结直肠癌患者KRAS和BRAF基因突变检测及其临床意义

目的探讨结直肠癌患者组织中KRAS和BRAF基因突变情况,分析突变与临床病理特征的关系。方法应用荧光PCR-优化寡核苷酸探针法检测304例结直肠癌石蜡包埋标本中KRAS基因2号外显子的12和13密码子、BRAF基因的15号外显子的突变情况,分析KRAS和BRAF基因突变与临床病理特征的关系。结果 KRAS和BRAF基因在结直肠癌的突变率分别为38.8%(118/304)和4.3%(13/304)。KRAS基因突变阳性标本中12密码子的突变率为78.0%,其中p.G12D发生率最高,占总突变的45.3%;13密码子的突变率为22.0%。高年龄组(≥60岁)患者的KRAS基因突变率为47.2%(58/123),高于低年龄组(<60岁)的33.1%(60/181),差异有统计学意义(P<0.05)。转移性结直肠癌患者19例,其KRAS基因突变率为36.8%(7/19),与285例原发性结直肠癌患者的突变率(38.9%,111/285)差异无统计学意义(P>0.05)。BRAF基因在结肠、低分化、黏液腺癌患者中的突变率明显高于直肠、中或高分化和管状腺癌的患者。结论结直肠癌患者中KRAS基因突变的发生率较高,与年龄相关,而与性别、部位、病理类型和分化程度不相关。BRAF基因突变与肿瘤部位、病理类型和分化程度有关。原发性与转移性结直肠癌患者KRAS基因突变率无明显差异。     

肺腺癌患者EGFR和KRAS基因突变与预后的相关性研究

目的 探讨肺腺癌患者表皮生长因子受体(EGFR)和KRAS基因突变与预后的相关性.方法 选取134例肺腺癌患者的肺腺癌组织标本,应用探针扩增阻滞突变系统在PCR仪上进行EGFR和KRAS基因突变检测,分析EGFR和KRAS基因突变与肺腺癌患者临床病理特征及预后的关系.结果 134例患者中,EGFR基因突变53例,突变率为39.55%,KRAS基因突变6例,突变率为4.48%.肺腺癌患者EGFR基因突变率与年龄、吸烟史有关(P﹤0.01).EGFR基因突变型患者的KRAS基因突变率低于EGFR基因野生型患者(P﹤0.05).EGFR基因突变型患者的无进展生存期(PFS)长于EGFR基因野生型患者(P﹤0.05),KRAS基因野生型患者的PFS长于KRAS基因突变型患者(P﹤0.05).结论 EGFR基因突变的肺腺癌患者KRAS基因更倾向于野生型,EGFR基因突变型或KRAS基因野生型的肺腺癌患者PFS更长.     

结直肠癌组织中KRAS和BRAF基因突变与临床病理特征及预后的关系

目的:探讨结直肠癌组织中KRAS和BRAF基因突变与临床病理和预后的关系。方法:采用扩增阻滞突变系统（ARMS）方法对134例结直肠癌组织进行回顾性分析。结果:134例CRC组织中KRAS基因突变率49.3%（66/134）,第2外显子突变率42.5%（57/134）,其中12及13密码子突变率分别为35.1%（47/134）和7.5%（10/134）,第3外显子61密码子突变率1.5%（2/134）,第4外显子117/146密码子突变率5.2%（7/134）,BRAF V600E突变率4.5%（6/134）。左半结肠KRAS基因突变率54.5%（54/99）高于右半结肠34.3%（12/35）,差异有统计学意义（P＜0.05）,右半结肠BRAF基因突变率14.3%（5/35）高于左半结肠1.0%（1/99）,差异有统计学意义（P＜0.05）,而KRAS和BRAF基因突变与性别、年龄、民族、肿块大小、分化程度、淋巴结转移及病理分期等临床病理特征,差异均无统计学意义（P＞0.05）。KRAS基因突变型CRC患者的中位生存时间48个月（39.9%）,与野生型47个月（46.2%）相比较,差异无统计学意义（P＞0.05）。BRAF基因突变型CRC患者的中位生存时间21个月（26.7%）,与野生型48个月（44.7%）相比较,差异有统计学意义（P＜0.05）。多因素COX回归风险模型结果显示,BRAF基因突变型是CRC患者预后不良的独立危险因素（B=1.664,OR=5.278,95%CI:1.505~18.516, P＜0.05）,而性别、年龄、民族、肿块大小、分化程度、肿瘤部位、淋巴结转移及病理分期均不是CRC患者生存时间的独立危险因素（P＞0.05）。结论:CRC组织中KRAS基因突变率高,BRAF基因突变率低。KRAS和BRAF基因突变型与肿瘤部位有关。BRAF基因突变型是CRC预后不良的独立危险因素。     

