A methylation-specific dot blot assay for improving specificity and sensitivity of methylation-specific PCR on DNA methylation analysis

The Mismatch Repair System (MMR) in Head and Neck Carcinogenesis and Its Role in Modulating the Response to Immunotherapy: A Critical Review

Simple Summary

The dysfunction of the mismatch repair system, an important mechanism for the detection and correction of DNA replication mistakes, may often lead to instability in the length of specific genetic sequences, known as microsatellites, and to the accumulation of mutations. Microsatellite instability is a well-known risk factor for the development of colorectal cancers and other types of tumors but is also considered a positive predictor of the immunotherapy response. Malignancies harboring such a specific genomic instability are very immunogenic because of the great number of aberrant antigens they produce. Therapies based on the blockade of specific immune checkpoints have shown to induce an effective immune response against microsatellite-unstable cancer. Many studies proved that microsatellite instability has a decisive role in the carcinogenesis and the malignant progression of head and neck cancer and, in the near future, it may become a useful tool in tailoring immunotherapy also in this field of precision oncology.

Abstract

The mismatch repair (MMR) system has a major role in the detection and correction of DNA replication errors, resulting from DNA polymerase slippage or nucleotides misincorporation. Specific inherited/acquired alterations or epigenetic inactivation of MMR genes are associated with microsatellite instability (MSI): the loss of crucial function in repairing DNA alterations can promote carcinogenesis by favoring the accumulation of thousands of mutations in a broad spectrum of different anatomic sites such as colon, stomach, prostate, esophagus, endometrium, lung and head and neck. Recent extensive data suggest that tumor mutational burden strongly correlates with a clinical response to immunotherapy using checkpoint inhibitors and this response is influenced by MMR deficiency in a wide range of human solid cancers. In this context, few data about this crucial point are available for head and neck cancer (HNC). In this review, we discuss the role of MMR alterations and the resulting MSI in HNC pathogenesis. Furthermore, by summarizing the clinical available data on how they influence the progression of precancerous lesions and the risk of recurrence or second primary tumors, we want to define the current role of MSI in the management of HNC. Finally, we analyze the complex interaction between cancer cells and the immune system addressing the data now available about a potential correlation between microsatellite instability and immunotherapy response in HNC.

Association of glutathione-S-transferase p1 gene promoter methylation and the incidence of prostate cancer: a systematic review and meta-analysis

OBJECTIVE

Some studies have shown that the methylation status of the GSTP1 gene promoter is related to the incidence of prostate cancer, but this finding is still controversial. The aim of this study was to evaluate the association between glutathione-S-transferase p1 (GSTP1) promoter methylation and the incidence of prostate cancer.

METHODS

The Medline, Embase, Web of Science, and Cochrane CENTRAL databases were searched from their inception to February 22, 2019. According to the inclusion criteria, studies of the association between the methylation status of the GSTP1 gene promoter and prostate cancer were included. The difference in the incidence of GSTP1 promoter methylation in tissues, blood, or urine between patients with prostate cancer and those without prostate cancer were compared, and the results were expressed as the odds ratio (OR) and 95% confidence interval (CI). The pooled OR of each study was estimated using a fixed-effects model or a random-effects model to generate forest plots.

RESULTS

Ultimately, 15 studies (1540 samples) were included. The estimated effect from our meta-analysis showed that the incidence of GSTP1 promoter methylation was higher in patients with prostate cancer than in those without prostate cancer (OR 18.58, 95% CI 9.60-35.95, P = 0.000). GSTP1 promoter methylation was highly correlated with the incidence of prostate cancer.

CONCLUSIONS

Methylation of the GSTP1 promoter may increase the risk of prostate cancer. This study may provide a strategic direction for prostate cancer research. Pending validation of these findings, the methylation of the GSTP1 promoter may be a potential biomarker to diagnose prostate cancer.

GSTP1 methylation in cancer: a liquid biopsy biomarker?

The coding region of GSTP1 gene is preceded by a large CpG-rich region that is frequently affected by methylation. In many cancer types, GSTP1 is affected by hypermethylation and, as a consequence, it has a low expression. The aim of this review is to give an overview on GSTP1 methylation studies with a special focus on liquid biopsy, thus to summarize methods, results, sample types, different diseases, to have a complete information regarding this promising epigenetic biomarker. We used all the most valuable scientific search engines (PubMed, Medline, Scopus and Web of Science) searching the following keywords: GSTP1, methylation, cancer, urine, serum, plasma and blood. GSTP1 is a largely investigated tissue biomarker in several malignancies such as prostate, breast, lung and hepatocellular carcinoma with good performances especially for diagnostic purposes. As a liquid biopsy biomarker, it has been mainly investigated in prostate cancer (PCa) where it showed a high specificity but a low sensitivity; thus, it is recommended in combination with other biomarkers. Despite the large number of published papers and the promising results, GSTP1 has not yet entered the clinical practice even for PCa diagnosis. For this reason, further large and prospective studies are needed to validate this assay.