皮肤黑素瘤94例临床病理特点与基因突变的关系

目的:探讨皮肤黑素瘤（CMM）临床病理特点及与易感基因突变的关系。方法:回顾分析新疆维吾尔自治区人民医院2009年1月至2019年12月确诊的94例CMM临床及组织病理学特征。48例留存黑素瘤石蜡组织标本,采用Sanger测序法检测黑素瘤组织中BRAF、NRAS、c-KIT基因及人端粒酶逆转录酶（hTERT）基因启动子...     

新疆80例恶性黑素瘤BRAF基因突变分析

目的 探讨BRAF基因突变与恶性黑素瘤临床表现的关系。方法 PCR及DNA直接测序法对新疆80例恶性黑素瘤及30例正常皮肤石蜡包埋组织BRAF基因11、15外显子进行检测。结果 80例恶性黑素瘤19例发生BRAF基因突变,突变率为23.8%（19/80）;有17例突变发生于15外显子,突变率为89.5% （17/19）,其中V600E突变占BRAF基因15外显子突变的88.2% （15/17）;2例突变位于11外显子,突变率10.5%（2/19）;30例正常皮肤组织均未发现BRAF基因突变。患者平均发病年龄为57.5岁,年龄在60岁以下患者BRAF基因突变率显著高于60岁以上（χ2 = 6.613,P < 0.05）。黏膜、肢端、非肢端突变率分别为：18.2%（4/21）,14.7%（5/34）,41.7%（10/24）,差异具有统计学意义（χ2 = 6.167,P < 0.05）。BRAF基因突变与恶性黑素瘤患者性别、民族、有无淋巴结转移无明显相关性（P > 0.05）。结论 BRAF基因仍为新疆地区恶性黑素瘤热点突变基因,且以该基因15外显子V600E突变为主。BRAF基因突变与恶性黑素瘤患者发病年龄、发病部位密切相关,而与民族、性别、有无淋巴结转移无相关性。     

恶性黑素瘤中BRAF癌基因突变研究新进展

恶性黑素瘤是死亡率较高的皮肤肿瘤之一,研究发现恶性黑素瘤中存在高频BRAF癌基因突变.紫外线是引起突变的高危因素,不同种族、发病部位以及病理类型的恶性黑素瘤间BRAF突变率存在差异.此突变与遗传、预先存在的色素痣、肿瘤侵袭性及预后之间的关系还存在争论.BRAF突变相关的MAPK信号传导分子是治疗恶性黑素瘤的靶点.综述近几年的研究,以认识BRAF突变与恶性黑素瘤的关系.     

黑素瘤相关通路及治疗的新进展

黑素瘤的发病机制与遗传、环境因素如紫外线长期照射有关.研究表明,黑素瘤的发生发展主要与细胞外调节蛋白激酶通路和磷酸酰肌醇3激酶/蛋白激酶/哺乳动物雷帕霉素靶蛋白信号通路改变相关.相关的基因改变有:BRAF基因、NRAS基因、GNAQ基因和GNA 11基因、C-kit基因、苏氨酸蛋白激酶基因等.黑素瘤是皮肤侵袭性肿瘤,对于放疗和化疗均不敏感.针对黑素瘤发病机制的分子靶向治疗发挥了重要的作用,包括免疫治疗、基因治疗以及针对肿瘤血供的治疗.生物治疗比传统治疗有更好的靶向性和特异性.     

不同病理类型及种族恶性黑素瘤遗传学差异

恶性黑素瘤是一种起源于黑素细胞的高度恶性肿瘤,在西方国家的发病率很高,但对于发病率相对较低的黄种人及其他有色人种,黑素瘤的常见病理类型和相应的遗传学改变和分子机制有很大的不同.白种人常见的病理类型是非慢性阳光损伤型恶性黑素瘤,遗传学上以BRAF和NRAS基因突变多见,亚洲人及其他有色人种常见的病理类型是肢端型及黏膜型恶性黑素瘤,以kit变异和CCND1扩增多见.通过对不同病理类型的恶性黑素瘤的遗传学改变的研究,有助于疾病的早期基因诊断和靶向治疗药物的研发.     

