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Uveal melanoma (UM) is the most common primary intraocular tumor that arises from neoplastic melanocytes in the choroid, iris, and ciliary body. Electrochemotherapy (ECT) has been successfully established for the treatment of skin and soft tissue metastatic lesions, deep-seated tumors of the liver, bone metastases, and unresectable pancreas lesions. The aim of this study was to evaluate the effect of ECT in vitro in 3D spheroid culture systems in primary and metastatic UM cell lines. We also investigated the chick embryo chorioallantoic membrane (CAM) as an in vivo model system for the growth and treatment of UM tumors using ECT. The cytotoxic effect of ECT in 3D spheroids was analyzed seven days following treatment by assessment of the size and MTT [(3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) tetrazolium reduction] assay. The cytotoxicity of ECT after intratumoral or intraarterial administration was evaluated histologically. In vitro and in vivo ECT caused a significant reduction in tumor size and viability compared to electroporation or chemotherapy in both sections of our study. The current results underline the effectiveness of ECT in the treatment of UM and prepare the way for further investigation of its potential application in UM.

Purpose To investigate the cytotoxic effect of bleomycin, mitomycin C ( MMC ) and Fluorouracil (5‐ FU ) in combination with electroporation ( EP ) on human conjunctival melanoma ( CM ) and normal conjunctival cell lines using 2D and 3D cell culture systems in vitro . Methods Two CM ( CRMM 1, CRMM 2) and one normal conjunctival epithelial cell line ( HC jE‐Gi) were treated with various EP conditions and increasing concentrations of 5‐ FU , MMC and bleomycin. Cell survival was assessed by MTT viability assay. All cell lines were seeded to create spheroids and were treated with bleomycin on day 3 and day 8 combined with EP . Spheroids were collected, fixed in buffered formalin and subsequently paraffin embedded for histological assessment of the effects of the treatment on cell viability. Results CM cell lines were resistant to electroporation alone and showed a reduction in cell number only when treated with 1000 Volts/cm and 8 pulses. HC jE‐Gi cells showed higher sensitivity to electric pulses over 750 Volts/cm. MMC and 5‐ FU demonstrated a higher cytotoxicity for the HC jE‐Gi cell line. The CM cell lines were resistant to MMC and 5‐ FU . Bleomycin (1 μ g/ml) alone had no significant effect on the HC jE‐Gi even when combined with EP conditions ≥750 Volts/cm. In contrast, it significantly (p ‐, paired t‐test) reduced cell viability in the CM cell lines. Spheroids treated with bleomycin and EP showed a reduction in tumour mass and proliferation rates after treatment. Conclusion Our in vitro study using 2D and 3D models indicates that the application of EP may effectively enhance chemotherapy with bleomycin in CM . This may offer new viable perspectives for CM treatment.

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.