MCAM and breast cancer: This also was not due to the higher proliferation rate of the METCAM/MUC18-expressing clones/cell lines since we have previously shown that increased expression of METCAM/MUC18 in melanoma and prostate cancer cells did not confer a higher in vitro proliferation (growth) rate of these cells and a similar effect was also found in breast cancer cells (data not shown) [8,9].