The Alternative TrkAIII Splice Variant, a Targetable Oncogenic Participant in Human Cutaneous Malignant Melanoma.

Post-therapeutic relapse, poor survival rates and increasing incidence justify the search for novel therapeutic targets and strategies in cutaneous malignant melanoma (CMM). Within this context, a potential oncogenic role for TrkA in CMM is suggested by reports of NTRK1 amplification, enhanced TrkA expression and intracellular TrkA activation associated with poor prognosis. TrkA, however, exhibits tumour-suppressing properties in melanoma cell lines and has recently been reported not to be associated with CMM progression. To better understand these contradictions, we present the first analysis of potential oncogenic alternative TrkA mRNA splicing, associated with TrkA immunoreactivity, in CMMs, and compare the behaviour of fully spliced TrkA and the alternative TrkAIII splice variant in BRAF(V600E)-mutated A375 melanoma cells. Alternative TrkA splicing in CMMs was associated with unfolded protein response (UPR) activation. Of the several alternative TrkA mRNA splice variants detected, TrkAIII was the only variant with an open reading frame and, therefore, oncogenic potential. TrkAIII expression was more frequent in metastatic CMMs, predominated over fully spliced TrkA mRNA expression in ≈50% and was invariably linked to intracellular phosphorylated TrkA immunoreactivity. Phosphorylated TrkA species resembling TrkAIII were also detected in metastatic CMM extracts. In A375 cells, reductive stress induced UPR activation and promoted TrkAIII expression and, in transient transfectants, promoted TrkAIII and Akt phosphorylation, enhancing resistance to reductive stress-induced death, which was prevented by lestaurtinib and entrectinib. In contrast, fully spliced TrkA was dysfunctional in A375 cells. The data identify fully spliced TrkA dysfunction as a novel mechanism for reducing melanoma suppression, support a causal relationship between reductive stress, UPR activation, alternative TrkAIII splicing and TrkAIII activation and characterise a targetable oncogenic pro-survival role for TrkAIII in CMM.

Merkel cell carcinoma: an updated overview of clinico-pathological aspects, molecular genetics and therapy.

Merkel cell carcinoma (MCC) is a rare cutaneous neuroendocrine carcinoma of uncertain origin. MCC incidence varies by country and has been increasing among white populations over the last three decades. MCC occurs most commonly in elderly men and typically arises on sun-exposed areas. It is associated with a high mortality rate due to rapid growth and significant metastatic potential. Clinical and histopathological diagnosis are challenging, but prompt recognition of the disease is imperative for a correct management. Several hypotheses have been proposed to define the cell of origin, which still remains controversial. The discovery of Merkel cell polyoma virus, identified in the majority of MCCs, led to the hypothesis of the existence of two tumour subtypes showing biological, clinico-pathological and prognostic differences. Significant interest is nowadays directed to characterize MCC genomic alterations and microRNA (miRNA) expression profiles. Current treatment strategies for MCC depend on staging, and typically consist of surgery, radiation therapy, chemotherapy and/or, more recently, immunotherapy. The aim of this review is to provide an updated overview of MCC with a special focus on clinico-pathological aspects, molecular-genetics and therapy.

Intra-patient Heterogeneity of BRAF and NRAS Molecular Alterations in Primary Melanoma and Metastases.

Mutations in MAPK signalling genes are driver events in melanoma, and have therapeutic relevance in the metastatic and adjuvant setting. This study evaluated the intra-patient heterogeneity of BRAF, NRAS and c-KIT mutational status between 30 primary melanomas and 39 related metastases, using molecular analysis and immunohistochemistry. BRAF mutations were identified in 46.7% of primary melanomas and 48.7% of metastases and NRAS mutations in 20% and 25.6%, respectively. Intra-patient heterogeneity was detected in 13.3% of patients for both BRAF and NRAS genes and was not associated with clinico-pathological characteristics of melanomas or metastases. High consistency was observed between immunostaining and molecular methods for BRAFV600E (k = 0.90; p < 0.001) and NRASQ61R (k = 0.87; p < 0.001). These findings demonstrate a relevant intra-patient heterogeneity between primary and metastatic lesions that is independent of clinical variables and methodological approach.

Telomeres and Telomerase in Cutaneous Squamous Cell Carcinoma.

The role of telomere biology and telomerase activation in skin cancers has been investigated in melanoma and basal cell carcinoma but limited evidence is available for cutaneous squamous cell carcinoma (cSCC). We will review the current knowledge on the role of telomere and telomerase pathway in cSCC pathogenesis. At the somatic level, both long and short telomere lengths have been described in cSCC. This telomere dichotomy is probably related to two different mechanisms of tumour initiation which determines two tumour subtypes. Telomere shortening is observed during the invasive progression from in situ forms of cSCC, such as Bowen's disease (BD) and actinic keratosis (AK), to invasive cSCC. At the germline level, controversial results have been reported on the association between constitutive telomere length and risk of cSCC. Approximately 75⁻85% of cSCC tumours are characterized by a high level of telomerase activity. Telomerase activation has been also reported in AKs and BD and in sun-damaged skin, thus supporting the hypothesis that UV modulates telomerase activity in the skin. Activating TERT promoter mutations have been identified in 32⁻70% of cSCCs, with the majority showing the UV-signature. No significant correlation was observed between TERT promoter mutations and cSCC clinico-pathological features. However, TERT promoter mutations have been recently suggested to be independent predictors of an adverse outcome. The attention on telomere biology and telomerase activity in cSCC is increasing for the potential implications in the development of effective tools for prognostic assessment and of therapeutic strategies in patients with cutaneous cSCC.

Familial Melanoma: Diagnostic and Management Implications.

BACKGROUND: An estimated 5%-10% of all cutaneous melanoma cases occur in families. This review describes susceptibility genes currently known to be involved in melanoma predisposition, genetic testing of familial melanoma patients, and management implications. RESULTS: CDKN2A is the major high-penetrance susceptibility gene with germline mutations identified in 20%-40% of melanoma families. A positive CDKN2A mutation status has been associated with a high number of affected family members, multiple primary melanomas, pancreatic cancer, and early age at melanoma onset. Mutations in the other melanoma predisposition genes-CDK4, BAP1, TERT, POT1, ACD, TERF2IP, and MITF-are rare, overall contributing to explain a further 10% of familial clustering of melanoma. The underlying genetic susceptibility remains indeed unexplained for half of melanoma families. Genetic testing for melanoma is currently recommended only for CDKN2A and CDK4, and, at this time, the role of multigene panel testing remains under debate. Individuals from melanoma families must receive genetic counseling to be informed about the inclusion criteria for genetic testing, the probability of an inconclusive result, the genetic risk for melanoma and other cancers, and the debatable role of medical management. They should be counseled focusing primarily on recommendations on appropriate lifestyle, encouraging skin self-examination, and regular dermatological screening. CONCLUSIONS: Genetic testing for high-penetrance melanoma susceptibility genes is recommended in melanoma families after selection of the appropriate candidates and adequate counseling of the patient. All patients and relatives from melanoma kindreds, irrespective of their mutation status, should be encouraged to adhere to a correct ultraviolet exposure, skin self-examination, and surveillance by physicians.