TY - JOUR
T1 - Expression of t-DARPP mediates trastuzumab resistance in breast cancer cells
AU - Belkhiri, Abbes
AU - Dar, Altaf A.
AU - Fa Peng, Dun
AU - Razvi, Mohammad H.
AU - Rinehart, Cammie
AU - Arteaga, Carlos L.
AU - El-Rifai, Wael
PY - 2008/7/15
Y1 - 2008/7/15
N2 - Purpose: We have investigated the role of t-DARPP in trastuzumab resistance in ERBB2-amplified and overexpressed breast cancer cell lines. Experimental Design: We have used the HR-5 and HR-6 trastuzumab-resistant cells that were established from tumors that recurred in the presence of trastuzumab therapy following xenografts of BT-474 cells in nude mice. In addition, SKBR-3 cells, engineered for stable expression of t-DARPP, and HCC-1569 cells, which have constitutive expression of t-DARPP and are de novo resistant to trastuzumab, were used. Results: We reported ≥15-fold up-regulation of mRNA and protein levels of t-DARPP in HR-5 and HR-6 cells compared with their progenitor BT-474 trastuzumab-sensitive cells. The t-DARPP expression was not regulated by changes in its promoter DNA methylation levels. The SKBR-3 cells stably expressing t-DARPP developed resistance to trastuzumab compared with their parental cells and empty vector controls (P < 0.01). The trastuzumab-resistant cell lines showed a significant increase in pAKT (Ser473) and BCL2 protein levels. The small interfering RNA knockdown of t-DARPP in all trastuzumab-resistant cells led to a significant reduction in ERBB2, pAKT (Ser473), and BCL2 protein levels with a significant decrease in cell viability (P ≤ 0.001) and an increase in cleaved caspase-3 levels, indicating the progression of these cells toward apoptosis. The t-DARPP protein was associated with both heat shock protein 90 and ERBB2 forming a potential protein complex. This association may play a role in regulating ERBB2 protein in trastuzumab-resistant cells. Conclusion: We conclude that t-DARPP is a novel molecular target that can mediate the therapeutic resistance to trastuzumab in breast cancer cells.
AB - Purpose: We have investigated the role of t-DARPP in trastuzumab resistance in ERBB2-amplified and overexpressed breast cancer cell lines. Experimental Design: We have used the HR-5 and HR-6 trastuzumab-resistant cells that were established from tumors that recurred in the presence of trastuzumab therapy following xenografts of BT-474 cells in nude mice. In addition, SKBR-3 cells, engineered for stable expression of t-DARPP, and HCC-1569 cells, which have constitutive expression of t-DARPP and are de novo resistant to trastuzumab, were used. Results: We reported ≥15-fold up-regulation of mRNA and protein levels of t-DARPP in HR-5 and HR-6 cells compared with their progenitor BT-474 trastuzumab-sensitive cells. The t-DARPP expression was not regulated by changes in its promoter DNA methylation levels. The SKBR-3 cells stably expressing t-DARPP developed resistance to trastuzumab compared with their parental cells and empty vector controls (P < 0.01). The trastuzumab-resistant cell lines showed a significant increase in pAKT (Ser473) and BCL2 protein levels. The small interfering RNA knockdown of t-DARPP in all trastuzumab-resistant cells led to a significant reduction in ERBB2, pAKT (Ser473), and BCL2 protein levels with a significant decrease in cell viability (P ≤ 0.001) and an increase in cleaved caspase-3 levels, indicating the progression of these cells toward apoptosis. The t-DARPP protein was associated with both heat shock protein 90 and ERBB2 forming a potential protein complex. This association may play a role in regulating ERBB2 protein in trastuzumab-resistant cells. Conclusion: We conclude that t-DARPP is a novel molecular target that can mediate the therapeutic resistance to trastuzumab in breast cancer cells.
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U2 - 10.1158/1078-0432.CCR-08-0121
DO - 10.1158/1078-0432.CCR-08-0121
M3 - Article
C2 - 18579663
AN - SCOPUS:51649096911
SN - 1078-0432
VL - 14
SP - 4564
EP - 4571
JO - Clinical Cancer Research
JF - Clinical Cancer Research
IS - 14
ER -