Transposable elements (TEs) comprise nearly half of the human genome and play an essential role in the maintenance of genomic stability, chromosomal architecture, and transcriptional regulation. TEs are repetitive sequences consisting of RNA transposons, DNA transposons, and endogenous retroviruses that can invade the human genome with a substantial contribution in human evolution and genomic diversity. TEs are therefore firmly regulated from early embryonic development and during the entire course of human life by epigenetic mechanisms, in particular DNA methylation and histone modifications. The deregulation of TEs has been reported in some developmental diseases, as well as for different types of human cancers. To date, the role of TEs, the mechanisms underlying TE reactivation, and the interplay with DNA methylation in human cancers remain largely unexplained. We reviewed the loss of epigenetic regulation and subsequent genomic instability, chromosomal aberrations, transcriptional deregulation, oncogenic activation, and aberrations of non-coding RNAs as the potential mechanisms underlying TE deregulation in human cancers.

Deregulation of imprinted genes is an important molecular mechanism contributing to the development of cancer in humans. However, knowledge about imprinting defects in human hepatocellular carcinoma (HCC), the third leading cause of cancer mortality worldwide, is still limited. Therefore, a systematic meta-analysis of the expression of 223 imprinted loci in human HCC was initiated. This screen revealed that the DLK1-MEG3 locus is frequently deregulated in HCC. Deregulation of DLK1 and MEG3 expression accompanied by extensive aberrations in DNA methylation could be confirmed experimentally in an independent series of human HCC (n = 40) in more than 80% of cases. Loss of methylation at the DLK1-MEG3 locus correlates linearly with global loss of DNA methylation in HCC (r2 = 0.63, p<0.0001). Inhibition of DNMT1 in HCC cells using siRNA led to a reduction in MEG3-DMR methylation and concomitant increase in MEG3 RNA expression. Allele-specific expression analysis identified loss of imprinting in 10 out of 31 informative samples (32%), rendering it one of the most frequent molecular defects in human HCC. In 2 cases unequivocal gain of bi-allelic expression accompanied by substantial loss of methylation at the IG-DMR could be demonstrated. In 8 cases the tumour cells displayed allelic switching by mono-allelic expression of the normally imprinted allele. Allelic switching was accompanied by gains or losses of DNA methylation primarily at IG-DMR1. Analysis of 10 hepatocellular adenomas (HCA) and 5 cases of focal nodular hyperplasia (FNH) confirmed that this epigenetic instability is specifically associated with the process of malignant transformation and not linked to increased proliferation per se. This widespread imprint instability in human HCC has to be considered in order to minimize unwanted side-effects of therapeutic approaches targeting the DNA methylation machinery. It might also serve in the future as predictive biomarker and for monitoring response to epigenetic therapy.

BackgroundCancer screening awareness and participation may be lower in low- and middle-income countries that lack established national screening programmes compared with those that do. We evaluated potential determinants of awareness about and participation in breast and cervical cancer screening, and breast self-examination (BSE) in women using survey data from Indonesia.MethodsFrom the fifth Indonesian Family Life Survey (2014–2015), a total of 5397 women aged 40 and older without any history of cancer who responded to questionnaires concerning Pap smears, mammography, and BSE were included. Multilevel modelling was used to assess potential determinants in relation to awareness about Pap smears and mammography, and participation in Pap smears and BSE practice. Multivariable analyses were performed to identify independent predictors of cancer screening.ResultsOf the 5397 respondents, 1058 (20%) women were aware of Pap smears, of which 297 had never had the procedure. Only 251 (5%) participants were aware of mammography. A total of 605 (12%) of women reported they performed BSE. Higher education and household expenditure were consistently associated with higher odds of awareness about Pap smears and mammography (e.g. odds ratio [OR] of being aware of Pap smear and mammography: 7.82 (95% CI: 6.30–9.70) and 7.70 (6.19–9.58), respectively, for high school graduates compared to women with less educational attainment in the multivariable models), and participation in Pap smears and BSE. We also identified enabling factors linked with greater cancer screening awareness and participation, including health insurance, shorter distance to health services, and social participation.ConclusionThere are socioeconomic disparities in cancer screening awareness and participation among Indonesian women. Our findings may help inform targeted health promotion and screening for cancer in the presence of limited resources.Electronic supplementary materialThe online version of this article (10.1186/s12885-018-4125-z) contains supplementary material, which is available to authorized users.

