Natural compounds derived from plants have been an important source of numerous clinically useful anticancer agents. Nevertheless, limited studies indicate that xanthohumol (XN), a major prenylated flavonoid in hop plants (Humulus lupulus), may possess anticarcinogenic properties. The purpose of the present study was to clarify the antitumorigenic effects and the underlying mechanism of XN on breast cancer in vivo and in vitro. A 4T1 breast tumor mouse model was used in the present study to investigate XN suppression of tumor growth as detected by tumorigenicity assays in vivo. In addition, in vitro studies revealed that XN significantly decreased cell viability, induced G0/G1 cell cycle arrest and apoptosis in MCF-7 and MDA-MB-231 cells, as confirmed by an MTT assay, flow cytometry and western blot analysis, indicating anticarcinogenic activity of XN against breast cancer. Furthermore, immunohistochemistry was performed to confirm the inactivation of the Notch signaling pathway, Notch 1 and Ki-67, in vivo; consistently, XN caused decreased activation of the Notch signaling pathway and apoptotic regulators B-cell lymphoma-2 (Bcl-2), Bcl-extra large and caspase 3, as determined by western blot analysis in vitro. This study suggests that XN may potentially be useful as a chemopreventive agent during breast hyperplasia and carcinogenesis, acting via the regulation of Notch associated apoptotic regulators in vivo and in vitro.

Xanthohumol (XN), a prenylflavonoid found in the hop plant, Humulus lupulus, exhibits a variety of biological activities. Numerous studies have reported that XN inhibits the growth of many types of cancer cells, but the effects of XN on tumor immunity have not yet been studied. We explored the effect of XN on Th1/Th2 balance and the underlying mechanism based on a BALB/c-4T1 breast cancer mouse model. The results showed that XN significantly slowed down tumor growth and inhibited expression of antitumor proliferation protein Ki-67 as well as breast cancer-specific marker cancer antigen 15-3 (CA15-3). Flow cytometric analysis revealed that XN enhanced the secretion of perforin, granzyme B and increased the ratio of CD8+/CD25+. ELISA analysis of cytokine results demonstrated that XN obviously upregulated Th1 cytokines, while downregulated Th2 cytokines. Th1/Th2 ratio analysis by flow cytometry illustrated that XN regulated the balance drift to Th1 polarization. Western blotting and immunohistochemistry (IHC) results manifested that XN induced expression of T-bet, a Th1-specific transcription factor. Furthermore, we found that XN significantly promoted the phosphorylation of signal transducer and activator of transcription (STAT)4. Our results demonstrated that XN promoted Th1/Th2 balance towards Th1 polarization, and STAT4 may play a positive role in the regulation of Th1/Th2 cytokines by XN.

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Current treatments for high-grade cervical intraepithelial neoplasia (CIN) and persistent infection with high-risk human papillomavirus (HR-HPV) type are mainly surgical interventions. However, such treatments are associated with adverse side effects and pose risks for future pregnancies. In order to reduce the requirement for excisional procedures, an effective and noninvasive therapy is needed for women at reproductive age. ALA-PDT has proved to be effective in the treatment of HPV-associated disease in several clinical investigations. In this study, the anti-proliferative effect of ALA-PDT was investigated in HPV16-immortalized cervical epithelial H8 cells. CCK-8 assay was used to measure cytotoxicity in H8 cells. The IC50 of ALA-PDT on H8 cells was about 120.75 ± 1.18 µM. We have now evaluated the mechanism by which ALA-PDT induces cell death. Annexin V-FITC/PI staining showed a significant dose-dependent induction of apoptosis by ALA-PDT in H8 cells, associated with accumulation of the tumor suppressor protein p53 and the cyclin-dependent kinase inhibitor p21. Furthermore, ALA-PDT down-regulates expression of HPV E6/E7 oncogene as well as up-regulate tumor suppressor RbAp48 protein. Together, our data provides a basis for understanding and developing ALA-PDT as a cure for HPV infection-associated diseases and prevention of cervical cancer.

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