Polyamine deprivation stimulates natural killer cell activity in cancerous mice

It has recently been established that the total blockade of all endogenous and exogenous sources of polyamines by a drug containing polyamine deficient chow (DC-PDC+) could inhibit tumor growth in vivo and increase the antitumoral efficacy of chemotherapy drugs. We show here that polyamine deprivation obtained with DC-PDC+ not only influences tumor development via reduction of polyamine concentrations in the tumor itself but, in addition, stimulates cells of the non-specific immune system specialized in tumor cell killing. We report that mice grafted with the 3LL carcinoma present a dramatic decrease in the cytotoxic activity of their natural killer (NK) cells. When these animals are treated with DC-PDC+, their NK cell activity is completely restored to normal values