Evaluating the impact reduced RBX1 expression has on chromosome instability and colorectal cancer

Abstract

Colorectal cancer (CRC) was ranked the fourth most commonly diagnosed cancer type and third leading cause of death in Canada in 2025. Although CRC is associated with high morbidity and mortality rates, the molecular mechanisms driving CRC development remain poorly understood. Therefore, understanding aberrant genetic and molecular mechanisms driving CRC development is crucial for the development of novel therapeutic strategies that can ultimately improve prognosis and survival of CRC patients. Chromosome instability (CIN) is a predominant genome instability in CRC, and it is defined by the increase of rate in which whole chromosomes or chromosome fragments are gained or lost and are a known driver of ongoing cell-to-cell heterogeneity. CIN is associated with ~85% of CRC cases and is suggested to be a driver of CRC pathogenesis. Previous studies have identified RBX1, a core member of the SCF complex, as a strong CIN gene candidate as its reduced expression resulted in increases in nuclear areas relative to non-targeting control. RBX1 encodes a core member of the SCF complex that ubiquitinates proteins for proteolytic degradation via the 26S proteasome; however, the role of RBX1 in inducing CIN in CRC remains to be elucidated. Therefore, this study evaluated the effect of reduced RBX1 expression on CIN and early CRC development. Short-term siRNA approaches coupled with quantitative imaging microscopy techniques were employed to assess changes in CIN-associated phenotypes. Analysis showed that reduced RBX1 expression corresponded with increases in CIN phenotypes (significant changes to nuclear areas, micronucleus formation, and chromosome numbers) in both non-malignant colonic epithelial and CRC cell lines relative to non- targeting control. Collectively, our findings identify RBX1 as a novel CIN gene and may provide new insights into the molecular origins and pathogenic events in CRC.