Purpose: To describe the differential response of uveal melanoma to NFkB inhibition in vitro vs. in vivo.
Methods: The C918 uveal melanoma (UM) cell line was grown in culture without and with 1mg/ml of the BMS-345541 NFkB inhibitor. Cells were grown under normoxic and hypoxic conditions (0.5%O2) for 72 hours with viability and Caspase3 measurements every 24 hours. Later, C918 cells were transfected with the luciferase (luc) gene and cells that stably expressed luc were selected. The new C918-Luc cells were injected either subcutaneously or directly into the livers of SCID mice through a small (1 cm) abdominal wall incision via a 0.5 cc insulin syringe (29 gauge needle) in a non-reflux technique. Injected cells were visualized with an IVIS bioluminescence (BioL) camera . Cells were allowed to settle for 1 week before BMS-345541 (0, 2, 10, 20, and 50 mg/kg) was administered IP 3 times / week for 3 weeks, and tumor growth was monitored via BioL twice weekly. The experiment was terminated following euthanasia and the livers were harvested for histopathologic evaluation.
Results: Cell viability diminished similarly either with addition of BMS in normoxia or without it in hypoxia, and was abolished with BMS in hypoxia. A similar increase in Caspase3 was noted at 72 hours. In SCID mice, bioluminescence started decreasing after administration of BMS, but then turned into a remarkable growth spurt which increased with higher doses of BMS. Histopathology of treated tumors showed a central area of necrosis surrounded by viable tumor vs. a completely viable tumor in untreated animals.
Conclusions: Inhibition of NFkB reduces cell viability and increases apoptosis in vitro and in vivo. However, this effect is reversed by yet unknown mechanisms in vivo, possibly triggered by the necrotic tumor. These mechanisms may lie behind UM’s unresponsiveness to chemotherapeutics.
