Abstract
Hypophosphorylation of retinoblastoma protein (RB) accompanies the DNA damage-induced, p53-independent G1 arrest and apoptosis in two p53-null human leukemic cell lines, HL-60 and U937 (Q. P. Dou et al., Proc. Natl. Acad. Sci. USA, 92: 9019–9023, 1995). When an HL-60 cell line resistant to cytosine arabinoside was exposed to this DNA-damaging agent, neither RB hypophosphorylation nor apoptosis were observed. In contrast, treatment of these cells with another DNA-damaging agent, etoposide, dramatically induced these events, which were inhibitable by the addition of zinc chloride, a protein tyrosine phosphatase inhibitor. Induction of hypophosphorylation of RB may be an important novel strategy for treating drug-resistant cancers.
Footnotes
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↵1 Supported by a start-up fund from the Department of Pharmacology, University of Pittsburgh School of Medicine (to Q.P.D.).
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↵2 To whom requests for reprints should be addressed, at Department of Pharmacology, University of Pittsburgh School of Medicine, W952 Biomedical Science Tower, 200 Lothrop Street, Pittsburgh, PA 15213-2582.
- Received September 19, 1995.
- Accepted October 5, 1995.
- ©1995 American Association for Cancer Research.
Volume 55, Issue 22
