Mirela-Diana Ilie

Antoine Tabarin

Alexandre Vasiljevic

Jean-François Bonneville

Lucile Moreau-Grangé

Franck Schillo

Brigitte Delemer

Anne Barlier

Dominique Figarella-Branger

Ségolène Bisot-Locard

Alexandre Santos
email: alexandre.santos@novartis.com.

Philippe Chanson

Gérald Raverot

Predictive Factors of Somatostatin Receptor Ligand Response in Acromegaly-A Prospective Study

Keywords: acromegaly, octreotide, somatostatin receptor, growth hormone (GH), insulin growth factor-I (IGF-I) IHC, immunohistochemistry, IRS, immunoreactive score, LAR, long-acting release, M, month, MRI, magnetic resonance imaging, SRL, somatostatin receptor ligand, SST, somatostatin, T2WSI, T2-weighted magnetic resonance imaging signal intensity

Context: Somatostatin receptor ligands (SRLs) are the cornerstone medical treatments for acromegaly; however, many patients remain unresponsive to SRLs. Well-established predictive markers of response are needed. Objective: We aimed to explore the relationship between responsiveness to SRLs relative to somatostatin (SST)2A and 5 receptor expression, adenoma granularity, and T2-weighted magnetic resonance imaging (MRI) signal intensity (T2WSI).

Methods:

We conducted a multicentric, prospective, observational cohort study, in France. Forty-nine naïve patients (ie, patients without preoperative SRL treatment) with active acromegaly following surgery were treated with octreotide (group 1; n = 47), or pasireotide if uncontrolled under first-generation SRLs (group 2; n = 9). Data were collected at baseline and months 3 and 6. Biochemical measurements, immunohistochemistry studies, and MRI readings were centralized.

Results:

In group 1, IGF-I decrease from baseline to month 6 positively correlated with SST2A immunoreactive score (IRS), P = 0.01. Densely granulated/intermediate adenomas had a greater IGF-I and GH decrease under octreotide compared with sparsely granulated adenomas (P = 0.02 and P = 0.006, respectively), and expressed greater levels of SST2A (P < 0.001), coupled with lower levels of SST5 (P = 0.004). T2WSI changed between preoperative MRI and month 6 MRI in one-half of the patients. Finally, SST5 IRS was higher in preoperative hyperintense compared with preoperative hypointense adenomas (P = 0.04), and most sparsely granulated and most hyperintense adenomas expressed high SST5 levels.

Conclusion:

We prospectively confirm that SST2A and adenoma granularity are good predictors of response to octreotide. We propose the IRS for scoring system harmonization. MRI sequences must be optimized to be able to use the T2WSI as a predictor of treatment response.

thirds of patients [START_REF] Dabrh | Surgical interventions and medical treatments in treatment-naïve patients with acromegaly: systematic review and meta-analysis[END_REF][START_REF] Chen | Microsurgical versus endoscopic transsphenoidal resection for acromegaly: a systematic review of outcomes and complications[END_REF]. In case of persistent disease following surgery, the recommended first-line medical therapy consists of first-generation long-acting release (LAR) somatostatin receptor ligands (SRLs) (ie, octreotide or lanreotide) [START_REF] Melmed | A consensus statement on acromegaly therapeutic outcomes[END_REF]. These molecules target preferentially somatostatin (SST) receptor subtype 2 [START_REF] Hofland | Pituitary tumours: the SST/D2 receptors as molecular targets[END_REF][START_REF] Bruns | SOM230: A novel somatostatin peptidomimetic with broad somatotropin release inhibiting factor (SRIF) receptor binding and a unique antisecretory profile[END_REF] and allow normalization of GH and IGF-I in approximately 45% of cases [START_REF] Van Der Lely | Pegvisomant and not somatostatin receptor ligands (SRLs) is first-line medical therapy for acromegaly[END_REF]. Second-line medical therapies include pasireotide, a second-generation SRL that targets SST1, SST2, SST3, and especially the SST5 receptor [START_REF] Bruns | SOM230: A novel somatostatin peptidomimetic with broad somatotropin release inhibiting factor (SRIF) receptor binding and a unique antisecretory profile[END_REF][START_REF] Van Der Hoek | Preclinical and clinical experiences with the role of somatostatin receptors in the treatment of pituitary adenomas[END_REF]. Pasireotide LAR was more effective than octreotide LAR in achieving biochemical control in patients with medically naïve acromegaly [START_REF] Colao | Pasireotide versus octreotide in acromegaly: a head-to-head superiority study[END_REF] and led to normalization of GH and IGF-I in 20% of patients who were inadequately controlled using first-generation SRLs [START_REF] Gadelha | Pasireotide versus continued treatment with octreotide or lanreotide in patients with inadequately controlled acromegaly (PAOLA): a randomised, phase 3 trial[END_REF]. Impaired glucose metabolism was also more frequent with pasireotide LAR [START_REF] Colao | Pasireotide versus octreotide in acromegaly: a head-to-head superiority study[END_REF][START_REF] Gadelha | Pasireotide versus continued treatment with octreotide or lanreotide in patients with inadequately controlled acromegaly (PAOLA): a randomised, phase 3 trial[END_REF].

