MMP9 and infection: The results of this study demonstrated a moderate increase in the expression of fibronectin protein in B. burgdorferi infected MCF 10A cells, but there was a detectable increase in the expression level of fibronectin, vimentin, and Twist1/2 protein and a statistically significant increase in activated MMP9 level at 72 h post B. burgdorferi infection in the MDA-MB-231 cells.