Cancer is one of the leading causes of death worldwide and it can affect any part of the organism. It arises as a consequence of the genetic and epigenetic changes that lead to the uncontrolled growth of the cells. The epigenetic machinery can regulate gene expression without altering the DNA sequence, and it comprises methylation of the DNA, histones modifications, and non-coding RNAs. Alterations of these gene-expression regulatory elements can be produced by an imbalance of the intracellular environment, such as the one derived by oxidative stress, to promote cancer development, progression, and resistance to chemotherapeutic treatments. Here we review the current literature on the effect of oxidative stress in the epigenetic machinery, especially over the largely unknown ncRNAs and its consequences toward cancer development and progression.

Background The promoter hypermethylation of the methylguanine-DNA methyltransferase gene is a frequently used biomarker in daily clinical practice as it is associated with a favorable prognosis in glioblastoma patients treated with temozolamide. Due to the absence of adequately standardized techniques, international harmonization of the MGMT methylation biomarker is still an unmet clinical need for the diagnosis and treatment of glioblastoma patients. Results In this study we carried out a clinical validation of a quantitative assay for MGMT methylation detection by comparing a novel quantitative MSP using double-probe (dp_qMSP) with the conventional MSP in 100 FFPE glioblastoma samples. We performed both technologies and established the best cutoff for the identification of positive-methylated samples using the quantitative data obtained from dp_qMSP. Kaplan–Meier curves and ROC time dependent curves were employed for the comparison of both methodologies. Conclusions We obtained similar results using both assays in the same cohort of patients, in terms of progression free survival and overall survival according to Kaplan–Meier curves. In addition, the results of ROC(t) curves showed that dp_qMSP increases the area under curve time-dependent in comparison with MSP for predicting progression free survival and overall survival over time. We concluded that dp_qMSP is an alternative methodology compatible with the results obtained with the conventional MSP. Our assay will improve the therapeutic management of glioblastoma patients, being a more sensitive and competitive alternative methodology that ensures the standardization of the MGMT-biomarker making it reliable and suitable for clinical use.

No abstract

No abstract

One of the major limitations associated with platinum use is the resistance that almost invariably develops in different tumor types. In the current study, we sought to identify epigenetically regulated microRNAs as novel biomarkers of platinum resistance in lung and ovarian cancers, the ones with highest ratios of associated chemo-resistance. Experimental procedures: We combined transcriptomic data from microRNA and mRNA under the influence of an epigenetic reactivation treatment in a panel of four paired cisplatin -sensitive and -resistant cell lines, followed by real-time expression and epigenetic validations for accurate candidate selection in 19 human cancer cell lines. To identify specific candidate genes under miRNA regulation, we assembled “in silico” miRNAs and mRNAs sequences by using ten different algorithms followed by qRT-PCR validation. Functional assays of site-directed mutagenesis and luciferase activity, miRNAs precursor overexpression, silencing by antago-miR and cell viability were performed to confirm their specificity in gene regulation. Results were further explored in 187 primary samples obtained from ovarian tumors and controls. Results: We identified 4 candidates, miR-7, miR-132, miR-335 and miR-148a, which deregulation seems to be a common event in the development of resistance to cisplatin in both tumor types. miR-7 presented specific methylation in resistant cell lines, and was associated with poorer prognosis in ovarian cancer patients. Our experimental results strongly support the direct regulation of MAFG through miR-7 and their involvement in the development of CDDP resistance in human tumor cells. Conclusion: The basal methylation status of miR-7 before treatment may be a potential clinical epigenetic biomarker, predictor of the chemotherapy outcome to CDDP in ovarian cancer patients. To the best of our knowledge, this is the first report linking the regulation of MAFG by miRNA-7 and its role in chemotherapy response to CDDP. Furthermore, this data highlights the possible role of MAFG as a novel therapeutic target for platinum resistant tumors. Citation Format: Olga Vera, Julia Jimenez, Carlos Rodriguez-Antolin, Olga Pernia, Carmen Rodriguez, Javier Soto, Rocio Rosas, Isabel Esteban-Rodriguez, Rosario Perona, Javier de Castro, Inmaculada Ibáñez-de-Cáceres. DNA methylation of miR-7 is a mechanism involved in platinum response through MAFG overexpression in cancer cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 4413.

Purpose: Many cancers initially respond to Cisplatin-based chemotherapy; however, resistance frequently develops. We have recently reported that reduction of IGFBP-3 expression by promoter methylation is involved in the CDDP acquired resistance process in 3 matched CDDP sensitive/resistant human cancer cell lines and in a human cohort of 36 in non-small cell lung cancer (NSCLC) patients, probably because CDDP also induces DNA methylation de novo. The purpose of the present study is to investigate the role of IGFBP-3 in the PI3K signaling pathway alterations to design a translational based-profile to predict resistance in NSCLC. The biological significance of IGFBP-3 is of great importance in controlling cell growth, transformation and survival; as IGF-I binds to IGFBP-3 with stronger affinity than to its own receptor (IGFIR), blocking their interaction and abolishing the mitogenic and antiapoptotic actions. IGF-I is also able to activate EGF receptor. Those tyrosine kinases receptors (IGFIR and EGFR), signal through the PI3K/Akt pathway, that plays a crucial role in cell growth, proliferation, and survival and is commonly upregulated during tumorigenesis, including NSCLC; although the precise mechanism is not well defined. Patients and methods: In the present study we have examined the relationship between first, IGFBP-3 gene expression regulated by promoter methylation measured by RT-PCR, bisulfite sequencing and methylation specific PCR and second the activation of the EGFR, IGFIR and PI3K/AKT pathways through the analysis of the PTEN, AKT, pAKT, pEGFR, EGFR, pIGFIR and IGFIR protein levels by Western-Blot, immunofluorescence and immunohistochemical analysis in 10 human cancer cell lines and in 25 NSCLC patients with known IGFBP-3 methylation status and response to CDDP. Additionally, in order to provide a helpful tool that enables clinicians to identify or to exclude patients with a potential response to cisplatin, we have used the Fisher's exact test within a 2x2 contingence table to calculate the association between our diagnostic test and the true outcome of analyzed samples in terms of cisplatin IC50. Results: Our results suggest that loss of IGFBP-3 expression by promoter methylation in tumor cells treated with CDDP may activate the PI3K/AKT pathway through the specific derepression of IGFIR signaling, inducing resistance to CDDP. This study also provides a predictive test for clinical practice with an accuracy and precision of 0.84 and 0.9, respectively, (P=0.0062). Conclusion: We present a biomarker-test that could provide clinicians with a robust tool with which to decide on the use of cisplatin, improving patient clinical outcomes. Supported by FIS project number: PS09/00472 and a Miguel Servet financial grant to Ibanez de Caceres, I (CP08/000689; PI-717). Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 1726. doi:1538-7445.AM2012-1726