title: A cytotoxic ribonuclease reduces the expression level of P-glycoprotein in multidrug-resistant cell lines.
abstract: We have previously described a cytotoxic human pancreatic-ribonuclease variant, named PE5, which is able to cleave nuclear RNA, inducing the apoptosis of cancer cells. We have investigated whether PE5 could specifically inhibit the accumulation of P-glycoprotein in multidrug-resistant cells, since P-glycoprotein overexpression is one of the most important mechanisms contributing to the multiple drug resistance phenotype. We show that PE5 is able to reduce the amount of P-glycoprotein in two different multidrug-resistant cell lines, NCI/H460-R and NCI/ADR-RES, while glutathione S-transferase-л is not affected. We also show that onconase, an amphibian ribonuclease that is undergoing phase II/III clinical trials as an antitumor drug, does not affect the expression of these proteins. The reduction of P-glycoprotein accumulation, which has been functionally confirmed by flow cytometry analysis, may be caused by the previously reported underphosphorylation of JNK induced by PE5. We also show that PE5 has synergistic cytotoxicity with doxorubicin on the NCI/ADR-RES multidrug-resistant cell line. In conclusion, PE5 is a cytotoxic ribonuclease that cleaves nuclear RNA and decreases the expression of P-glycoprotein, showing anticancer activity in multidrug-resistant cell lines.
authors.affiliation: Laboratori d'Enginyeria de Proteïnes, Departament de Biologia, Facultat de Ciències, Universitat de Girona, Campus de Montilivi, Maria Aurèlia Campmany, 69, 17071, Girona, Spain.
authors.forename: Jessica
authors.initials: J
authors.lastname: Castro
authors.forename: Marc
authors.initials: M
authors.lastname: Ribó
authors.forename: Teresa
authors.initials: T
authors.lastname: Puig
authors.forename: Ramon
authors.initials: R
authors.lastname: Colomer
authors.forename: Maria
authors.initials: M
authors.lastname: Vilanova
authors.forename: Antoni
authors.initials: A
authors.lastname: Benito
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000378:metabolism; D000970:Antineoplastic Agents / Q000494:pharmacology*; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D004317:Doxorubicin / Q000494:pharmacology; D018432:Drug Resistance, Multiple; D019008:Drug Resistance, Neoplasm; D006801:Humans; D012260:Ribonucleases / Q000494:pharmacology*
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D000970:Antineoplastic Agents; D004317:Doxorubicin; D012260:Ribonucleases