Prognostic significance of defective mismatch repair and BRAF V600E in patients with colon cancer

PURPOSE: Colon tumors with defective DNA mismatch repair (dMMR) have a well-characterized phenotype and accounts for approximately 15% to 20% of sporadic colon cancer as well as those colon cancer patients with Lynch syndrome. Although the presence of dMMR seems to be a favorable prognostic marker, data suggest that these patients do not respond as well to adjuvant chemotherapy. EXPERIMENTAL DESIGN: In this study, we examined the prognostic significance of tumor MMR deficiency and the presence of a specific mutation in BRAF (V600E) in a group of patients (n = 533) who participated in a randomized prospective clinical trial through the North Central Cancer Treatment Group. RESULTS: Tumors with dMMR were found to be associated with higher tumor grade (P = 0.001), proximal location (P < 0.0001), and improved overall and disease-free survival (P = 0.05 and 0.04, respectively). Among all cases examined, evaluation of the BRAF V600E mutation status revealed no statistically significant differences in either disease-free or overall survival. Patients were then grouped into four categories for further analysis: dMMR/BRAF(-), dMMR/BRAF(+), pMMR/BRAF(-), and pMMR/BRAF(+). The dMMR/BRAF(-) group had a significantly improved overall survival (5-year overall survival of 100% versus 73%, P = 0.002) compared with all others. The remaining three groups had very similar survival outcomes. An additional cohort of tumors previously classified as having dMMR were also tested for the BRAF V600E alteration. Results remained significant (P = 0.006) when the two groups were combined for analysis. CONCLUSIONS: Overall, these data suggest that the underlying molecular etiology of those tumors having dMMR may influence the disease outcome in these patients.     

VE1 immunohistochemistry predicts BRAF V600E mutation status and clinical outcome in colorectal cancer

Aim

VE1 is a monoclonal antibody detecting mutant BRAF^V600E protein by immunohistochemistry. Here we aim to determine the inter-observer agreement and concordance of VE1 with mutational status, investigate heterogeneity in colorectal cancers and metastases and determine the prognostic effect of VE1 in colorectal cancer patients.

Methods

Concordance of VE1 with mutational status and inter-observer agreement were tested on a pilot cohort of colorectal cancers (n = 34), melanomas (n = 23) and thyroid cancers (n = 8). Two prognostic cohorts were evaluated (n = 259, Cohort 1 and n = 226, Cohort 2) by multiple-punch tissue microarrays. VE1 staining on preoperative biopsies (n = 118 patients) was compared to expression in resections. Primary tumors and metastases from 13 patients were tested for VE1 heterogeneity using a tissue microarray generated from all available blocks (n = 100 blocks).

Results

Inter-observer agreement was 100% (kappa = 1.0). Concordance between VE1 and V600E mutation was 98.5%. Cohort 1: VE1 positivity (seen in 13.5%) was associated with older age (p = 0.0175) and MLH1 deficiency (p < 0.0001). Cohort 2: VE1 positivity (seen in 12.8%) was associated with female gender (p = 0.0016), right-sided tumor location (p < 0.0001), higher tumor grade (p < 0.0001) and mismatch repair (MMR)-deficiency (p < 0.0001). In survival analysis, MMR status and postoperative therapy were identified as possible confounding factors. Adjusting for these features, VE1 was an unfavorable prognostic factor. Preoperative biopsy staining matched resections in all cases except one. No heterogeneity was found across any primary/metastatic tumor blocks.

Conclusion

VE1 is highly concordant for V600E and homogeneously expressed suggesting staining can be analysed on resection specimens, preoperative biopsies, metastatic lesions and tissue microarrays.     

