Background: Colorectal Cancer (CRC) is one of the top three malignancies with the highest incidence and mortality.

Objective: The study aimed to identify the effect of Traditional Chinese Medicine (TCM) on postoperative patients with stage II-III CRC and explore the core herb combination and its mechanism.

Methods: An observational cohort study was conducted on patients diagnosed with stage II-III CRC from January 2016 to January 2021. The primary outcome was disease-free survival, which was compared between the patients who received TCM or not, and the secondary outcome was the hazard ratio. The relevance principle was used to obtain the candidate herb combinations, and the core combination was evaluated through an assessment of efficacy and representativeness. Then, biological processes and signaling pathways associated with CRC were obtained by Gene Ontology function, Kyoto Encyclopedia of Gene and Genomes pathway, and Wikipathway. Furthermore, hub genes were screened by the Kaplan-Meier estimator, and molecular docking was employed to predict the binding sites of key ingredients to hub genes. The correlation analysis was employed for the correlations between the hub genes and tumor-infiltrating immune cells and hypoxiarelated genes. Ultimately, a quantitative polymerase chain reaction was performed to verify the regulation of hub genes by their major ingredients.

Results: A total of 707 patients were included. TCM could decrease the metastatic recurrence associated with stage II-III CRC (HR: 0.61, log-rank P < 0.05). Among those patients in the TCM group, the core combination was Baizhu → Yinchen, Chenpi, and Fuling (C combination), and its antitumor mechanism was most likely related to the regulation of BCL2L1, XIAP, and TOP1 by its key ingredients, quercetin and tangeretin. The expression of these genes was significantly correlated with both tumor-infiltrating immune cells and hypoxia- related genes. In addition, quercetin and tangeretin down-regulated the mRNA levels of BCL2L1, XIAP, and TOP1, thereby inhibiting the growth of HCT116 cells.

Conclusion: Overall, a combination of four herbs, Baizhu → Yinchen, Chenpi, and Fuling, could reduce metastatic recurrence in postoperative patients with stage II-III CRC. The mechanism may be related to the regulation of BCL2L1, XIAP, and TOP1 by its key ingredients quercetin and tangeretin.