BRAF point mutations in primary melanoma show different prevalences by subtype

Methylation and mutation of the inhibin‑α gene in human melanoma cells and regulation of PTEN expression and AKT/PI3K signaling by a demethylating agent

Inhibin suppresses the pituitary secretion of follicle‑stimulating hormone and has been reported to act as a tumor suppressor gene in the gonad in mice. Epigenetic modifications, mutations, changes in the loss of heterozygosity (LOH) of the inhibin‑α gene and regulation of gene expression in response to a demethylating agent [5‑aza‑2'‑deoxycytidine (5‑Aza‑dC)] in human melanoma cells were assessed. In addition, the association between a mutation in the 5'‑untranslated region (5'‑UTR) of the inhibin‑α subunit and the expression of phosphatidylinositol 3,4,5‑trisphosphate‑dependent Rac exchanger 2 (PREX2) and phosphatase and tensin homolog (PTEN) as well as AKT/PI3K signaling was determined. The methylation status of the CpG sites of the inhibin‑α promoter was analyzed by methylation‑specific PCR in bisulfite‑treated DNA. Cell viability was counted using the trypan blue assay, mRNA expression was examined via reverse transcription‑quantitative PCR, and protein expression was examined via western blot analysis. The inhibin‑α promoter was hypermethylated in G361, SK‑MEL‑3, SK‑MEL‑24 and SK‑MEL‑28 cells and moderately methylated in SK‑MEL‑5 cells. Inhibin‑α gene mutations were observed in the 5'‑UTR exon 1 of G361, SK‑MEL‑5, SK‑MEL‑24 and SK‑MEL‑28 cells as well as in exon 2 of SK‑MEL‑3 cells. Allelic imbalance, including LOH, in the inhibin‑α gene was detected in human melanoma cells. Treatment with 5‑Aza‑dC increased inhibin‑α mRNA and protein levels, inhibited cell proliferation, and delayed the doubling times of surviving melanoma cells. In 5‑Aza‑dC‑treated cells, PREX2 protein expression was slightly increased in G361 and SK‑MEL‑24 cells and decreased in SK‑MEL3, SK‑MEL‑5 and SK‑MEL‑28 cells. However, the protein expression of PTEN was decreased in melanoma cells. In addition, AKT and PI3K protein phosphorylation levels increased in all melanoma cells, except of G361 cells, demonstrating decreased PI3K protein phosphorylation. These data provided evidence that methylation, mutation and LOH are observed in the inhibin α‑subunit gene and gene locus in human melanoma cells. Furthermore, the demethylating agent reactivated inhibin‑α gene expression and regulated PREX2 expression. AKT/PI3K signaling increased as PTEN expression decreased. In addition, mutations in the tumor suppressor inhibin‑α, PTEN and p53 genes were not associated with transcriptional silencing, gene expression and cell growth as analyzed through experiments and literature reviews. These data demonstrated that methylation and mutations were associated with the inhibin‑α gene in human melanoma cells and indicated the regulation of PTEN expression and AKT/PI3K signaling by a demethylating agent.

Single-Cell RNA Sequencing Unravels Heterogeneity of the Stromal Niche in Cutaneous Melanoma Heterogeneous Spheroids

Heterogeneous spheroids have recently acquired a prominent position in melanoma research because they incorporate microenvironmental cues relevant for melanoma. In this study, we focused on the analysis of microenvironmental factors introduced in melanoma heterogeneous spheroids by different dermal fibroblasts. We aimed to map the fibroblast diversity resulting from previously acquired damage caused by exposure to extrinsic and intrinsic stimuli. To construct heterogeneous melanoma spheroids, we used normal dermal fibroblasts from the sun-protected skin of a juvenile donor. We compared them to the fibroblasts from the sun-exposed photodamaged skin of an adult donor. Further, we analysed the spheroids by single-cell RNA sequencing. To validate transcriptional data, we also compared the immunohistochemical analysis of heterogeneous spheroids to melanoma biopsies. We have distinguished three functional clusters in primary human fibroblasts from melanoma spheroids. These clusters differed in the expression of (a) extracellular matrix-related genes, (b) pro-inflammatory factors, and (c) TGFβ signalling superfamily. We observed a broader deregulation of gene transcription in previously photodamaged cells. We have confirmed that pro-inflammatory cytokine IL-6 significantly enhances melanoma invasion to the extracellular matrix in our model. This supports the opinion that the aspects of ageing are essential for reliable melanoma 3D modelling in vitro.

BRAF, KIT, and NRAS Mutations of Acral Melanoma in White Patients

OBJECTIVES

Malignant acral melanoma (AM) is relatively infrequent in white patients. Molecular investigations have returned variable results regarding the mutational pattern. We sought to describe the mutation profile and clinicopathologic features of AM.

METHODS

We investigated BRAF, KIT, and NRAS mutational status in a series of 31 AM samples from white patients.

RESULTS

Nodular melanoma was the most common histopathologic subtype (48.4%), followed by acral lentiginous melanoma (25.8%) and superficial spreading melanoma (25.8%). BRAF, KIT, and NRAS mutational rates were 12.9%, 17.2%, and 30.0%, respectively. We observed significant associations between KIT mutational status and a thinner Breslow thickness compared with wild-type (WT) status (P = .002), NRAS mutation status and younger age compared with WT. In patients presenting at least one mutation, triple-WT patients presented metastases most frequently.

CONCLUSIONS

Although these data represent preliminary results, better knowledge of tumor biology and prognosis of AM can support the clinical approach and follow-up.

Depletion of primary cilium in acral melanoma

BACKGROUND

A eukaryotic cell's primary cilium (PC) is critical for cell signaling, migration and homeostasis. Primary cilium dysfunction has been demonstrated in several malignancies, but whether primary cilia loss occurs in acral melanoma has remained unknown. To address this, we examined the ciliation index (% melanocytes containing a PC) of patient-derived, biopsy-proven acral melanoma and compared these to benign acral nevi.

METHODS

We generated a pilot initiative study that included six acral melanomas and seven acral nevi derived from the foot. Using fluorescent immunohistochemistry, we calculated ciliation indexes of Sox10+ melanocytes.

RESULTS

Average ciliation index for acral nevi was 74.0% (SE of the mean [SEM] 3.3%) vs 9.3% for acral melanoma (SEM 5.7%), finding a statistically significant difference between the groups (P-value <.001, two tailed t test).

CONCLUSION

The data show a significant loss of primary cilia in malignant acral melanoma vs benign acral nevi, suggesting that cilia may play an important role during acral melanoma formation. Our data, which should be validated by a larger study with longer follow-up period, suggest that examining ciliation index may be a useful diagnostic test when distinguishing benign acral nevi from melanoma.

