Phase II trial of the histone deacetylase inhibitor pivaloyloxymethyl butyrate (Pivanex, AN-9) in advanced non-small cell lung cancer

Histone deacetylase inhibitors: insights into mechanisms of lethality

Histone deacetylases (HDACs) have recently emerged as an important target for therapeutic intervention in cancer and potentially other human diseases. By modulating the acetylation status of histones, histone deacetylase inhibitors (HDACIs) alter the transcription of genes involved in cell growth, maturation, survival and apoptosis, among other processes. Early clinical results suggest a potentially useful role for HDACIs in the treatment of certain forms of lymphoma (e.g., cutaneous T cell lymphoma) and acute leukaemia. An unresolved question is how HDACIs induce cell death in tumour cells. Recent studies suggest that acetylation of nonhistone proteins may play an important role in the biological effects of this class of compounds, and may explain lack of correlation between histone acetylation and induction of cell death by HDACIs in some circumstances. Recently, attention has focussed on the effects of HDACIs on disruption of co-repressor complexes, induction of oxidative injury, upregulation of the expression of death receptors, generation of lipid second messengers such as ceramide, interference with the function of chaperone proteins and modulation of the activity of NF-kappaB as critical determinants of lethality. Aside from providing critical insights into the mechanism of action of HDACIs in neoplastic disease, these findings may provide a foundation for the rational development of combination studies, involving HDACIs in combination with either conventional cytotoxic drugs as well as more novel targeted agents.

Future trends in patient-reported outcomes assessment for patients with advanced-stage lung cancer receiving targeted therapy

Recent advances in cancer cell biology have led to the development of therapeutic agents that target pathways critical to the development and progression of disease. These so-called "targeted therapies" might offer patients a more tolerable alternative to traditional systemic chemotherapy that often achieves therapeutic benefit at the cost of debilitating side effects. Several targeted agents have been recently tested in clinical trials of advanced-stage lung cancer. As interest in these therapies grows, an understanding of their impact on the patient's well-being will be important. Patient-reported outcome measures such as formal assessments of health-related quality of life and disease symptoms provide a useful means for addressing the impact of therapy from the perspective of the patient. We summarize the most commonly used measures of health-related quality of life in clinical trials of advanced-stage lung cancer. Although existing measurement systems do provide adequate coverage of many important patient-related outcome issues, the advent of targeted therapies in advanced-stage lung cancer does expose several measurement gaps. We highlight some of these gaps by reviewing a representative sample of recently conducted clinical trials of targeted lung cancer therapy and offer insight as to how these gaps can be filled. We also briefly discuss a set of issues unique to patients receiving targeted therapy (eg, perceptions of treatment efficacy, treatment compliance, patient satisfaction, and treatment convenience) and consider a few methodologic concerns unique to patients with advanced cancer.

Suberoylanilide hydroxamic acid (vorinostat) represses androgen receptor expression and acts synergistically with an androgen receptor antagonist to inhibit prostate cancer cell proliferation

Growth of prostate cancer cells is initially dependent on androgens, and androgen ablation therapy is used to control tumor growth. Unfortunately, resistance to androgen ablation therapy inevitably occurs, and there is an urgent need for better treatments for advanced prostate cancer. Histone deacetylase inhibitors, such as suberoylanilide hydroxamic acid (SAHA; vorinostat), are promising agents for the treatment of a range of malignancies, including prostate cancer. SAHA inhibited growth of the androgen-responsive LNCaP prostate cancer cell line at low micromolar concentrations and induced caspase-dependent apoptosis associated with chromatin condensation, DNA fragmentation, and mitochondrial membrane depolarization at higher concentrations (>/=5 mumol/L). Gene profiling and immunoblot analyses showed a decrease in androgen receptor (AR) mRNA and protein in LNCaP cells cultured with SAHA compared with control cells, with a corresponding decrease in levels of the AR-regulated gene, prostate-specific antigen. Culture of LNCaP cells in steroid-free medium markedly sensitized the cells to SAHA. Moreover, a combination of low, subeffective doses of SAHA and the AR antagonist bicalutamide resulted in a synergistic reduction in cell proliferation and increase in caspase-dependent cell death. Addition of exogenous androgen prevented the induction of cell death, indicating that suppression of androgen signaling was required for synergy. At the subeffective concentrations, these agents had no effect, alone or in combination, on proliferation or death of AR-negative PC-3 prostate cancer cells. Our findings indicate that SAHA is effective in targeting the AR signaling axis and that androgen deprivation sensitizes prostate cancer cells to SAHA. Consequently, combinatorial treatments that target different components of the AR pathway may afford a more effective strategy to control the growth of prostate cancer cells.

