Evaluation of azacitidine and entinostat as sensitization agents to cytotoxic chemotherapy in preclinical models of non-small cell lung cancer

Epigenetic changes driven by environmental pollutants in lung carcinogenesis: a comprehensive review

Lung cancer remains the leading cause of cancer-related mortality globally, with environmental pollutants identified as significant risk factors, especially for nonsmokers. The intersection of these pollutants with epigenetic mechanisms has emerged as a critical area of interest for understanding the etiology and progression of lung cancer. Epigenetic changes, including DNA methylation, histone modifications, and non-coding RNAs, can induce alterations in gene expression without affecting the DNA sequence and are influenced by environmental factors, contributing to the transformation of normal cells into malignant cells. This review assessed the literature on the influence of environmental pollutants on lung cancer epigenetics. A comprehensive search across databases such as PubMed, Web of Science, Cochrane Library, and Embase yielded 3,254 publications, with 22 high-quality papers included for in-depth analysis. These studies demonstrated the role of epigenetic markers, such as DNA methylation patterns of genes like F2RL3 and AHRR and alterations in the miRNA expression profiles, as potential biomarkers for lung cancer diagnosis and treatment. The review highlights the need to expand research beyond homogenous adult male groups typically found in high-risk occupational environments to broader population demographics. Such diversification can reduce biases and enhance the relevance of findings to various clinical contexts, fostering the development of personalized preventive and therapeutic measures. In conclusion, our findings underscore the potential of innovative epigenetic therapies, such as DNA demethylating drugs and histone modification agents, to counter environmental toxins' carcinogenic effects. The growing interest in miRNA therapies and studies aiming to correct aberrant methylation patterns indicate significant strides toward better lung cancer management and a healthier future for global communities.

Entinostat Enhances the Efficacy of Chemotherapy in Small Cell Lung Cancer Through S-phase Arrest and Decreased Base Excision Repair

PURPOSE

Acquired chemoresistance is a frequent event in small cell lung cancer (SCLC), one of the deadliest human malignancies. Histone deacetylase inhibitors (HDACi) have been shown to synergize with different chemotherapeutic agents including cisplatin. Accordingly, we aimed to investigate the dual targeting of HDAC inhibition and chemotherapy in SCLC.

EXPERIMENTAL DESIGN

The efficacy of HDACi and chemotherapy in SCLC was investigated both in vitro and in vivo. Synergistic drug interactions were calculated based on the HSA model (Combenefit software). Results from the proteomic analysis were confirmed via ICP-MS, cell-cycle analysis, and comet assays.

RESULTS

Single entinostat- or chemotherapy significantly reduced cell viability in human neuroendocrine SCLC cells. The combination of entinostat with either cisplatin, carboplatin, irinotecan, epirubicin, or etoposide led to strong synergy in a subset of resistant SCLC cells. Combination treatment with entinostat and cisplatin significantly decreased tumor growth in vivo. Proteomic analysis comparing the groups of SCLC cell lines with synergistic and additive response patterns indicated alterations in cell-cycle regulation and DNA damage repair. Cell-cycle analysis revealed that cells exhibiting synergistic drug responses displayed a shift from G1 to S-phase compared with cells showing additive features upon dual treatment. Comet assays demonstrated more DNA damage and decreased base excision repair in SCLC cells more responsive to combination therapy.

CONCLUSIONS

In this study, we decipher the molecular processes behind synergistic interactions between chemotherapy and HDAC inhibition. Moreover, we report novel mechanisms to overcome drug resistance in SCLC, which may be relevant to increasing therapeutic success.

Enhanced Codelivery of Gefitinib and Azacitidine for Treatment of Metastatic-Resistant Lung Cancer Using Biodegradable Lipid Nanoparticles