Ethnicity and risk for colorectal cancers showing somatic BRAF V600E mutation or CpG island methylator phenotype

Colorectal cancers arising from serrated polyps are characterized by the CpG island methylator phenotype (CIMP) and somatic mutation (V600E) in the BRAF proto-oncogene. Few epidemiologic studies have investigated risk factors for these tumors. We conducted a cohort study of 41,328 residents of Melbourne, Australia that included 9,939 participants of southern European origin and 31,389 of Anglo-Celtic origin. Colorectal adenocarcinomas were identified from population-based cancer registries. BRAF V600E mutation in tumors was determined using a PCR-based allelic discrimination method. Tumors were classified as CIMP positive when at least three of five markers (RUNX3, CACNA1G, SOCS1, NEUROG1, and IGF2) were methylated according to MethyLight analysis. Hazard ratios (HR) and 95% confidence intervals (95% CI) were estimated by Cox regression with adjustment for risk factors for colorectal cancer. During follow-up, 718 participants were diagnosed with colorectal cancer. CIMP assays were done for 579 and BRAF V600E mutation testing for 582. After adjustment for other risk factors, when compared with people of Anglo-Celtic origin, those of southern European origin had lower incidence of colorectal cancer that had CIMP (HR, 0.32; 95% CI, 0.16-0.67) or BRAF mutations (HR, 0.30; 95% CI, 0.16-0.58) but similar incidence of colorectal cancer without CIMP (HR, 0.86; 95% CI, 0.70-1.05) or BRAF (HR, 0.90; 95% CI, 0.74-1.11). People of southern European origin had lower risk of colorectal cancers with CIMP and BRAF mutation than people of Anglo-Celtic origin, which may in part be due to genetic factors that are less common in people of southern European origin.     

BRAF V600E mutation in metastatic colorectal cancer: Methods of detection and correlation with clinical and pathologic features

The screening for BRAF V600E mutation is employed in clinical practice for its prognostic and potentially predictive role in patients with metastatic colorectal carcinoma (mCRC). Little information is available on the sensitivity and specificity of the testing methods to detect this mutation in CRC. By using serial dilution of BRAF mutant DNA with wild type DNA, we found that the sensitivity of allelic discrimination-Real Time PCR was higher than PCR-Sequencing (10% vs 20%). In agreement, the Real Time PCR assay displayed increased analytical sensitivity in detecting the BRAF V600E mutation as compared with PCR-Sequencing in a cohort of 510 consecutive CRCs (21 vs 16 cases). Targeted resequencing demonstrated that all cases negative by PCR-Sequencing had an allelic frequency of the BRAF mutation <20%, thus suggesting tumor heterogeneity. The association of BRAF mutations with clinical and pathological features was assessed next in a cohort of 840 KRAS exon 2 wild type CRC patients screened with the Real Time PCR assay. The BRAF V600E mutation frequency in this cohort was 7.8% that increased to 33.4% in females over 70 y of age with right-sided tumor location. BRAF mutations were also detected in 4.4% of male patients with left-sided tumors and aged <70 y. Fourteen of 61 (22.9%) BRAF V600E mutation bearing patients exhibited microsatellite instability (MSI) as assessed by T17 mononucleotide sequence within intron 8 of HSP110. Our study indicates that Real Time PCR-based assays are more sensitive than PCR-Sequencing to detect the BRAF V600E mutation in CRC and that BRAF mutations screening should not be restricted to selected patients on the basis of the clinical-pathological characteristics.     

