Overexpression of short TRPM8 variant a promotes cell migration and invasion, and decreases starvation-induced apoptosis in prostate cancer LNCaP cells

The aim of the present study was to investigate the function of a transient receptor potential melastatin 8 (TRPM8) splice variant, short TRMP8 alpha (sM8 alpha), in the androgen-dependent prostate cancer LNCaP cell line, and to evaluate the potential involvement of the mitogen-activated protein kinase (MAPK) signaling pathway. The coding DNA for sM8 alpha was cloned and transfected into INCaP cells to generate cells that overexpress this isoform of TRPM8. Cellular proliferation was determined by performing an MTT assay, and flow cytometry was used to analyze apoptosis and cell cycle distribution. Furthermore, cellular migration and invasion were evaluated using Transwell (R) migration assays. The subcellular location of recombinant sM8a was detected by quantum dots-based immunofluorescent imaging, western blotting was performed to examine the expression levels of proteins in the MAPK signaling pathway and reverse transcription-polymerase Chain reaction was used to determine the expression of sM8a :mRNA transcripts. The present study demonstrated that sM8a :mRNA was expressed at a low level in the LNCaP, DU145 and PC-3 prostate cancer cell lines. Additionally, the recombinant sM8a protein was located in the cytoplasm of LNCaP cells and its overexpression significantly reduced starvation-induced apaptosis in these cells (P<0.05), possibly by means of reduced activation of phosphorylated-c-Jun N-terminal kinase (p-JNK). The migration and invasion of the LNCaP cells were markedly enhanced by the overexpression of sM8 alpha, possibly via activation of MMP-2. Furthermore, overexpression of sM8 alpha in LNCaP cells did not alter the expression of full-length TRPM8 and had no effect on cellular proliferation. Overall, the results of the present study indicate that sM8 alpha may be important in the regulation of prostate cancer cell migration and invasion through the activation of matrix metalloproteinase-2, as well as in the regulation of apoptosis through the activation of p-JNK in the MAPK signaling pathway.