Selective growth inhibition by suppression of F1Fo ATPase in canine malignant melanoma cell lines

Canine malignant melanoma (CMM) is a highly aggressive and fatal neoplasm. To identify potential therapeutic compounds and/or targets, 320 compounds were screened for their growth inhibitory activity in a CMM line (CMM-1) using a chemical library known to target specific signaling pathways/cell growth-related molecules. Among the compounds screened, the F1Fo ATPase inhibitor oligomycin showed potent growth inhibitory effects in CMM-1 cells, while exhibiting less toxic effects in a non-neoplastic control cell line (MDCK cells). The growth inhibitory effect of oligomycin A was then examined using six CMM lines and MDCK cells. Three CMM lines were highly sensitive to oligomycin A, with around 3000–20 000 times lower IC₅₀ compared with oligomycin A-resistant CMM lines and MDCK cells. Oligomycin A-sensitive CMM-1 cells exhibited much greater oligomycin A-induced decreases in cellular ATP compared to oligomycin A-resistant cell lines. Although the oligomycins are clinically unsuitable because of its in vivo toxicity, these findings implicate the potential of F1Fo ATPase as a therapeutic target in a subset of CMM.