BRAF基因V600E突变在甲状腺病变中的表达

目的 分析BRAF基因V600E突变在中国汉族人群甲状腺病变中的表达情况.方法 240例甲状腺病变中,乳头状癌(PTC)129例(其中经典型PTC 121例,滤泡型PTC 8例).滤泡癌12例,髓样癌4例,甲状腺隙瘤30例,结节性甲状腺肿30例,Lp状腺乳头状增生35例.采用常规酚.氯仿法抽提87例新鲜组织样本的总DNA,改良试剂盒法抽提153例石蜡组织样本的总DNA,经过PCR、测序,检测BRAF V600E突变.结果 在240例甲状腺病变中,BRAF V6OOE突变61例,发生率为25.4%.61例BRAF V600E突,变患者均为PTC,占PTC的47.3%.BRAF V600E突变在经典型PTC中的表达率(49.6%)与在滤泡型PTC中的表达率(12.5%)比较,差异有统计学意义(P<0.05).BRAF V600E突变与PTC患者临床病理参数间的差异无统计学意义(P>0.05).结论 BRAFV600E突变与PTC的发生、发展可能有着重要联系,BRAF V600E突变可以作为PTC诊断的特异性标记;改良的试剂盒法抽提石蜡组织DNA具有高效、简便、价格栩对低廉的优点.

Abstract：

Objective To evaluate the expression of BRAF V600E mutation in 240 Chinese patients with thyroid lesions. Methods Two hundred and forty Chinese patients with thyroid lesions, including 129 papillary thyroid carcinomas (PTC) , 12 follicular carcinomas, 4 medullary carcinomas, 30 adenomas, 30 nodular goiters, and 35 papillary hyperplasia. DNA was extracted from thyroid biopsy and paraffin embedded thyroid tissues, and the expression of BRAF V600E mutation was detected by polymerase chain reaction and DNA sequencing assays. Results The presence of BRAF V600E mutation was found in 61 of the total group of 240 cases (25. 4%). It was only detected in PTC (47. 3%), and not detected in other types of malignant and benign thyroid lesions. There was a statistically significant difference between the expression of BRAF V600E mutation in classic type PTC (49. 6% ) and in follicular type PTC (12. 5% ,P <0. 05) , but statistical data did not show any correlation between BRAF V600E mutation and clinicopathologic parameters in PTC (P > 0. 05). Conclusions BRAF V600E mutation has a significant correlation with PTC and the detection of BRAF V600E mutation may be used as an important prognostic marker of PTC. Our new method of DNA extraction from paraffin embedded tissues is efficient and inexpensive.     

BRAF基因V600E突变在甲状腺病变中的表达

目的 分析BRAF基因V600E突变在中国汉族人群甲状腺病变中的表达情况.方法 240例甲状腺病变中,乳头状癌(PTC)129例(其中经典型PTC 121例,滤泡型PTC 8例).滤泡癌12例,髓样癌4例,甲状腺隙瘤30例,结节性甲状腺肿30例,Lp状腺乳头状增生35例.采用常规酚.氯仿法抽提87例新鲜组织样本的总DNA,改良试剂盒法抽提153例石蜡组织样本的总DNA,经过PCR、测序,检测BRAF V600E突变.结果 在240例甲状腺病变中,BRAF V6OOE突变61例,发生率为25.4%.61例BRAF V600E突,变患者均为PTC,占PTC的47.3%.BRAF V600E突变在经典型PTC中的表达率(49.6%)与在滤泡型PTC中的表达率(12.5%)比较,差异有统计学意义(P<0.05).BRAF V600E突变与PTC患者临床病理参数间的差异无统计学意义(P>0.05).结论 BRAFV600E突变与PTC的发生、发展可能有着重要联系,BRAF V600E突变可以作为PTC诊断的特异性标记;改良的试剂盒法抽提石蜡组织DNA具有高效、简便、价格栩对低廉的优点.     

