Pro-apoptotic and terminal differentiation activity of a 6 base length phosphodiester oligonucleotide, OligomodulatorTM BT 99-25, towards leukemia cells.

MC Filion, PhD, B Filion, S Ménard, J Roy, S Reader, NC Phillips

Bioniche Life Sciences Inc, Bioniche Therapeutics division, Montreal, Quebec Canada

AIM: We have developed a series of non-antisense 6 base length phosphodiester ODN with the ability to inhibit the cellular division of cancer cells. The ability of the OligomodulatorTM BT 99-25 to inhibit the division of acute lymphocytic leukemia (ALL) and chronic myeloid leukemia (CML) cells was evaluated. METHODS: Jurkat T cells (ALL) and K562 cells (CML) were treated with BT 99-25 for 24-72 h. Cell number was evaluated using a Coulter Counter and cell cycle analysis by flow cytometry. Apoptosis was monitored by measurement of phosphatidylserine translocation, the release of nuclear mitotic apparatus protein and the presence of fragmented DNA. Cell differentiation was determined by flow cytometry using different cell surface markers: CD41a (megakaryocyte), RhD (erythrocyte) and CD14 (monocyte). RESULTS: We found that BT 99-25 caused a time- and concentration- dependent inhibition of Jurkat T and K562 leukemia cell division. The cell division arrest observed with BT 99-25 was associated with the induction of apoptosis in Jurkat T cells and with terminal differentiation in K562 cells. Apoptosis induction in Jurkat T cells was associated with activation of the caspase pathway and cleavage of poly (ADP-ribose) polymerase. The cell division arrest observed with K562 was associated with terminal differentiation into megakaryocyte-like, monocyte-like or erythrocyte-like cells. In addition, BT 99-25 stimulated the synthesis of both adult and fetal hemoglobin by K562 cells. CONCLUSIONS: We have identified a 6 base length phosphodiester ODN that blocks the cellular division of leukemia cells by either inducing apoptosis or causing differentiation. These oligonucleotides may have potential for the treatment of either ALL or CML as inducer of apoptosis or terminal differentiation.

KEY WORDS: acute lymphocytic leukemia, chronic myeloid leukemia, caspase, poly (ADP-ribose) polymerase, hemoglobin.

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Paper presented at the International Symposium on Predictive Oncology and Intervention Strategies; Paris, France; February 9 - 12, 2002; in the section on Apoptosis - Molecular Mechanisms.