Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.6.3.44 (P-glycoprotein)
 13,344 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We have developed a new immunoperoxidase "sandwich" staining method for amplified detection of P-glycoprotein (Pgp) that is suitable for use on formalin-fixed, paraffin-embedded (conventional) tissue sections. This was accomplished by substantially changing the procedure described by Chan (1988) so as to increase specific staining intensity and to decrease nonspecific background staining. To determine the most appropriate primary antibody for the assay, we compared the immunoreactivity of JSB-1, C494, and C219 monoclonal antibodies recognizing internal epitopes of Pgp, and MRK16 and 4E3 monoclonal antibodies recognizing external epitopes of Pgp. Paraffin sections of Pgp-positive normal human tissues (adrenal, liver, kidney, and brain), of renal tumors, and of cell pellets of sensitive and multidrug resistant human tumor cell lines (MCF-7, KB) were used for comparisons. Immunostaining was excellent with JSB-1, moderate with C494, and very weak with C219. MRK16 and 4E3 showed no reaction. Nonspecific background staining was reduced by 1) omitting immunoglobulin G from secondary antibodies; 2) decreasing the concentration of peroxidase-antiperoxidase complex; and 3) utilizing casein solution for blocking and washing. Pretreatment of sections before immunostaining was also simplified. Using JSB-1, the threshold for detection of elevated Pgp corresponded to less than two-fold relative resistance to doxorubicin. Applying this method, we found two of 26 non-small cell lung cancers were positive for Pgp, consistent with previous results of others using frozen sections. This new immunoperoxidase sandwich staining method using JSB-1 now allows reliable Pgp detection in sections of formalin-fixed, paraffin-embedded (archived) surgical specimens and small biopsy materials commonly used for diagnostic purposes.
 ...
PMID:New immunohistochemical "sandwich" staining method for mdr1 P-glycoprotein detection with JSB-1 monoclonal antibody in formalin-fixed, paraffin-embedded human tissues. 750 82

Paraffin-embedded, formalin-fixed tissue (PEFFT) specimens from a subset of breast cancer patients were analyzed by immunohistochemistry to determine whether or not the presence of P-glycoprotein identified chemotherapy resistance. Two antibodies, C219 (monoclonal) and Ab1 (polyclonal), demonstrated appropriate immunostaining. Retrospectively and prospectively, P-glycoprotein expression was determined from PEFFT of 20 breast cancer biopsies (19 patients with locally advanced or metastatic disease). Immunohistochemical staining was graded for number of positive cells (N0 to N4) and intensity (I0 to I3). The immunostaining N and I of both antibodies were similar. There was no correlation between N, (P = 0.13) or I, (P = 0.67) and chemotherapy response or between N, (P = 0.63) or I, (P = 0.89) and survival. Five patients had residual cancer at repeat biopsy after systemic chemotherapy for locally advanced disease. These specimens had similar N and I as the primary cancer. This assay accurately identifies P-glycoprotein expression in PEFFT and revealed no correlation between expression and chemotherapy response or survival.
 ...
PMID:Immunohistochemical analysis of P-glycoprotein expression in breast cancer: clinical correlations. 776 69

Prostate cancer progresses from a localized disease to a widely disseminated malignancy. Each step along this progression pathway involves multiple genetic alterations that impart a survival advantage to the tumor cell over its normal counterparts and may confer resistance to therapy. Because metastatic prostate cancer is one of the most therapy-resistant human neoplasms, we studied the expression of certain molecular determinants of drug resistance in the context of tumor progression. Paraffin-embedded formalin-fixed resected prostates were chosen based on Gleason grade and surgical stage. Immunohistochemistry was used to detect the expression of multidrug resistance protein (MRP), topoisomerase II alpha, p53, glutathione S-transferase pi, Bcl-2, and P-glycoprotein in these specimens. We found that all of the proteins were expressed in resected prostate except for P-glycoprotein. The expression of MRP, topoisomerase II alpha, p53, and Bcl-2 increased with the Gleason grade. In addition, the expression of MRP, topoisomerase II alpha, and p53 increased with the surgical stage. In contrast, the glutathione S-transferase pi and Bcl-2 expression decreased with the increasing surgical stage. Stage was the strongest indicator of protein expression. These results suggest that drug resistance gene products are expressed in prostate cancer at the time of surgical resection. Thus, although the emergence of the "pan-resistance" phenotype in prostate cancer may partly be a function of the selection pressure exerted by therapeutic interventions, certain determinants of chemoresistance may be caused by genetic changes accompanying tumorigenesis.
 ...
PMID:The expression of drug resistance gene products during the progression of human prostate cancer. 962 55