BRAF基因V600E突变在甲状腺病变中的表达

目的 分析BRAF基因V600E突变在中国汉族人群甲状腺病变中的表达情况.方法 240例甲状腺病变中,乳头状癌(PTC)129例(其中经典型PTC 121例,滤泡型PTC 8例).滤泡癌12例,髓样癌4例,甲状腺隙瘤30例,结节性甲状腺肿30例,Lp状腺乳头状增生35例.采用常规酚.氯仿法抽提87例新鲜组织样本的总DNA,改良试剂盒法抽提153例石蜡组织样本的总DNA,经过PCR、测序,检测BRAF V600E突变.结果 在240例甲状腺病变中,BRAF V6OOE突变61例,发生率为25.4%.61例BRAF V600E突,变患者均为PTC,占PTC的47.3%.BRAF V600E突变在经典型PTC中的表达率(49.6%)与在滤泡型PTC中的表达率(12.5%)比较,差异有统计学意义(P<0.05).BRAF V600E突变与PTC患者临床病理参数间的差异无统计学意义(P>0.05).结论 BRAFV600E突变与PTC的发生、发展可能有着重要联系,BRAF V600E突变可以作为PTC诊断的特异性标记;改良的试剂盒法抽提石蜡组织DNA具有高效、简便、价格栩对低廉的优点.     

Promoter methylation of Wnt5a is associated with microsatellite instability and BRAF V600E mutation in two large populations of colorectal cancer patients

Background:

In colorectal cancer (CRC), tumour microsatellite instability (MSI) status and CpG island methylator phenotype (CIMP) status are indicators of patient outcome, but the molecular events that give rise to these outcomes remain largely unknown. Wnt5a is a critical regulator of non-canonical Wnt activity and promoter hypermethylation of this gene has emerging prognostic roles in CRC; however the frequency and prognostic significance of this epigenetic event have not been explored in the context of colorectal tumour subtype. Consequently, we investigated the frequency and prognostic significance of Wnt5a methylation in a large cohort of MSI-stratified CRCs.

Methods:

Methylation was quantified in a large cohort of 1232 colorectal carcinomas from two clinically distinct populations from Canada. Associations were examined between methylation status and clinicopathlogical features, including tumour MSI status, BRAF V600E mutation, and patient survival.

Results:

In Ontario, Wnt5a methylation was strongly associated with MSI tumours after adjustment for age, sex, and tumour location (odds ratio (OR)=4.2, 95% confidence interval (CI)=2.4–7.4, P<10⁻⁶) and with BRAF V600E mutation, a marker of CIMP (OR=12.3, 95% CI=6.9–21.7, P<10⁻¹⁷), but was not associated with patient survival. Concordant results were obtained in Newfoundland.

Conclusion:

Methylation of Wnt5a is associated with distinct tumour subtypes, strengthening the evidence of an epigenetic-mediated Wnt bias in CRC.     

Epithelioid glioblastoma arising from pleomorphic xanthoastrocytoma with the BRAF V600E mutation

Pleomorphic xanthoastrocytoma (PXA) is classified by the World Health Organization as a grade II astrocytic tumor with relatively favorable prognosis among gliomas. A valine-to-glutamic acid substitution at position 600 of the serine/threonine-protein kinase BRAF (BRAF V600E) mutation, which is commonly found in PXA, has recently been detected in approximately 50 % of all epithelioid glioblastoma (GBM) cases. We herein report a case of epithelioid GBM developing at the site of a left temporal PXA 13 years after the treatment of the primary tumor. The BRAF V600E mutation was detected in both tumors. These findings suggest that epithelioid GBM may arise from a PXA with a BRAF V600E mutation.     

Poor survival associated with the BRAF V600E mutation in microsatellite-stable colon cancers

The BRAF V600E mutation has been associated with microsatellite instability and the CpG island methylator phenotype (CIMP) in colon cancer. We evaluated a large population-based sample of individuals with colon cancer to determine its relationship to survival and other clinicopathologic variables. The V600E BRAF mutation was seen in 5% (40 of 803) of microsatellite-stable tumors and 51.8% (43 of 83) of microsatellite-unstable tumors. In microsatellite-stable tumors, this mutation was related to poor survival, CIMP high, advanced American Joint Committee on Cancer (AJCC) stage, and family history of colorectal cancer [odds ratio, 4.23; 95% confidence interval (95% CI), 1.65-10.84]. The poor survival was observed in a univariate analysis of 5-year survival (16.7% versus 60.0%; P < 0.01); in an analysis adjusted for age, stage, and tumor site [hazard rate ratio (HRR), 2.97; 95% CI, 2.05-4.32]; in stage-specific, age-adjusted analyses for AJCC stages 2 to 4 (HRR, 4.88, 3.60, and 2.04, respectively); and in Kaplan-Meier survival estimates for AJCC stages 2 to 4 (P < 0.01 for all three stages). Microsatellite-unstable tumors were associated with an excellent 5-year survival whether the V600E mutation was present or absent (76.2% and 75.0%, respectively). We conclude that the BRAF V600E mutation in microsatellite-stable colon cancer is associated with a significantly poorer survival in stages 2 to 4 colon cancer but has no effect on the excellent prognosis of microsatellite-unstable tumors.     

