Riok1, A Novel Potential Target in MSI-High p53 Mutant Colorectal Cancer Cells

Abstract

The vulnerabilities of cancer cells constitute a promising strategy for drug therapeutics. This paper integrates proteomics, bioinformatics, and cell genotype together with in vitro cell proliferation assays to identify key biological processes and potential novel kinases that could account, at least in part, for the clinical differences observed in colorectal cancer (CRC) patients. This study started by focusing on CRC cell lines stratified by their microsatellite (MS) state and p53 genotype. It shows that cell-cycle checkpoint, metabolism of proteins and RNA, signal transduction, and WNT signaling processes are significantly more active in MSI-High p53-WT cell lines. Conversely, MSI-High cell lines with a mutant (Mut) p53 gene showed hyperactivation of cell signaling, DNA repair, and immune-system processes. Several kinases were linked to these phenotypes, from which RIOK1 was selected for additional exploration. We also included the KRAS genotype in our analysis. Our results showed that RIOK1’s inhibition in CRC MSI-High cell lines was dependent on both the p53 and KRAS genotypes. Explicitly, Nintedanib showed relatively low cytotoxicity in MSI-High with both mutant p53 and KRAS (HCT-15) but no inhibition in p53 and KRAS WT (SW48) MSI-High cells. This trend was flipped in CRC MSI-High bearing opposite p53-KRAS genotypes (e.g., p53-Mut KRAS-WT or p53-WT KRAS-Mut), where observed cytotoxicity was more extensive compared to the p53-KRAS WT-WT or Mut-Mut cells, with HCT 116 (KRAS-Mut and p53-WT) being the most sensitive to RIOK1 inhibition. These results highlight the potential of our in silico computational approach to identify novel kinases in CRC sub-MSI-High populations as well as the importance of clinical genomics in determining drug potency.

The RioK1 network determines p53 activity at multiple levels

“…However, this compound might also target other kinases, including RioK3 [65], but experimental evidence in this regard remains lacking. Recently, Nintedanib, a tyrosine kinase inhibitor approved for use in idiopathic pulmonary fibrosis, also targeted RioK1 in colorectal cancer cells [66]. More desirable precision approaches could involve developing ligands that target the post-translational modifications of RioK1 (p-S407, p-T410, met-K411), which determine its activity and stability.…”

“…These could be combined with compounds that disrupt the MDM2-p53 interaction [56] or that target RioK1 to enhance the stability of re-activated mutant p53, similar to inhibiting RioK1 in cancer cells expressing wild-type p53 [2]. Recent reports revealed that genetically downregulating or drug (Nintedanib) treating RioK1 abrogated the growth and proliferation of malignancies expressing gain-of-function mutant p53 [15,66]. However, considering that neither p53 stability nor activity was probed, and given that RioK1 mediates myriad roles in cells, while Nintedanib does not target RioK1 exclusively, it cannot be excluded that secondary activities were aspecifically affected in both studies, causing the observed cytotoxicities.…”