Banxia Xiexin Decoction inhibits colitis-associated colorectal cancer development by modulating STAT3 signaling and gut microbiota

Objective: To investigate the therapeutic effects of Banxia Xiexin Decoction (BXD), a herbal medicine formula, on inflammation and the imbalance of the gut microbiota in a rat model of colorectal cancer (CRC) induced by azoxymethane (AOM) /dextran sulfate sodium (DSS). Methods: A total of 75 male C57BL/6 mice were randomly divided into five groups: normal control group (NC), model group (MODEL), low-dose BXD treatment group (L-BXD), high-dose BXD treatment (H-BXD) group and MS treatment group (MS). BXD and MS were used in CRC mice at the doses of 3.915 g/kg, 15.66 g/kg, 0.6 g/kg for 3 weeks consecutively. Histopathological changes in the colon were observed using hematoxylin-eosin (HE) staining. The content of inflammatory factors in serum was detected by an enzyme-linked immunosorbent assay (ELISA), and the expression of mRNA and protein of genes related to immunity, apoptosis, inflammation, and inflammatory factors was evaluated. Changes in the intestinal flora of mouse fecal were determined based on high-throughput sequencing of the 16S rRNA microbial gene. Results: Compared to the model group, the low-dose BXD and high-dose BXD groups decreased the number of colon tumors, reversed weight loss, and shortened colon length of mice. The pathological examination showed that BXD alleviated the malignancy of intestinal tumors. It also suppressed signal transducer and activator of transcription 3 (STAT3), matrix metalloproteinase-9 (MMP-9), and transforming growth factor beta 1 (TGF-β1) expression, while increasing the expression of the tight junction protein ZO-1 in colon tissues. Additionally, the levels of key pathway proteins involved in inflammation (phosphorylated-STAT3, Bcl-2, COX-2) and cell cycle regulatory molecules (c-Myc and PCNA) were reduced. According to 16S rRNA sequence analysis, BXD enhanced the relative abundance of potentially beneficial bacteria, while that of cancer-related bacteria decreased. Conclusion: BXD plays a preventive role in developing colorectal cancer; its mechanisms are related to the inhibition of inflammation and tumor proliferation, as well as maintenance of intestinal homeostasis.