BRAF mutation is associated with the CpG island methylator phenotype in colorectal cancer from young patients

This study investigated the relationship between BRAF mutation, the CpG island methylator phenotype (CIMP+) and APC methylation in colorectal cancer (CRC) from young patients. The V600E BRAF mutation was found in 7% of cases and was strongly associated with the tumour features of proximal site, advanced stage and poor histological grade. More than half (53%) the tumours with BRAF mutation were also CIMP+ as evaluated by a standard panel of markers, compared to only 4% of tumours with wildtype BRAF (P<0.0001). In contrast to CIMP+, APC methylation was inversely correlated with BRAF mutation (P=0.02). BRAF mutation and CIMP+ are therefore likely to be involved in an alternate, albeit rare, pathway to APC inactivation during the development of CRC in younger patients.     

Clinical and radiological findings of glioblastomas harboring a BRAF V600E mutation

Brain Tumor Pathology - The aim of this study was to analyze the clinical and radiological characteristics of glioblastomas (GBMs) harboring a BRAF mutation. Sequencing analysis of BRAF, IDH1/2,...     

Incidence of the BRAF V600E mutation in chronic lymphocytic leukaemia and prolymphocytic leukaemia

The spectrum of underlying molecular abnormalities of clinically and biologically heterogeneous chronic lymphocytic leukaemia (CLL) and prolymphocytic leukaemia (PLL) has yet to be identified. While whole genome sequencing has identified several genes implicated in the pathogenesis and progression of CLL, the molecular lesions in a substantial proportion of patients remain to be elucidated. The incidence of the BRAF V600E mutation, widely implicated in solid tumours and other B-cell malignancies, was sought in a cohort of patients with CLL and related disorders. One CLL patient and one patient with B-prolymphocytic leukaemia (PLL) were found to harbour this mutation. Although present at a low frequency, the finding of BRAF V600E has biological and clinical implications for CLL and PLL.     

High prevalence of mismatch repair deficiency in prostate cancers diagnosed in mismatch repair gene mutation carriers from the colon cancer family registry

The question of whether prostate cancer is part of the Lynch syndrome spectrum of tumors is unresolved. We investigated the mismatch repair (MMR) status and pathologic features of prostate cancers diagnosed in MMR gene mutation carriers. Prostate cancers (mean age at diagnosis = 62 ± SD = 8 years) from 32 MMR mutation carriers (23 MSH2, 5 MLH1 and 4 MSH6) enrolled in the Australasian, Mayo Clinic and Ontario sites of the Colon Cancer Family Registry were examined for clinico-pathologic features and MMR-deficiency (immunohistochemical loss of MMR protein expression and high levels of microsatellite instability; MSI-H). Tumor MMR-deficiency was observed for 22 cases [69 %; 95 % confidence interval (CI) 50–83 %], with the highest prevalence of MMR-deficiency in tumors from MSH2 mutation carriers (19/23, 83 %) compared with MLH1 and MSH6 carriers combined (3/9, 33 %; p = 0.01). MMR-deficient tumors had increased levels of tumor infiltrating lymphocytes compared with tumors without MMR-deficiency (p = 0.04). Under the assumption that tumour MMR-deficiency occurred only because the cancer was caused by the germline mutation, mutation carriers are at 3.2-fold (95 % CI 2.0–6.3) increased risk of prostate cancer, and when assessed by gene, the relative risk was greatest for MSH2 carriers (5.8, 95 % CI 2.6–20.9). Prostate cancer was the first or only diagnosed tumor in 37 % of carriers. MMR gene mutation carriers have at least a twofold or greater increased risk of developing MMR-deficient prostate cancer where the risk is highest for MSH2 mutation carriers. MMR IHC screening of prostate cancers will aid in identifying MMR gene mutation carriers.     