Epigenetics of lung cancer

Epigenetics is the study of heritable changes in gene expression that occur without changes in DNA sequence. It has a role in determining when and where a gene is expressed during development. Perhaps the most well known epigenetic mechanism is DNA methylation whereby cytosines at position 5 in CpG dinucleotides are methylated. Histone modification is another form of epigenetic control, which is quite complex and diverse. Histones and DNA make up the nucleosome which is the structural unit of chromatin which are involved in packaging DNA. Apart from the crucial role epigenetics plays in embryonic development, transcription, chromatin structure, X chromosome inactivation and genomic imprinting, its role in an increasing number of human diseases is more and more recognized. These diseases include cancer, and lung cancer in particular has been increasingly studied for the potential biological role of epigenetic changes with the promise of better and novel diagnostic and therapeutic tools.

Epigenetic regulation of immune escape genes in cancer

According to the concept of immune surveillance, the appearance of a tumor indicates that it has earlier evaded host defenses and subsequently must have escaped immunity to evolve into a full-blown cancer. Tumor escape mechanisms have focused mainly on mutations of immune and apoptotic pathway genes. However, data obtained over the past few years suggest that epigenetic silencing in cancer may be as frequent a cause of gene inactivation as are mutations. Here, we discuss the evidence that tumor immune evasion is mediated by non-mutational epigenetic events involving chromatin and that epigenetics collaborates with mutations in determining tumor progression. Since epigenetic changes are potentially reversible, the relative contribution of mutations and epigenetics, to the gene defects in any given tumor, may be a factor in determining the efficacy of treatments. We review new developments in basic chromatin mechanisms and in this context describe the rationale for the current use of epigenetic agents in cancer therapy and for a novel epigenetically generated tumor vaccine model. We emphasize that epigenetic cancer treatments are currently a 'blunt-sword' and suggest future directions for designing chromatin-based programs of potential value in the diagnosis and treatment of cancer.

The selectivty and anti-metastatic activity of oral bioavailable butyric acid prodrugs

Acyloxyalkyl ester prodrugs of histone deacetylase inhibitors, a family of anti-cancer agents, are metabolized intracellularly to acids and aldehyde(s). The purpose of this study was to assess the in vitro and in vivo anticancer activity, selectivity and oral bioavailability of these prodrugs. The prodrugs exhibited a hierarchal potency of AN-193 > or = AN-7 > AN-1 and AN-9 >> AN-10 against murine lung carcinoma (3LLD122) and human breast carcinoma (MCF-7) cell lines. AN-9, and to even greater extent AN-7, displayed preferential cytotoxicity against leukemic and glioblastoma cells compared to their normal cellular counterparts-normal mononuclear and astrocytes cells, respectively. In vivo, anti-metastatic activity was evaluated in a metastatic model of lung cancer in which Lewis lung carcinoma (3LLD122) cells are injected intravenously into C57/BL mice and produce lung nodules. The prodrugs administered orally demonstrated a significant inhibition of lung-lesion formation and their hierarchal potency concurred with that observed in vitro, with the exception of AN-193 that was the least active compound. Escalating doses of AN-7 (5-100 mg/kg), administered by oral or intraperitoneal routes and displayed equivalent anti-metastatic activities, confirmed the good oral bioavailability of AN-7. Consistent with these findings, a time course study of histone acetylation in subcutaneously implanted 3LL122 tumors showed 2-4 fold increases in histone acetylation within 0.5 h of intravenous, intraperitoneal, or oral administration of AN-7 (100 mg/kg). Relative contributions of the prodrug metabolites to the anti-neoplastic activity and the best candidate for clinical studies are discussed.

