Activation of the steroid and xenobiotic receptor (human pregnane X receptor) by nontaxane microtubule-stabilizing agents

Sridhar Mani, Haiyan Huang, Sumathy Sundarababu, Wenjing Liu, Ganjam V. Kalpana, Amos B. Smith, Susan Band Horwitz

Research output: Contribution to journalArticle

60 Citations (Scopus)

Abstract

Purpose: Because induction of drug efflux transporters is one of the major underlying mechanisms of drug resistance in cancer chemotherapy, and human pregnane X receptor (hPXR) is one of the principal "xenobiotic" receptors whoseactivation induces transporterand drug-metabolizing enzyme gene transcription, it would be ideal to develop chemotherapy drugs that do not activate hPXR. This report describes studies undertaken to explore the characteristics of hPXR stimulation and mechanisms of drug-receptor interactions in vitro with new anti-tubulin drugs. Experimental Design: In vitro transient transcription, glutathione S-transferase pull-down assays, and mammalian one-hybrid and two-hybrid systems were used to explore drug-receptor interactions. Loss of righting reflex was used to assess effects of drugs on PXR activity in vivo. Results: The current study showed that paclitaxel, discodermolide, and an analogue of epothilone B, BMS-247550, induced CYP3A4 protein expression in HepG2 hepatoma cells. Transient transcription assays of a luciferase reporter in the presence and absence of a GAL4-steroid and xenobiotic receptor (SXR) plasmid in HepG2 cells showed that these drugs activate hPXR. This was not true for the inactive analogue of paclitaxel, baccatin III, or for an analogue of epothilone A, analogue 5, none of which stabilizes microtubules. To determine the mechanisms by which paclitaxel, discodermolide, and BMS-247550 activate hPXR, a mammalian two-hybrid assay was done using VP16SRC-1 (coactivator) and GAL4-SXR. SRC-1 preferentially augmented the effects of these drugs on hPXR. Expression of SMRT (corepressor) but not NCoR suppressed the drug-induced activation of SXR by ∼50%, indicating a selectivity in corepressor interaction with hPXR. These drugs resulted in shortened duration of loss of righting reflex in vivo, indicating drug-induced activation of PXR in mice. Conclusion: These findings suggest that activation of hPXR with selective displacement of corepressors is an important mechanism by which microtubule-stabilizing drugs induce drug-metabolizing enzymes both in vitro and in vivo.

Original languageEnglish (US)
Pages (from-to)6359-6369
Number of pages11
JournalClinical Cancer Research
Volume11
Issue number17
DOIs
StatePublished - Sep 1 2005

Fingerprint

Excipients
Microtubules
Pharmaceutical Preparations
Paclitaxel
Righting Reflex
Drug Receptors
Co-Repressor Proteins
Hep G2 Cells
Drug Interactions
Nuclear Receptor Co-Repressor 2
pregnane X receptor
Drug Therapy
Cytochrome P-450 CYP3A
Two-Hybrid System Techniques
Xenobiotics
Enzymes
Tubulin
Glutathione Transferase
Luciferases
Drug Resistance

ASJC Scopus subject areas

  • Cancer Research
  • Oncology

Cite this

Activation of the steroid and xenobiotic receptor (human pregnane X receptor) by nontaxane microtubule-stabilizing agents. / Mani, Sridhar; Huang, Haiyan; Sundarababu, Sumathy; Liu, Wenjing; Kalpana, Ganjam V.; Smith, Amos B.; Band Horwitz, Susan.

In: Clinical Cancer Research, Vol. 11, No. 17, 01.09.2005, p. 6359-6369.

Research output: Contribution to journalArticle

@article{6fd1880b7f0845e0a2be68eddf6d3dd2,
title = "Activation of the steroid and xenobiotic receptor (human pregnane X receptor) by nontaxane microtubule-stabilizing agents",
abstract = "Purpose: Because induction of drug efflux transporters is one of the major underlying mechanisms of drug resistance in cancer chemotherapy, and human pregnane X receptor (hPXR) is one of the principal {"}xenobiotic{"} receptors whoseactivation induces transporterand drug-metabolizing enzyme gene transcription, it would be ideal to develop chemotherapy drugs that do not activate hPXR. This report describes studies undertaken to explore the characteristics of hPXR stimulation and mechanisms of drug-receptor interactions in vitro with new anti-tubulin drugs. Experimental Design: In vitro transient transcription, glutathione S-transferase pull-down assays, and mammalian one-hybrid and two-hybrid systems were used to explore drug-receptor interactions. Loss of righting reflex was used to assess effects of drugs on PXR activity in vivo. Results: The current study showed that paclitaxel, discodermolide, and an analogue of epothilone B, BMS-247550, induced CYP3A4 protein expression in HepG2 hepatoma cells. Transient transcription assays of a luciferase reporter in the presence and absence of a GAL4-steroid and xenobiotic receptor (SXR) plasmid in HepG2 cells showed that these drugs activate hPXR. This was not true for the inactive analogue of paclitaxel, baccatin III, or for an analogue of epothilone A, analogue 5, none of which stabilizes microtubules. To determine the mechanisms by which paclitaxel, discodermolide, and BMS-247550 activate hPXR, a mammalian two-hybrid assay was done using VP16SRC-1 (coactivator) and GAL4-SXR. SRC-1 preferentially augmented the effects of these drugs on hPXR. Expression of SMRT (corepressor) but not NCoR suppressed the drug-induced activation of SXR by ∼50{\%}, indicating a selectivity in corepressor interaction with hPXR. These drugs resulted in shortened duration of loss of righting reflex in vivo, indicating drug-induced activation of PXR in mice. Conclusion: These findings suggest that activation of hPXR with selective displacement of corepressors is an important mechanism by which microtubule-stabilizing drugs induce drug-metabolizing enzymes both in vitro and in vivo.",
author = "Sridhar Mani and Haiyan Huang and Sumathy Sundarababu and Wenjing Liu and Kalpana, {Ganjam V.} and Smith, {Amos B.} and {Band Horwitz}, Susan",
year = "2005",
month = "9",
day = "1",
doi = "10.1158/1078-0432.CCR-05-0252",
language = "English (US)",
volume = "11",
pages = "6359--6369",
journal = "Clinical Cancer Research",
issn = "1078-0432",
publisher = "American Association for Cancer Research Inc.",
number = "17",

