Time-Dependent Effects of Cisplatin on Autophagy Gene Expression in Bladder Cancer Cells

Background/Objectives: Bladder cancer treatment is frequently hindered by chemoresistance to agents such as cisplatin, a process in which autophagy is hypothesized to play a cytoprotective role. This study aimed to investigate the time-dependent transcriptional dynamics of autophagy-related genes in response to cisplatin in bladder cancer cell lines to better elucidate the molecular underpinnings of this resistance. Methods: Two human bladder cancer cell lines, T24 and 5637, were exposed to varying concentrations of cisplatin. Cell viability and half-maximal inhibitory concentration (IC₅₀) values were determined at 24 and 48 h using the MTS assay. Subsequently, the relative mRNA expression levels of key autophagy-related genes (ULK1, BECN1, ATG5, ATG7, LC3B, SQSTM1/p62, LAMP1, and TFEB) were quantitatively analyzed via RT-qPCR at 0, 6, 24, and 48 h intervals. Results: Cisplatin exerted a dose- and time-dependent cytotoxic effect, with 5637 cells exhibiting significantly greater sensitivity compared to T24 cells. Transcriptional analysis revealed a dynamic, multiphasic modulation of the autophagic pathway: an early-phase upregulation of initiation genes (ULK1, BECN1), a mid-phase increase in autophagosome formation genes (ATG5, ATG7), and a late-phase alteration in lysosomal regulation genes (LAMP1, TFEB). Notably, the more chemoresistant T24 cells mounted a robust and sustained autophagic transcriptional response, whereas the sensitive 5637 cells demonstrated a more limited and transient reaction. Conclusions: Cisplatin modulates the autophagic pathway at the transcriptional level in a highly dynamic, time-dependent, and cell-line-specific manner. Interpreted alongside established functional evidence in the literature, the sustained autophagic gene expression observed in the resistant cells is consistent with a potential cytoprotective role, warranting further functional validation at the protein level. These findings map the temporal genetic landscape of cisplatin-induced autophagy, providing a theoretical framework for optimizing the timing of autophagy-targeted combination therapies in bladder cancer.