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MicroRNAs (miRNAs) regulate tumor progression and invasion via direct interaction with target messenger RNAs (mRNAs). We defined miRNAs involved in cancer metastasis (metastamirs) using an established in vitro colorectal cancer (CRC) model of minimally metastatic cells (SW480 line) from a colon adenocarcinoma primary lesion and highly metastatic cells (SW620 line) from a metastatic lymph node from the same patient 1 year later. We used microarray analysis to identify miRNAs differentially expressed in SW480 and SW620 cells, focusing on miR-499-5p as a novel candidate prometastatic miRNA whose functions in cancer had not been studied. We confirmed increased miR-499-5p levels in highly invasive CRC cell lines and lymph node-positive CRC specimens. Furthermore, enhancing the expression of miR-499-5p promoted CRC cell migration and invasion in vitro and lung and liver metastasis in vivo, while silencing its expression resulted in reduced migration and invasion. Additionally, we identified FOXO4 and PDCD4 as direct and functional targets of miR-499-5p. Collectively, these findings suggested that miR-499-5p promoted metastasis of CRC cells and may be useful as a new potential therapeutic target for CRC.

Hepatocellular carcinoma (HCC) is an aggressive cancer with a poor prognosis. The specific cellular gene alterations responsible for hepatocarcinogenesis are not well known. Cytokine-induced antiapoptotic molecule (CIAPIN1), a recently reported antiapoptotic molecule which plays an essential role in mouse definitive hematopoiesis, is considered a downstream effecter of the receptor tyrosine kinase-Ras signaling pathway. However, the exact function of this gene in tumors is not clear. In this study, we reported that CIAPIN1 is highly expressed in HCC as compared with non-tumor hepatic tissue (P0.05). We employed adenovirus-mediated RNA interference technique to knock down CIAPIN1 expression in HCC cells and observed its effects on HCC cell growth in vitro and in vivo. Among the four HCC and one normal human liver cell lines we analyzed, CIAPIN1 was highly expressed in HCC cells. Knock down of CIAPIN1 could inhibit HCC cell proliferation by inhibiting the cell cycle S-phase entry. Soft agar colony formation assay indicated that the colony-forming ability of SMMC-7721 cells decreased by approximately 70% after adenovirus AdH1-small interfering RNA (siRNA)/CIAPIN1 infection. In vivo experiments showed that adenovirus AdH1-siRNA/CIAPIN1 inhibited the tumorigenicity of SMMC-7721 cells and significantly suppressed tumor growth when injected directly into tumors. These results suggest that knock down of CIAPIN1 by adenovirus-delivered siRNA may be a potential therapeutic strategy for treatment of HCC in which CIAPIN1 is overexpressed.

Previous studies by our laboratory indicated that zinc ribbon domain-containing 1 (ZNRD1) suppressed the growth of gastric cancer cells with a G(1) cell cycle arrest. However, the precise molecular mechanism underlying the growth-inhibitory effect of ZNRD1 remained fragmentary. In the present study, we have demonstrated that ZNRD1 could significantly inhibit the in vitro and in vivo growth of gastric cell line MKN28. Human cDNA microarray, reverse transcription-polymerase chain reaction and western blot analyses were used to identify differentially expressed cell cycle-related genes in MKN28 cells over-expressing ZNRD1. ZNRD1-induced growth suppression was found at least partially to regulate various proteins and signaling pathways controlling G(1) to S progression, including inhibition of cyclin D1 and CDK4, up-regulation of p21(CIP1/WAF1) and p27(Kip1) and acceleration of pRb dephosphorylation. Furthermore, ZNRD1 significantly inhibited the transcriptional activity of cyclin D1. p27(Kip1) might play a pivotal role in ZNRD1-induced cell cycle arrest because the p27(Kip1) anti-sense could block the cytostatic effects of ZNRD1. Moreover, ZNRD1 suppressed Skp2 expression via an increase in the protein instability, and induced significant decrease in cyclin E-CDK2 kinase activity. In addition, ZNRD1 could reduce tumor microvessel densities through inhibition of VEGF. Taken together, these results suggested that ZNRD1 might inhibit cell growth by targeting cell cycle-related genes and reducing tumor angiogenesis.