RESUMO
Lung cancer patients are diagnosed at late stages when curative treatments are no longer possible; thus, molecular biomarkers for noninvasive detection are urgently needed. In this sense, we previously identified and validated an epigenetic 4-gene signature that yielded a high diagnostic performance in tissue and invasive pulmonary fluids. We analyzed DNA methylation levels using the ultrasensitive digital droplet PCR in noninvasive samples in a cohort of 83 patients. We demonstrated that BCAT1 is the candidate that achieves high diagnostic efficacy in circulating DNA derived from plasma (area under the curve: 0.85). Impact of potentially confounding variables was also explored.
Assuntos
Ácidos Nucleicos Livres , Neoplasias Pulmonares , Biomarcadores Tumorais/genética , Ácidos Nucleicos Livres/genética , DNA , Metilação de DNA , Epigênese Genética , Humanos , Neoplasias Pulmonares/diagnóstico , Neoplasias Pulmonares/genética , Transaminases/genéticaRESUMO
Early alterations in cancer include the deregulation of epigenetic events such as changes in DNA methylation and abnormal levels of non-coding (nc)RNAs. Although these changes can be identified in tumors, alternative sources of samples may offer advantages over tissue biopsies. Because tumors shed DNA, RNA, and proteins, biological fluids containing these molecules can accurately reflect alterations found in cancer cells, not only coming from the primary tumor, but also from metastasis and from the tumor microenvironment (TME). Depending on the type of cancer, biological fluids encompass blood, urine, cerebrospinal fluid, and saliva, among others. Such samples are named with the general term "liquid biopsy" (LB). With the advent of ultrasensitive technologies during the last decade, the identification of actionable genetic alterations (i.e., mutations) in LB is a common practice to decide whether or not targeted therapy should be applied. Likewise, the analysis of global or specific epigenetic alterations may also be important as biomarkers for diagnosis, prognosis, and even for cancer drug response. Several commercial kits that assess the DNA promoter methylation of single genes or gene sets are available, with some of them being tested as biomarkers for diagnosis in clinical trials. From the tumors with highest incidence, we can stress the relevance of DNA methylation changes in the following genes found in LB: SHOX2 (for lung cancer); RASSF1A, RARB2, and GSTP1 (for lung, breast, genitourinary and colon cancers); and SEPT9 (for colon cancer). Moreover, multi-cancer high-throughput methylation-based tests are now commercially available. Increased levels of the microRNA miR21 and several miRNA- and long ncRNA-signatures can also be indicative biomarkers in LB. Therefore, epigenetic biomarkers are attractive and may have a clinical value in cancer. Nonetheless, validation, standardization, and demonstration of an added value over the common clinical practice are issues needed to be addressed in the transfer of this knowledge from "bench to bedside".
RESUMO
Cancer is a complex disease involving alterations of multiple processes, with both genetic and epigenetic features contributing as core factors to the disease. In recent years, it has become evident that non-coding RNAs (ncRNAs), an epigenetic factor, play a key role in the initiation and progression of cancer. MicroRNAs, the most studied non-coding RNAs subtype, are key controllers in a myriad of cellular processes, including proliferation, differentiation, and apoptosis. Furthermore, the expression of miRNAs is controlled, concomitantly, by other epigenetic factors, such as DNA methylation and histone modifications, resulting in aberrant patterns of expression upon the occurrence of cancer. In this sense, aberrant miRNA landscape evaluation has emerged as a promising strategy for cancer management. In this review, we have focused on the regulation (biogenesis, processing, and dysregulation) of miRNAs and their role as modulators of the epigenetic machinery. We have also highlighted their potential clinical value, such as validated diagnostic and prognostic biomarkers, and their relevant role as chromatin modifiers in cancer therapy.
Assuntos
Epigênese Genética , MicroRNAs/genética , Neoplasias/genética , RNA Neoplásico/genética , Pesquisa Translacional Biomédica , Biomarcadores Tumorais , Neoplasias da Mama/genética , Metilação de DNA , DNA de Neoplasias/genética , Feminino , Regulação Neoplásica da Expressão Gênica , Terapia Genética , Código das Histonas , Humanos , Neoplasias Pulmonares/genética , MicroRNAs/biossíntese , Proteínas de Neoplasias/genética , Proteínas de Neoplasias/metabolismo , Neoplasias/metabolismo , Neoplasias/terapia , Neoplasias Ovarianas/genética , Prognóstico , Processamento Pós-Transcricional do RNA , RNA Neoplásico/biossíntese , Neoplasias Gástricas/genéticaRESUMO
Methylation of CpG dinucleotides plays a crucial role in the regulation of gene expression and therefore in the development of different pathologies. Aberrant methylation has been associated to the majority of the diseases, including cancer, neurodegenerative, cardiovascular and autoimmune disorders. Analysis of DNA methylation patterns is crucial to understand the underlying molecular mechanism of these diseases. Moreover, DNA methylation patterns could be used as biomarker for clinical management, such as diagnosis, prognosis and treatment response. Nowadays, a variety of high throughput methods for DNA methylation have been developed to analyze the methylation status of a high number of CpGs at once or even the whole genome. However, identification of specific methylation patterns at specific loci is essential for validation and also as a tool for diagnosis. In this review, we describe the most commonly used approaches to evaluate specific DNA methylation. There are three main groups of techniques that allow the identification of specific regions that are differentially methylated: bisulfite conversion-based methods, restriction enzyme-based approaches, and affinity enrichment-based assays. In the first group, specific restriction enzymes recognize and cleave unmethylated DNA, leaving methylated sequences intact. Bisulfite conversion methods are the most popular approach to distinguish methylated and unmethylated DNA. Unmethylated cytosines are deaminated to uracil by sodium bisulfite treatment, while the methyl cytosines remain unconverted. In the last group, proteins with methylation binding domains or antibodies against methyl cytosines are used to recognize methylated DNA. In this review, we provide the theoretical basis and the framework of each technique as well as the analysis of their strength and the weaknesses.
Assuntos
Metilação de DNA , Epigênese Genética , Epigenômica/métodos , Envelhecimento/genética , Ilhas de CpG/genética , Neoplasias/genética , Obesidade/genética , Reação em Cadeia da Polimerase/métodos , Análise de Sequência de DNA/métodosRESUMO
Aging is a multifactorial process characterized by the progressive loss of physiological functions, leading to an increased vulnerability to age-associated diseases and finally to death. Several theories have been proposed to explain the nature of aging. One of the most known identifies the free radicals produced by the mitochondrial metabolism as the cause of cellular and DNA damage. However, there are also several evidences supporting that epigenetic modifications, such as DNA methylation, noncoding RNAs, and histone modifications, play a critical role in the molecular mechanism of aging. In this review, we explore the significance of these findings and argue how the interlinked effects of oxidative stress and epigenetics can explain the cause of age-related declines.
