Melanoma NRAS/BRAF Mutations: A Population-Based Study

描述（由申请人提供）：黑色素瘤的发病率正在迅速增加，它仍然是一种潜在的致命疾病，医疗选择不足，预防方法存在争议。由于这一疾病的负担和致死率日益增加，预计改进预防、早期诊断和治疗方法将日益重要。NRAS和BRAF是RAS-RAF-MEK-ERK-MAP细胞信号通路中的介质，是迄今为止描述的黑色素瘤中最常见的突变癌基因。然而，尽管在原发性人类黑素瘤中发现了这些突变，但黑素瘤中NRAS和BRAF突变的频率和突变谱尚未得到充分表征，并且关于这些突变与黑素瘤的异质性、前体病变、风险和预后的关系的知识库存在重大空白。本研究的具体目的是：(1)确定原发性皮肤浸润性黑色素瘤中NRAS和BRAF体细胞改变的人群频率和突变谱及其与组织学亚型和潜在前体病变的关系；(2)确定NRAS和BRAF突变表型与已知预后指标和危险因素之间的关系。在这项研究中，我们收集了2000年北卡罗来纳州大约300名连续的恶性黑色素瘤患者。完整的流行病学资料，病理和肿瘤块已获得这些患者。NRAS和BRAF体细胞突变将采用高灵敏度的单链构象多态性（SSCP）分析技术结合PCR产物的直接测序来检测和表征。以人群为基础的这些突变频率将被确定，并在病理上不同的黑色素瘤亚型（浅表性扩散、恶性黄斑、结节性和肢端黄斑）之间进行比较。在与痣相关的黑色素瘤样本中，将使用激光捕获显微解剖分别分析该成分的突变。突变表型将与亚型、潜在的前驱病变、危险因素和预后指标相关。本研究获得的数据有望阐明NRAS和BRAF在黑色素瘤的发生、进展和异质性中的作用，最终导致更好的预防、分类和治疗。阐明这些突变如何与环境和遗传因素产生关系，将导致更多基于证据的风险因素避免建议。此外，了解突变是如何与前体产生关系的，应该提供有关哪些潜在的前体应该被移除的信息。这项研究还有望发现新的血液治疗靶点，并更有效地测试最近开发的NRAS和BRAF信号抑制剂。

DESCRIPTION (provided by applicant): Melanoma, which is rapidly increasing in incidence, remains a potentially fatal disease with poor medical treatment options and controversial methods of prevention. Because of the increasing burden of this disease and its lethality, improved methods of prevention, early diagnosis and treatment are expected to be of increasing importance. NRAS and BRAF, mediators in the RAS-RAF-MEK-ERK-MAP cell signaling pathway, are the most commonly mutated oncogenes thus far described for melanoma. However, despite the identification of these mutations in primary human melanomas, the frequency and mutational spectrum of NRAS and BRAF mutations in melanoma have not been fully characterized and there is a critical gap in the knowledge base regarding the association of these mutations with heterogeneity, precursor lesions, risk, and prognosis in melanoma. The specific aims of this study are to: (1) determine the population-based frequency and mutational spectrum of NRAS and BRAF somatic alterations in primary cutaneous invasive melanoma and their associations with histologic subtype and potential precursor lesions, and (2) determine associations between NRAS and BRAF mutational phenotypes and known prognostic indicators and risk factors. For this study, a group of approximately 300 consecutive patients with malignant melanoma in North Carolina in the year 2000 has been assembled. Complete epidemiologic data, pathology, and tumor blocks have been obtained for these patients. NRAS and BRAF somatic mutations will be detected and characterized using the highly sensitive technique of single strand conformational polymorphism (SSCP) analysis combined with direct sequencing of PCR products. The population-based frequency of these mutations will be determined and compared between pathologically distinct subtypes of melanoma (superficial spreading, lentigo maligna, nodular, and acral lentiginous). In melanoma samples associated with a nevus, this component will be analyzed separately for mutations using laser capture microdissection. Mutational phenotype will be associated with subtype, potential precursor lesions, risk factors, and prognostic indicators. The data derived from this study is expected to clarify the role of NRAS and BRAF in the development, progression and heterogeneity of melanoma, ultimately leading to better prevention, classification and treatment. Elucidation of how these mutations might arise in relationship to environmental and hereditary factors should result in more evidence-based recommendations for risk factor avoidance. In addition, understanding how mutations arise in relationship to precursors should provide information regarding which potential precursors should be removed. This study is also expected to lead to identification of new hemotherapeutic targets and more efficient testing of inhibitors for NRAS and BRAF signaling, which have recently been developed.