Effect And Molecular Mechanism Of Thiothymidine On A375 Cell

Malignant melanoma is a malignant tumor derived from normal melanocytes or the original mole cells of the skin.The current therapy for malignant melanoma has the deficiency of poor targeting and almost has no effect for middle and terminal stage cancer.The current therapy using photosensitizer plus UVA radiation has shown many advantages,such as high targeting,high selection and low toxicity.Thiothymidine combined with UVA radiation has been demonstrated a highly targeted destruction to many tumor cells and their tissues.In this study,the effect and possible molecular mechanism of S4TdR/UVA on human malignant tumor cells will be investigated.In vitro human malignant melanoma cell line A3 75 and human immortal keratinocyte cell line HaCat were used to study the influence of S4TdR/UVA on cell viability and cell cycle.The possible apoptotic mechanism induced by S4TdR/UVA was identified by quantitative analysis of relative molecules in P53 and CHOP pathways.Our results demonstrated 10-5 and 10-6M S4TdR synergistic with UVA could significantly reduce the cell viability of A375 cells,but almost had no effect on HaCat.10-5 M UVA/S4TdR could lead to a significant G,phase cell cycle arrest in A3 75 cells and the cell cycle proliferation index is only 2.86%,indicating a strong prolifaration inhibition.Quantitative analysis of mRNA and protein indicated that S4TdR/UVA could increase the expression of p53 in A375 cells.The increased p53 could activate two downstream pathways:(1)The up-regulating of p21 induced an inhibition on G1/S transition and thus led to cell prolifaration inhibition;(2)Caspase-3 was activated by up-regulating of bax/bcl-2 ratio and led to cell apoptosis.Further investigation demonstrated S4TdR/UVA could also activate stress respond proteins,like ATF6,IRE1 and PERK,and induce cell apoptosis by up-regulating chop expression and activation the CHOP/GADD153 pathway.Our data provided in this study first addressed the potential therapeutic effects of S4TdR/UVA on malignant melanoma.