Suberoylanilide Hydroxamic Acid Induces Akt-mediated Phosphorylation of p300, Which Promotes Acetylation and Transcriptional Activation of RelA/p65

We have previously demonstrated that the transcription factor NF-kappaB is activated by histone deacetylase inhibitors in a PI3K/Akt-dependent manner. The molecular mechanisms governing this process have not been well described. By virtue of their inhibitory action, it is unclear whether the addition of histone deacetylase inhibitors simply preserves the acetylation status of RelA/p65 or whether they actively stimulate signaling cascades that result in increased acetylation and transcription of NF-kappaB. Here we provide evidence that suberoylanilide hydroxamic acid stimulates NF-kappaB transcription through a signaling cascade that involves activation of both the serine/threonine kinase Akt and the p300 acetyltransferase. Using newly developed phosphospecific antibodies to p300 (pSer(1834)), and site-directed mutant proteins, we find that suberoylanilide hydroxamic acid stimulates Akt activity, which is required to phosphorylate p300 at Ser(1834). Akt-mediated phosphorylation of p300 dramatically increases its acetyltransferase activity as measured by an increased acetylation of RelA/p65 at Lys(310), a modification that is required for full NF-kappaB transcription. Importantly, coordinate activation of Akt/p300 pathway by suberoylanilide hydroxamic acid occurs at the chromatin level, resulting in recruitment of activated Akt (pSer(473)), p300 (pSer(1834)), acetylated RelA/p65 (Lys(310)), and RNA polymerase II to the NF-kappaB-dependent cIAP-2 and Bfl-1/A1 promoters. These studies provide evidence that histone deacetylase inhibitors, such as suberoylanilide hydroxamic acid, not only inhibit deacetylase activity but also stimulate active NF-kappaB transcription and cell survival through signaling pathways involving Akt and increased p300 acetyltransferase activity.

Short-chain fatty acid mediated phosphorylation of heat shock protein 25: effects on camptothecin-induced apoptosis

Although short-chain fatty acid (SCFA)-induced heat shock protein 25 (Hsp25) is associated with increased cellular resistance to injury, withdrawal of lumenal butyrate in vivo is associated with intestinal epithelial injury and apoptosis. Recognizing that SCFA-dependent posttranslational modification of Hsp25 may involve altered Hsp25 phosphorylation, we hypothesized that butyrate regulates Hsp25 phosphorylation and secondarily affects cellular responses to apoptosis-inducing agents. Intestinal epithelial crypt IEC-18 cells were treated with butyrate, propionate, or the histone deacetylase inhibitor trichostatin A for 6-24 h. Immunolocalization of Hsp25 was examined by confocal laser microscopy. Hsp25 phosphorylation was characterized using two-dimensional isoelectric focusing gel electrophoresis. Hsp25 accumulation in cytoskeletal- and mitochondrial-enriched fractions was examined by immunoblotting. The activation of p38 MAP kinase was determined using phospho-specific antibodies and MAPKAPK 2 kinase assays. The effects of SCFA on apoptosis were studied by ELISA detection of cleaved DNA and using antibodies recognizing cleaved caspase-3. Five-millimolar butyrate induced no significant injury to IEC-18 cells. Hsp25 did not accumulate in Triton X-100-insoluble cytoskeletal fractions with butyrate treatment but did localize to mitochondria in a p38 MAP kinase-dependent manner. Hsp25 phosphorylation was induced by butyrate, propionate, and trichostatin A. Butyrate-mediated changes in Hsp25 phosphorylation coincide with the activation of the p38 MAP kinase and MAPKAPK 2. Butyrate, propionate, and low-dose trichostatin A confer significant protection from camptothecin-induced apoptosis, which was not reversed by the p38 inhibitor SB203580. We conclude that butyrate-mediated phosphorylation of Hsp25 is associated with significant resistance to apoptosis, which appears to be independent of p38-mediated targeting of Hsp25 to mitochondria.

Mode of interaction between butyroyloxymethyl-diethyl phosphate (AN-7) and doxorubicin in MCF-7 and resistant MCF-7/Dx cell lines

PURPOSE

To investigate the anticancer activity and mode of action of butyroyloxymethyl-diethyl phosphate (AN-7), a prodrug of butyric acid and formaldehyde, as a single agent and in combination with doxorubicin in human carcinoma MCF-7 and the multidrug resistant MCF-7 Dx cell lines.