Among the factors to consider when choosing a medical treatment, the 2018 expert consensus included predictive factors of treatment response, notably adenoma granularity and T2-weighted magnetic resonance imaging (MRI) signal intensity (T2WSI) (4); both densely granulated adenomas [START_REF] Melmed | A consensus statement on acromegaly therapeutic outcomes[END_REF][START_REF] Cuevas-Ramos | A structural and functional acromegaly classification[END_REF][START_REF] Brzana | Growth hormone granulation pattern and somatostatin receptor subtype 2A correlate with postoperative somatostatin receptor ligand response in acromegaly: a large single center experience[END_REF][START_REF] Kiseljak-Vassiliades | Differential somatostatin receptor (SSTR) 1-5 expression and downstream effectors in histologic subtypes of growth hormone pituitary tumors[END_REF] and hypointense adenomas [START_REF] Melmed | A consensus statement on acromegaly therapeutic outcomes[END_REF][START_REF] Potorac | T2-weighted MRI signal predicts hormone and tumor responses to somatostatin analogs in acromegaly[END_REF][START_REF] Puig-Domingo | Magnetic resonance imaging as a predictor of response to somatostatin analogs in acromegaly after surgical failure[END_REF][START_REF] Nista | Clinical and radiological predictors of biochemical response to first-line treatment with somatostatin receptor ligands in acromegaly: a real-life perspective[END_REF] were shown to exhibit a greater response to first-generation SRLs. However, evidence regarding the predictive role of SST2A and SST5 receptor expression via immunohistochemistry (IHC) was considered of very low quality, lacking scoring harmonization and prospective validation [START_REF] Melmed | A consensus statement on acromegaly therapeutic outcomes[END_REF]. Indeed, although SST2A receptor expression was consistently found to positively correlate or to be associated with the biochemical response to firstgeneration SRLs [START_REF] Brzana | Growth hormone granulation pattern and somatostatin receptor subtype 2A correlate with postoperative somatostatin receptor ligand response in acromegaly: a large single center experience[END_REF][START_REF] Plöckinger | Selective loss of somatostatin receptor 2 in octreotide-resistant growth hormone-secreting adenomas[END_REF][START_REF] Casar-Borota | Expression of SSTR2a, but not of SSTRs 1, 3, or 5 in somatotroph adenomas assessed by monoclonal antibodies was reduced by octreotide and correlated with the acute and long-term effects of octreotide[END_REF][START_REF] Gatto | Immunoreactivity score using an anti-sst2A receptor monoclonal antibody strongly predicts the biochemical response to adjuvant treatment with somatostatin analogs in acromegaly[END_REF][START_REF] Fougner | The clinical response to somatostatin analogues in acromegaly correlates to the somatostatin receptor subtype 2a protein expression of the adenoma[END_REF][START_REF] Ferone | Correlation of in vitro and in vivo somatotropic adenoma responsiveness to somatostatin analogs and dopamine agonists with immunohistochemical evaluation of somatostatin and dopamine receptors and electron microscopy[END_REF][START_REF] Iacovazzo | Factors predicting pasireotide responsiveness in somatotroph pituitary adenomas resistant to firstgeneration somatostatin analogues: an immunohistochemical study[END_REF][START_REF] Wildemberg | Low somatostatin receptor subtype 2, but not dopamine receptor subtype 2 expression predicts the lack of biochemical response of somatotropinomas to treatment with somatostatin analogs[END_REF], the studies analyzing the predictive role of SST2A and SST5 receptor expression are all retrospective, reported differently the level of expression of SST receptors, and some included patients who received preoperative SRL treatment, which might modify SST2A receptor expression [START_REF] Plöckinger | Selective loss of somatostatin receptor 2 in octreotide-resistant growth hormone-secreting adenomas[END_REF][START_REF] Casar-Borota | Expression of SSTR2a, but not of SSTRs 1, 3, or 5 in somatotroph adenomas assessed by monoclonal antibodies was reduced by octreotide and correlated with the acute and long-term effects of octreotide[END_REF][START_REF] Coelho | Clinical significance of filamin A in patients with acromegaly and its association with somatostatin and dopamine receptor profiles[END_REF]. Studies assessing the biochemical response to pasireotide relative to SST2A and SST5 receptor expression are scarce and yielded contradictory results [START_REF] Iacovazzo | Factors predicting pasireotide responsiveness in somatotroph pituitary adenomas resistant to firstgeneration somatostatin analogues: an immunohistochemical study[END_REF][START_REF] Muhammad | Pasireotide responsiveness in acromegaly is mainly driven by somatostatin receptor subtype 2 expression[END_REF].

Here, we aimed to prospectively assess the relationship between response to first-and second-generation SRLs and SST2A and SST5 receptor expression, adenoma granularity, and T2WSI, in exclusively naïve patients (ie, patients without preoperative SRL treatment). Furthermore, we explored the relationship between SST receptor expression and adenoma granularity, SST receptor expression and T2WSI, and between adenoma granularity and T2WSI.

Methods

Patients and Study Design

This is a longitudinal, observational, prospective cohort study conducted from 2017 to 2020 in 14 clinical centers in France. The study included adult acromegaly patients who were inadequately controlled by surgery and who were to be initiated on either octreotide LAR or pasireotide LAR for the first time. The patients were treated according to each center's protocol.

Group 1 included patients who were to receive octreotide LAR IM (starting dose, 10-30 mg/28 days). Group 2 included patients who were unresponsive to a first-generation SRL administered for at least 3 months but not more than 12 months and were to receive pasireotide LAR IM (starting dose 40 mg/ 28 days). Group 1 was allowed to join group 2 in case octreotide LAR was switched to pasireotide LAR before the end of the inclusion date in group 2 (in this case, these patients were first analyzed as being part of group 1, and then of group 2). The study required an assessment at baseline (M0), month 3 (M3), and 6 (M6). The study accepted an offset of the visit dates by at most 1 month.

The study was performed in line with the principles of the Declaration of Helsinki and its later amendments, it was approved by the bioethics committee "Comité de protection des personnes Sud-Méditerranée II" (no. 2017-A00938-45), and registered with "Commission nationale de l'informatique et des libertés" no. 2002304. Informed consent was obtained from all patients before enrollment.

Biochemical Assessment

Laboratory parameters (GH, IGF-I) were measured centrally at M0, M3 and M6, using Immulite Siemens Healthcare Diagnostics Products (Llanberis, UK) chemiluminescent immunometric assays (Siemens catalog #L2KGF2, RRID:AB_2756880 for IGF-I, and Siemens catalog #L2KGRH2, RRID: AB_2811291 for GH). Note that "RRID:AB_2756880" is hyperlinked to https://scicrunch.org/resolver/AB_2756880 and "RRID: AB_ 2811291" is hyperlinked to https://scicrunch.org/resolver/ AB_2811291. For GH, the intra-and interassays coefficients of variation were respectively 3.5% and 6.5% for 2.6 ng/mL, and 2.9% and 4.2% for 7.5 ng/mL, expressed relative to World Health Organization Second International Standard 98/574. For IGF-I, the intra-and interassays coefficients of variation were respectively 6.3% and 7.6% for 56 ng/mL, and 3.1% and 3.9% for 200 ng/mL, expressed relative to World Health Organization First International Standard 02/2547. The detection limits were 0.01 ng/mL for GH and 3 ng/mL for IGF-I. Normal levels of IGF-I were sex-and age-adjusted [START_REF] Sabbah | Reference values for IGF-I serum concentration in an adult population: use of the VARIETE cohort for two new immunoassays[END_REF].

Results are presented as percent reduction of GH and IGF-I between M0 and M6. M6 GH measurements were replaced with M3 GH measurements if the treatment was stopped before M6. Acromegaly control was defined as both normalized IGF-I and random GH < 1 µg/L; partial response was defined as a > 20% decrease in IGF-I, and resistance was defined as a ≤20% decrease in IGF-I.

