The BRAF inhibitor
PLX4032 is effective in treating BRAF-mutated
melanoma; however, because drug resistance develops in most cases, it is critical to develop a new strategy for inhibiting
drug-resistant
melanoma growth. The
melanoma-associated
membrane glycoprotein CD63 is involved in cell proliferation and
metastasis. Here, we found that cell surface CD63 suppresses the proliferation of human
melanoma cells and PLX4032-resistant cells. Endogenous CD63
protein levels were negatively correlated with
PLX4032 resistance of human
melanoma cell lines. CD63 overexpression in these cells, in which endogenous CD63 levels are low, suppressed cell proliferation under
PLX4032 treatment. The cell surface levels and average molecular mass of CD63 were increased with
PLX4032 treatment because of the up-regulated
polylactosamine modification caused by induced β1,3-
N-acetylglucosaminyltransferase 2 expression, which is involved in
polylactosamine synthesis. Forced cell surface localization of CD63 led to reduced
melanoma cell proliferation without
PLX4032 treatment. CD63 overexpression in PLX4032-resistant cells, in which CD63 levels were lower and cell surface
polylactosamine levels were higher than those in parental cells, effectively suppressed proliferation. Our study shows the potential of CD63 to sensitize
melanoma cells to
PLX4032 and to reduce the proliferation of PLX4032-resistant cells.-Kudo, K., Yoneda, A., Sakiyama, D., Kojima, K., Miyaji, T., Yamazaki, M., Yaita, S., Hyodo, T., Satow, R., Fukami, K. Cell surface CD63 increased by up-regulated
polylactosamine modification sensitizes human
melanoma cells to the BRAF inhibitor
PLX4032.