BackgroundThe newly released 450k DNA methylation array from Illumina, Inc. offers the possibility to analyze more than 480,000 individual CpG sites in a user friendly standardized format. In this study the relationship between the β-values provided by the Illumina, Inc. array for each individual CpG dinucleotide and the quantitative methylation levels obtained by pyrosequencing were analyzed. In addition, the representation of microRNA genes and imprinted loci on the Illumina, Inc. array was assessed in detail. Genomic DNA from 4 human breast cancer cell lines (IPH-926, HCC1937, MDA-MB-134, PMC42) and 18 human breast cancer specimens as well as 4 normal mammary epithelial fractions was analyzed on 450k DNA methylation arrays. The β-values for 692 individual CpG sites from 62 different genes were cross-validated using conventional quantitative pyrosequencing.FindingsThe newly released 450k methylation array from Illumina, Inc. shows a high concordance with quantitative pyrosequencing if identical CpG sites are analyzed in cell lines (Spearman r = 0.88, p ≪ 0.0001), which is somewhat reduced in primary tumor specimens (Spearman r = 0.86, p ≪ 0.0001). 80.7% of the CpG sites show an absolute difference in methylation level of less than 15 percentage points. If different CpG sites in the same CpG islands are targeted the concordance is lower (r = 0.83 in cell lines and r = 0.7 in primary tumors). The number of CpG sites representing microRNA genes and imprinted loci is very heterogeneous (range: 1 – 70 CpG sites for microRNAs and 1 – 288 for imprinted loci).ConclusionsThe newly released 450k methylation array from Illumina, Inc. provides a genome-wide quantitative representation of DNA methylation aberrations in a convenient format. Overall, the congruence with pyrosequencing data is very good. However, for individual loci one should be careful to translate the β-values directly into percent methylation levels.

Epigenetic alterations have been identified as a major characteristic in human cancers. Advances in the field of epigenetics have contributed significantly in refining our knowledge of molecular mechanisms underlying malignant transformation. DNA methylation and microRNA expression are epigenetic mechanisms that are widely altered in human cancers including hepatocellular carcinoma (HCC), the third leading cause of cancer related mortality worldwide. Both DNA methylation and microRNA expression patterns are regulated in developmental stage specific-, cell type specific- and tissue-specific manner. The aberrations are inferred in the maintenance of cancer stem cells and in clonal cell evolution during carcinogenesis. The availability of genome-wide technologies for DNA methylation and microRNA profiling has revolutionized the field of epigenetics and led to the discovery of a number of epigenetically silenced microRNAs in cancerous cells and primary tissues. Dysregulation of these microRNAs affects several key signalling pathways in hepatocarcinogenesis suggesting that modulation of DNA methylation and/or microRNA expression can serve as new therapeutic targets for HCC. Accumulative evidence shows that aberrant DNA methylation of certain microRNA genes is an event specifically found in HCC which correlates with unfavorable outcomes. Therefore, it can potentially serve as a biomarker for detection as well as for prognosis, monitoring and predicting therapeutic responses in HCC.

