PIK3CA mutation in colorectal cancer: relationship with genetic and epigenetic alterations.
Somatic PIK3CA mutations are often present in colorectal cancer. Mutant PIK3CA activates AKT signaling, which up-regulates fatty acid synthase (FASN). Microsatellite instability (MSI) and CpG island methylator phenotype (CIMP) are important molecular classifiers in colorectal cancer. However, the relationship between PIK3CA mutation, MSI and CIMP remains uncertain. Using Pyrosequencing technology, we detected PIK3CA mutations in 91 (15%) of 590 population-based colorectal cancers. To determine CIMP status, we quantified DNA methylation in eight CIMP-specific promoters [CACNA1G, CDKN2A (p16), CRABP1, IGF2, MLH1, NEUROG1, RUNX3, and SOCS1] by real-time polymerase chain reaction (MethyLight). PIK3CA mutation was significantly associated with mucinous tumors [P = .0002; odds ratio (OR) = 2.44], KRAS mutation (P < .0001; OR = 2.68), CIMP-high (P = .03; OR = 2.08), phospho-ribosomal protein S6 expression (P = .002; OR = 2.19), and FASN expression (P = .02; OR = 1.85) and inversely with p53 expression (P = .01; OR = 0.54) and beta-catenin (CTNNB1) alteration (P = .004; OR = 0.43). In addition, PIK3CA G-to-A mutations were associated with MGMT loss (P = .001; OR = 3.24) but not with MGMT promoter methylation. In conclusion, PIK3CA mutation is significantly associated with other key molecular events in colorectal cancer, and MGMT loss likely contributes to the development of PIK3CA G>A mutation. In addition, Pyrosequencing is useful in detecting PIK3CA mutation in archival paraffin tumor tissue. PIK3CA mutational data further emphasize heterogeneity of colorectal cancer at the molecular level.
Nosho
Katsuhiko
K
Department of Medical Oncology, Dana-Farber Cancer Institute, Boston, MA 02115, USA.
Kawasaki
Takako
T
Ohnishi
Mutsuko
M
Suemoto
Yuko
Y
Kirkner
Gregory J
GJ
Zepf
Dimity
D
Yan
Liying
L
Longtine
Janina A
JA
Fuchs
Charles S
CS
Ogino
Shuji
S
D001483:Base Sequence; D058534:Class I Phosphatidylinositol 3-Kinases; D015179:Colorectal Neoplasms / Q000235:genetics* / Q000473:pathology; D019175:DNA Methylation; D015254:DNA Modification Methylases / Q000235:genetics; D004252:DNA Mutational Analysis; D045643:DNA Repair Enzymes / Q000235:genetics; D044127:Epigenesis, Genetic; D005091:Exons; D005260:Female; D006801:Humans; D008957:Models, Genetic; D008969:Molecular Sequence Data; D009154:Mutation; D019869:Phosphatidylinositol 3-Kinases / Q000235:genetics* / Q000502:physiology*; D011518:Proto-Oncogene Proteins / Q000235:genetics; D048493:Proto-Oncogene Proteins B-raf / Q000235:genetics; D016283:Proto-Oncogene Proteins p21(ras); D025521:Tumor Suppressor Proteins / Q000235:genetics; D018631:ras Proteins / Q000235:genetics
C117307:KRAS protein, human; D011518:Proto-Oncogene Proteins; D025521:Tumor Suppressor Proteins; D015254:DNA Modification Methylases; C515491:MGMT protein, human; D019869:Phosphatidylinositol 3-Kinases; D058534:Class I Phosphatidylinositol 3-Kinases; C484760:PIK3CA protein, human; C482119:BRAF protein, human; D048493:Proto-Oncogene Proteins B-raf; D016283:Proto-Oncogene Proteins p21(ras); D018631:ras Proteins; D045643:DNA Repair Enzymes