Abstract 1274: Investigation into the influence of the H1047R PIK3CA mutation on the bioenergetic dependency of a cell
Authors: Foster Rebecca , Rigby Sue , Christopherson Cindy , Sninsky John , Kwok Shirley , Torrance Chris 
Published: June 2012

Background: During tumorigenesis, cells acquire mutations that confer selective advantages for growth. These mutations may reprogram cellular metabolism to meet the requirements of rapid proliferation and survival in an environment of fluctuating and scarce nutrients. Phosphoinositide-3-kinases (PI3Ks) play key roles in fundamental cellular processes and are frequently mutated in a broad range of cancers. The aim of this study was to investigate how a single endogenous activating mutation in PI3K, H1047R, affects the metabolic programming of human breast epithelial cells.

Methods: We utilized X-MAN isogenic cells derived from MCF10a mammary epithelial cells, which harbour a single H1047R PIK3CA mutation introduced via AAV-mediated homologous recombination and compared them to matched parental cells with a wild type (WT) allele. This system allows use of endogenous promoters thereby more accurately recapitulating the genomic architecture in human tumours. Metabolic gene expression profiles were measured by RT-PCR.

Results: We identified a multi-gene expression signature indicative of increased dependency on the glycolytic pathway. Hexokinase 2, which is involved at an early stage of the glycolytic pathway, was strongly up-regulated along with the lactate transporters MCT1 and 4. The fructose transporter GLUT5 was nearly undetectable in H1047R PIK3CA cells, suggesting a strong preference for glucose and elevated levels of aerobic glycolysis. PI3K mutant cells also down-regulated genes in the pentose phosphate pathway-shunt, tricarboxylic acid cycle and glutaminolysis pathways, indicating that aerobic glycolysis is heavily favoured. Treatment with the PI3K inhibitor GDC-0941 led to a general reversal of gene expression for these pathways, confirming the PI3K specificity of these metabolic alterations.

We proceeded to investigate growth dependence of the H1047R PIK3CA and parental MCF10a cells on various nutrient sources (e.g. glucose, fructose, galactose and glutamine). While the growth rates of cells WT for PIK3CA were not significantly affected by glucose withdrawal and nutrient replacement, growth of mutant PIK3CA cells was dramatically compromised in the absence of glucose, revealing a specific dependency for this nutrient as an energy substrate. Consistent with PI3K activation mediating glucose dependency, treatment of H1047R PIK3CA cells with GDC-0941 promoted growth of the cells under low or no glucose conditions.

Conclusion: Isogenic cells WT for PIK3CA are capable of utilizing a range of nutrient sources, while cells harboring H1047R PIK3CA appear hard-wired to exclusively utilize glucose. These data suggest that targeting glucose transporters or glycolytic enzymes may be a powerful therapeutic strategy for mutant PI3K-cancers. The overt glucose dependence of cells with this mutation may also offer routes to non-invasively image PI3K-pathway activated tumors.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 1274. doi:10.1158/1538-7445.AM2011-1274