['Inhibition of the apoptosis cascade is an important cause of therapy resistance in diffuse large B-cell lymphomas (DLBCL). In this study, we investigated possible mechanisms and expression levels of apoptosis-related genes in the apoptosis pathway that may be responsible for differences in chemotherapy sensitivity between DLBCL patients.', 'Twenty-eight DLBCL patient samples were investigated for their expression levels of apoptosis-related genes using reverse transcription-multiplex ligation-dependent probe amplification analysis. Functional analysis of the intrinsic, caspase-9-mediated pathway was done using fluorescence-activated cell sorting analysis, Western blot analysis, and immunohistochemistry.', 'Two DLBCL groups were identified: one with low expression levels of both proapoptotic and antiapoptotic genes and one group with high expression levels of these genes. DLBCL with high expression levels of proapoptotic and antiapoptotic genes frequently seemed to be refractory to clinical chemotherapy. Functional analysis in these latter DLBCL samples and DLBCL cell lines with comparable expression profiles revealed high levels of spontaneous caspase-9 activity without induction of apoptosis, indicating disruption of the apoptosis pathway downstream of caspase-9 activation. This disruption of the apoptosis pathway could be restored using a small-molecule XIAP antagonist.'] Does inhibition of the intrinsic apoptosis pathway downstream of caspase-9 activation cause chemotherapy resistance in diffuse large B-cell lymphoma?