Morphoproteomic analysis reveals an overexpressed and constitutively activated phospholipase D1-mTORC2 pathway in endometrial carcinoma.

The mammalian target of rapamycin (MTOR) assembles into two distinct complexes: mTOR complex 1 (mTORC1) is predominantly cytoplasmic and highly responsive to rapamycin, whereas mTOR complex 2 (mTORC2) is both cytoplasmic and nuclear, and relatively resistant to rapamycin. mTORC1 and mTORC2 phosphorylatively regulate their respective downstream effectors p70S6K/4EBP1, and Akt. The resulting activated mTOR pathways stimulate protein synthesis, cellular proliferation, and cell survival. Moreover, phospholipase D (PLD) and its product, phosphatidic acid (PA) have been implicated as one of the upstream activators of mTOR signaling. In this study, we investigated the activation status as well as the subcellular distribution of mTOR, and its upstream regulators and downstream effectors in endometrial carcinomas (ECa) and non-neoplastic endometrial control tissue. Our data show that the mTORC2 activity is selectively elevated in endometrial cancers as evidenced by a predominant nuclear localization of the activated form of mTOR (p-mTOR at Ser2448) in malignant epithelium, accompanied by overexpression of nuclear p-Akt (Ser473), as well as overexpression of vascular endothelial growth factor (VEGF)-A isoform, the latter a resultant of target gene activation by mTORC2 signaling via hypoxia-inducible factor (HIF)-2alpha. In addition, expression of PLD1, one of the two major isoforms of PLD in human, is increased in tumor epithelium. In summary, we demonstrate that the PLD1/PA-mTORC2 signal pathway is overactivated in endometrial carcinomas. This suggests that the rapamycin-insensitive mTORC2 pathway plays a major role in endometrial tumorigenesis and that therapies designed to target the phospholipase D pathway and components of the mTORC2 pathway should be efficacious against ECa.

Genetic variations in the PI3K-AKT-mTOR pathway and bladder cancer susceptibility and clinical outcomes

Bladder cancer is the fourth most common cancer in men in the United States. There is compelling evidence supporting that genetic variations contribute to the risk and outcomes of bladder cancer. The PI3K-AKT-mTOR pathway is a major cellular pathway involved in proliferation, invasion, inflammation, tumorigenesis, and drug response. Somatic aberrations of PI3K-AKT-mTOR pathway are frequent events in several cancers including bladder cancer; however, no studies have investigated the role of germline genetic variations in this pathway in bladder cancer. In this project, we used a large case control study to evaluate the associations of a comprehensive catalogue of SNPs in this pathway with bladder cancer risk and outcomes. Three SNPs in RAPTOR were significantly associated with susceptibility: rs11653499 (OR: 1.79, 95%CI: 1.24–2.60), rs7211818 (OR: 2.13, 95%CI: 1.35–3.36), and rs7212142 (OR: 1.57, 95%CI: 1.19–2.07). Two haplotypes constructed from these 3 SNPs were also associated with bladder cancer risk. In combined analysis, a significant trend was observed for increased risk with an increase in the number of unfavorable genotypes (P for trend<0.001). Classification and regression tree analysis identified potential gene-environment interactions between RPS6KA5 rs11653499 and smoking. In superficial bladder cancer, we found that PTEN rs1234219 and rs11202600, TSC1 rs7040593, RAPTOR rs901065, and PIK3R1 rs251404 were significantly associated with recurrence in patients receiving BCG. In muscle invasive and metastatic bladder cancer, AKT2 rs3730050, PIK3R1 rs10515074, and RAPTOR rs9906827 were associated with survival. Survival tree analysis revealed potential gene-gene interactions: patients carrying the unfavorable genotypes of PTEN rs1234219 and TSC1 rs704059 exhibited a 5.24-fold (95% CI: 2.44–11.24) increased risk of recurrence. In combined analysis, with the increasing number of unfavorable genotypes, there was a significant trend of higher risk of recurrence and death (P for trend<0.001) in Cox proportional hazard regression analysis, and shorter event (recurrence and death) free survival in Kaplan-Meier estimates (P log rank<0.001). This study strongly suggests that genetic variations in PI3K-AKT-mTOR pathway play an important role in bladder cancer development. The identified SNPs, if validated in further studies, may become valuable biomarkers in assessing an individual's cancer risk, predicting prognosis and treatment response, and facilitating physicians to make individualized treatment decisions. ^