Multiple mechanisms are involved in PKCε-regulated tumorigenesis. For example, PKCε promotes cell proliferation
and survival by regulating the Ras signaling pathway, which is a well characterized signaling pathway in cancer biology [10, 34]. PKCε expression is related to the activation of cyclin D1 promoter, a downstream effects of Ras signaling, and to enhanced cell growth [9–11]. In addition, PKCε plays a role in anti-apoptotic signaling pathways through interacting with caspases and Bcl-2 family members [35, 36], and exerts its GSK3235025 purchase pro-survival effects by activating Akt/PKB [27, 37]. These mechanisms may explain the inhibited growth of RCC cells by PKCε knockdown in our study. Like in other cancer types, relapse and metastasis are the main causes of failure of surgical operation in treating clear cell RCC. Patients with RCC response to postoperative adjuvant chemotherapy at various levels and usually cannot achieve expected outcomes . The phenotype of tumor metastasis presents with promotion of cell proliferation, escape from apoptosis, and dysregulation of cellular adhesion and migration. The selleck invasion of tumor cells to surrounding tissues and spreading to distal sites rely on cell migration ability. Cell migration, a complex event, depends on the coordinated remodeling of the actin cytoskeleton, regulated assembly, and turnover
of focal adhesion . Interestingly, PKCε contains an actin-binding domain  and promotes F-actin assembly in a cell-free system, indicating that PKCε modulates cell migration via actin polymers. In addition, PKCε has been observed to translocate
to the cell membrane during the formation of focal adhesions  and to reverse the effect of non-signaling β1-integrin molecules in inhibiting cell spreading . PKCε-driven cell migration was shown to be mediated, at least in part, by activating downstream small Rho GTPases, especially RhoA and/or RhoC . We found that silencing PKCε by RNAi decreased migration and invasion of clear cell RCC cells in vitro, suggesting that PKCε may be one of the potential treatment targets for this disease. Additionally, PKCε is also cleaved by caspases in response to several apoptotic stimuli including oxyclozanide chemotherapeutic agents. PKCε is a substrate for caspase-3 as evidenced by caspase-3-caused PKCε cleavage and the inhibition of PKCε cleavage by a cell permeable inhibitor of caspase-3 . PKCε has been shown to regulate apoptosis mediated by either DNA damage or receptor . PKCε up-regulation was associated with chemoresistance of non-small cell lung cancer (NSCLC) cell lines, whereas chemosensitivity was proved in PKCε-knockdown SCLC cells . In addition, PKCε was reported to mediate with induction of the drug-resistance gene P-glycoprotein in LNCaP cells .