Down-regulation of Rab17 promotes tumourigenic properties of hepatocellular carcinoma cells via Erk pathway.

The small GTPase, Ras-related protein 17 (Rab17), a member of the Rab family, plays a critical role in the regulation of membrane traffic in polarized eukaryotic cells. However, the role of Rab17 in hepatocellular carcinoma (HCC) is not clear. Clinical speciments reveal that Rab17 was present in 15 of 20 (75.0%) paraneoplastic tissues and 7 of 20 (35.0%) HCC samples (P=0.0248). To elucidate the tumourigenic role of Rab17 in HCC, we generated two Rab17 low-expressing HCC cell lines (Hep3B and Huh-7). The results showed that Rab17 down-regulation significantly promoted the tumourigenic properties of HCC cells in vitro and in vivo, as demonstrated by enhanced cell proliferation, colony formation, invasion and migration, decreased G1 arrest, and increased tumour xenograft growth and angiogenesis. However, the enhanced tumourigenic properties of HCC cells by Rab17 down-regulation was significantly inhibited by PD980592, the inhibitor of the Erk pathway, indicating that the Erk pathway plays a critical role in Rab17 down-regulation-induced enhanced tumourigenic properties of HCC cells. Our data provide a new insight into the essential role of Rab17 in HCC carcinogenesis and suggest that Rab17 expression might be tumor suppressor gene and might provide a new interventional therapeutic target for this common malignancy.

MicroRNA-194 acts as a prognostic marker and inhibits proliferation in hepatocellular carcinoma by targeting MAP4K4.

MicroRNAs (miRNAs) play a crucial role in cancer development and progression of hepatocellular carcinoma (HCC). In this study, we aimed to analyze the role of microRNA-194 (miR-194) in HCC. We found that miR-194 expression was significantly reduced in HCC and its expression was an independent poor prognostic factor for HCC patient overall and disease-free survival rate. A significant correlation was observed between miR-194 reduction and unfavourable variables including tumor size (P = 0.0315), histologic grade (P = 0.0038), TNM stage (P = 0.0083), intrahepatic metastasis (P = 0.0184). Overexpression of miR-194 in HCC cell lines HepG2 and Hep3B inhibited cell proliferation by blocking G1-S transition and inducing apoptosis. Mitogen-activated protein kinase 4 (MAP4K4), a potential target gene of miR-194, was inversely correlated with miR-194 expression in HCC tissues and cell lines. Further studies demonstrated that miR-194 regulated the progression of HCC through directly inhibiting the expression of MAP4K4 and the restoration of MAP4K4 expression reversed the inhibitory effects of miR-194 on HCC cell proliferation. Together, our findings indicate that miR-194 may serve as a valuable prognostic marker and promising interventional therapeutic target for HCC.

Silencing of hypoxia­inducible adrenomedullin using RNA interference attenuates hepatocellular carcinoma cell growth in vivo.

Adrenomedullin (ADM) is an angiogenic peptide that has been shown to increase the risk of endometrial hyperplasia and to promote tumor cell survival following hypoxia. ADM may induce microvessel proliferation and partially decrease hypoxia in solid tumors, thus contributing to the proliferation of tumor cells, as well as tumor invasion and metastasis. However, the impact of hypoxia­induced ADM expression on hepatocellular carcinoma (HCC) cells requires further elucidation. In the present study it was found that the levels of ADM mRNA in tumor tissue from patients with HCC were significantly increased compared with the mRNA levels in adjacent non­tumorous liver tissue. Under hypoxic conditions, the mRNA and protein levels of ADM, as well as those of the cancer­promoting genes vascular endothelial growth factor and hypoxia­inducible factor 1α, were significantly elevated in a time­dependent manner in three human HCC cell lines. In addition, knockdown of ADM expression using short hairpin RNA (shRNA) in SMMC­7721 cells resulted in apoptosis that was not observed in untransfected cells. Furthermore, combined treatment with cisplatin and ADM­shRNA significantly decreased tumor growth in vivo compared with treatment with cisplatin or ADM­shRNA alone. These data demonstrate that ADM acts as a critical promoter of cell cycle progression in HCC and that the inhibition of ADM may be an effective interventional therapeutic strategy in HCC.

RNA interference targeting adrenomedullin induces apoptosis and reduces the growth of human bladder urothelial cell carcinoma.

Adrenomedullin (ADM) is a potent, long-lasting angiogenic peptide that was originally isolated from human pheochromocytoma. ADM signaling is of particular significance in endothelial cell biology because the peptide protects cells from apoptosis, and ADM has been shown to be pro-tumorigenic in that it stimulates tumor cell growth and angiogenesis. ADM may be involved in micro-vessel proliferation and partially in the release of hypoxia in solid tumors, contributing to the proliferation of tumor cells as well as local tumor invasion and metastasis. However, the effect of hypoxia-induced ADM expression in bladder cancer remains unclear. Here, we found that the levels of ADM protein in tumor tissue from patients with bladder urothelial cell carcinoma were significantly increased compared to the adjacent non-tumor bladder tissues (p < 0.01). Under hypoxic conditions, the expression of ADM was significantly elevated in a time-dependent manner in human bladder cancer cell lines. Furthermore, the knockdown of ADM by shRNA in T24 cells showed obvious apoptosis compared to untransfected controls (p < 0.0001). In addition, the combination of cisplatin and ADM-shRNA significantly reduces the tumor growth in vivo compared to treatment with cisplatin (p = 0.0046) or ADM-shRNA alone (p < 0.0001). These data suggest that ADM plays an important role in promoting bladder cancer cell growth under hypoxia and that the inhibition of ADM may provide a target for bladder cancer therapy.