Sources/Clones
Accurate (MRPr1), Biodesign (JSB-1), Coulter (UIC1), Dako (C494, 4E3, C219), Immunotech (MRK-16, UIC2), Monosan (JSB-1, MRPm6, LRP-56), Novocastra, Oncogene, Sanbio (MRPr1), Seralab (JSB-1), Signet (C219, C494, JSB-1) and Zymed (JSB-1).
Fixation/Preparation
Most antibodies available are immunoreactive in frozen sections and some react in fixed paraffin-embedded sections, enhanced by HIER treatment.
Background
P-glycoprotein (P-170) is a transmembrane protein of 170 kD molecular weight. It has been associated with both intrinsic and acquired resistance to certain chemotherapeutic agents, particularly anthracyclines and vinca alkaloids. It is an energy-dependent pump which functions in drug efflux, reducing intracellular accumulation of chemotherapeutic agents, thus conferring the so-called multi-drug resistance (MDR) phenomenon on cells expressing increased levels of this protein (Kartner & Ling, 1989; Gottesman et al, 1991). One of the most perplexing problems encountered in chemotherapy is the resistance of certain tumors to all chemotherapeutic regimens, while other tumors which are initially chemosensitive to a particular agent show resistance to treatment over time and with disease progression. Furthermore, tumor cells which are resistant to one drug often show crossresistance to a wide variety of other, structurally unrelated drugs. For example, tumor cells resistant to adriamycin can show cross-resistance to diverse drugs to which they have never been exposed, including vinca alkaloids and mitomycin C, but not to other drugs such as alkylating agents. This is known as the MDR phenomenon (Leong & Leong, 1997). A family of so-called MDR genes encodes the P-glycoprotein, apparently with only the protein encoded by the MDR 1 gene inducing the MDR phenotype.
There is extensive evidence from in vitro studies, especially with non-human cell lines, that overexpression of P-glycoprotein results in reduced accumulation of drug within the cell. Recently, mice have been generated with knockout of MDR 1 and these animals show abnormalities of transport at the blood-brain barrier and are more sensitive to drugs.
Applications
Molecular and immunohistochemical studies of P-glycoprotein reveal that it is overexpressed in a number of intrinsically resistant tumors such as carcinomas of the liver, pancreas, colon, adrenal cortex and kidney, and appears to vary according to the differentiation of the cells (Cordon-Cardo et al 1990; Lopes et al 1997). Interestingly, in these cases, high levels of the protein have also been demonstrated in the normal tissues from which the tumors are derived. The physiologic function of P-glycoprotein can be deduced from its normal tissue distribution in that high levels of expression are seen in endothelial cells of the blood-brain barrier and in renal proximal tubules, both cell types having the primary function of moving toxic molecules across cell membranes (Schinkel et al, 1994). Tumors responsive to chemotherapy generally show low levels of P-glycoprotein expression and solid tumors that are most responsive to systemic chemotherapy, such as seminomas and embryonal carcinomas, rarely display detectable levels of the protein. Tumors from patients previously treated with chemotherapy show frequent elevation of P-glycoprotein, suggesting that the MDR phenotype is induced by exposure to chemotherapy. The detection of elevated levels of P-glycoprotein expression has the potential to identify tumors likely to be resistant to conventional chemotherapy and may provide a rationale for the use of alternative treatments for such patients. Immunohistological evaluation appears to be the method of choice for the assessment of P-glycoprotein, largely because it allows morphological correlation and discrimination from that in non-tumor cells (Ramani & Dewchand, 1995).
Comments
Only two MDR genes are known to be present in man, namely MDR 1 and MDR 3, but only the MDR 1 gene product confers the MDR phenotype. One of the most widely used antibodies to P-glycoprotein is clone C219 which reacts with both the MDR 1 and MDR 3 gene products. Several other antibodies specific to the MDR 1 gene product have now been described. They include HYB-24, HYB-612, and C494. While earlier studies were conducted on frozen sections, HIER has improved the immunoreactivity in fixed paraffin-embedded sections. Renal proximal tubules are used as the standard positive control because of the high levels of expression of P-glycoprotein in the epithelial cells.
References
•Cordon-Cardo C, O'Brien JP, Boccia J et al 1990. Expression of the multidrug resistance gene product (P-glycoprotein) in human normal and tumor tissues. Journal of Histochemistry and Cytochemistry 38: 1277-1287.
•Gottesman MM, Goldstein LJ, Fojo A et al 1991. Expression of the multidrug resistance gene in human cancer. In: Ronison IB (ed) Molecular cellular biology of multi-drug resistance in tumor cells. New York: Plenum Press, pp 291-301.
•Kartner N, Ling V 1989. Multidrug resistance in cancer. Science 260: 44-51.
•Leong AS-Y, Leong FJ 1998. Cancer genetics-what you need to know. Diagnostic Cytopathology 18: 33-40.
•Lopes JM, Bruland OS, Bjekehagen B et al 1997. Synovial sarcoma: immunohistochemical expression of P-glycoprotein and glutathione S transferase-pi and clinical drug resistance. Pathology Research and Practice 193: 21-36.
•Ramani P, Dewchand H 1995. Expression of mdr 1/P-glycoprotein and P110 in neuroblastoma. Journal of Pathology 175: 13-22.
•Schinkel AH, Smith JJM, Van Telingen O 1994. Disruption of the mouse mdr 1AP-glycoprotein gene leads to a deficiency in the blood-brain barrier and to increased sensitivity to drugs. Cell 77:491-502.
Bibliografia
Manual of diagnostic antibodies for immunohistology / Anthony S.-Y. Leong, Kumarasen Cooper, F. Joel W.-M. Leong.
