title: Colon carcinoma cells harboring PIK3CA mutations display resistance to growth factor deprivation induced apoptosis.
abstract: PIK3CA, encoding the p110alpha catalytic subunit of phosphatidylinositol 3-kinase (PI3K), is mutated in a variety of human cancers. We screened the colon cancer cell lines previously established in our laboratory for PIK3CA mutations and found that four of them harbored gain of function mutations. We have now compared a panel of mutant and wild-type cell lines for cell proliferation and survival in response to stress. There was little difference in PI3K activity between mutant PIK3CA-bearing cells (mutant cells) and wild-type PIK3CA-bearing cells (wild-type cells) under optimal growth conditions. However, the mutant cells showed constitutive PI3K activity during growth factor deprivation stress (GFDS), whereas PI3K activity decayed rapidly in the wild-type cells. Importantly, constitutively active PI3K rendered the mutant cells resistant to GFDS-induced apoptosis relative to the wild-type cells, indicating a biological advantage under stress conditions that is imparted by the mutant enzymes. Compared with the wild-type cells, the mutant cells were hypersensitive to the apoptosis induced by the PI3K inhibitor LY294002. In addition, PIK3CA small interfering RNA significantly decreased DNA synthesis and/or induced apoptosis in the mutant cells but not in the wild-type cells. Furthermore, ecotopic expression of a mutant PIK3CA in a nontumorigenic PIK3CA wild-type cell line resulted in resistance to GFDS-induced apoptosis, whereas transfection of wild-type PIK3CA or empty vector had little effect. Taken together, our studies show that mutant PIK3CA increases the capacity for proliferation and survival under environmental stresses, such as GFDS while also imparting greater dependency on the PI3K pathway for proliferation and survival.
authors.affiliation: Department of Pharmacology and Therapeutics, Roswell Park Center Institute, Elm and Carlton Streets, Buffalo, NY 14263, USA.
authors.forename: Jing
authors.initials: J
authors.lastname: Wang
authors.forename: Karen
authors.initials: K
authors.lastname: Kuropatwinski
authors.forename: Jennie
authors.initials: J
authors.lastname: Hauser
authors.forename: Michael R
authors.initials: MR
authors.lastname: Rossi
authors.forename: Yunfei
authors.initials: Y
authors.lastname: Zhou
authors.forename: Alexis
authors.initials: A
authors.lastname: Conway
authors.forename: Julie L C
authors.initials: JL
authors.lastname: Kan
authors.forename: Neil W
authors.initials: NW
authors.lastname: Gibson
authors.forename: James K V
authors.initials: JK
authors.lastname: Willson
authors.forename: John K
authors.initials: JK
authors.lastname: Cowell
authors.forename: Michael G
authors.initials: MG
authors.lastname: Brattain
mesh_terms: D017209:Apoptosis / Q000187:drug effects*; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D058534:Class I Phosphatidylinositol 3-Kinases; D003110:Colonic Neoplasms / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D019008:Drug Resistance, Neoplasm; D006133:Growth Substances / Q000172:deficiency*; D006801:Humans; D009154:Mutation / Q000235:genetics*; D019869:Phosphatidylinositol 3-Kinases / Q000235:genetics* / Q000378:metabolism; D000081082:Phosphoinositide-3 Kinase Inhibitors; D016133:Polymerase Chain Reaction; D015398:Signal Transduction / Q000187:drug effects; D014162:Transfection
chemical_list: D058534:Class I Phosphatidylinositol 3-Kinases; D006133:Growth Substances; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; C484760:PIK3CA protein, human