Neoplastic epithelial cells generate the most aggressive types of cancers such as those located in the lung, breast, colon, prostate and ovary. During advanced stages of prostate cancer, epithelial cells are associated to the appearance of androgen-independent tumors, an apoptotic-resistant phenotype that ultimately overgrows and promotes metastatic events. We have previously identified and electrophysiologically characterized a novel Ca2+-permeable channel activated during apoptosis in the androgen-independent prostate epithelial cancer cell line, LNCaP.
In addition, we reported for the first time the cloning and characterization of this channel-like molecule named apoptosis regulated protein 2 (ARP2) associated to a lethal influx of Ca2+ in Xenopus oocytes. In the present study, LNCaP cells and Chinese hamster ovary cells (CHO cell line) transfected with arp2-cDNA are induced to apoptosis showing an important impact on cell viability and activation of caspases 3 and 7 when compared to serum deprived grown cells and ionomycin treated cells. The subcellular localization of ARP2 in CHO cells undergoing apoptosis was studied using confocal microscopy. While apoptosis progresses, ARP2 initially localized in the peri-nuclear region of cells migrates with time towards the plasma membrane region. Based on the present results and those of our previous studies, the fact that ARP2 constitutes a novel cation channel is supported.
Therefore, ARP2 becomes a valuable target to modulate the influx and concentration of calcium in the cytoplasm of epithelial cancer cells showing an apoptotic-resistant phenotype during the onset of an apoptotic event.
Figure. Confocal microscopy of ARP2 fusion protein expressed in CHO cells. CHO cells transfected with arp2-egfp cDNA examined at 16, 24, 48 and 72 h post-transfection (A, C, E and G respectively). Same using DIC microscopy (B, D, F and H respectively). Scale bar 10 mm.