云南地区结直肠癌患者RAS/BRAF/PIK3CA基因突变状态及与临床病理特征的关系

目的:本研究主要对结直肠癌患者的KRAS/NRAS/BRAF V600E/PIK3CA基因突变情况及与临床病理特征的关系进行探究。方法:我们对2018年01月至2020年01月在我院分子诊断中心进行基因检测的结直肠癌患者的KRAS/NRAS/BRAF V600E/PIK3CA突变情况进行回顾性分析,共纳入209例具有完整临床信息的患者,所有患者的基因检测都是采用高通量测序方法获得的,并对患者的人口统计学和临床信息进行分析。结果:209例结直肠癌患者中,KRAS、NRAS、BRAF V600E、PIK3CA突变例数分别为98例、7例、10例和25例,突变率分别为46.9%、3.3%、4.8%和12.0%。KRAS 2号外显子突变最常见,其中又以G12D亚型突变高发,肿瘤原发部位在直肠的患者和微卫星稳定的CRC患者KRAS突变率明显高于原发部位在左右半结肠和微卫星不稳定的患者(P<0.05);BRAF V600E在MSI-H的CRC患者中突变率显著高于MSS的患者(P<0.05);男性患者、既往没有吸烟史、有淋巴结转移、临床分期较早以及MSI-H的CRC患者有更高的PIK3CA...     

原发性肝癌中 KRAS 及 BRAF 基因突变及其临床意义

目的：检测原发性肝癌患者血浆中的 KRAS 与 BRAF 基因突变机率及特征,研究与疾病进展的相关性及对治疗的意义。方法：收集肝癌患者血液（51例）,观察组25例,为肝癌伴肝外转移患者;对照组26例,为病灶局限于肝脏的肝癌患者。所有的患者抽取外周血10ml,从血样中游离 DNA,采用人类 KRAS ／NRAS 基因突变联合检测试剂盒及人类 BRAF 基因 V600E 突变检测试剂盒分别对 KRAS 基因和 BRAF 基因突变进行检测,并分析基因突变机率及与其突变特征。结果：51例肝癌患者中,伴肝外转移患者 KRAS 基因突变率（24％,6／25）明显高于无肝外转移患者 KRAS 基因突变率（0％,0／26;P ＜0．05）;肝癌患者中 BRAF 基因突变率为0％（0／51）。结论：本研究表明肝癌患者 KRAS 基因会发生明显的突变,且肝癌伴肝外转移患者,KRAS基因突变频率明显增加。未检测出 BRAF 基因突变或 BRAF 基因突变率较低。     

