摘要目的 回顾性分析中国结直肠癌患者中 KRAS与BRAF基因突变特征及其与临床病理学的关系.方法 收集结直肠癌病例557例,其中结肠癌325例,直肠癌232例.采用PCR-DNA直接测序法检测557例中 KRAS基因第2号外显子突变和197例中BRAF基因第15号外显子突变,分析基因突变特征及与其临床病理特征的的相关性.结果 (1)结直肠癌患者中 KRAS基因突变率为40.4％(225/557),常见突变位点是第12位密码子(79.1％,178/225)和第13 位密码子(20.4％,46/225);常见突变类型为第12位密码子GGT＞GAT(G12D)、GGT＞GTT(G12V)和第13密码子GGC＞ GAC(G13D),分别占 KRAS总突变的37.8％(85/225)、20.0％(45/225)和19.6％ (44/225),3者约占总突变的77.3％(174/225).未检测到KRAS基因不同密码子同时突变的病例.(2)557例结直肠癌患者中,女性KRAS基因突变率(46.2％,92/199)明显高于男性(37.2％,133/358;P＜0.05).KRAS基因第13位密码子突变在右半结肠(11.3％,12/106)高于左半结肠(4.8％,6/124),但差异无统计学意义(P＞0.05).(3)结直肠癌BRAF基因突变率为5.1％ (10/197),主要为第600位密码子GTG＞ GAG突变(V600E,8/10),8例GTG＞ GAG(V600E)的结直肠癌中未同时检测到KRAS基因突变.第600位密码子GTG＞ATG(V600M)和第606位密码子GGG＞ AGT(G606S)突变各1例,均同时伴KRAS基因第2号外显子第12位密码子突变.(4)女性BRAF(V600E)基因突变率(8.5％,6/71)高于男性患者(1.6％,2/126),差异接近有统计学意义(P=0.05);结肠癌(8.3％,6/72)高于直肠癌(2.1％,2/94),右半结肠癌9.7％(3/31)略高于左半结肠癌7.3％(3/41),但差异均无统计学意义(均P＞0.05) 结论 (1)KRAS基因第12、13 位密码子及BRAF基因第600 位密码子是中国人结直肠癌最常见的突变位点,KRAS不同类型突变、KRAS与 BRAF V600E突变均不同时发生,是独立的分子事件;(2)结直肠癌中 KRAS、BRAF (V600E)基因突变率女性明显高于男性,提示RAS-RAF-MAPK信号通路可能直接或间接与性激素相关;(3)KRAS基因第13 位密码子和BRAF基因突变在右半结肠癌有高于左半结肠癌的趋势,但尚需更多病例证实.

abstractsObjection To retrospectively analyze KRAS and BRAF gene mutation features in Chinese colorectal cancer(CRC) and their clinicopathologic relationship.Methods 557 colorectal cancer eases were collected,including 325 colon cancer and 232 rectal cancer.PCR amplification and DNA sequencing were used to detect mutations in exon 2 of KRAS gene and exon 15 of BRAF gene mutation.Results (1) KRAS mutation was found in 40.4％ (225/557) colorectal cancer.The most common mutation locations were in codon 12 (79.1％,178/225) and codon 13 (20.4％,46/225).The most common mutation types were GGT ＞ GAT(G12D) (37.8％,85/225),GGT ＞ GTT (G12V) (20.0％,45/225) in codon 12 and GGC ＞ GAC(G13D) in codon 13 (19.6％,44/225).These three point mutations accounted 77.3％ (174/225) in total KRAS gene mutation cases.All cases showed only one of point mutation types.(2) Among 557 CRC cases,KRAS mutation was significantly higher in female (46.2％,92/199) than in man(37.2％,133/358; P ＜ 0.05).KRAS gene codon 13 mutation was higher in right colon cancer (11.3％,12/106) than that in left colon cancer (4.8％,6/124),but it didn't show any statistical significance(P ＞ 0.05).(3)BRAF gene mutation was 5.1％ (10/197) in colorectal cancer and 8/10 were the point mutation of GTG ＞ GAG(V600E).Eight colorectal cancer cases with GTG ＞ GAC(V600E) were not showing KRAS gene mutation.Both two cases with mutation on codon 600 (GTG ＞ ATG,V600M) and codon 606(GGG ＞ AGT,G606S) showed codon 12 mutation of KRAS gene.(4) BRAF(V600E) gene mutation was higher in female(8.5％,6/71) than that in male(1.6％,2/126; P =0.05) ; BRAF mutation in colon cancer(8.3％,6/72) was higher than that in rectum cancer(2.1％,2/94),but hadn't statistical significance(P ＞ 0.05).Conclusions (1) Codon 12,13 in KRAS gene and codon 600 in BRAF gene are the most common mutation points in Chinese colorectal cancer.KRAS and BRAF mutations are mutually exclusive.(2) KRAS and BRAF gene mutation is higher in female than that in male,suggesting that RAS-RAF-MAPK signal pathway is probably related to hormones directly or indirectly.(3) There is a trend that codon 13 mutation in KRAS and codon 600 mutation in BRAF in right colon cancer are higher than that in left colon cancer,respectively,however,which needs more cases to be further verified.