Katchman BA et al. reported that QSOX1 plays a role in the growth and invasion of pancreatic and breast tumor cells in vitro [18, 19, 37], The authors also demonstrated that silencing QSOX1 prevents tumor cells from invading through Matrigel due to a reduction in the proteolytic activity of MMP-2 and MMP-9. This evidence concerns the gene MMP9 and breast neoplasm.