Abstract:

Objective To investigate the effects of HINT1 on the growth of and apoptosis in malignant melanoma in nude mouse models established by subcutaneous xenotransplantation of human melanoma A375 cells. Methods Three groups of nude mice were subcutaneously inoculated with A375 cells transfected with pcDNA 3.1/myc-His（-） A-HINT1 （HINT1-A375）, A375 cells transfected with pcDNA 3.1/myc-His（-） A empty vector（neo-A375）, and untransfected A375 cells, respectively. Then, the growth of transplanted tumors was observed and tumor formation rate was calculated. Thirty-three days after the inoculation, mice were killed and tumor tissue was obtained followed by the examination of tumor weight and volume. Histopathology was performed to observe the morphological features of tumor cells and in situ end labeling technique （TUNEL） was carried out to assess the apoptosis in transplanted tumor cells. Results The tumor formation rate was consistently 100% in the three groups. The transplanted tumor in HINT1 group grew more slowly than that in the other two groups, and significant difference was observed as early as day 18（P < 0.01）. Lower tumor weight and volume were noted in the HINT1 group compared with the neo group and A375 cell group （0.04 ± 0.00 g vs. 0.23 ± 0.00 g and 0.29 ± 0.03 g, 0.06 ± 0.04 cm3 vs. 0.34 ± 0.15 cm3 and 0.43 ± 0.19 cm3 respectively, all P < 0.01）. Histopathology revealed smaller tumor nests, slight atypia of tumor cells with no obvious pathologic mitoses or necrosis in HINT1 group in comparison with the other two groups. Immunohistochemistry and TUNEL revealed that the percentage of apoptotic cells in HINT1 group was statistically higher than that in the neo group and A375 cell group（12.87% ± 1.18% vs. 3.22% ± 0.49% and 3.00% ± 0.53%, both P < 0.01）. Conclusion High expression of HINT1 could inhibit the growth of and promote the apoptosis in malignant melanoma in nude mice subcutaneous xenotransplantation models, suggesting that HINT1 gene might be responsible for tumor suppression in human malignant melanoma.

Key words: HINT1