To test whether XIAP is involved in the inhibition of endogenous and apoptosome-generated caspase activity in cytosol from NSCLC tumours we used the heptapeptides AVPIAQK (P1) and ATPFQEG (P2) to neutralize the XIAP inhibitory action against the caspases (38,46). This evidence concerns the gene XIAP and non-small cell lung carcinoma.