EXPERIMENTAL COLORECTAL CARCINOGENESIS IN ALBINO WISTAR RATS: INCIDENCE, TUMOUR BURDEN, AND INDUCTION SUCCESS RATE FOLLOWING 1,2-DIMETHYLHYDRAZINE EXPOSURE — REVIEW

Background: Colorectal cancer (CRC) remains one of the leading causes of cancer-related mortality worldwide. To better understand colorectal carcinogenesis and evaluate chemopreventive interventions, chemically induced animal models are essential. Among these, the 1,2-dimethylhydrazine (DMH)-induced colorectal cancer model in albino Wistar rats is particularly valuable, as it closely mimics the histopathological and molecular characteristics of human sporadic CRC. Objective: This systematic review aims to evaluate the incidence rate, tumor burden, induction success, histopathological progression, and molecular characteristics of DMH-induced colorectal carcinogenesis in albino Wistar rats. Methods: We conducted a systematic review following PRISMA 2020 guidelines. A comprehensive literature search was performed across PubMed, Scopus, Web of Science, Science Direct, and Google Scholar for studies published between 2000 and 2025. We included experimental studies focusing on DMH-induced colorectal cancer in albino Wistar rats. Data extracted included induction protocols, tumor incidence, aberrant crypt foci (ACF) formation, adenoma occurrence, adenocarcinoma prevalence, and molecular alterations. Results: Thirty-six eligible studies were included in the final synthesis. Across these studies, DMH doses ranged from 20 to 40 mg/kg, administered either subcutaneously or intraperitoneally over 8 to 20 weeks. The model proved highly reliable, with tumor induction success rates varying between 68% and 100%, and adenocarcinoma incidence ranging from 55% to 95%. Aberrant crypt foci were detected in nearly all DMH-treated subjects. Consistent molecular findings included heightened oxidative stress, β-catenin accumulation, cyclooxygenase-2 (COX-2) overexpression, inflammatory cytokine activation, and DNA methylation abnormalities. Conclusion: The DMH-induced colorectal carcinogenesis model in albino Wistar rats is highly reproducible and carries substantial translational relevance for human CRC research. Its high tumor induction rates and predictable histopathological progression make it an excellent platform for preclinical therapeutic investigations.