Magnetic Resonance Imaging

Invasion of the adenoma into the cavernous sinus (revised Knosp classification (29)), T2WSI, and change in signal from the preoperative MRI to M6 were evaluated centrally, in a blinded manner, by 2 pituitary imaging experts. T2WSI was evaluated qualitatively as described by Potorac et al [START_REF] Potorac | Pituitary MRI characteristics in 297 acromegaly patients based on T2-weighted sequences[END_REF], and classified as hypointense, isointense, hyperintense, and heterogeneous/not interpretable (Fig. 1). In case of discordance between the 2 experts, the evaluation was jointly repeated to reach consensus.

Histopathology and Immunohistochemistry

Automated IHC staining to determine SST2A and SST5 receptor expression, and adenoma granularity, was performed centrally by a single pathologist (at once for all patients), and subsequently assessed centrally by 2 expert assessors. In case of discordance between the 2 experts, the staining was jointly reviewed to reach consensus. Antibodies used for IHC were as follows: SST2A (1:4000, rabbit monoclonal, clone UMB-1, Abcam, Cambridge, UK, Abcam catalog #ab134152, RRID:AB_2737601), SST5 (1:500, rabbit monoclonal, clone UMB-4, Abcam, Cambridge, UK, Abcam catalog #ab109495, RRID:AB_10859946), and cytokeratin 18 (1:50, mouse monoclonal, clone DC10, Dako, Glostrup, Denmark, Agilent catalog #M7010, RRID: AB_2133299). Note that "RRID:AB_2737601" is hyperlinked to https://scicrunch.org/resolver/AB_2737601, "RRID:AB_ 10859946" is hyperlinked to https://scicrunch.org/resolver/ AB_10859946, and "RRID:AB_2133299" is hyperlinked to https://scicrunch.org/resolver/AB_2133299. The IHC protocol was the same as previously published [START_REF] Ilie | Gonadotroph tumors show subtype differences that might have implications for therapy[END_REF].

SST2A and SST5 receptor expression was assessed using the immunoreactive score (IRS), as previously published [START_REF] Ilie | Gonadotroph tumors show subtype differences that might have implications for therapy[END_REF][START_REF] Delgrange | Expression of estrogen receptor alpha is associated with prolactin pituitary tumor prognosis and supports the sex-related difference in tumor growth[END_REF]. Briefly, the IRS (0-12) is the product between the percentage of stained cells (0-4: 0 = 0% stained cells, 1 ≤ 10%, 2 = 10%-50%, 3 = 51%-80%, 4 ≥ 80%) and the staining intensity (0-3: 0 = absent, 1 = weak, 2 = moderate, 3 = strong). According to cytokeratin 18 IHC distribution pattern, adenomas were categorized into densely granulated (perinuclear pattern), intermediate (transitional pattern), and sparsely granulated adenomas (dot-pattern, fibrous body) [START_REF] Obari | Clinicopathological features of growth hormone-producing pituitary adenomas: difference among various types defined by cytokeratin distribution pattern including a transitional form[END_REF]. The first 2 categories were merged into 1 category for analysis, as previously done in the literature [START_REF] Brzana | Growth hormone granulation pattern and somatostatin receptor subtype 2A correlate with postoperative somatostatin receptor ligand response in acromegaly: a large single center experience[END_REF][START_REF] Kiseljak-Vassiliades | Differential somatostatin receptor (SSTR) 1-5 expression and downstream effectors in histologic subtypes of growth hormone pituitary tumors[END_REF].

Statistical Analysis

All analyses related to treatment response were conducted separately in groups 1 and 2, whereas analyses looking at baseline characteristics were performed on all unique patients for which adenoma tissue was exploitable. Spearman correlation, Mann-Whitney, Kruskal-Wallis, exact Fisher test, and receiver operator characteristic curve analysis, were applied, as appropriate. The significance level was set at 5% for all tests. Statistical analysis and graphs were made using SAS v9.4 software.

Results

Patients and Tumors Characteristics

A total of 49 patients were recruited: group 1 included 47 patients and group 2 included 9 patients (Fig. 2), 7 of which switched from group 1. Adenoma tissue was not exploitable in 9 patients. The final study cohort consisted of 39 patients (group 1) and 8 patients (group 2); there was a total of 41 unique patients for which adenoma tissue was exploitable. One patient from group 1 did not finish the study because of adverse events, and 2 patients (1 from each group) did not finish the study because of insufficient efficacy of the treatment (Fig. 2). Table 1 provides details of the patients and tumors characteristics per group.

Treatment Efficacy

Twelve patients (30.8%) had a dose change in group 1: 11 because of insufficient control (all 11 of these cases received an initial dose of 20 mg/28 days and were switched to 30 mg/ 28 days after 2 injections in 1 case, after 3 injections in 2 cases, after 4 injections in 7 cases, and after 5 injections in 1 case, respectively), and 1 because of an adverse event (this patient received an initial dose of 20 mg/28 days and was switched to 10 mg/28 days after 4 injections). Two patients (25%) had a dose change in group 2 because of insufficient control: both patients received an initial dose of 40 mg/28 days and were switched to 60 mg/28 days after 4 injections. The maximum dose was 30 mg in group 1 and 60 mg in group 2. The median final dose was 30 mg/days in group 1 (73% of patients had a final dose of 30 mg/28 days in group 1) and 40 mg/28 days in group 2 (71.4% of patients had a final dose of 40 mg/28 days in group 2).

At M6, no patient achieved biochemical control. In group 1, partial response was observed in 10/35 (28.6%) patients, and resistance was observed in 25/35 (71.4%) patients. In group 2, 3/6 (50%) patients had a partial response, and 3/6 (50%) patients were resistant.

The median percent reduction of IGF-I from M0 to M6 was 19.7% (range, -107.6 to 66.8) in group 1 and 32.7% (range, 2.5-65.7) in group 2, whereas the median percent reduction of GH from M0 to M6 was 52.9% (range, -1154.5 to 93.2) in group 1 and 67.5% (range, 33.6-83.3) in group 2. Given that group 2 was formed by only 6 patients at M6, we will only report the analyses exploring the relationships between response and potential predictive factors of response for this group in Table 2.

