Clinical trials indicate efficacy of drugs inhibiting the mammalian target of rapamycin (mTOR) in the treatment of gastroenteropancreatic neuroendocrine tumours (GEP-NET); however, information on detailed expression and activity patterns of mTOR in these tumours is sparse. We investigated the expression of mTOR and expression as well as phosphorylation of its downstream targets 4EBP1, S6K and eIF4E in a cohort of 99 human GEP-NET by immunohistochemistry. We correlated our findings with clinicopathological variables and patient prognosis. We found that 61, 93, 80, 69, 57 and 79% of GEP-NET were positive for mTOR, 4EBP1, cytoplasmic phospho-4EBP1 (p-4EBP1), nuclear p-4EBP1, phospho-S6K (p-S6K) and phospho-eIF4E (p-eIF4E) respectively. mTOR expression and activity were higher in foregut than in midgut tumours. In foregut tumours, expression of mTOR was higher when distant metastases were present (P=0.035). Strong mTOR activity was associated with higher proliferative capacity. In patients with stage IV midgut tumours, strong p-S6K expression was associated with poor disease-specific survival (P=0.048). In conclusion, mTOR shows considerable variations in expression and activity patterns in GEP-NET in dependence of tumour location and metastatic status. We hypothesise that these differences in mTOR expression and activity might possibly influence response to mTOR inhibitors.
Atsuko Kasajima, Marianne Pavel, Silvia Darb-Esfahani, Aurelia Noske, Albrecht Stenzinger, Hironobu Sasano, Manfred Dietel, Carsten Denkert, Christoph Röcken, Bertram Wiedenmann and Wilko Weichert
Silvia Darb-Esfahani, Ralph M Wirtz, Bruno V Sinn, Jan Budczies, Aurelia Noske, Wilko Weichert, Areeg Faggad, Susanne Scharff, Jalid Sehouli, Guelten Oskay-Özcelik, Claudio Zamagni, Pierandrea De Iaco, Andrea Martoni, Manfred Dietel and Carsten Denkert
Epidemiological and cell culture studies indicate that ovarian carcinoma growth is dependent on estrogen stimulation. However, possibly due to the lack of a reliable biomarker that helps to select patients according to prognostically relevant estrogen receptor (ER) levels, clinical trials using anti-estrogenic therapeutics in ovarian carcinoma have had inconsistent results. Therefore, we tested if ER expression analysis by a quantitative method might be useful in this regard in formalin-fixed paraffin-embedded (FFPE) tissue. In a study group of 114 primary ovarian carcinomas expression of estrogen receptor 1 (ESR1) mRNA was analyzed using a new method for RNA extraction from FFPE tissue that is based on magnetic beads, followed by kinetic PCR. The prognostic impact of ESR1 mRNA expression was investigated and compared to ERα protein expression as determined by immunohistochemistry. In univariate survival analysis the expression level of ESR1 mRNA was a significant positive prognostic factor for patient survival (hazard ratio (HR) 0.230 (confidence interval (CI) 0.102–0.516), P=0.002). ERα protein expression was correlated to ESR1 mRNA expression (P=0.0001); however, ERα protein expression did not provide statistically significant prognostic information. In multivariate analysis, ESR1 mRNA expression emerged as a prognostic factor, independent of stage, grade, residual tumor mass, age, and ERα protein expression (HR 0.227 (CI 0.078–0.656), P=0.006). Our results indicate that the determination of ESR1 levels by kinetic PCR may be superior to immunohistochemical methods in assessment of biologically relevant levels of ER expression in ovarian carcinoma, and is feasible in routinely used FFPE tissue.