Evidences have shown that the RAS signalling pathway plays an important role in colorectal cancer (CRC). Moreover, RAS-GTPase-activating proteins (RASGAPs) as RAS signalling terminators are associated with tumourigenicity and tumour progression. In this study, we used bioinformatics analysis to predict and study important miRNAs that could target RAS p21 GTPase-activating protein 1 (RASA1), an important member of RASGAPs.

The levels of RASA1 and miR-223 were analysed by real-time PCR, western blotting or in situ immunofluorescence analyses. The functional effects of miR-223 and the effects of miR-223-targeted inhibitors were examined in vivo using established assays.

Upregulation of miR-223 was detected in CRC tissues (P<0.01) and was involved in downregulation of RASA1 in CRC tissues. Furthermore, the direct inhibition of RASA1 translation by miR-223 and the activation of miR-223 by CCAAT/enhancer binding protein-β (C/EBP-β) were evaluated in CRC cells. An in vivo xenograft model of CRC suggested that the upregulation of miR-223 could promote tumour growth and that the inhibition of miR-223 might prevent solid tumour growth.

These results identify that C/EBP-β-activated miR-223 contributes to tumour growth by targeting RASA1 in CRC and miR-223-targeted inhibitors may have clinical promise for CRC treatment via suppression of miR-223.British Journal of Cancer advance online publication 31 March 2015. doi:10.1038/bjc.2015.107 www.bjcancer.com.