Octreotide Efficacy Relative to SST2A and SST5 Receptor Expression

In group 1, there was a positive, moderate correlation between SST2A IRS and the percent reduction of IGF-I from M0 to M6 (Fig. 3A). No statistically significant correlation between SST2A IRS and the percent reduction of GH from M0 to M6 was found (rho = 0.25, P = 0.12). Moreover, SST5 IRS did not correlate with the percent reduction of IGF-I from M0 to M6 (Fig. 3B), or with that of GH (rho = -0.16, P = 0.34). Similar to the SST2A IRS analyses, there was also a positive, moderate correlation between SST2A IRS/SST5 IRS ratio and the percent reduction of IGF-I from M0 to M6 (Fig. 3C); no statistically significant correlation between SST2A IRS/SST5 IRS ratio and the percent reduction of GH from M0 to M6 was found (rho = 0.32, P = 0.06).

Interestingly, when analyzing together all 41 unique patients, no correlation was found between SST2A IRS and SST5 IRS (rho = 0.03, P = 0.84).

Regarding the best SST2A IRS cutoff discriminating between resistant and partial responders to octreotide LAR, in our cohort, the received operator characteristic curve analysis identified a SST2A IRS ≥ 7 to be the best predictor of response, with 81.25% sensitivity, 58.82% specificity, a positive predictive value of 65%, a negative predictive value of 76.92%, and an accuracy of 69.69% (Fig. 3D).

Octreotide Efficacy Relative to Adenoma Granularity

The densely granulated/intermediate group had a higher percent reduction from M0 to M6 of both IGF-I and GH, compared with the sparsely granulated group, with a median percent reduction of IGF-I of 44.8 vs 14.5, P = 0.02, and a median percent reduction of GH of 69 vs 5.9, P = 0.006 (Fig. 4).

Interestingly, when analyzing together all 41 unique patients, the densely granulated/intermediate group had higher SST2A IRS, higher SST2A IRS/SST5 IRS ratio, and lower SST5 IRS than the sparsely granulated group, P < 0.001, P < 0.0001, and P = 0.004, respectively (Figs. 5 and6). Moreover, 76% of sparsely granulated adenomas expressed high levels of SST5 (ie, IRS ≥ 9).

Octreotide Efficacy Relative to T2-weighted MRI Signal Intensity

Neither the percent reduction of IGF-I from M0 to M6, nor that of GH, were statistically different between hypointense (median = 16.4; range, -9.1 to 66. From interpretable MRI scans, T2WSI changed between the preoperative MRI and the M6-MRI for 6 of 13 (46.1%) patients. This change was either from isointense to hyperintense (3 cases) or to hypointense (1 case), or from hyperintense to isointense (1 case), or from hypointense to hyperintense (1 case).

When analyzing all unique patients together, SST5 IRS was statistically different between hyperintense, isointense, and hypointense adenomas, P = 0.01, as evaluated on the preoperative MRIs, with significantly higher SST5 IRS in hyperintense than in hypointense adenomas, P = 0.04 (Fig. 7A).

Moreover, 75% of hyperintense adenomas expressed high levels of SST5 (ie, IRS = 12). Neither SST2A IRS nor SST2A IRS/SST5 IRS ratio was statistically different between hypointense, isointense, and hyperintense adenomas (Fig. 7B andC). The granulation pattern was not statistically different between the hypointense, isointense, and hyperintense adenomas, either (P = 0.15); however, hypointense adenomas tended to be associated with a densely granulated/intermediate pattern with an odds ratio of 3:1 (Table 3).

Discussion

Here, we conducted the first prospective, longitudinal study to evaluate first-and second-generation SRLs efficacy relative to SST2A and SST5 receptor expression, adenoma granularity, and T2WSI. The strength and originality of our study lies in its prospective, longitudinal design, allowing a detailed description of the enrolled patients, whereas its observational design reflects more closely real life. Furthermore, the exclusive inclusion of treatment-naïve patients averted potential modification of SST receptor expression and of T2WSI by the administration of preoperative SRLs. In addition, centralized biochemical measurements, IHC, and MRI readings add further validity to the outcomes.

SST2A and SST5 receptors are the most frequently expressed SST receptor subtypes in GH-secreting adenomas [START_REF] Chinezu | Expression of somatostatin receptors, SSTR2A and SSTR5, in 108 endocrine pituitary tumors using immunohistochemical detection with new specific monoclonal antibodies[END_REF][START_REF] Cuevas-Ramos | Somatostatin receptor ligands and resistance to treatment in pituitary adenomas[END_REF], but the level of expression varies from 1 individual to another [START_REF] Chinezu | Expression of somatostatin receptors, SSTR2A and SSTR5, in 108 endocrine pituitary tumors using immunohistochemical detection with new specific monoclonal antibodies[END_REF]. Several retrospective studies, mainly conducted with first-generation SRLs, have sought to assess the relationship between the level of expression of SST2A and SST5 receptors and the biochemical response. The studies repeatedly showed that biochemical response to first-generation SRLs positively correlated or was associated with SST2A receptor expression, regardless of the way the level of receptor expression was reported or of the definition used for biochemical response [START_REF] Brzana | Growth hormone granulation pattern and somatostatin receptor subtype 2A correlate with postoperative somatostatin receptor ligand response in acromegaly: a large single center experience[END_REF][START_REF] Plöckinger | Selective loss of somatostatin receptor 2 in octreotide-resistant growth hormone-secreting adenomas[END_REF][START_REF] Casar-Borota | Expression of SSTR2a, but not of SSTRs 1, 3, or 5 in somatotroph adenomas assessed by monoclonal antibodies was reduced by octreotide and correlated with the acute and long-term effects of octreotide[END_REF][START_REF] Gatto | Immunoreactivity score using an anti-sst2A receptor monoclonal antibody strongly predicts the biochemical response to adjuvant treatment with somatostatin analogs in acromegaly[END_REF][START_REF] Fougner | The clinical response to somatostatin analogues in acromegaly correlates to the somatostatin receptor subtype 2a protein expression of the adenoma[END_REF][START_REF] Ferone | Correlation of in vitro and in vivo somatotropic adenoma responsiveness to somatostatin analogs and dopamine agonists with immunohistochemical evaluation of somatostatin and dopamine receptors and electron microscopy[END_REF][START_REF] Iacovazzo | Factors predicting pasireotide responsiveness in somatotroph pituitary adenomas resistant to firstgeneration somatostatin analogues: an immunohistochemical study[END_REF][START_REF] Wildemberg | Low somatostatin receptor subtype 2, but not dopamine receptor subtype 2 expression predicts the lack of biochemical response of somatotropinomas to treatment with somatostatin analogs[END_REF][START_REF] Soukup | Predictive and prognostic significance of tumour subtype, SSTR1-5 and e-cadherin expression in a well-defined cohort of patients with acromegaly[END_REF][START_REF] Puig-Domingo | Molecular profiling for acromegaly treatment: a validation study[END_REF][START_REF] Wildemberg | Machine learning-based prediction model for treatment of acromegaly with first-generation somatostatin receptor ligands[END_REF]. However, no statistically significant associations or correlations between SST5 receptor expression and the response to first-generation SRLs were found [START_REF] Plöckinger | Selective loss of somatostatin receptor 2 in octreotide-resistant growth hormone-secreting adenomas[END_REF][START_REF] Casar-Borota | Expression of SSTR2a, but not of SSTRs 1, 3, or 5 in somatotroph adenomas assessed by monoclonal antibodies was reduced by octreotide and correlated with the acute and long-term effects of octreotide[END_REF][START_REF] Iacovazzo | Factors predicting pasireotide responsiveness in somatotroph pituitary adenomas resistant to firstgeneration somatostatin analogues: an immunohistochemical study[END_REF][START_REF] Wildemberg | Machine learning-based prediction model for treatment of acromegaly with first-generation somatostatin receptor ligands[END_REF]. The results regarding the biochemical response to pasireotide LAR are conflicting, with 1 study showing that the response to pasireotide LAR in patients resistant to first-generation SRLs was positively associated with SST5 receptor expression, but not significantly associated with SST2A receptor expression [START_REF] Iacovazzo | Factors predicting pasireotide responsiveness in somatotroph pituitary adenomas resistant to firstgeneration somatostatin analogues: an immunohistochemical study[END_REF], whereas another study has reported a positive correlation with SST2A receptor expression in patients partially responsive to first-generation SRLs, but not with SST5 receptor expression [START_REF] Muhammad | Pasireotide responsiveness in acromegaly is mainly driven by somatostatin receptor subtype 2 expression[END_REF]. However, the sample sizes of both studies were limited (ie, 14 [START_REF] Muhammad | Pasireotide responsiveness in acromegaly is mainly driven by somatostatin receptor subtype 2 expression[END_REF] and 11 patients ( 24)).

