Panoply™ Human KCNK9 Over-expressing Stable Cell Line

The primary function of two-pore-domain potassium (K2P) channels is to maintain the cellular resting membrane potential-a prerequisite essential for numerous biological processes. As a member of the K2P family, KCNK9 is considered to be intimately linked to the initiation and progression of cancer, given its overexpression in human tumors and its capacity to promote tumor cell survival and proliferation. However, due to a lack of specific modulators, the precise mechanisms by which KCNK9 contributes to the progression of malignant tumors remain elusive. Here, researchers report the development and functional characterization of monoclonal antibodies targeting the extracellular domain of KCNK9. The results demonstrate that one such antibody-designated Y4-exhibiting the highest binding affinity, is capable of inducing the endocytosis of KCNK9 channels. The addition of Y4 to cultures of KCNK9-expressing cancer cells resulted in a significant reduction in cell viability and an increase in cell death rates. In vivo systemic administration studies in mice further revealed that Y4 effectively inhibits the growth of human lung cancer xenografts as well as the metastasis of murine breast cancer. Furthermore, this study provides evidence confirming that the cytotoxic effects mediated by Y4 involve a dual mechanism: direct killing of cancer cells themselves, as well as indirect killing mechanisms dependent on the immune system. This research highlights that antibody-based therapeutic strategies targeting KCNK9 hold great promise as a highly prospective treatment modality for malignant tumors that express this channel.

The time-dependent characteristics exhibited by the channel inhibition mediated by Y4 suggested an antibody-induced endocytic mechanism. To verify this possibility, researchers employed flow cytometry. They co-incubated hKCNK9-overexpressing HEK293 cells with Y-series monoclonal antibodies (Y-mAbs) at 30°C for 12 hours, and subsequently stained the channels remaining on the cell surface (Figure 1a). Flow cytometry analysis revealed that, within the KCNK9-positive cell population, 15.6% of the cells completely lost their cell-surface signal, thereby converting to a KCNK9-negative status; meanwhile, in the remaining cells that retained their KCNK9-positive status, the overall fluorescence intensity decreased by 25.7%. This reduction in cell-surface KCNK9 levels was observed exclusively following treatment with the Y4 antibody, whereas no such change was detected in cells treated with other Y-series monoclonal antibodies (Figure 1b-d). To conduct a more in-depth analysis, the researchers utilized confocal microscopy to track fluorescently labeled Y4 antibodies. The results demonstrated that fluorescent labeling of the Y4 antibody did not alter its binding affinity for its target (Figure 1h). During the incubation period-and specifically under temperature conditions permissive for endocytosis-the researchers observed a phenomenon characterized by a progressive attenuation of the cell-surface signal accompanied by a concomitant intensification of the intracellular signal (with the intracellular signal predominantly localized to the perinuclear region). These data suggest that the monoclonal antibody-induced endocytosis of functional cell-surface channels may constitute one of the mechanisms underlying the reduction in channel conductance observed in ion influx assays.

Figure 1. Y4 reduced the number of hKCNK9 channels expressed on cell surface. (Sun, Han, et al., 2016)