Elevated Bcl-2/Bax are a consistent feature of apoptosis resistance in B-cell chronic lymphocytic leukaemia and are correlated with in vivo chemoresistance.
We investigated the relationship between drug resistance and Bcl-2/Bax in B-cell chronic lymphocytic leukaemia (B-CLL). Apoptosis was induced in vitro with chlorambucil and cell death was monitored by dual-labelled FACS analysis using Annexin V and propidium iodide. Bcl-2 and Bax protein expression was quantified using FACS and a correlation between drug-induced apoptosis and Bcl-2/Bax was established. Cells were then sorted into viable and nonviable populations according to their forward and side-scatter characteristics and re-analysed for Bcl-2/Bax. The most resistant cells had elevated Bcl-2 levels and low Bax expression. Furthermore, those cells which were undergoing apoptosis showed only a marginal reduction in Bcl-2 expression, but significantly elevated Bax expression following exposure to chlorambucil. The Bcl-2/Bax was significantly greater in the cell fractions resistant to chlorambucil-induced apoptosis. This observation further supports the suggestion that Bax is the pivotal protein in determining the fate of cells following apoptotic signals.
Pepper
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Department of Haematology, Llandough Hospital, Penarth, South Glamorgan, UK.
Hoy
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Bentley
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D018906:Antineoplastic Agents, Alkylating / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects; D002469:Cell Separation; D002699:Chlorambucil / Q000494:pharmacology; D015536:Down-Regulation; D019008:Drug Resistance, Neoplasm; D005434:Flow Cytometry; D006801:Humans; D066298:In Vitro Techniques; D015451:Leukemia, Lymphocytic, Chronic, B-Cell / Q000378:metabolism* / Q000473:pathology; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism*; D051028:bcl-2-Associated X Protein
D018906:Antineoplastic Agents, Alkylating; C494826:BAX protein, human; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D051028:bcl-2-Associated X Protein; D002699:Chlorambucil