}

TY - JOUR

T1 - Activation of the steroid and xenobiotic receptor (human pregnane X receptor) by nontaxane microtubule-stabilizing agents

AU - Mani, Sridhar

AU - Huang, Haiyan

AU - Sundarababu, Sumathy

AU - Liu, Wenjing

AU - Kalpana, Ganjam V.

AU - Smith, Amos B.

AU - Band Horwitz, Susan

PY - 2005/9/1

Y1 - 2005/9/1

N2 - Purpose: Because induction of drug efflux transporters is one of the major underlying mechanisms of drug resistance in cancer chemotherapy, and human pregnane X receptor (hPXR) is one of the principal "xenobiotic" receptors whoseactivation induces transporterand drug-metabolizing enzyme gene transcription, it would be ideal to develop chemotherapy drugs that do not activate hPXR. This report describes studies undertaken to explore the characteristics of hPXR stimulation and mechanisms of drug-receptor interactions in vitro with new anti-tubulin drugs. Experimental Design: In vitro transient transcription, glutathione S-transferase pull-down assays, and mammalian one-hybrid and two-hybrid systems were used to explore drug-receptor interactions. Loss of righting reflex was used to assess effects of drugs on PXR activity in vivo. Results: The current study showed that paclitaxel, discodermolide, and an analogue of epothilone B, BMS-247550, induced CYP3A4 protein expression in HepG2 hepatoma cells. Transient transcription assays of a luciferase reporter in the presence and absence of a GAL4-steroid and xenobiotic receptor (SXR) plasmid in HepG2 cells showed that these drugs activate hPXR. This was not true for the inactive analogue of paclitaxel, baccatin III, or for an analogue of epothilone A, analogue 5, none of which stabilizes microtubules. To determine the mechanisms by which paclitaxel, discodermolide, and BMS-247550 activate hPXR, a mammalian two-hybrid assay was done using VP16SRC-1 (coactivator) and GAL4-SXR. SRC-1 preferentially augmented the effects of these drugs on hPXR. Expression of SMRT (corepressor) but not NCoR suppressed the drug-induced activation of SXR by ∼50%, indicating a selectivity in corepressor interaction with hPXR. These drugs resulted in shortened duration of loss of righting reflex in vivo, indicating drug-induced activation of PXR in mice. Conclusion: These findings suggest that activation of hPXR with selective displacement of corepressors is an important mechanism by which microtubule-stabilizing drugs induce drug-metabolizing enzymes both in vitro and in vivo.

AB - Purpose: Because induction of drug efflux transporters is one of the major underlying mechanisms of drug resistance in cancer chemotherapy, and human pregnane X receptor (hPXR) is one of the principal "xenobiotic" receptors whoseactivation induces transporterand drug-metabolizing enzyme gene transcription, it would be ideal to develop chemotherapy drugs that do not activate hPXR. This report describes studies undertaken to explore the characteristics of hPXR stimulation and mechanisms of drug-receptor interactions in vitro with new anti-tubulin drugs. Experimental Design: In vitro transient transcription, glutathione S-transferase pull-down assays, and mammalian one-hybrid and two-hybrid systems were used to explore drug-receptor interactions. Loss of righting reflex was used to assess effects of drugs on PXR activity in vivo. Results: The current study showed that paclitaxel, discodermolide, and an analogue of epothilone B, BMS-247550, induced CYP3A4 protein expression in HepG2 hepatoma cells. Transient transcription assays of a luciferase reporter in the presence and absence of a GAL4-steroid and xenobiotic receptor (SXR) plasmid in HepG2 cells showed that these drugs activate hPXR. This was not true for the inactive analogue of paclitaxel, baccatin III, or for an analogue of epothilone A, analogue 5, none of which stabilizes microtubules. To determine the mechanisms by which paclitaxel, discodermolide, and BMS-247550 activate hPXR, a mammalian two-hybrid assay was done using VP16SRC-1 (coactivator) and GAL4-SXR. SRC-1 preferentially augmented the effects of these drugs on hPXR. Expression of SMRT (corepressor) but not NCoR suppressed the drug-induced activation of SXR by ∼50%, indicating a selectivity in corepressor interaction with hPXR. These drugs resulted in shortened duration of loss of righting reflex in vivo, indicating drug-induced activation of PXR in mice. Conclusion: These findings suggest that activation of hPXR with selective displacement of corepressors is an important mechanism by which microtubule-stabilizing drugs induce drug-metabolizing enzymes both in vitro and in vivo.

UR - http://www.scopus.com/inward/record.url?scp=24344454303&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=24344454303&partnerID=8YFLogxK

U2 - 10.1158/1078-0432.CCR-05-0252

DO - 10.1158/1078-0432.CCR-05-0252

M3 - Article

VL - 11

SP - 6359

EP - 6369

JO - Clinical Cancer Research

JF - Clinical Cancer Research

SN - 1078-0432

IS - 17

ER -