Abstract
Bidens pilosa L., a traditional Chinese medicinal herb, has been used in clinical practice for the treatment of inflammatory diseases and cancer. BPA, an extract derived from the whole herb of B. pilosa L., has been shown to possess potent immunomodulatory properties by regulating tumor-associated macrophages (TAMs) and regulatory T cells (Tregs) within the tumor microenvironment (TME) in a mouse syngeneic colorectal cancer (CRC) model. RT-PCR and flow cytometry analyses showed that BPA, together with its flavonoid and polyacetylene constituents, effectively suppressed the differentiation of M2-TAMs and Tregs by downregulating Arg-1 and CD25 expression. They had minimal effects on the expression of markers associated with M1-TAMs and promoted the proliferation of CD4+ T cells that were inhibited by M2-TAMs and Tregs. In mice, BPA markedly inhibited the growth of syngeneic CRC tumors, accompanied by decreased serum levels of the immunosuppressive cytokine IL-10 and reduced expression of the proliferative marker Ki67 in tumor tissues. Moreover, BPA downregulated the mRNA expression of markers associated with M2-TAMs and Tregs, while increasing markers associated with M1-TAMs. Western blot analyses of tumor tissues revealed that BPA reduced the expression of marker proteins associated with M2-TAMs and Tregs, while increasing the expression of the immune-stimulatory markers CD80, GITR and CD4. In addition, combined treatment with BPA and 5-fluorouracil (5-FU), a commonly used chemotherapeutic agent for CRC, notably enhanced the anti-tumor effect in mice. These findings indicate that BPA, an active extract of B. pilosa L., showed antitumor activity in mice by suppressing the differentiation of pro-tumorigenic TAMs and Tregs within the TME.