MMP9 and cancer: Although we have not directly determined whether SM22α dampens activation of fibroblasts, it is reasonable to consider that elevated levels might contribute to the smaller tumors in the CD248CyD/CyD mice by maintaining the fibroblasts in a more quiescent state and by indirectly reducing TGF-β-induced MMP-9 release, overall preventing microenvironmental changes that would facilitate cell migration and cancer progression.