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Expression profiling of ligand-stimulated wild type and tamoxifen-resistant MCF-7

ABSTRACT: Quantitative phosphoproteome and transcriptome analysis of ligand-stimulated MCF-7 human breast cancer cells was performed to understand the mechanisms of tamoxifen resistance at a systems level. Phosphoproteome data revealed that wild type (WT) cells were more enriched with phospho-proteins than tamoxifen-resistant (TamR) cells after stimulation with ligands. Surprisingly, decreased phosphorylation after ligand perturbation was more common than increased phosphorylation. In particular, 17beta-estradiol (E2) induced down-regulation in WT cells at a very high rate. E2 and the ErbB ligand, heregulin (HRG) induced almost equal numbers of up-regulated phospho-proteins in WT cells. Pathway and motif activity analyses using transcriptome data additionally suggested that deregulated activation of GSK3B　(glycogen synthase kinase 3 beta) and MAPK1/3 signaling might be associated with altered activation of CREB and AP-1 transcription factors in TamR cells and this hypothesis was validated by reporter assays. An examination of clinical samples revealed that, inhibitory phosphorylation of GSK3B at serine 9 was significantly lower in tamoxifen-treated breast cancer patients that eventually had relapses, implying that activation of GSK3B may be associated with the tamoxifen resistant phenotype. