The clinicopathological significance of hMLH1 hypermethylation in non-small-cell lung cancer: a meta-analysis and literature review

UNC5A, an epigenetically silenced gene, functions as a tumor suppressor in non-small cell lung cancer

UNC5A has been reported to be related with human cancers. However, the function and mechanism in non-small cell lung carcinoma (NSCLC) remains unknown. We analyzed two NSCLC cell lines (A549 and H157), one normal human bronchial epithelial cell line (BEAS-2B) and the tissues of NSCLC. We used quantitative real-time PCR (qRT-PCR), western blot and immunohistochemical (IHC) staining to examine the expression of UNC5A. Methylation status of the UNC5A promoter was analyzed using methylation-specific PCR (MSP) and bisulfite sequencing PCR (BSP). We used western blot to analyzed protein levels of PI3K/Akt pathway. We found that the mRNA expression of UNCA5 was significantly downregulated in NSCLC cells and tissues. The promoter of UNC5A was hypermethylated in NSCLC cells compared to normal control cells. The expression of UNC5A could be reversed by demethylation agent in NSCLC cells. The expression of UNC5A was decreased in NSCLC samples and significantly associated with the advanced types of NSCLC. Functionally, knockdown of UNC5A promoted cell proliferation, migration, invasion and induced apoptosis in NSCLC, overexpression of UNC5A yielded the opposite result. Moreover, we found that UNC5A negatively regulated PI3K/Akt signaling pathway in NSCLC. UNC5A is a novel epigenetically silenced gene in NSCLC and consequent under-expression of UNC5A may contribute to NSCLC tumorigenesis through regulating PI3K/Akt pathway.

Gene promoter methylation and cancer: An umbrella review

Gene promoter methylation is a common epigenetic event, taking place in the early phase of tumorigenesis, which has a great potential as a diagnostic and prognostic cancer biomarker. In this umbrella review, we provide an overview on the association between gene-promoter methylation of protein-coding genes and cancer risk based on currently available meta-analyses data on gene promoter methylation. We searched MEDLINE via PubMed and the Cochrane Database of Systematic Reviews for meta-analyses that examine the association between gene-promoter methylation and cancer, published until January 2019 in English. We used AMSTAR to assess the quality of the included studies and applied a set of pre-specified criteria to evaluate the magnitude of each association. We provide a comprehensive overview of 80 unique combinations between 22 different genes and 18 cancer outcomes, all of which indicated a positive association between promoter hypermethylation and cancer. In total, the 70 meta-analyses produced significant results under a random-effects model with odds ratios that ranged from 1.94 to 26.60, with the summary effect being in favor of the unmethylated group in all cases. Three of the strong evidence associations involve RASSF1 methylation on bladder cancer risk (OR = 18.46; 95% CI: 12.69-26.85; I2 = 0%), MGMT methylation on NSCLC (OR = 4.25; 95% CI: 2.83-6.38; I2 = 22.4%) and RARB methylation on prostate cancer (OR = 6.87; 95% CI: 4.68-10.08; I2 = 0%). Meta-analyses showed a moderate quality, AMSTAR score ranging from 4 to 9 (Mdn = 8; IQR: 7.0 to 8.0). As primary studies and meta-analyses on the subject accumulate, more genetic loci may be found to be highly associated with specific cancer types and hence the biomarker sets will become wider.

HDAC6 regulates DNA damage response via deacetylating MLH1

MutL homolog 1 (MLH1) is a key DNA mismatch repair protein, which plays an important role in maintenance of genomic stability and the DNA damage response. Here, we report that MLH1 is a novel substrate of histone deacetylase 6 (HDAC6). HDAC6 interacts with and deacetylates MLH1 both in vitro and in vivo Interestingly, deacetylation of MLH1 blocks the assembly of the MutSα-MutLα complex. Moreover, we have identified four novel acetylation sites in MLH1 by MS analysis. The deacetylation mimetic mutant, but not the WT and the acetylation mimetic mutant, of MLH1 confers resistance to 6-thioguanine. Overall, our findings suggest that the MutSα-MutLα complex serves as a sensor for DNA damage response and that HDAC6 disrupts the MutSα-MutLα complex by deacetylation of MLH1, leading to the tolerance of DNA damage.

