Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P04155 (pS2)
 1,234 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A novel in vivo model of tamoxifen-stimulated endometrial cancer was developed and the role of HER-2/neu investigated by using trastuzumab. Tamoxifen-stimulated tumors (ECC-1TAM) were growth stimulated by 17beta-estradiol (E2), tamoxifen, or raloxifene. Trastuzumab inhibited growth of E2-stimulated ECC-1E2 tumors by 50% and tamoxifen-stimulated ECC-1TAM tumors by 100%. ECC-1 tumors expressed functional estrogen receptor alpha (ER alpha) as measured by induction of pS2 and c-myc mRNAs. E2 induced pS2 and c-myc mRNAs up to 40-fold in ECC-1E2 and ECC-1TAM. Tamoxifen induced pS2 and c-myc mRNAs up to 5-fold in ECC-1E2 tumors and up to 10-fold in ECC-TAM tumors. Trastuzumab blocked E2-induced pS2 mRNA (P < 0.01) in ECC-1E2 by 50% and tamoxifen-induced c-myc mRNA (P < 0.1) in ECC-1TAM tumors by 70%. Trastuzumab decreased phosphorylated and total HER-2/neu protein in ECC-1E2 and ECC-1TAM tumors. However, only phospho-ERK-1/2 and not phospho-Akt protein was decreased by trastuzumab in tamoxifen-treated ECC-1TAM tumors. The insulin-like growth factor (IGF-I) signaling pathway also activates extracellular signal-related kinase (ERK)-1/2 and could block the efficacy of trastuzumab in ECC-1E2 tumors. The results showed that IGF-I, IGF-IR mRNAs, and phospho-insulin receptor substrate-1 (IRS-1) protein were decreased in ECC-1TAM compared with ECC-1E2 tumors. The results show that trastuzumab is an effective therapy for both E2-stimulated and tamoxifen-stimulated endometrial cancer. The data suggest estrogenic activities of E2 and tamoxifen at ER alpha-regulated pS2 and c-myc genes are in part mediated by HER-2/neu. However, trastuzumab is a better growth inhibitor of ECC-1TAM tumors where there is diminished IGF-I signaling allowing for complete blockade of the downstream phospho-ERK-1/2 signal.
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PMID:Trastuzumab therapy for tamoxifen-stimulated endometrial cancer. 1616 31

ERBB2 overexpression in estrogen receptor (ER)-positive breast cancer cells such as BT474 (BT) cells has been found to confer resistance to tamoxifen, and suppression of ERBB2 improves the antiproliferative effects of tamoxifen. In this study, the responsiveness to tamoxifen in the BT/HerR, Herceptin-resistant BT cell lines established through constant Herceptin exposure, was evaluated. Compared with BT cells, improvement of sensitivity to tamoxifen in BT/HerR was demonstrated by ER functional analysis and cell proliferation assay. Tamoxifen in the resistant cell line was found to inhibit 17beta-estradiol-stimulating estrogen-responsive gene pS2 expression more effectively than in BT cells in real-time PCR assay. Western blot analysis showed that cross-phosphorylation between ER and downstream components of ERBB2 was attenuated in BT/HerR cells. ER redistribution from cytoplasm to nucleus could be found in these cells through immunofluorescence and confocal studies, and importantly, chromatin immunoprecipitation studies demonstrated that tamoxifen induced occupancy of the pS2 promoter by ER and nuclear receptor corepressor (NCOR1) instead of coactivator NCOA3 in these cells. Finally, combination of tamoxifen and Herceptin was found to improve the sensitivity of BT/HerR cells to Herceptin. Our results suggest that the ER genomic pathway in the ER-positive and Herceptin-resistant breast cancer cells may be reactivated, allowing tamoxifen therapy to be effective again, and a combination of tamoxifen and Herceptin can be a potential therapeutic strategy for ER-positive and Herceptin-resistant human breast cancer.
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PMID:Improvement of sensitivity to tamoxifen in estrogen receptor-positive and Herceptin-resistant breast cancer cells. 1876 63

Treatment with tyrosine kinase inhibitors (TKIs) including trastuzumab has revolutionized the management of HER2-positive breast cancer. Recent evaluation of clinical trial data suggests that a subset of HER2/ER double-positive cancers may not receive significant benefit from the TKI therapy. Here we investigate the cross talk between HER2 and ER in breast cancer and monitor the effect of trastuzumab on the tyrosine kinase effector transcription factor Myc. In HER2-positive breast cancer patients treated with neoadjuvant trastuzumab, steroid receptor-negative status (ER and PR negative) of pre-treatment biopsies predicted pathological complete response (pCR) (n=31 patients, P=0.0486), whereas elevated Myc protein inversely associated with pCR (P=0.0446). Liquid chromatography mass spectrometry identified the corepressor SMRT as a novel Myc-interacting protein. Trastuzumab treatment enhanced Myc-SMRT interactions in HER2-overexpressing breast cancer cells (LCC1) and inhibited expression of the Myc target gene survivin. In HER2-low, ER-positive steroid-dominant cells (MCF7), trastuzumab therapy repressed Myc-SMRT interactions and upregulated survivin expression. Trastuzumab treatment induced ER-CBP interactions, enhanced ER transcriptional activity and upregulated expression of the ER target gene pS2. The absence of pS2 expression in pre-treatment biopsies predicted pCR to neoadjuvant trastuzumab in breast cancer patients (n=25, P=0.0089) and pS2 expression associated with residual cancer burden (P=0.0196). Furthermore, metastatic tissues from patients who had failed trastuzumab therapy were pS2 positive. In HER2-overexpressing cells, trastuzumab treatment can repress Myc transcriptional activity and clinical response is favorable. However, with co-expression of the steroid pathway, this inhibition is lost and response to treatment is often poor.
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PMID:Growth factor receptor/steroid receptor cross talk in trastuzumab-treated breast cancer. 2446 58