title: UBE2L6/UBCH8 and ISG15 attenuate autophagy in esophageal cancer cells.
abstract: Esophageal cancer remains a poor prognosis cancer due to advanced stage of presentation and drug resistant disease. To understand the molecular mechanisms influencing response to chemotherapy, we examined genes that are differentially expressed between drug sensitive, apoptosis competent esophageal cancer cells (OE21, OE33, FLO-1) and those which are more resistant and do not exhibit apoptosis (KYSE450 and OE19). Members of the ISG15 (ubiquitin-like) protein modification pathway, including UBE2L6 and ISG15, were found to be more highly expressed in the drug sensitive cell lines. In this study, we evaluated the contribution of these proteins to the response of drug sensitive cells. Depletion of UBE2L6 or ISG15 with siRNA did not influence caspase-3 activation or nuclear fragmentation following treatment with 5-fluorouracil (5-FU). We assessed autophagy by analysis of LC3II expression and Cyto-ID staining. Depletion of either ISG15 or UBE2L6 resulted in enhanced endogenous autophagic flux. An increase in autophagic flux was also observed following treatment with cytotoxic drugs (5-FU, rapamycin). In ISG15 depleted cells, this increase in autophagy was associated with improved recovery of drug treated cells. In contrast, UBE2L6 depleted cells, did not show enhanced recovery. UBE2L6 may therefore influence additional targets that limit the pro-survival effect of ISG15 depletion. These data identify UBE2L6 and ISG15 as novel inhibitors of autophagy, with the potential to influence chemosensitivity in esophageal cancer cells.
authors.affiliation: Cork Cancer Research Centre, University College Cork, Cork, Ireland.
authors.forename: Chloe M
authors.initials: CM
authors.lastname: Falvey
authors.affiliation: Cork Cancer Research Centre, University College Cork, Cork, Ireland.
authors.forename: Tracey R
authors.initials: TR
authors.lastname: O'Donovan
authors.affiliation: Cork Cancer Research Centre, University College Cork, Cork, Ireland.
authors.forename: Shereen
authors.initials: S
authors.lastname: El-Mashed
authors.affiliation: Cork Cancer Research Centre, University College Cork, Cork, Ireland.
authors.forename: Michelle J
authors.initials: MJ
authors.lastname: Nyhan
authors.affiliation: Department of Oncology, Cork University Hospital, Cork, Ireland.
authors.forename: Seamus
authors.initials: S
authors.lastname: O'Reilly
authors.affiliation: Cork Cancer Research Centre, University College Cork, Cork, Ireland.
authors.forename: Sharon L
authors.initials: SL
authors.lastname: McKenna
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects / Q000235:genetics; D001343:Autophagy / Q000187:drug effects / Q000235:genetics*; D015153:Blotting, Western; D053148:Caspase 3 / Q000378:metabolism; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects / Q000235:genetics; D016207:Cytokines / Q000235:genetics* / Q000378:metabolism; D019008:Drug Resistance, Neoplasm / Q000187:drug effects / Q000235:genetics*; D004938:Esophageal Neoplasms / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D005472:Fluorouracil / Q000494:pharmacology; D020869:Gene Expression Profiling / Q000379:methods; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D008869:Microtubule-Associated Proteins / Q000378:metabolism; D034622:RNA Interference; D015398:Signal Transduction / Q000187:drug effects / Q000235:genetics; D044763:Ubiquitin-Conjugating Enzymes / Q000235:genetics* / Q000378:metabolism; D014452:Ubiquitins / Q000235:genetics* / Q000378:metabolism
chemical_list: D000970:Antineoplastic Agents; D016207:Cytokines; C477012:MAP1LC3A protein, human; D008869:Microtubule-Associated Proteins; D014452:Ubiquitins; C074034:ISG15 protein, human; C471622:UBE2L6 protein, human; D044763:Ubiquitin-Conjugating Enzymes; D053148:Caspase 3; D005472:Fluorouracil
keywords: ISG15; UBE2L6; apoptosis; autophagy; esophageal