Regarding SST2A receptor expression in our study, we observed a positive, moderate correlation between SST2A IRS and the percent decrease of IGF-I in group 1. The correlation with the percent decrease of GH was not statistically significant. Consistently with the literature and expected given the low affinity of octreotide for SST5, we did not find any correlations between SST5 receptor expression and the percent decrease of IGF-I, or of GH. Moreover, the SST2A IRS/SST5 IRS ratio, similar to SST2A IRS, positively and moderately correlated with the percent decrease of IGF-I in group 1, reinforcing a role for SST2A and the absence of a role for SST5. Our prospective study confirms, therefore, that SST2A receptor expression is a good predictor of biochemical response to first-generation SRLs, whereas SST5 receptor expression is not. It appears reasonable that future consensus/guidelines include SST2 as an established predictive factor of response to octreotide. However, to introduce it in the clinical practice, harmonization of SST expression grading will be needed. So far, the IRS was used in 3 other studies analyzing the relationship between SST2 receptor expression and response to octreotide [START_REF] Casar-Borota | Expression of SSTR2a, but not of SSTRs 1, 3, or 5 in somatotroph adenomas assessed by monoclonal antibodies was reduced by octreotide and correlated with the acute and long-term effects of octreotide[END_REF][START_REF] Gatto | Immunoreactivity score using an anti-sst2A receptor monoclonal antibody strongly predicts the biochemical response to adjuvant treatment with somatostatin analogs in acromegaly[END_REF][START_REF] Wildemberg | Machine learning-based prediction model for treatment of acromegaly with first-generation somatostatin receptor ligands[END_REF], in addition to ours (all the other scoring systems were used even less frequently [START_REF] Brzana | Growth hormone granulation pattern and somatostatin receptor subtype 2A correlate with postoperative somatostatin receptor ligand response in acromegaly: a large single center experience[END_REF][START_REF] Plöckinger | Selective loss of somatostatin receptor 2 in octreotide-resistant growth hormone-secreting adenomas[END_REF][START_REF] Fougner | The clinical response to somatostatin analogues in acromegaly correlates to the somatostatin receptor subtype 2a protein expression of the adenoma[END_REF][START_REF] Ferone | Correlation of in vitro and in vivo somatotropic adenoma responsiveness to somatostatin analogs and dopamine agonists with immunohistochemical evaluation of somatostatin and dopamine receptors and electron microscopy[END_REF][START_REF] Iacovazzo | Factors predicting pasireotide responsiveness in somatotroph pituitary adenomas resistant to firstgeneration somatostatin analogues: an immunohistochemical study[END_REF][START_REF] Wildemberg | Low somatostatin receptor subtype 2, but not dopamine receptor subtype 2 expression predicts the lack of biochemical response of somatotropinomas to treatment with somatostatin analogs[END_REF][START_REF] Puig-Domingo | Molecular profiling for acromegaly treatment: a validation study[END_REF]). Given that the IRS is fairly simple to use and also used in several pituitary adenoma subtypes [START_REF] Ilie | Gonadotroph tumors show subtype differences that might have implications for therapy[END_REF][START_REF] Øystese | Estrogen receptor α, a sex-dependent predictor of aggressiveness in nonfunctioning pituitary adenomas: SSTR and sex hormone receptor distribution in NFPA[END_REF], we propose keeping IRS as the preferred SST scoring system for acromegaly.

Regarding the best SST2A IRS cutoff, in our cohort, an SST2A IRS ≥ 7 best discriminated between resistant and partial responders to octreotide LAR. However, this cutoff should be cautiously interpreted given that we did not see any complete response in our cohort and that we defined a partial response as a ≤ 20% decrease in IGF-I. Indeed, that we did not see any complete response (and that, generally speaking, the response to octreotide was lesser than expected) is a limitation of our study and might be explained by the fact that both the starting dose and the uptitration were performed according to each center's protocol, coupled with a relatively short duration of the study (6 months). Therefore, the final dose might have been insufficient in some patients and/or the duration of treatment on the optimal dose too short.

