Poster Presentation 30th Lorne Cancer Conference 2018

Investigating the metabolic reprogramming resulting from a single knock-in PIK3CAH1047R mutation in cancer (#129)

Sabrina Caiazzo 1 , Lorey Smith 1 , Camilla Mitchell 1 , Wayne Phillips 1
  1. Peter MacCallum Cancer Centre, Melbourne, VIC, Australia

The phosphoinositide 3-kinase (PI3K) pathway is one of the most commonly activated pathways in human cancers. Somatic mutations in the helical (E542 and E545) and kinase (H1047) domain of PIK3CA promote cellular transformation. Growing interest in cancer metabolism has highlighted the PI3K/AKT pathway as one of the primary modulators of cellular metabolism in tumour cells. This has opened promises and challenges for the development of therapeutic strategies to target metabolism in cancer cells harbouring mutations in the PIK3CA gene. To better understand the role of the PIK3CAH1047R mutation in cancer cell metabolism, we utilised our novel mouse model where the H1047R mutation is conditionally knocked into the endogenous PIK3CA gene, resulting in expression at physiological levels. Combining studies on enzymatic activity and lactate production assays with the Seahorse XF Flux Analyzer, we investigated changes in metabolism following the PIK3CAH1047R mutation in mouse embryonic fibroblasts (MEFs) isolated from the above described mice. We observed changes in metabolism associated with an increased glycolytic phenotype. MEFs harbouring the PIK3CA mutation have greater proton extraction rate and extracellular acidification rate, compared with the control MEFs. In agreement with this, mutant MEFs extrude lactate at a higher rate than the control, suggesting that most of the glucose taken by the cells with the PIK3CAH1047R mutation is converted to lactate (“the Warburg effect”). Despite a change in the glycolytic rate, the oxygen consumption rate and the activity of pyruvate dehydrogenase complex, the major regulator of oxidative function, are not affected by the PIK3CAH1047R mutation, suggesting the mutation does not alter the mitochondrial respiratory capacity of the MEFs. We have also performed preliminary Extracellular Flux Analyses, using the Seahorse Technology, in 3D intestinal epithelial organoids culture, generated from the PIK3CAH1047R mouse, which will aid in understanding metabolic reprogramming in colorectal cancer. Our analyses highlight the phenotypic changes in metabolism, resulting from a single mutation in the PIK3CA gene, as a marker for oncogenic transformation and potential therapeutic target for the treatment of PIK3CA mutated cancers.