A novel sigma2 receptor agonist induces apoptosis in human metastatic melanoma SK-MEL-2 cell line.
L. Benassi1,2, C. Vaschieri1,2, P.Azzoni1,2, C. Magnoni1,2, A. Pisciotta1, L.Bertoni1, G. Carnevale1,  S.Franchini3, C. Sorbi3 and G. Pellacani1,2.

1.Department of Surgery, Medicine, Dentistry and Morphological Sciences with interest in Transplant, Oncology and Regenerative Medicine, University of Modena and Reggio Emilia, Modena, Italy.
2.Laboratory of Dermatology, University of Modena and Reggio Emilia, Modena, Italy.
3. Department of Life Sciences, University of Modena and Reggio Emilia, Modena, Italy. 

Sigma receptors are highly expressed in various cancer cells and are involved in the modulation of cellular proliferation and cell death.
Several classes of sigma1 and sigma2 ligands developed in our laboratory were assayed for the capability to inhibit cell proliferation in two melanoma cell lines SK-MEL-2 and SK-MEL-28. Cells were treated with increasing concentrations (from 20 to 100µM) of the compounds and monitored at 24 and 48 hours.
In order to identify the best candidate for potential application to melanoma therapy we have selected a novel sigma 2 receptor agonist (16a/BS148) based on its cytotoxic effect. 16a/BS148 was able to significantly induce cell death in SK-MEL-2 cells. Particularly about 40%  positive cells were detected by TUNEL assay in SK-MEL-2 cells at 72 hours while almost no cell death occurred in healthy human melanocytes and SK-MEL-28 cells.
Immunofluorescence analysis, carried out against human mitochondrial protein and cleaved caspase 3, was aimed to evaluate apoptosis in SK-MEL-2 cells. Our data revealed that most of SK-MEL-2 cells stained positive for cleaved caspase 3 expression after 48 hours of exposure, besides showing altered cell morphology and mitochondria distribution. The activation of apoptotic effector caspase 3 was also confirmed by Western blot analysis.
According to our findings 16a/BS148 owns a remarkable selective toxicity for SK-MEL-2 cells and further investigations might provide the basis for representing a promising compound in the treatment of human metastatic melanoma.

A novel sigma-2 receptor agonist induces apoptosis in human metastatic melanoma SK-MEL-2 cell line