Regarding adenoma granularity, based on IHC, GH-secreting adenomas can be classified as densely granulated, sparsely granulated, or intermediate [START_REF] Obari | Clinicopathological features of growth hormone-producing pituitary adenomas: difference among various types defined by cytokeratin distribution pattern including a transitional form[END_REF]. The intermediate group is generally considered to behave similarly to the densely granulated one [START_REF] Brzana | Growth hormone granulation pattern and somatostatin receptor subtype 2A correlate with postoperative somatostatin receptor ligand response in acromegaly: a large single center experience[END_REF][START_REF] Kiseljak-Vassiliades | Differential somatostatin receptor (SSTR) 1-5 expression and downstream effectors in histologic subtypes of growth hormone pituitary tumors[END_REF][START_REF] Obari | Clinicopathological features of growth hormone-producing pituitary adenomas: difference among various types defined by cytokeratin distribution pattern including a transitional form[END_REF]; therefore, studies usually considered these 2 subtypes together [START_REF] Brzana | Growth hormone granulation pattern and somatostatin receptor subtype 2A correlate with postoperative somatostatin receptor ligand response in acromegaly: a large single center experience[END_REF][START_REF] Kiseljak-Vassiliades | Differential somatostatin receptor (SSTR) 1-5 expression and downstream effectors in histologic subtypes of growth hormone pituitary tumors[END_REF]. Densely granulated/intermediate adenomas were shown to be more responsive to first-generation SRLs compared with sparsely granulated adenomas, and in addition, to express the SST2A receptor more frequently and to a greater extent [START_REF] Cuevas-Ramos | A structural and functional acromegaly classification[END_REF][START_REF] Brzana | Growth hormone granulation pattern and somatostatin receptor subtype 2A correlate with postoperative somatostatin receptor ligand response in acromegaly: a large single center experience[END_REF][START_REF] Kiseljak-Vassiliades | Differential somatostatin receptor (SSTR) 1-5 expression and downstream effectors in histologic subtypes of growth hormone pituitary tumors[END_REF][START_REF] Fougner | Adenoma granulation pattern correlates with clinical variables and effect of somatostatin analogue treatment in a large series of patients with acromegaly: granulation in somatotroph adenomas[END_REF]. Indeed, the better responsiveness of densely granulated adenomas might be due in part to this higher expression of SST2A receptor [START_REF] Brzana | Growth hormone granulation pattern and somatostatin receptor subtype 2A correlate with postoperative somatostatin receptor ligand response in acromegaly: a large single center experience[END_REF][START_REF] Kiseljak-Vassiliades | Differential somatostatin receptor (SSTR) 1-5 expression and downstream effectors in histologic subtypes of growth hormone pituitary tumors[END_REF]. Regarding the expression of SST5 receptor relative to the granulation pattern, the literature is contradictory, with certain authors demonstrating a similar expression of SST5 between densely granulated and sparsely granulated adenomas [START_REF] Chinezu | Expression of somatostatin receptors, SSTR2A and SSTR5, in 108 endocrine pituitary tumors using immunohistochemical detection with new specific monoclonal antibodies[END_REF], whereas others demonstrating SST5 to be expressed only in sparsely granulated adenomas, but not in densely granulated adenomas [START_REF] Mayr | Molecular and functional properties of densely and sparsely granulated GH-producing pituitary adenomas[END_REF].

In our cohort, densely granulated/intermediate adenomas were also more responsive to octreotide than sparsely granulated adenomas and expressed higher levels of SST2A; moreover, densely granulated/intermediate adenomas also had higher SST2A IRS/SST5 IRS ratio and expressed lower levels of SST5 receptor than sparsely granulated adenomas. In addition, the vast majority of sparsely granulated adenomas expressed high levels of SST5. Our group 2 was too small to allow a firm conclusion, but these sparsely granulated adenomas high in SST5 receptor might be good responders to pasireotide LAR; of note, a better response to pasireotide LAR of sparsely granulated adenomas compared with densely granulated ones have previously been noted [START_REF] Iacovazzo | Factors predicting pasireotide responsiveness in somatotroph pituitary adenomas resistant to firstgeneration somatostatin analogues: an immunohistochemical study[END_REF]. In addition, given that sparsely granulated adenomas respond less to first-generation SRLs, they may even represent a group in which pasireotide LAR would be worth trying as first-line SRL. Further studies should test whether this is the case. Based on the T2WSI, GH-secreting adenomas can be classified as hypointense, isointense, or hyperintense. The hypointense character was associated with a better response to SRLs (mainly first-generation SRLs) both when diagnostic/ baseline MRIs were used as reference for primary SRL treatment [START_REF] Potorac | T2-weighted MRI signal predicts hormone and tumor responses to somatostatin analogs in acromegaly[END_REF][START_REF] Nista | Clinical and radiological predictors of biochemical response to first-line treatment with somatostatin receptor ligands in acromegaly: a real-life perspective[END_REF][START_REF] Heck | Intensity of pituitary adenoma on T2-weighted magnetic resonance imaging predicts the response to octreotide treatment in newly diagnosed acromegaly: intensity of somatotroph adenoma on T2-weighted MRI[END_REF][START_REF] Bonneville | MRI T2 signal intensity and tumor response in patients with GH-secreting pituitary macroadenoma: PRIMARYS post hoc analysis[END_REF] and when postoperative MRIs were used as reference for adjuvant SRL treatment [START_REF] Puig-Domingo | Magnetic resonance imaging as a predictor of response to somatostatin analogs in acromegaly after surgical failure[END_REF]. Conversely, a better hormonal response to pasireotide LAR administered as monotherapy or in combination with pegvisomant to patients resistant to first-generation SRL was found to be associated with hyperintense adenomas and to weakly correlate with higher baseline T2WSI (baseline here meaning when pasireotide LAR was started or maximum 1 year before) [START_REF] Coopmans | Potential antitumour activity of pasireotide on pituitary tumours in acromegaly[END_REF][START_REF] Coopmans | T2-signal intensity, SSTR expression, and somatostatin analogs efficacy predict response to pasireotide in acromegaly[END_REF].

In our group 1, although not statistically significant, we also found that the median percent decrease of GH was higher in hypointense than in isointense and hyperintense adenomas. However, the median percent decrease of IGF-I did not follow the same trend. This observation is different from the results of the only other study assessing the T2WSI as a predictor of response to adjuvant first-generation SRL treatment, which found at M6 a complete response in 71% of the hypointense tumors compared with in only 20% of the hyperintense tumors [START_REF] Puig-Domingo | Magnetic resonance imaging as a predictor of response to somatostatin analogs in acromegaly after surgical failure[END_REF]. This incongruence might be explained by the many differences between the 2 studies, including different definitions of T2WSI. That different definitions might be used to define T2WSI is important given that a recent study showed very different proportions of each signal category when using 3 different ways of defining T2WSI (the percentage of the hypointense category varied from as low as 20% to as high as 59%) [START_REF] Bonneville | MRI T2 signal intensity and tumor response in patients with GH-secreting pituitary macroadenoma: PRIMARYS post hoc analysis[END_REF]. We also used preoperative MRIs compared with postoperative MRIs in the aforementioned study; however, as noted in their study, no difference in T2WSI was seen between the preoperative and the postoperative MRIs [START_REF] Puig-Domingo | Magnetic resonance imaging as a predictor of response to somatostatin analogs in acromegaly after surgical failure[END_REF].

