Colorectal cancer (CRC) is the third most commonly diagnosed cancer in males and the second in females. In Australia, there is a 5-year overall survival rate of 13% for stage IV CRC, the main reason being the development of resistance to treatment.
The presence of PIK3CA (phosphoinositide 3-kinase catalytic subunit alpha) mutations being in up to 30% of CRC, prompted the development of novel targeted therapies. Initially, PI3K (Phosphoinositide 3-kinases) inhibitors presented an increase of the progression-free survival rate. However, drug resistance finally led to treatment failure.
This study will help to elucidate de novo resistance mechanisms to PI3K inhibitors through genome-scale Knock Out CRISPR-Cas9 screening, using a specific PIK3CA inhibitor, Alpelisib. We used a CRC cell line (LIM2551) with high sensitivity to Alpelisib to identify candidate gene knock outs that generate resistance to Alpelisib. In contrast, we used another CRC cell line (HCT116) with low sensitivity to Alpelisib to identify candidates that when knocked out increase the efficacy of Alpelisib.
Interestingly, the gene knock out results so far show a change in drug sensitivity in several cellular pathways and processes including: the mTOR pathway (PTEN, TSC2, NPRL2 and DEPDC5), the glycolysis pathway (PGP and ENO1), the pentose phosphate pathway (PGD), mitochondrial function (PET117, NDUFA1, NDUFA9, NDUFS1, COA6 and COX17), protein translation (DPH1, DNAJC24, EIF4A1, DPH6 and DPH5), and the cytoskeleton and cell migration (MYH9, LIMK2 and ROCK2).Finally, other top candidate hits present ambiguous connections such as RALGAPB, KCTD5 and LCMT1.
Upon functional validation, the most promising targets will be used to test combinational therapy together with Alpelisib to find new treatments to overcome resistance to PI3K inhibitors in CRC.