430例中国非小细胞肺癌患者EGFR、KRAS、BRAF和PIK3CA基因突变状态及其临床意义

目的： 探讨非小细胞肺癌（non-small cell lung cancers,NSCLC）患者表皮生长因子受体（epidermal growth factor receptor, EGFR）信号通路中EGFR、Kirsten鼠肉瘤病毒癌基因(Kirsten rat sarcoma viral oncogene homolog, KRAS)、B-Raf原癌基因丝氨酸/苏氨酸蛋白激酶(B-Raf proto oncogene serine/threonine protein kinase,BRAF)和磷脂酰肌醇-3-激酶α亚单位(phosphatidylinositol -4,5- bisphosphate 3-kinase catalytic subunit alpha,PI3KCA)基因的突变状态及其临床意义,为酪氨酸酶抑制剂（tyrasin kimase inhibitor, TKI)临床用药与科学研究提供依据。方法：采用SurPlex-xTAG70plex液相芯片技术平台检测中国430例NSCLC患者的福尔马林固定石蜡包埋(formalin fixed paraffin embedded, FFPE)组织中EGFR、KRAS、BRAF和PIK3CA基因的突变状态,分析基因的突变率及其与临床病理特征的关系。结果： EGFR、KRAS、BRAF和PIK3CA的突变率分别为41.2%,79%,0.7%和3.7%。EGFR外显子19、21在女性患者中的突变率明显高于男性（P<0.01）, 在肺腺癌患者中的突变率明显高于其他类型肺癌（P<0.01）,在无吸烟史患者中的突变率高于有吸烟史的患者（P<0.01）。相反地,KRAS突变在男性患者中的突变率高于女性（P<0.05）,在肺腺癌中的突变率高于肺鳞癌（P<0.005）,有吸烟史患者的突变率高于无吸烟史患者（P<0.01）。在肺腺癌患者中PIK3CA的突变率明显低于其他类型肺癌（P<0.01）。结论： EGFR和KRAS基因突变率与性别、组织学类型及吸烟史密切相关。在检测中发现EGFR和KRAS双突变,此外PIK3CA突变并非与EGFR和KRAS突变互斥。     

甲状腺乳头状癌BRAF V600E、NRAS、TERT基因的突变特征及其与临床病理特征的相关性

目的:探索甲状腺乳头状癌(papillary thyroid carcinoma,PTC)三种驱动基因BRAF V600E、NRAS和TERT基因突变与临床病理特征的相关性,旨在为甲状腺癌患者提供更精准的分子分型检测指导。方法:纳入2018年01月至2018年12月期间空军军医大学西京医院收治的接受BRAF V600E、NRAS、TERT三基因检测的PTC患者,回顾性收集患者的临床病理特征和三种基因突变状态资料,分析各基因的突变特点及其与临床病理特征的相关性。结果:本研究347例患者,BRAF V600E、TERT、NRAS基因突变率分别为89.3%、2.0%以及1.2%。TERT和NRAS基因的患者同时发现有BRAF V600E基因突变。BRAF V600E/NRAS或BRAF V600E/TERT双基因突变率为3.2%。双基因突变患者多发病灶占72.7%,病理分型非PTMC占72.7%,淋巴结转移率为81.8%。BRAF V600E/NRAS双基因突变患者均发现淋巴结转移,BRAF V600E/TERT双基因突变患者有71.4%（5/7）出现淋巴结转移。单因素分析结果显示,年龄、病灶数量、病灶位置以及淋巴结转移与基因突变相关（P均＜0.05）。结论:BRAF V600E基因在PTC中的突变率达89.3%,TERT、NRAS基因突变往往与BRAF V600E基因突变同时出现,双基因突变可能与PTC侵袭性相关。     

