Immunohistochemical expression of mismatch repair genes (hMSH2 and hMLH1) in hepatocellular carcinoma in Egypt

Hepatocellular carcinoma in a transplanted donor liver and colon cancer developing in a patient with a complex background: A case report

The development of tumors in livers transplanted from hepatitis B virus (HBV)-negative donors to patients with hepatitis B and cirrhosis is rare. The present study describes the case of a woman in her 60s who developed hepatocellular carcinoma (HCC) in her grafted liver, 19 years after transplantation, as well as a metachronous colorectal tumor. The pathological findings, including clinical, immunohistochemical and molecular results, are described in the present case report. The liver tumor was a conventional HCC and the colorectal tumor comprised a tubular adenocarcinoma. Immunohistochemistry of both tumors showed a loss of expression of mutL homolog 1 and postmeiotic segregation increased 2 in the tumor cells, confirming microsatellite instability-high (MSI-H) status. Furthermore, a molecular study detected the presence of genes located on the Y chromosome in the normal and tumor tissues of the liver, proving that the HCC occurred in the grafted liver. The present report also discusses that prolonged use of immunosuppressive drugs to prevent post-transplant rejection, poorly controlled diabetes mellitus and MSI-H may have contributed to the risk of tumor development.

The role of DNA damage and repair in liver cancer

Hepatocellular carcinoma is rapidly becoming a major cause of global mortality due to the ever-increasing prevalence of obesity. DNA damage is known to play an important role in cancer initiation, however DNA repair systems are also vital for the survival of cancer cells. Given the function of the liver and its exposure to the gut, it is likely that DNA damage and repair would be of particular importance in hepatocellular carcinoma. However, many contemporary reports have neglected the role of individual pathways of DNA damage and repair in their hypotheses. This review, therefore, aims to provide a concise overview for researchers in the field of liver cancer to understand the pathways of DNA damage and repair and their individual roles in hepatocellular carcinoma.

The Pivotal Role of DNA Repair in Infection Mediated-Inflammation and Cancer

Pathogenic and commensal microbes induce various levels of inflammation and metabolic disease in the host. Inflammation caused by infection leads to increased production of reactive oxygen species (ROS) and subsequent oxidative DNA damage. These in turn cause further inflammation and exacerbation of DNA damage, and pose a risk for cancer development. Helicobacter pylori-mediated inflammation has been implicated in gastric cancer in many previously established studies, and Fusobacterium nucleatum presence has been observed with greater intensity in colorectal cancer patients. Despite ambiguity in the exact mechanism, infection-mediated inflammation may have a link to cancer development through an accumulation of potentially mutagenic DNA damage in surrounding cells. The multiple DNA repair pathways such as base excision, nucleotide excision, and mismatch repair that are employed by cells are vital in the abatement of accumulated mutations that can lead to carcinogenesis. For this reason, understanding the role of DNA repair as an important cellular mechanism in combatting the development of cancer will be essential to characterizing the effect of infection on DNA repair proteins and to identifying early cancer biomarkers that may be targeted for cancer therapies and treatments.

Involvement of DNA damage response pathways in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) has been known as one of the most lethal human malignancies, due to the difficulty of early detection, chemoresistance, and radioresistance, and is characterized by active angiogenesis and metastasis, which account for rapid recurrence and poor survival. Its development has been closely associated with multiple risk factors, including hepatitis B and C virus infection, alcohol consumption, obesity, and diet contamination. Genetic alterations and genomic instability, probably resulted from unrepaired DNA lesions, are increasingly recognized as a common feature of human HCC. Dysregulation of DNA damage repair and signaling to cell cycle checkpoints, known as the DNA damage response (DDR), is associated with a predisposition to cancer and affects responses to DNA-damaging anticancer therapy. It has been demonstrated that various HCC-associated risk factors are able to promote DNA damages, formation of DNA adducts, and chromosomal aberrations. Hence, alterations in the DDR pathways may accumulate these lesions to trigger hepatocarcinogenesis and also to facilitate advanced HCC progression. This review collects some of the most known information about the link between HCC-associated risk factors and DDR pathways in HCC. Hopefully, the review will remind the researchers and clinicians of further characterizing and validating the roles of these DDR pathways in HCC.

Promoter methylation of MLH1, PMS2, MSH2 and p16 is a phenomenon of advanced-stage HCCs

Epigenetic silencing of tumour suppressor genes has been observed in various cancers. Looking at hepatocellular carcinoma (HCC) specific protein silencing was previously demonstrated to be associated with the Hepatitis C virus (HCV). However, the proposed HCV dependent promoter methylation of DNA mismatch repair (MMR) genes and thereby enhanced progression of hepatocarcinogenesis has been the subject of controversial discussion. We investigated promoter methylation pattern of the MMR genes MLH1, MSH2 and PMS2 as well as the cyclin-dependent kinase inhibitor 2A gene (p16) in 61 well characterized patients with HCCs associated with HCV, Hepatitis B virus infection or alcoholic liver disease. DNA was isolated from formalin-fixed, paraffin-embedded tumour and non-tumour adjacent tissue and analysed by methylation-specific PCR. Moreover, microsatellite analysis was performed in tissues showing methylation in MMR gene promoters. Our data demonstrated that promoter methylation of MLH1, MSH2, PMS2 and p16 is present among all considered HCCs. Hereby, promoter silencing was detectable more frequently in advanced-stage HCCs than in low-stage ones. However, there was no significant correlation between aberrant DNA methylation of MMR genes or p16 and HCV infection in related HCC specimens. In summary, we show that promoter methylation of essential MMR genes and p16 is detectable in HCCs most dominantly in pT3 stage tumour cases. Since loss of MMR proteins was previously described to be not only responsible for tumour development but also for chemotherapy resistance, the knowledge of mechanisms jointly responsible for HCC progression might enable significant improvement of individual HCC therapy in the future.

Immunohistochemical analysis of mismatch proteins in carcinogenesis of the lower lip

AIM

This study investigated the immunohistochemical expression of hMLH1 and hMSH2 proteins in lower lip squamous cell carcinoma (SCC) and actinic cheilitis (AC), to contribute to the understanding of the development of lower lip cancer.

METHODS AND RESULTS

Forty cases of lower lip AC and SCC were studied. Quantitative immunohistochemical analysis was undertaken by counting 1000 cells (positive and negative) in each lesion. Statistical evaluation included Student's t-test and one-way ANOVA. For SCC and AC, the mean number of hMLH1- and hMSH2-positive cells decreased with advanced stage of the lesion. The largest mean number of immunostained cells was observed in AC cases without dysplasia or with mild dysplasia (hMLH1: 721.23 ± 88.116; hMHS2: 781.50 ± 156.93). Intermediate values were obtained for AC with moderate or severe dysplasia (hMLH1: 532.86 ± 197.72; hMHS2: 611.14 ± 172.48). Lower lip SSCs presented the smallest number of positive cells (hMLH1: 255.03 ± 199.47; hMHS2: 518.38 ± 265.68). A statistically significant difference was observed between groups (P < 0.001).

CONCLUSIONS

The results support the hypothesis that changes in the immunoexpression of these mismatch proteins are related to the process of carcinogenesis of the lower lip.