Arabinosylguanine-induced apoptosis of T-lymphoblastic cells: incorporation into DNA is a necessary step.

Abstract

9-Beta-D-Arabinosylguanine (ara-G) is a recently introduced and effective treatment for T-cell acute lymphoblastic leukemia, but how ara-G and ara-G triphosphate (ara-GTP) kill cells is not known. We hypothesized that, in cycling T-lymphoblastoid cells, ara-G may act directly by incorporation into DNA, which may lead to apoptosis. Hence, blocking the incorporation of ara-G monophosphate (ara-GMP) into DNA may prevent apoptosis. To test this hypothesis, we performed experiments in a T-lymphoblastic leukemia cell line (CCRF-CEM) after synchronization with a double aphidicolin block. Intracellular accumulation of ara-GTP was neither cell cycle dependent nor affected by aphidicolin (53 +/- 5 microM/h without aphidicolin, 50 +/- 5 microM/h with aphidicolin). Cells at the G1-S boundary accumulated 75 +/- 7 microM ara-GTP with minimal incorporation into DNA (5 +/- 2 pmol ara-GMP/mg DNA) and had little biochemical or morphological evidence of apoptosis. In marked contrast, cells in S phase had significantly more ara-G incorporated into DNA (24 +/- 4 pmol ara-GMP/mg DNA), although the cytosolic concentration of ara-GTP (85 +/- 7 microM) was similar to that in the G1-enriched population. In the S-phase cells, there was a corresponding increase in apoptosis (measured as high molecular weight DNA fragmentation and morphological changes), and the incorporation of ara-GTP into DNA resulted in a >95% inhibition of DNA synthesis. There was a direct linear relationship between the number of cells in S phase and both the total number of ara-GMP molecules in DNA and the inhibition of DNA synthesis. Blocking of ara-GTP incorporation into S-phase DNA abolished biochemical and morphological features of apoptosis, even in the presence of cytotoxic level of intracellular ara-GTP. Taken together, these data demonstrate that the incorporation of ara-GTP into DNA is the critical event that mediates the induction of apoptosis in CCRF-CEM cells.

• Authors: C O Rodriguez Jr, V Gandhi
• Journal: Cancer research (Cancer Res) Vol. 59 Issue 19 Pg. 4937-43 (Oct 01 1999) ISSN: 0008-5472 [Print] United States
• PMID: 10519407 (Publication Type: Journal Article, Research Support, U.S. Gov't, P.H.S.)

Chemical References

• Antineoplastic Agents
• Arabinonucleosides
• DNA, Neoplasm
• 9-arabinofuranosylguanine
• Aphidicolin

Topics

• Antineoplastic Agents (pharmacokinetics, toxicity)
• Aphidicolin (toxicity)
• Apoptosis (drug effects, physiology)
• Arabinonucleosides (pharmacokinetics, toxicity)
• Cell Cycle (drug effects)
• DNA Fragmentation
• DNA, Neoplasm (biosynthesis)
• G1 Phase
• Humans
• Kinetics
• Leukemia-Lymphoma, Adult T-Cell
• S Phase
• T-Lymphocytes (drug effects)
• Time Factors
• Tumor Cells, Cultured