Roger Pai

Safety and antitumor activity of recombinant soluble Apo2 ligand

TNF and Fas ligand induce apoptosis in tumor cells; however, their severe toxicity toward normal tissues hampers their application to cancer therapy. Apo2 ligand (Apo2L, or TRAIL) is a related molecule that triggers tumor cell apoptosis. Apo2L mRNA is expressed in many tissues, suggesting that the ligand may be nontoxic to normal cells. To investigate Apo2Ls therapeutic potential, we generated in bacteria a potently active soluble version of the native human protein. Several normal cell types were resistant in vitro to apoptosis induction by Apo2L. Repeated intravenous injections of Apo2L in nonhuman primates did not cause detectable toxicity to tissues and organs examined. Apo2L exerted cytostatic or cytotoxic effects in vitro on 32 of 39 cell lines from colon, lung, breast, kidney, brain, and skin cancer. Treatment of athymic mice with Apo2L shortly after tumor xenograft injection markedly reduced tumor incidence. Apo2L treatment of mice bearing solid tumors induced tumor cell apoptosis, suppressed tumor progression, and improved survival. Apo2L cooperated synergistically with the chemotherapeutic drugs 5-fluorouracil or CPT-11, causing substantial tumor regression or complete tumor ablation. Thus, Apo2L may have potent anticancer activity without significant toxicity toward normal tissues.

Differential hepatocyte toxicity of recombinant Apo2L/TRAIL versions.

Our findings not only provide a novel insight into the pathogenesis of the transplant-related atherosclerosis, but also point to a new therapeutic strategy that involves targeting of homing, differentiation and proliferation of putative smooth-muscle progenitor cells derived from the recipient. This is the first report demonstrating that circulating progenitor cells contribute to the development of proliferative diseases. AKIO SAIURA, MASATAKA SATA, YASUNOBU HIRATA, RYOZO NAGAI MASATOSHI MAKUUCHI Department of Surgery, University of Tokyo, Graduate School of Medicine, Tokyo, Japan, Department of Cardiovascular Medicine University of Tokyo, Graduate School of Medicine, Tokyo, Japan A.S. and M.S. supervised this study equally as senior authors Email: sata-2im@h.u-tokyo.ac.jp 1. McKay, R. Stem cells-hype and hope. Nature 406, 361–364 (2000). 2. Asahara, T. et al. Isolation of putative progenitor endothelial cells for angiogenesis. Science 275, 964–967 (1997). 3. Yamashita, J. et al. Flk1-positive cells derived from embryonic stem cells serve as vascular progenitors. Nature 408, 92–96 (2000). 4. Carmeliet, P. One cell, two fates. Nature 408, 43–45 (2000). 5. Clarke, D.L. et al. Generalized potential of adult neural stem cells. Science 288, 1660–1663 (2000).