Lung cancer is a formidable challenge in clinical practice owing to its metastatic nature and resistance to conventional treatments. The codelivery of anticancer agents offers a potential solution to overcome resistance and minimize systemic toxicity. The encapsulation of these agents within nanostructured lipid carriers (NLCs) provides a promising strategy to enhance lymphatic delivery and reduce the risk of relapse. This study aimed to develop an NLC formulation loaded with Gefitinib and Azacitidine (GEF-AZT-NLC) for the treatment of metastatic-resistant lung cancer. The physicochemical properties of the formulations were characterized, and in vitro drug release was evaluated using the dialysis bag method. The cytotoxic activity of the GEF-AZT-NLC formulations was assessed on a lung cancer cell line, and hemocompatibility was evaluated using suspended red blood cells. The prepared formulations exhibited nanoscale size (235-272 nm) and negative zeta potential values (-15 to -31 mV). In vitro study revealed that the GEF-AZT-NLC formulation retained more than 20% and 60% of GEF and AZT, respectively, at the end of the experiment. Hemocompatibility study demonstrated the safety of the formulation for therapeutic use, while cytotoxicity studies suggested that the encapsulation of both anticancer agents within NLCs could be advantageous in treating resistant cancer cells. In conclusion, the GEF-AZT-NLC formulation developed in this study holds promise as a potential therapeutic tool for treating metastatic-resistant lung cancer.

Epigenetic inhibitors for cancer treatment

Epigenetics is a heritable and reversible modification that occurs independent of the alteration of primary DNA sequence but remarkably affects genetic expression. Aberrant epigenetic regulators are frequently observed in cancer progression not only influencing the behavior of tumor cells but also the tumor-associated microenvironment (TME). Increasing evidence has shown their great potential as biomarkers to predict clinical outcomes and chemoresistance. Hence, targeting the deregulated epigenetic regulators would be a compelling strategy for cancer treatment. So far, current epigenetic drugs have shown promising efficacy in both preclinical trials and clinical treatment of cancer, which encourages research discoveries on the development of novel epigenetic inhibitors either from natural compounds or artificial synthesis. However, only a few have been approved by the FDA, and more effort needs to be put into the related research. This chapter will update the applications and latest progress of epigenetic inhibitors in cancer treatment and provide prospects for the future development of epigenetic drugs.

Histone Modification in NSCLC: Molecular Mechanisms and Therapeutic Targets

Lung cancer is the leading cause of cancer mortality in both genders, with non-small cell lung cancer (NSCLC) accounting for about 85% of all lung cancers. At the time of diagnosis, the tumour is usually locally advanced or metastatic, shaping a poor disease outcome. NSCLC includes adenocarcinoma, squamous cell carcinoma, and large cell lung carcinoma. Searching for novel therapeutic targets is mandated due to the modest effect of platinum-based therapy as well as the targeted therapies developed in the last decade. The latter is mainly due to the lack of mutation detection in around half of all NSCLC cases. New therapeutic modalities are also required to enhance the effect of immunotherapy in NSCLC. Identifying the molecular signature of NSCLC subtypes, including genetics and epigenetic variation, is crucial for selecting the appropriate therapy or combination of therapies. Epigenetic dysregulation has a key role in the tumourigenicity, tumour heterogeneity, and tumour resistance to conventional anti-cancer therapy. Epigenomic modulation is a potential therapeutic strategy in NSCLC that was suggested a long time ago and recently starting to attract further attention. Histone acetylation and deacetylation are the most frequently studied patterns of epigenetic modification. Several histone deacetylase (HDAC) inhibitors (HDIs), such as vorinostat and panobinostat, have shown promise in preclinical and clinical investigations on NSCLC. However, further research on HDIs in NSCLC is needed to assess their anti-tumour impact. Another modification, histone methylation, is one of the most well recognized patterns of histone modification. It can either promote or inhibit transcription at different gene loci, thus playing a rather complex role in lung cancer. Some histone methylation modifiers have demonstrated altered activities, suggesting their oncogenic or tumour-suppressive roles. In this review, patterns of histone modifications in NSCLC will be discussed, focusing on the molecular mechanisms of epigenetic modifications in tumour progression and metastasis, as well as in developing drug resistance. Then, we will explore the therapeutic targets emerging from studying the NSCLC epigenome, referring to the completed and ongoing clinical trials on those medications.

Epigenetics of lung cancer: a translational perspective

BACKGROUND

Lung cancer remains the most common cause of cancer-related death, with a 5-year survival rate of only 18%. In recent years, the development of targeted pharmacological agents and immunotherapies has substantially increased the survival of a subset of patients. However, most patients lack such efficacious therapy and are, thus, treated with classical chemotherapy with poor clinical outcomes. Therefore, novel therapeutic strategies are urgently needed. In recent years, the development of epigenetic assays and their application to cancer research have highlighted the relevance of epigenetic regulation in the initiation, development, progression and treatment of lung cancer.