Molecular evaluation of BRAF V600 mutation and its association with clinicopathological characteristics: First findings from Indian malignant melanoma patients

Mutations in the BRAF gene have been described to occur in two-third of melanomas. The objective of the study was to establish the frequency of BRAF V600E/K/R mutation in a series of melanomas from Indian origin and to correlate mutation status with clinicopathological features. Seventy melanoma cases were evaluated for BRAF V600 mutation by pyrosequencing. Overall, BRAF mutations were detected in 30% of the patients. All mutations observed were missense type (GTG > GAG) resulting in p.V600E, while none showed V600K/R mutation. The frequency of BRAF V600E mutations were more in patients with onset age of 50 years. BRAF mutations were significantly associated with tumor site wherein more mutations were seen in tumors from head and neck and extremities region. Acral and mucosal tumor subtype showed a mutation frequency of 31% and 20%, respectively. Epithelial cell morphology tends to harbor frequent BRAF V600E mutation (36%) than other morphological subtypes. Tumors with ulceration and necrosis showed increased BRAF mutation rate (32.5% and 33%) respectively. In conclusion, this is the first study to report a mutation frequency of 30% in this cohort. Our results demonstrated that the BRAF V600E mutation is a frequent event in Indian melanomas, and represents an important molecular target for novel therapeutic approaches.

Acral melanoma: correlating the clinical presentation to the mutational status

Acral lentiginous melanoma (ALM) is the most common type of malignant melanoma (MM) in Asians, Afro-Americans and Middle-Easterners. It represents 1.5-10% of all MM cases, being the most common histological type of MM arising on palms, soles and nail apparatus, which is more generically defined as acral MM. To date no risk factors have been officially established, however a history of trauma may be involved in the pathogenesis of acral MM. This shows heterogeneous clinical features and frequently presents with advanced stage and aggressive behavior, often as a result of misdiagnosis or delayed identification. Dermoscopy is helpful for an early diagnosis of ALM: the most characteristic dermoscopic patterns are the parallel ridge and the irregular diffuse pigmentation. On histopathology ALM displays a lentiginous growth pattern, with melanocytes arranged as solitary units along the basilar epidermis, without notable pagetoid growth in the early stage. Not all acral MMs present a lentiginous pattern: superficial spreading melanoma and nodular melanoma patterns are also possible. Novel studies investigating the biologic characteristics of acral MM reported variable results: the overall mutational rates ranged respectively between 8.5% and 23% for KIT, between 3.6% and 33.3% for BRAF and between 3% and 47% for NRAS in ALMs. Increasing attention has been recently given to other genes, such as telomerase reverse transcriptase, platelet-derived growth factor receptor alfa and cyclin D1. Larger molecular investigations urge to describe the molecular profile of acral MM, to allow the development of specific targeted therapies.

Aberrations and clinical significance of BRAF in malignant melanoma: A series of 60 cases in Chinese Uyghur

Malignant melanoma (MM) is a highly malignant melanocytic tumor, it occurs mostly in the skin, the mucous membrane close to the skin, but also in the tunicae rhagoides and the pia mater. The Uyghur is the largest ethnic group living in the Xinjiang Uyghur Autonomous Region of China, accounting for 46% of the total population of 20 million. Large-scale studies on MMs in Asian countries are limited. This study aimed to investigate BRAF mRNA expression and mutations in Chinese Uyghur patients with MMs and to identify the clinical features associated with these parameters.Formalin-fixed, paraffin wax-embedded tumor sections from 60 MMs were analyzed for BRAF expression using reverse transcription polymerase chain reaction (RT-PCR). Exons 11 and 15 of BRAF were analyzed for the presence of mutations using PCR and DNA sequencing. Sixty MMs were followed by mobile phone for survival analysis.BRAF mRNA expression was higher in MMs than in pigmented moles and normal skin tissues. Fourteen of 60 MMs had BRAF mutations. The frequency of BRAF mutations was significantly higher in patients younger than 60 years (10/28, 4/32, P = .02). A significant difference was observed in the frequency of BRAF mutations among specimens of mucosal, acral, chronic sun-induced damage (CSD), and non-CSD MMs (2/10, 3/19, 8/25, 1/6, P = .002). No significant association was found among BRAF mutations, sex, ulceration, or lymph node metastasis. MMs lymph node metastasis (hazard ratio 2.54 [95% confidence interval 1.062 - 6.066], P = .01) affected survival.This study indicated that BRAF mutations and expression might serve as independent adverse prognostic factors in melanoma.

Kinase gene fusions in defined subsets of melanoma

Genomic rearrangements resulting in activating kinase fusions have been increasingly described in a number of cancers including malignant melanoma, but their frequency in specific melanoma subtypes has not been reported. We used break-apart fluorescence in situ hybridization (FISH) to identify genomic rearrangements in tissues from 59 patients with various types of malignant melanoma including acral lentiginous, mucosal, superficial spreading, and nodular. We identified four genomic rearrangements involving the genes BRAF, RET, and ROS1. Of these, three were confirmed by Immunohistochemistry (IHC) or sequencing and one was found to be an ARMC10-BRAF fusion that has not been previously reported in melanoma. These fusions occurred in different subtypes of melanoma but all in tumors lacking known driver mutations. Our data suggest gene fusions are more common than previously thought and should be further explored particularly in melanomas lacking known driver mutations.

MAP Kinase Pathways: Molecular Roads to Primary Acral Lentiginous Melanoma

The etiology and pathogenesis of lentiginous acral melanomas are poorly understood. Recent studies have postulated that DNA repair mechanisms and cell growth pathways are involved in the development of melanoma, particularly changes in the MAPK pathways (RAS, BRAF, MEK 1/2, and ERK 1/2). The aim of this study is to assess the status of the MAP kinase pathways in the pathogenesis of acral melanomas. The authors examined the components of the RAS–RAF–MEK–ERK cascades by immunohistochemistry in a series of 16 primary acral melanomas by tissue microarray. The expression of MAP kinase cascade proteins changed in most cases. The authors observed that 57.14% of cases were BRAF positive and that 61.53%, 71.42%, and 71.42% of cases were positive for MEK2, ERK1, and ERK2, respectively; RAS was not expressed in 92.31%, and all cases were negative for MEK1. The absence of RAS and positivity for MEK2, ERK1, and ERK2 were most seen in invasive cases with high thickness. These aspects of the MAPK pathway require further examination in acral melanomas between different populations. Nevertheless, the results highlight significant alterations in the MAP kinase cascades that are related to histological indicators of prognosis in primary acral melanomas.

