Extract Of Hedyotis Diffusa Willd Inhibited Activation Of STAT3 And Induced Apoptosis Of Cancer Cells

Traditional Chinese Medicine are complicated but useful medicine, most of which have been used in clinical practice for hundreds of years.Nowadays, it is urgently needed to investigate its mechanism for modern drug development. Hedyotis Diffusa Willd, one of the Traditional Chinese Medicine, has been widely used for many years in clinical application for clearing heat and detoxifying, promoting blood circulation to arrest pain, and subsidence of a swelling and diuresis. Moreover, it also showed remarkable effect on treatment of cancer and inflammation. Recently, it has been reported that the extracts of Hedyotis Diffusa Willd can induced apoptosis of several kinds of cancer cell lines, but the mechanism remain unclear. Because STAT3 (Signal Transducer and Activators of Transcription 3, STAT3) and related signaling pathways play important role in the cancer cell anti-apoptosis, proliferation, invasion, metastasis, and angiogenesis, it has become a key therapeutic target for anti-cancer drug development.In this study, we are aimed to evaluate the anti-cancer effect of extracts from Hedyotis Diffusa Willd both in vitro and in vivo, and discuss its mechanism based on STAT3 signaling pathway. HT (Total extract), HE (ethyl acetate extract), and HW (water extract) were collected in this work to study their anti-cancer activity. MTT assay indicated that HE inhibited the growth of human breast cancer cells MDA-MB-468 and prostate cancer DU145 cells. Western blotting analysis showed that HE can inhibit the constitutive STAT3 activation in both cell lines in time and dose dependent manner. Moreover, pretreatment of HE decreased IL-6 induced phosphorylation of JAK2 and IL-6 induced STAT3 regulated transcription of SOCS3. In addition, results from Western blotting and immunocytochemistry showed that HE blocked both IL-6 induced and constitutive STAT3 nuclear translocation. These results indicated that HE might inhibit activation of STAT3 signaling by inactivating phosphorylation of JAK2. We further found that HE induced apoptosis of STAT3 dependent cancer cells, as evidenced by MTT assay and Hochest staining. Meantime, cleavage of PARP was significantly increased. It was also observed that cell cycle was arrested at G2/M, and c-myc and cyclin Dl were down-regulated by HE, while p21 was up-regulated. Finally, HE inhibited growth of breast tumor in BALB/c-4T1 mouse model and downregulation of STAT3 phosphorylation was also observed in tumor tissue anylsis by western blotting.In summary, this work demonstrated HE, one of the extracts of Hedyotis Diffusa Willd, can induce apoptosis of cancer cells by inhibiting the activation of STAT3 signaling pathway and downregulating related gene expression involved in cancer cell survival. We also found that it showed significant anticaner effect in vivo. Accordingly, our work studied the mechanism underlying the anti-cancer activity of Hedyotis Diffusa Willd and provided insights and research evidences to further investigate its drug targets.