CXCL8 and Familial prostate cancer: As we have previously seen for other types of senescent cancer cells [31], a high level of many secreted SASP factors including IL-6 and IL-8 was detected in the conditioned media of irradiated PC-3 cells by multiplex assay, suggesting that the low-level SASP observed in LNCaP cells is not related to prostate cancer in general (Figure S2F).