Epigenetic reprogramming in cancer: From diagnosis to treatment

Disruption of the epigenetic program of gene expression is a hallmark of cancer that initiates and propagates tumorigenesis. Altered DNA methylation, histone modifications and ncRNAs expression are a feature of cancer cells. The dynamic epigenetic changes during oncogenic transformation are related to tumor heterogeneity, unlimited self-renewal and multi-lineage differentiation. This stem cell-like state or the aberrant reprogramming of cancer stem cells is the major challenge in treatment and drug resistance. Given the reversible nature of epigenetic modifications, the ability to restore the cancer epigenome through the inhibition of the epigenetic modifiers is a promising therapy for cancer treatment, either as a monotherapy or in combination with other anticancer therapies, including immunotherapies. Herein, we highlighted the main epigenetic alterations, their potential as a biomarker for early diagnosis and the epigenetic therapies approved for cancer treatment.

Roles of Histone Deacetylases and Inhibitors in Anticancer Therapy

Histones are the main structural proteins of eukaryotic chromatin. Histone acetylation/ deacetylation are the epigenetic mechanisms of the regulation of gene expression and are catalyzed by histone acetyltransferases (HAT) and histone deacetylases (HDAC). These epigenetic alterations of DNA structure influence the action of transcription factors which can induce or repress gene transcription. The HATs catalyze acetylation and the events related to gene transcription and are also responsible for transporting newly synthesized histones from the cytoplasm to the nucleus. The activity of HDACs is mainly involved in silencing gene expression and according to their specialized functions are divided into classes I, II, III and IV. The disturbance of the expression and mutations of HDAC genes causes the aberrant transcription of key genes regulating important cancer pathways such as cell proliferation, cell-cycle regulation and apoptosis. In view of their role in cancer pathways, HDACs are considered promising therapeutic targets and the development of HDAC inhibitors is a hot topic in the search for new anticancer drugs. The present review will focus on HDACs I, II and IV, the best known inhibitors and potential alternative inhibitors derived from natural and synthetic products which can be used to influence HDAC activity and the development of new cancer therapies.

Emerging promise of epigenetics and DNA methylation for the diagnosis and management of women's cancers

Over the last two decades, survival rates from women's cancers (breast, ovarian, endometrial and cervical cancer) have all but modestly improved despite huge efforts from both research and clinical communities. In parallel with this, the field of epigenetics has grown from its infancy into a promising scientific discipline. In particular, DNA methylation analysis has been adopted by oncologists in an attempt to better understand and manage cancer. Now that the epigenetic technological base has caught up, the potential of methylation markers in cancer research is finally being realized. In this review, we present the current status of epigenetic research into women's cancers with a main focus on DNA methylation analysis. We provide an overview of technological development, current markers of risk prediction, early detection, diagnosis, prognosis and response to treatment, and highlight the progression of epigenetic therapies. Finally, we comment on the potential impact of epigenetic analyses on the future of women's health.

A phase II evaluation of belinostat and carboplatin in the treatment of recurrent or persistent platinum-resistant ovarian, fallopian tube, or primary peritoneal carcinoma: a Gynecologic Oncology Group study

BACKGROUND

Patients with recurrent ovarian cancer have limited options, especially in the context of relapse less than six months from primary platinum-based therapy. This Gynecologic Oncology Group (GOG) study was conducted to evaluate the impact of the histone deacetylase inhibitor, belinostat, in combination with carboplatin in women with platinum-resistant ovarian cancer.

METHODS

Eligible patients had measurable, recurrent disease within six months of their last dose of a platinum-based combination. Belinostat was dosed at 1000 mg/m(2) daily for five days with carboplatin AUC 5 on day three of 21-day cycles. The primary endpoint was overall response rate (ORR), using a two-stage design.

RESULTS

Twenty-nine women enrolled on study and 27 were evaluable. The median number of cycles given was two (range 1-10). One patient had a complete response and one had a partial response, for an ORR of 7.4% (95% CI, .9%-24.3%). Twelve patients had stable disease while eight had increasing disease. Response could not be assessed in five (18.5%). Grade 3 and 4 events occurring in more than 10% of treated patients were uncommon and limited to neutropenia (22.2%), thrombocytopenia (14.8%), and vomiting (11.1%). The median progression-free survival (PFS) was 3.3 months and overall survival was 13.7 months. PFS of at least six months was noted in 29.6% of patients. Due to the lack of drug activity, the study was closed after the first-stage.

CONCLUSIONS

The addition of belinostat to carboplatin had little activity in a population with platinum-resistant ovarian cancer.

Belinostat: clinical applications in solid tumors and lymphoma

INTRODUCTION

Histone deacetylase (HDAC) inhibitors have recently emerged as a novel and active class of anticancer agents. Belinostat is one member of the class that has been tested as a single agent and in combination with other chemotherapies and biological agents in the treatment of solid tumors and lymphoma.

AREAS COVERED

A literature search of pre-clinical and clinical studies of belinostat was performed. The data from these studies were analysed to summarise the progress of belinostat from Phase I to a current pivotal trial in peripheral T-cell lymphoma. The parallel development of appropriate biomarker analysis is also discussed.

EXPERT OPINION

Belinostat has demonstrated significant clinical activity in T-cell lymphomas. Although its activity as a single agent in solid tumors has been less compelling, the emerging results from combination trials are promising. However, the basis for the activity of belinostat, like that of other HDAC inhibitors, remains to be truly defined and the identification of predictive and prognostic biomarkers of activity should be established to further progress the development of this compound.

[Histone deacetylase inhibitors: highlight on epigenetic regulation]

HDAC, by modifiing relations between DNA and histones, are major proteins of the epigenetic regulation. They play part in the signal transduction and in many cellular processes: cell cycle control, apoptosis, protein degradation, angiogenesis, invasion and cell motility. In several models of cancer HDAC inhibitors (HDACIs) are able to up regulate tumor suppressing gene (p53, p21, pRB...) and to down regulate oncogenes (SRC, HIF-Ialpha,HER2...). Many inhibitors are currently in clinical development and promising results have been reported in cutaneous T cell lymphoma, Hodgkin's disease and non-hodgkin lymphoma. Combination with chemotherapy and molecular targeted agents seem to be effective in myeloma, lung cancer and myeloïd neoplasms. In this review, we focus on recent biologic and clinical data that highlitght the anti-neoplastic role of HDACIs.

Histone deacetylase inhibitors in cancer therapy

PURPOSE OF REVIEW

The purpose of this review is to provide an overview of recent advances in the development of histone deacetylase inhibitors (HDACi) for the treatment of cancer.

RECENT FINDINGS

Recently, there has been a dramatic expansion of HDACi clinical investigation. There are now 11 HDACi in clinical trial, including inhibitors with a broad spectrum of HDAC isoform inhibitory activity as well as drugs with isoform selectivity. Over 70 combination therapy trials are in progress. Major areas of progress covered include the entry of new HDAC inhibitors into clinical development, recent progress in understanding of molecular mechanisms of HDACi anticancer activity, and a preclinical and clinical update on HDACi in combination.

SUMMARY

In the period under review there have been advances in understanding of HDACi mechanisms of action, identification of rational combinations that address increased efficacy and overcoming resistance, and greatly expanded clinical development of pan-HDAC-inhibitory and isoform-selective inhibitors in monotherapy and combination therapy protocols.