Histone deacetylase inhibitors as anti-neoplastic agents

Histone deacetylase inhibitors (HDACIs) constitute a novel class of targeted drugs that alter the acetylation status of histones and other important cellular proteins. These agents modulate chromatin structure leading to transcriptional changes, induce pleiotropic effects on functional pathways and activate cell death signaling in cancer cells. Anti-neoplastic activity in vitro was shown in several experimental models of cancer, but the exact mechanism of cytotoxicity and responses are not clearly understood. Phase I/II clinical trials of various HDACIs as single agents conducted to date have shown substantial activity in cutaneous T cell lymphoma (CTCL), preliminary activity in Hodgkin's disease and modest activity in myeloid neoplasms. Responses have been rare in solid tumors. Several agents are being tested in combination therapy clinical trials, either as chemosensitizers for cytotoxic chemotherapy or radiation therapy, or in association with DNA methylation inhibitors based on in vitro synergy. In this review, we focus on recent basic and clinical data that highlight the anti-neoplastic role of HDACIs.

Emerging drugs for non-small-cell lung cancer

Non-small-cell lung cancer (NSCLC) accounts for 80% of all lung cancer cases and is the leading cause of cancer mortality. Despite the optimization of chemotherapy regimens, treatment outcomes for advanced disease are still disappointing. The EGFR tyrosine kinase inhibitor, erlotinib, and the recombinant monoclonal antibody against the VEGF, bevacizumab, have proven active in NSCLC. In the BR.21 trial, a 2-month benefit in overall survival was observed for previously treated NSCLC patients who received erlotinib versus placebo. The combination of chemotherapy plus bevacizumab yielded superior overall survival or progression-free survival in one randomized trial in advanced non-squamous NSCLC patients. However, despite the introduction of more effective agents, new treatment strategies are clearly needed in lung cancer management. The review focuses on a number of new targeted agents/chemotherapy drugs now in clinical trials directed at improving NSCLC management. Mature results regarding their activity and usefulness can be expected in the near future.

Histone deacetylase inhibitors in cancer therapy

Histones are a family of nuclear proteins that interact with DNA, resulting in DNA being wrapped around a core of histone octamer within the nucleosome. Acetylation/deacetylation of histones is an important mechanism that regulates gene expression and chromatin remodeling. Histone deacetylase (HDAC) inhibitors are a new class of chemotherapeutic drugs that regulate gene expression by enhancing the acetylation of histones, and thus inducing chromatin relaxation and altering gene expression. HDAC inhibitors have been shown in preclinical studies to have potent anticancer activities. A range of structurally diverse HDAC inhibitors have been purified as natural products or synthetically produced. Due to the promising preclinical activity of these agents, numerous clinical trials have been initiated. In this review, the results of published data of single agent and combination trials of these drugs are reviewed, with a focus on dosing, scheduling and toxicity. Although still early in drug development, there is a picture that is starting to develop as to the common toxicities and which tumors seem to be the most susceptible to this class of drugs.

Recent advances in targeted therapy for non-small cell lung cancer

Non-small-cell lung cancer (NSCLC) is characterized by wide molecular heterogeneity. In recent years, novel agents that target specific, aberrant molecular pathways in NSCLC have been under rigorous evaluation. Erlotinib, an inhibitor of the epidermal growth factor receptor (EGFR) tyrosine kinase, improves survival for advanced NSCLC patients who progressed following one or two prior chemotherapy regimens. Novel molecular predictive markers, such as EGFR mutations and gene amplification, are at present under evaluation to select patients for therapy with erlotinib. Another area of progress is the recent demonstration that bevacizumab, a monoclonal antibody against the vascular endothelial growth factor (VEGF), extended survival when administered in combination with chemotherapy for patients with non-squamous NSCLC. Promising anticancer activity has also been noted with agents that inhibit the VEGF receptor tyrosine kinase in patients with advanced NSCLC. Inhibitors of the proteosomal complex, histone deacetylase, mammalian target of rapamycin pathway, and other growth factor receptor-mediated signaling are under investigation for treatment of NSCLC. These developments have paved the way for a new era of tailor-made therapies based on clinical or molecular/genetic profiles in the treatment of NSCLC. This article reviews the recent advances in targeted therapy of advanced NSCLC.