CD40 and breast cancer: We previously established that elastase is the biologically relevant indole carbinol target protein in human breast cancer cells, and the non-competitive inhibition of elastase enzymatic activity by I3C triggers a shift from cell survival signaling to apoptotic signaling that is mediated by altered signaling through downstream elastase substrates such as the CD40 member of the tumor necrosis factor receptor gene family [33,34,48].