Bear Bile Powder Inhibits Growth of Hepatocellular Carcinoma via Suppressing STAT3 Signaling Pathway in Mice

Abstract

Objective: To evaluate the inhibitory effect of bear bile powder (BBP) on hepatocellular carcinoma (HCC) growth in vivo and investigate the underlying mechanisms.

Methods: A HCC xenograft mouse model was developed by producing with huh7 cells. After 5 days following xenograft implantation, ten HCC xenograft mice were given intra-gastric administration with 10 mg/(kg•d) dose of BBP or saline for 3 weeks. Tumor growth in HCC xenograft mice was evaluated by measuring the tumor weight and volume. Cell apoptosis, proliferation or tumor angiogenesis were examined via immunohistochemical (IHC) staining for transferase-mediated deoxyuridine triphosphate-biotin nick end labeling (TUNEL), proliferating cell nuclear antigen (PCNA) or cluster of differentiation 31 (CD31), respectively. Phosphorylation of signal transducer and activator of transcription 3 (STAT3) were determined by Western blot. The mRNA and protein expressions of Bcl-2, Bax, Cyclin D1 and Cyclin-dependent kinase 4 (CDK4) in HCC tumor tissues were respectively determined by reverse transcription polymerase chain reaction (RT-PCR) and Western blot. The protein expression of vascular endothelial growth factor A (VEGF-A) in tumor tissues was examined by IHC staining.

Results: BBP treatment led to a significant decrease on tumor volume and tumor weight in HCC mice (P<0.05) and had no effect on the change of body weight. In addition, BBP profoundly promoted cell apoptosis, inhibited cell proliferation and intratumoral microvessel density in HCC tumor tissues (P<0.05). Moreover, BBP treatment remarkably suppressed the STAT3 phosphorylation and modulated the expression of critical target genes including Bcl-2, Bax, Cyclin D1, CDK4 and VEGF-A in HCC mice.

Conclusion: BBP exerts its anti-cancer activities via suppressing STAT3 signaling pathway and affecting multiple intracellular targets.

Keywords: Chinese medicine; bear bile powder; hepatocellular carcinoma; signal transducer and activator of transcription 3 pathway.