Extracts from Asian medicinal herbs are known to be successful therapeutic agents against cancer. In this study, the effects of three types of herbal extracts on anti-tumor growth were examined. Among the three types of herbal extracts, H9 showed stronger anti-tumor growth effects than H5 and H11 in vivo. To find the molecular mechanism by which H9 inhibited the proliferation of breast cancer cell lines, the levels of apoptotic markers were examined. Proapoptotic markers, including cleaved PARP and cleaved caspases 3 and 9, were increased, whereas the anti-apoptotic marker Bcl-2 was decreased by H9 treatment. Next, the combined effect of H9 with the chemotherapeutic drugs doxorubicin/cyclophosphamide (AC) on tumor growth was examined using 4T1-tumor-bearing mice. The combined treatment of H9 with AC did not show additive or synergetic anti-tumor growth effects. However, when tumor-bearing mice were co-treated with H9 and the targeted anti-tumor drug trastuzumab, a delay in tumor growth was observed. The combined treatment of H9 and trastuzumab caused an increase of natural killer (NK) cells and a decrease of myeloid-derived suppressor cells (MDSC). Taken together, H9 induces the apoptotic death of tumor cells while increasing anti-tumor immune activity through the enhancement of NK activity and diminishment of MDSC.
Keywords: Apoptosis; Breast cancer; Doxorubicin/Cyclophosphamide; Medicinal herbal extracts; Trastuzumab.