METHODS

The anti-cancer activity of AN-7 as a single agent or in combination with doxorubicin was measured by the Hoechst cell viability and colony forming assays as well as by FACS analyses of cells stained with propidium iodide and annexin V-FITC. Modulations of protein expression and acetylation were measured by Western blot analyses. The number of doxorubicin-DNA adducts formed was evaluated using (14)C-labeled doxorubicin.

RESULTS

The AN-7 and homologous prodrugs exhibited similar growth inhibition effects against drug resistant and sensitive cells, and elicited their anticancer effect partially by inhibition of HDAC. The AN-7 transiently augmented histone acetylation and increase of p21 expression. Synergy between AN-7 and doxorubicin was demonstrated in the sensitive and the resistant cell lines by viability and colony formation assays and was further confirmed by FACS analysis showing an increase in cell mortality. The number of doxorubicin-DNA adducts in total genomic DNA isolated from cells treated with (14)C-labeled doxorubicin and AN-7 increased substantially compared to treatment with doxorubicin only. Treatment with AN-7 or doxorubicin increased p53 acetylation that was further potentiated by their combination.

CONCLUSION

The AN-7 combined with doxorubicin overcame drug resistance; at least in part by the intracellularly releasable formaldehyde that augmented formation of doxorubicin-DNA adducts and butyric acid that induced histone and p53 acetylation. Since the use of doxorubicin is limited by toxicity, the combination could offer an effective treatment modality with lower toxicity for breast cancer.

The second annual symposium on the future of lung cancer: a translational focus

Lung cancer continues to be a leading cause of death in the US, and in its most advanced stages remains incurable. Cytotoxic chemotherapies have been the standard of care for the treatment of unresectable disease. However, recent advances in the development of epidermal growth factor receptor (EGFR) inhibitors have led the way to a new generation of targeted biological agents. During the second annual symposium entitled 'the future of lung cancer: a translational focus', which was sponsored by the Physician s Education Resource, new strategies for the treatment of lung cancer were discussed. Besides the role of EGFR inhibitors, potential targets include the angiogenesis pathway; other growth factor pathways, such as phosphoinositol-3 kinase/Akt and Raf-MEK; the 26S proteasome, the histone deacetylase mechanism; and the TNF-related apoptosis-inducing factor receptors. Agents that are directed against these targets are all in varying stages of clinical development. As more is learned about their mechanisms of action and clinical spectrum of activity, the author anticipates their incorporation into novel regimens with enhanced activity against lung cancer.

Cholesteryl butyrate solid lipid nanoparticles inhibit adhesion of human neutrophils to endothelial cells

1. Adhesion of polymorphonuclear cells (PMNs) to vascular endothelial cells (EC) is a critical step in recruitment and infiltration of leukocytes into tissues during inflammation. High doses of butyric acid have been shown to ameliorate inflammation in inflammatory bowel diseases (IBD). Cholesteryl-butyrate solid lipid nanoparticles (chol-but SLN) as prodrug are a possible delivery system for butyric acid. 2. Sodium butyrate or chol-but SLN were coincubated with human PMNs and human umbilical vein EC (HUVEC); adhesion was quantified by computerized microimaging fluorescence analysis. Both chol-but SLN and sodium butyrate displayed antiadhesive effects on FMLP- and IL-1beta-stimulated cells in a concentration-response curve (10(-8)-10(-5) M), but chol-but SLN were in all cases more active. Moreover, chol-but SLN inhibited FMLP-induced adhesion of PMNs to FCS-coated plastic wells, thus showing a direct effect on PMNs, while sodium butyrate had little effect. Confocal microscopy showed that fluorescent SLN entered PMNs and HUVEC after 10 min incubation. Chol-but SLN acted either on activated PMN or HUVEC. 3. Chol-but SLN inhibited O2-* production and myeloperoxidase release by PMNs evoked by FMLP, in a dose-dependent, but not time-dependent, manner and were more active than sodium butyrate. 4. In conclusion, in all tests chol-but SLN were more active than sodium butyrate. Thus, chol-but SLN might be a valid alternative to sodium butyrate in the anti-inflammatory therapy of ulcerative colitis, avoiding complications related to the administration of sodium butyrate.