Molecular profiling, including TERT promoter mutations, of acral lentiginous melanomas

Acral lentiginous melanoma (ALM) is the less common subtype with singular characterization. TERT (human telomerase reverse transcriptase) promoter mutations have being described as recurrent in melanomas and infrequent in ALM, but their real incidence and clinical relevance is unclear. The objectives of this study were to describe the prevalence of TERT promoter mutations in ALM, and correlate with the molecular profile of other drive genes and clinical features. Sixty-one samples from 48 patients with ALM were analyzed. After DNA isolation, the mutation profiles of the hotspot region of BRAF, NRAS, KIT, PDGFRA, and TERT genes were determined by PCR amplification followed by direct Sanger sequencing. KIT, PDGFRA, and VEGFR2 gene amplification was performed by quantitative PCR. Clinical information such as survival, clinical stage, and Breslow tumor classification were obtained from medical records. TERT promoter mutations were found in 9.3% of the cases, BRAF in 10.3%, NRAS in 7.5%, KIT in 20.7%, and PDGFRA in 14.8% of ALM. None of the cases showed KIT, PDGFRA, or VEGFR2 gene amplification. We found an association between KIT mutations and advanced Clark level (IV and V, P=0.043) and TERT promoter mutations with low mitotic index. No other significant associations were observed between mutation profile and patients' clinical features nor survival rates. Oncogenic TERT promoter mutations are present in a fraction of ALMs. No relevant associations were found between TERT mutation status and clinical/molecular features nor survival. Mutations of KIT and PDGFRA are the most common genetic alterations, and they can be therapeutic targets for these patients.

Prevalence of BRAF and NRAS mutations in cutaneous melanoma patients in Taiwan

BACKGROUND/PURPOSE

BRAF and NRAS mutations have been described in melanomas among Caucasians and some Asian populations. However, few large-scale studies have investigated the status and clinical significance of BRAF and NRAS mutations in a Taiwanese population.

METHODS

Melanoma samples (n = 119) were analyzed for mutations in exons 11 and 15 of the BRAF gene, and in exons 1 and 2 of the NRAS gene. The samples were studied in genomic DNA, using polymerase chain reaction amplification and Sanger sequencing. Mutations of the BRAF and NRAS genes were then correlated with clinicopathological features and patients' prognosis.

RESULTS

The incidence of somatic mutations within the BRAF and NRAS genes was 14.3% (17/119 patients) and 10.1% (12/119 patients), respectively. Among the 17 patients with BRAF mutations, 15 (88.2%) had V600E mutations. BRAF mutation was frequently detected in younger patients (p = 0.0035), in thin melanomas (p = 0.0181), and in melanomas with less ulceration (p = 0.0089). NRAS mutation was more often seen in patients with lymph node metastasis (p = 0.0332). Both BRAF and NRAS mutations were not significantly correlated with overall survival and disease-free survival.

CONCLUSION

As BRAF and NRAS mutations are rare in Taiwan, BRAF- or NRAS-targeted therapies may be effective only for selected Taiwanese melanoma patients.

BRAF V600 mutations and pathological features in Japanese melanoma patients

Ultraviolet radiation is a risk factor for BRAF V600 mutations frequently found in melanomas that cause constitutive BRAF activation. Primary sites of melanoma and the frequency of BRAF mutations might differ between races. Melanoma is rare in Japan (1500–2000 cases/year compared with 132 000/year worldwide) and the frequency and distribution of BRAF V600 mutations are unknown. We aimed to investigate the frequency of BRAF V600 mutations in a cohort of Japanese patients with melanoma and determine the relationship between mutations and clinical/pathologic features. DNA was extracted from 80 formalin-fixed, paraffin-embedded tumours from individuals diagnosed with melanoma. BRAF V600 mutations were detected using the Cobas 4800 System with z480 Analyzer and Cobas 4800 BRAF V600 Mutation Test reagents. BRAF V600 mutations were detected in 41.8% of tested tumours, with an invalid rate of 1.3%. The mutation rate was more than 60% in patients aged less than 60 years and more than 36% in patients with stage III/IV disease. No sex difference in the mutation rate was observed. BRAF V600 mutations were detected in 18.8% of acral lentiginous melanomas (ALMs), 64.7% of superficial spreading melanomas, 50.0% of lentigo maligna melanomas and 20.0% of nodular melanomas. Although the mutation rate was low in ALMs, 36.4% were mutation positive at stage III/IV compared with 9.5% at stage I/II. This study confirmed associations among BRAF V600 mutations, pathological features and subtypes of melanoma. BRAF V600 mutations were more frequent in late-stage ALMs than in early-stage ALMs. Superficial spreading melanomas had similar mutation rates at all stages. These insights suggest improved treatment predictions for stage III/IV melanoma patients.

Mutational dichotomy in desmoplastic malignant melanoma corroborated by multigene panel analysis

Desmoplastic malignant melanoma is a distinct melanoma entity histologically subtyped into mixed and pure forms due to significantly reduced lymph node metastases in the pure form. Recent reports investigating common actionable driver mutations have demonstrated a lack of BRAF, NRAS, and KIT mutation in pure desmoplastic melanoma. In search for alternative driver mutations next generation amplicon sequencing for hotspot mutations in 50 genes cardinal to tumorigenesis was performed and in addition the RET G691S polymorphism was investigated. Data from 21 desmoplastic melanomas (12 pure and 9 mixed) were retrieved. Pure desmoplastic melanomas were either devoid of mutations (50%) or displayed mutations in tumor suppressor genes (TP53, CDKN2A, and SMAD4) singularly or in combination with the exception of a PIK3CA double-mutation lacking established biological relevance. Mixed desmoplastic melanomas on the contrary were frequently mutated (89%), and 67% exhibited activating mutations similar to common-type cutaneous malignant melanomas (BRAF, NRAS, FGFR2, and ERBB2). Separate analysis of morphologically heterogeneous tumor areas in four mixed desmoplastic malignant melanomas displayed no difference in mutation status and RET G691 status. GNAQ and GNA11, two oncogenes in BRAF and NRAS wild-type uveal melanomas, were not mutated in our cohort. The RET G691S polymorphism was found in 25% of pure and 38% of mixed desmoplastic melanomas. Apart from RET G691S our findings demonstrate absence of activating driver mutations in pure desmoplastic melanoma beyond previously investigated oncogenes (BRAF, NRAS, and KIT). The findings underline the therapeutic dichotomy of mixed versus pure desmoplastic melanoma with regard to activating mutations primarily of the mitogen-activated protein kinase pathway.

Metaanalysis of BRAF mutations and clinicopathologic characteristics in primary melanoma

BACKGROUND

BRAF mutations occur in some melanomas. We hypothesized that BRAF mutation rates may differ in melanomas found in Asian compared to white populations.

OBJECTIVE

We performed a metaanalysis of BRAF mutations and their associations with the clinicopathologic characteristics of primary melanoma (PM), with a subgroup analysis to compare Asian and white patients with PM.

METHODS

The PubMed, EMBASE, and Cochrane databases were searched up to November 2013. The incidence rates and odds ratios (ORs) of BRAF mutations were calculated using a fixed or random effects model.

