Transcription network of SLC7A11 (xCT) in colon cancer provides clinical targets for metabolic regulation and cell proliferation
Colorectal cancer (CRC) represents the third leading cause of cancer-related deaths. Knowledge covering diverse cellular and molecular data from individual patients has become valuable for diagnosis, prognosis, and treatment selection. Here, we present in-depth comparative RNA-seq analysis of 32 CRC patients pairing tumor and healthy tissues (total of 73 samples). Strict thresholds for differential expression genes (DEG) analysis revealed an interconnection between nutrients, metabolic program, and cell cycle pathways. Among the upregulated DEGs, we focused on the Xc- system, composed of the proteins from SLC7A11 (xCT) and SLC3A2 genes, along with several interacting genes. To assess the oncogenic potency of the Xc- system in a cellular setting, we applied a knowledge-based approach, analyzing gene perturbations from CRISPR screens. The study focused on a set of 27 co-dependent genes that were strongly correlated with the fitness of SLC7A11 and SLC3A2 across many cell types. Alterations in these genes in 13 large-scale studies (e.g., by mutations and copy number variation) were found to enhance overall survival and progression-free survival in CRC patients. In agreement, the overexpression of these genes in cancer cells drives cancer progression by allowing effective management of the redox level, induction of stress response mechanisms, and most notably, enhanced activity of ion/amino acid transporters, and enzymes acting in de novo nucleotide synthesis. We also highlight the positive correlation between the Xc- system gene expression level, patient responsiveness to different chemotherapy treatments, and immune cell infiltration (e.g., myeloid-derived suppressor cells) in CRC tumors as a measure for their immunosuppressive activity. This study illustrates that knowledge-based interpretation by synthesizing multiple layers of data leads to functional and mechanistic insights into the role of SLC7A11 and its associated genes in CRC tumorigenesis and therapeutics.