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)

Metastatic malignant melanoma is notoriously resistant to chemotherapeutic agents, but the exact mechanisms involved in this drug resistance are unknown. One recently defined major mechanism of multidrug resistance involves the overexpression of P-glycoprotein on cell membranes. In order to evaluate the significance of this putative drug efflux pump for chemoresistance of malignant melanoma, five different antibodies were employed to examine P-glycoprotein expression on tissue from 33 primary malignant melanomas and 35 metastases, before and after chemotherapy, using immunohistological techniques. The expression of P-glycoprotein was low on primary cutaneous melanomas (three of 33), and on metastases (one of 35). Normal tissue in and around the melanoma showed reactivity of endothelial cells, stromal cells and eccrine sweat glands with several antibodies tested. Chemotherapy with drugs commonly used in metastatic melanoma, including agents known to induce P-glycoprotein expression in other tumours (vindesine, cisplatin) had no effect on P-glycoprotein expression in human melanoma metastases. The high chemoresistance of human melanoma cells in vitro and in vivo is probably not mediated via P-glycoprotein, and other possible mechanisms involved will have to be explored in future studies.
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PMID:P-glycoprotein expression in primary and metastatic malignant melanoma. 774 45

Metastatic malignant melanoma is considered a chemotherapy-refractory malignancy. A few previous studies have delivered contradictory results regarding the presence and functionality of P-glycoprotein (P-gp), a transmembranous protein associated with the classical multidrug resistance (cMDR), in malignant melanoma. Therefore we have investigated this issue on 33 cell lines established from primary and metastatic lesions of human malignant melanoma, comparing different cMDR detection methods. Immunocytochemically 33% of the cell lines stained positive for P-gp. The data correlated with those of a P-gp-radioimmunometric (antibody-binding) assay. When RT-PCR was used for MDR-1 mRNA determination, 76% of the melanoma cell lines scored positive. Slot-blot analysis was seen to be less sensitive than RT-PCR. Results from the functional P-gp assays, using daunomycin (DM) as MDR-substrate, showed no influence of P-gp expression on drug accumulation and cytotoxicity. However, the cMDR-modifier verapamil (VP) significantly increased both parameters in those melanoma cells with the highest P-gp levels. We conclude that cMDR is apparently not the decisive but probably a complementary protective mechanism against toxic agents in malignant melanoma.
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PMID:Intrinsic MDR-1 gene and P-glycoprotein expression in human melanoma cell lines. 796 Feb 46

Metastatic malignant melanoma (MM) is well known for its poor response to chemotherapy, radiotherapy, and its remarkable susceptibility to interleukin-2 (IL-2) based immunotherapies. MM with brain metastatis in particular, has 4-5 months life expectancy from metastasis to death. Drug efflux pumps such as P-glycoprotein (P-gp), or drug detoxifying mechanisms e.g. glutathion epsilon S-transferase-pi (GST) are some of the possible multidrug resistance (MDR) mechanisms in MM. Here we report the first P-gp+ MDR MM with brain metastasis in the literature, demonstrating a remarkable response to IL-2, interferon-alpha (IFN), 5-fluorouracil (5FU) regimen. A 41-year old man was admitted with multiple inoperable brain lesions. Biopsies from intracranial and dermal lesions revealed MM. Cisplatin, carmustine, dacarbazine, tamoxifen (CCDT) together with external cranial radiotherapy were administered, and partial response in lesions and symptoms was achieved. However, after the third course of CCDT treatment, he was admitted to the emergency ward with dramatically increased intracranial lesions, and recurring dermal lesions. A biopsy from the recurred lesions revealed that MM cells were P-gp+, but GST. Administration of a IL-2, IFN and 5FU regimen achieved a remarkable decline in the brain lesions with almost total disappearance of symptoms. He was well and capable of doing work for 18 months. Dermal lesions had not recurred since the beginning of immunotherapy. In contrast, another 34-year old man who developed brain metastases after CCDT for MM, was negative for P-gp and GST. Cranial radiotherapy was started and the above mentioned IL-2 based regimen was administered. However, no response was observed. These two cases together with previous studies demonstrating the susceptibility of P-gp+ MDR cancer cell lines to IL-2 activated killer (LAK) cells in this report suggest that P-gp+ MDR MM is probably a good candidate for IL-2 based treatments.
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PMID:Multidrug resistant malignant melanoma with intracranial metastasis responding to immunotherapy. 1065 Jul 85