Characterizing the Calcium Sensing Receptor in the progression of the metastatic phenotype of prostate cancer cells
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Background: Prostate cancer (PCa) is one of the most common cancers in the world. Obesity increases risk for fatal PCa and increases the aggressive phenotype of PCa cells. Calcium sensing receptor (CaSR) is correlated with lethal PCa and bone metastasis which is the most likely site for secondary PCa tumors. We hypothesize sera from obese males increase CaSR-mediated PCa progression. Methods: PC3 and DU145 PCa cells were treated with 5% sera from obese (BMI>30) or normal weight (BMI<25) males. Cells were treated with 5μM 2-Chloro-6-[(2R)-3-[[1,1-dimethyl-2-(naphthalenyl)ethyl]amino-2-hyroxypropoxy]benzonitrile hydrochloride (NPS-2143) to determine the effect of CaSR on PCa cells. Western blot analysis determined protein expression of pAKT, pERK, tumor necrosis factor (TNF)-α, cyclooxygenase (COX-2), interleukin (IL)-6, and CaSR. mRNA levels of ion channels important to PCa progression including receptor activator of nuclear factor kappa-B (RANK), RANKL, CaSR, parathyroid hormone related peptide (PTHrP), transient receptor potential (TRP)M7, and TRPC6 were also assessed. MMP-9 activity, invasive capacity, and wound healing were also assessed. Results: Obese sera increased the invasive capacity of PCa cells, as well as de-localized EMT markers from the cell membranes which was attenuated with CaSR inhibition. CaSR contributed to MMP-9 activity in DU145 cells treated with normal weight sera. CaSR contributed to mRNA expression of PTHrP in PC3 cells treated with obese sera. Obese sera increased and protein expression of COX-2, IL-6, and CaSR in DU145 cells. Inhibition of CaSR decreased protein levels of phosphorylated ERK in DU145 cells treated with obese sera, and TNF-α in DU145 cells treated with normal weight sera. Conclusion: Obese sera was shown to promote the invasive-phenotype and protein expression of important factors in PCa tumorigenesis. The obesity-mediated invasive capacity and expression of COX-2 and IL-6 were similar to control when treated with the CaSR inhibitor, NPS-2143. CaSR may be an important protein to target for obesity-mediated PCa progression.