[Screening for mutations in the hotspot mutation regions of PIK3CA gene in nasopharyngeal carcinoma].
OBJECTIVE
Recent studies showed high frequency of phosphatidylinositol 3-kinase catalytic alpha polypeptide (PIK3CA) mutations in various human cancers; notably, these mutations frequently locate in the hotspot mutation regions of PIK3CA exon 9 and exon 20 with functional significance in tumorigenesis, invasion, and anti-apoptosis. This study was to screen for mutations in the hotspot mutation regions of PIK3CA in nasopharyngeal carcinoma (NPC), and explore the correlation of PIK3CA mutations to tumorigenesis of NPC.


METHODS
PIK3CA exon 9 and exon 20 in 46 specimens of sporadic primary NPC tissues were screened by polymerase chain reaction (PCR)-clone sequencing; those in 46 samples of matched NPC peripheral blood and 3 NPC cell lines CNE1, CNE2, and SUNE1 were directly sequenced.


RESULTS
Among the 46 specimens of NPC, 2 (4.3%) had point mutation in PIK3CA exon 9 [T1563G (521Asn-->Lys) and A1646G (549Asp-->Gly)], 18 had multiple mutations in PIK3CA exon 9 (A1634C-G1658C-del 1659T), which might be the homologous sequence of Cat Eye Syndrome region on 22q11.2; none had mutation in PIK3CA exon 20. Moreover, no mutation was detected in PIK3CA exon 9 and exon 20 in the 46 matched NPC peripheral blood samples and CNE1, CNE2, and SUNE1 cells.


CONCLUSIONS
PIK3CA exon 9 and exon 20 rarely mutate in NPC. Clone sequencing is more sensitive than direct sequencing in screening for somatic mutation. A1634C-G1658C-del 1659T mutations in PIK3CA exon 9, detected by clone sequencing, are supposed to be the homologous sequence of Cat Eye Syndrome region on 22q11.2 instead of mutations in PIK3CA.
Liu
Peng
P
State Key Laboratory of Oncology in South China, Guangzhou, Guangdong, 510060, P. R. China.
Li
Da-Jiang
DJ
Qin
Hai-De
HD
Zhang
Ru-Hua
RH
Chen
Li-Zhen
LZ
Zeng
Yi-Xin
YX
D001483:Base Sequence; D002294:Carcinoma, Squamous Cell / Q000235:genetics*; D002892:Chromosomes, Human, Pair 22; D058534:Class I Phosphatidylinositol 3-Kinases; D004252:DNA Mutational Analysis; D004273:DNA, Neoplasm / Q000235:genetics; D005091:Exons / Q000235:genetics*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D008969:Molecular Sequence Data; D009154:Mutation; D009303:Nasopharyngeal Neoplasms / Q000235:genetics*; D019869:Phosphatidylinositol 3-Kinases / Q000235:genetics*; D016133:Polymerase Chain Reaction
D004273:DNA, Neoplasm; D019869:Phosphatidylinositol 3-Kinases; D058534:Class I Phosphatidylinositol 3-Kinases; C484760:PIK3CA protein, human