Glutamate-mediated signaling pathway regulates the invasion and growth of malignant melanoma

Abstract

Objective To investigate the action mechanism of glutamate-mediated signaling pathway in malignant melanoma. Methods WM451LU melanoma cells in log phase were classified into 6 groups, negative control group treated with PBS (100 μl), MK801 group treated with the non-competitive N-methyl-D-aspartate (NMDA) receptor antagonist MK-801 (100 μmol/L), CPCCOEt group treated with non-competitive metabotropic glutamate receptor 1 (mGluR1) antagonist CPCCOEt, MAP2 group transfected with adenovirus vector containing microtubule associated protein 2a (Ad-MAP2a), MK801 + MAP2 group treated with MK801 of 100 μmol/L and transfected with Ad-MAP2a, CPCCOEt + MAP2 group treated with CPCCOEt of 10 μmol/L and transfected with Ad-MAP2a. Western blot was performed to detect the expression of an ionotropic glutamate receptor, i.e., N-methyl-D-aspartate receptor type 2A (NMDAR2A) in WM451LU cells transfected with Ad-MAP2a. Scratch motility assay and cell invasion assay were conducted in vitro to detect the changes in migration and invasion ability of WM451LU cells after treated with Ad-MAP2a, MK-801, CPCCOEt alone or in combination. In vivo study was carried out to compare the inhibitory effect of the above treatments on melanoma. Results Western blot revealed a decrease in the expression of NMDAR2A in WM451LU cells after transfected with Ad-MAP2a. The scratch motility assay showed that the number of migrating cells per high power field was 117.04 ± 2.76 in MAP2 group,107.64 ± 6.50 in MK801 group,97.36 ± 4.79 in CPCCOEt group, 43.28 ± 3.02 in MK801 + MAP2 group,30.76 ± 3.97 in CPCCOEt + MAP2 group,significantly different from that in the negative control group (152.3 ± 5.75,all P ＜ 0.01 ). Cell invasion assay demonstrated that the average number of invading cells per high power field in the negative control was significantly higher than that in MAP2 group, MK801 group, CPCCOEt group, MK801+MAP2 group and CPCCOEt + MAP2 group (170.43 ±8.72 vs. 98.26 ± 3.84, 97.22 ± 5.54, 112.23 ± 7.21, 42.89 ± 5.06, 58.25 ± 6.68, P ＜ 0.05, 0.05, 0.05, 0.01and 0.01, respectively).A significant decrease was observed in the average volume of experimental melanoma in mice of MAP2 group, MK801 group, MK801 + MAP2 group, CPCCOEt group and CPCCOEt + MAP2 group compared with the negative control group (224.02 ± 46.19 mm3, 160.33 ± 33.91 mm3, 91.49 ± 21.48 mm3,202.30 ± 52.37 mm3, 111.13 ± 69.81 mm3 vs. 342.70 ± 60.92 mm3, all P ＜ 0.01 ). Conclusions To block the glutamate signaling pathway in vitro can inhibit the invasion and migration of melanoma cells, and to block the pathway in vivo can inhibit the growth of malignant melanoma and alter the morphology of melanoma cells. Key words: Melanoma, experimental; Cell line, tumor; Receptors, metabotropic glutamate; Microtubule proteins; Cell movement