RESULTS

BRAF mutation was associated with younger age (OR = 1.734; P < .001), trunk location (OR = 2.272; P < .001), non-chronically sun damaged skin (OR = 2.833; P < .001), superficial spreading melanoma (OR = 2.081; P < .001), and advanced melanoma stage (OR = 1.551; P = .003). The incidence of BRAF mutations in Asian patients with PM was half that of white patients with PM, but it was linked to the same clinicopathologic characteristics.

LIMITATIONS

Only a small number of studies have been conducted on Asian patients with PMs.

CONCLUSIONS

The BRAF mutation in PM was associated with age, anatomic site based on ultraviolet radiation exposure, histologic subtype, and advanced stage of melanoma. The clinicopathologic associations with BRAF mutations were similar in Asian and white patients with PM.

Diagnosis and management of lentigo maligna: a review

Lentigo maligna is a melanocytic neoplasm occurring on sun-exposed skin, usually on the head and neck, of middle-aged and elderly patients. It is thought to represent the in situ phase of lentigo maligna melanoma. The ill-defined nature and potentially large size of lesions can pose significant diagnostic and treatment challenges. The goal of therapy is to cure the lesions in order to prevent development of invasive disease, and surgical excision is the treatment of choice to achieve clear histological margins. Nonsurgical treatment modalities have been reported; however, evidence is lacking to support their use. Age, general health, and comorbidities need to be taken into account when deciding the right treatment modality for each individual patient.

miR-19b regulates hTERT mRNA expression through targeting PITX1 mRNA in melanoma cells

Human telomerase reverse transcriptase (hTERT) plays a crucial role in cancer development. We previously identified paired-like homeodomain1 (PITX1) as an hTERT suppressor gene. However, the underlying mechanisms that are involved in the regulation of PITX1 remain unknown. Here, we report that the microRNA-19b (miR-19b) regulates hTERT expression and cell proliferation through inhibition of PITX1. Compared with normal melanocyte cells, miR-19b expression was higher in most melanoma cells and was accompanied by downregulation of PITX1. Moreover, overexpression of miR-19b inhibited PITX1 mRNA translation through a miR-19b binding site within the 3'UTR of the PITX1 mRNA. Our combined findings indicate the participation of miR-19b as a novel upstream effector of hTERT transcription via direct targeting of PITX1.

BRAF analysis on a spectrum of melanocytic neoplasms: an epidemiological study across differing UV regions

BRAF mutation has been linked to the development of melanocytic tumors in homogeneous Caucasian cohorts. The role of solar UV radiation (UVR) in BRAF mutation status is poorly understood. We studied the epidemiology of BRAF mutation across a spectrum of melanocytic neoplasms in populations with differing UVR rates. Extended testing for 9 mutation types was attempted on 600 melanocytic neoplasms including banal nevi (n = 225), dysplastic nevi (n = 113), primary (n = 172), and metastatic melanomas (n = 90). Specimens were collected from 4 countries with increasing UVR rates (in kJ/m/yr): Syria (n = 45; UVR = 93.5), Lebanon (n = 225; UVR = 110), Pakistan (n = 122; UVR = 128), and Saudi Arabia (n = 208; UVR = 139). UVR was estimated from 21-year averages from The National Center for Atmospheric Research database. The overall BRAF mutation rate was 49% (268 of 545) and differed significantly by the geographic location [34% Pakistan, 49% Lebanon, 67% Syria, and 54% Saudi Arabia; P = 0.001], neoplasm type (P < 0.001), and anatomical location (P < 0.001) but not with age (P = 0.07) and gender (P = 1.0). V600E was the predominant mutation type, found in 96.3% of the cases. Incidence of melanoma was significantly greater in BRAF-negative (39%) versus BRAF-positive (17%) groups. For BRAF-positive cases, less severe lesions were systematically more frequent (P < 0.001). Multivariate analysis indicated that BRAF mutation is predicted by neoplasm type, anatomical site, and geographic location. In our Near East cohort, BRAF mutation rates varied by geographic location but not based on UVR. BRAF-positive status was associated with less severe lesions.

Treatment patterns and outcomes among patients with metastatic melanoma treated in community practice

BACKGROUND

The primary systemic treatments for advanced melanoma have been chemotherapy and immunotherapy. New agents are currently in development.

OBJECTIVES

This study aimed to characterize treatment patterns and outcomes across several lines of therapy and to illustrate the treatment landscape prior to the approval of new therapies. The study endpoints were progression-free survival (PFS), overall survival (OS), and best overall response within line of therapy.

METHODS

A retrospective chart analysis was conducted at 11 community oncology practices in the USA. Data for patients aged ≥18 years and diagnosed with stage IV and/or metastatic melanoma during 2006-2010 were analyzed. Primary endpoints were PFS within line of therapy and OS from the diagnosis of metastasis.

RESULTS

Data on a total of 202 patients were collected. The sample was mostly male (60%) and Caucasian (88%), with a mean age of 61.3 years. Of the 202 patients, 56 (28%) never received any systemic therapy. In the remaining 146 patients, systemic therapies included temozolomide-based regimens (n = 68), platinum-based regimens without temozolomide (n = 16), other regimens (n = 23), and research regimens (n = 39). Of the 146 patients who received systemic therapy, not all did so immediately after the diagnosis of metastasis: 102 (51%) patients did so shortly after diagnosis and before first disease progression, and 44 (22%) did so after first disease progression. Response rates were very low (≤5%) and did not differ across treatment groups. Progressive disease was the most frequent best overall response category identified, with rates of 83, 78, and 89% in the first to third lines of treatment, respectively. In 146 patients receiving first-line systemic therapy, median PFS was 3.25 months. Median OS in the entire sample was 7.66 months.

CONCLUSIONS

Findings provided little evidence for any beneficial effects of the treatments available in the timeframe referred to in this study. Few patients (≤5%) responded to treatment, PFS among treated patients was short (3.25 months in first-line treatments, less in later lines), and there was no evidence of a differential effect of treatment regimens on PFS. There was no evidence of shorter survival in patients who never received systemic therapy. The high proportion of patients who did not receive any systemic therapy highlights the lack of effective therapies and underscores the unmet medical need in this patient population.

KIT, NRAS, BRAF and PTEN mutations in a sample of Swedish patients with acral lentiginous melanoma

BACKGROUND

Acral lentiginous melanoma (ALM) accounts for <10% of all melanomas in Caucasians. Although the involvement of KIT, NRAS and BRAF mutations is well known in ALM, the impact of these mutations on clinicopathological features has not been established.

OBJECTIVE

To define the KIT, NRAS, BRAF and PTEN mutation frequencies in Swedish patients with ALM and to evaluate the impact of mutation status on patient and tumor characteristics.

METHODS

Tumor cells were microdissected from 88 primary ALMs and 16 paired metastases and analyzed for KIT, NRAS and BRAF mutations. A subset of 25 ALMs was also evaluated for PTEN mutations.

