KRAS inhibition impacts chromatin organization and transcriptional performance in colorectal cancer cells [LS174T RNA-seq]

Preclinical and clinical data revealed that targeting KRAS mutant tumors is more challenging than expected. While initially sensitive to the treatment, cancer cells have the capability to rapidly bypass dependence on this oncogene to acquire a drug-tolerant phenotype. Gaining a comprehensive understanding of the mechanisms underlying the transition from a drug-sensitive to a drug-tolerant state holds the key to invaluable insights. Such insights will inform the development of therapeutic strategies aimed at disrupting intrinsic or adaptive resilience, ultimately enhancing therapeutic outcomes. Building upon this rationale, we established three-dimensional culture models of mutant KRAS CRC cell lines with distinct KRAS dependencies to investigate the cellular response to KRAS silencing. Our approach revealed a unique response in KRAS-dependent cells, characterized by G0/G1 cell cycle arrest and entry into a quiescent-like state. Proteomics analysis identified nucleosome assembly, regulation of gene expression, mRNA splicing, and mRNA processing as the top biologic processes specifically up-regulated in KRAS-dependent CRC cell lines upon KRAS silencing. Additionally, alterations in histone 3 post-translational modifications and chromatin compaction were also observed, along with enhanced transcriptional performance revealed by longitudinal RNA-Seq analysis. Our discoveries substantiate the existence of an epigenetic mechanism responsible for inducing tolerance to KRAS loss. This mechanism relies on both chromatin reorganization and transcriptional upregulation, illuminating the cancer cells' remarkable capacity to swiftly adapt, survive, and sustain malignancy even in the absence of oncogenic KRAS. To investigate the effect of KRAS inhibition in transcription dynamics os colorectal cancer cell lines, we used 3 different KRAS mutant colorectal cancer cell lines (HCT116, LS174T and SW480). We then silenced cells using siRNA and performed gene expression profilling analysis using data obtained from RNA-seq of the different cell lines at four different-time points from silenced cells (siKRAS) or its control (siControl).