Melanoma NRAS/BRAF Mutations: A Population-Based Study

描述(申请人提供)：黑色素瘤，它的发病率正在迅速增加，仍然是一种潜在的致命疾病，缺乏医疗选择和有争议的预防方法。由于这种疾病日益加重的负担及其致命性，改进预防、早期诊断和治疗的方法预计将变得越来越重要。NRAS和BRAF是RAS-RAF-MEK-ERK-MAP细胞信号通路的介体，是迄今为止描述的黑色素瘤最常见的突变癌基因。然而，尽管在人类原发黑色素瘤中发现了这些突变，但NRAS和BRAF突变在黑色素瘤中的频率和突变谱尚未完全确定，关于这些突变与黑色素瘤的异质性、前驱病变、风险和预后的相关性的知识基础存在严重差距。本研究的具体目的是：(1)确定原发皮肤侵袭性黑色素瘤中NRAS和BRAF的体细胞改变在人群中的频率和突变谱，以及它们与组织学亚型和潜在的前驱病变的关系；(2)确定NRAS和BRAF突变表型与已知预后指标和危险因素的关系。在这项研究中，集合了2000年北卡罗来纳州大约300名连续患有恶性黑色素瘤的患者。已获得这些患者的完整流行病学数据、病理学和肿瘤块。NRAS和BRAF的体细胞突变将使用高度敏感的单链构象多态(SSCP)分析技术结合PCR产物的直接测序进行检测和表征。这些突变的人群频率将被确定，并在病理上不同的黑色素瘤亚型(浅表播散性、恶性雀斑、结节状和肢端雀斑样斑)之间进行比较。在与雀斑相关的黑色素瘤样本中，将使用激光捕获显微解剖技术单独分析这种成分的突变。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。来自这项研究的数据有望阐明NRAS和BRAF在黑色素瘤的发展、进展和异质性中的作用，最终导致更好的预防、分类和治疗。阐明这些突变是如何与环境和遗传因素有关的，应该会产生更多基于证据的风险因素避免建议。此外，了解与前体有关的突变是如何产生的，应该提供关于哪些潜在前体应该被移除的信息。这项研究还有望确定新的血液治疗靶点，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.