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