Molecular biomarkers for aflatoxins: from adducts to gene mutations to human liver cancer

Historical review of the causes of cancer

In the early 1900s, numerous seminal publications reported that high rates of cancer occurred in certain occupations. During this period, work with infectious agents produced only meager results which seemed irrelevant to humans. Then in the 1980s ground breaking evidence began to emerge that a variety of viruses also cause cancer in humans. There is now sufficient evidence of carcinogenicity in humans for human T-cell lymphotrophic virus, human immunodeficiency virus, hepatitis B virus, hepatitis C virus, human papillomavirus, Epstein-Barr virus, and human herpes virus 8 according to the International Agency for Research on Cancer (IARC). Many other causes of cancer have also been identified by the IARC, which include: Sunlight, tobacco, pharmaceuticals, hormones, alcohol, parasites, fungi, bacteria, salted fish, wood dust, and herbs. The World Cancer Research Fund and the American Institute for Cancer Research have determined additional causes of cancer, which include beta carotene, red meat, processed meats, low fibre diets, not breast feeding, obesity, increased adult height and sedentary lifestyles. In brief, a historical review of the discoveries of the causes of human cancer is presented with extended discussions of the difficulties encountered in identifying viral causes of cancer.

Comparative analysis on the genetic polymorphisms of CYP3A5 between hepatocellular carcinoma high and low incidence area in Guangxi Zhuang Autonomous Region

AIM: To investigate the relationship between genetic polymorphism of CYP3A5 and HCC affectability through analysis of two groups of patients coming from Guangxi HCC high-incidence area and HCC low-incident area.

METHODS: We had collected 72 cases of HCC tissues and HCC-adjacent tissues from the First Affiliated Hospital of Guangxi Medical University during 2005-12/2006-09, and all the cases, who came from Guangxi HCC high-incidence area and HCC low-incidence area respectively, had been pathologically confirmed. At the same time, we used 12 cases of hepatic angioma-surrounding tissue as the normal control group. PCR-RFLP assay was used to analyze CYP3A5 genetic polymorphism of the above-mentioned samples.

RESULTS: There were statistic differences between the population with CYP3A5*1 allele frequency and the proportion of (CYP3A5*1/*1 + CYP3A5*1/*3) genotypes of Guangxi HCC high-incidence area and the population of Guangxi HCC low-incidence area (P < 0.05). There were statistic differences between the population of Guangxi HCC high-incidence area and the population of the normal control group (P < 0.05). There were no statistic differences between Guangxi HCC low-incidence area population and the normal control group.

CONCLUSION: CYP3A5 might take part in the morbidity of AFB1 related HCC.

Analysis of DNA damage induced by aflatoxin B1 in Dunkin–Hartley guinea pigs

Aflatoxin B1 (AFB1) is among the most potent naturally occurring carcinogens and classified as a group I carcinogen. Since the ingestion of aflatoxin-contaminated food is associated with several liver diseases, the aim of the present study was to evaluate the effect of 2, 20, and 200 ppb of AFB1 on DNA damage in peripheral blood lymphocytes and liver cells in Dunkin-Hartley guinea pigs. The animals were divided into four groups according to the given diet. After the treatment the lymphocytes and liver cells were isolated and DNA damage determined by Comet assay. The levels of DNA damage in lymphocytes were higher animals treated with 200 ppb of AFB1-enriched diet (P = 0.02). In the liver cells there were a relationship between the levels of DNA damage and the consumption of AFB1 in all studied groups. These results suggest that Comet assay performed on lymphocytes is a valuable genotoxic marker for high levels of exposure to AFB1 in guinea pig. Additionally our results indicate that the exposure to this toxin increases significantly and increases the level of DNA damage in liver cells, which is a key step on liver cancer development. We also suggest that the Comet assay is an useful tool for monitoring the genotoxicity of AFB1 in liver.