TRPM8 activation suppresses cellular viability in human melanoma

Abstract

The transient receptor potential melastatin subfamily (TRPM), which is a mammalian homologue of cell death-regulated genes in Caenorhabditis elegans and Drosophila, has potential roles in the process of the cell cycle and regulation of Ca(2+) signaling. Among this subfamily, TRPM8 (also known as Trp-p8) is a Ca(2+)-permeable channel that was originally identified as a prostate-specific gene upregulated in tumors. Here we showed that the TRPM8 channel was expressed in human melanoma G-361 cells, and activation of the channel produced sustainable Ca(2+) influx. The application of menthol, an agonist for TRPM8 channel, elevated cytosolic Ca(2+) concentration in a concentration-dependent manner with an EC(50) value of 286 microM in melanoma cells. Menthol-induced responses were significantly abolished by the removal of external Ca(2+). Moreover, inward currents at a holding potential of -60 mV in melanoma cells were markedly potentiated by the addition of 300 microM menthol. The most striking finding was that the viability of melanoma cells was dose-dependently depressed in the presence of menthol. These results reveal that a functional TRPM8 protein is expressed in human melanoma cells to involve the mechanism underlying tumor progression via the Ca(2+) handling pathway, providing us with a novel target of drug development for malignant melanoma.

Dose-Dependent Cytotoxic Effects of Menthol on Human Malignant Melanoma A-375 Cells: Correlation with TRPM8 Transcript Expression

“…Although a similar result has previously been reported on the G-361 malignant melanoma cell line (Yamamura et al, 2008), the IC 50 value of menthol on the A-375 line reported here was over 20-fold lower, suggesting a significant difference in the menthol sensitivity between the two cell lines. Several diverse studies have reported that menthol elicits an increase in the cytosolic calcium concentration (Behrendt et al, 2004;Yamamura et al, 2008;Kim et al, 2009;Latorre et al, 2011;Liu and Qin, 2011), and so it has been suggested that the menthol-triggered increased cytosolic Ca 2+ by TRPM8 action in A-375 cells might cause an ion imbalance and lead to cell death, similar to the prostate cancer cell model (Zhang and Barritt, 2006;Liu and Qin, 2011). Additionally, compared with 5-FU treatment, menthol was at least as effective as 5-FU in the in vitro cytotoxicity of the A-375 cell line, with an IC 50 for menthol of 11.8 µM ( Figure 2B) compared to 120 µM for 5-FU.…”

“…Several reports show that menthol triggers an increase in cytosolic Ca 2+ levels (Behrendt et al, 2004;Yamamura et al, 2008;Kim et al, 2009), leading to downstream Ca 2+ -dependent cell signaling pathways. With respect to its bioactivity, some studies have recently reported on the efficiency of menthol in killing cancer cells such as gastric, leukemia, prostate, colorectal adenocarcinoma and skin (melanoma) cancers (Lin et al, 2005;Lu et al, 2006;Yamamura et al, 2008;Kim et al, 2009;Lu et al, 2009;Faridi et al, 2011), but few studies have pointed out a mechanism. Rather, it is still controversial as to whether the process involves or is related to TRPM8 (Yamamura et al, 2008;Kim et al, 2009).…”

“…Surgical removal of the melanoma is used to cure the disease in early stages when still small and not spread with good success, but this is ineffective once the cancer cells have started to metastasize. Several traditional non-surgical methods, such as radiotherapy and/or chemotherapy, are not successful enough because of melanoma resistance (Yamamura et al, 2008) and RESEARCH ARTICLE…”

Tryptamine-Based Derivatives as Transient Receptor Potential Melastatin Type 8 (TRPM8) Channel Modulators

“…The non-substituted N-1 indole derivatives (8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21) were quite productive. A direct linkage of the amine moiety with different bulky aromatic groups, such as naphthalene and quinolines, gives compounds 8-11 unable to act as TRPM8 modulators ( Figures 1A and 1B).…”

“…Apart from androgen-sensitive prostate cancer, TRPM8 is abnormally over-expressed in other tumor malignancies, like breast cancer, 7,8 human pancreatic adenocarcinoma, 9 and skin melanoma cells. 10 Concurrently, TRPM8 blockers have been investigated for the treatment of overactive and painful bladder syndromes. 11 In particular, N-(3-Aminopropyl)-2-[(3-methylphenyl)methoxy]-N-(2-thienylmethyl) benzamide (AMTB), a well-recognized TRPM8 antagonist, can attenuate the bladder micturition reflex and the nociceptive reflex response in the rat, thus decreasing the frequency of volume-induced bladder contraction.…”