皮肤恶性黑素瘤的易感基因

皮肤恶性黑素瘤是一种多因素相关疾病 ,遗传因素与其密切相关。目前 ,两个高风险性皮肤恶性黑素瘤易感基因%D细胞周期素依赖性激酶抑制剂 2A和细胞周期蛋白依赖性激酶 4已被确认 ,而基因p14 ARF和细胞周期素D1基因也可能起一定作用。另外 ,由于发现有染色体 9p2 1不相关家族 ,故其他高风险性基因也可能存在。黑皮质素受体 - 1已确认为低风险黑素瘤易感基因。目前的研究是为了明确其他易感基因及其作用     

BRAF基因突变与皮肤恶性黑素瘤

BRAF基因,位于染色体7q34编码一个67 000～99 000的丝,苏氨酸蛋白激酶,其产物在丝裂原活化蛋白激酶信号途径中起重要调控作用.国内外的研究者先后发现并揭示出BRAF基因变异与皮肤恶性黑素瘤的关系.随着探索的深入,部分学者以BRAF基因作为治疗靶向进行研究,并初步取得成果.对BRAF基因及其突变的研究可能在未来恶性黑素瘤诊断、治疗以及预后等方面产生临床价值,为恶性黑素瘤的治疗开辟新的方向.     

皮肤恶性黑素瘤的易感基因

皮肤恶性黑素瘤是一种多因素相关疾病，遗传因素与其密切相关。目前，两个高风险性皮肤恶性黑素瘤易感基因一细胞周期素依赖性激酶抑制剂2A和细胞周期蛋白依赖性激酶4已被确认．而基因p14^ARF和细胞周期素D1基因也可能起一定作用。另外，由于发现有染色体9p21不相关家族，故其他高风险性基因也可能存在。黑皮质素受体-1已确认为低风险黑素瘤易感基因。目前的研究是为了明确其他易感基因及其作用。     

BRAF基因突变与皮肤恶性黑素瘤

BRAF基因,位于染色体7q34编码一个67 000～99 000的丝,苏氨酸蛋白激酶,其产物在丝裂原活化蛋白激酶信号途径中起重要调控作用.国内外的研究者先后发现并揭示出BRAF基因变异与皮肤恶性黑素瘤的关系.随着探索的深入,部分学者以BRAF基因作为治疗靶向进行研究,并初步取得成果.对BRAF基因及其突变的研究可能在未来恶性黑素瘤诊断、治疗以及预后等方面产生临床价值,为恶性黑素瘤的治疗开辟新的方向.     

BRAF基因突变与皮肤恶性黑素瘤

BRAF基因,位于染色体7q34编码一个67 000～99 000的丝,苏氨酸蛋白激酶,其产物在丝裂原活化蛋白激酶信号途径中起重要调控作用.国内外的研究者先后发现并揭示出BRAF基因变异与皮肤恶性黑素瘤的关系.随着探索的深入,部分学者以BRAF基因作为治疗靶向进行研究,并初步取得成果.对BRAF基因及其突变的研究可能在未来恶性黑素瘤诊断、治疗以及预后等方面产生临床价值,为恶性黑素瘤的治疗开辟新的方向.     

RAS and RAF mutations in banal melanocytic aggregates contiguous with primary cutaneous melanoma: clues to melanomagenesis

