Evaluating the impact reduced FBXO30 expression has on chromosome instability in colonic epithelial cell lines

Abstract

Colorectal cancer (CRC) is the fourth most commonly diagnosed and second most lethal cancer in Canada. While there are effective screening programs and therapeutic options, individuals are often diagnosed with CRC at late disease stages. Despite the high morbidity and mortality rates facing Canadians, the underlying mechanisms driving CRC pathogenesis remain poorly understood. Chromosome instability (CIN), is an ongoing phenomenon defined by the increased changes in chromosome complements and occurs in ~85 % of all CRC cases. Recent evidence from the McManus laboratory demonstrates that decreased expression of core SKP1-CUL1-F-box (SCF) E3 ubiquitin ligase complex members induce CIN and promote early CRC development. However, the role of the variable 69 F-box protein subunits in driving CIN remains largely unknown. Therefore, this thesis examines the impact of reduced FBXO30 expression on CIN in early CRC development. Quantitative imaging microscopy techniques coupled with siRNA-based silencing were used to assess CIN-associated phenotypes, including changes in nuclear areas, micronucleus formation, and chromosome numbers in karyotypically stable non-malignant and malignant colonic epithelial cell lines. As a result, reduced FBXO30 expression induced significant changes (increases and/or decreases) in nuclear areas, micronucleus formation, and chromosome numbers in non-malignant, non-transformed 1CT and A1309 cell lines. Additionally, in the malignant context, FBXO30 silencing induced significant increases in nuclear areas and aberrant chromosome numbers in HCT116 cells. Collectively, these data identify FBXO30 as a novel CIN gene and may provide novel insights into the etiological events promoting CRC pathogenesis.