Introduction and objective Dysregulation of Mammalian target of rapamycin pathway has been shown in various cancers. Phosphorylated 70S6k is a vital downstream signalling protein of this pathway, dysregulation of this protein has also been linked to various malignancies and potentially to patient survival. In this study, we aimed to investigate the expression of phosphorylated 70S6K in MPM and evaluate its relationship with patient survival. Methods We performed immunohistochemical analysis on archival MPM tissue samples to examine the expression of phosphorylated 70S6K. Western blot analysis was also performed to evaluate the expression this protein in MPM cell lines. Histopathological and clinical data of relevant patients were obtained from Hull Royal Infirmary. Univariate analysis was performed for protein expression using Kaplan Meier survival curves with log rank analysis. Multivariate Cox regression analysis taking histological subtypes into account was performed, to assess the effect of phosphorylated 70S6K expression on patient survival. Results Our cohort consisted of total 79 archival MPM samples which included 43 Epithelioid, 24 Biphasic, and 12 Sarcomatoid MPM tissue samples. Of these 79 samples, 45 (57%) were found to be negative for Phospho 70s6K expression while 34 (43.%) showed positive expression. A significant difference in expression of phospho 70s6K was found between MPM subtypes, on immunohistochemistry (p=0.01). Phospho 70S6K protein was expressed in MSTO-211H and A549 cells, very weak expression in the NCI-H2452 cells was detected but none in the NCI-H2052 cell. No significant difference in survival was found between patients who had positive and negative phospho 70s6K expression (p=>0.05). Conclusion Our data suggest that phosphorylated 70S6K is expressed in MPM and there was a difference in expression of phospho 70s6K between MPM subtypes. No statistically significant association was found between phosphorylated 70S6K expression and patient prognosis.

Background Dysregulation of the PI3K/AKT/mTOR pathway has been observed in various cancers and has also been suggested to be involved in mesothelioma. In some cancers, a significant association has been found between the expression of these proteins and patient survival. In this study, we aimed to investigate the expression of phosphorylated AKT/mTOR in our archival MPM tissue samples and evaluate their relationship with patient survival. Methods Immunohistochemistry was performed on 82 archival MPM tissue samples to examine the expression of phosphorylated AKT/mTOR. Histopathological and clinical data of relevant patients were obtained from Hull Royal Infirmary. Mesothelioma tissues with >25% staining were grouped as positive while tissues with <25% staining were grouped as negative. Colorectal cancer tissues were used as positive and negative controls. Univariate analysis for protein expression and histological subtypes was performed using Kaplan Meier survival curves with log rank analysis. Multivariate Cox regression analysis taking histological subtypes into account was performed, to assess the effect of phosphorylated AKT/mTOR expression on patient survival. Results Our data set included 44 epithelioid, 24 biphasic and 14 sarcomatoid tissue samples. Of the MPM tissues samples, 63.41% demonstrated positive expression for phosphorylated mTOR protein while 61.73% showed positive phosphorylated AKT expression. We did not observe a significant difference in expression of phosphorylated AKT/mTOR between the histological subtypes of MPM (p>0.05). Positive expression of phosphorylated AKT/mTOR proteins was not associated with survival in Kaplan Meier survival curve analysis (p>0.05). When histological subtypes were taken into account, multivariate Cox regression analysis demonstrated that neither phosphorylated mTOR nor phosphorylated AKT expression were independent prognostic factors for survival (p>0.05). Conclusion Our data suggest that phosphorylated AKT/mTOR are expressed in a significant proportion of MPM samples. However, no statistically significant association was found between phosphorylated AKT/mTOR/expression and patient prognosis. Reference Li S, Wang Z, Huang J, Cheng S, Du H, Che G, Peng Y. Clinicopathological and prognostic significance of mTOR and phosphorylated mTOR expression in patients with esophageal squamous cell carcinoma: A systematic review and meta-analysis. BMC Cancer 2016;16(1):877.