A method and kit for inhibiting the proliferation of cancer cells are disclosed, based on a combination of a gemcitabine and a telomerase inhibitor. When used in cancer therapy, the two compounds in combination enhance the anti-cancer treatment efficacy obtained with gemcitabine alone or the telomerase inhibitor alone. Preferably, efficacy is supraadditive or synergistic in nature relative to the combined effects of the individual agents, with minimal exacerbation of side effects.