BRAFV600E基因突变在甲状腺癌中的临床应用研究进展

B型RAF基因(BRAF)编码蛋白质的第600位密码子对应的缬氨酸被谷氨酸替代(BRAFV600E突变)是甲状腺乳头状癌中最常见的基因突变.很多研究表明,该突变与甲状腺乳头状癌的发生、发展和转移密切相关.该文综合阐明BRAFV600E突变在甲状腺乳头状癌中的术前诊断、预后判断和抑制剂治疗等方面的临床应用,以便更好地指导临床决策.     

Involvement of Krüppel-like factor 6 (KLF6) mutation in the development of nonpolypoid colorectal carcinoma

AIM: To examine Krüppel-like factor 6 (KLF6) mutations in nonpolypoid-type tumors and alterations of K-ras, p53,and B-raf in relation between mutation and morphologic type, particularly nonpolypoid-type colorectal carcinomas.METHODS: Fifty-five early nonpolypoid colorectal carcinomas were analyzed. Loss of heterozygosity (LOH) of KLF6 and p53 was determined by microsatellite assay.Mutations of KLF6, K-ras, and B-raf were examined by polymerase chain reaction-single-strand conformation polymorphism followed by direct sequencing. In LOH-positive and/or mutation-positive tumors, multiple (4-7) samples in each tumor were microdissected and examined for genetic alterations, p53 expression was evaluated by immunohistochemistry.RESULTS: LOH of KLF6 and p53 was found in 14 of 29 (48.3%) and 14 of 31 (45.2%) tumors, respectively. In 10 of the 14 (71.4%) KLF6 LOH-positive tumors and 9 of the 14 (64.3%) p53 LOH-positive tumors, LOH was found in all of the microdissected samples. In 1 of the 10 (10.0%) KLF6 LOH-positive tumors, a single missense mutation was identified. K-ras and B-raf mutations were found in 5 of 55 (9.1%) and 6 of 55 (10.9%) tumors,respectively. However, these mutations were detected only in subsets of microdissected tumor samples.CONCLUSION: These data suggest that KLF6 and p53 mutations are involved in the development of nonpolypoid colorectal carcinoma, whereas K-ras and B-raf mutations are not.     

K-ras and B-raf gene mutations are not associated with gastrin- and CCK2-receptor mRNA expression in human colorectal tumour tissues

BACKGROUND: Colorectal cancer is a multistep process caused by genetic alterations in cell growth regulatory genes such as K-ras and B-raf. It has been assumed that mutations in the K-ras gene induce gastrin gene expression and that gastrin stimulates the growth of colorectal cancer in an autocrine fashion by coexpressing gastrin and cholecystokinin (CCK)2 receptors. The aim of this study was to examine a possible association of K-ras and B-raf gene mutations with gastrin and CCK2 receptor mRNA expression in human colon and rectum tumour biopsy specimens. METHODS: K-ras and B-raf gene mutations as well as gastrin and CCK2 receptor mRNA expression in 50 colon and 46 rectum biopsies, respectively, were determined using molecular biology methods. RESULTS: K-ras mutations occurred in 44% colon and 30% rectum and B-raf mutations in 16% colon and 4% rectum tumours, respectively. Gastrin mRNA was expressed in 64% colon and 61% rectum tumours, whereas CCK2 receptor mRNAs was expressed in 32% colon and 13% rectum tumours. K-ras or B-raf gene mutations and simultaneous gastrin mRNA expression was observed in 40% colon and 17% rectum tumours, respectively. Co-expression of gastrin and CCK2 receptor mRNA occurred in 20% colon and 9% rectal tumours. CONCLUSIONS: The results do not support the hypothesis that K-ras and B-raf gene mutations have an impact on gastrin- and CCK-receptor mRNA expression in colorectal tumour tissues.     