The Relevance of Gender in Tumor-Influencing Epigenetic Traits

Tumorigenesis as well as the molecular orchestration of cancer progression are very complex mechanisms that comprise numerous elements of influence and regulation. Today, many of the major concepts are well described and a basic understanding of a tumor's fine-tuning is given. Throughout the last decade epigenetics has been featured in cancer research and it is now clear that the underlying mechanisms, especially DNA and histone modifications, are important regulators of carcinogenesis and tumor progression. Another key regulator, which is well known but has been neglected in scientific approaches as well as molecular diagnostics and, consequently, treatment conceptualization for a long time, is the subtle influence patient gender has on molecular processes. Naturally, this is greatly based on hormonal differences, but from an epigenetic point of view, the diverse susceptibility to stress and environmental influences is of prime interest. In this review we present the current view on which and how epigenetic modifications, emphasizing DNA methylation, regulate various tumor diseases. It is our aim to elucidate gender and epigenetics and their interconnectedness, which will contribute to understanding of the prospect molecular orchestration of cancer in individual tumors.

Hypermethylation of MDFI promoter with NSCLC is specific for females, non-smokers and people younger than 65

Non-small cell lung carcinoma (NSCLC) is a major subtype of lung cancer. Aberrant DNA methylation has been frequently observed in NSCLC. The aim of the present study was to investigate the role of MyoD family inhibitor (MDFI) methylation in NSCLC. Formalin-fixed paraffin-embedded tumor tissues and adjacent non-cancerous tissues were collected from a total of 111 patients with NSCLC. A methylation assay was performed using the quantitative methylation-specific polymerase chain reaction method. The percentage of methylated reference was used to represent the methylation level of the MDFI promoter. Data mining of a dataset from The Cancer Genome Atlas (TCGA) demonstrated that MDFI promoter methylation levels were significantly increased in 830 tumor tissues compared with 75 non-tumor tissues (P=0.012). However, the results on tissues obtained in the present study indicated that the MDFI promoter methylation levels in tumor tissues were not significantly different compared with those in the adjacent non-tumor tissues (P=0.159). Subsequent breakdown analysis identified that higher MDFI promoter methylation levels were significantly associated with NSCLC in females (P=0.031), but not in males (P=0.832). Age-based subgroup analysis demonstrated that higher MDFI promoter methylation levels were significantly associated with NSCLC in younger patients (≤65 years; P=0.003), but not in older patients (P=0.327). In addition, the association of MDFI methylation with NSCLC was significant in non-smokers (P=0.014), but not in smokers (P=0.832). Similar results also have been determined from subgroup analysis of the TCGA datasets. The Gene Expression Omnibus database indicated MDFI expression restoration in partial lung cancer cell lines (H1299 and Hotz) following demethylation treatment. However, it was identified that MDFI promoter hypermethylation was not significantly associated with prognosis of NSCLC (P>0.05). In conclusion, the present study indicated that the association of higher methylation of the MDFI promoter with NSCLC may be specific to females, non-smokers and people aged ≤65.

Association Between hMLH1 Promoter Methylation and Risk of Gastric Cancer: A Meta-Analysis

Background: Human mutL homolog 1 (hMLH1) is located on chromosome 3q21-23. As a classic tumor suppressor gene, many researchers have studied the association between hMLH1 promoter methylation and gastric cancer, but their conclusions were not always consistent. Therefore, we performed a meta-analysis to make a more integrated and precise estimate of the associations.

Method: PubMed, EMBASE, and Cochrane Library were retrieved without language restrictions. Data were analyzed by Review Manager 5.2 and Stata 12.0 software. Odds ratio (OR) with 95% confidence interval (95%CI) was used to assess the statistical associations.

