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Acquired TRAIL resistance in human breast cancer cells are caused by the sustained cFLIP(L) and XIAP protein levels and ERK activation.

Lee TJ, Lee JT, Park JW, Kwon TK

Department of Immunology, School of Medicine, Keimyung University, 194 DongSan-Dong Jung-Gu, Taegu 700-712, Republic of Korea.

We established TRAIL-resistant MDA-231/TR cells from MDA-231 parent cells to understand the mechanism of TRAIL resistance in breast cancer cells. The selected TRAIL-resistant cells were cross-resistant to TNF-alpha/cycloheximide but remained sensitive to DNA-damage drugs such as oxaliplatin and etoposide. The expression levels of death receptors (DR4 and DR5), FADD, cIAP1, cIAP2, and Bcl-2 family were not changed in TRAIL-treated both cells. Significant down-regulation of XIAP and cFLIP was occurred after TRAIL treatment in MDA-231 cells whereas their levels were sustained in MDA-231/TR cells. TRAIL-mediated activation of ERK and JNK were also observed in parent MDA-231 cells but not in MDA-231/TR cells. However, TRAIL-resistant cells showed constitutive activation state after treatment with TRAIL. Pretreatment with PD98059 or transfection of MKK1-DN (dominant negative) expression vector attenuated TRAIL resistance in MDA-231/TR cells. Our findings provide the evidence that the sustained expression level of cFLIP(L) and XIAP protein and constitutive ERK activation may lead to acquired TRAIL resistance in breast cancer cells.

Published 19 November 2006 in Biochem Biophys Res Commun, 351(4): 1024-30.
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