RESULTS

BRAF mutations were identified in 17% of the primary ALMs. Both NRAS and KIT mutations were found at a similar frequency of 15%. Only one of the ALMs that were screened for PTEN harbored a mutation (4%). The KIT, NRAS and BRAF mutation status in paired primary and metastatic ALMs was identical. Patients with BRAF mutated tumors were significantly younger (57 years) than those with BRAF wild-type tumors (73 years, p=0.028). BRAF mutations were significantly more common in females (p=0.011) and more often found in tumors located on the feet (p=0.039). Anatomical site was an independent prognostic factor for overall survival; patients with ALMs on the hands or under fingernails had a better prognosis than those with tumors on the feet or under toenails (p=0.025).

CONCLUSION

Our results confirm the presence of KIT, NRAS and BRAF mutations in ALM and provide evidence that mutations in these genes occur at similar frequencies. Our results also show that PTEN is mutated in a small subset of ALM tumors.

BRAF mutational epidemiology in dysplastic nevi: does different solar UV radiation exposure matter?

BACKGROUND

Proto-oncogene B-Raf (BRAF) mutation rates have been reported in nevi and melanomas of homogeneous Caucasian cohorts.

OBJECTIVE

To study the demographics of BRAF mutations in dysplastic nevi of populations with differing potential solar UV radiation exposure.

METHODS

Extended BRAF testing for 9 mutations in 125 dysplastic nevi from 101 patients, derived from populations with differing potential UV radiation exposure rates (Lebanon and Saudi Arabia), was performed. Clinical and microscopic parameters were recorded.

RESULTS

BRAF mutation status was carried out for 101/125 (80.8%) cases with an overall mutation rate of 62.4% (63/101). V600E (c.1799T > A) was the predominant mutation, found in 61/63 (96.8%) cases. BRAF mutation rate differed significantly by potential UV radiation exposure (Lebanon: 53.4%, Saudi Arabia: 74.4%, P < 0.05). A 43.8% discordant mutation rate (7/16 patients) was found in patients with multiple nevi, including 2 patients with different BRAF mutations. Microscopic examination subdivided the dysplasia into mild (n = 24), moderate (n = 60) and severe (n = 41) with trunk predominance (72.8%). Higher rates of pigment in the stratum corneum were identified in Saudi Arabia (P < 0.05). No statistical significant increase in BRAF mutation rate was noted with advanced architectural and cytological atypia. Parameters associated with a negative BRAF mutation status included upper extremity location, regression, cohesiveness and presence of suprabasal melanocytes (P < 0.05). Positive BRAF mutation status was reasonably predicted by multivariate binary logistic regression by 2 independent predictors: Geographic location and compound nevus type.

CONCLUSIONS

In our Near Eastern cohort, the BRAF mutation rate varied significantly by geographic location. In patients with multiple dysplastic nevi examined, discordant BRAF mutation status potentially negates an underlying constitutional predilection.

Unique prognostic factors in acral lentiginous melanoma

BACKGROUND

This study was performed to identify clinicopathologic factors associated with survival in acral lentiginous melanoma.

METHODS

A post hoc analysis of a prospective clinical trial and local database was performed in all patients with acral lentiginous melanomas. Multivariate analyses of factors associated with a tumor-positive sentinel lymph node (SLN) biopsy, disease-free survival (DFS), overall survival (OS), and local and in-transit recurrence-free survival (LITRFS) were performed. Kaplan-Meier survival analyses were performed.

RESULTS

Eighty-five patients were identified. Age younger than 59 years and Breslow thickness (BT) of 2.0 mm or greater were independent risk factors for a positive SLN. SLN status was the only independent risk factor for DFS and LITRFS on multivariate analysis. A BT of 2.0 mm or greater was the only independent risk factor for OS. SLN status distinguished differences in DFS, OS, and LITRFS on Kaplan-Meier analysis.

CONCLUSIONS

SLN status is the dominant factor for recurrence and survival in acral lentiginous melanoma. BT and ulceration are less important in this histologic subtype.

Superficial spreading and nodular melanoma are distinct biological entities: a challenge to the linear progression model

The classification of melanoma subtypes into prognostically relevant and therapeutically insightful categories has been a challenge since the first description of melanoma in the 1800s. One limitation has been the assumption that the two most common histological subtypes of melanoma, superficial spreading and nodular, evolve according to a linear model of progression, as malignant melanocytes spread radially and then invade vertically. However, recent clinical, pathological, and molecular data indicate that these two histological subtypes might evolve as distinct entities. Here, we review the published data that support distinct molecular characterization of superficial spreading and nodular melanoma, the clinical significance of this distinction including prognostic relevance and the therapeutic implications.

Insights into melanoma: targeting the mTOR pathway for therapeutics

INTRODUCTION

Cutaneous melanoma represents < 5% of all skin cancers, but is responsible for the majority of skin cancer-related deaths. Ocular melanoma is the most common primary eye tumor in adults, and accounts for approximately 5% of all melanomas. Despite new diagnostic and therapeutic tools, the overall survival of patients treated for melanoma has not improved and most patients die of metastatic disease. Therefore, clarification of the molecular mechanisms underlying the etiopathogenesis of cutaneous and ocular melanomas may help determining the prognosis and tailoring therapy of patients harboring melanomas.

AREAS COVERED

In this review the authors aim to survey relevant research in the molecular mechanisms underlying melanomagenesis, and therapies under evaluation with emphasis in the mTOR pathway.

EXPERT OPINION

Despite an increasingly understanding of the genetics and biochemistry of melanoma, the mechanisms underlying their complex interactions are still poorly understood. Their clarification will lead to more successful therapeutic strategies and evidence-based management of patients with melanoma. More active drug combinations together with appropriate melanoma patient stratification based on molecular biomarkers will be essential for new advances in melanoma therapy.

Molecular targets in melanoma: time for 'ethnic personalization'

Worldwide, the incidence of melanoma continues to rise. Although not the most common cutaneous malignancy, it is the most lethal. Until recently, while other oncologic patients benefited from the nuances of targeted therapy, those afflicted with melanoma lacked that option. In 2011, the US FDA approved an oral agent that targets the BRAF oncogene. As this information is promising, it is essential that other populations (in addition to Caucasians) are examined, in order to further comprehend the biology of melanoma. Recent studies profiling various ethnicities, including Asians, have provided novel data with respect to the molecular characterization (c-KIT, BRAF, NRAS) of melanoma. It is hopeful that the management of melanoma will be universally applicable to all ethnic groups.

