Schedule-dependent synergy between the heat shock protein 90 inhibitor 17-(dimethylaminoethylamino)-17-demethoxygeldanamycin and doxorubicin restores apoptosis to p53-mutant lymphoma cell lines

Ana I. Robles, Mollie H. Wright, Bheru Gandhi, Steven S. Feis, Christin L. Hanigan, Adrian Wiestner, Lyuba Varticovski

Research output: Contribution to journalArticle

Abstract

Purpose: Loss of p53 function impairs apoptosis induced by DNA-damaging agents used for cancer therapy. Here, we examined the effect of the heat shock protein 90 (HSP90) inhibitor 17-(dimethylaminoethylamino)-17- demethoxygeldanamycin (DMAG) on doxorubicin-induced apoptosis in lymphoma. We aimed to establish the optimal schedule for administration of both drugs in combination and the molecular basis for their interaction. Experimental Design: Isogenic lymphoblastoid and nonisogenic lymphoma cell lines differing in p53 status were exposed to each drug or combination. Drug effects were examined using Annexin V, active caspase-3, cell cycle, and cytotoxicity assays. Synergy was evaluated by median effect/combination index. Protein expression and kinase inhibition provided insight into the molecular mechanisms of drug interaction. Results: Presence of mutant p53 conferred increased survival to single agents. Nevertheless, DMAG showed synergistic toxicity with doxorubicin independently of p53 status. Synergy required exposure to doxorubicin before DMAG. DMAG-mediated down-regulation of CHK1, a known HSP90 client, forced doxorubicin-treated cells into premature mitosis followed by apoptosis. A CHK1 inhibitor, SB-218078, reproduced the effect of DMAG. Administration of DMAG before doxorubicin resulted in G1-S arrest and protection from apoptosis, leading to additive or antagonistic interactions that were exacerbated by p53 mutation. Conclusions: Administration of DMAG to doxorubicin-primed cells induced premature mitosis and had a synergistic effect on apoptosis regardless of p53 status. These observations provide a rationale for prospective clinical trials and stress the need to consider schedule of exposure as a critical determinant of the overall response when DMAG is combined with chemotherapeutic agents for the treatment of patients with relapsed/refractory disease.

Original languageEnglish (US)
Pages (from-to)6547-6556
Number of pages10
JournalClinical Cancer Research
Volume12
Issue number21
DOIs
StatePublished - Nov 1 2006

ASJC Scopus subject areas

  • Oncology
  • Cancer Research

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