Colorectal cancer (CRC) is a prevalent malignancy, often diagnosed at advanced stages. 5-fluorouracil (5FU) is a common chemotherapeutic agent for CRC but is limited by toxicity, variable responses, and resistance. Thus, alternative preventive and therapeutic strategies with proven in vivo antineoplastic activity are essential. Hybrid molecules, such as the 5FU-curcumin conjugate, combine the 5FU pharmacophore with curcumin, an antioxidant pigment, to enhance efficacy and reduce adverse effects.

A colorectal cancer (CRC) model induced by azoxymethane (AOM) and dextran sodium sulfate (DSS) was standardized in Balb/c mice, evaluating two induction protocols: protocol 1 (AOM + 1 cycle of DSS) and protocol 2 (AOM + 2 cycles of DSS), selecting the optimal one through histopathological analysis. Then, treatment was administered using 5-fluorouracil (control) and the 5-fluorouracil-curcumin hybrid in two periods (weeks 3 to 7 and weeks 5 to 10). Positive (CRC-AOM/DSS) and negative controls were included. After euthanasia, the colon was extracted for methylene blue staining and histopathological analysis. The study was approved by the bioethics committee (Act No. 114/2017, UdeA).

A single DSS cycle (protocol 1) did not induce tumors in all animals, whereas two cycles (protocol 2) did after week 10. Wilcoxon test analysis showed no significant sex differences, confirming that the AOM/DSS CRC model in BALB/c mice replicates the adenocarcinomatous process and is applicable to both sexes with one AOM dose and two DSS cycles. Preneoplastic lesions appeared in week 3, progressing to tumors by week 12. Dysplasia was observed from week 2, preceding neoplastic proliferation and infiltration. Fibrosis developed in response to inflammation detected in week 2. Both 5FU and 5FU-curcumin delayed lesion progression, with mild to moderate histopathological alterations compared to the positive control. However, tumor growth resumed by week 12 . Mice treated with 5FU experienced up to 40% mortality and weight loss, whereas those receiving 5FU-curcumin did not, indicating lower toxicity. Histopathological analysis confirmed reduced tissue damage, as ulceration levels were lower in the 5FU-curcumin group than in 5-FU alone.

- The AOM/DSS system effectively replicates colorectal cancer progression in humans and is useful for evaluating chemopreventive strategies. -The model can be applied to both male and female mice. -The 5FU-Curcumin hybrid slightly delays tumor progression, but its effect is insufficient after treatment discontinuation. -Unlike 5FU alone, the 5FU-Curcumin hybrid showed no toxicity and slightly reduced tissue damage. -Hybrids like 5FU-Curcumin could be a promising strategy for colorectal cancer chemoprevention.