Background  Distinguishing banal melanocytic aggregates contiguous with malignant melanoma can be a histological challenge but is essential because of the potential for a spurious Breslow measurement.
Objectives  Our aim was to ascertain whether the histological distinction between the two relates to differences in the prevalence of mutations in genes significant in melanomagenesis.
Methods  Mutations in BRAF codon 600, NRAS1 codons 12/13, NRAS2 codons 60/61 and KRAS codons 12/13 were ascertained in 18 cases of primary cutaneous malignant melanoma contiguous with banal melanocytic aggregates using laser capture microdissection.
Results  Overall, 12 of 18 cases (67%) exhibited a mutation in at least one gene. BRAF  V600E appeared to be the most commonly mutated gene in both the melanocytic aggregate (seven of 18, 39%) and the melanoma (four of 18, 22%). Both populations demonstrated a similar BRAF genomic profile in 11 of 18 cases (61%) (two BRAF  V600E, nine BRAF -WT), a similar KRAS genomic profile in 14 of 18 cases (78%) (one KRAS  G12V, 13 KRAS- WT) and a similar NRAS2 genomic profile in 14 of 18 cases (all WT). Of interest, we noted a relatively high prevalence of KRAS mutations (five of 18, 28%). The frequency of KRAS mutations in the melanocytic aggregate (five of 18, 28%) was second to BRAF  V600E, while in melanoma, the frequency was also second to BRAF  V600E but equalled that of NRAS2 (1 of 18, 6%). No NRAS1 mutations were observed. BRAF and RAS mutations appeared to be mutually exclusive with only three of 18 cases (17%) demonstrating a mutation in both genes (melanocytic aggregate only).
Conclusions  Our findings hint towards the interpretation of banal melanocytic aggregates serving as precursor lesions.     

BRAF point mutations in primary melanoma show different prevalences by subtype

To elucidate the biological significance of activating mutations of BRAF in human malignant tumors, we performed a mutation analysis using 43 cell lines established from tumors that had developed in several kinds of human organs. Because the same V599E point mutation was observed in three of six melanoma cell lines and no such mutations were observed in other types of cancers, we focused further on melanoma, performed mutation analyses of NRAS, KRAS, CTNNB1, and p16/p14(ARF) in these cell lines, and found one NRAS mutation and three p16/p14(ARF) mutations. We further searched for mutations of BRAF and NRAS in 35 primary sporadic melanomas from 35 Japanese patients and detected the V599E BRAF point mutation in only nine (26%) of them. Significant differences in mutation frequency were observed among four histological subtypes; four (50%) of eight superficially spreading melanoma and five (33%) of 15 acral lentiginous melanoma had the mutation, whereas none of 12 other types (six nodular melanoma, five lentigo melanoma, and one mucosal melanoma) had it. The BRAF mutation was observed frequently even in small lesions, indicating that activation of this gene may be one of the early events in the pathogenesis of some melanomas.     

Genetic interaction between NRAS and BRAF mutations and PTEN/MMAC1 inactivation in melanoma

Extant evidence implicates growth factor signaling in the pathogenesis of many tumor types, including cutaneous melanoma. Recently, reciprocal activating mutations of NRAS and BRAF were found in benign melanocytic nevi and cutaneous melanomas. We had previously reported a similar epistatic relationship between activating NRAS mutations and inactivating PTEN/MMAC1 alterations. We thus hypothesized that BRAF and PTEN/MMAC1 mutations may cooperate to promote melanoma tumorigenesis. Overall, 40 of 47 (85%) melanoma cell lines and 11 of 16 (69%) uncultured melanoma metastases had mutations in NRAS, BRAF, or PTEN/MMAC1. NRAS was exclusively mutated in nine of 47 (19%) cell lines and two of 16 (13%) metastases, whereas BRAF was solely mutated in 28 of 47 (60%) cell lines and nine of 16 (56%) metastases. In the 12 of 15 melanoma cell lines (80%) and two of two melanoma metastases with PTEN alterations, BRAF was also mutated. These findings suggest the existence of possible cooperation between BRAF activation and PTEN loss in melanoma development.     