甲状腺乳头状癌BRAF V600E基因突变 及相关蛋白的表达

背景与目的:BRAF V600E基因突变可作为甲状腺乳头状癌靶向治疗的靶点,因此检测患者BRAF基因状态对于能否应用靶向药物治疗具有重要意义.观察BRAF V600E基因突变及突变蛋白VE1在甲状腺乳头状癌中的表达情况,并分析其与甲状腺乳头状癌的临床病理特征及其预后的关系.方法:采用DNA测序法及免疫组织化学法分别检测108例甲状腺乳头状癌、54例甲状腺腺瘤和54例结节性甲状腺肿标本中BRAF基因突变及其相关蛋白VE1的表达.结果:108例甲状腺乳头状癌基因突变率为67.6%,VE1表达率为64.8%,与甲状腺良性病变相比差异有统计学意义(P<0.05),与临床病理参数间无相关性.结论:甲状腺乳头状癌BRAF V600E基因突变率和BRAF V600E蛋白表达水平增高,可以作为鉴别甲状腺良、恶性肿瘤的有效指标.免疫组织化学法检测甲状腺乳头状癌BRAF V600E蛋白的表达与其基因突变的一致性高,可间接有效地反映BRAF V600E基因突变的状态.BRAF V600E基因突变及突变蛋白的表达与甲状腺乳头状癌患者预后无关.     

Non-V600E BRAF mutations and EGFR signaling pathway in colorectal cancer

The Raf murine sarcoma viral oncogene homolog B (BRAF^V600E) mutation (MT) in metastatic colorectal cancer (CRC) is a well-known prognostic indicator and a negative predictive biomarker for antiepidermal growth factor receptor (EGFR) treatment. However, the clinical characteristics and significance of BRAF^non-V600E MTs remain unclear. Here, we evaluated the clinical characteristics of BRAF^non-V600E MTs vs. those of other MTs in the EGFR signaling pathway, including BRAF^V600E. Consecutive CRC patients in our institute from June 2012 to November 2013 were enrolled in our study. Multiplex genotyping of the EGFR pathway was performed with archival samples using a Luminex Assay for BRAF^V600E/BRAF^non-V600E, KRAS/NRAS exons 2–4, and phosphatidylinositol-4,5-bisphosphate 3-kinase, catalytic subunit alpha (PIK3CA). We analyzed correlations among the MT profiles, clinical data and primary tumor locations in CRC. All statistical analyses were performed using R software. CRC samples (824) from 374 (45.4%) male and 450 (54.6%) female patients were analyzed, of which 154 (18.7%), 202 (24.5%), 270 (32.8%) or 198 (24.0%) had Stages I, II, III or IV or recurrent CRC, respectively. The frequencies of BRAF^V600E/BRAF^non-V600E, KRAS (including exons 2–4), NRAS and PIK3CA MTs were 5.3/1.7, 41.4, 3.3 and 9.6%, respectively. The characteristics of patients with the BRAF^V600E MT were an age of ≥65 years old, a right-sided primary tumor location, poorly differentiated histology and an advanced disease stage. In contrast, the characteristics of patients with BRAF^non-V600E MTs were a left-sided primary tumor location and well-differentiated histology. BRAF^non-V600E MTs were relatively rare and showed different characteristics compared to the BRAF^V600E MT. These results may contribute to future precision medicine.