Despite the ability of Smac mimetics to activate the noncanonical NF-κB pathway in ER+ breast cancer subtypes, both birinapant and CpA were more effective in activating caspases and inducing cell death in TNBC cell lines, consistent with formation of the larger complex II in TNBC cells (Figs. 1a–c and 3e). This evidence concerns the gene CPA1 and breast cancer.