Polyamines, required components of proliferation, are autoregulated by the protein antizyme. To date, agmatine is the only molecule other than the polyamines that can induce antizyme, and thus influence cell homeostasis and growth. Agmatine has effectively suppressed proliferation in immortalized and transformed cell lines. An increased sensitivity to the anti-proliferative effects of agmatine observed in Ras transformed versus native cells paralleled an increase in agmatine uptake in the transformed cells. We hypothesize that agmatine may target transformed cells via selective transporters.