title: Variable effects of sodium butyrate on the expression and function of the MDR1 (P-glycoprotein) gene in colon carcinoma cell lines.
abstract: Expression of the MDR1 (P-glycoprotein) gene confers resistance to several classes of chemotherapeutic drugs (multi-drug resistance). Colon carcinomas frequently express high levels of MDR1 mRNA and P-glycoprotein, presumably reflecting the origin of these tumors from MDR1-expressing normal colonic cells. In 4 colon carcinoma cell lines (SW 620, HCT-15, DLD-1, LS 180), MDR1 expression was reported in an earlier study to be elevated after exposure to a differentiating agent, sodium butyrate (NaB). In one of these cell lines (SW 620), increased MDR1 expression reportedly was not accompanied by a decrease in the accumulation or cytotoxicity of vinblastine, a P-glycoprotein-transported drug, suggesting a possible functional abnormality of NaB-induced P-glycoprotein. We have re-examined the effect of NaB on MDR1/P-glycoprotein expression and function in the same colon carcinoma cell lines. NaB treatment induced differentiation-related changes and increased expression of MDR1 mRNA in all 4 cell lines. A major increase in MDR1 mRNA and P-glycoprotein expression was observed in only one line, SW 620. This increase, however, was accompanied by a commensurate increase in the activity of P-glycoprotein, indicating that the induced protein was fully functional. NaB treatment caused a relatively minor increase in MDR1 mRNA expressed in the other 3 cell lines. Two of these lines showed a detectable increase in the P-glycoprotein expression and function, but in the third line (LS 180) P-glycoprotein was undetectable either before or after exposure to NaB. The magnitude of MDR1 induction by NaB showed no apparent correlation with differentiation-related changes induced by this agent.
authors.affiliation: Department of Genetics, University of Illinois at Chicago 60612-7309.
authors.forename: T O
authors.initials: TO
authors.lastname: Frommel
authors.forename: J S
authors.initials: JS
authors.lastname: Coon
authors.forename: T
authors.initials: T
authors.lastname: Tsuruo
authors.forename: I B
authors.initials: IB
authors.lastname: Roninson
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D002087:Butyrates / Q000494:pharmacology*; D020148:Butyric Acid; D002277:Carcinoma / Q000235:genetics* / Q000378:metabolism* / Q000473:pathology; D002352:Carrier Proteins / Q000187:drug effects* / Q000235:genetics; D002455:Cell Division / Q000187:drug effects; D003110:Colonic Neoplasms / Q000235:genetics* / Q000378:metabolism* / Q000473:pathology; D005434:Flow Cytometry; D015870:Gene Expression / Q000187:drug effects; D006801:Humans; D007150:Immunohistochemistry; D008562:Membrane Glycoproteins / Q000187:drug effects* / Q000235:genetics; D016133:Polymerase Chain Reaction; D012333:RNA, Messenger / Q000032:analysis; D014407:Tumor Cells, Cultured; D014747:Vinblastine / Q000494:pharmacology
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D002087:Butyrates; D002352:Carrier Proteins; D008562:Membrane Glycoproteins; D012333:RNA, Messenger; D020148:Butyric Acid; D014747:Vinblastine