The melanomas: a synthesis of epidemiological, clinical, histopathological, genetic, and biological aspects, supporting distinct subtypes, causal pathways, and cells of origin

Converging lines of evidence from varied scientific disciplines suggest that cutaneous melanomas comprise biologically distinct subtypes that arise through multiple causal pathways. Understanding the respective relationships of each subtype with etiologic factors such as UV radiation and constitutional factors is the first necessary step toward developing refined prevention strategies for the specific forms of melanoma. Furthermore, classifying this disease precisely into biologically distinct subtypes is the key to developing mechanism-based treatments, as highlighted by recent discoveries. In this review, we outline the historical developments that underpin our understanding of melanoma heterogeneity, and we do this from the perspectives of clinical presentation, histopathology, epidemiology, molecular genetics, and developmental biology. We integrate the evidence from these separate trajectories to catalog the emerging major categories of melanomas and conclude with important unanswered questions relating to the development of melanoma and its cells of origin.

NUAK2: an emerging acral melanoma oncogene

Recent technological advances in cancer genomics make it possible to dissect complicated genomic aberrations of melanomas. In particular, several specific genomic aberrations including 11q13 amplification and KIT aberrations have been identified in acral melanomas. We recently identified NUAK2 at 1q32 as a promising oncogene in acral melanomas and reported its significant roles in tumorigenesis in melanoma cells using both in vitro and in vivo analyses. NUAK2 as a member of the AMPK family has several intriguing aspects both as an oncogene and as a tumor suppressor gene. Here we review genomic aberrations of melanomas focusing on acral melanomas to emphasize the possible roles of NUAK2 in tumorigenesis in general and suggest that NUAK2 has pivotal roles in acral melanomagenesis.

Frequencies of BRAF and NRAS mutations are different in histological types and sites of origin of cutaneous melanoma: a meta-analysis

BACKGROUND

There have been conflicting data regarding the prevalence and clinicopathological characteristics of BRAF and NRAS mutations in primary cutaneous melanoma.

OBJECTIVES

To solve this controversy, this study used a meta-analysis to evaluate the frequencies of BRAF and NRAS mutations, and the relationship between these mutations and clinicopathological parameters of cutaneous melanoma.

METHODS

Data from studies published between 1989 and 2010 were combined. The BRAF and NRAS mutations were reported in 36 and 31 studies involving 2521 and 1972 patients, respectively. The effect sizes of outcome parameters were calculated by odds ratios (OR).

RESULTS

BRAF and NRAS mutations were reported in 41% and 18% of cutaneous melanomas, respectively. The mutations were associated with histological subtype and tumour site, but not with age and sex. The BRAF mutation was frequently detected in patients with superficial spreading melanoma (OR=2·021; P<0·001) and in melanomas arising in nonchronic sun-damaged skin (OR=2·043; P=0·001). In contrast, the NRAS mutation was frequently evident in patients with nodular melanoma (OR=1·894; P<0·001) and in melanomas arising in chronic sun-damaged skin (OR=1·887; P=0·018).

CONCLUSIONS

This pooled analysis shows that the incidences of BRAF and NRAS mutations in cutaneous melanomas differ according to histological type and tumour location based on the degree of sun exposure.

Malignant melanoma

Malignant melanoma is the most lethal cutaneous neoplasm. Awareness, detection, and treatment along with sophistication of both the physician and patient are integral components to early recognition and cure of the disease. Diagnosis of melanoma at its earliest stage is crucial to outcome. This article discusses in depth the clinical presentation and evaluation, patterns of growth, and pathologic staging of the neoplasm and regional lymph nodes. Treatment approaches and outcomes are presented.

Melanoma arising in African-, Asian-, Latino- and Native-American populations

This review highlights melanoma trends observed among African-, Asian-, Latino- and Native-American populations. Melanoma is the most lethal form of skin cancer, accounting for about 75% of all skin cancer deaths. Generally, incidence rates increase with age, peak after age 40, and are greater in men than women. However, these trends do not reflect what is typically seen in minority ethnic groups, where incidence rates are lower. In addition, for some groups, relative disease-specific survival also is lower compared with European-Americans. Melanomas in minority populations also tend to appear in atypical locations and are of unclear etiology. To improve our understanding of the causes of melanoma arising in ethnic minority populations future research efforts are needed. In addition, the general lack of awareness of this disease entity among minority populations and the fact that certain ethnic groups tend to present with advanced disease further highlight the need for educational programs for both patients and health care professionals.

BRAF activation initiates but does not maintain invasive prostate adenocarcinoma

Prostate cancer is the second leading cause of cancer-related deaths in men. Activation of MAP kinase signaling pathway has been implicated in advanced and androgen-independent prostate cancers, although formal genetic proof has been lacking. In the course of modeling malignant melanoma in a tyrosinase promoter transgenic system, we developed a genetically-engineered mouse (GEM) model of invasive prostate cancers, whereby an activating mutation of BRAF^V600E–a mutation found in ∼10% of human prostate tumors–was targeted to the epithelial compartment of the prostate gland on the background of Ink4a/Arf deficiency. These GEM mice developed prostate gland hyperplasia with progression to rapidly growing invasive adenocarcinoma without evidence of AKT activation, providing genetic proof that activation of MAP kinase signaling is sufficient to drive prostate tumorigenesis. Importantly, genetic extinction of BRAF^V600E in established prostate tumors did not lead to tumor regression, indicating that while sufficient to initiate development of invasive prostate adenocarcinoma, BRAF^V600E is not required for its maintenance.

KIT gene mutations and copy number in melanoma subtypes

PURPOSE

We recently identified a KIT exon 11 mutation in an anorectal melanoma of a patient who had an excellent response to treatment with imatinib. To determine the frequency of KIT mutations across melanoma subtypes, we surveyed a large series of tumors.

EXPERIMENTAL DESIGN

One hundred eighty-nine melanomas were screened for mutations in KIT exons 11, 13, and 17. KIT copy number was assessed by quantitative PCR. A subset of cases was evaluated for BRAF and NRAS mutations. Immunohistochemistry was done to assess KIT (CD117) expression.

RESULTS

KIT mutations were detected in 23% (3 of 13) of acral melanomas, 15.6% (7 of 45) of mucosal melanomas, 7.7% (1 of 13) of conjunctival melanomas, 1.7% (1 of 58) of cutaneous melanomas, and 0% (0 of 60) of choroidal melanomas. Almost all the KIT mutations were of the type predicted to be imatinib sensitive. There was no overlap with NRAS mutations (11.1% of acral and 24.3% of mucosal tumors) or with BRAF mutations (absent in mucosal tumors). Increased KIT copy number was detected in 27.3% (3 of 11) of acral and 26.3% (10 of 38) of mucosal melanomas, but was less common among cutaneous (6.7%; 3 of 45), conjunctival (7.1%; 1 of 14), and choroidal melanomas (0 of 28). CD117 expression, present in 39% of 105 tumors representing all melanoma types, did not correlate with either KIT mutation status or KIT copy number.

