Synergistic Effects of the Combination of Alpelisib (PI3K Inhibitor) and Ribociclib (CDK4/6 Inhibitor) in Preclinical Colorectal Cancer Models
Razia Aslam, Cathy E. Richards, Joanna Fay, Lance Hudson, Julie Workman, Cha Len Lee, Adrian Murphy, Brian Patrick O’Neill, Sinéad Toomey, Bryan T. Hennessy
Abstract
The CDK4/6 inhibitor Ribociclib has shown limited efficacy as a monotherapy in colorectal cancer (CRC). However, combining Ribociclib with targeted therapies could present a viable strategy for treating CRC. This study evaluated the combination of Ribociclib and the PI3K inhibitor Alpelisib across four distinct cell lines representing different mutational statuses (PIK3CA/KRAS wild-type, KRAS-mutated, PIK3CA-mutated, and PIK3CA/KRAS-mutated). We analyzed the drugs’ impact on key proteins involved in the PI3K pathway, cell cycle regulation, and apoptosis. The combination of Alpelisib and Ribociclib demonstrated a synergistic anti-proliferative effect across all cell lines, leading to a simultaneous decrease in pRB, pAKT, and p-S6 levels, and a more comprehensive suppression of the PI3K/AKT/mTOR pathway. Additionally, there was an upregulation of the apoptotic marker, p-BCL2, in cells treated with the combination compared to controls. In vivo studies using Caco-2, LS1034, and SNUC4 xenografts revealed a significant reduction in tumour growth with the combination therapy compared to single-agent treatments. These findings suggest that combining Alpelisib and Ribociclib could be a promising therapeutic approach for CRC, warranting further clinical exploration.