BRAF and NRAS mutations are frequent in nodular melanoma but are not associated with tumor cell proliferation or patient survival

Previous studies have shown frequent mutations in the BRAF (V-raf murine sarcoma viral oncogene homolog B1) or NRAS (neuroblastoma RAS viral [V-ras] oncogene homolog) genes in cutaneous melanoma, but the relationship between these alterations and tumor cell proliferation has not been examined in human melanoma. In our study of 51 primary nodular melanomas and 18 paired metastases, we found mutations in BRAF (codon 600, previously denoted 599) in 15 primary tumors (29%) and eight metastases (44%). The figures for NRAS mutations were 27% and 22%, respectively. Mutations in BRAF and NRAS genes were mutually exclusive in all but one case, and were maintained from primary tumors through their metastases. Mutations, however, were not associated with tumor cell proliferation by Ki-67 expression, tumor thickness, microvessel density, or vascular invasion, and there were no differences in patient survival. Although BRAF and NRAS mutations are likely to be important for the initiation and maintenance of some melanomas, other factors might be more significant for proliferation and prognosis in subgroups of aggressive melanoma.     

Phospho-ERK staining is a poor indicator of the mutational status of BRAF and NRAS in human melanoma

Mutated BRAF and NRAS are suspected to contribute to melanomagenesis by activation of extracellular signal-regulated kinase (ERK). To test this notion, we analyzed the presence of phosphorylated ERK1/2 in 170 melanomas with established NRAS/BRAF mutational status and well-documented clinical follow-up by immunohistochemistry. Several notable observations were obtained: (i) phospho-ERK staining was very heterogeneous within the tumor; (ii) in most cases, ERK was phosphorylated in only a minority of tumor cells; (iii) the percentage of phospho-ERK-positive cells was not correlated with the mutational status of NRAS and/or BRAF; (iv) the Raf kinase inhibitor protein (RKIP) was expressed homogeneously in virtually all melanoma samples not reflecting the inhomogeneity of phospho-ERK; and, finally, (v) neither the portion of phospho-ERK-positive tumor cells nor the RKIP staining intensity showed any correlation to the clinical course of the patients. Furthermore, the ability of BRAF mutant melanoma cells to downregulate mitogen-activated protein kinase activation was shown in melanoma cell lines cultured at high densities or under nonadherent conditions. Our findings suggest that mitogen-activated protein kinase (MAPK) activity is subject to regulation even in BRAF/NRAS mutant melanoma cells and that high MAPK pathway signaling may be important only in distinct subsets of tumor cells.     

Examination of mutations in BRAF, NRAS, and PTEN in primary cutaneous melanoma

Frequent somatic mutation of v-raf murine sarcoma viral oncogene homolog B (BRAF), a downstream effector of the rat sarcoma oncogene (RAS) signaling pathway, is described in melanoma and other tumors. Our analysis of melanoma cell lines suggests that activating mutations in BRAF can occur simultaneously with inactivation of phosphatase and tensin homolog (PTEN), but neuroblastoma RAS (NRAS) mutations are not coincident. We determined the concurrent prevalence of mutations in BRAF and NRAS, and alteration of PTEN expression in 69 primary cutaneous melanomas. BRAF mutations were seen in 57% of cases. NRAS was mutated in 17% of samples, exclusively in exon 2. Two cases showed concurrent BRAF and NRAS mutations. Using immunohistochemistry, PTEN protein expression was lost or greatly reduced in 19% of tumors. Seven tumors with reduced PTEN yielded DNA amenable to sequencing, and three also showed mutation in BRAF but none in NRAS. In all, 11 (85%) of 13 tumors showing reduced PTEN expression were greater than 3.5 mm thick, and the association of increasing Breslow thickness and loss or reduction of PTEN expression was statistically significant (P<0.0001). Mutations in NRAS were not coincident with reduced PTEN expression, and the concurrent mutation of NRAS and BRAF was rare.     

MicroRNAs in the pathogenesis of malignant melanoma

Cutaneous malignant melanoma is the most aggressive and lethal form of skin cancer. Over the past decades, its incidence has been increasing by 3–8% per year in western countries while mortality has stabilized. Melanoma is a heterogenous disease and can be subclassified based on distinct clinical characteristics, histopathological features and mutation patterns within NRAS and BRAF genes. Recent data indicate that microRNAs (miRNAs) are involved in the pathogenesis of malignant melanoma. MiRNAs are small, non‐coding, regulatory RNA molecules expressed in a tissue and cell specific manner and are known to play a crucial role in cell homeostasis and carcinogenesis. MiRNAs might prove to be powerful cancer biomarkers and future therapeutic targets. In this review, we focused on the miRNA involvement in four molecular pathways known to be deregulated in malignant melanoma, including the RAS‐RAF‐MEK‐ERK pathway, the p16^INK4A‐CDK4‐RB pathway, the PIK3‐AKT pathway and the MITF pathway.     

