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Loss of TSC1 function, a crucial negative regulator of mTOR signaling, is a common alteration in bladder cancer. Mutations in other members of the PI3K pathway, leading to mTOR activation, are also found in bladder cancer. This provides rationale for targeting mTOR for treatment of bladder cancer characterized by TSC1 mutations and/or mTOR activation. In this study, we asked whether combination treatment with rapamycin and resveratrol could be effective in concurrently inhibiting mTOR and PI3K signaling and inducing cell death in bladder cancer cells. In combination with rapamycin, resveratrol was able to block rapamycin-induced Akt activation, while maintaining mTOR pathway inhibition. In addition, combination treatment with rapamycin and resveratrol induced cell death specifically in TSC1-/- MEF cells, and not in wild-type MEFs. Similarly, resveratrol alone or in combination with rapamycin induced cell death in human bladder cancer cell lines. These data indicate that administration of resveratrol together with rapamycin may be a promising therapeutic option for treatment of bladder cancer. J. Cell. Physiol. 232: 436-446, 2017. © 2016 Wiley Periodicals, Inc.

Class I PI 3-kinases signal by producing the signaling lipid phosphatidylinositol(3,4,5) trisphosphate, which in turn acts by recruiting downstream effectors that contain specific lipid-binding domains. The class I PI 3-kinases comprise four distinct catalytic subunits linked to one of seven different regulatory subunits. All the class I PI 3-kinases produce the same signaling lipid, PIP3, and the different isoforms have overlapping expression patterns and are coupled to overlapping sets of upstream activators. Nonetheless, studies in cultured cells and in animals have demonstrated that the different isoforms are coupled to distinct ranges of downstream responses. This review focuses on the mechanisms by which the production of a common product, PIP3, can produce isoform-specific signaling by PI 3-kinases.

The K + channel KCa3.1 is required for Ca 2+ influx and the subsequent activation of CD4 T cells. The class II phosphatidylinositol 3 kinase C2β (PI3KC2β) is activated by the T-cell receptor (TCR) and is critical for KCa3.1 channel activation. Tripartite motif containing protein 27 (TRIM27) is a member of a large family of proteins that function as Really Interesting New Gene (RING) E3 ubiquitin ligases. We now show that TRIM27 functions as an E3 ligase and mediates lysine 48 polyubiquitination of PI3KC2β, leading to a decrease in PI3K enzyme activity. By inhibiting PI3KC2β, TRIM27 also functions to negatively regulate CD4 T cells by inhibiting KCa3.1 channel activity and TCR-stimulated Ca 2+ influx and cytokine production in Jurkat, primary human CD4 T cells, and Th0, Th1, and Th2 CD4 T cells generated from TRIM27 −/− mice. These findings provide a unique mechanism for regulating class II PI3Ks, and identify TRIM27 as a previously undescribed negative regulator of CD4 T cells.

Lymphangioleiomyomatosis (LAM) is a rare neoplastic metastatic disease affecting women of childbearing age. LAM is caused by hyperactivation of the mechanistic target of rapamycin complex 1 (mTORC1) as a consequence of tuberous sclerosis complex (TSC) 1/2 inactivation. Clinically, LAM results in cystic lung destruction. mTORC1 inhibition using rapamycin analogs (rapalogs) is partially effective in reducing disease progression and improving lung function. However, cessation of treatment results in continued progression of the disease. In the present study, we investigated the effectiveness of the combination of rapamycin treatment with resveratrol, an autophagy inhibitor, in the TSC2-null xenograft tumor model. We determined that this combination inhibits phosphatidylinositol-4,5-bisphosphate 3-kinase PI3K/Akt/mTORC1 signaling and activates apoptosis. Therefore, the combination of rapamycin and resveratrol may be an effective clinical strategy for treatment of LAM and other diseases with mTORC1 hyperactivation.