Inhibition of T-type Ca2+channels by endostatin attenuates human glioblastoma cell proliferation and migration

BACKGROUND AND PURPOSE Endostatin (ES) is a c-terminal proteolytic fragment of collagen XVIII with promising antitumour properties in several tumour models, including human glioblastoma. We hypothesized that this peptide could interact with plasma membrane ion channels and modulate their functions. EXPERIMENTAL APPROACH Using cell proliferation and migration assays, patch clamp and Western blot analysis, we studied the effects of ES on the proliferation and migration of human glioblastoma U87 cells, mediated by T-type Ca2+ channels. KEY RESULTS Extracellular application of ES reversibly inhibited T-type Ca2+ channel currents (T-currents) in U87 cells, whereas L-type Ca2+ currents were not affected. This inhibitory effect was associated with a hyperpolarizing shift in the voltage-dependence of inactivation but was independent of G-protein and protein tyrosine kinase-mediated pathways. All three a1 subunits of T-type Ca2+ channels (CaV3), a1G (CaV3.1), a1H (CaV3.2) and a1I (CaV3.3), were endogenously expressed in U87 cells. Using transfected HEK293 or CHO cells, we showed that only CaV3.1 and CaV3.2, but not CaV3.3 or CaV1.2 (L-type), channel currents were significantly inhibited. More interestingly, ES inhibited the proliferation and migration of U87 cells in a dose-dependent manner. Pretreatment of the cells with the specific T-type Ca2+ channel blocker mibefradil occluded these inhibitory effects of ES. CONCLUSION AND IMPLICATIONS This study provides the first evidence that the antitumour effects of ES on glioblastoma cells is through direct inhibition of T-type Ca2+ channels and gives new insights into the future development of a new class of antiglioblastoma agents that target the proliferation and migration of these cells. LINKED ARTICLE This article is commented on by Santoni et al., pp. 12441246 of this issue. To view this commentary visit