title: A structure-function relationship among reserpine and yohimbine analogues in their ability to increase expression of mdr1 and P-glycoprotein in a human colon carcinoma cell line.
abstract: We previously showed that there is a structure-function relationship among reserpine and yohimbine analogues in their ability to inhibit the function of P-glycoprotein (P-gp) and reverse multidrug resistance (MDR). Because some P-gp inhibitors (e.g., verapamil and nifedipine) can increase mdr1 and P-gp expression in human colon carcinoma cell lines, we used our reserpine/yohimbine analogues to determine whether there was a structural requirement for this induction. We found that 10 microM reserpine increased both mdr1 and P-gp expression by 4-10-fold in 48 hr in a human colon carcinoma cell line that expresses moderate levels of mdr1 (LS180-Ad50) but not in several other cell lines that expressed no mdr1. The reserpine/yohimbine analogues rescinnamine, trimethoxybenzoylyohimbine, and LY191401 (compound G), all of which contain the three structural elements used to describe the MDR pharmacophore, also increased both mdr1 and P-gp expression significantly. Despite some exceptions, we found that there was a good association between the ability of these analogues to induce mdr1 and P-gp expression and their ability to reverse vinblastine and doxorubicin resistance, revealing a structure-function relationship for this phenomenon. The increased P-gp expressed by these cells appeared to be functional, as determined by flow cytometric detection of rhodamine 123 retention. The increased expression was suppressed by 5,6-dichloro-1-beta-D-ribofuranosylbenzimidazole, an RNA synthesis inhibitor, whereas the protein synthesis inhibitor cycloheximide enhanced the expression several-fold, suggesting that induction of mdr1 by these analogues is regulated at both the transcriptional and post-transcriptional levels.(ABSTRACT TRUNCATED AT 250 WORDS)
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000096:biosynthesis / Q000235:genetics* / Q000502:physiology; D000903:Antibiotics, Antineoplastic / Q000494:pharmacology; D000972:Antineoplastic Agents, Phytogenic / Q000494:pharmacology; D003110:Colonic Neoplasms / Q000188:drug therapy* / Q000235:genetics / Q000378:metabolism; D004317:Doxorubicin / Q000494:pharmacology; D018432:Drug Resistance, Multiple / Q000235:genetics*; D019008:Drug Resistance, Neoplasm / Q000235:genetics*; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D006801:Humans; D009363:Neoplasm Proteins / Q000096:biosynthesis; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D012334:RNA, Neoplasm / Q000096:biosynthesis; D012110:Reserpine / Q000031:analogs & derivatives* / Q000737:chemistry / Q000494:pharmacology; D013329:Structure-Activity Relationship; D014407:Tumor Cells, Cultured; D014747:Vinblastine / Q000494:pharmacology; D015016:Yohimbine / Q000031:analogs & derivatives* / Q000737:chemistry / Q000494:pharmacology
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D000903:Antibiotics, Antineoplastic; D000972:Antineoplastic Agents, Phytogenic; D009363:Neoplasm Proteins; D011500:Protein Synthesis Inhibitors; D012334:RNA, Neoplasm; D015016:Yohimbine; D014747:Vinblastine; D004317:Doxorubicin; D012110:Reserpine