BACKGROUND: Although low-dose cytosine arabinoside (LD-Ara-C) therapy has been accepted as an effective treatment for patients with acute non-lymphocytic leukemia (ANLL) transformed from myelodysplastic syndromes or elderly patients with ANLL, the anti-leukemic mechanism remains to be resolved. Recently, the potential role of the Fas/Fas ligand system in chemotherapeutic drug-induced apoptosis has been studied. In the present study the relationship between the anti-leukemic effect of LD-Ara-C and the Fas/Fas ligand system was examined. MATERIALS AND METHODS: The human myeloid leukemia cell line HL60 was treated with LD-Ara-C in combination with anti-Fas IgM MoAb, and apoptosis in the treated cells was estimated by morphological observation, DNA electrophoresis and flow cytometry. Simultaneously, changes in Fas antigen expression on cells treated with LD-Ara-C were investigated. RESULTS: Only limited apoptosis was observed following treatment with LD-Ara-C alone or anti-Fas MoAb alone; however, a synergistic increase in apoptosis was observed by treatment with the MoAb in combination with pretreatment with LD-Ara-C. LD-Ara-C induced a slight but consistent increase in the expression of Fas antigen on the treated cells. Moreover, the expression of Fas antigen was enhanced by repeated administration of LD-Ara-C. CONCLUSIONS: These findings suggest the possible involvement of the Fas/Fas ligand system in the anti-leukemic effect of LD-Ara-C therapy.

Antibodies, Monoclonal↗

PubMedDate not supplied

Induction of apoptosis in HL60 leukemic cells by anticancer drugs in combination with anti-Fas monoclonal antibody.

Some anticancer drugs kill tumor cells through the mechanism of apoptosis. Fas antigen has been generally noticed as an apoptosis-signalling receptor molecule on the surface of different cells. Recently, it has become clear that some tumor cells express Fas antigen on their surface, and apoptosis is induced in those cells by IgM-anti-Fas monoclonal antibody (IgM-anti-Fas MoAb). If it is possible to induce apoptosis in tumor cells effectively by anticancer drugs in combination with IgM-anti-Fas MoAb, then we may be able to develop a new strategy for cancer chemotherapy. HL60 human leukemic cell line was incubated with anticancer drugs adriamycin (ADM) or cytosine arabinoside (Ara-C) at different doses alone and in combination with IgM-anti-Fas MoAb. We then observed the morphologic changes of tumor cells, the DNA fragmentation by agarose gel electrophoresis, and the changes in the amount of Fas antigen expression in their cell surface by using flow cytometry. In ADM- or Ara-C-treated tumor cells, apoptotic cells increased in number time- and dose-dependently. By the combination of ADM or Ara-C with IgM-anti-Fas MoAb, the induction of apoptosis in HL60 cells was enhanced significantly. The DNA electrophoresis supported those results. The amount of Fas antigen expression was slightly increased only in cells treated with a low dose of Ara-C, not in others. Our results suggest that apoptosis is a major process of leukemic cell death induced by anticancer drugs. Furthermore, it has become clear that the combination of anticancer drugs with IgM-anti-Fas MoAb enhances leukemic cell death through apoptosis in vitro, though the mechanism remains to be resolved.

Antibodies, Monoclonal↗