[K-ras gene mutation in colorectal cancer and its clinicopathologic significance].
OBJECTIVE
To establish a simple, rapid and economical method in detecting mutations of oncogene K-ras and to investigate its mutations in colorectal cancer tissues and its relationship with clinicopathologic characteristics of colorectal carcinoma.


METHODS
Forty colorectal cancer tissues were tested for K-ras mutations at codon 12 and codon 13 using polymerase chain reaction (PCR) followed by direct sequencing and polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) followed by sequence analysis. The other 113 colorectal cancer tissues were tested for K-ras mutations at codon 12 and codon 13 using PCR-RFLP followed by sequence analysis only. The mutation results were analyzed with the corresponding clinical pathological data.


RESULTS
Among 40 colorectal cancer cases, none of K-ras mutations at codon 12 and codon 13 was detected by PCR followed by direct sequencing. However, K-ras mutations were found in 11 cases (11/40, 27.5%) by PCR-RFLP followed by sequence analysis, including 8 cases at codon 12 and 3 cases at codon 13 respectively. Among 153 colorectal cancer cases, point mutations were detected by PCR-RFLP followed by sequence analysis in 58 cases (37.9%). Point mutations at codon 12 were found in 46 cases and 12 cases at codon 13. Mutations with the highest frequency were G→A transitions (25/58, 43.1%) at codon 12. No significant correlation was observed between mutations of K-ras and gender, invasive depth, tumor differentiation, number of invaded lymph nodes, distant metastasis and clinical stage (P > 0.05). Mutation of oncogene K-ras at codon 12 and codon 13 was closely related with age and tumor location (P < 0.05). The incidence of K-ras mutation was significantly higher in younger patients and in patients with ascending colon cancer.


CONCLUSIONS
PCR-RFLP followed by sequence analysis is a rapid, simple, sensitive and low-cost method. It is a suitable technology for detecting hot-spot mutations in the K-ras oncogene. Mutation of oncogene K-ras at codon 12 and codon 13 is a common molecular event in colorectal carcinogenesis, which might be related with age and tumor location.
Department of Oncology, the Second Hospital of Zhejiang University College of Medicine, Hangzhou, China.
Ying
Y
Yuan
Han-guang
HG
Hu
Xiao-xian
XX
Ye
Hong
H
Shen
Shu
S
Zheng
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015179:Colorectal Neoplasms / Q000235:genetics* / Q000473:pathology; D005260:Female; D011905:Genes, ras / Q000235:genetics*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009154:Mutation; D012150:Polymorphism, Restriction Fragment Length