Mechanisms for T-cell selective cytotoxicity of arabinosylguanine.
Nelarabine, prodrug of arabinosylguanine (ara-G), has demonstrated T-lymphoblastic antileukemic activity in cell lines and in the clinic. To investigate the mechanism for lineage-specific toxicity, the effects of ara-G were compared in CEM (T-lymphoblast), Raji (B-lymphoblast), and ML-1 (myeloid) cell lines. CEM cells were the most sensitive to ara-G-induced apoptosis and accumulated the highest levels of ara-G triphosphate (ara-GTP). However, compared with myeloid and B-lineage cell lines, CEM cells incorporated fewer ara-G molecules-which were at internucleotide positions in all 3 cell lines- into DNA. Ara-G induced an S-phase arrest in both Raji and ML-1, while in CEM the S-phase cells decreased with a concomitant increase in the sub-G1 population. Within 3 hours of ara-G treatment, the levels of soluble Fas ligand (sFasL) in the medium increased significantly in CEM cultures. In parallel, an induction of FasL gene expression was observed by real-time reverse transcriptase-polymerase chain reaction (RT-PCR). Pretreatment of CEM cells with a Fas antagonistic antibody inhibited ara-G-mediated cell death. These results demonstrate that high ara-GTP accumulation in T cells results in an S phase-dependent apoptosis induced by ara-G incorporation into DNA, which may lead to a T cell-specific signal for the induction and liberation of sFasL. Subsequently, the sFasL induces an apoptotic response in neighboring non-S-phase cells. In contrast, myeloid and B cells accumulated lower levels of ara-GTP and arrested in S phase, blocking any apoptotic signaling.
Department of Experimental Therapeutics, Box 71, The University of Texas M. D. Anderson Cancer Center, Houston, TX 77030, USA.
Carlos O
CO
Rodriguez
Christine M
CM
Stellrecht
Varsha
V
Gandhi
D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects; D001087:Arabinonucleosides / Q000493:pharmacokinetics*; D002455:Cell Division / Q000187:drug effects; D053222:Fas Ligand Protein; D015870:Gene Expression / Q000187:drug effects; D006157:Guanosine Monophosphate / Q000378:metabolism; D006160:Guanosine Triphosphate / Q000378:metabolism; D006801:Humans; D019169:Jurkat Cells; D007700:Kinetics; D008562:Membrane Glycoproteins / Q000235:genetics / Q000378:metabolism; D019384:Nucleic Acid Synthesis Inhibitors / Q000494:pharmacology; D013601:T-Lymphocytes / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D015854:Up-Regulation / Q000187:drug effects; D019014:fas Receptor / Q000235:genetics / Q000378:metabolism
D000970:Antineoplastic Agents; D001087:Arabinonucleosides; C505661:FASLG protein, human; D053222:Fas Ligand Protein; D008562:Membrane Glycoproteins; D019384:Nucleic Acid Synthesis Inhibitors; D019014:fas Receptor; C028771:9-arabinofuranosylguanine; D006157:Guanosine Monophosphate; D006160:Guanosine Triphosphate