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Drug resistance is the drug-effectiveness reduction in treatment and is a serious problem in oncology and infections. In oncology, drug resistance is a complicated process resulting from enhancing the function of a pump that transports drugs out of tumor cells, or acquiring mutations in drug target. Surprisingly, most drugs are very effective in the early stages, but the response to the drug wears off over time and resistance eventually develops. Drug resistance is caused by genetic and epigenetic changes that affect cancer cells and the tumor environment. The study of inherited changes in the phenotype without changes in the DNA sequence is called epigenetics. Because of reversible changes in epigenetics, they are an attractive target for therapy. Some of these epigenetic drugs are effective in treating cancers like acute myeloid leukemia (AML), which is characterized by the accumulation and proliferation of immature hematopoietic cells in the blood and bone marrow. In this article, we outlined the various contributing factors involved in resistance or sensitivity to epigenetic drugs in the treatment of AML.

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Evidence has emerged implicating epigenetic alterations in inflammatory breast cancer (IBC) origin and progression. IBC is a rare and rapidly progressing disease, considered the most aggressive type of breast cancer (BC). At clinical presentation, IBC is characterized by diffuse erythema, skin ridging, dermal lymphatic invasion, and peau d'orange aspect. The widespread distribution of the tumor as emboli throughout the breast and intra- and intertumor heterogeneity is associated with its poor prognosis. In this review, we highlighted studies documenting the essential roles of epigenetic mechanisms in remodeling chromatin and modulating gene expression during mammary gland differentiation and the development of IBC. Compiling evidence has emerged implicating epigenetic changes as a common denominator linking the main risk factors (socioeconomic status, environmental exposure to endocrine disruptors, racial disparities, and obesity) with IBC development. DNA methylation changes and their impact on the diagnosis, prognosis, and treatment of IBC are also described. Recent studies are focusing on the use of histone deacetylase inhibitors as promising epigenetic drugs for treating IBC. All efforts must be undertaken to unravel the epigenetic marks that drive this disease and how this knowledge could impact strategies to reduce the risk of IBC development and progression.

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Triple-negative breast cancer is an aggressive disease frequently associated with resistance to chemotherapy. Evidence supports that small molecules showing DNA methyltransferase inhibitory activity (DNMTi) are important to sensitize cancer cells to cytotoxic agents, in part, by reverting the acquired epigenetic changes associated with the resistance to therapy. The present study aimed to evaluate if chemical compounds derived from propolis could act as epigenetic drugs (epi-drugs). We selected three phenolic acids (caffeic, dihydrocinnamic, and p-coumaric) commonly detected in propolis and the (-)-epigallocatechin-3-gallate (EGCG) from green tea, which is a well-known DNA demethylating agent, for further analysis. The treatment with p-coumaric acid and EGCG significantly reduced the cell viability of four triple-negative breast cancer cell lines (BT-20, BT-549, MDA-MB-231, and MDA-MB-436). Computational predictions by molecular docking indicated that both chemicals could interact with the MTAse domain of the human DNMT1 and directly compete with its intrinsic inhibitor S-Adenosyl-l-homocysteine (SAH). Although the ethanolic extract of propolis (EEP) did not change the global DNA methylation content, by using MS-PCR (Methylation-Specific Polymerase Chain Reaction) we demonstrated that EEP and EGCG were able to partly demethylate the promoter region of RASSF1A in BT-549 cells. Also, in vitro treatment with EEP altered the RASSF1 protein expression levels. Our data indicated that some chemical compound present in the EEP has DNMTi activity and can revert the epigenetic silencing of the tumor suppressor RASSF1A. These findings suggest that propolis are a promising source for epi-drugs discovery.

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Valproic acid is an antiepileptic drug with more than 50 years of clinical use. In the past decade, its anticancer effects were discovered. Analyses in groups of patients who used this drug for years have shown that it decreases the frequency of head and neck cancer. Recent studies show the anticancer effect of combining valproic acid with chemotherapy, biological therapy and antioxidant systems inhibitors, with exceptional results. In this review, we analyze the metabolism of valproic acid and its application against cancer.

El ácido valproico es un fármaco antiepiléptico con más de 50 años de uso clínico. En la década pasada se descubrieron sus efectos anticancerígenos. El análisis de grupos de pacientes que utilizaron este fármaco durante años ha mostrado que disminuye la frecuencia de cáncer de cabeza y cuello. Estudios recientes evidencian el efecto anticáncer al combinar el ácido valproico con la quimioterapia, terapia biológica e inhibidores de sistemas antioxidantes, con resultados excepcionales. En esta revisión se analiza el metabolismo del ácido valproico y su aplicación contra el cáncer.

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Resumen El ácido valproico es un fármaco antiepiléptico con más de 50 años de uso clínico. En la década pasada se descubrieron sus efectos anticancerígenos. El análisis de grupos de pacientes que utilizaron este fármaco durante años ha mostrado que disminuye la frecuencia de cáncer de cabeza y cuello. Estudios recientes evidencian el efecto anticáncer al combinar el ácido valproico con la quimioterapia, terapia biológica e inhibidores de sistemas antioxidantes, con resultados excepcionales. En esta revisión se analiza el metabolismo del ácido valproico y su aplicación contra el cáncer.

Abstract Valproic acid is an antiepileptic drug with more than 50 years of clinical use. In the past decade, its anticancer effects were discovered. Analyses in groups of patients who used this drug for years have shown that it decreases the frequency of head and neck cancer. Recent studies show the anticancer effect of combining valproic acid with chemotherapy, biological therapy and antioxidant systems inhibitors, with exceptional results. In this review, we analyze the metabolism of valproic acid and its application against cancer.

