title: Bortezomib arrests the proliferation of hepatocellular carcinoma cells HepG2 and JHH6 by differentially affecting E2F1, p21 and p27 levels.
abstract: Despite the broad anti-tumour potential of the proteasome inhibitor bortezomib, partial information is available with regard to its effects on hepatocellular carcinoma (HCC) cells. Here we studied the effects of bortezomib on two human HCC cell lines displaying a different phenotype, hepatocyte-like for HepG2 and undifferentiated for JHH6. Bortezomib induced a dose- and time-dependent increase in cell toxicity and decrease of cell viability, with JHH6 being less sensitive than HepG2. Moreover, a differential influence on major cell cycle regulatory genes was responsible for the observed decrease of S and increase of G(2)-M phase cells. In HepG2, bortezomib induced a post-transcriptional increase of cyclin E1 together with a transcriptional-mediated decrease of the transcription factor E2F1. This in turn resulted in the reduction of the hyper-phosphorylated form of pRB and in the transcriptional down-regulation of the E2F1 targets cyclin D1, cyclin A2 and CdK2 but not cyclin E1. Up-regulation of LRH1, a liver specific cyclin E1 transcription factor, accounted for the unvaried cyclin E1 mRNA levels. Additionally, bortezomib induced both transcriptional and post-translational increase of p21(waf1/cip1) and p27(kip1). In JHH6, an overall more contained variation in cell cycle mediators was observed with the reduction of E2F1, cyclin A2, LRH1 and the increase of p21(waf1/cip1) being the most evident. In conclusion, the presented data show the mechanisms regulating cell proliferation inhibition by bortezomib in two different HCC cell lines. Despite a certain phenotype-dependent effect, the potent action exerted by bortezomib makes this drug attractive for future experimentation in animal models, possibly leading to novel treatments for HCC.
authors.affiliation: Department of Life Sciences, University of Trieste, Italy.
authors.forename: Daniele
authors.initials: D
authors.lastname: Baiz
authors.forename: Gabriele
authors.initials: G
authors.lastname: Pozzato
authors.forename: Barbara
authors.initials: B
authors.lastname: Dapas
authors.forename: Rossella
authors.initials: R
authors.lastname: Farra
authors.forename: Bruna
authors.initials: B
authors.lastname: Scaggiante
authors.forename: Mario
authors.initials: M
authors.lastname: Grassi
authors.forename: Laura
authors.initials: L
authors.lastname: Uxa
authors.forename: Carlo
authors.initials: C
authors.lastname: Giansante
authors.forename: Cristina
authors.initials: C
authors.lastname: Zennaro
authors.forename: Gianfranco
authors.initials: G
authors.lastname: Guarnieri
authors.forename: Gabriele
authors.initials: G
authors.lastname: Grassi
mesh_terms: D001897:Boronic Acids / Q000494:pharmacology*; D000069286:Bortezomib; D006528:Carcinoma, Hepatocellular / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects*; D002470:Cell Survival / Q000187:drug effects; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000378:metabolism*; D050760:Cyclin-Dependent Kinase Inhibitor p27 / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D050687:E2F1 Transcription Factor / Q000378:metabolism*; D016195:G2 Phase / Q000187:drug effects; D006801:Humans; D008113:Liver Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D011719:Pyrazines / Q000494:pharmacology*; D012333:RNA, Messenger / Q000032:analysis; D016196:S Phase / Q000187:drug effects; D013997:Time Factors
chemical_list: D001897:Boronic Acids; D050759:Cyclin-Dependent Kinase Inhibitor p21; D050687:E2F1 Transcription Factor; C493753:E2F1 protein, human; D011719:Pyrazines; D012333:RNA, Messenger; D050760:Cyclin-Dependent Kinase Inhibitor p27; D000069286:Bortezomib