Glucosylceramide synthase inhibitors sensitise CLL cells to cytotoxic agents without reversing P-gp functional activity.
Malignant B-cells from most chronic lymphocytic leukaemia (CLL) patients over-express MDR1 encoded P-glycoprotein (P-gp) multidrug efflux pump. Inhibition of glucosylceramide (GC) synthesis has been shown in cell lines to correlate with the expression and function of P-gp and sensitise cancer cells...
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| Format: | Journal article |
| Language: | English |
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2009
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| _version_ | 1797087985900978176 |
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| author | Gerrard, G Butters, T Ganeshaguru, K Mehta, AB |
| author_facet | Gerrard, G Butters, T Ganeshaguru, K Mehta, AB |
| author_sort | Gerrard, G |
| collection | OXFORD |
| description | Malignant B-cells from most chronic lymphocytic leukaemia (CLL) patients over-express MDR1 encoded P-glycoprotein (P-gp) multidrug efflux pump. Inhibition of glucosylceramide (GC) synthesis has been shown in cell lines to correlate with the expression and function of P-gp and sensitise cancer cells to cytotoxic agents. We investigated the hypothesis that reducing intracellular GC levels will reduce P-gp expression in malignant cells from CLL patients. We studied the ability of glucosylceramide synthase (GCS) inhibitors N-butyl-deoxygalactonojirimycin (OGB-1) and N-nonyl-deoxygalactonojirimycin (OGB-2) to sensitise CLL cells to conventional cytotoxic drug 2-chlorodeoxyadenosine (CdA) and the cytostatic drugs chlorambucil and fludarabine. The effect on P-gp activity was analysed using the calcein-AM accumulation assay where a multidrug activity factor (MAF) of >10 in the presence of a P-gp inhibitor denotes P-gp functional activity. The P-gp over-expressing cell line CEM-VLB showed a MAF value of 96.4 with the P-gp inhibitor Z.3HCL, which fell to 15.7 after co-incubation with OGB-1 and 45.9 with OGB-2. The IC(50) for vincristine fell from >10 microg/ml to 55.5 ng/ml in the presence of OGB-2. In P-gp(+ve) peripheral blood mononuclear cells from three normal volunteers, the mean MAF values for Z.3HCL, OGB-1 and OGB-2 were 23.86, 1.83 and 16.2 respectively. In 9/13 CLL samples the mean P-gp functional activity was 22.15 and P-gp was over-expressed in 12/13 samples. However, the MAF value with OGB-1 and OGB-2 was <10. Nevertheless, sensitisation in CLL cells was observed by a reduction in the IC(50) in the presence of OGB-1 and OGB-2 with the conventional drugs. We conclude that although GCS inhibitors sensitize CLL cells to cytotoxic and cytostatic drugs, they do not appear to have any effect on P-gp functional activity. |
| first_indexed | 2024-03-07T02:43:24Z |
| format | Journal article |
| id | oxford-uuid:ab396e6b-cea8-4c0b-91ac-43ddc0c4004b |
| institution | University of Oxford |
| language | English |
| last_indexed | 2024-03-07T02:43:24Z |
| publishDate | 2009 |
| record_format | dspace |
| spelling | oxford-uuid:ab396e6b-cea8-4c0b-91ac-43ddc0c4004b2022-03-27T03:20:30ZGlucosylceramide synthase inhibitors sensitise CLL cells to cytotoxic agents without reversing P-gp functional activity.Journal articlehttp://purl.org/coar/resource_type/c_dcae04bcuuid:ab396e6b-cea8-4c0b-91ac-43ddc0c4004bEnglishSymplectic Elements at Oxford2009Gerrard, GButters, TGaneshaguru, KMehta, ABMalignant B-cells from most chronic lymphocytic leukaemia (CLL) patients over-express MDR1 encoded P-glycoprotein (P-gp) multidrug efflux pump. Inhibition of glucosylceramide (GC) synthesis has been shown in cell lines to correlate with the expression and function of P-gp and sensitise cancer cells to cytotoxic agents. We investigated the hypothesis that reducing intracellular GC levels will reduce P-gp expression in malignant cells from CLL patients. We studied the ability of glucosylceramide synthase (GCS) inhibitors N-butyl-deoxygalactonojirimycin (OGB-1) and N-nonyl-deoxygalactonojirimycin (OGB-2) to sensitise CLL cells to conventional cytotoxic drug 2-chlorodeoxyadenosine (CdA) and the cytostatic drugs chlorambucil and fludarabine. The effect on P-gp activity was analysed using the calcein-AM accumulation assay where a multidrug activity factor (MAF) of >10 in the presence of a P-gp inhibitor denotes P-gp functional activity. The P-gp over-expressing cell line CEM-VLB showed a MAF value of 96.4 with the P-gp inhibitor Z.3HCL, which fell to 15.7 after co-incubation with OGB-1 and 45.9 with OGB-2. The IC(50) for vincristine fell from >10 microg/ml to 55.5 ng/ml in the presence of OGB-2. In P-gp(+ve) peripheral blood mononuclear cells from three normal volunteers, the mean MAF values for Z.3HCL, OGB-1 and OGB-2 were 23.86, 1.83 and 16.2 respectively. In 9/13 CLL samples the mean P-gp functional activity was 22.15 and P-gp was over-expressed in 12/13 samples. However, the MAF value with OGB-1 and OGB-2 was <10. Nevertheless, sensitisation in CLL cells was observed by a reduction in the IC(50) in the presence of OGB-1 and OGB-2 with the conventional drugs. We conclude that although GCS inhibitors sensitize CLL cells to cytotoxic and cytostatic drugs, they do not appear to have any effect on P-gp functional activity. |
| spellingShingle | Gerrard, G Butters, T Ganeshaguru, K Mehta, AB Glucosylceramide synthase inhibitors sensitise CLL cells to cytotoxic agents without reversing P-gp functional activity. |
| title | Glucosylceramide synthase inhibitors sensitise CLL cells to cytotoxic agents without reversing P-gp functional activity. |
| title_full | Glucosylceramide synthase inhibitors sensitise CLL cells to cytotoxic agents without reversing P-gp functional activity. |
| title_fullStr | Glucosylceramide synthase inhibitors sensitise CLL cells to cytotoxic agents without reversing P-gp functional activity. |
| title_full_unstemmed | Glucosylceramide synthase inhibitors sensitise CLL cells to cytotoxic agents without reversing P-gp functional activity. |
| title_short | Glucosylceramide synthase inhibitors sensitise CLL cells to cytotoxic agents without reversing P-gp functional activity. |
| title_sort | glucosylceramide synthase inhibitors sensitise cll cells to cytotoxic agents without reversing p gp functional activity |
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