Transcriptomic analysis reveals differential adaptation of colorectal cancer cells to low and acute doses of cisplatin.

Over the years, the landscape of cisplatin-based cancer treatment options has undergone continuous transitions. Currently, there is much debate over the optimum dose of cisplatin to be administered to cancer patients. In clinical practice, it can extend from repeated low sub-toxic doses to a few cycles of acute high drug doses. Herein, the molecular understanding of the overall cellular response to such differential doses of cisplatin becomes crucial before any decision making; and it has been a grey area of research. In this study, colorectal cancer (CRC) cells were treated with either- a low sub-toxic dose (LD; 30 µM) or a ten times higher acute dose (HD; 300 µM) of cisplatin, and thereafter, the cellular response was mapped through RNA sequencing followed by transcriptomic analysis. Interestingly, we observed that the tumor cells' response to varying doses of cisplatin is distinctly different, and they activate unique transcriptional programs. The analysis of differentially regulated or uniquely expressed transcripts and corresponding pathways revealed a preferential enrichment of genes associated with chromatin organization, oxidative stress, senescence-associated signaling, and developmentally-active signaling pathways in HD; whereas, modulation of autophagy, protein homeostasis, or differential expression of ABC transporters was primarily enriched in LD. This study is the first of its kind to highlight cellular transcriptomic adaptations to different doses of cisplatin in CRC cells. Consequently, since, protein homeostasis was found to be deeply affected after cisplatin treatment, we further analyzed one of the primary cellular protein homeostatic mechanisms- autophagy. It was activated upon LD, but not HD, and served as a pro-survival strategy through the regulation of oxidative stress. Inhibition of autophagy improved sensitivity to LD. Overall, our study provides a holistic understanding of the distinct molecular signatures induced in CRC cells in response to differential cisplatin doses. These findings might facilitate the design of tailored therapy or appropriate drug dose for enhanced efficacy against CRCs.