title: Concomitant inactivation of the p53- and pRB- functional pathways predicts resistance to DNA damaging drugs in breast cancer in vivo.
abstract: Chemoresistance is the main obstacle to cancer cure. Contrasting studies focusing on single gene mutations, we hypothesize chemoresistance to be due to inactivation of key pathways affecting cellular mechanisms such as apoptosis, senescence, or DNA repair. In support of this hypothesis, we have previously shown inactivation of either TP53 or its key activators CHK2 and ATM to predict resistance to DNA damaging drugs in breast cancer better than TP53 mutations alone. Further, we hypothesized that redundant pathway(s) may compensate for loss of p53-pathway signaling and that these are inactivated as well in resistant tumour cells. Here, we assessed genetic alterations of the retinoblastoma gene (RB1) and its key regulators: Cyclin D and E as well as their inhibitors p16 and p27. In an exploratory cohort of 69 patients selected from two prospective studies treated with either doxorubicin monotherapy or 5-FU and mitomycin for locally advanced breast cancers, we found defects in the pRB-pathway to be associated with therapy resistance (p-values ranging from 0.001 to 0.094, depending on the cut-off value applied to p27 expression levels). Although statistically weaker, we observed confirmatory associations in a validation cohort from another prospective study (n = 107 patients treated with neoadjuvant epirubicin monotherapy; p-values ranging from 7.0 × 10(-4) to 0.001 in the combined data sets). Importantly, inactivation of the p53-and the pRB-pathways in concert predicted resistance to therapy more strongly than each of the two pathways assessed individually (exploratory cohort: p-values ranging from 3.9 × 10(-6) to 7.5 × 10(-3) depending on cut-off values applied to ATM and p27 mRNA expression levels). Again, similar findings were confirmed in the validation cohort, with p-values ranging from 6.0 × 10(-7) to 6.5 × 10(-5) in the combined data sets. Our findings strongly indicate that concomitant inactivation of the p53- and pRB- pathways predict resistance towards anthracyclines and mitomycin in breast cancer in vivo.
authors.affiliation: Section of Oncology, Department of Clinical Science, University of Bergen, Norway; Department of Oncology, Haukeland University Hospital, Bergen, Norway. Electronic address: stian.knappskog@k2.uib.no.
authors.forename: Stian
authors.initials: S
authors.lastname: Knappskog
authors.affiliation: Section of Oncology, Department of Clinical Science, University of Bergen, Norway; Department of Oncology, Haukeland University Hospital, Bergen, Norway.
authors.forename: Elisabet O
authors.initials: EO
authors.lastname: Berge
authors.affiliation: Section of Oncology, Department of Clinical Science, University of Bergen, Norway; Department of Oncology, Haukeland University Hospital, Bergen, Norway.
authors.forename: Ranjan
authors.initials: R
authors.lastname: Chrisanthar
authors.affiliation: Section of Oncology, Department of Clinical Science, University of Bergen, Norway; Department of Oncology, Haukeland University Hospital, Bergen, Norway.
authors.forename: Stephanie
authors.initials: S
authors.lastname: Geisler
authors.affiliation: Section of Oncology, Department of Clinical Science, University of Bergen, Norway; Department of Oncology, Haukeland University Hospital, Bergen, Norway.
authors.forename: Vidar
authors.initials: V
authors.lastname: Staalesen
authors.affiliation: Section of Oncology, Department of Clinical Science, University of Bergen, Norway; Department of Oncology, Haukeland University Hospital, Bergen, Norway.
authors.forename: Beryl
authors.initials: B
authors.lastname: Leirvaag
authors.affiliation: Section of Oncology, Department of Clinical Science, University of Bergen, Norway; Department of Oncology, Haukeland University Hospital, Bergen, Norway.
authors.forename: Synnøve
authors.initials: S
authors.lastname: Yndestad
authors.affiliation: Section of Oncology, Department of Clinical Science, University of Bergen, Norway; Department of Oncology, Haukeland University Hospital, Bergen, Norway.
