Updated project metadata. Stat3 has been acknowledged as an oncogene that has dual protumorigenic activity in a cell-intrinsic way, by promoting cancer cell proliferation and survival and in a paracrine mode, acting as suppressor of immune cell attack. We demonstrated that Stat3 silencing with a small interfering RNA (siRNA) induced a senescence program in Stat3-addicted cancer cells and leads to the production of a senescence associated secretory phenotype (SASP) that has several antitumor properties. The composition of the SASP induced by Stat3 silencing is poorly characterized. The goal of the project was to analyze the protein content in the secretome released by the mouse breast cancer cell line 4T1 after Stat3 silencing with a small interfering RNA.