The present study revealed that the SMAC mimetic compound AT101 treatment down-regulated XIAP, cIAP1, and cIAP2 mRNA and protein expressions while increasing caspase-6 and caspase-7 mRNA and protein expression levels in NCI-H522 lung cancer cell line to favor total apoptosis in these cells. This evidence concerns the gene BIRC3 and lung carcinoma.