4-Piperidinopiperidine-resistant lymphoma cells were resistant to dexamethasone- and A23187-induced apoptosis

4-Piperidinopiperidine is a side residue of CPT-11, a derivative of camptothecin. We have previously established a 4-piperidinopiperidine-resistant lymphoma cell line, 4-pp-R, which was co-resistant to CPT-11. We report here that this cell line is cross-resistant to dexamethasone and A23187 which induce apoptosis in parent RVC cells. Examination of apoptosis-related gene expression by RT-PCR showed that bcl-2 expression was greater in 4-pp-R than in RVC. p53, bax and bcl-xL were expressed at the same level in 4-pp-R and RVC cells. These results suggest that upregulation of bcl-2 in 4-pp-R cells is related to the resistance to CPT-11 as well as to A23187 or dexamethasone.