They are involved in three stages of tumor invasion: (1) cathepsins that migrate to the cell membrane have the ability to activate other ECM-degrading proteases, such as MMPs and uPAs; (2) cathepsins that are secreted by cancer or by immune cells in the TME can cleave (together with other proteases) the ECM or the basement membrane; and (3) cathepsins can break the interaction between cells, by cleaving the adherens junction components, such as E-cadherin [105]. This evidence concerns the gene CTSS and cancer.