The Timeless (TIM) and it's interacting partner TIPIN
protein complex is well known for its role in replication checkpoints and normal DNA replication processes. Recent studies revealed the involvement of TIM and TIPIN in human
malignancies; however, no evidence is available regarding the expression of the TIM/TIPIN
protein complex or its potential role in
melanoma. Therefore, we investigated the role of this complex in
melanoma. To assess the role of the TIM/TIPIN complex in
melanoma, we analyzed TIM/TIPIN expression data from the publicly accessible TCGA online database, Western blot analysis, and RT-qPCR in a panel of
melanoma cell lines. Lentivirus-mediated TIM/TIPIN knockdown in A375
melanoma cells was used to examine proliferation, colony formation, and apoptosis. A xenograft
tumor formation assay was also performed. The TIM/TIPIN complex is frequently overexpressed in
melanoma cells compared to normal melanocytes. We also discovered that the overexpression of TIM and TIPIN was significantly associated with poorer prognosis of
melanoma patients. Furthermore, we observed that
shRNA-mediated knockdown of TIM and TIPIN reduced cell viability and proliferation due to the induction of apoptosis and increased levels of γH2AX, a marker of DNA damage. In a xenograft
tumor nude mouse model,
shRNA-knockdown of TIM/TIPIN significantly reduced
tumor growth. Our results suggest that the TIM/TIPIN complex plays an important role in
tumorigenesis of
melanoma, which might reveal novel approaches for the development of new
melanoma therapies. Our studies also provide a beginning structural basis for understanding the assembly of the TIM/TIPIN complex. Further mechanistic investigations are needed to determine the complex's potential as a
biomarker of
melanoma susceptibility. Targeting TIM/TIPIN might be a potential therapeutic strategy against
melanoma.