Accurate (MRPr1), Biodesign (JSB-1), Coulter (UIC1), Dako (C494, 4E3, C219), Immunotech (MRK-16, UIC2), Monosan (JSB-1, MRPm6, LRP-56), Novocastra, Oncogene, Sanbio (MRPr1), Seralab (JSB-1), Signet (C219, C494, JSB-1) and Zymed (JSB-1).
Fixation/Preparation
Most antibodies available are immunoreactive in frozen sections and some react in fixed paraffin-embedded sections, enhanced by HIER treatment.
Background
P-glycoprotein (P-170) is a transmembrane protein of 170 kD molecular weight. It has been associated with both intrinsic and acquired resistance to certain chemotherapeutic agents, particularly anthracyclines and vinca alkaloids. It is an energy-dependent pump which functions in drug efflux, reducing intracellular accumulation of chemotherapeutic agents, thus conferring the so-called multi-drug resistance (MDR) phenomenon on cells expressing increased levels of this protein (Kartner & Ling, 1989; Gottesman et al, 1991). One of the most perplexing problems encountered in chemotherapy is the resistance of certain tumors to all chemotherapeutic regimens, while other tumors which are initially chemosensitive to a particular agent show resistance to treatment over time and with disease progression. Furthermore, tumor cells which are resistant to one drug often show crossresistance to a wide variety of other, structurally unrelated drugs. For example, tumor cells resistant to adriamycin can show cross-resistance to diverse drugs to which they have never been exposed, including vinca alkaloids and mitomycin C, but not to other drugs such as alkylating agents. This is known as the MDR phenomenon (Leong & Leong, 1997). A family of so-called MDR genes encodes the P-glycoprotein, apparently with only the protein encoded by the MDR 1 gene inducing the MDR phenotype.
There is extensive evidence from in vitro studies, especially with non-human cell lines, that overexpression of P-glycoprotein results in reduced accumulation of drug within the cell. Recently, mice have been generated with knockout of MDR 1 and these animals show abnormalities of transport at the blood-brain barrier and are more sensitive to drugs.
Applications
Molecular and immunohistochemical studies of P-glycoprotein reveal that it is overexpressed in a number of intrinsically resistant tumors such as carcinomas of the liver, pancreas, colon, adrenal cortex and kidney, and appears to vary according to the differentiation of the cells (Cordon-Cardo et al 1990; Lopes et al 1997). Interestingly, in these cases, high levels of the protein have also been demonstrated in the normal tissues from which the tumors are derived. The physiologic function of P-glycoprotein can be deduced from its normal tissue distribution in that high levels of expression are seen in endothelial cells of the blood-brain barrier and in renal proximal tubules, both cell types having the primary function of moving toxic molecules across cell membranes (Schinkel et al, 1994). Tumors responsive to chemotherapy generally show low levels of P-glycoprotein expression and solid tumors that are most responsive to systemic chemotherapy, such as seminomas and embryonal carcinomas, rarely display detectable levels of the protein. Tumors from patients previously treated with chemotherapy show frequent elevation of P-glycoprotein, suggesting that the MDR phenotype is induced by exposure to chemotherapy. The detection of elevated levels of P-glycoprotein expression has the potential to identify tumors likely to be resistant to conventional chemotherapy and may provide a rationale for the use of alternative treatments for such patients. Immunohistological evaluation appears to be the method of choice for the assessment of P-glycoprotein, largely because it allows morphological correlation and discrimination from that in non-tumor cells (Ramani & Dewchand, 1995).
Comments
Only two MDR genes are known to be present in man, namely MDR 1 and MDR 3, but only the MDR 1 gene product confers the MDR phenotype. One of the most widely used antibodies to P-glycoprotein is clone C219 which reacts with both the MDR 1 and MDR 3 gene products. Several other antibodies specific to the MDR 1 gene product have now been described. They include HYB-24, HYB-612, and C494. While earlier studies were conducted on frozen sections, HIER has improved the immunoreactivity in fixed paraffin-embedded sections. Renal proximal tubules are used as the standard positive control because of the high levels of expression of P-glycoprotein in the epithelial cells.
References
•Cordon-Cardo C, O'Brien JP, Boccia J et al 1990. Expression of the multidrug resistance gene product (P-glycoprotein) in human normal and tumor tissues. Journal of Histochemistry and Cytochemistry 38: 1277-1287.
•Gottesman MM, Goldstein LJ, Fojo A et al 1991. Expression of the multidrug resistance gene in human cancer. In: Ronison IB (ed) Molecular cellular biology of multi-drug resistance in tumor cells. New York: Plenum Press, pp 291-301.
•Kartner N, Ling V 1989. Multidrug resistance in cancer. Science 260: 44-51.
•Leong AS-Y, Leong FJ 1998. Cancer genetics-what you need to know. Diagnostic Cytopathology 18: 33-40.
•Lopes JM, Bruland OS, Bjekehagen B et al 1997. Synovial sarcoma: immunohistochemical expression of P-glycoprotein and glutathione S transferase-pi and clinical drug resistance. Pathology Research and Practice 193: 21-36.
•Ramani P, Dewchand H 1995. Expression of mdr 1/P-glycoprotein and P110 in neuroblastoma. Journal of Pathology 175: 13-22.
•Schinkel AH, Smith JJM, Van Telingen O 1994. Disruption of the mouse mdr 1AP-glycoprotein gene leads to a deficiency in the blood-brain barrier and to increased sensitivity to drugs. Cell 77:491-502.
Bibliografia
Manual of diagnostic antibodies for immunohistology / Anthony S.-Y. Leong, Kumarasen Cooper, F. Joel W.-M. Leong.
