Activation of T-cells through an antigen-independent alternative pathway induces precocious sensitivity to Fas-induced apoptosis

Phytohemagglutinin Inhibits Lymphoid Tumor GrowthIn VitroandIn Vivo

Cure rates for a variety of leukemias and lymphomas have improved dramatically over the past several decades, but relapsed disease continues to account for thousands of deaths per year. Viable treatment options for relapsed disease are few, encouraging the development of novel therapies. In the present paper, we describe phytohemagglutinin (PHA), a standard T cell mitogen, as an inhibitor of both T- and B-cell tumors. In vitro studies show that PHA can inhibit incorporation of 3H-thymidine and mediate apoptosis of B- and T-cell tumor lines. The inhibitory effects are enhanced when PHA is used in conjunction with the cell cycle directed drug 5-fluorouracil (5-FU). Phytohemagglutinin treatments can also impede tumor growth in mice while showing no toxic side effects in this animal model.