TY - JOUR
T1 - Altered localization of a coactivator sensitizes breast cancer cells to tumor necrosis factor-induced apoptosis
AU - Rayla, Suresh K.
AU - Mascarenhas, Joseph
AU - Vadlamudi, Ratna K.
AU - Kumar, Rakesh
PY - 2006/2
Y1 - 2006/2
N2 - Proline-, glutamic acid-, and leucine-rich protein-1 (PELP1) is a novel coregulator of the estrogen receptor that plays a role in both genomic and nongenomic actions of the estrogen receptor. Emerging studies suggest that in addition to the nuclear localization of PELP1, it is predominantly localized in the cytoplasm in human breast tumors, leading to excessive nongenomic signaling and possibly to tamoxifen resistance. The mechanisms underlying resistance to hormones in preclinical model systems remain under intense investigation. In an effort to develop a model system to treat tumor cells with cytoplasmic PELP1 expression and tamoxifen resistance, here we used the cytokine tumor necrosis factor (TNF)-α. We found that clones of MCF-7 human breast cancer cells overexpressing PELP1 in the cytoplasm were distinctly sensitive to TNF-α-induced apoptosis than were wild-type nuclear PELP1- and pcDNA vector-expressing clones as revealed by cell growth assay, cell cycle analysis, Annexin V staining, and terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling assay. We also found that the clones with cytoplasmic PELP1 overexpression had significantly less antiapoptotic protein Bcl-2 and nuclear factor-κB DNA binding, but increased cyclin E expression, further supporting evidence that these cells are sensitive to apoptosis. The mechanism behind TNF-induced apoptosis in these cells involves caspases, as revealed by poly(ADP-ribose) polymerase cleavage and the broad-spectrum caspase inhibitor Z-VAD-inhibited apoptosis. In conclusion, our results suggest that altered localization of PELP1 promotes heightened sensitivity to TNF-α in MCF-7 cells, paving the way for developing new treatment strategies for tumors with cytoplasmic PELP1 expression.
AB - Proline-, glutamic acid-, and leucine-rich protein-1 (PELP1) is a novel coregulator of the estrogen receptor that plays a role in both genomic and nongenomic actions of the estrogen receptor. Emerging studies suggest that in addition to the nuclear localization of PELP1, it is predominantly localized in the cytoplasm in human breast tumors, leading to excessive nongenomic signaling and possibly to tamoxifen resistance. The mechanisms underlying resistance to hormones in preclinical model systems remain under intense investigation. In an effort to develop a model system to treat tumor cells with cytoplasmic PELP1 expression and tamoxifen resistance, here we used the cytokine tumor necrosis factor (TNF)-α. We found that clones of MCF-7 human breast cancer cells overexpressing PELP1 in the cytoplasm were distinctly sensitive to TNF-α-induced apoptosis than were wild-type nuclear PELP1- and pcDNA vector-expressing clones as revealed by cell growth assay, cell cycle analysis, Annexin V staining, and terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling assay. We also found that the clones with cytoplasmic PELP1 overexpression had significantly less antiapoptotic protein Bcl-2 and nuclear factor-κB DNA binding, but increased cyclin E expression, further supporting evidence that these cells are sensitive to apoptosis. The mechanism behind TNF-induced apoptosis in these cells involves caspases, as revealed by poly(ADP-ribose) polymerase cleavage and the broad-spectrum caspase inhibitor Z-VAD-inhibited apoptosis. In conclusion, our results suggest that altered localization of PELP1 promotes heightened sensitivity to TNF-α in MCF-7 cells, paving the way for developing new treatment strategies for tumors with cytoplasmic PELP1 expression.
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U2 - 10.1158/1535-7163.MCT-05-0276
DO - 10.1158/1535-7163.MCT-05-0276
M3 - Article
C2 - 16505095
SN - 1535-7163
VL - 5
SP - 230
EP - 237
JO - Molecular Cancer Therapeutics
JF - Molecular Cancer Therapeutics
IS - 2
ER -