CONCLUSIONS

A variety of epigenetic modifications do occur at different steps of lung cancer development, some of which are key to tumor progression. The rise of cutting-edge technologies such as single cell epigenomics is, and will continue to be, crucial for uncovering epigenetic events at a single cell resolution, leading to a better understanding of the biology underlying lung cancer development and to the design of novel therapeutic options. This approach has already led to the development of strategies involving single agents or combined agents targeting epigenetic modifiers, currently in clinical trials. Here, we will discuss the epigenetics of every step of lung cancer development, as well as the translation of these findings into clinical applications.

Paradoxical Role of Glypican-1 in Prostate Cancer Cell and Tumor Growth

Recent studies suggest that glypican-1 (GPC-1) is a biomarker for prostate cancer, but there are few studies elucidating the role of GPC-1 in prostate cancer progression. We observed high expression of GPC-1 in more aggressive prostate cancer cell lines such as PC-3 and DU-145. While inhibition of GPC-1 expression in PC-3 cells decreased cell growth and migration in vitro, it surprisingly increased cell proliferation and migration in DU-145 cells, suggesting that the role of GPC-1 is cell type-dependent. Further, GPC-1 inhibition increased PC-3 tumor size in NCr nude mice xenografts. We hypothesized that the discrepancy between the in vitro and in vivo data is mediated by stromal cells in the tumor microenvironment. Thus, we tested the effect of tumor conditioned media (TCM) on gene expression in human mesenchymal stem cells and fibroblasts. Treatment of stromal cells with TCM from PC-3 cells transfected with GPC-1 shRNA increased the expression of migration markers, endocrine/paracrine biomolecules, and extracellular matrix components. Additionally, the decreased cell growth in GPC-1 knockdown PC-3 cells was rescued by coculturing with stromal cells. These data demonstrate the paradoxical role that GPC-1 plays in prostate cancer cell growth by interacting with stromal cells and through ECM remodeling and endocrine/paracrine signaling.

Determinants of immunological evasion and immunocheckpoint inhibition response in non-small cell lung cancer: the genetic front

The incorporation into clinical practice of immune-checkpoint inhibitors (ICIs), such as those targeting the cytotoxic T lymphocyte-associated antigen 4 (CTLA-4) and the programmed cell death 1 (PD-1) and its ligand (PD-L1), has represented a major breakthrough in non-small cell lung cancer (NSCLC) treatment, especially in cases where the cancer has no druggable genetic alterations. Despite becoming the standard of care in certain clinical settings, either alone or in combination with chemotherapy, a proportion of patients do not respond while others actually progress during treatment. Therefore, there is a clinical need to identify accurate predictive biomarkers and to develop novel therapeutic strategies based on ICIs. Although they have limitations, the current markers evaluated to select which patients will undergo ICI treatment are the levels of PD-L1 and the tumor mutational burden. In this paper we describe what is currently known about the dynamic interaction between the cancer cell and the immune system during carcinogenesis, with a particular focus on the description of the functions and gene alterations that preclude the host immunoresponse in NSCLC. We emphasize the deleterious gene alterations in components of the major histocompatibility complex (HLA-I or B2M) and of the response to IFNγ (such as JAK2) which are mutually exclusive and can affect up to one fifth of the NSCLCs. The participation of other gene alterations, such as those of common oncogenes and tumor suppressors, and of the epigenetic alterations will also be discussed, in detail. Finally, we discuss the potential use of the tumor's genetic profile to predict sensitivity to ICIs.

