Found 1 Presentation For Request "33P"
33P - Synergistic effects of Alpelisib (PI3K inhibitor) and Ribociclib (CDK 4/6 inhibitor) in preclinical colorectal cancer (CRC) models
- Razia Aslam (Dublin, Ireland)
- Razia Aslam (Dublin, Ireland)
- Sinead Toomey (Dublin, Ireland)
- Bryan Hennessy (Dublin, Ireland)
Abstract
Background
Multiple activating genetic mutations in the phosphatidylinositol-3 kinase (PI3K) and the mitogen activated protein kinase (MAPK) pathways have been implicated in the development of resistance to anti-cancer therapies. Ribociclib has limited activity as a single agent in CRC. However, combining Ribociclib with targeted therapies of the MAPK and PI3K pathways may be a promising treatment strategy in CRC.
Methods
We explored the in vitro efficacy of drug combinations (Ribociclib and Alpelisib (R+A)) in four CRC cell lines with different mutational statuses; CACO-2 (PIK3CA/KRAS wildtype), LS-1034 (KRAS mutated), SNU-C4 (PIK3CA mutated), and DLD-1 (PIK3CA/KRAS mutated). The drug combination index (CI) was calculated by using Calcusyn Biosoft software. A western immunoblotting method was used for protein analysis.
Results
IC50s for R and A were calculated for all four cell lines. CACO2 and DLD-1 cells were resistant to R (IC50 >15μM). The cell lines had varying sensitivity to both drugs. Drug combination analysis showed that the combination of R+A has a synergistic anti-proliferative effect in all CRC cell lines tested. The combination of R+A is highly synergistic in LS1034 cells which harbor a KRAS mutation (CI=0.16). Relative expression of the proteins Cyclin D1, E2F-1, p-BCL-2, p-AKT, p-Rb, and p-S6 was determined by measuring the density of each band and normalizing to β-actin. We demonstrated that combined inhibition of CDK4/6 and PI3Kα caused a simultaneous reduction of p-RB, p-AKT, and p-S6 and a more complete inhibition of the PI3K/AKT/mTOR pathway in all four cell lines. There was a marginal increment in the apoptotic marker (pBCL-2), possibly due to the shorter duration of treatment (24 hours).
Cell lines Molecular features Ribociclib (R) IC50 Alpelisib (A) IC50 Drug combination doses R+A Combination Index CI ED50 SNUC4 PIK3CA E545G 0.259μM 0.4413μM 2μM+400nM 0.54 LS1034 KRAS A146T 1.126μM 0.3134μM 2μM+400nM 0.16 DLD1 KRAS G13D/PIK3CA E545K >15 μM 1.307μM 2μM +3μM 0.78 CACO2 Wild type >15 μM 1.547μM 5μM+2μM 0.28
Conclusions
A synergistic response to treatment with the combination of R+A is seen in all cell lines. We are currently investigating this combination in CRC animal models.
Legal entity responsible for the study
The authors.
Funding
RCSI Dublin and Hermitage Hospital Dublin.
Disclosure
All authors have declared no conflicts of interest.