This invention relates to anti-cancer uses of ionophores of which clioquinol (5-chloro-7-iodo-8-hydroxyquinoline) is a prototype drug. The present invention is further directed toward using ionophores such as clioquinol alone, or in combination with metals (e.g., zinc or copper, manganese) as anti-cancer and anti-angiogenic agents. This invention further relates to the potentiation of the anti-cancer properties of polyunsaturated fatty acids when used in conjunction with the ionophores of the present invention. The invention is also directed to the therapeutic or prophylactic use of pharmaceutical compositions containing the ionophores of the present invention, and to methods of treating cancer as well as other disease states associated with unwanted angiogenesis and/or cellular proliferation, such as diabetic retinopathy, neovascular glaucoma, rheumatoid arthritis, and psoriasis, by administering effective amounts of such compounds.