Our results demonstrate that progression to this chemoresistant relapse is characterized by increased expression of MMP-9, as well as cathepsins S, X/Z/P, D and decreased expression of cathepsin V. In order to study protease expression by locally invasive tumor cells, we employed cell lines NCI-H526 and SCLC26A, representing a bone metastasis and a local pleural metastasis, respectively. This evidence concerns the gene CTSS and neoplasm.