Butyric acid prodrugs are histone deacetylase inhibitors that show antineoplastic activity and radiosensitizing capacity in the treatment of malignant gliomas

Histone modification has emerged as a promising approach to cancer therapy. We explored the efficacy of a novel class of histone deacetylase inhibitors in the treatment of malignant gliomas. Treatment of glioma cell lines with two butyric acid derivatives, pivaloylomethyl butyrate (AN-9) and butyroyloxymethyl butyrate (AN-1), induced hyperacetylation, increased p21(Cip1) expression, inhibited proliferation, and enhanced apoptosis. Histone deacetylase inhibitor-induced apoptosis was mediated primarily by caspase-8. Treatment of cells with AN-1 or AN-9 for 24 hours before exposure to gamma-irradiation potentiated further caspase-8 activity and resultant apoptosis. Clonogenic survival curves revealed marked reductions in cell renewal capacity of U251 MG cells exposed to combinations of AN-1 and radiation. Preliminary in vivo experiments using human glioma cell lines grown as xenografts in mouse flanks suggest in vivo efficacy of AN-9. The data suggest that novel butyric acid prodrugs provide a promising treatment strategy for malignant gliomas as single agents and in combination with radiation therapy.

The Potential of Histone Deacetylase Inhibitors in Lung Cancer

In the nucleus, DNA is wrapped around octamers of histone proteins. Histones, like other proteins, are posttranslationally modified by the addition of an array of chemical groups that affect their interactions with surrounding structures. Histone acetyltransferases and histone deacetylases (HDACs) are the enzymes involved in the addition and removal, respectively, of acetyl groups from the aminoterminal tails of histones. A number of structurally diverse compounds are capable of inhibiting HDACs and exert a variety of biologic effects on cancer cells in preclinical models. Early clinical trials with the first generation of HDAC inhibitors (HDACIs) have demonstrated promising therapeutic activity, and HDACs have become one of the hottest targets in drug development today.

Epigenetics of cervical cancer. An overview and therapeutic perspectives

Cervical cancer remains one of the greatest killers of women worldwide. It is difficult to foresee a dramatic increase in cure rate even with the most optimal combination of cytotoxic drugs, surgery, and radiation; therefore, testing of molecular targeted therapies against this malignancy is highly desirable. A number of epigenetic alterations occur during all stages of cervical carcinogenesis in both human papillomavirus and host cellular genomes, which include global DNA hypomethylation, hypermetylation of key tumor suppressor genes, and histone modifications. The reversible nature of epigenetic changes constitutes a target for transcriptional therapies, namely DNA methylation and histone deacetylase inhibitors. To date, studies in patients with cervical cancer have demonstrated the feasibility of reactivating the expression of hypermethylated and silenced tumor suppressor genes as well as the hyperacetylating and inhibitory effect upon histone deacetylase activity in tumor tissues after treatment with demethylating and histone deacetylase inhibitors. In addition, detection of epigenetic changes in cytological smears, serum DNA, and peripheral blood are of potential interest for development of novel biomolecular markers for early detection, prediction of response, and prognosis.

[Randomized controlled trial on haiguiyuyang capsule in the treatment of duodenal ulcer]

OBJECTIVE

To assess the efficacy and safety of haiguiyuyang capsule in the treatment of duodenal ulcer (also diagnosed as weiwan pain and hanrecuoza syndrome according to the theory of TCM).

METHODS

This is a multi-center clinical trial cooperatively conducted from May 2003 to March 2004 in accordance to the principle of informed consent, to the criteria for subject inclusion, exclusion, discontinuation, and to the relevant guidelines for evaluating the therapeutic effects of new TCM drugs. The design of double-blind, double-dummy and randomized controlled trial was adopted. 438 patients were randomized to the Test group (n = 330, treated with haiguiyuyang capsule) and to the Control group (n = 108, treated with ranitidine). The therapeutic course for both groups was 6 weeks.

