Remarkably, Swami et al. showed that the expression of cathepsin L, whose activity is inhibited by cystatin D, is downregulated by 1,25(OH)2D3 in breast cancer cells [68], while Zhang et al. described that silencing of cathepsin L suppresses the cell invasion and migration, the actin cytoskeleton remodeling, and the increase in SNAIL1 expression associated with TGF-β-promoted EMT in breast and lung cancer cells [83]. This evidence concerns the gene SNAI1 and breast cancer.