Evidence that TRPM8 Is an Androgen-Dependent Ca2+ Channel Required for the Survival of Prostate Cancer Cells

Abstract

The Ca 2؉ -permeable channel TRPM8 is thought to play an important role in the pathophysiology of prostate cancer. We have investigated the intracellular location of TRPM8 and its role as a Ca 2؉ -permeable channel in an androgen-responsive and an androgen-insensitive prostate cancer cell line. We report evidence from immunofluorescence experiments that in the androgen-responsive LNCaP cell line, the TRPM8 protein is expressed in the endoplasmic reticulum and plasma membrane, acts as a Ca 2؉ -permeable channel (assessed using Fura-2 to measure increases in the cytoplasmic Ca 2؉ concentration) in each of these membranes, and is regulated by androgen. Although TRPM8 was detected in the androgeninsensitive PC-3 cell line, no evidence was obtained for regulation of its expression by androgen. The results of experiments using LNCaP cells, the TRPM8 antagonist capsazepine, and small interference RNA targeted to TRPM8 indicate that TRPM8 is required for cell survival. These results indicate that TRPM8 is an important determinator of Ca 2؉ homeostasis in prostate epithelial cells and may be a potential target for the action of drugs in the management of prostate cancer.

TRPM8-independent Menthol-induced Ca2+ Release from Endoplasmic Reticulum and Golgi

“…Later studies have reported similar menthol-induced Ca 2ϩ release in TRPM8-expressing LNCaP cells and dorsal root ganglion neurons (4,7,8), leading to the hypothesis that TRPM8 can function as an intracellular Ca 2ϩ -release channel. Further support to this idea came from immunocytochemical stainings indicating that TRPM8 is significantly or even exclusively located on intracellular membranes in LNCaP cells (7,8). However, our present data indicate that these results should be interpreted with caution.…”

“…Alternatively, menthol may activate a Ca 2ϩ -release pathway different from the well characterized IP 3 and ryanodine receptors. Several recent studies have suggested that members of the TRP channel superfamily, including TRPP2 (polcystin 2) (26), TRPV1 (27), and TRPM8 (7,8), can function as release channels on intracellular membranes. Although our experiments allow discarding TRPM8 as menthol target in our experiments with HEK293 cells, the involvement of other TRP channels in the menthol-induced release phenomenon mandates further investigation.…”

“…3F). As previous studies reporting that endogenous TRPM8 in LNCaP cells is to a large extent or even fully restricted to intracellular compartments used the commercial anti-TRPM8 antibodies (7,8), we repeated immunocytochemical staining of LNCaP using our new anti-TRPM8 antibody. In contrast to the results from these previous studies, the staining pattern that we obtained was consistent with a principally plasma- lemmal localization of TRPM8 (Fig.…”

“…Yet, the function of TRPM8 in non-sensory cells and particularly its relation to the pathophysiology of cancer cells are currently unknown. Recent studies have suggested that TRPM8, besides its established function as a plasmalemmal channel, can also be found in the ER membrane of the androgenresponsive LNCaP prostate cell line, where it may function as a menthol-and cold-sensitive intracellular Ca 2ϩ -release channel (7,8). In addition, menthol-induced release of Ca 2ϩ from intracellular stores has been reported in other different cell types, including skeletal muscle (9), tracheal epithelial cells (10), and dorsal horn neurons (11).…”

Novel role for the transient receptor potential channel TRPM2 in prostate cancer cell proliferation

“…23 TRPM8 is highly expressed in endoplasmic reticulum membrane as an ion channel in prostate cancer cells and has an essential role in prostate cancer cell survival. 24 30 Another example is, cADP-ribose, an endogenous regulator of type 2 ryanodine receptors that induces Ca 2 þ release from nuclear stores. 31 More detailed information concerning the nuclear location of TRPM2 will be useful in advancing our knowledge of this aspect of prostate cancer proliferation.…”