biostudies-literatureKadera BENIDDK NIH HHSNCI NIH HHS157-65https://www.ebi.ac.uk/biostudies/studies/S-EPMC4286535biostudies-literatureUnknown21(1)<h4>Purpose</h4>Expression of CBL, an ubiquitin ligase, is decreased in 60% of human pancreatic ductal adenocarcinomas (PDAC) and is associated with shorter overall survival. We sought to determine how low CBL directly contributes to clinically more aggressive PDAC.<h4>Experimental design</h4>Human PDACs were stained for CBL, pEGFR, and EGFR. CBL-low was modeled in PDAC cells (Panc-1, L3.6pl, and AsPC-1) via transient transfection (siRNA) or stable knockdown (shRNA). Cell viability and apoptosis were measured by MTT assays and FACS. Immunoblot and a phospho-receptor tyrosine kinase (pRTK) array were used to probe signal transduction. NOD-scid-IL2Rγ(null) mice were subcutaneously implanted with PDAC or PDAC(CBL-low) cells on opposite flanks and treated with gemcitabine ± erlotinib for ≥4 weeks.<h4>Results</h4>There was an inverse correlation between CBL and pEGFR protein expression in 12 of 15 tumors. CBL knockdown increased PDAC resistance to gemcitabine and 5-fluorouracil (5-FU) by upregulating pEGFR (Y1068), pERK, and pAKT. A pRTK array of PDAC(CBL-low) cells revealed additional activated tyrosine kinases but all to a much lower magnitude than EGFR. Increased chemoresistance from low CBL was abrogated by the EGFR inhibitor erlotinib both in vitro and in vivo. Erlotinib+gemcitabine-treated PDAC(CBL-low) cells exhibited greater apoptosis by cleaved PARP, caspase-3, and Annexin V/PI.<h4>Conclusions</h4>Low CBL causes chemoresistance in PDAC via stress-induced EGFR activation that can be effectively abrogated by EGFR inhibition. These results suggest that dysregulation of ubiquitination is a key mechanism of EGFR hyperactivation in PDAC and that low CBL may define PDAC tumors likely to respond to erlotinib treatment.Clinical cancer research : an official journal of the American Association for Cancer ResearchLow expression of the E3 ubiquitin ligase CBL confers chemoresistance in human pancreatic cancer and is targeted by epidermal growth factor receptor inhibition.PMC4286535P30 DK041301P30 DK41301R01 CA187678T32 DK007180Wu NKadera BEDonahue TRNguyen AHDawson DWToste PALi LfalseLow expression of the E3 ubiquitin ligase CBL confers chemoresistance in human pancreatic cancer and is targeted by epidermal growth factor receptor inhibition.<h4>Purpose</h4>Expression of CBL, an ubiquitin ligase, is decreased in 60% of human pancreatic ductal adenocarcinomas (PDAC) and is associated with shorter overall survival. We sought to determine how low CBL directly contributes to clinically more aggressive PDAC.<h4>Experimental design</h4>Human PDACs were stained for CBL, pEGFR, and EGFR. CBL-low was modeled in PDAC cells (Panc-1, L3.6pl, and AsPC-1) via transient transfection (siRNA) or stable knockdown (shRNA). Cell viability and apoptosis were measured by MTT assays and FACS. Immunoblot and a phospho-receptor tyrosine kinase (pRTK) array were used to probe signal transduction. NOD-scid-IL2Rγ(null) mice were subcutaneously implanted with PDAC or PDAC(CBL-low) cells on opposite flanks and treated with gemcitabine ± erlotinib for ≥4 weeks.<h4>Results</h4>There was an inverse correlation between CBL and pEGFR protein expression in 12 of 15 tumors. CBL knockdown increased PDAC resistance to gemcitabine and 5-fluorouracil (5-FU) by upregulating pEGFR (Y1068), pERK, and pAKT. A pRTK array of PDAC(CBL-low) cells revealed additional activated tyrosine kinases but all to a much lower magnitude than EGFR. Increased chemoresistance from low CBL was abrogated by the EGFR inhibitor erlotinib both in vitro and in vivo. Erlotinib+gemcitabine-treated PDAC(CBL-low) cells exhibited greater apoptosis by cleaved PARP, caspase-3, and Annexin V/PI.<h4>Conclusions</h4>Low CBL causes chemoresistance in PDAC via stress-induced EGFR activation that can be effectively abrogated by EGFR inhibition. These results suggest that dysregulation of ubiquitination is a key mechanism of EGFR hyperactivation in PDAC and that low CBL may define PDAC tumors likely to respond to erlotinib treatment.2015-01-01T00:00:00Z2015 Jan2026-04-29T11:15:34.146Z2019-03-27T01:42:54ZS-EPMC42865352534851510.1158/1078-0432.CCR-14-061010.1158/1078-0432.ccr-14-0610