Bruce Blumberg is a named inventor on several patents related to SXR: US 6,756,491, US 6,809,178, US 6,984,773.
Expression levels and activation of a PXR variant are directly related to drug resistance in osteosarcoma cell lines
Article first published online: 5 FEB 2007
Copyright © 2007 American Cancer Society
Volume 109, Issue 5, pages 957–965, 1 March 2007
How to Cite
Mensah-Osman, E. J., Thomas, D. G., Tabb, M. M., Larios, J. M., Hughes, D. P., Giordano, T. J., Lizyness, M. L., Rae, J. M., Blumberg, B., Hollenberg, P. F. and Baker, L. H. (2007), Expression levels and activation of a PXR variant are directly related to drug resistance in osteosarcoma cell lines. Cancer, 109: 957–965. doi: 10.1002/cncr.22479
- Issue published online: 22 FEB 2007
- Article first published online: 5 FEB 2007
- Manuscript Accepted: 30 NOV 2006
- Manuscript Revised: 27 NOV 2006
- Manuscript Received: 14 NOV 2006
- Robert and Heather Urich Research and Patient Care Fund
- Walter Cancer Institute
- University of Michigan Comprehensive Cancer Center innovation. Grant Number: P/G F004721
- Environmental Protection Agency. Grant Number: STAR-R830686
Vol. 119, Issue 5, 1115, Article first published online: 12 OCT 2012
- P450 3A4;
- drug resistance
Approximately 30% to 40% of all patients with osteosarcomas ultimately experience recurrence. The study investigated the hypothesis that the resistance of osteosarcoma to chemotherapy may be related to the expression of a pregnane xenobiotic receptor (PXR) variant protein and its role as the major inducer of P450 3A4 in these tumors.
Polymerase chain reaction (PCR) and Western blot analysis were used to determine PXR mRNA and protein expression, respectively. Real-time PCR and CYP3A catalytic activity using 7-benzyl-trifluoromethyl coumarin (BFC) as the probe substrate were used to measure the induction of P450 3A4 or MDR1. siRNA transfections were performed for PXR and cytotoxicity determined by a colorimetric based assay or Annexin v-Fitc staining.
Differences were observed in the molecular size of the PXR protein expressed in sarcoma cell lines when compared with the wildtype PXR expressed in normal liver, kidney, or small intestine. A polyclonal PXR antibody raised against the N-terminus of the wildtype PXR did not detect PXR expressed in these sarcoma cell lines. In the osteosarcoma cell lines, etoposide and doxorubicin were better inducers of P450 3A4 and MDR1 than rifampin. siRNA against PXR down-regulated P450 3A4 expression only in the osteosarcoma cell line. Cytotoxicity assays showed that the resistance of the osteosarcoma cell lines to etoposide correlated with PXR protein expression levels and activation of P450 3A4 and could be prevented by ketoconazole.
The results suggest that PXR plays a critical role in the regulation of P450 3A4 expression in osteosarcoma and that its expression and activation in these tumors may influence the effect of chemotherapeutic agents on the induction of target genes implicated in drug resistance. Cancer 2007. © 2007 American Cancer Society.