Changes in cellular components of spleen and lymph node cells and the effector cells responsible for Meth A tumor eradication induced by zinostatin stimalamer.

We reported previously that pretreatment with zinostatin stimalamer (ZSS) eradicated Meth A tumors in BALB/c mice. We herein investigated cellular components of spleen and lymph node cells of Meth A-bearing ZSS-pretreated mice by flow cytometry; the antitumor effector cells by in vivo depletion of T cells, NK cells, or macrophages; and host-mediated antitumor activity associated with ZSS treatment after tumor transplantation. ZSS given on day-3 transiently decreased the number of spleen cells. The percentage of T cells increased, but B cells and macrophages decreased. B cells decreased in inguinal lymph nodes in Meth A-bearing ZSS-pretreated mice, but increased in Meth A-bearing control mice. In vivo depletion experiments using antibodies or carrageenan showed that antitumor effector cells for tumor eradication are Thy1.2+/Lyt2.2+ and that at least a part of them are asialo GM1+. Thy1.2+/Lyt2.2+/asialoGM1- cells are important in generation of the antitumor activity of ZSS; however, L3T4+ T cells are also involved in initiation of tumor eradication. The result of ZSS treatment after tumor transplantation suggests that ZSS might exhibit antitumor activity by augementating host-mediated antitumor resistance, as well as its intrinsic cytocidal activity.