NFKB1 and invasive breast carcinoma: IL-1β is a proinflammatory cytokine and is both an activator and a target of NFκB signaling 51 Although IL-1β and TIBs are only weakly correlated in invasive breast cancer, it is possible that the initial activation of IL-1β in a small population of tumor cells by B cells may have triggered a positive feedback loop.