Involvement of Krüippel-like factor 6 （KLF6） mutation in the development of nonpolypoid colorectal carcinoma

AIM： To examine Kruppel-like factor 6 （KLF6） mutations in nonpolypoid-type tumors and alterations of K-ras, p53, and B-raf in relation between mutation and morphologic type, particularly nonpolypoid-type colorectal carcinomas.
METHODS： Fifty-five early nonpolypoid colorectal carcinomas were analyzed. Loss of heterozygosity （LOH） of KLF6 and p53 was determined by microsatellite assay. Mutations of KLF6, K-ras, and B-raf were examined by polymerase chain reaction-single-strand conformation polymorphism followed by direct sequencing. In LOH- positive and/or mutation-positive tumors, multiple （4-7） samples in each tumor were microdissected and examined for genetic alterations, p53 expression was evaluated by immunohistochemistry. RESULTS： LOH of KLF6 and p53 was found in 14 of 29 （48.3%） and 14 of 31 （45.2%） tumors, respectively. In tO of the 14 （71.4%） KLF6 LOH-positive tumors and 9 of the 14 （64.3%） p53 LOH-positive tumors, LOH was found in all of the microdissected samples. In 1 of the tO （10.0%） KLF6 LOH-positive tumors, a single missense mutation was identified. K-ras and B-raf mutations were found in 5 of 55 （9.1%） and 6 of 55 （10.9%） tumors, respectively. However, these mutations were detected only in subsets of microdissected tumor samples.
CONCLUSION： These data suggest that KLF6 and p53 mutations are involved in the development of nonpolypoid colorectal carcinoma, whereas K-ras and B-raf mutations are not.     

Constitutive Activation of the Mitogen-Activated Protein Kinase Signaling Pathway in Acral Melanomas

One of the most attractive clinical targets for melanoma is the mitogen-activated protein kinase (MAPK) signaling pathway. In this study, we examined MAPK signaling activation in a total of 28 acral melanoma samples, consisting of 13 primary tumors and 15 metastases. In line with the previous reports, NRAS/BRAF mutations were rare; only one metastatic tumor had an NRAS E61R mutation, and one primary tumor and two metastases harbored BRAF V599E mutations. Western blot analyses, however, revealed phosphorylated extracellular signal-regulated kinase (ERK)1/2 proteins in 11 of 14 (78.5%) of the acral melanoma tumors. Furthermore, fluorescence in situ hybridization analyses revealed the prominent amplification of the cyclin D1 ( CCND1 ) gene, which is an important down-stream effecter of the MAPK pathway, in 5 of 21 (23.8%) tumors examined. Interestingly, two of three tumors that were negative for phosphorylated ERK proteins according to western blot harbored CCND1 amplifications, suggesting that the increased gene dosage of CCND1 may exert effects similar to phosphorylated ERK proteins in cell growth. We conclude that, despite the low frequency of BRAF/NRAS mutations, the MAPK signaling pathway is constitutively activated in the majority of acral melanomas. This provides a rational basis to include acral melanomas into the clinical trials with MAPK inhibitors.     

Proficiency of DNA repair genes and microsatellite instability in operated colorectal cancer patients with clinical suspicion of lynch syndrome

Background

Lynch syndrome (LS) diagnosis is underestimated, and most of the patients remain undetected after colorectal resections. The study aims to assess the frequency of LS in patients undergoing surgical treatment for colorectal cancer (CRC).

Methods

A total of 458 CRC patients were operated from January 2005 to December 2008. Positive CRC family history (FH) was present in 118 (25.8%) patients. Histologic sections were reviewed for microsatellite instability (MSI) criteria (Bethesda guidelines), immunohistochemical (IHC) analysis for MLH1, MSH2, MSH6, PMS2 proteins, through the avidin-biotin-peroxidase complex, MSI (BAT-25, BAT-26, NR-21, NR-24 and MONO-27) and BRAF somatic mutation.