Epigenetic inactivation by aberrant DNA methylation has been reported for many microRNA genes in various human malignancies. However, relatively little is known about microRNA gene methylation in hepatocellular carcinoma (HCC). Therefore, a systematic screen for identification of aberrantly hypermethylated microRNA genes in HCC was initiated. The methylation status of 39 intergenic CpG island associated microRNA genes was analyzed in HCC cell lines (n 5 7), immortalized hepatocytes (n 5 2) and normal liver samples (n 5 5). Subsequently, 13 differentially methylated microRNA genes were analyzed in primary human HCC samples (n 5 40), benign liver tumors (n 5 15) and the adjacent liver tissues employing pyrosequencing. Expression of microRNA genes was measured using quantitative real-time polymerase chain reaction (RT-PCR). In addition, DNA methylation and expression of microRNA genes were measured after DNMT1 knockdown or DNMT inhibition. Aberrant hypermethylation and concomitant reduction in expression of intergenic microRNA genes is a frequent event in human HCC: hsamir-9-2 (23%), hsa-mir-9-3 (50 %), hsa-mir-124-1 (20%), hsa-mir-124-2 (13%), hsa-mir-124-3 (43%), hsa-mir-129-2 (58%), hsa-mir-596 (28%) and hsa-mir-1247 (38%). Altogether, it affects 90% of the HCC specimens under study. MicroRNA gene methylation is not found in hepatocellular adenoma (n 5 10) and focal nodular hyperplasia (n 5 5). DNMT1 knockdown or DNMT inhibition reduced microRNA gene methylation and stimulated expression. In primary human HCC specimens hypermethylation and expression of microRNA genes showed an inverse correlation. Concordant hypermethylation of three or more microRNA genes is a highly specific marker for the detection of HCC and for poor prognosis.

The discovery of small non-coding RNAs known as microRNAs has refined our view of the complexity of gene expression regulation. In hepatocellular carcinoma (HCC), the fifth most frequent cancer and the third leading cause of cancer death worldwide, dysregulation of microRNAs has been implicated in all aspects of hepatocarcinogenesis. In addition, alterations of microRNA expression have also been reported in non-cancerous liver diseases including chronic hepatitis and liver cirrhosis. MicroRNAs have been proposed as clinically useful diagnostic biomarkers to differentiate HCC from different liver pathologies and healthy controls. Unique patterns of microRNA expression have also been implicated as biomarkers for prognosis as well as to predict and monitor therapeutic responses in HCC. Since dysregulation has been detected in various specimens including primary liver cancer tissues, serum, plasma, and urine, microRNAs represent novel non-invasive markers for HCC screening and predicting therapeutic responses. However, despite a significant number of studies, a consensus on which microRNA panels, sample types, and methodologies for microRNA expression analysis have to be used has not yet been established. This review focuses on potential values, benefits, and limitations of microRNAs as new clinical markers for diagnosis, prognosis, prediction, and therapeutic monitoring in HCC.

Background:Omega-3 is a polyunsaturated fatty acid with an ability to regulate cell proliferation and apoptosis through interaction with inflammatory mediators. The potential additional beneficial effects of Omega-3 on chemotherapy patients with breast cancer is not yet completely revealed.Methods:A double-blind randomized control trial (RCT) involving a total of 48 locally advanced breast cancer patients was conducted. Ki-67 and VEGF expressions, as well as overall survival of patients receiving neoadjuvant cyclophosphamide-doxorubicin-5’fluorouracyl (CAF) chemotherapy plus Omega-3 (intervention group) or placebo (control group), were compared. Kaplan-Meier curve and Cox-regression tests were used to assess conditional disease-free survival (DFS) and overall survival (OS) between the two groups.Results:Decreased Ki-67 expression was observed in the intervention group compared to control (42.4±4.8 versus 39.2±5.3; T-test p=0.032). Decreased Ki-67 expression was observed in intervention compared to control group (42.4±4.8 versus 39.2±5.3; T-test p=0.032). Decreased VEGF expression was also seen in the intervention group compared to control (32.7±5.2 versus 29.5±5.4; T-test p=0.041). VEGF expression positively correlated with Ki-67 expression (Spearman’s test p<0.001, R2=0.541). Overall survival in the intervention group was significantly longer in comparison to the control group (mean survival: 30.9 ± 3.71 versus 25.9 ± 3.6 weeks, Mantel-Cox test p=0.048; HR=0.411, 95%CI: 0.201-0.840). Disease-free survival was significantly longer in the intervention group compared to the control group (mean survival: 28.5 ± 3.3 versus 23.7 ± 3.6, respectively; Mantel-Cox test p=0.044, HR= 0.439, 95%CI: 0.222-0.869).Conclusion:Omega-3 fatty acid supplementation improved overall survival and progression-free survival of locally advanced breast cancer treated with CAF neoadjuvant chemotherapy and mastectomy.