Unmasking the pathological and therapeutic potential of histone deacetylases for liver cancer

Hepatocellular carcinoma (HCC) is the most common form of primary liver cancer, currently ranking as one of the highest neoplastic-related mortalities in the world. Due to the difficulty in early diagnosis and lack of effective treatment options, the 5-year survival rate of HCC remains extremely low. Histone deacetylation is one of the most important epigenetic mechanisms, regulating cellular events such as differentiation, proliferation and cell cycle. Histone deacetylases (HDACs), the chief mediators of this epigenetic mechanism, are often aberrantly expressed in various tumours including HCC. Areas covered: This review focuses on the most up-to-date findings of HDACs and their associated molecular mechanisms in HCC onset and progression. In addition, a potential network between HDACs and non-coding RNAs including microRNAs and long noncoding RNAs underlying hepatocarcinogenesis is considered. Expert opinion: Unmasking the role of HDACs and their association with HCC pathogenesis could have implications for future personalized therapeutic and diagnostic targeting.

Preclinical studies reveal that LSD1 inhibition results in tumor growth arrest in lung adenocarcinoma independently of driver mutations

Lung adenocarcinoma (LUAD) is the most prevalent subtype of non-small cell lung cancer. Despite the development of novel targeted and immune therapies, the 5-year survival rate is still only 21%, indicating the need for more efficient treatment regimens. Lysine-specific demethylase 1 (LSD1) is an epigenetic eraser that modifies histone 3 methylation status, and is highly overexpressed in LUAD. Using representative human cell culture systems and two autochthonous transgenic mouse models, we investigated inhibition of LSD1 as a novel therapeutic option for treating LUAD. The reversible LSD1 inhibitor HCI-2509 significantly reduced cell growth with an IC₅₀ of 0.3-5 μmin vitro, which was linked to an enhancement of histone 3 lysine methylation. Most importantly, growth arrest, as well as inhibition of the invasion capacities, was independent of the underlying driver mutations. Subsequent expression profiling revealed that the cell cycle and replication machinery were prominently affected after LSD1 inhibition. In addition, our data provide evidence that LSD1 blockade significantly interferes with EGFR downstream signaling. Finally, our in vitro results were confirmed by preclinical therapeutic approaches, including the use of two autochthonous transgenic LUAD mouse models driven by either EGFR or KRAS mutations. Importantly, LSD1 inhibition resulted in significantly lower tumor formation and a strong reduction in tumor progression, which were independent of the underlying mutational background of the mouse models. Hence, our findings provide substantial evidence indicating that tumor growth of LUAD can be markedly decreased by HCI-2509 treatment, suggesting its use as a single agent maintenance therapy or combined therapeutical application in novel concerted drug approaches.

Induction of Thioredoxin-Interacting Protein by a Histone Deacetylase Inhibitor, Entinostat, Is Associated with DNA Damage and Apoptosis in Esophageal Adenocarcinoma

In 2017, an estimated 17,000 individuals were diagnosed with esophageal adenocarcinoma (EAC), and less than 20% will survive 5 years. Positron emission tomography avidity is indicative of high glucose utilization and is nearly universal in EAC. TXNIP blocks glucose uptake and exhibits proapoptotic functions. Higher expression in EAC has been associated with improved disease-specific survival, lack of lymph node involvement, reduced perineural invasion, and increased tumor differentiation. We hypothesized that TXNIP may act as a tumor suppressor that sensitizes EAC cells to standard chemotherapeutics. EAC cell lines and a Barrett epithelial cell line were used. qRT-PCR, immunoblot, and immunofluorescence techniques evaluated gene expression. TXNIP was stably overexpressed or knocked down using lentiviral RNA transduction techniques. Murine xenograft methods examined growth following overexpression of TXNIP. Apoptosis and DNA damage were measured by annexin V and γH2AX assays. Activation of the intrinsic apoptosis was quantitated with green fluorescence protein-caspase 3 reporter assay. In cultured cells and an esophageal tissue array, TXNIP expression was higher in Barrett epithelia and normal tissue compared with EAC. Constitutive overexpression of TXNIP decreased proliferation, clonogenicity, and tumor xenograft growth. TXNIP overexpression increased, whereas knockdown abrogated, DNA damage and apoptosis following cisplatin treatment. An HDAC inhibitor, entinostat (currently in clinical trials), upregulated TXNIP and synergistically increased cisplatin-mediated DNA damage and apoptosis. TXNIP is a tumor suppressor that is downregulated in EACC. Its reexpression dramatically sensitizes these cells to cisplatin. Our findings support phase I/II evaluation of "priming" strategies to enhance the efficacy of conventional chemotherapeutics in EAC. Mol Cancer Ther; 17(9); 2013-23. ©2018 AACR.

