Effects of the MHC class II complex engagement and of the meso-tetra(4-sulfonatophenyl) porphynate derivatives on melanoma cells.

The extreme resistance of melanoma to the available tumour treatment has stimulated the investigation of immunotherapy approaches and the identification of new chemotherapeutic agents. Based on this, we studied the signalling triggered in melanoma cells by the Major Histocompatibility Complex (MHC) class II molecules as well as the molecular targets and the signalling activated by some TPPS derivatives. The melanoma cells often display a constitutive expression of the MHC class II molecules which is usually associated with a higher metastatic dissemination. Therefore, in the aim to understand the intracellular signalling that melanomas use to frustrate an effective anti-tumour response, we stimulated the melanoma cells with a specific anti-MHC class II monoclonal antibody (L243) that mimic the class II interaction with the TCR. Interestingly, in stimulated melanoma cells we observed an increased localisation of HLA-DR molecules in lipid rafts and their physical association with the adhesion receptor integrin ?1 in these membrane compartments. FAK and JNK activation as a consequence of the class II engagement were also reported. Therefore, we analysed the proteins localised in exosomes secreted by stimulated melanoma cells and we observed a lower concentration of the HLA-DR molecules as a consequence of the class II engagement. Moreover, in the aim to identify new potential anti-tumour drugs for this aggressive type of cancer, we studied a new class of porphyrin derivatives and we showed that the (Bu2Sn)2TPPS and (Bu3Sn)4TPPS compounds induce the death for apoptosis of melanoma cells. The analysis of the apoptotic pathway activated by these TPPS derivatives, showed that the protein kinases ERK 1/2, JNK, and p38 are activated in (Bu2Sn)2TPPS 10-5M and (Bu3Sn)4TPPS 10-6M treated melanoma cells. These results strongly suggested all the three MAP Kinases are involved in the apoptotic death of treated melanoma cells. Therefore, in the aim to understand the targets of these compounds we analyzed their cellular localization taking advantage by the porphyrin fluorescence. Interestingly, the results of these experiments showed a rapid concentration of (Bu2Sn)2TPPS and (Bu3Sn)4TPPS in the nucleus and in the nucleoli of melanoma cells in comparison with TPPS. Moreover, we identified respectively in 500 nM and in 80 nM, the concentrations of (Bu2Sn)2TPPS and (Bu3Sn)4TPPS sufficient to significantly reduce the growth of melanoma cells after only 48 h of treatment. Indeed an outstanding slowdown of cells growth and loss of cell-cell interactions are evident by in vitro wound repair assay.