Trastuzumab Down-Regulates Bcl-2 Expression and Potentiates Apoptosis Induction by Bcl-2/Bcl-XL Bispecific Antisense Oligonucleotides in HER-2 Gene–Amplified Breast Cancer Cells
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Media type:
E-Article
Title:
Trastuzumab Down-Regulates Bcl-2 Expression and Potentiates Apoptosis Induction by Bcl-2/Bcl-XL Bispecific Antisense Oligonucleotides in HER-2 Gene–Amplified Breast Cancer Cells
imprint:
American Association for Cancer Research (AACR), 2004
Published in:Clinical Cancer Research
Language:
English
DOI:
10.1158/1078-0432.ccr-04-0908
ISSN:
1078-0432;
1557-3265
Origination:
Footnote:
Description:
<jats:title>Abstract</jats:title>
<jats:p>Purpose: To investigate the possible existence of an antiapoptotic cross-talk between HER-2 and antiapoptotic Bcl-2 family members.</jats:p>
<jats:p>Experimental Design: Bcl-2 and Bcl-XL expression and apoptosis induction were analyzed in HER-2gene–amplified (BT474) and nonamplified (ZR 75-1) breast cancer cell lines exposed to trastuzumab, alone or in combination with either Bcl-2/Bcl-XL bispecific antisense oligonucleotides (AS-4625) or the small-molecule Bcl-2 antagonist HA14-1.</jats:p>
<jats:p>Results: In addition to HER-2 and epidermal growth factor receptor, trastuzumab down-regulated Bcl-2, but not Bcl-XL, protein, and mRNA expression in BT474 cells. Interestingly, trastuzumab-induced down-regulation of HER-2 and Bcl-2 was also observed in three of five and two of three breast cancer patients undergoing trastuzumab treatment, respectively. Despite Bcl-2 down-regulation, however, trastuzumab only marginally increased the rate of apoptosis (7.3 ± 3.5%). We therefore investigated whether a combination of AS-4625 and trastuzumab might increase proapoptotic efficiency. AS-4625 treatment of BT474 cells decreased both Bcl-2 and Bcl-XL expression, resulting in a 21 ± 7% net apoptosis induction; the combination of AS-4625 followed by trastuzumab resulted in a significantly stronger induction of apoptosis (37 ± 6%, P &lt; 0.01) that was not observed with the reverse treatment sequence (trastuzumab followed by AS-4625). Similar results were obtained with the Bcl-2 antagonist HA14-1; indeed, exposure of BT474 cells to HA14-1 followed by trastuzumab resulted in a striking proapoptotic synergism (combination index = 0.58 ± 0.18), as assessed by isobologram analysis.</jats:p>
<jats:p>Conclusions: Altogether our findings suggest that combined targeting of HER-2 and Bcl-2 may represent a novel, rational approach to more effective breast cancer therapy.</jats:p>