Combining PCI-24781, a novel histone deacetylase inhibitor, with chemotherapy for the treatment of soft tissue sarcoma

Gonzalo Lopez, Juehui Liu, Wenhong Ren, Wei Wei, Suizhao Wang, Guy Lahat, Quan Sheng Zhu, William G. Bornmann, David J. McConkey, Raphael E. Pollock, Dina C. Lev

Research output: Contribution to journalArticlepeer-review

67 Scopus citations


Purpose: Histone deactylase inhibitors (HDACi) are a promising new class of anticancer therapeutics; however, little is known about HDACi activity in soft tissue sarcoma (STS), a heterogeneous cohort of mesenchymal origin malignancies. Consequently, we investigated the novel HDACi PCI-24781, alone/in combination with conventional chemotherapy, to determine its potential anti-STS-related effects and the underlying mechanisms involved. Experimental Design: Immunoblotting was used to evaluate the effects of PCI-24781 on histone and nonhistone protein acetylation and expression of potential downstream targets. Cell culture-based assays were utilized to assess the effects of PCI-24781 on STS cell growth, cell cycle progression, apoptosis, and chemosensitivity. Quantitative reverse transcription-PCR, chromatin immunoprecipitation, and reporter assays helped elucidate molecular mechanisms resulting in PCI-24781-induced Rad51 repression. The effect of PCI-24781, alone or with chemotherapy, on tumor and metastatic growth was tested in vivo using human STS xenograft models. Results: PCI-24781 exhibited significant anti-STS proliferative activity in vitro, inducing S phase depletion, G2/M cell cycle arrest, and increasing apoptosis. Superior effects were seen when combined with chemotherapy. A PCI-24781-induced reduction in Rad51, a major mediator of DNA double-strand break homologous recombination repair, was shown and may be a mechanism underlying PCI-24781 chemosensitization. We showed that PCI-24781 transcriptionally represses Rad51 through an E2F binding-site on the Rad51 proximal promoter. Although single-agent PCI-24781 had modest effects on STS growth and metastasis, marked inhibition was observed when combined with chemotherapy. Conclusions: In light of these findings, this novel molecular-based combination may be applicable to multiple STS histologic subtypes, and potentially merits rigorous evaluation in human STS clinical trials.

Original languageEnglish
Pages (from-to)3472-3483
Number of pages12
JournalClinical Cancer Research
Issue number10
StatePublished - 15 May 2009
Externally publishedYes


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