Gun Jönsson1, Staffan Paulie, Alf Grandien. 1. Department of Immunology, Wenner-Gren Institute, Stockholm University, S-106 91 Stockholm, Sweden. gun@imm2.su.se
Abstract
BACKGROUND: The Inhibitors of Apoptosis (IAPs) are negative regulators of apoptosis and their overexpression renders cells resistant to a variety of apoptotic stimuli. We investigated the mRNA expression levels of IAPs in a panel of bladder tumour cells, selected as being sensitive or resistant to death receptor-mediated apoptosis. MATERIALS AND METHODS: The mRNA expression of IAPs was quantified in a RNase protection assay (RPA). Apoptosis was induced by recombinant killerTRAIL, agonistic anti-CD95 mAbs or doxorubicin and quantified by TUNEL and MTT assays. Stable expression of cIAP-2 was obtained by retroviral transduction. RESULTS: The expression of cIAP-2 mRNA was highly correlated with resistance to TRAIL-mediated apoptosis. Overexpression of cIAP-2 conferred resistance to previously sensitive cell lines and made cells less susceptible to doxorubicin. Treatment with doxorubicin in combination with TRAIL or anti-CD95 resulted in a synergistic cytotoxic effect, which was not possible to reverse by overexpression of cIAP-2. CONCLUSION: cIAP-2 is an important regulator of apoptosis in bladder cancer and its overexpression may make tumours less susceptible to therapy involving apoptosis. The combination of immunotherapy and chemotoxic agents may represent a valid strategy to potentiate anti-tumour therapy, in particular treating tumours resisting conventional chemotherapy.
BACKGROUND: The Inhibitors of Apoptosis (IAPs) are negative regulators of apoptosis and their overexpression renders cells resistant to a variety of apoptotic stimuli. We investigated the mRNA expression levels of IAPs in a panel of bladder tumour cells, selected as being sensitive or resistant to death receptor-mediated apoptosis. MATERIALS AND METHODS: The mRNA expression of IAPs was quantified in a RNase protection assay (RPA). Apoptosis was induced by recombinant killerTRAIL, agonistic anti-CD95 mAbs or doxorubicin and quantified by TUNEL and MTT assays. Stable expression of cIAP-2 was obtained by retroviral transduction. RESULTS: The expression of cIAP-2 mRNA was highly correlated with resistance to TRAIL-mediated apoptosis. Overexpression of cIAP-2 conferred resistance to previously sensitive cell lines and made cells less susceptible to doxorubicin. Treatment with doxorubicin in combination with TRAIL or anti-CD95 resulted in a synergistic cytotoxic effect, which was not possible to reverse by overexpression of cIAP-2. CONCLUSION:cIAP-2 is an important regulator of apoptosis in bladder cancer and its overexpression may make tumours less susceptible to therapy involving apoptosis. The combination of immunotherapy and chemotoxic agents may represent a valid strategy to potentiate anti-tumour therapy, in particular treating tumours resisting conventional chemotherapy.
Authors: Rama Rathore; Jennifer E McCallum; Elizabeth Varghese; Ana-Maria Florea; Dietrich Büsselberg Journal: Apoptosis Date: 2017-07 Impact factor: 4.677