结直肠癌组织基因突变、微卫星不稳定与患者临床病理特征的相关性

目的探讨结直肠癌组织KRAS、NRAS、BRAF基因突变及微卫星不稳定(MSI)的发生情况, 及其与患者临床病理特征的相关性。方法回顾性分析山西省肿瘤医院2020年10月至2021年5月诊治的473例结直肠癌患者临床病理资料。应用扩增阻滞突变系统(ARMS)法检测石蜡包埋组织中KRAS、NRAS、BRAF基因突变情况, 应用聚合酶链反应-毛细管电泳法分析MSI状态, 并分析患者临床病理特征与基因突变及MSI状态的相关性。结果 473例结直肠癌组织中KRAS、NRAS和BRAF基因突变率分别为45.03%(213/473)、2.96%(14/473)和5.50%(26/473), 未检出两种基因共突变患者。高/中分化腺癌中KRAS基因突变率高于低分化腺癌[47.4%(175/369)比36.5%(38/104), χ2=3.89, P=0.049]。女性NRAS基因突变率高于男性[5.0%(10/202)比1.5%(4/271), χ2=4.86, P=0.027];肿瘤长径≤3 cm者NRAS基因突变率高于肿瘤长径>3 cm者[7.1%(7/98)比1.9%(7/375), P=...     

江苏地区肺癌和胃癌患者 KRAS 基因突变状态分析*

目的:检测江苏地区肺癌和胃癌患者KRAS基因突变状态及其与临床病理特征的关系,并比较其在两种癌症间的异同。方法:收集肺癌128 例,胃癌115 例。采用直接测序法检测KRAS基因第2 号外显子突变,分析基因突变状态及其与临床病理特征的相关性。结果:KRAS基因突变率在肺癌和胃癌中无显著性差异（6.3% vs. 4.3% ,P > 0.05）。 两种癌症中,KRAS 基因突变都以第12密码子为主。KRAS 突变与年龄,性别无明显相关。肺腺癌患者KRAS基因突变高于非腺癌包括鳞癌等（10.7% vs. 0 ,P < 0.05）。 结论:江苏地区肺癌和胃癌患者中,KRAS第2 外显子突变率均较低,男性和女性的突变率无明显差异。肺腺癌患者KRAS基因突变率相对较高,因此个体化治疗前应同时检测KRAS 基因,以筛选出对靶向治疗耐药的肺癌患者,从而更好地指导患者的个体化分子靶向治疗。      

非小细胞肺癌患者RAS基因突变临床特征和预后分析

摘 要：［目的］ 探讨非小细胞肺癌RAS基因突变的临床特征和预后。［方法］ 对475例非小细胞肺癌患者进行RAS基因检测和随访。Kaplan-Meier法计算生存率,Log-rank法进行生存率检验。［结果］ 475例非小细胞肺癌中,KRAS基因突变的突变率为8.00% (38/475),其中吸烟患者的KRAS突变频率远高于非吸烟患者(15.76% vs 4.41%,P<0.01)。 346例非小细胞肺癌中NRAS基因突变的突变率为0.29% (1/346);315例非小细胞肺癌中HRAS基因突变的突变率为0.63% (2/315)。RAS基因复合其他基因突变15例,中位生存时间29.8个月;而单纯RAS突变26例中位生存时间16.3个月(P=0.15)。［结论］ 在NSCLC患者中,吸烟患者的KRAS基因突变频率高于非吸烟患者。RAS基因突变的非小细胞肺癌临床特征上无统计学差异;复合突变比单纯突变临床获益更多。     

Involvement of the serrated neoplasia pathway in inflammatory bowel disease-related colorectal oncogenesis

The purpose of this study is to identify colorectal serrated lesions in the inflammatory mucosa of inflammatory bowel disease (IBD), to characterize their molecular status based on BRAF and KRAS mutations, mismatch-repair (MMR) deficiency and microsatellite instability (MSI), and to verify that these molecular alterations are specific to the 'serrated neoplasia pathway' in IBD. Neoplastic lesions from 36 patients with IBD were reviewed retrospectively, including 13 adenocarcinomas (1 mucinous and 12 conventional), 28 dysplasias [1 traditional serrated adenoma (TSA) and 27 conventional adenomas] and 1 hyperplastic polyp (HP). Both the HP and TSA exhibited the V600E BRAF mutation without MSI or MMR deficiency. The mucinous adenocarcinoma, close to the TSA, exhibited the BRAF mutation and MSI with loss of hMLH1. No KRAS mutations were found in these 3 lesions, and no BRAF mutations were found in the conventional ones. Serrated lesions exist in the inflammatory mucosa of IBD and are associated with a characteristic molecular profile, i.e. the appearance of the BRAF mutation as early as the hyperplastic polyp stage followed by MSI at the carcinoma stage. We therefore identified the serrated neoplasia pathway in IBD-related colorectal oncogenesis.     

