Gastroesophageal junction adenocarcinoma displays abnormalities in homologous recombination and nucleotide excision repair

Sustained inactivation of the Polycomb PRC1 complex induces DNA repair defects and genomic instability in epigenetic tumors

Cancer initiation and progression are typically associated with the accumulation of driver mutations and genomic instability. However, recent studies demonstrated that cancers can also be purely initiated by epigenetic alterations, without driver mutations. Specifically, a 24-hours transient down-regulation of polyhomeotic (ph-KD), a core component of the Polycomb complex PRC1, is sufficient to drive epigenetically initiated cancers (EICs) in Drosophila, which are proficient in DNA repair and are characterized by a stable genome. Whether genomic instability eventually occurs when PRC1 down-regulation is performed for extended periods of time remains unclear. Here we show that prolonged depletion of a PRC1 component, which mimics cancer initiating events, results in broad dysregulation of DNA replication and repair genes, along with the accumulation of DNA breaks, defective repair, and widespread genomic instability in the cancer tissue. A broad mis-regulation of H2AK118 ubiquitylation and to a lesser extent of H3K27 trimethylation also occurs, and might contribute to these phenotypes. Together, this study supports a model where DNA repair and replication defects amplify the tumorigenic transformation epigenetically induced by PRC1 loss, resulting in genomic instability and cancer progression.

Therapeutic Potential of PARP Inhibitors in the Treatment of Gastrointestinal Cancers

Gastrointestinal (GI) malignancies are a major global health burden, with high mortality rates. The identification of novel therapeutic strategies is crucial to improve treatment and survival of patients. The poly (ADP-ribose) polymerase (PARP) enzymes involved in the DNA damage response (DDR) play major roles in the development, progression and treatment response of cancer, with PARP inhibitors (PARPi) currently used in the clinic for breast, ovarian, fallopian, primary peritoneal, pancreatic and prostate cancers with deficiencies in homologous recombination (HR) DNA repair. This article examines the current evidence for the role of the DDR PARP enzymes (PARP1, 2, 3 and 4) in the development, progression and treatment response of GI cancers. Furthermore, we discuss the role of HR status as a predictive biomarker of PARPi efficacy in GI cancer patients and examine the pre-clinical and clinical evidence for PARPi and cytotoxic therapy combination strategies in GI cancer. We also include an analysis of the genomic and transcriptomic landscape of the DDR PARP genes and key HR genes (BRCA1, BRCA2, ATM, RAD51, MRE11, PALB2) in GI patient tumours (n = 1744) using publicly available datasets to identify patients that may benefit from PARPi therapeutic approaches.

LncRNA BCYRN1/miR-490-3p/POU3F2, served as a ceRNA network, is connected with worse survival rate of hepatocellular carcinoma patients and promotes tumor cell growth and metastasis

Backgrounds

LncRNA Brain Cytoplasmic RNA 1 (BCYRN1) has been certified to modulate cancer cells growth and aggressiveness in several tumors. However, research about function of BCYRN1 in hepatocellular carcinoma (HCC) is limited. Therefore, our research intends to explore the function of BCYRN1 in HCC.

Methods

HepG2 and BEL-7402 cell lines were employed for later function experiments. Differently expression levels of BCYRN1, miR-490-3p, and POU class 3 homeobox 2 (POU3F2) were determined on the base of TCGA dataset including 375 HCC patients and 50 normal. 370 cases of patients, which have fairly complete clinical data, were utilized for survival analysis of BCYRN1, miR-490-3p, or POU3F2 by Kaplan–Meier method. Relative expression pattern of BCYRN1 was examined by quantitative real time polymerase chain reaction (qRT-PCR), and relative expression level of POU3F2 was assessed by qRT-PCR and western blot. Cell biological behaviors were analyzed by cell counting kit-8, cloning formation, and transwell assays. Bioinformatics software and dual luciferase assay were applied to predict and confirm the targeted relationship between BCYRN1 and miR-490-3p, as well as miR-490-3p and POU3F2. Further associations among BCYRN1, miR-490-3p, and POU3F2 were analyzed by rescue assays.

Results

Our results exhibited that BCYRN1 was over expressed in HCC samples, which was connected with unfavorable prognosis in HCC patients. In addition, a series of experiments exhibited that overexpression of BCYRN1 significantly expedited HCC cells growth, clone formation, and movement abilities, and vice versa. Moreover, targeted relationships between BCYRN1 and miR-490-3p, as well as miR-490-3p and POU3F2 were affirmed by dual luciferase assay. Furthermore, POU3F2 expression was negatively connected with the expression of miR-490-3p and positively associated with BCYRN1 expression. Whilst, either overexpression of miR-490-3p or knockdown of POU3F2 could remarkably inhibit the increasing trends of proliferation, clone formation, invasion, and migration abilities induced by BCYRN1 in HCC cells.

Conclusions

BCYRN1, served as a competing endogenous RNA, up-regulated the expression of POU3F2 to promote the development of HCC through sponging miR-490-3p, supplying novel molecular targets and underlying prognostic biomarkers for HCC therapy.

ERCC1-C19007T基因多态性与中晚期食管癌铂类药物化疗敏感性的Meta分析

目的

定量分析中晚期食管癌患者切除修复交叉互补基因1(excision repair cross comple-menting 1, ERCC1)C-19007T基因多态性与铂类药物化疗敏感性的关系.

方法

计算机检索PubMed、EMBASE、Cochrane Library, 中文科技期刊数据库、中国生物医学文献数据库、中国期刊全文数据库和万方数据库, 收集有关中晚期食管癌患者ERCC1-C19007T基因多态性与基于铂类药物方案化疗敏感性的相关研究, 以临床化疗有效率(完全缓解＋部分缓解)作为化疗敏感评价指标, 采用Reviewm5.2及Stata12.1软件进行统计学分析, 计算合并比值比(odd ratio, OR)及95%可信区间(confidence interval, CI).

结果

本研究共纳入8篇文献. Meta分析结果显示, 各基因型之间(CT vs CC: OR = 3.31, 95%CI: 1.94-5.64); (CT vs TT: OR = 5.48, 95%CI: 3.21-9.35); (CT vs CC+TT: OR = 4.06, 95%CI: 2.66-6.18); 差异有统计学意义, 表明ERCC1-C19007T基因多态性与中晚期食管癌对铂类化疗药物敏感性的差异有统计学意义.

结论

ERCC1-C19007T基因多态性可能与食管癌铂类药物化疗耐药相关.