The same study also found that during lanreotide Autogel treatment, 20% of adenomas shifted from 1 category of T2WSI to another [START_REF] Bonneville | MRI T2 signal intensity and tumor response in patients with GH-secreting pituitary macroadenoma: PRIMARYS post hoc analysis[END_REF], whereas other authors reported no change in T2WSI with first-generation SRLs [START_REF] Puig-Domingo | Magnetic resonance imaging as a predictor of response to somatostatin analogs in acromegaly after surgical failure[END_REF]. In our group 1, we also found that T2WSI shifted from 1 category to another between the preoperative MRI and the M6-MRI in about one-half of the patients for which the information was available. It is uncertain whether this change in T2WSI might be of biological significance, as recently proposed for the increased T2WSI seen in patients treated with pasireotide LAR [START_REF] Coopmans | Potential antitumour activity of pasireotide on pituitary tumours in acromegaly[END_REF][START_REF] Coopmans | T2-signal intensity, SSTR expression, and somatostatin analogs efficacy predict response to pasireotide in acromegaly[END_REF]. Nevertheless, it is important to be aware of this potential change in T2WSI, especially if one wants to predict the response to more than 1 treatment (for example, to predict the response to pasireotide after first-generation SRLs). Unfortunately, our group 2 was too small to draw any conclusions, but further studies should evaluate whether the diagnostic vs the pretreatment MRI is a better predictor of response to second-line SRLs.

Of note, hyperintense adenomas were associated with a sparsely granulated pattern, whereas hypointense adenomas were associated with a densely granulated/intermediate pattern [START_REF] Heck | Intensity of pituitary adenoma on T2-weighted magnetic resonance imaging predicts the response to octreotide treatment in newly diagnosed acromegaly: intensity of somatotroph adenoma on T2-weighted MRI[END_REF][START_REF] Heck | Quantitative analyses of T2-weighted MRI as a potential marker for response to somatostatin analogs in newly diagnosed acromegaly[END_REF][START_REF] Hagiwara | Comparison of growth hormone-producing and non-growth hormone-producing pituitary adenomas: imaging characteristics and pathologic correlation[END_REF]. We observed similar trends in our study. Isointense adenomas, however, were found to have an exclusively densely granulated/intermediate pattern in 1 study [START_REF] Heck | Intensity of pituitary adenoma on T2-weighted magnetic resonance imaging predicts the response to octreotide treatment in newly diagnosed acromegaly: intensity of somatotroph adenoma on T2-weighted MRI[END_REF][START_REF] Heck | Quantitative analyses of T2-weighted MRI as a potential marker for response to somatostatin analogs in newly diagnosed acromegaly[END_REF] and an exclusively sparsely granulated pattern in another study [START_REF] Hagiwara | Comparison of growth hormone-producing and non-growth hormone-producing pituitary adenomas: imaging characteristics and pathologic correlation[END_REF]. In our cohort, isointense adenomas were more frequently sparsely granulated. Remarkably, we found SST5 IRS to be higher in hyperintense than in hypointense adenomas. Moreover, most hyperintense adenomas presented high SST5 levels. To the best of our knowledge, we are the first to report this association between SST5 receptor expression and hyperintense adenomas. That hyperintense adenomas are more frequently sparsely granulated and with high SST5 expression, might partially explain their better response to pasireotide LAR noted in literature.

T2WSI may appear to be an interesting predictive factor of response particularly as it is noninvasive and can be used to predict response to primary SRL treatment. However, in real- life, the MRI quality, a heterogeneous signal, or an exclusively cystic adenoma may hinder its use as a predictive factor in some cases. In our cohort, of 41 unique patients, as many as 13 patients (31.7%) had missing, uninterpretable, or heterogeneous MRIs. Others noted important numbers of heterogeneous or uninterpretable MRIs, as well, with 1 study noting that the T2WSI of 24 of 144 (16.7%) MRIs was heterogeneous [START_REF] Potorac | T2-weighted MRI signal predicts hormone and tumor responses to somatostatin analogs in acromegaly[END_REF], whereas the authors of another study noted that in their cohort of 45 patients, they were unable to use diagnostic MRIs to assess the T2WSI because of the low resolution [START_REF] Coopmans | T2-signal intensity, SSTR expression, and somatostatin analogs efficacy predict response to pasireotide in acromegaly[END_REF]. In addition, harmonization of the definitions used to define T2WSI categories would be more than welcomed to facilitate comparison between studies, but also to set a standard for the average clinician.

In conclusion, our prospective study confirms that SST2A receptor expression and adenoma granularity are good predictors of response to octreotide LAR. By contrast, we did not find that SST5 receptor expression was a good predictor. Scoring system harmonization is needed for SST expression, and we propose the use of IRS for this. Regarding adenoma granularity, densely granulated/intermediate adenomas were more responsive to octreotide than sparsely granulated adenomas, and expressed greater levels of SST2A receptor, coupled with lower levels of SST5 receptor. The majority of sparsely granulated adenomas from our cohort expressed high levels of SST5, and this subgroup might prove to be a good responder to pasireotide LAR. When MRI is of good quality, T2WSI might be an interesting predictive factor of response, with hypointense tumors responding better to first-generation SRLs than iso-or hyperintense tumors; however, harmonization of the used definitions and optimization of MRI sequences, appear necessary. In addition, T2WSI signal can change with SRL treatment, therefore caution regarding the choice of diagnostic vs pretreatment MRI to predict response to second-line SRLs is also needed.

Figure 1 .

 1 Figure 1. (A) Hypointense, (B) isointense, (C) hyperintense, and (D) heterogeneous T2-weighted MRI signal intensity. The white arrow indicates the cortex of the temporal lobe (B).

  8, n = 10 and median = 57.3; range, -51.5 to 93.2, n = 11), isointense (median = 26.4; range, -107.6 to 65.4, n = 6 and median = 35.8; range, -239.4 to 77.5, n = 6), and hyperintense adenomas (median = 40.5; range, 1.3-61.9, n = 5 and median = 13.7; range, -43.7 to 91.7, n = 6), P = 0.93 and P = 0.82, respectively.

