BACKGROUND: One of the major problems in the cure of advanced non-small-cell lung cancer (NSCLC) is its lack of response to cytotoxic drug treatment, and the mechanisms underlying this intrinsic drug resistance are unclear. PATIENTS AND METHODS: We determined the expression of a newly recognised drug resistance gene, the Multidrug Resistance-associated Protein (MRP) gene, in normal lung tissue and in tumour biopsies from 35 surgically resected NSCLCs (11 adenocarcinomas, 24 squamous cell carcinomas). MRP mRNA levels were quantitated by RNase protection assay and expression of the MRP Mr 190,000 glycoprotein was estimated by immunohistochemistry. RESULTS: Using the MRP-specific monoclonal antibody MRPr1, MRP expression was detected by immunohistochemistry in epithelial cells lining the bronchi in normal lung. In NSCLC approximately 35% of the samples showed elevated MRP mRNA levels. Based on MRP-specific immunohistochemical staining the tumours were divided into 4 groups: 12% were scored as negative (-), 14% showed weak cytoplasmic staining of the tumour cells (+/-), 40% had a clear cytoplasmic staining (+), and in 34% a strong cytoplasmic as well as membranous staining was observed (++). MRP expression, as estimated by immunohistochemistry, correlated with the MRP mRNA levels quantitated by RNase protection assay (correlation coefficient = 0.745, p = 0.0009), with MRP mRNA levels (mean +/- SD) of 3.0 +/- 1.0 U, 3.5 +/- 0.7 U, 7.5 +/- 5.9 U, and 19.3 +/- 10.7 U, in the (-), (+/-), (+), and (++) immunohistochemistry expression groups, respectively. Among the squamous cell carcinomas a correlation was observed between MRP staining and tumour cell differentiation: the strongest MRP staining was predominantly found in the well differentiated tumours. CONCLUSIONS: Hyperexpression of MRP is frequently observed in primary NSCLC, especially in the well differentiated squamous cell carcinomas. Further studies are needed to assess the role of MRP in the mechanism of clinical drug resistance in NSCLC.
BACKGROUND: One of the major problems in the cure of advanced non-small-cell lung cancer (NSCLC) is its lack of response to cytotoxic drug treatment, and the mechanisms underlying this intrinsic drug resistance are unclear. PATIENTS AND METHODS: We determined the expression of a newly recognised drug resistance gene, the Multidrug Resistance-associated Protein (MRP) gene, in normal lung tissue and in tumour biopsies from 35 surgically resected NSCLCs (11 adenocarcinomas, 24 squamous cell carcinomas). MRP mRNA levels were quantitated by RNase protection assay and expression of the MRP Mr 190,000 glycoprotein was estimated by immunohistochemistry. RESULTS: Using the MRP-specific monoclonal antibody MRPr1, MRP expression was detected by immunohistochemistry in epithelial cells lining the bronchi in normal lung. In NSCLC approximately 35% of the samples showed elevated MRP mRNA levels. Based on MRP-specific immunohistochemical staining the tumours were divided into 4 groups: 12% were scored as negative (-), 14% showed weak cytoplasmic staining of the tumour cells (+/-), 40% had a clear cytoplasmic staining (+), and in 34% a strong cytoplasmic as well as membranous staining was observed (++). MRP expression, as estimated by immunohistochemistry, correlated with the MRP mRNA levels quantitated by RNase protection assay (correlation coefficient = 0.745, p = 0.0009), with MRP mRNA levels (mean +/- SD) of 3.0 +/- 1.0 U, 3.5 +/- 0.7 U, 7.5 +/- 5.9 U, and 19.3 +/- 10.7 U, in the (-), (+/-), (+), and (++) immunohistochemistry expression groups, respectively. Among the squamous cell carcinomas a correlation was observed between MRP staining and tumour cell differentiation: the strongest MRP staining was predominantly found in the well differentiated tumours. CONCLUSIONS: Hyperexpression of MRP is frequently observed in primary NSCLC, especially in the well differentiated squamous cell carcinomas. Further studies are needed to assess the role of MRP in the mechanism of clinical drug resistance in NSCLC.
Authors: G A Meijer; A B Schroeijers; M J Flens; S G Meuwissen; P van der Valk; J P Baak; R J Scheper Journal: J Clin Pathol Date: 1999-06 Impact factor: 3.411
Authors: Walter Berger; Ulrike Setinek; Peter Hollaus; Thomas Zidek; Elisabeth Steiner; L Elbling; H Cantonati; Johannes Attems; Andrea Gsur; Michael Micksche Journal: J Cancer Res Clin Oncol Date: 2005-01-27 Impact factor: 4.553
Authors: Robert W Robey; Suneet Shukla; Elizabeth M Finley; Robert K Oldham; Daryl Barnett; Suresh V Ambudkar; Tito Fojo; Susan E Bates Journal: Biochem Pharmacol Date: 2007-12-14 Impact factor: 5.858
Authors: K Nooter; G Brutel de la Riviere; M P Look; K E van Wingerden; S C Henzen-Logmans; R J Scheper; M J Flens; J G Klijn; G Stoter; J A Foekens Journal: Br J Cancer Date: 1997 Impact factor: 7.640