Mutant KRAS-Associated Proteome Is Mainly Controlled by Exogenous Factors

Understanding how mutant KRAS signaling is modulated by exogenous stimuli is of utmost importance to elucidate resistance mechanisms underlying pathway inhibition failure, and to uncover novel therapeutic targets for mutant KRAS patients. Hence, aiming at perceiving KRAS-autonomous versus -non autonomous mechanisms, we studied the response of two mutant KRAS colorectal cancer cell lines (HCT116 and LS174T) upon KRAS silencing and treatment with rhTGF beta 1-activated fibroblasts secretome. A proteomic analysis revealed that rhTGF beta 1-activated fibroblast-secreted factors triggered cell line-specific proteome alterations and that mutant KRAS governs 43% and 38% of these alterations in HCT116 and LS174T cells, respectively. These KRAS-dependent proteins were localized and displayed molecular functions that were common to both cell lines (e.g., extracellular exosome, RNA binding functions). Moreover, 67% and 78% of the KRAS-associated proteome of HCT116 and LS174T cells, respectively, was controlled in a KRAS-non-autonomous manner, being dependent on fibroblast-secreted factors. In HCT116 cells, KRAS-non-autonomously controlled proteins were mainly involved in proteoglycans in cancer, p53, and Rap1 signaling pathways; whereas in LS174T cells, they were associated with substrate adhesion-dependent cell-spreading and involved in metabolic processes. This work highlights the context-dependency of KRAS-associated signaling and reinforces the importance of integrating the tumor microenvironment in the study of KRAS-associated effects.

Automated summary

Understanding how external stimuli modulate mutant KRAS signaling is crucial for uncovering resistance mechanisms and therapeutic targets in mutant KRAS patients. This study found that factors secreted by rhTGF beta 1-activated fibroblasts triggered cell-specific proteome alterations in mutant KRAS colorectal cancer cell lines. Mutant KRAS was shown to govern a significant portion of these alterations, while a substantial portion was controlled by fibroblast-secreted factors. The study highlights the context-dependent nature of KRAS signaling and emphasizes the importance of considering the tumor microenvironment in KRAS-related effects.