Silencing the Cav2.3 Calcium Channel Decreases the Expression of Phosphorylated AKT and Ribosomal Protein S6 in Transformed Mouse Ovarian Surface Epithelial Cells.

Epithelial ovarian cancer has a high mortality rate and is among the most common gynecological malignancies in developed countries. Our laboratory has shown previously that the voltage-sensitive calcium channel Cav2.3 modulates ovarian cancer cell proliferation. Specifically, we found that RNA silencing of Cav2.3 expression inhibits the proliferation of ID8 cells in the presence and absence of epidermal growth factor (EGF). Using immunoblotting (n ≥ 3), we show here that in the tumorigenic transformed mouse ovarian epithelial cell line ID8, EGF-stimulation of cell proliferation is associated with phosphoryation of the EGF receptor (Y845, Y1045 and Y1068), ERK1/2 (T202/Y204), Src (Y416), AKT (S473) and ribosomal protein S6 (S235/S236). On the basis of these data, we examined the effects of silencing Cav2.3 on components of the growth factor signaling pathways associated with Src-Ras-Raf-MEK-ERK and PI3K-AKT-mTOR. In ID8 cells, silencing of Cav2.3 had minimal effects on expression of phosphorylated Src and ERK1/2, whereas the expression of phosphorylated AKT and S6 were significantly diminished. Knockdown of Cav2.3 had similar effects on phosphorylated AKT and S6 in chemoresistant ID8 cells. To our knowledge, these data provide the first evidence linking the Cav2.3 channel to the PI3K-AKT-mTOR pathway. Further work will be needed to elucidate the role of Cav2.3 in various aspects of ovarian cancer progression linked to downstream targets of mTOR such as S6 kinase, as well as to determine if targeting Cav2.3 is a useful strategy for treatment of ovarian cancer. This work was supported by the Kansas State University College of Veterinary Medicine, the Terry C. Johnson Center for Basic Cancer Research, and the COBRE Confocal Microscopy Facility and Molecular Biology Support Cores (NIH P20-RR017686). (poster)