ABSTRACT
Cholangiocarcinoma (CCA) is a highly malignant cancer of the bile duct, which has a five-year survival rate less than 5% due to a high metastasis rate and lack of therapeutic options. Although omega-3 polyunsaturated fatty acids (n-3 PUFAs) have been shown to inhibit the proliferation of CCA cells, the effects on CCA metastasis have not been previously reported. In this study, we first assessed the proliferation, migration and invasion effects of n-3 PUFA-based fish oil on human CCA cells. Then, we investigated PUFA effects on metastasis in vivo by xenografting CCA cells into zebrafish larvae that overexpress a critical n-3 PUFA synthesis gene, Δ6 fatty acid desaturase. The results indicated that n-3 PUFA-based fish oil suppresses CCA cell growth, potentially by blocking the cell cycle at G2/M phase, and it inhibits migration and invasion potential with coincident downregulation of migration-related genes. Furthermore, zebrafish endogenous n-3 PUFAs appear to suppress CCA metastasis by inhibiting the expression of twist, a key regulator of tumor metastasis. Interestingly, only long chain n-3 PUFAs could inhibit the expression of twist in CCA cells. Together, our results suggest that n-3 PUFAs, especially DHA, may inhibit proliferation and metastasis of CCA cells by inhibiting the expression of twist.
Subject(s)
Bile Duct Neoplasms/diet therapy , Cholangiocarcinoma/diet therapy , Fatty Acids, Omega-3/pharmacology , Nuclear Proteins/genetics , Twist-Related Protein 1/genetics , Animals , Animals, Genetically Modified , Bile Duct Neoplasms/pathology , Cell Cycle Checkpoints/drug effects , Cell Cycle Checkpoints/genetics , Cell Line, Tumor , Cell Movement/drug effects , Cell Movement/genetics , Cell Proliferation/drug effects , Cell Survival/drug effects , Cholangiocarcinoma/pathology , Fatty Acids, Omega-3/chemistry , Fish Oils/chemistry , Fish Oils/pharmacology , Gene Expression Regulation, Neoplastic/drug effects , Humans , Larva/drug effects , Xenograft Model Antitumor Assays , Zebrafish/geneticsABSTRACT
Cholangiocarcinoma (CCA) is increasing in incidence worldwide and is resistant to chemotherapeutic agents, making treatment of CCA a major challenge. Previous studies reported that natural sulfated polysaccharides (SPs) disrupted growth factor receptor activation in cancer cells. The present study, therefore, aimed at investigating the antiproliferation effect of sulfated galactans (SG) isolated from the red seaweed Gracilaria fisheri (G. fisheri) on CCA cell lines. Direct binding activity of SG to CCA cells, epidermal growth factor (EGF) and epidermal growth factor receptor (EGFR) were determined. The effect of SG on proliferation of CCA cells was investigated. Cell cycle analyses and expression of signaling molecules associated with proliferation were also determined. The results demonstrated that SG bound directly to EGFR. SG inhibited proliferation of various CCA cell lines by inhibiting EGFR and extracellular signal-regulated kinases (ERK) phosphorylation, and inhibited EGF-induced increased cell proliferation. Cell cycle analyses showed that SG induced cell cycle arrest at the G0/G1 phase, down-regulated cell cycle genes and proteins (cyclin-D, cyclin-E, cdk-4, cdk-2), and up-regulated the tumor suppressor protein P53 and the cyclin-dependent kinase inhibitor P21. Taken together, these data demonstrate that SG from G. fisheri inhibited proliferation of CCA cells, and its mechanism of inhibition is mediated, to some extent, by inhibitory effects on EGFR activation and EGFR/ERK signaling pathway. SG presents a potential EGFR targeted molecule, which may be further clinically developed in a combination therapy for CCA treatment.