Low prevalence of RAS-RAF-activating mutations in Spitz melanocytic nevi compared with other melanocytic lesions

Melanocytic lesions, including Spitz nevi (SN), common benign nevi (CBN) and cutaneous metastatic melanoma (CMM), were analyzed for activating mutations in NRAS, HRAS and BRAF oncogenes, which induce cellular proliferation via the MAP kinase pathway. One of 22 (4.5%) SN tested showed an HRAS G61L mutation. Another lesion, a 'halo' SN, showed a BRAF V600E (T1796A) mutation. BRAF V600E mutations were found in two thirds (20/31) of CBN, while a further 19% (6/31) showed NRAS codon 61 mutations. One third of CMM (10/30) had various BRAF mutations of codon 600, and a further 6% (2/31) showed NRAS codon 61 mutations. Seventeen SN tested for loss of heterozygosity (LOH) at 9p and 10q regions, known to be frequently deleted in melanoma, showed LOH at the 9p loci D9S942 and IFNA. A further lesion was found with low-level microsatellite instability at one locus, D10S214. The low rate of RAS-RAF mutations (2/22, 9.1%) observed in SN suggests that these lesions harbor as yet undetected activating mutations in other components of the RAS-RAF-MEK-ERK-MAPK pathway. Germline DNA from members of 111 multiple-case melanoma families, representing a range of known (CDKN2A) and unknown predisposing gene defects, was analyzed for germline BRAF mutations, but none was found.     

Chromosomal translocations as a mechanism of BRAF activation in two cases of large congenital melanocytic nevi

Genetic studies of melanocytic tumors have mainly demonstrated activation of oncogenes such as NRAS or BRAF through point mutations. In two cases of large congenital melanocytic nevi, we observed a chromosomal translocation involving the BRAF oncogene on chromosome 7q34, resulting in both cases in removal of the auto-inhibitory N-terminal regulatory domain (hence the Ras-guanosine triphosphate binding domain) of BRAF from its protein kinase domain. This is early evidence of BRAF activation through chromosomal translocation in melanocytic tumors. Because BRAF point mutations are rather rare in congenital melanocytic nevi and melanoma arising in non-sun-exposed area, the molecular mechanism of oncogenic activation as described here could be a recurrent molecular feature in these groups of melanocytic tumors.     

Congenital melanocytic nevi frequently harbor NRAS mutations but no BRAF mutations

Most melanocytic nevi develop on sun-exposed skin during childhood and adolescence and commonly harbor BRAF mutations or, less frequently, NRAS mutations. A small subset of nevi is present at birth, and therefore must develop independently of UV light. To assess whether these nevi have a different mutation spectrum than those that develop on sun-exposed skin, we determined the BRAF and NRAS mutation frequencies in 32 truly congenital nevi. We found no BRAF mutations, but 81% (26/32) harbored mutations in NRAS. Consistently, seven of 10 (70%) proliferating nodules that developed early in life in congenital nevi showed mutations in NRAS. A separate set of nevi that displayed histological features frequently found in nevi present at birth ("congenital pattern nevi") but lacked a definitive history of presence at birth showed an inverse mutation pattern with common BRAF mutations (20/28 or 71%) and less frequent NRAS mutations (7/28 or 25%). Thus, nevi that develop in utero are genetically distinct from those that develop later, and histopathologic criteria alone are unable to reliably distinguish the two groups. The results are consistent with the finding in melanoma that BRAF mutations are uncommon in neoplasms that develop in the absence of sun-exposure.