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The hypomethylating agents azacytidine and decitabine are unaffordable for many patients with MDS. The combination of the DNA methyltransferase inhibitor hydralazine and the histone deacetylase inhibitor valproate has shown preliminary efficacy in MDS. The aim of this study is to evaluate the clinical efficacy and safety of hydralazine/valproate in a case series of MDS patients treated in a compassionate manner. Hydralazine was dosed according to the acetylation genotype of patients (slow acetylators 83 mg daily; fast acetylators 182 mg daily), and valproate was dosed at 30 mg/kg/day. Both drugs were given daily until disease progression. Response and toxicity were evaluated with the International Working Group criteria and CTCAE, version 4, respectively. Survival parameters were estimated with the Kaplan-Meier method. From 2009 to 2012, 14 patients were treated. The median age ± SD was 55.2 ± 19.52 (range 23-87) years. According to the IPSS, cases were graded as intermediate-1 (n = 8/14; 57.2%) or intermediate-2 (n = 6/14; 42.8%). Responses were as follows: five (35.7%) complete response, one (7.1%) partial response, and two (14.28%) became transfusion independent. The mean duration of response ± SD was 60 ± 35.28 months (range 5-94). Three patients progressed to AML. At a median follow-up of 57 months (range 1-106), the median OS was 27 months. At that point, five patients remained on the treatment, one with partial response and four with complete response. The median OS was not reached in the eight patients who saw a clinical benefit from the treatment, in comparison to an OS of 7 months in the six patients who had no treatment. The combination of hydralazine and valproate is safe and effective in MDS, and its further testing is highly desirable.

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Cancer is a complex disease with both genetic and epigenetic origins. The growing field of epigenetics has contributed to our understanding of oncogenesis and tumor progression, and has allowed the development of novel therapeutic drugs. First-generation epigenetic inhibitor drugs have obtained modest clinical results in two types of hematological malignancy. Second-generation epigenetic inhibitors are in development, and have intrinsically greater selectivity for their molecular targets. Solid tumors are more genetic and epigenetically complex than hematological malignancies, but the transcriptome and epigenome biomarkers have been identified for many of these malignancies. This solid tumor molecular aberration profile may be modified using specific or quasi-specific epidrugs together with conventional and innovative anticancer treatments. In this critical review, we briefly analyze the strategies to select the targeted epigenetic changes, enumerate the second-generation epigenetic inhibitors, and describe the main signs indicating the potential of epigenetic therapies in the management of solid tumors. We also highlight the work of consortia or academic organizations that support the undertaking of human epigenetic therapeutic projects as well as some examples of transcriptome/epigenome profile determination in clinical assessment of cancer patients treated with epidrugs. There is a good chance that epigenetic therapies will be able to be used in patients with solid tumors in the future. This may happen soon through collaboration of diverse scientific groups, making the selection of targeted epigenetic aberration(s) more rapid, the design and probe of drug candidates, accelerating in vitro and in vivo assays, and undertaking new cancer epigenetic-therapy clinical trails.

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A epigenética compreende um conjunto de mecanismos que promovem a regulação da expressão gênica a nível transcricional através de modificações químicas no DNA e na cromatina, como metilação, acetilação e fosforilação, que resultam na conseqüente mudança fenotípica do indivíduo sem, no entanto, ocorrer nenhuma alteração na seqüência do DNA. Essas modificações químicas no DNA são constantemente feitas e desfeitas durante toda a vida do indivíduo, exceto para marcações químicas constitutivas que são herdadas geneticamente, visto que freqüentemente os indivíduos entram em contato com agentes promotores desses fenômenos durante a vida. Alterações nos padrões epigenéticos promovendo a expressão aberrante ou o silenciamento de determinados genes podem aparecer em organismos com idade avançada, e em uma ampla variedade de eventos e patologias como no câncer, na inativação do cromossomo X, no imprinting genômico, e em diversas síndromes de ordem neurológica e de prejuízo no desenvolvimento motor. Desse modo, busca-se atualmente o desenvolvimento de drogas que possuem a capacidade de reverter as marcações químicas alteradas em regiões específicas do genoma relacionadas a determinadas doenças. Uma maior compreensão desse universo da epigenética associada com suas implicações aos estados fisiológicos normais e patológicos mostra-se como uma grande promessa nessa era molecular, para o desenvolvimento de ferramentas profiláticas, diagnósticas e terapêuticas de uma ampla variedade de doenças.

Epigenetics includes several mechanisms that promote the gene expression regulation at transcriptional level through chemical changes in DNA and chromatin, such as methylation, acetylation and phosphorylation, resulting in phenotypic change without no changes occur in the DNA sequence. These DNA chemical changes are constantly made and unmade throughout the individual life, except for constitutive chemical markings that are genetically inherited, because often people are in contact with agents that promote these phenomens during their lifes. Changes in epigenetic patterns promoting aberrant expression or gene silencing may appear in aged organisms, and in a wide variety of events and conditions such as cancer, X chromosome inactivation in genomic imprinting, and in various neurological and motor development syndromes. Thus, seek currently drugs development that have the ability to reverse altered chemical markings in specific regions of the genome related to certain diseases. A greater understanding of the epigenetic universe associated with its implications to normal physiological and pathological states, it is a great promise in molecular era to development of prophylactic, diagnostic and therapeutic tools of a wide variety of diseases.

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