CONCLUSIONS

Our findings confirm that KIT mutations are most common in acral and mucosal melanomas but do not necessarily correlate with KIT copy number or CD117 expression. Screening for KIT mutations may open up new treatment options for melanoma patients.

In melanocytic lesions the fraction of BRAF V600E alleles is associated with sun exposure but unrelated to ERK phosphorylation

BRAF(V600E) mutation has been frequently reported in different types of melanocytic lesions, but its role in melanomagenesis is poorly understood, having been associated with either the proliferative-induced MAPK pathway activation or the acquisition of oncogene-driven senescence. The presence of BRAF alterations has been related to sun exposure, although the molecular mechanisms underlying this event are only partly known. To elucidate the relationships among BRAF/NRAS alterations, MAPK pathway activation, and sun exposure, we examined 22 acquired nevi and 18 cutaneus melanomas from 38 patients. Microdissected tissues from each lesion were subjected to BRAF/NRAS mutation analysis by sequencing, allele-specific PCR and pyrosequencing assay. The same lesions were also examined for the expression of phosphorylated ERK1/2. Phototype and an accurate history of sun exposure were evaluated for each patient. BRAF(V600E) mutation was detected in 50% of the acquired nevi and in 70% of the cutaneus melanomas in the absence of NRAS alterations. The fraction of alleles carrying BRAF(V600E) substitution was variable but strongly associated with sun exposure. In contrast, no relationship was evidenced between the presence of this mutation and patients' phototype, phosphorylated ERK1/2 expression, or Clark's level. Our findings indicate that in melanocytic lesions, BRAF(V600E) mutation can affect a subset of the cells and is associated with the type and quantity of sun exposure. This mutation is independent of the nevo-melanoma progression and unrelated to ERK phosphorylation, suggesting that alternative mechanisms to the MAPK activation are also involved in this type of transformation.

[DNA copy number changes in the diagnosis of melanocytic tumors]

In the case of many tumors, the development of cancer is associated with a loss of control over genomic integrity, resulting in alterations, determined by selection, of the genome of the cancer cells. Comparative genomic hybridization (CGH) is a method that can be used to assess the entire genome of tumor cells for the presence of changes in DNA copy number. CGH analysis has revealed that melanomas differ from melanocytic nevi in the presence of frequent chromosomal aberrations. CGH analysis of benign melanocytic tumors typically shows no clonally expanded chromosomal aberrations, while in the vast majority of melanomas gains and losses of particular chromosomes are found. As an exception, Spitz nevi show an increased copy number of chromosome 11p in about 20% of cases, something not found in melanoma. These marked differences between the aberration patterns of melanomas and melanocytic nevi can be exploited during differential diagnosis of melanocytic tumors in which histopathologic assessment yields equivocal results. In addition, it has also been shown with the aid of CGH and mutation analysis that melanomas are not a homogenous disease, but rather a group of genetically different tumors. A study checking for correlations between the chromosomal alterations in melanocytic tumors not classified at diagnosis and the course of illness in patients is currently under way.

Cutaneous melanoma subtypes show different BRAF and NRAS mutation frequencies

PURPOSE

BRAF mutations are present in two thirds of cutaneous melanomas and many of the rest have NRAS mutations. However, cutaneous melanoma is a heterogeneous disease with many clinicopathologic subtypes. Of these, the majority fits into four categories: superficial spreading, nodular, lentigo maligna, and acral lentiginous melanoma (ALM). Thus far, there is very limited data combining BRAF and NRAS mutation analysis to explore differences between cutaneous melanoma subtypes. The aim of this study was to address this issue.

EXPERIMENTAL DESIGN

The frequency of BRAF and NRAS hotspot mutations, in exons 15 and 2, respectively, was assessed in 59 cutaneous melanomas comprising superficial spreading, nodular, lentigo maligna, and ALM using single-strand conformational polymorphism and RFLP-PCR analysis.

RESULTS

Only 2 of 21 (9.5%) ALM showed BRAF exon 15 mutation compared with 9 of 14 (64.3%) superficial spreading malignant melanomas, 4 of 11 (36.4%) nodular melanomas, and 7 of 13 (53.4%) lentigo maligna melanomas (P < 0.01). However, our key finding is that the combined analysis of BRAF exon 15 and NRAS exon 2 showed that there were no significant differences in the overall mutation frequency between subtypes. In particular, 9 of 19 (47.4%) ALM without BRAF exon 15 mutation had an NRAS exon 2 mutation.

CONCLUSIONS

We show that the overall BRAF/NRAS frequency in mutation hotspots is not significantly different among cutaneous melanoma subtypes. These data show that mitogen-activated protein kinase pathway activation may be important in all major subtypes of cutaneous melanoma, although the mechanism by which this is achieved varies.

Understanding spitzoid tumours: new insights from molecular pathology

Spitzoid tumours are a morphologically diverse group of lesions that share histological similarity to the Spitz naevus, a benign melanocytic skin tumour. Distinguishing classic Spitz naevi from cutaneous malignant melanoma is usually achievable on standard histology sections, but occasionally equivocal lesions are encountered that show features intermediate between these two entities and consequently generate considerable clinical and histopathological concern. The nomenclature and diagnostic criteria for spitzoid lesions are not standardized and this article begins by considering the adverse effect this has on our understanding of spitzoid tumour biology. Investigations of some of the hallmark features of cancer and neoplasia in spitzoid tumours are described, and the contribution of these studies to our understanding of spitzoid tumour biology is considered, along with their potential diagnostic utility. These studies compare spitzoid tumours with better-characterized melanocytic lesions, and from such comparisons assumptions concerning the biological nature of different spitzoid tumours can be made. In contrast, investigations of the mitogen-activated protein kinase (MAPK) pathway and DNA gains and losses have suggested that Spitz naevi may be genetically distinct from other melanocytic tumours. The studies that led to this conclusion are reviewed, as well as subsequent work examining whether the same applies to all spitzoid tumours. Possible explanations for the considerable inconsistencies within some of these data are explored. Finally, potential pathways of tumour progression within spitzoid lesions are considered, with an emphasis placed upon insights gained from investigations of MAPK genes and DNA gains and losses.

