Combination of Proteasome and HDAC Inhibitors for Uterine Cervical Cancer Treatment

Abstract

Purpose: Cervical cancer cells are addicted to the expression of the human papillomavirus (HPV) oncoproteins E6 and E7. The oncogencity of E6 is mediated in part by targeting p53 and PDZfamily tumor suppressor proteins for rapid proteasomal degradation, whereas the E7 oncoprotein acts in part by coopting histone deacetylases (HDAC)1/2. Here, we examine the hypothesis that inhibition of proteasome function and HDAC activity would synergistically and specifically trigger cervical cancer cell death by the interruption of E6 and E7 signaling. Experimental Design: The sensitivity and molecular responses of keratinocytes and HPVpositive and HPV-negative cervical cancer cells and xenografts to combinations of proteasome and HDAC inhibitors were tested. The expression of HDAC1/HDAC2 in situ was examined in cervical cancer, its precursors, and normal epithelium. Results: Cervical cancer cell lines exhibit greater sensitivity to proteasome inhibitors than do HPV-negative cervical cancers or primary human keratinocytes. Treatment of cervical cancer cells with bortezomib elevated the level of p53 but not hDlg, hScribble or hMAGI. Immunohistochemical analysis revealed elevated HDAC1/HDAC2 expression in cervical dysplasia and cervical carcinoma versus normal cervical epithelium. The combination of bortezomib and HDAC inhibitor trichostatin A or vorinostat shows synergistic killing of HPV-positive, but not HPV-negative, cervical cancer cell lines. Similarly, treatment of HeLa xenografts with the combination of bortezomib and trichostatin A retarded tumor growth significantly more effectively than either agent alone. Conclusions: A combination of proteasome and HDAC inhibitors, including bortezomib and vorinostat, respectively, warrants exploration for the treatment of cervical cancer.Persistent infection with an oncogenic-type human papillomavirus (HPV), most commonly HPV16 and HPV18, is a necessary but insufficient cause of cervical cancer (1). HPV DNA is detected in 99.7% of cervical cancers (2), as well as a large proportion of other anogenital cancers, and also in a subset of head and neck cancers. Although cytologic screening and HPV vaccines are effective preventive measures, there are currently no virus-specific therapies for cervical cancer, and the efficacy of standard surgical and chemo/radiotherapies is limited for advanced disease. Expression of two viral oncogenes, E6 and E7, is critical for the induction and maintenance of the transformed phenotype and is lacking from normal cells (3 -6). This suggests that E6 and E7 are logical targets for rational therapeutic approaches and that inhibitors should target the functions of both oncoproteins (4). Although neither has intrinsic enzymic activity, genetic and biochemical studies have defined key cellular partners through which these viral proteins transform cells (7,8).E6 exerts one important aspect of its oncogenic activity by binding to the HECT (homologous to the E6-AP Carboxyl Terminus) domain E3 ubiquitin ligase E6-AP (and possibly other ubiquitin lig...

Histone deacetylase inhibitors induce thyroid cancer-specific apoptosis through proteasome-dependent inhibition of TRAIL degradation

“…Moreover, we show that the combination of HDACi with a proteasome inhibitor has a much higher efficacy, with respect to the treatment with HDACi alone, inducing the death of cell lines deriving from ATCs. In agreement with our findings, the synergism of proteasome inhibitors with HDACis has recently been reported in glioma, in cervical cancer and in leukemia (Miller et al, 2007(Miller et al, , 2009Dai et al, 2008;Yu et al, 2008;Lin et al, 2009), strongly supporting our molecular model and suggesting the application of this combined treatment in other types of cancers.…”

Histone deacetylase inhibitor (SAHA) and repression of EZH2 synergistically inhibit proliferation of gallbladder carcinoma

“…(16,17) Recently, several reports showed that HDACs are strongly expressed in cancerous tissue, and the expression of class I HDACs is an independent prognostic marker in various cancers, such as ovarian, colorectal and cervical cancer. (32)(33)(34) The present study showed that HDAC1 ⁄ 2 were expressed in the nuclei of non-neoplastic epithelial cells and carcinoma cells in the gallbladder, although nuclear staining was slightly weaker in the former than in the latter. This pattern was verified in cultured normal epithelial and carcinoma cells, indicating that HDAC1 ⁄ 2 expression level is a little higher in cancerous tissue; however, its expression is not specific to carcinoma cells in the gallbladder.…”

Viral epigenomes in human tumorigenesis

“…In addition to DNA methylation, the role of histone marks and chromatin remodeling factors in viral and host genome alterations has prompted the in vitro investigation of the effects of epigenetic drugs that target histone modification proteins, such as HDACs (Jiang et al, 2007;Lin et al, 2009). Furthermore, it has been proposed that the combination of epigenetic and conventional antiviral therapies, for example, unmasks HIV reservoirs and prevents the spread of the virus to uninfected CD4 þ T cells (Richman et al, 2009).…”