title: Proteomic analysis of the transitional endoplasmic reticulum in hepatocellular carcinoma: an organelle perspective on cancer.
abstract: The transitional endoplasmic reticulum (tER) is composed of both rough and smooth ER membranes and thus participates in functions attributed to both these two subcellular compartments. In this paper we have compared the protein composition of tER isolated from dissected liver tumor nodules of aflatoxin B1-treated rats with that of tER from control liver. Tandem mass spectrometry (MS), peptide counts and immunoblot validation were used to identify and determine the relative expression level of proteins. Inhibitors of apoptosis (i.e. PGRMC1, tripeptidyl peptidase II), proteins involved in ribosome biogenesis (i.e. nucleophosmin, nucleolin), proteins involved in translation (i.e. eEF-2, and subunits of eIF-3), proteins involved in ubiquitin metabolism (i.e. proteasome subunits, USP10) and proteins involved in membrane traffic (i.e. SEC13-like 1, SEC23B, dynactin 1) were found overexpressed in tumor tER. Transcription factors (i.e. Pur-beta, BTF3) and molecular targets for C-Myc and NF-kappa B were observed overexpressed in tER from tumor nodules. Down-regulated proteins included cytochrome P450 proteins and enzymes involved in fatty acid metabolism and in steroid metabolism. Unexpectedly expression of the protein folding machinery (i.e. calreticulin) and proteins of the MHC class I peptide-loading complex did not change. Proteins of unknown function were detected in association with the tER and the novel proteins showing differential expression are potential new tumor markers. In many cases differential expression of proteins in tumor tER was comparable to that of corresponding genes reported in the Oncomine human database. Thus the molecular profile of tumor tER is different and this may confer survival advantage to tumor cells in cancer.
authors.affiliation: McGill University and Genome Quebec Innovation Centre, Proteomics Services, Genome Quebec, Montreal, Quebec, Canada.
authors.forename: Line
authors.initials: L
authors.lastname: Roy
authors.forename: Sylvie
authors.initials: S
authors.lastname: Laboissière
authors.forename: Eman
authors.initials: E
authors.lastname: Abdou
authors.forename: Geneviève
authors.initials: G
authors.lastname: Thibault
authors.forename: Nathalie
authors.initials: N
authors.lastname: Hamel
authors.forename: Maryam
authors.initials: M
authors.lastname: Taheri
authors.forename: Daniel
authors.initials: D
authors.lastname: Boismenu
authors.forename: Joël
authors.initials: J
authors.lastname: Lanoix
authors.forename: Robert E
authors.initials: RE
authors.lastname: Kearney
authors.forename: Jacques
authors.initials: J
authors.lastname: Paiement
mesh_terms: D016604:Aflatoxin B1 / Q000633:toxicity; D000818:Animals; D014408:Biomarkers, Tumor / Q000378:metabolism*; D006528:Carcinoma, Hepatocellular / Q000139:chemically induced / Q000378:metabolism*; D004721:Endoplasmic Reticulum / Q000378:metabolism* / Q000648:ultrastructure; D006801:Humans; D008113:Liver Neoplasms / Q000139:chemically induced / Q000378:metabolism*; D008297:Male; D015388:Organelles / Q000378:metabolism*; D011042:Poisons / Q000633:toxicity; D020543:Proteome / Q000032:analysis*; D051381:Rats; D011916:Rats, Inbred F344; D053719:Tandem Mass Spectrometry
chemical_list: D014408:Biomarkers, Tumor; D011042:Poisons; D020543:Proteome; D016604:Aflatoxin B1