The tumor suppressive role of Ctsb deficiency is, however, not solely caused by the mitotic problems described here as the frequently observed increase in Ctsb/CTSB expression in murine and human tumors stimulates tumor progression by numerous means, e.g., by supporting the increased metabolic needs of cancer cells, promoting cancer cell migration and invasion and stimulating angiogenesis10,48. Here, CTSB is linked to neoplasm.