S100A4 protein is down-regulated by relaxin. The 10 kDa S100A4 protein was detected by Western blot analysis in cellular extracts of MDA-MB-231 cells, MDA/EGFP and MDA/RLN2 transfectants. (a) All MDA/RLN2 transfectants contained negligible levels of S100A4 protein when compared with MDA-MB-231 or MDA/EGFP vector controls. (b) In T47D cells, S100A4 protein was also down-regulated following 48 hour and 72 hour exposure to 100 ng/ml or 500 ng/ml rhRLN2. Beta-actin detection was used to control for equal protein loading of the gels.