Aflatoxins are the secondary metabolites of the fungi namely, Aspergillus flavus and A. parasiticus. They can colonize and contaminate grain before harvest or during storage. There are about twenty related secondary forms of aflatoxins, and subtypes B₁, B₂, G₁, G₂. These aflatoxins frequently contaminate the foods and feeds (Yu J et al, 2000, Imanaka BT et al, 2007). Aflatoxin B1, the most toxic, is a potent hepatocarcinogenic and genotoxigenic metabolites that have been classified as group I carcinogens by International Agency of Research on Cancer (International Agency for Research on cancer, 1993). Aflatoxin M1 is found in milk of lactating cows that have consumed feeds contaminated with aflatoxin B₁. Aflatoxin M₁ was originally classified as a Group 2B human carcinogen in 1993, but subsequent evidences of its cytotoxic, genotoxic and carcinogenic effects led to a new categorization of aflaoxin M1 as Group I (International Agency for Research on cancer, 2002). Aflatoxins can affect a wide range of commodities, including crops, cereals, oilseeds, spices, tree nuts, milk, meat, and dried fruit (Wilson DM et al, 1994, Bao L et al, 2010). Mongolia has been imported foods about 60 percent of food demands including wheat, flour, rice, milk, dairy products, peanuts and maize. This situation is required to study aflatoxin contamination in food in Mongolia. Epidemiological studies have found that dietary exposure to aflatoxin and chronic infection with hepatitis B, C virus are three major risk factors for HCC (Viviani et al. 1997; Hall et al. 2003). HCC as a result of chronic aflatoxin exposure has been well documented, presenting most often in persons with chronic hepatitis B virus (HBV) infection (Wild and Gong, 2010). The risk of liver cancer in individuals exposed to chronic HBV infection and aflatoxin is up to 30 times greater than the risk in individuals exposed to aflatoxin (Groopman et al., 2008). According to the WHO, the national liver cancer incidence rates was 54.1 per 100.000 population, the prevalence of HBV and HCV infection in 11.8%, 15.6% were respectively (J.Abarsanaa, 2012). This situation is a serous public health problem in Mongolia. Thus, we aimed to carry out the monitoring surveillance survey on the aflatoxin contamination level in some food.

Background: Nucleic acid sequencing is a multi-step process taken place in medical research or diagnostic laboratories. Since the emerge of second generation sequencing technology generally referred as next generation sequencing (NGS), the mass parallel reads covering human genome or transcriptome is achieved by cost cut down over thousand folds. Though the technology made tremendous push forward to various applications, its data analysis time and effort still takes worrisome time and human effort, bringing the emerge of next-step demand: targeted mass sequencing of only desired part from human genome or transcriptome with lower material cost and labor. By targeted sequencing, both run cost and data analysis process can be further cut down, and the read results are more reliable on changes such as determining varied number of repeats, heterozygote alleles, deletions, chromosomal scale abnormality and more. Objective: In this study, we explored the utilization of biotinylated RNA baits on captured sequencing of cancer marker genes functional regions. Method: Targeted NGS was achieved by capturing desired genomic regions using preparatory nucleic acid probes. RNA bait capturing of desired genomic regions has shown to have high specificity and quality.
The study was carried out with informed consent obtained from patients, with the approval №53 in 2018.03.15 by Medical Ethics committee, Ministry of Health, Mongolia. Result: By preparing library of biotinylated RNA baits with 75000 unique sequences, we achieved mass parallel sequencing of human 410 cancer-marker-genes’ exons and UTRs with average read depth ~760, and covered thousands of SNPs on 5 genomic DNA samples. Tissue samples derived from breast cancer and ovary cancer had SNP and deletion on 7 marker genes (BRCA1, BRCA2, ATM, BRIP1, PTEN, TP53, RAD51C) not registered in database. Conclusion Experiments showed RNA baits with up to 117 nucleotide length, produced from ssDNA oligonucleotide stock, can be utilized to capture desired regions of human genome, and bring the cost of captured mass sequencing to 1500 USD, with 93.14-93.33% of Q30 read quality.