Involvement of bcl-2 and p21 super(waf1) proteins in response of human breast cancer cell clones to Tomudex
Mechanisms of resistance to Tomudex include increased thymidylate synthase activity, as well as reduced intracellular drug uptake and polyglutamation. However, little is known about other mechanisms of resistance, such as a possible protection against Tomudex-induced apoptosis mediated by bcl-2. We...
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| Published in: | British journal of cancer Vol. 81; no. 2; pp. 252 - 260 |
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| Main Authors: | , , , , , |
| Format: | Journal Article |
| Language: | English |
| Published: |
01-09-1999
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| Online Access: | Get full text |
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| Summary: | Mechanisms of resistance to Tomudex include increased thymidylate synthase activity, as well as reduced intracellular drug uptake and polyglutamation. However, little is known about other mechanisms of resistance, such as a possible protection against Tomudex-induced apoptosis mediated by bcl-2. We transfected the MDA-MB-435 human breast cancer cell line, which is characterized by a mutated p53 gene, with cDNA of the bcl-2 gene and generated two clones (MDA-bcl4 and MDA-bcl7) characterized by bcl-2 expression twofold and fourfold that observed in the control cell clone (MDA super(neo)). A concomitant overexpression of p21 super(wafl) was also detected in the MDA-bcl7 clone. The MDA-bcl4 clone was three times more resistant to a 24-h Tomudex exposure than the MDA super(neo) clone, whereas the MDA-bcl7 clone was as sensitive to Tomudex as the control cell clone. A lower sensitivity of the MDA-bcl4 clone than MDA super(neo) and MDA-bcl7 clones to 5-fluorouracil and gemcitabine was also observed. No significant difference was noted in the susceptibility of clones to fludarabine and methothrexate. Basal levels of thymidylate synthase activity were superimposable in the three clones. Tomudex induced a marked accumulation of cells in the S phase in all the clones. However, an apoptotic hypodiploid DNA peak and the characteristic nuclear morphology of apoptosis were observed only in the MDA-bcl7 clone after exposure to Tomudex. No difference in the treatment-induced modulation of proteins involved in cell cycle progression (cyclin A, cdk2, pRB, E2F-1) and apoptosis (bcl-2, bax) was observed in the three clones. The only exception was that the expression of p21 super(wafl) in the MDA-bcl4 clone was inducible at a Tomudex concentration much higher than that required to induce the protein in the other clones. Overall, the results indicate that bcl-2 and p21 super(wafl) proteins concur in determining the cellular profile of sensitivity/resistance to Tomudex. |
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| Bibliography: | ObjectType-Article-2 SourceType-Scholarly Journals-1 content type line 23 ObjectType-Feature-1 |
| ISSN: | 0007-0920 |