title: Targeted inhibition of histone deacetylases and hedgehog signaling suppress tumor growth and homologous recombination in aerodigestive cancers.
abstract: Standard combined modality therapies for aerodigestive tract malignancies have suboptimal outcomes, and targeting cancer-specific molecular pathways in combination with radiation could improve the therapeutic ratio. Dysregulation of epigenetic modulators such as histone deacetylases (HDACs), and developmental morphogens such as the hedgehog (HH) pathway have been implicated in aerodigestive tumor progression and metastasis. We hypothesized that simultaneous targeting of HDACs and the HH-pathway mediator Smoothened (Smo) represents an opportunity to overcome therapeutic resistance in these cancers. We evaluated the effects of the HDAC inhibitor SAHA and Smo inhibitor GDC-0449 with radiation in multiple aerodigestive cancer cell lines. Isobologram analyses showed that SAHA and GDC-0449 synergistically suppressed cancer cell proliferation in vitro. SAHA and GDC-0449 cooperatively enhanced G0/G1 cell cycle arrest which was associated with up-regulation of p21(waf). GDC-0449 prevented SAHA-induced up-regulation of Gli-1 and Gli-2. Both Smo and Ptc-1 expression was cooperatively suppressed by SAHA and GDC-0449. The combination of SAHA and GDC-0449 induced radiation sensitization with 2 Gy as determined by colony formation assays and cytogenetic analyses, which correlated with higher residual γ-H2AX and 53BP1 foci. In mouse tumor xenografts of the SqCC/Y1 cell line, SAHA and GDC-0449 delayed tumor growth longer and prolonged survival more than either agent alone. In summary, we have identified synergistic effect of HDAC and HH signaling for radiosensitization to improve therapeutic outcomes for aerodigestive malignancies.
authors.affiliation: Division of Molecular Radiation Biology, Department of Radiation Oncology, Harold C. Simmons Comprehensive Cancer Center, University of Texas at Southwestern Medical Center Dallas, TX, USA.
authors.forename: Stephen G
authors.initials: SG
authors.lastname: Chun
authors.affiliation: Division of Molecular Radiation Biology, Department of Radiation Oncology, Harold C. Simmons Comprehensive Cancer Center, University of Texas at Southwestern Medical Center Dallas, TX, USA.
authors.forename: Hyunsil
authors.initials: H
authors.lastname: Park
authors.affiliation: Department of Radiation Oncology, Cancer Research Program, The Houston Methodist Research Institute Houston, TX, USA.
authors.forename: Raj K
authors.initials: RK
authors.lastname: Pandita
authors.affiliation: Department of Radiation Oncology, Cancer Research Program, The Houston Methodist Research Institute Houston, TX, USA.
authors.forename: Nobuo
authors.initials: N
authors.lastname: Horikoshi
authors.affiliation: Department of Radiation Oncology, Cancer Research Program, The Houston Methodist Research Institute Houston, TX, USA.
authors.forename: Tej K
authors.initials: TK
authors.lastname: Pandita
authors.affiliation: Division of Molecular Radiation Biology, Department of Radiation Oncology, Harold C. Simmons Comprehensive Cancer Center, University of Texas at Southwestern Medical Center Dallas, TX, USA.
authors.forename: David L
authors.initials: DL
authors.lastname: Schwartz
authors.affiliation: Division of Molecular Radiation Biology, Department of Radiation Oncology, Harold C. Simmons Comprehensive Cancer Center, University of Texas at Southwestern Medical Center Dallas, TX, USA ; Anchorage and Valley Radiation Therapy Center Anchorage, AK, USA.
authors.forename: John S
authors.initials: JS
authors.lastname: Yordy
keywords: Histone deacetylases; head and neck cancer; hedgehog; homologous recombination; lung cancer; lysine deacetylases; radiation sensitization; smoothened