Result: A total of 39 studies published before January 20, 2018 were included in this study. The results indicated that the frequency of hMLH1 promoter methylation in gastric cancers was substantially higher than that in non-cancer controls (OR = 7.94, 95%CI = 4.32–14.58, P < 0.001). Furthermore, hMLH1 promoter methylation had considerable associations with lymph node metastasis, microsatellite instability (MSI), and low expression of hMLH1 protein (OR = 1.53, 95%CI = 1.04–2.26, P = 0.03; OR = 15.33, 95%CI = 9.26–25.36, P < 0.001; OR = 37.86, 95%CI = 18.03–79.50, P < 0.001, respectively). No association was found between hMLH1 promoter methylation and Lauren classification or Helicobacter pylori (HP) infection status.

Conclusion: The present study provides evidence that promoter methylation of hMLH1 is a major causative event in the occurrence and development of human gastric cancer.

Aberrant methylation of mutL homolog 1 is associated with increased risk of non-small cell lung cancer

BACKGROUND

Non-small cell lung cancer (NSCLC) is a common malignant tumor. DNA hypermethylation in the promoter region has been served as a potential molecular marker for several tumors. The goal of the current study was to assess the diagnostic ability of mutL homolog 1 (MLH1) promoter methylation in NSCLC.

METHODS

A total of 111 NSCLC patients' paired tissue samples were obtained to explore the association between MLH1 promoter methylation and NSCLC by methylation-specific polymerase chain reaction (MSP) method. Public databases including The Cancer Genome Atlas (TCGA) and Gene Expression Omnibus (GEO) were used to verify our findings.

RESULTS

Our results showed a significantly higher MLH1 methylation frequency in tumor tissue samples than their paired adjacent tissues (P = .008). ROC curve indicated that MLH1MSP assay was a sensitive but not a specific method in the diagnosis for NSCLC (sensitivity = 0.964, specificity = 0.135, AUC = 0.550). And the association between the methylation level and clinical characteristics has no statistical significance. TCGA cohort evinced a higher methylation probability in tumor group compared with nontumor group (the mean β value: -0.449 [-0.467, -0.437] vs -0.466 [-0.472, -0.437], P = .011), which was consistent with our results. Meanwhile, an inverse correlation between MLH1 methylation and MLH1 expression was detected in TCGA and GEO databases.

CONCLUSIONS

The MSP method for MLH1 methylation was a sensitive but not a specific diagnostic method for NSCLC.

Prognostic role of platelet to lymphocyte ratio in hepatocellular carcinoma: a systematic review and meta-analysis

BACKGROUND AND AIMS

Several studies were conducted to explore the prognostic significance of platelet to lymphocyte ratio (PLR) in hepatocellular carcinoma (HCC), however, contradictory results across most reports were documented. To this end, we present a systematic review that aims to summarize the prognostic significance of PLR in patients with HCC.

RESULTS

A total of 10 studies involving a total of 2,315 patients were identified. The Newcastle-Ottawa Quality Assessment Scale (NOS) of each included study was greater than or equal to 5. The results indicated that high PLR was significantly associated with a worse OS when compared to the low PLR (HR = 1.60, 95% CI = 1.23-2.08, p = 0.0005; I2 = 88%, p < 0.00001). Similar results were detected in the subgroup analysis of the analysis model, cut-off value, ethnicity, sample size and therapy. However, no obvious correlation between the PLR and DFS/RFS in patients with HCC was observed (HR = 1.21, 95% CI = 0.87-1.67, p = 0.26; I2 = 61%, p = 0.07).

MATERIALS AND METHODS

A complete literature search in the PubMed, Cochrane Library and Embase database was performed. Retrospective and prospective studies focusing on the role of PLR on the prognosis in HCC were all deemed as "suitable" for our scope. The endpoints determined were: the overall survival (OS), disease-free survival (DFS), recurrence-free survival (RFS) and the progress free survival (PFS).

CONCLUSIONS

The study revealed that high PLR is an unfavorable predictor of OS in patients with HCC, and high PLR is a promising prognostic biomarker for HCC, especially for patients in Asia.