Mutations in BRAF and KRAS differentially distinguish serrated versus non-serrated hyperplastic aberrant crypt foci in humans

We previously reported that colon carcinomas, adenomas, and hyperplastic polyps exhibiting a serrated histology were very likely to possess BRAF mutations, whereas when these same advanced colonic lesions exhibited non-serrated histology, they were wild type for BRAF; among hyperplastic polyps, KRAS mutations were found mainly in a non-serrated variant. On this basis, we predicted that hyperplastic aberrant crypt foci (ACF), a putative precancerous lesion found in the colon, exhibiting a serrated phenotype would also harbor BRAF mutations and that non-serrated ACF would not. In contrast, KRAS mutations would be found more often in the non-serrated ACF. We examined 55 ACF collected during screening colonoscopy from a total of 28 patients. Following laser capture microdissection, DNA was isolated, and mutations in BRAF and KRAS were determined by direct PCR sequencing. When hyperplastic lesions were further classified into serrated and non-serrated histologies, there was a strong inverse relationship between BRAF and KRAS mutations: a BRAF(V600E) mutation was identified in 10 of 16 serrated compared with 1 of 33 non-serrated lesions (P = 0.001); conversely, KRAS mutations were present in 3 of 16 serrated compared with 14 of 33 non-serrated lesions. Our finding of a strong association between BRAF mutations and serrated histology in hyperplastic ACF supports the idea that these lesions are an early, sentinel, or a potentially initiating step on the serrated pathway to colorectal carcinoma.     

BRAF and KRAS mutations in colorectal hyperplastic polyps and serrated adenomas

Colorectal cancer is believed to progress through an adenoma-carcinoma sequence. However, recent evidence increasingly supports the existence of an alternative route for colorectal carcinogenesis through serrated polyps, a group that encompasses a morphological spectrum, including hyperplastic polyp (HP), admixed hyperplastic polyp/adenoma (HP/AD), and serrated adenoma (SA; the latter two manifest epithelial dysplasia). We have studied a large series of serrated polyps for BRAF and KRAS mutations. BRAF mutations were detected in 18 of 50 (36%) HPs, 2 of 10 (20%) HP/ADs, and 9 of 9 (100%) SAs. Twenty-six of 29 mutations caused amino acid substitutions at valine 599, the known hotspot. KRAS mutations were detected in 9 of 50 (18%) HPs, 6 of 10 (60%) HP/ADs, and 0 of 9 (0%) SAs. BRAF and KRAS mutations are mutually exclusive (P = 0.001). The associations of BRAF mutations with SAs (P < 0.001) and KRAS mutations with HP/ADs (P = 0.005) are statistically significant. A majority (90%) of the serrated polyps showing dysplasia had mutations in either BRAF or KRAS, significantly different from those without dysplasia (54%; P = 0.014). Our data highlight the important role of activation of the RAS-RAF-mitogen-activated protein/extracellular signal-regulated kinase kinase-extracellular signal-regulated kinase-mitogen-activated protein kinase pathway in the initiation and progression of serrated neoplasms. Acquisition of a BRAF mutation appears to be associated with the progression of HP to SA, whereas progression to HP/AD is predominantly associated with acquisition of a KRAS mutation. The high incidence of BRAF mutations in HPs and SAs is consistent with the notion that the group of colorectal cancers carrying BRAF mutations may harbor most that have progressed through the HP-SA-carcinoma pathway.     

