Targeting RhoC by Way of Ribozyme Trangene in Human Breast Cancer Cells and its Impact on Cancer Invasion

BACKGROUND: Cell motility and migration are known to be regulated by the Rho family of GTPases through their effects on the actin cytoskeleton. In breast cancer studies, RhoC has been identified as a highly specific marker in detecting tumors that developed metastases. This study aims to investigate the impact of targeting RhoC in human breast cancer cells by utilising ribozyme transgene technology and to assess its effect on cancer cell invasion. METHODS: Retroviral hammerhead ribozyme transgenes, regulated by doxycycline, were designed to specifically target human RhoC mRNA. The breast cancer cell line MDA-MB-231 was transfected with either a retroviral RhoC transgene or a control retroviral transgene. Stably transfected cells were tested for their invasiveness and migratory properties in vitro. RESULTS: In vitro testing of the invasiveness of wild type, plasmid control and the RhoC knockdown cells showed that MDA-MB-231(DRHOC) cells had significantly reduced invasiveness compared with MDA-MB-231(WT) (p < 0.038 RHOC2 knockdown cells; p < 0.006 RHOC3 knockdown cells) and MDA-MB-231(pRevTRE) control plasmid cells (p < 0.07 RHOC2 knockdown cells; p < 0.002 RHOC3 knockdown cells). An even greater reduction in invasiveness of the MDA-MB-231(DRHOC) cells compared with the MDA-MB-231(WT) cells was seen in response to hepatocyte growth factor (HGF/SF) (p < 0.009 RHOC1 knockdown; p = 0.004 RHOC2 knockdown; p = 0.00007 RHOC3 knockdown). The addition of doxycycline significantly improved the effectiveness of the ribozyme transgenes (p < 0.04 for all three Rho ribozymes), but did not improve the effectiveness of these knockdown cells when treated with HGF/SF (p > 0.1 for all three ribozymes). CONCLUSIONS: This data would indicate that targeting RhoC may be an effective way to reduce the invasive potential of human breast cancer cells.