Epigenetic agents in combined anticancer therapy

In the last decade, epigenetic drugs (such as inhibitors of DNA methyltransferases and histone deacetylases) have been intensively used for cancer treatment. Their applications have shown high anticancer effectivity and tolerable side effects. However, they are unfortunately not effective in the treatment of some types and phenotypes of cancers. Nevertheless, several studies have demonstrated that problems of drug efficacy can be overcome through the combined application of therapeutic modulates. Therefore, combined applications of epigenetic agents with chemotherapy, radiation therapy, immunotherapy, oncolytic virotherapy and hyperthermia have been presented. This review summarizes and discusses the general principles of this approach, as introduced and supported by numerous examples. In addition, predictions of the future potential applications of this methodology are included.

MicroRNA-mediated epigenetic targeting of Survivin significantly enhances the antitumor activity of paclitaxel against non-small cell lung cancer

Elevated expression of Survivin correlates with poor prognosis, tumor recurrence, and drug resistance in various human cancers, including non-small cell lung cancer (NSCLC). The underlying mechanism of Survivin upregulation in cancer cells remains elusive. To date, no Survivin-targeted therapy has been approved for cancer treatment. Here, we explored the molecular basis resulting in Survivin overexpression in NSCLC and investigated the antitumor activity of the class I HDAC inhibitor entinostat in combination with paclitaxel. Our data showed that entinostat significantly enhanced paclitaxel-mediated anti-proliferative/anti-survival effects on NSCLC cells in vitro and in vivo. Mechanistically, entinostat selectively decreased expression of Survivin via induction of miR-203 (in vitro and in vivo) and miR-542-3p (in vitro). Moreover, analysis of NSCLC patient samples revealed that the expression levels of miR-203 were downregulated due to promoter hypermethylation in 45% of NSCLC tumors. In contrast, increased expression of both DNA methytransferase I (DNMT1) and Survivin was observed and significantly correlated with the reduced miR-203 in NSCLC. Collectively, these data shed new lights on the molecular mechanism of Survivin upregulation in NSCLC. Our findings also support that the combinatorial treatments of entinostat and paclitaxel will likely exhibit survival benefit in the NSCLC patients with overexpression of DNMT1 and/or Survivin. The DNMT1-miR-203-Survivin signaling axis may provide a new avenue for the development of novel epigenetic approaches to enhance the chemotherapeutic efficacy against NSCLC.

Entinostat: a promising treatment option for patients with advanced breast cancer

Entinostat is a synthetic benzamide derivative histone deacetylase (HDAC) inhibitor, which potently and selectively inhibits class I and IV HDAC enzymes. This action promotes histone hyperacetylation and transcriptional activation of specific genes, with subsequent inhibition of cell proliferation, terminal differentiation and apoptosis. This oral HDAC inhibitor has been evaluated in Phase I and II trials in patients with advanced malignancies, and is in general well tolerated. Entinostat does not currently have regulatory approval for clinical use; however promising preclinical and clinical data exist in hormone-resistant breast cancer. An ECOG-ACRIN Phase III registration study is ongoing in advanced breast cancer (E2112, NCT02115282) and aims to confirm the overall survival advantage observed with the combination of exemestane and entinostat/placebo in the Phase II setting (ENCORE301 trial). This article provides an overview of the chemistry, pharmacokinetics/pharmacodynamics and available clinical data for entinostat with a focus on advanced breast cancer.

Epigenetic therapy approaches in non-small cell lung cancer: Update and perspectives

Non-small cell lung cancer (NSCLC) still constitutes the most common cancer-related cause of death worldwide. All efforts to introduce suitable treatment options using chemotherapeutics or targeted therapies have, up to this point, failed to exhibit a substantial effect on the 5-year-survival rate. The involvement of epigenetic alterations in the evolution of different cancers has led to the development of epigenetics-based therapies, mainly targeting DNA methyltransferases (DNMTs) and histone-modifying enzymes. So far, their greatest success stories have been registered in hematologic neoplasias. As the effects of epigenetic single agent treatment of solid tumors have been limited, the investigative focus now lies on combination therapies of epigenetically active agents with conventional chemotherapy, immunotherapy, or kinase inhibitors. This review includes a short overview of the most important preclinical approaches as well as an extensive discussion of clinical trials using epigenetic combination therapies in NSCLC, including ongoing trials. Thus, we are providing an overview of what lies ahead in the field of epigenetic combinatory therapies of NSCLC in the coming years.