RESULTS

Regarding the efficacy in treating duodenal ulcer, in the Test group, the Marked Efficacy Rate was 66.37% and the Total Efficacy Rate was 82.13%; in the Control group, the Marked Efficacy Rate was 68.61% and the Total Efficacy Rate was 93.34%; there was no significant difference between the two groups (P>0.05). Regarding the efficacy in treating the syndrome diagnosed by TCM, in the Test group, the Marked Efficacy Rate was 70.31% and the Total Efficacy Rate was 93.34%; in the control group, the rates were 71.29% and 91.66% respectively; there was no significant difference between the two groups (P>0.05). Besides, regarding the abatement of distention and fullness of stomach after treatment, the haiguiyuyang capsule was better than ranitidine (P<0.05). No adverse side-effect was observed.

CONCLUSION

The efficacy of haiguiyuyang capsule in treating duodenal ulcer is similar to that of ranitidine. No obvious adverse effect of it was observed in this trial.

Role of histone and transcription factor acetylation in diabetes pathogenesis

Globally, diabetes (and, in particular, type 2 diabetes) represents a major challenge to world health. Currently in the United States, the costs of treating diabetes and its associated complications exceed 100 billion US dollars annually, and this figure is expected to soar in the near future. Despite decades of intense research efforts, the genetic basis of the events involved in the pathogenesis of diabetes is still poorly understood. Diabetes is a complex multigenic syndrome primarily due to beta-cell dysfunction associated with a variable degree of insulin resistance. Recent advances have led to exciting new developments with regard to our understanding of the mechanisms that regulate insulin transcription. These include data that implicate chromatin as a critical regulator of this event. The 'Histone Code' is a widely accepted hypothesis, whereby sequential modifications to the histones in chromatin lead to regulated transcription of genes. One of the modifications used in the histone code is acetylation. This is probably the best characterized modification of histones, which is carried out under the control of histone acetyltransferases (HATs) and histone deacetylases (HDACs). These enzymes also regulate the activity of a number of transcription factors through acetylation. Increasing evidence links possible dysregulation of these mechanisms in the pathogenesis of diabetes, with important therapeutic implications.

Histone Deacetylase Inhibitors: Emerging Anticancer Therapeutic Agents?

Histone deacetylase inhibitors are novel anticancer agents in clinical development that target the family of histone deacetylase (HDAC) enzymes responsible for deacetylating core nucleosomal histones and other proteins. The precise mechanisms resulting in the antiproliferative biologic effects of these agents are not yet known, but there are several proposed mechanistic models, including transcriptional and nontranscriptional processes. Clinical experience with these agents indicates that they are generally well tolerated, and anticancer activity has been observed in early clinical trials in several tumor types including non-small-cell lung cancer. The development of these agents continues, with an emphasis on the discovery of HDAC isoform-selective compounds. Successful future development relies on clearer understanding of the dominant mechanisms involved in the observed antiproliferative effects.

The power and potential of doxorubicin-DNA adducts

Doxorubicin (trade name Adriamycin) is a widely used anticancer agent which exhibits good activity against a wide range of tumors. Although the major mode of action appears to be normally as a topoisomerase II poison, it also exhibits a number of other cellular responses, one of which is the ability to form adducts with DNA. For adduct formation doxorubicin must react with cellular formaldehyde to form an activated Schiff base which is then able to form an aminal (N-C-N) linkage to the exocyclic amino group of guanine residues. The mono-adducts form primarily at G of 5'-GCN-3' sequences where the chromophore of the drug is intercalated between the C and N base pair. The structure of the adducts has have been well defined by 2D NMR, mass spectrometry and X-ray crystallography. The formation of these anthracycline adducts in cells grown in culture has been unequivocally demonstrated. The source of formaldehyde in cells can be endogenous, provided by coadministration of prodrugs that release formaldehyde or by prior complexation of anthracyclines with formaldehyde. Since the adducts appear to be more cytotoxic than doxorubicin alone, and also less susceptible to drug-efflux forms of resistance, they offer new approaches to improving the anticancer activity of the anthracyclines.

