CDKN1A and neoplasm: Immunohistochemical analysis of the treated tumors showed how Gemcitabine induces a robust senescent response in the tumor as observed from the positive senescence-associated beta-galactosidase (SABG) staining, the loss of proliferation marker Ki67, and the expression of cell cycle inhibitor p21 (Fig. 4d, e), all of them markers of cell senescence41.