M-CSF as a therapeutic target in BRAFV600E melanoma resistant to BRAF inhibitors.

BACKGROUND: Disseminated BRAFV600E melanoma responds to BRAF inhibitors (BRAFi) but easily develops resistance with poor prognosis. Secretome plays a pivotal role during tumour progression causing profound effects on therapeutic efficacy. Secreted M-CSF is involved in both cytotoxicity suppression and tumour progression in melanoma. We aimed to analyse the M-CSF contribution in resistant metastatic melanoma to BRAF-targeted therapies. METHODS: Conditioned media from melanoma cells were analysed by citoarray. Viability and migration/invasion assays were performed with paired melanoma cells and tumour growth in xenografted SCID mice. We evaluated the impact of M-CSF plasma levels with clinical prognosis from 35 metastatic BRAFV600E-mutant melanoma patients. RESULTS: BRAFi-resistant melanoma cells secretome is rich in pro-tumour cytokines. M-CSF secretion is essential to induce a Vemurafenib-resistant phenotype in melanoma cells. Further, we demonstrated that M-CSF mAb in combination with Vemurafenib and autophagy blockers synergistically induce apoptosis, impair migration and reduce tumour growth in BRAFi-resistant melanoma cells. Interestingly, lower M-CSF plasma levels are associated with better prognosis in metastatic melanoma patients. CONCLUSIONS: Secreted M-CSF induces a BRAFi-resistant phenotype and means worse prognosis in BRAFV600E metastatic melanoma patients. These results identify secreted M-CSF as a promising therapeutic target toward BRAFi-resistant melanomas.

Descriptive study of naevus involution in a series of 74 patients with atypical naevus syndrome under SIAscopy digital follow-up.

BACKGROUND: Characterization of nevi involution could help to understand the biological behaviour of melanocytic neoplasms. OBJECTIVE: To describe the frequency and morphology of naevus involution in a series of patients with atypical naevus syndrome under digital follow-up with a SIAscopy program and, in a small sample of fading nevi, to analyse histopathological features and immunohistochemical biomarkers. METHODS: Seventy-four patients registered from April 2007 to July 2014 in the SIAscopy system of the Department of Dermatology of Hospital Arnau de Vilanova of Lleida, Spain, were reviewed. Fourteen naevus cases with fading features were prospectively excised during follow-up. Eleven already excised naevus controls were randomly selected from our archive. RESULTS: We observed that 81% of patients showed, at least, one involutive naevus and 25% of recorded nevi presented this phenomenon; the mean time of involution was 46.7 months. The predominant structural pattern was reticular (>70%), and the most frequently observed regression structures were vascular (33.8%). Histopathological significant higher intensity of inflammatory infiltrate in controls and higher presence of laminar and compact fibrosis and increase of vessels in cases were demonstrated. Regarding immunohistochemical biomarkers, only higher expression of cytoplasmic activated caspase 3 in controls was significant. CONCLUSIONS: Naevus involution is a common phenomenon in patients with dysplastic naevus syndrome. It is usually a slow process, more frequent in naevus with reticular pattern. SIAscopy regression structures are uncommon, with the exception of vascular ones. Histologically, fading involutive pattern is characterized by scarce inflammatory infiltrate and melanophages, delicate fibrosis and increase of vessels.

Immunohistochemical analysis of T-type calcium channels in acquired melanocytic naevi and melanoma.

BACKGROUND: Cutaneous malignant melanoma arises from transformed melanocytes de novo or from congenital or acquired melanocytic naevi. We have recently reported that T-type Ca2+ channels (TT-Cs) are upregulated in human melanoma and play an important role in cell proliferation. OBJECTIVES: To describe for the first time in formalin-fixed paraffin-embedded tissue the immunoexpression of TT-Cs in biopsies of normal skin, acquired melanocytic naevi and melanoma, in order to evaluate their role in melanomagenesis and/or tumour progression, their utility as prognostic markers and their possible use in targeted therapies. METHODS: Tissue samples from normal skin, melanocytic naevi and melanoma were subjected to immunohistochemistry for two TT-Cs (Cav3.1, Cav3.2); markers of proliferation (Ki67), the cell cycle (cyclin D1), hypoxia (Glut1), vascularization (CD31) and autophagy (LC3); BRAF V600E mutation (VE1) and phosphatase and tensin homologue (PTEN). Immunostaining was evaluated by histoscore. In silico analysis was used to assess the prognostic value of TT-C overexpression. RESULTS: TT-C immunoexpression increased gradually from normal skin to common naevi, dysplastic naevi and melanoma samples, but with differences in the distribution of both isoforms. Particularly, Cav3.2 expression was significantly higher in metastatic melanoma than in primary melanoma. Statistical correlation showed a linear interaction between PTEN loss/BRAF V600E/Cav3.1/LC3/ Ki67/cyclin D1/Cav3.2/Glut1. Disease-free survival (DFS) and overall survival correlated inversely with overexpression of Cav3.2. DFS also correlated inversely with overexpression of Cav3.1. CONCLUSIONS: TT-C immunoexpression on melanocytic neoplasms is consistent with our previous in vitro studies and appears to be related to tumour progression. TT-C upregulation can be considered as a prognostic marker using The Cancer Genome Atlas database. The high expression of Cav3.2 in metastatic melanoma encourages the investigation of the use of TT-C blockers in targeted therapies.