Effect of matrix densities on the expression of invasion- related genes. MTLn3, rat breast cancer cells were cultured in LD (1 mg/cm3) and HD (20 mg/cm3) collagen matrices and the cells were allowed to invade in the matrices for 72 h and the total RNA was used to quantify the gene expression levels by RT- qPCR. Gene expression levels were normalized to GAPDH expression and relative expression was calculated using the ΔΔCt method. A, The expression of MT1-MMP, N-WASp, fascin, cortactin and ROCK were significantly increased in HD matrix. B, ROCK activity assay and western blotting showed that HD matrix significantly increased the ROCK activity 4-folds compared to LD matrix. The experiment was repeated three times. Bars indicate the standard error from three biological triplicates. Student’s t-test show significant difference at either * p < 0.05 or ** p < 0.01.