Electrochemotherapy with bleomycin and cisplatin enhances cytotoxicity in primary and metastatic uveal melanoma cell lines in vitro

Electrochemotherapy (ECT) enhances responsiveness to cytotoxic drugs in numerous cell lines in vitro. Clinically ECT is widely applied for skin tumor ablation and has shown efficacy in treating non-resectable colorectal liver metastases. There is limited experience of ECT for ocular tumor therapy. We investigated the cytotoxic effect of bleomycin and cisplatin in combination with electroporation on chemoresistant human uveal melanoma (UM) cell lines in vitro. Four UM cell lines (Mel 270, 92-1, OMM-1, OMM-2.5) were treated with electroporation (pulse amplitude 300-1000 V/cm, 8-80 pulses, 100 μs, 5 Hz) and increasing concentrations of bleomycin and cisplatin (0-7.5 μg/ml). Cell survival was analyzed by MTT viability assay after 36 hours. UM cell lines were resistant to both bleomycin and cisplatin. In combination with electro- poration, the effects of bleomycin and cisplatin were increased 8-70 fold and 3-15 fold, respectively, in all UM cell lines. At the lowest concentration of bleomycin tested (1 μg/ml), viability was maximally reduced in all UM cell lines by ≥69% with electroporation conditions of 750 V/cm and 20 pulses. All UM cell lines were more resistant to cisplatin; however, electro- poration of 1000 V/cm and 8 pulses resulted in similar reductions in cell viability of 92-1, Mel270 with 2.5 μg/ml cisplatin, OMM2-5 cells with 5 μg/ml cisplatin and OMM1 cells with 1 μg/ml cisplatin. In vitro ECT with bleomycin or cisplatin is more effective than the highest concentration of the antineoplastic drug or electroporation alone, opening new perspectives in primary and metastatic UM treatment.