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

Abstract

Abstract. The aim of the present study was to investigate the function of a transient receptor potential melastatin 8 (TRPM8) splice variant, short TRMP8α (sM8α), 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 sM8α was cloned and transfected into LNCaP 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 ® migration assays. The subcellular location of recombinant sM8α 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 sM8α mRNA transcripts. The present study demonstrated that sM8α mRNA was expressed at a low level in the LNCaP, DU145 and PC-3 prostate cancer cell lines. Additionally, the recombinant sM8α protein was located in the cytoplasm of LNCaP cells and its overexpression significantly reduced starvation-induced apoptosis 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 sM8α, possibly via activation of MMP-2. Furthermore, overexpression of sM8α 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 sM8α 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.

Differential Impacts of Alternative Splicing Networks on Apoptosis

“…In addition to full-length transcripts, short sM8α and sM8β were generated from the TRPM8 gene through alternative splicing regulation [65]. Spatial expressions of TRPM8 isoforms were noted in lung tissues and prostate cancer [67]. These short transcripts encode the N-terminus region of the TRPM8 protein, and were demonstrated to manipulate the activity and sensitivity of authentic TRPM8 [67].…”

“…Spatial expressions of TRPM8 isoforms were noted in lung tissues and prostate cancer [67]. These short transcripts encode the N-terminus region of the TRPM8 protein, and were demonstrated to manipulate the activity and sensitivity of authentic TRPM8 [67]. Overexpression of sTRPM8α, but not sTRPM8β, substantially abolished starvation-induced apoptosis of several prostate cancer cells [66].…”

“…Overexpression of sTRPM8α, but not sTRPM8β, substantially abolished starvation-induced apoptosis of several prostate cancer cells [66]. Moreover, the presence of sTRPM8α overexpression largely enhanced the activity of metalloproteinase-2, which subsequently induced progression of LNCaP prostate cancer cells [67]. In contrast, the influence of sTRPM8β is largely uncharacterized.…”

The oncogenic roles of TRPM ion channels in cancer

“…Activities of TRPM8 were required for the chemotaxis and migration of glioblastoma cells (T98G and U-87MG) as shown by siRNA-mediated downregulation of TRPM8, pharmacological inhibition by the TRP channel blocker BCTC or TRPM8 activation by icilin (Klumpp et al, 2017). The authors reported that TRPM8 promoted migration of these glioblastoma cells possibly through activation of Ca 2+ -regulated K + channel, that is, big conductance Moreover, independent groups of researchers demonstrated that TRPM8 short isoforms localized in the cytoplasm (in contrast to the full-length TRPM8 localized on the plasma membrane) were required for the survival, migration, and invasion of prostate cancer cells (LNCaP; Bidaux et al, 2016;Peng et al, 2015). Multiple non-channel cytoplasmic TRPM8 isoforms, consisting of sM8α, sM8β, sM8γ, sM8δ, sM8ε, sM8ζ, and sM8η (both sM8ζ and sM8η do not encode protein), collectively termed as sM8, were found to be expressed in prostate cancer cell lines (PC3, LNCaP, and LNCaP C4-2b; Bidaux et al, 2016).…”

Molecular mechanisms of tumour invasion: regulation by calcium signals

“…, ), whereas the short TRPM8 isoform could have a pro‐metastatic potential (Peng et al . ; Bidaux et al . ).…”