Establishment and refinement of a DEN-induced hepatocellular carcinoma model in rats

Hepatocellular carcinoma is one of the most common malignant tumors in the world with complex etiology, high tumor heterogeneity, and low efficacy of treatment. The establishment of an animal model that is close to the clinical situation of hepatocellular carcinoma and can be successfully modeled many times is of great significance to the study of the pathogenesis, diagnosis and treatment of hepatocellular carcinoma. We used Diethylnitrosamine (DEN) to induce hepatocellular carcinoma in rodents and compared four models of DEN-induced hepatocellular carcinoma. Group C (Control): rats were fed a standard laboratory rat diet and freely drank normal water. Group P (Peritoneal injection): rats were administered an IP injection (50 mg/kg/week) between 5 and 23 weeks after birth. Ten microliter of DEN solution would be injected per g of rat. Group O (DEN-Fed group): rats were allowed unrestricted access to water contaminated with 0.01 % DEN between the ages of 7 and 15 weeks. 0.2 mL of DEN drinking water was consumed per gram of rat. Group P+O (Combined peritoneal injection and Oral feeding): rats were administered an IP injection (50 mg/kg) at weeks 3 and 5 post-birth, and they freely drank water contaminated with 0.012 % DEN between weeks 7 and 14 post-birth. We used an ultrasound scan, biochemical testing, haematoxylin, and eosin staining, Masson staining, Wolf scarlet staining, Ki67, CD34, a-SMA, CD8, and CD68 staining to compare between groups. Liver dissection and ultrasound scan showed that compared to other groups, the liver of Group P+O was darker in color, with more grey-white cancer nodules and larger localized tumors, and the structure of the tumors was slightly disorganized, with the elastography hardness of the middle lobe and the right lobe was slightly increased. The alanine aminotransferase and total bilirubin of Group P+O were higher than those of Group O but lower than those of Group P. Haematoxylin and eosin staining showed that the tumors of Group P+O were large, with large tumor cords and pseudo-glandular, the degree of differentiation was medium and surrounded by more fatty lesions. We conclude that combined DEN treatment is more effective, stable, and has the advantage of multiple modalities, leading to faster tumor formation.