KL and neoplasm: This peptide promoted apoptosis in tumor cells, and a chimera (smac-KLA) fusing a modified KLA peptide and an octa-peptide from the N-terminus of mature Smac protein (second mitochondrial-derived activator of caspases) exerted an anticancer synergic action by inducing apoptosis in BC cells (MDA-MB-231, MCF-7) and, in addition, favored an anti-inhibitor of apoptosis protein activity (drug resistance is caused by an upregulation of this inhibitor) [274].