Figure 2 .

 2 Figure 2. Patient flow in the study.

Figure 4 .

 4 Figure 4. Association analysis between adenoma granulation pattern and the percent reduction of (A) IGF-I and (B) GH, respectively, from month 0 to month 6 under octreotide long-acting release. Individual points (crosses) and mean (rhombus) are shown.

Figure 5 .

 5 Figure 5. Association analysis between adenoma granulation pattern and somatostatin receptor (A) SST2A IRS, (B) SST5 IRS, and (C) SST2A IRS/SST5 IRS ratio. Individual points (crosses) and mean (rhombus) are shown. Abbreviations: IRS, immunoreactive score; SST, somatostatin receptor.

Figure 6 .

 6 Figure 6. Examples of cytokeratin 18, somatostatin (SST)2A and SST5 receptor immunohistochemistry in a densely granulated adenoma vs a sparsely granulated adenoma (original magnification, ×200), showing a diffuse cytoplasmic and perinuclear distribution of cytokeratin 18, an SST2A receptor immunoreactive score (IRS) of 12, and an SST5 receptor IRS of 2 for the densely granulated adenoma vs cytokeratin 18-positive "fibrous bodies" (dot-pattern), an SST2A receptor IRS of 4, and an SST5 receptor IRS of 12 for the sparsely granulated adenoma.

Figure 7 .

 7 Figure 7. Association analysis between T2-weighted MRI signal intensity (evaluated on the preoperative MRI) and somatostatin receptor (A) SST5 IRS, (B) SST2A IRS, and (C) SST2A IRS/SST5 IRS ratio. Individual points (crosses) and mean (rhombus) are shown. Abbreviations: IRS, immunoreactive score; ns, nonsignificant; SST, somatostatin receptor.

Table 1 . Patient and tumor characteristics Group 1 (n = 39) Group 2 (n = 8) Sex

 1

	Male (n, %)	24 (61.5%)	7 (87.5%)
	Female (n, %)	15 (38.5%)	1 (12.5%)
	Age (median with range)	44.5 (21.7-77.1)	38.9 (29.0-46.0)
	Type 2 diabetes (n, %)	7 (17.9%)	1 (12.5%)
	Months since acromegaly	6.8 (1.6-128.8)	12.8 (4.5-17.8)
	diagnosis (median with
	range)
	Months since adenoma was	4.2 (1.3-49.4)	9.8 (3.5-13.4)
	surgically removed
	(median with range)
	Tumor invasion into the
	cavernous sinus
	(preoperative MRI)
	Yes (n, %)	12 (30.7%)	3 (37.5%)
	No (n, %)	18 (46.2%%)	4 (50.1%)
	NA (n, %)	9 (23.1%)	1 (12.5%)
	T2-weighted MRI signal
	intensity (preoperative
	MRI)
	Hypointense (n, %)	11 (28.2%)	3 (37.5%)
	Isointense (n, %)

Table 3 .

 3 Contingency table summarizing the relationship between MRI T2 signal intensity and granulation pattern Downloaded from https://academic.oup.com/jcem/article/107/11/2982/6711554 by Novartis Pharma AG user on 11 April 2023

		Hypointense Isointense Hyperintense Total
	Densely	9	3	3	15
	granulated/
	intermediate
	Sparsely	3	5	5	13
	granulated
	Total	12	8	8	28

Acknowledgments

The authors thank the investigators of the EOLIA study: Antoine Tabarin, Gérald Raverot, Philippe Chanson, Lucile Moreau-Grangé, Anne-Francoise Cailleux, Franck Schillo, Brigitte Delemer, Olivier Chabre, Claire Briet, Pierre-Louis Colombo, Yves Reznik, Bernard Goichot, Rachel Desailloud, Veronique Kerlan, Luc Foubert, Thierry Brue, Christine Cortet, and Hélène Bihan; the statistical team of Novartis; and Dr. Artin Karapet for English proofreading.

Funding

Sponsorship for this study were funded by Novartis Pharma.

Data Availability

Some or all datasets generated during and/or analyzed during the current study are not publicly available but are available from the corresponding author on reasonable request.


We would like to revisit the commentary by Christaki and Patrozou [START_REF] Christaki | The kinetics of T regulatory cells in shock: beyond sepsis[END_REF] on regulatory T cells (Tregs) as significant modulators of various immune responses after severe injury. Indeed, we would like to add some very recent references that strongly reinforce their results.

Strong evidence indicates that, in septic conditions, increases in Tregs have deleterious consequences. In septic shock patients, augmented levels of Tregs signifi cantly and inversely correlated with decreased lymphocyte proliferation [START_REF] Venet | Increased circulating regulatory T cells (CD4(+)CD25 (+)CD127 (-)) contribute to lymphocyte anergy in septic shock patients[END_REF]. Th is phenomenon, recapitu lated after cecal ligation and puncture (CLP) in mice, was totally abrogated by using Foxp3 small interfering RNA (Foxp3 is a specifi c Treg transcription factor). In a similar model [START_REF] Nascimento | Role of regulatory T cells in long-term immune dysfunction associated with severe sepsis[END_REF], after mild CLP, mice presented with immunosuppression that dampened defenses against secondary infectious challenge (Legionella pneumo philia inoculation 15 days after CLP). Th e restoration of effi cient responses against infection was achieved thanks to anti-glucocorticoid-induced TNF receptor antibodies, known to abrogate Treg-mediated suppression. Lastly, a recent paper published in Blood [START_REF] Cavassani | The post sepsis-induced expansion and enhanced function of regulatory T cells create an environment to potentiate tumor growth[END_REF] reported that sepsisinduced immunosuppression resulted in a reduced immune tolerance that facilitated the rapid growth of solid tumors. Foxp3+ Tregs were responsible for this eff ect. Although tumors were sub cutaneously implanted (which is not relevant to septic patients), this indicates the occurrence of a major immunosuppressive state induced by sepsis and driven by Tregs in this model.

Collectively, and beyond Tregs (unfortunately not the sole bad guys in the game), these data highlight the profound impact of sepsis/injury on immune functions. Th is should stimulate basic research and development of innovative therapies for rebalancing immune homeostasis in severe critical illness.

Abbreviations

CLP, cecal ligation and puncture; Treg, regulatory T cell.

Competing interests

The authors declare that they have no competing interests.

Published: 20 December 2010