Background: Malignant melanoma is a fast growing form of skin cancer with increasing global incidence.
Clinically, canine malignant melanoma and human melanoma share comparable treatment-resistances, metastatic
phenotypes and site selectivity.
Objective: Both interferon-β (IFNβ) and bortezomib (BTZ) display inhibitory activities on melanoma cells. Here, we
evaluated the cytotoxic effects of the combination of BTZ and IFNβ gene lipofection on cultured melanoma cell lines.
Method: Cell viability determined by the acid phosphatase method, cell migration mesasured by the wound healing
assay, DNA fragmentation and cell cycle by flow cytometry after propidium iodide staining and reactive oxygen
species (ROS) production by H2DCF-DA fluorescence.
Results: Four canine mucosal (Ak, Br, Bk and Ol) and two human dermal (A375 and SB2) melanoma cell lines were
assayed. BTZ sub-pharmacological concentrations (5 nM) enhanced the cytotoxic effects of IFNβ transgene expression
on melanoma cells monolayers and spheroids. The combination was also more effective than the single treatments
when assayed for clonogenic survival and cell migration. The combined treatment produced a significant raise of
apoptosis evidenced by DNA fragmentation as compared to either BTZ or IFNβ gene lipofection single treatments.
Furthermore, BTZ significantly increased the intracellular ROS generation induced by IFNβ gene transfer in
melanoma cells, an effect that was reversed by the addition of the ROS inhibitor N-acetyl-L-cystein.
Conclusion: The present work encourages further studies about the potential of the combination of interferon gene
transfer with proteasome inhibitors as a new combined therapy for malignant melanoma, both in veterinary and/or
human clinical settings.