Abstract 2636: The H1047R point mutation in PI3KCA changes morphology in human colon cancer cells.

INTRODUCTION: The PI3K signaling pathway involves a wide range of cell signaling phenomena, including cell proliferation, differentiation, angiogenesis, survival, adhesion, cytoskeletal rearrangement, invadopodia formation and motility. Mutations in the catalytic subunit p110α (PIK3CA) of Class 1A phosphatidyinositol 3-kinase (PI3K) occur in up to 1/3 of human colorectal cancers (CRC). The kinase domain mutation H1047R is the most frequent cancer-specific mutation in p110α and results in a gain of function. In vivo studies have demonstrated that cell lines bearing the p110α mutation are more metastatic than the cells with wild type p110α. We have previously shown that inhibition of PI3K-p110α significantly delayed or abrogated the migration of HCT116 parental cell line, which is a CRC cell line that is heterozygous for the PIK3CA mutation and thus contains both the H1047R mutation in p110α and a wild type allele of PIK3CA. The aim of our study was to investigate the mechanism of how the H1047R mutation of PI3K results in the increased cell motility in HCT116 cell line. We hypothesize that the rearrangement of the cytoskeleton may be responsible for the changes in cell morphology and cell motility in the presence of the H1047R mutation of PI3K. METHODS: HCT116 cells engineered to contain either the H1047R mutant (MUT) or wild type (WT) PI3KCA allele were used in this study. Cell morphology was observed by microscopic approaches and F-actin, the major component of cytoskeleton, was stained with Alexa Fluor® 488 Phalloidin. Effect of PI3K-p110α inhibition on cell morphology was tested at a series of time points with 1.0 μM of A66 and PIK75, which are specific inhibitors of p110α. RESULTS: The morphological appearance of MUT cells was considerably different as compared to WT cells. The WT HCT116 cells normally show a rounded and more clumped morphology. However, the MUT HCT116 cells become elongated and actin filaments appear to align along the length of the cell. The cells also adopt less clumped and more fibroblastic morphology. Furthermore, when the MUT cells were treated with the p110α specific inhibitors, the cell morphology then again resembled the WT cells. The morphological changes in MUT HCT116 cells possibly contribute to enhanced migratory capacity. CONCLUSION: The morphologic appearance of MUT PIK3CA bearing colon cancer cells is markedly different from WT cells. The inhibition of mutant PIK3CA function results in morphologic changes that resemble the WT allele bearing cells. Thus, the interaction of PI3K and the cell cytoskeleton appears to be an important aspect in regulating cell motility and subsequently, metastases. The PI3K pathway remains a desirable target in CRC therapeutics. Citation Format: Guanghua Wan, Essence Hand, Judy Lin Cannon, Ashwani Rajput. The H1047R point mutation in PI3KCA changes morphology in human colon cancer cells. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 2636. doi:10.1158/1538-7445.AM2013-2636