title: The p53-mediated sensitivity of cancer cells to chemotherapeutic agents is conditioned by the status of the retinoblastoma protein.
abstract: Despite the well-established function of p53 in determining cell cycle arrest and/or apoptosis in response to cytostatic/cytotoxic stresses, the role of the p53 status in the response to chemotherapeutic agents in human cancers has been not clearly defined. We wondered whether this was due to the fact that the p53-mediated response to chemotherapy drugs might be conditioned by the status of the retinoblastoma protein (pRb), a downstream factor of the pathway activated by p53 stabilization, which is frequently disrupted in cancer. The dependence of p53-mediated chemosensitivity on pRb status was first investigated in a prospective study on the prognostic relevance of p53 in breast cancer patients treated with adjuvant chemotherapy (5-fluorouracil, methotrexate and cyclophosphamide). Univariate analysis of disease-free survival (DFS) indicated that the p53 status, immunohistochemically evaluated, had no predictive value if considered independently of the pRb status. However, in patients with cancer with pRb neither lost nor hyperphosphorylated, p53 was significantly associated with the prognosis and, in a multivariate analysis of DFS including the established clinical and histopathological prognostic parameters, was found to be the only factor predicting the progression of the disease. We then studied the role of pRb status in the p53-mediated response to 5-fluorouracil and methotrexate or doxorubicin treatment in three human cancer cell lines. We found that in these cells the chemosensitivity was strictly dependent on the p53 status. However, either RB1 silencing or pRb hyperphosphorylation, caused by p16(INK4a) silencing, strongly reduced the p53-mediated response to chemotherapeutic agents. These results demonstrated that: (a) the p53-mediated response to chemotherapeutic agents induces a cytostatic/cytotoxic effect only in cancers with unaltered pRb pathway; and (b) the p53 status can actually predict the clinical outcome in this group of cancer patients.
authors.affiliation: Clinical Department of Radiological and Histopathological Sciences, University of Bologna, Via Massarenti 9, 40138 Bologna, Italy. massimo.derenzini@unibo.it
authors.forename: Massimo
authors.initials: M
authors.lastname: Derenzini
authors.forename: Elisa
authors.initials: E
authors.lastname: Brighenti
authors.forename: Giulio
authors.initials: G
authors.lastname: Donati
authors.forename: Manuela
authors.initials: M
authors.lastname: Vici
authors.forename: Claudio
authors.initials: C
authors.lastname: Ceccarelli
authors.forename: Donatella
authors.initials: D
authors.lastname: Santini
authors.forename: Mario
authors.initials: M
authors.lastname: Taffurelli
authors.forename: Lorenzo
authors.initials: L
authors.lastname: Montanaro
authors.forename: Davide
authors.initials: D
authors.lastname: Treré
mesh_terms: D000971:Antineoplastic Combined Chemotherapy Protocols / Q000627:therapeutic use*; D014408:Biomarkers, Tumor / Q000378:metabolism*; D001943:Breast Neoplasms / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D017024:Chemotherapy, Adjuvant; D004812:Epidemiologic Methods; D005260:Female; D020868:Gene Silencing; D006801:Humans; D011379:Prognosis; D016160:Retinoblastoma Protein / Q000378:metabolism / Q000502:physiology*; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000379:methods; D015398:Signal Transduction / Q000502:physiology; D014407:Tumor Cells, Cultured; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism / Q000502:physiology*
chemical_list: D014408:Biomarkers, Tumor; D016160:Retinoblastoma Protein; D016159:Tumor Suppressor Protein p53