Rhabdomyosarcomas generally respond well to chemotherapy, and the residual lesions often are better differentiated than their primaries. This phenomenon may be explained by selective multidrug resistance (MDR) of differentiated tumor cell populations. We assess the role of MDR proteins in chemotherapy-induced differentiation in rhabdomyosarcomas in a clinical setting. Paraffin-embedded samples of 13 pairs of primary untreated rhabdomyosarcomas and their residual, recurrent, or metastatic lesions after chemotherapy were assessed for expression of MDR proteins, including P-glycoprotein (Pgp), multidrug resistance-associated protein (MRP-1), and lung resistance-related protein (LRP). Expression was semiquantitatively scored based on the percentage of isolated immunoreactive tumor cells as follows: 0, negative; 0.5, <5%; 1, 5% to 25%; 2, 26% to 50%; 3, 51% to 75%, and 4, >75%. All specimens after chemotherapy, except the late recurrences, were better differentiated than their primary, untreated specimens. Pgp or MRP-1 expression did not change significantly, but LRP expression increased significantly after chemotherapy. In both untreated and treated samples, LRP was expressed primarily in differentiated cells. The findings indicate that the in vivo expression of LRP, but not of Pgp and MRP-1, is induced by chemotherapeutic treatment in rhabdomyosarcomas. The preferential expression of LRP in differentiated cells and the subsequent more extensive expression after chemotherapy suggests that LRP plays a role in therapy-induced differentiation.
 ...
PMID:Expression of multidrug resistance-associated proteins in rhabdomyosarcomas before and after chemotherapy: the relationship between lung resistance-related protein (LRP) and differentiation. 1261 83

This study was undertaken to investigate the expression and predictive value for outcome of multidrug resistance-associated (MDR) proteins P-glycoprotein (Pgp), MRP1, BCRP, and LRP, in advanced testicular germ-cell tumours (TGCT). Paraffin-embedded sections from 56 previously untreated patients with metastatic TGCT were immunostained for Pgp, MRP1, BCRP, and LRP. All patients received platinum-based chemotherapy after orchidectomy. Immunostaining was related to clinicopathological parameters, response to chemotherapy, and outcome. Strong and intermediate expressions of the different MDR-related proteins were: 27 and 41% (Pgp), 54 and 37% (MRP1), 86 and 7% (BCRP), and 14 and 29% (LRP). P-glycoprotein and MRP1 associated, respectively, to low AFP (P=0.026) and high LDH levels (P=0.014), whereas LRP expression associated with high beta-hCG levels (P=0.003) and stage IV tumours (P=0.029). No correlation was found between Pgp, MRP1, and BCRP expression and response to chemotherapy and survival. In contrast, patients with LRP-positive tumours (strong or intermediate expression) had shorter progression-free (P=0.0006) and overall survival (P=0.0116) than LRP-negative patients, even after individual log-rank adjustments by statistically associated variables. Our data suggest that a positive LRP immunostaining at the time of diagnosis in metastatic TGCT is associated with an adverse clinical outcome.
 ...
PMID:Lung resistance-related protein as a predictor of clinical outcome in advanced testicular germ-cell tumours. 1264 25