Regulation of hormone responsive cancers by Ca 2+ /calmodulindependent protein kinase kinase 2
Gocher, Angela M.
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Steroid Receptors (SR) are oncogenic drivers of proliferation in hormonally regulated cancers. Immunohistochemistry (IHC) studies have shown high expression levels of Ca2+/calmodulin-dependent kinase kinase 2 (CaMKK2), an upstream regulator of multiple downstream kinases, in a variety of hormone stimulating cancers including prostate (PCa), breast (BCa) and ovarian (OvCa) cancer. Recent studies have shown that CaMKK2 plays a role in BCa and PCa cell cycle kinetics and that CaMKK2 is hormonally regulated by the Androgen Receptor (AR) in the latter by its cognate ligands Dihydrotestosterone (DHT) and Testosterone (T). I report here that in LNCaP PCa cells, E2 (17-β Estradiol) and progesterone regulate CaMKK2 in a dose- and time-dependent manner through activity at the AR, rather than via their cognate receptors. In MCF-7 BCa cells neither DHT, progesterone, or E2 treatment nor steroid derivation affected CaMKK2 levels. These data suggest that the hormonal regulation of CaMKK2 may be specific to PCa, an AR driven cancer, or to other cancers specific to males. In OVCAR-3 OvCa cells CaMKK2 knockdown via RNAi, significantly decreased the number of viable cells. The slowing in growth was accompanied by a decrease in cyclin D1 nuclear and cytoplasmic protein, as well as cyclin D1 mRNA, levels. Consistent with the decrease in cyclin D1 levels was a significant drop in the phosphorylation of retinoblastoma protein. These data suggest that there is a block in the G1/S interface of the cell cycle with CaMKK2 knockdown in OvCa cells. CaMKK2 knockdown produced a significant decrease in the viability of OVCAR-3 cells. Complementing cell death induced by CaMKK2 silencing was a decrease in the phosphorylation of the anti-apoptotic protein, Akt and an increase in PARP cleavage. These data suggest that the cell death of CaMKK2 silenced OVCAR-3 cells is due to apoptosis. Together the results of my dissertation suggest that CaMKK2 is required for optimal growth and viability of OVCAR-3 cells. These data also imply that CaMKK2 may be a promising and novel therapeutic target for OvCa.