Distinct CpG island methylation profiles and BRAF mutation status in serrated and adenomatous colorectal polyps

A subset of colorectal cancers with CpG island methylator phenotype-high (CIMP-H) is frequently associated with MSI and BRAF V600E mutation. Since limited data are available on different histological types of colorectal polyps, we compared the pattern and the frequency of promoter methylation, CIMP-H, MSI, KRAS and BRAF V600E mutations and the relationship among these molecular parameters and the clinicopathologic characteristics in 110 serrated polyps (48 hyperplastic polyps, 32 sessile serrated adenomas and 30 serrated adenomas) and 32 tubular adenomas using 7 commonly used tumor-associated gene loci. No significant difference in the frequency of overall methylation frequency (86% vs. 100%) and CIMP-H (39% vs. 28%) between serrated polyps and tubular adenomas was observed, but proximally located serrated polyps showed more frequent methylation at 5 of 7 loci examined, and were more likely to be CIMP-H (62% vs. 22%). MGMT methylation was more common in tubular adenomas while MLH1 and HIC1 were more frequently methylated in serrated polyps. BRAF mutation was frequently present in all types of serrated polyps (80%), but was absent in tubular adenomas and was not associated with CIMP or MSI status. These results show comparable frequencies of promoter methylation of tumor-associated genes and CIMP-H, but distinct differences in gene-specific or colonic site-specific methylation profiles occur in serrated polyps and tubular adenomas. BRAF mutation occurs independently of CIMP and MSI in all types of serrated polyps and may serve as a marker of serrated pathway of colorectal carcinogenesis.     

Mutation Analysis of KRAS and BRAF Genes in Metastatic Colorectal Cancer: a First Large Scale Study from Iran

Background: The investigation of mutation patterns in oncogenes potentially can make available a reliable mechanism for management and treatment decisions for patients with colorectal cancer (CRC). This study concerns the rate of KRAS and BRAF genes mutations in Iranian metastatic colorectal cancer (mCRC) patients, as well as associations of genotypes with clinicopathological features. Materials and Methods: A total of 1,000 mCRC specimens collected from 2008 to 2012 that referred to the Mehr Hospital and Partolab center, Tehran, Iran enrolled in this cross sectional study. Using HRM, Dxs Therascreen and Pyrosequencing methods, we analyzed the mutational status of KRAS and BRAF genes in these. Results: KRAS mutations were present in 33.6% cases (n=336). Of KRAS mutation positive cases, 85.1% were in codon 12 and 14.9% were in codon 13. The most frequent mutation at KRAS codon 12 was Gly12Asp; BRAF mutations were not found in any mCRC patients (n=242). In addition, we observed a strong correlation of KRAS mutations with some clinicopathological characteristics. Conclusions: KRAS mutations are frequent in mCRCs while presence of BRAF mutations in these patients is rare. Moreover, associations of KRAS genotypes with non mucinous adenocarcinoma and depth of invasion (pT3) were remarkable.     

High Frequency of Genes’ Promoter Methylation, but Lack of BRAF V600E Mutation among Iranian Colorectal Cancer Patients

Gene silencing due to DNA hypermethylation is a major mechanism for loss of tumor suppressor genes function in colorectal cancer. Activating V600E mutation in BRAF gene has been linked with widespread methylation of CpG islands in sporadic colorectal cancers. The aim of the present study was to evaluate the methylation status of three cancer-related genes, APC2, p14ARF, and ECAD in colorectal carcinogenesis and their association with the mutational status of BRAF and KRAS among Iranian colorectal cancer patients. DNA from 110 unselected series of sporadic colorectal cancer patients was examined for BRAF V600E mutation by PCR-RFLP. Promoter methylation of genes in tumors was determined by methylation specific PCR. The frequency of APC2, E-CAD, and p14 methylation was 92.6%, 40.4% and 16.7%, respectively. But, no V600E mutation was identified in the BRAF gene in any sample. No association was found in cases showing epigenetic APC, ECAD, and p14 abnormality with the clinicopathological parameters under study. The association between KRAS mutations and the so called methylator phenotype was previously reported. Therefore, we also analyzed the association between the hot spot KRAS gene mutations in codons of 12 and 13 with genes' promoter hypermethylation in a subset of this group of patients. Out of 86 tumors, KRAS was mutated in 24 (28%) of tumors, the majority occurring in codon 12. KRAS mutations were not associated with genes' methylation in this tumor series. These findings suggest a distinct molecular pathway for methylation of APC2, p14, and ECAD genes from those previously described for colorectal cancers with BRAF or KRAS mutations.     