SFRP1 is a possible candidate for epigenetic therapy in non-small cell lung cancer

Background

Non-small cell lung cancer (NSCLC) remains a lethal disease despite many proposed treatments. Recent studies have indicated that epigenetic therapy, which targets epigenetic effects, might be a new therapeutic methodology for NSCLC. However, it is not clear which objects (e.g., genes) this treatment specifically targets. Secreted frizzled-related proteins (SFRPs) are promising candidates for epigenetic therapy in many cancers, but there have been no reports of SFRPs targeted by epigenetic therapy for NSCLC.

Methods

This study performed a meta-analysis of reprogrammed NSCLC cell lines instead of the direct examination of epigenetic therapy treatment to identify epigenetic therapy targets. In addition, mRNA expression/promoter methylation profiles were processed by recently proposed principal component analysis based unsupervised feature extraction and categorical regression analysis based feature extraction.

Results

The Wnt/β-catenin signalling pathway was extensively enriched among 32 genes identified by feature extraction. Among the genes identified, SFRP1 was specifically indicated to target β-catenin, and thus might be targeted by epigenetic therapy in NSCLC cell lines. A histone deacetylase inhibitor might reactivate SFRP1 based upon the re-analysis of a public domain data set. Numerical computation validated the binding of SFRP1 to WNT1 to suppress Wnt signalling pathway activation in NSCLC.

Conclusions

The meta-analysis of reprogrammed NSCLC cell lines identified SFRP1 as a promising target of epigenetic therapy for NSCLC.

Electronic supplementary material

The online version of this article (doi:10.1186/s12920-016-0196-3) contains supplementary material, which is available to authorized users.

Epigenetics: A primer for clinicians

With recent advances in cellular biology, we now appreciate that modifications to DNA and histones can have a profound impact on transcription and function, even in the absence of changes to DNA sequence. These modifications, now commonly referred to as "epigenetic" alterations, have changed how we understand cell behavior, reprogramming and differentiation and have provided significant insight into the mechanisms underlying carcinogenesis. Epigenetic alterations, to this point, are largely identified by changes in DNA methylation and hydroxymethylation as well as methylation, acetylation, and phosphorylation of histone tails. These modifications enable significant flexibility in gene expression, rather than just turning genes "ON" or "OFF." Herein we describe the epigenetic landscape in the regulation of gene expression with a particular focus on interrogating DNA methylation in myeloid malignancy.

Epigenetics in Personalized Management of Lung Cancer

In last several years, the focus on the origin and progression of human cancers has shifted from genetic to epigenetic regulation, with particular attention to methylation and acetylation events that have profound effect on the eventual expression of oncogenes and the suppression of tumor suppressors. A few drugs targeting these epigenetic changes have already been approved for treatment, albeit not for lung cancer. With the recent advances in the push towards personalized therapy, questions have been asked about the possible targeting of epigenetic events for personalized lung cancer therapy. Some progress has been made but a lot needs to be done. In this chapter, a succinct review of these topics is provided.

Inhibitors of DNA Methylation, Histone Deacetylation, and Histone Demethylation: A Perfect Combination for Cancer Therapy

Epigenetic silencing and inappropriate activation of gene expression are frequent events during the initiation and progression of cancer. These events involve a complex interplay between the hypermethylation of CpG dinucleotides within gene promoter and enhancer regions, the recruitment of transcriptional corepressors and the deacetylation and/or methylation of histone tails. These epigenetic regulators act in concert to block transcription or interfere with the maintenance of chromatin boundary regions. However, DNA/histone methylation and histone acetylation states are reversible, enzyme-mediated processes and as such, have emerged as promising targets for cancer therapy. This review will focus on the potential benefits and synergistic/additive effects of combining DNA-demethylating agents and histone deacetylase inhibitors or lysine-specific demethylase inhibitors together in epigenetic therapy for solid tumors and will highlight what is known regarding the mechanisms of action that contribute to the antitumor response.