Results of identifying mutations in the TP53 gene and comparing them with p53 protein expression in hepatocellular carcinoma tissues

Abstract

Background: Mongolia’s incidence and mortality rates for hepatocellular carcinoma (HCC) are eight times higher than the global average. According to 2023 statistics from the National Cancer Center of Mongolia, 7,244 cases of HCC were recorded, with 4,556 deaths. Risk factors for HCC include hepatitis B and C infections, alcohol and tobacco use, and exposure to toxins such as aflatoxin. In Asian countries, hepatitis B virus (HBV) infection and aflatoxin exposure are particularly common causes. The TP53 (p53) gene encodes the p53 protein with a weight of 53 kD, is located on the short line of chromosome 17 (17p13), and is a transcription factor that regulates the cell division cycle, so it is considered a tumor suppressor gene. Mutations of the TP53 gene occur in 50% of all tumors, and mutations of this gene are also found in hepatocellular carcinoma. Hepatitis B and C infections and aflatoxin exposure are known to induce TP53 gene mutations, particularly at codons 249 and 258 in exon 7, which are frequently identified in HCC. Studies also suggest that TP53 mutations and p53 protein accumulation in cancer tissues influence tumor progression and patient prognosis. In Mongolia, there is a lack of research on this topic, providing the basis for our study. Aim: To investigate TP53 gene mutations and p53 protein expression in HCC tissues and compare these findings with selected clinical, laboratory, and pathological parameters. Materials and Methods: The study included 50 participants diagnosed with HCC and treated with surgery at different stages of the disease. Genomic DNA was extracted from parafÏn-embedded tissue samples, and allele-specific PCR was conducted to identify TP53 gene mutations at codons 249 and 258 in exon 7. Immunohistochemistry was used to evaluate p53 protein expression, which was then correlated with clinical, laboratory, and pathological indicators. Results: Participants ranged in age from 33 to 79 years (mean: 64.06±9.1), comprising 21 males (42%) and 29 females (58%). TP53 gene mutations at codon 249 were not observed in any samples (0%), but mutant alleles at codon 258 were identified in 15 (30%) cases. Statistical analysis found no significant association between the TP53 gene codon 258 mutation and age (p=0.558), sex (p=0.851), HBV infection (p=0.288), HCV infection (p=0.902), cirrhosis (p=0.736), fibrosis (p=0.985), steatosis (p=0.368), serum AFP levels (p=0.662), tumor number (p=0.665), tumor size (p=0.439), or vascular invasion (p=0.849). In 46 tissue samples, p53 protein expression was assessed, revealing positive staining in 26 (57%) cases. Positive p53 expression was significantly associated with TP53 gene codon 258 mutations (p=0.004) and HBV infection (p=0.002). Conclusions: 1. The predominance of mutations at codon 258 of the TP53 gene in hepatocellular carcinoma (HCC) tissues suggests that this is primarily driven by the effects of hepatitis virus infection. Additionally, the absence of mutations at codon 249 indicates that aflatoxin exposure currently plays a minor role in the development of HCC among Mongolians. 2. In the presence of TP53 gene mutations, the expression of p53 protein is elevated in liver tissues, which is associated with hepatitis B virus (HBV) infection.