Colorectal serrated pathway cancers and precursors

The serrated pathway (SP) can be viewed as two parallel, but partially overlapping, arrays of colorectal precursor lesions, and their respective endpoint carcinomas, that are distinct from those of the conventional adenoma–carcinoma sequence (APC‐pathway). In this review we focus at the outset on the clinical impact, pathological features, molecular genetics and biological behaviours of the various SP cancers. Then we summarize the clinicopathological features, classification and molecular profiles of the two main precursor lesions that anchor the respective pathways: (i) sessile serrated adenoma/polyp (SSA/P), also called sessile serrated lesion (SSL), and (ii) traditional serrated adenoma (TSA). Activating mutations of the RAS–RAF–MAPK pathway initiate and sustain the lesions of the SP, and CpG island methylation of the promoter regions of tumour suppressor and DNA repair genes play the major role in their neoplastic progression. The SP includes microsatellite stable (MSS) carcinomas that are among the most biologically aggressive colorectal carcinomas (CRC), and also accounts for the great preponderance of sporadic hypermutated, mismatch repair (MMR)‐deficient or microsatellite instable (MSI) CRC. The identification, removal and appropriate classification of at‐risk SP precursors and surveillance of individuals who harbour these lesions present a challenge and opportunity for CRC prevention and mortality reduction.     

A trip through the signaling pathways of melanoma

Many cellular signaling pathways are involved in the development of cancer. Depending on the tumor entity, the nature as well as the mode of activation can differ. Some signaling pathways frequently show changes as all tumor cells have to fulfill some basic requirements such as independence from growth factors or insensitivity against apoptosis. In this review, the possibilities of a tumor to manipulate signaling pathways to reach these goals are exemplified based on an archetypical melanoma cell. In addition, new therapeutic options based on the knowledge of signaling pathways will be discussed.     

结直肠癌RAS、BRAF基因状态与临床病理特征的关系

目的分析中国人群结直肠癌患者中KRAS、NRAS及BRAF基因突变状态与临床病理特征之间的关系。方法回顾性分析2018年1月—2020年11月于福建省肿瘤医院接受治疗的370例结直肠癌患者的肿瘤组织标本,检测KRAS、NRAS、BRAF基因突变状态及MMR蛋白表达状态,分析基因突变状态与结直肠癌临床病理特征的关系。结果370例患者中存在KRAS基因突变155例(41.9%),NRAS基因突变19例(5.1%),BRAF基因突变40例(10.8%),其中1例患者突变类型为G469V,其他均为V600E突变。KRAS基因在女性、高中分化患者中突变率高(P<0.05)。NRAS基因突变多见于低分化、浸润型患者(P<0.05)。BRAF V600E突变在右半结肠癌、年龄小于50岁、低分化、浸润型、淋巴结及远处转移患者中的突变率高(P<0.05)。结论KRAS基因突变与性别、分化程度有关,NRAS基因突变与分化程度、肿瘤大体分类有关,BRAF基因V600E突变与肿瘤原发部位、年龄、分化程度、肿瘤大体分类、区域淋巴结及远处转移有关。对结直肠癌患者进行KRAS、NRAS及BRAF基因的检测,为了解中国患者热点基因突变分布情况和临床精准诊疗提供理论依据。     

Phenotypic and genotypic differences in colorectal carcinoma among Caucasians,Asians, and Hispanics lack statistical significance

Colorectal carcinoma (CRC) has been shown to have both genetic and environmental factors that can promote carcinoma development. Previous studies have found ethnic differences in the distribution of molecular phenotypes of CRC. Very little specific data exist regarding Hispanic CRC, and these data primarily focus on epidemiology or location of carcinoma. Our retrospective study analyzed 562 Caucasian, Asian, and Hispanic CRC patients at the UCI Medical Center from 2004 to 2012. The results showed that there were no statistically significant differences with respect to mean age, gender or site of carcinoma among the three ethnic groups. There were no statistically significant differences among the three ethnicities with respect to rates of MSI, mutated BRAF, and mutated KRAS. The Caucasian group had a non-significant higher rate of MSI (15%) and BRAF mutation (12%) than the Asian and Hispanic groups. Hispanics had a non-significant higher rate of KRAS mutation (59%) than Caucasians (38%) and Asians (37%). The results of this study demonstrated a higher rate of MSI and BRAF mutation in the Caucasian group and a higher rate of KRAS mutation in the Hispanic group, however differences were not statistically significant.     

Survivin蛋白和BRAF基因在甲状腺癌中的表达

甲状腺癌是头颈部常见的恶性肿瘤.如何鉴别及确定良、恶性甲状腺结节并估计预后的特异性肿瘤分子标记物对于甲状腺肿瘤患者的诊断和治疗具有重要意义.本文就与甲状腺癌发生发展及预后相关的BRAF基因和Survivin蛋白的表达两个方面予以综述.     

Melanoma patient derived xenografts acquire distinct Vemurafenib resistance mechanisms

Variable clinical responses, tumor heterogeneity, and drug resistance reduce long-term survival outcomes for metastatic melanoma patients. To guide and accelerate drug development, we characterized tumor responses for five melanoma patient derived xenograft models treated with Vemurafenib. Three BRAF^V600E models showed acquired drug resistance, one BRAF^V600E model had a complete and durable response, and a BRAF^V600V model was expectedly unresponsive. In progressing tumors, a variety of resistance mechanisms to BRAF inhibition were uncovered, including mutant BRAF alternative splicing, NRAS mutation, COT (MAP3K8) overexpression, and increased mutant BRAF gene amplification and copy number. The resistance mechanisms among the patient derived xenograft models were similar to the resistance pathways identified in clinical specimens from patients progressing on BRAF inhibitor therapy. In addition, there was both inter- and intra-patient heterogeneity in resistance mechanisms, accompanied by heterogeneous pERK expression immunostaining profiles. MEK monotherapy of Vemurafenib-resistant tumors caused toxicity and acquired drug resistance. However, tumors were eradicated when Vemurafenib was combined the MEK inhibitor. The diversity of drug responses among the xenograft models; the distinct mechanisms of resistance; and the ability to overcome resistance by the addition of a MEK inhibitor provide a scheduling rationale for clinical trials of next-generation drug combinations.