Results

Of the 118 patients with FH, 61 (51.69%) met at least one of the revised Bethesda criteria. IHC was abnormal in 8 (13.1%) and MSI in 12 patients (20%). BRAF was negative in all cases. MSI histopathological included: intratumoral lymphocytes (47.5%), expansive tumors (29.5%) mucinous component (27.8%) and Crohn’s like reaction in (14.7%). There was an association between the revised Bethesda criteria with: sex, mucinous histology and Crohn’s like reaction; MSI and IHC with PMS2 and MLH1. Revised Bethesda criteria 4 had 10.6 increased chances to display positive MSI. We have proposed a score to contribute as a practical tool in the diagnosis of LS.

Conclusions

The frequence of LS in resected CRC patients was 2.6%. The criterion 4 Revised Bethesda was associated more strongly with the presence of MSI.     

BRAF V600E突变蛋白在皮肤黑素瘤中的表达

目的 探讨皮肤黑素瘤BRAF V600E突变蛋白表达情况,分析免疫组化法检测V600E突变的灵敏度和特异度。 方法 应用抗BRAF V600E单克隆抗体的免疫组化法检测103例皮肤黑素瘤、40例色素痣石蜡包埋组织切片中BRAF V600E突变蛋白表达水平。采用SPSS 17.0统计软件进行统计分析,率的比较采用χ2检验。 结果 BRAF V600E突变蛋白阳性表达率在皮肤黑素瘤中为20.4%（21/103）,色素痣中为5.0%（2/40）,两组差异有统计学意义（χ2 = 5.06,P < 0.05）。黑素瘤BRAF V600E突变蛋白的表达率在不同年龄组［＜ 60岁组表达率为29.8%（14/47）, ≥ 60岁组为12.5%（7/56）］、不同民族［维吾尔族组为30.2%（13/43）,汉族组为13.3%（8/60）］、不同发病部位［肢端为13.6%（6/42）、黏膜为11.8%（4/29）、非肢端为45.8%（11/32）］、不同Clark分级［Ⅰ ~ Ⅲ级组为8.6%（4/42）,Ⅳ ~ Ⅴ级组为12.4%（17/61）］组间表达差异均有统计学意义（P < 0.05）,而在不同性别、有无淋巴结转移组间表达差异均无统计学意义（P ＞ 0.05）。免疫组化检测恶性黑素瘤中BRAF V600E突变灵敏度为100%（15/15）,特异度为98.5%（65/66）。 结论 BRAF V600E突变蛋白在皮肤黑素瘤中高表达,在维吾尔族人群表达率高于汉族人群;免疫组化法检测BRAF V600E突变具有准确、快速等特点。     

Expression status and mutational analysis of the ras and B-raf genes in ovarian granulosa cell and epithelial tumors

OBJECTIVES: The molecular pathogenesis of granulosa cell tumors of the ovary (GCT) is not understood. Activating mutations in the K-, N-, and H-ras protooncogenes have been identified in a wide range of human cancers, including ovarian epithelial tumors. Furthermore, an apparent association has recently been reported between the presence of ras and B-raf mutations in the same cancer types. Activation of the ras/raf pathway would be predicted to be tumorigenic in granulosa cells. METHODS: Gene expression patterns of the three ras and B-raf genes were determined in a panel of GCT and ovarian epithelial tumors, and in normal premenopausal ovaries. Expression was determined by RT-PCR using gene-specific primers combined with Southern blot analysis of the PCR products using gene-specific (32)P-labeled probes. Direct sequence analysis was used to screen for known activating mutations. RESULTS: Widespread expression of the four genes was observed in all tumor types examined. Compared to the normal ovaries, none of the genes was expressed at significantly higher levels in any of the tumor types examined. A heterozygous point mutation in codon 12 of the K-ras gene was found in five of the 10 mucinous tumors. No B-raf mutations were detected in the mucinous tumors. No mutations were detected in any of the genes in the cohort of GCT. CONCLUSION: These results suggest that neither overexpression nor activating mutations of the ras or B-raf genes are associated with the development of GCT.