Oncogenic PIK3CA mutations in colorectal cancers and polyps

Oncogenic PIK3CA mutations contribute to colorectal tumorigenesis by activating AKT signaling to decrease apoptosis and increase tumor invasion. A synergistic association of PIK3CA mutation with KRAS mutation has been suggested to increase AKT signaling and resistance to antiepidermal growth factor receptor inhibitor therapy for advanced colorectal cancer, although studies have been conflicting. We sought to clarify this by examining PIK3CA mutation frequency in relation to other key molecular features of defined pathways of tumorigenesis. PIK3CA mutation was assessed by high resolution melt analysis in 829 colorectal cancer samples and 426 colorectal polyps. Mutations were independently correlated with clinicopathological features including patient age, sex and tumor location as well as molecular features including microsatellite instability, KRAS and BRAF mutation, MGMT methylation and the CpG Island Methylator Phenotype (CIMP). Mutation of the helical (Exon 9) and catalytic (Exon 20) domain mutation hotspots were also examined independently. Overall, PIK3CA mutation was positively correlated with KRAS mutation (p < 0.001), MGMT methylation (p = 0.007) and CIMP (p < 0.001). Novel, exon-specific associations linked Exon 9 mutations to a subgroup of cancers characterized by KRAS mutation, MGMT methylation and CIMP-Low, whilst Exon 20 mutations were more closely linked to features of serrated pathway tumors including BRAF mutation, microsatellite instability and CIMP-High or Low. PIK3CA mutations were uncommonly, but exclusively, seen in tubulovillous adenomas (4/124, 3.2%) and 1/4 (25.0%) tubulovillous adenomas with a focus of cancer. These data provide insight into the molecular events driving traditional versus serrated pathway tumorigenesis.     

KRAS, BRAF and PIK3CA mutations in human colorectal cancer: relationship with metastatic colorectal cancer

Many abnormal gene expressions and dysregulated signaling pathways have been found in human colorectal cancer. Activating mutations of the KRAS, BRAF or PIK3CA oncogenes are frequently found in colorectal cancer. The aim of the study was to investigate the molecular occurrence of KRAS, BRAF and PIK3CA mutations in the colorectal tumorigenesis and to study the association of these events with clinicopathological parameters. In our study, DNA was extracted from 200 cases of human colorectal cancer tissue samples. KRAS, BRAF and PIK3CA mutation analysis was performed by PCR and pyrosequencing. Using statistical methods, we analyzed the relationships between the gene mutations and clinicopathological parameters. KRAS point mutations were detected in 63/200 patients (31.5%), with codon 12 mutations in 52/200 patients (26%), codon 13 mutations in 10/200 patients (5%) and codon 12.13 bi-mutations in 1/200 patients (0.5%). The V600E mutations of BRAF were detected in 14/200 patients (7%). PIK3CA point mutations (exon 9, exon 20) were detected in 25/200 (12.5%) patients, exon 9 mutatons in 12/200 patients (6%) and exon 20 mutations in 13/200 (6.5%). Our study suggested that both KRAS and BRAF mutations are exclusive, but KRAS and PIK3CA mutations are coexistent. The mutational status of BRAF did not correlate with Dukes' staging, histological type, age and gender. However, strong associations were found between KRAS, PIK3CA mutations and Dukes' staging (staging D, 12/25, 48%). Notably, our data indicated that colorectal cancers with KRAS and PIK3CA bi-mutations are more likely to develop into liver metastasis.