Rational development of histone deacetylase inhibitors as anticancer agents: a review

The epigenome is defined by DNA methylation patterns and the associated post-translational modifications of histones. This histone code determines the expression status of individual genes dependent upon their localization on the chromatin. The histone deacetylases (HDACs) play a major role in keeping the balance between the acetylated and deacetylated states of chromatin and eventually regulate gene expression. Recent developments in understanding the cancer cell cycle, specifically the interplay with chromatin control, are providing opportunities for developing mechanism-based therapeutic drugs. Inhibitors of HDACs are under considerable exploration, in part because of their potential roles in reversing the silenced genes in transformed tumor cells by modulating transcriptional processes. This review is an effort to summarize the nonclinical and clinical status of HDAC inhibitors currently under development in anticancer therapy.

Predicting the effect of transcription therapy in hematologic malignancies

Molecular lesions of genes encoding for transcriptional regulatory proteins are common oncogenic events in hematologic malignancies. Transcriptional activation and repression both occur by virtue of the choreographed recruitment of multisubunit cofactor complexes to target gene loci. As a consequence, the three-dimensional structure of the target gene is altered and its potential to support transcription is increased or decreased. The complexity of the transcriptional process offers a rich substrate for designing therapeutic agents. The objective of such 'transcription therapy' is to regain control over cohorts of target genes and restore the normal genetic and epigenetic programming of the cancer cell. The success of all-trans retinoic acid in the treatment of acute promyelocytic leukemia indicates that transcription therapy can be highly effective and safe. A classification scheme of these therapeutic strategies is proposed herein, which allows predictions to be made regarding specificity, efficacy, disease spectrum and side effects. This framework could help facilitate discussion of the mechanisms of action of transcription therapy drugs as well as the design of preclinical and clinical trials in the future.

Drug Insight: histone deacetylase inhibitors—development of the new targeted anticancer agent suberoylanilide hydroxamic acid

This review focuses on the discovery and development of the histone deacetylase (HDAC) inhibitor, suberoylanilide hydroxamic acid (SAHA). Post-translational modifications of the histones of chromatin are important factors in regulating gene expression--so-called epigenetic gene regulation. Acetylation and deacetylation of lysine residues in histone tails, controlled by the activities of HDACs and histone acetyltransferases, are among the most studied post-translational modification of histones. In addition to chromatin protein, transcription factors, cell-signaling regulatory proteins, and proteins regulating cell death are substrates of HDACs and may be altered in function by HDAC inhibitors. HDAC inhibitors have several remarkable aspects. For instance, despite HDACs being ubiquitously distributed through chromatin, SAHA selectively alters the transcription of relatively few genes, and normal cells are at least 10-fold more resistant than transformed cells to SAHA and related HDAC inhibitor-induced cell death. HDAC inhibitors represent a relatively new group of targeted anticancer compounds, which are showing significant promise as agents with activity against a broad spectrum of neoplasms, at doses that are well tolerated by cancer patients. SAHA is one of the HDAC inhibitors most advanced in development. It is in phase I and II clinical trials for patients with both hematologic and solid tumors.

Targeted therapies and non-small cell lung cancer: methodological and conceptual challenge for clinical trials

PURPOSE OF REVIEW

Targeted therapies are emerging as important drugs in the treatment of advanced non-small cell lung cancer (NSCLC). Within the past months, there have been considerable contributions to this topic. The results of several important clinical trials have been published. Furthermore, laboratory results have significantly contributed to clear out some molecular mechanisms regulating sensitivity or resistance to these drugs and to provide rational basis for further clinical studies.

RECENT FINDINGS

A great part of recently published research on targeted agents in NSCLC regards EGFR inhibitors. Following the demonstration of activity of gefitinib in patients pretreated with chemotherapy, four large randomized trials testing the addition of gefitinib or erlotinib to first-line chemotherapy have been conducted, but failed to show any advantage. Interestingly, erlotinib has shown efficacy compared with placebo in pretreated patients. Mutations in the EGFR gene have shown a strong predictive role for sensitivity to EGFR inhibitors. A number of other targeted agents are currently under investigation: most of the phase II trials maintain a traditional methodology, with response rate as primary measure of activity.

SUMMARY

Recent advances will lead to a rapid expansion of further studies aimed to define the best way to use targeted agents in NSCLC. Several methodological issues are still open. The proper selection of patients, the choice of the best study design and the most appropriate end-point for early clinical trials, and the correct modality to integrate these drugs with traditional chemotherapy represent the most challenging points that research is called to answer in the near future.