title: PIK3CA mutation is an oncogenic aberration at advanced stages of oral squamous cell carcinoma.
abstract: Phosphatidylinositol 3-kinases (PI3K) are a group of heterodimeric lipid kinases that regulate many cellular processes. Gene amplification and somatic mutations mainly within the helical (exon 9) and kinase (exon 20) domains of PIK3CA, which encode the 110-kDa catalytic subunit of PI3K and are mapped to 3q26, have been reported in various human cancers. Herein, 14 human oral squamous cell carcinoma (OSCC) cell lines and 108 primary OSCC tumors were investigated for activating mutations at exons 9 and 20 as well as amplifications in PIK3CA. PIK3CA missense mutations in exons 9 and 20 were identified in 21.4% (3/14) of OSCC cell lines and 7.4% (8/108) of OSCC tumors by genomic DNA sequencing. An increase in the copy number of PIK3CA, although small, was detected in 57.1% (8/14) of OSCC lines and 16.7% (18/108) of OSCC tumors using quantitative real-time PCR. A significant correlation between somatic mutations of PIK3CA and disease stage was observed: the frequency of mutations was higher in stage IV (16.1%, 5/31) than in a subset of early stages (stages I-III) (3.9%, 3/77; P = 0.042, Fisher's extract test). In contrast, the amplification of PIK3CA was observed at a similar frequency among all stages. AKT was highly phosphorylated in OSCC cell lines with PIK3CA mutations compared to those without mutations, despite the amplification. The results suggest that somatic mutations of the PIK3CA gene are likely to occur late in the development of OSCC, and play a crucial role through the PI3K-AKT signaling pathway in cancer progression.
authors.affiliation: Department of Genome Medicine, Graduate School, Tokyo Medical and Dental University, 1-5-45 Yushima Bunkyo-ku, Tokyo 113-8510, Japan.
authors.forename: Ken-ichi
authors.initials: K
authors.lastname: Kozaki
authors.forename: Issei
authors.initials: I
authors.lastname: Imoto
authors.forename: Atiphan
authors.initials: A
authors.lastname: Pimkhaokham
authors.forename: Shogo
authors.initials: S
authors.lastname: Hasegawa
authors.forename: Hitoshi
authors.initials: H
authors.lastname: Tsuda
authors.forename: Ken
authors.initials: K
authors.lastname: Omura
authors.forename: Johji
authors.initials: J
authors.lastname: Inazawa
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D017209:Apoptosis / Q000187:drug effects; D014408:Biomarkers, Tumor / Q000235:genetics; D015153:Blotting, Western; D002294:Carcinoma, Squamous Cell / Q000235:genetics* / Q000378:metabolism / Q000556:secondary; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D058534:Class I Phosphatidylinositol 3-Kinases; D004252:DNA Mutational Analysis; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D005784:Gene Amplification; D006801:Humans; D008297:Male; D008875:Middle Aged; D009062:Mouth Neoplasms / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D020125:Mutation, Missense / Q000235:genetics*; D019869:Phosphatidylinositol 3-Kinases / Q000235:genetics* / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt / Q000235:genetics / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction; D014062:Tongue Neoplasms / Q000235:genetics
chemical_list: D014408:Biomarkers, Tumor; D004791:Enzyme Inhibitors; D019869:Phosphatidylinositol 3-Kinases; D058534:Class I Phosphatidylinositol 3-Kinases; C484760:PIK3CA protein, human; C494918:AKT1 protein, human; D051057:Proto-Oncogene Proteins c-akt