Number of Nevi and Early-Life Ambient UV Exposure Are Associated with BRAF-Mutant Melanoma

Malignant melanomas often contain BRAF or NRAS mutations, but the relationship of these mutations to ambient UV exposure in combination with phenotypic characteristics is unknown. In a population-based case series from North Carolina, 214 first primary invasive melanoma patients in the year 2000 were interviewed regarding their risk factors. Ambient solar UV exposures were estimated using residential histories and a satellite-based model. Cases were grouped on the basis of BRAF and NRAS somatic mutations, determined using single-strand conformation polymorphism analysis and radiolabeled DNA sequencing, and the risk profiles of these groups were compared. Mutually exclusive BRAF-mutant and NRAS-mutant cases occurred at frequencies of 43.0% and 13.6% with mean ages at diagnosis of 47.3 and 62.1 years, respectively. Tumors from patients with >14 back nevi were more likely to harbor either a BRAF mutation [age-adjusted odds ratio (OR), 3.2; 95% confidence interval (95% CI), 1.4-7.0] or an NRAS mutation (age-adjusted OR, 1.7; 95% CI, 0.6-4.8) compared with patients with 0 to 4 back nevi. However, BRAF-mutant and NRAS-mutant tumors were distinctive in that BRAF-mutant tumors were characteristic of patients with high early-life ambient UV exposure (adjusted OR, 2.6; 95% CI, 1.2-5.3). When ambient UV irradiance was analyzed by decadal age, high exposure at ages 0 to 20 years was associated with BRAF-mutant cases, whereas high exposure at ages 50 and 60 years was characteristic of NRAS-mutant cases. Our results suggest that although nevus propensity is important for the occurrence of both BRAF and NRAS-mutant melanomas, ambient UV irradiance influences risk differently based on the age of exposure. The association of BRAF mutations with early-life UV exposure provides evidence in support of childhood sun protection for melanoma prevention.

The FBXW7 β-form is suppressed in human glioma cells

FBXW7 (F-box and WD40 domain protein 7) is an F-box protein with 7 tandem WDs (tryptophan-aspartic acid) that functions as a phosphoepitope-specific substrate recognition component of SCF (Skp1-Cul1-F-box protein) ubiquitin ligases and catalyzes the ubiquitination of proteins promoting cell proliferation, such as CCNE1, MYC, AURKA, NOTCH1, and JUN, which are frequently activated in a wide range of human cancers. FBXW7 is a candidate tumor suppressor, and mutations have been reported in some human tumors. In this study, we analyzed 84 human tumor cell lines in search for genetic alterations of FBXW7, as well as mRNA and protein expressional changes, and compared them with expression levels of the CCNE1, MYC, and AURKA proteins. We found a novel nonsense mutation in a colon cancer cell line SCC and confirmed the missense mutations in SKOV3, an ovarian cancer cell line, and LoVo, a colon cancer cell line. Moreover, suppressed expression of FBXW7 accompanied by activation of the target proteins were observed in ovarian, colon, endometrial, gastric, and prostate cancers. It is notable that highly suppressed mRNA expression of the FBXW7 beta-form was found in all the human glioma cell lines analyzed; enhanced expressions of CCNE1, MYC, and AURKA were observed in these cells. Our present results imply that FBXW7 plays a pivotal role in many tissues by controlling the amount of cell cycle promoter proteins and that dysfunction of this protein is one of the essential steps in carcinogenesis in multiple organs.

BRAF and NRAS mutations in melanoma and melanocytic nevi

In this report, we investigated BRAF/NRAS mutations in samples from a case-control study of melanoma and a series of benign melanocytic nevi. We evaluated potential associations between BRAF mutations and histopathologic and pigmentary characteristics of melanoma. Mutations in BRAF and NRAS were detected by sequencing microdissected/laser-captured DNA from 18 in-situ melanomas, 64 primary melanomas, and 51 nevi. Nevi showed the highest frequency of BRAF mutations (82%). BRAF mutations were identified in 29% of invasive melanomas and in only 5.6% of in-situ melanomas. Mutations in NRAS were found in 5.2% of primary melanomas, 5.9% of nevi and no NRAS mutations were seen in in-situ melanomas. A majority of the BRAF mutations observed in primary invasive melanoma were seen in superficial spreading melanoma (15/17), and melanomas with BRAF mutations were also more likely to be found on a body site that was likely to be exposed to intermittent sun exposure compared with chronic or no sun exposure (P=0.02). Tumors with BRAF mutations were also significantly more likely to occur in association with a contiguous nevus (odds ratio 3.49, 95% confidence interval 1.06-11.46), although a contiguous nevus was not found in all melanomas with a BRAF mutation. Our data support the evidence that the mitogen-activated protein kinase pathway is upregulated in a large percentage of melanocytic lesions, but these mutations are not sufficient for malignant transformation. We suggest that BRAF mutations contribute to benign melanocytic hyperplasia, but are likely to contribute to invasive melanoma only in conjunction with other mutations.

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.

Distinguishing melanocytic nevi from melanoma by DNA copy number changes: comparative genomic hybridization as a research and diagnostic tool

Cancer typically results in loosened control over genomic integrity, resulting in alterations of the genome of cancer cells. Comparative genomic hybridization (CGH) is a method that can be used on DNA extracted from routinely fixed tissue to assess the entire genome for the presence of changes in DNA copy number. CGH analysis has revealed that melanoma differs from melanocytic nevi by the presence of frequent chromosomal aberrations. In contrast, melanocytic nevi typically show no chromosomal aberrations, or have a restricted set of alterations with basically no overlap to melanoma. These marked differences between aberration patterns in melanomas and melanocytic nevi can be exploited diagnostically to classify melanocytic tumors that are ambiguous based on histopathologic assessment. In addition to potential diagnostic applications, detailed analyses of recurrent aberrations can lead to the identification of genes relevant in melanocytic neoplasia.

B-RAF and melanocytic neoplasia

High frequency of B-RAF gene mutations has recently been identified in benign melanocytic nevi and melanoma. This review focuses on clinical studies that evaluate the role of B-RAF in melanocytic neoplasia.

BRAF somatic mutations in malignant melanoma and melanocytic naevi

BRAF somatic mutations are frequently found in primary and metastatic melanomas and melanocytic naevi. Commonly found BRAF mutants stimulate constitutive RAF/MEK (mitogen-activated ERK-activating kinase)/ERK (extracellular signal-regulated kinase) pathway activation and act as transforming oncogenes in NIH-3T3 cells and immortalized murine melanocytes. The most common BRAF mutation is the V600E alteration, but over 30 distinct BRAF mutations, varying in biological activity, have been found and may be predictive of clinically relevant tumour differences. The origin of these acquired mutations remains unknown, but melanomas have a different BRAF mutational spectrum from other tumours, possibly resulting from unique environmental exposures. In melanoma cases, BRAF mutations are frequently found in superficial spreading or nodular histological subtypes, in tumours on intermittently sun-exposed sites and in younger patients. Although evidence indicates that the activation of the RAF/MEK/ERK pathway influences the proliferation, invasion and survival of melanoma cells in vitro, the exact role of BRAF mutation in melanoma tumour progression, maintenance and outcome remains controversial. In addition, although BRAF and NRAS mutations are mutually exclusive in melanomas, other genetic events may complement BRAF mutation to produce biological activity similar to NRAS mutation. Nonetheless, preclinical and early clinical studies predict that RAF/MEK/ERK pathway inhibitors will have therapeutic activity towards melanoma, but that tumour subclassification by BRAF/NRAS mutational status may be necessary to evaluate their efficacy.