title: Clitocine reversal of P-glycoprotein associated multi-drug resistance through down-regulation of transcription factor NF-κB in R-HepG2 cell line.
abstract: Multidrug resistance (MDR) is one of the major reasons for failure in cancer chemotherapy and its suppression may increase the efficacy of therapy. The human multidrug resistance 1 (MDR1) gene encodes the plasma membrane P-glycoprotein (P-gp) that pumps various anti-cancer agents out of the cancer cell. R-HepG2 and MES-SA/Dx5 cells are doxorubicin induced P-gp over-expressed MDR sublines of human hepatocellular carcinoma HepG2 cells and human uterine carcinoma MES-SA cells respectively. Herein, we observed that clitocine, a natural compound extracted from Leucopaxillus giganteus, presented similar cytotoxicity in multidrug resistant cell lines compared with their parental cell lines and significantly suppressed the expression of P-gp in R-HepG2 and MES-SA/Dx5 cells. Further study showed that the clitocine increased the sensitivity and intracellular accumulation of doxorubicin in R-HepG2 cells accompanying down-regulated MDR1 mRNA level and promoter activity, indicating the reversal effect of MDR by clitocine. A 5'-serial truncation analysis of the MDR1 promoter defined a region from position -450 to -193 to be critical for clitocine suppression of MDR1. Mutation of a consensus NF-κB binding site in the defined region and overexpression of NF-κB p65 could offset the suppression effect of clitocine on MDR1 promoter. By immunohistochemistry, clitocine was confirmed to suppress the protein levels of both P-gp and NF-κB p65 in R-HepG2 cells and tumors. Clitocine also inhibited the expression of NF-κB p65 in MES-SA/Dx5. More importantly, clitocine could suppress the NF-κB activation even in presence of doxorubicin. Taken together; our results suggested that clitocine could reverse P-gp associated MDR via down-regulation of NF-κB.
authors.affiliation: Zhejiang University, Research Centre of Siyuan Natural Pharmacy and Biotoxicology, College of Life Sciences, Zijinggang Campus, Hangzhou, People's Republic of China.
authors.forename: Jianguo
authors.initials: J
authors.lastname: Sun
authors.forename: Chilam Au
authors.initials: CA
authors.lastname: Yeung
authors.forename: Ngai Na
authors.initials: NN
authors.lastname: Co
authors.forename: Tsun Yee
authors.initials: TY
authors.lastname: Tsang
authors.forename: Esmond
authors.initials: E
authors.lastname: Yau
authors.forename: Kewang
authors.initials: K
authors.lastname: Luo
authors.forename: Ping
authors.initials: P
authors.lastname: Wu
authors.forename: Judy Chan Yuet
authors.initials: JC
authors.lastname: Wa
authors.forename: Kwok-Pui
authors.initials: KP
authors.lastname: Fung
authors.forename: Tim-Tak
authors.initials: TT
authors.lastname: Kwok
authors.forename: Feiyan
authors.initials: F
authors.lastname: Liu
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000235:genetics / Q000378:metabolism*; D000970:Antineoplastic Agents / Q000494:pharmacology*; D049109:Cell Proliferation / Q000187:drug effects; D015536:Down-Regulation / Q000187:drug effects*; D018432:Drug Resistance, Multiple / Q000187:drug effects* / Q000235:genetics; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D056945:Hep G2 Cells; D006801:Humans; D011401:Promoter Regions, Genetic / Q000187:drug effects / Q000235:genetics; D011741:Pyrimidine Nucleosides / Q000494:pharmacology*; D051996:Transcription Factor RelA / Q000235:genetics*; D051636:X-Linked Inhibitor of Apoptosis Protein / Q000235:genetics
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D000970:Antineoplastic Agents; D011741:Pyrimidine Nucleosides; D051996:Transcription Factor RelA; D051636:X-Linked Inhibitor of Apoptosis Protein; C055433:clitocine