authors.forename: Elise
authors.initials: E
authors.lastname: de Faveri
authors.affiliation: Department of Oncology, Haukeland University Hospital, Bergen, Norway.
authors.forename: Bård O
authors.initials: BO
authors.lastname: Karlsen
authors.affiliation: Wellcome Trust Sanger Institute, Hinxton, Cambridgeshire, UK.
authors.forename: David C
authors.initials: DC
authors.lastname: Wedge
authors.affiliation: Centre for Cancer Biomarkers (CCBIO), Department of Clinical Medicine, University of Bergen, Norway; Department of Pathology, Haukeland University Hospital, Bergen, Norway.
authors.forename: Lars A
authors.initials: LA
authors.lastname: Akslen
authors.affiliation: Department of Pathology, Haukeland University Hospital, Bergen, Norway; The Gade Laboratory for Pathology, Department of Clinical Medicine, University of Bergen, Norway.
authors.forename: Peer K
authors.initials: PK
authors.lastname: Lilleng
authors.affiliation: Department of Oncology, Oslo University Hospital, The Norwegian Radium Hospital, Oslo, Norway.
authors.forename: Erik
authors.initials: E
authors.lastname: Løkkevik
authors.affiliation: Department of Oncology, St. Olavs University Hospital, Trondheim, Norway; Department of Cancer Research and Molecular Medicine, Norwegian University of Science and Technology, Trondheim, Norway.
authors.forename: Steinar
authors.initials: S
authors.lastname: Lundgren
authors.affiliation: Department of Oncology, Oslo University Hospital, Ullevaal, Oslo, Norway.
authors.forename: Bjørn
authors.initials: B
authors.lastname: Østenstad
authors.affiliation: Department of Oncology, University Hospital of Northern Norway and Institute of Clinical Medicine, University of Tromsø, Tromsø, Norway.
authors.forename: Terje
authors.initials: T
authors.lastname: Risberg
authors.affiliation: Division of Hematology and Oncology, Stavanger University Hospital, Stavanger, Norway.
authors.forename: Ingvild
authors.initials: I
authors.lastname: Mjaaland
authors.affiliation: Department of Surgery, Haukeland University Hospital, Bergen, Norway.
authors.forename: Turid
authors.initials: T
authors.lastname: Aas
authors.affiliation: Section of Oncology, Department of Clinical Science, University of Bergen, Norway; Department of Oncology, Haukeland University Hospital, Bergen, Norway.
authors.forename: Per E
authors.initials: PE
authors.lastname: Lønning
mesh_terms: D000903:Antibiotics, Antineoplastic / Q000627:therapeutic use*; D001943:Breast Neoplasms / Q000175:diagnosis* / Q000235:genetics*; D015331:Cohort Studies; D004249:DNA Damage / Q000235:genetics; D004252:DNA Mutational Analysis; D004317:Doxorubicin / Q000627:therapeutic use; D019008:Drug Resistance, Neoplasm / Q000235:genetics*; D005260:Female; D005472:Fluorouracil / Q000627:therapeutic use; D015972:Gene Expression Regulation, Neoplastic; D020868:Gene Silencing; D006801:Humans; D016685:Mitomycin / Q000627:therapeutic use; D011379:Prognosis; D016160:Retinoblastoma Protein / Q000235:genetics* / Q000378:metabolism; D015398:Signal Transduction / Q000235:genetics; D017211:Treatment Failure; D016159:Tumor Suppressor Protein p53 / Q000235:genetics*
chemical_list: D000903:Antibiotics, Antineoplastic; D016160:Retinoblastoma Protein; C495901:TP53 protein, human; D016159:Tumor Suppressor Protein p53; D016685:Mitomycin; D004317:Doxorubicin; D005472:Fluorouracil
keywords: Breast cancer; Resistance; p53; pRB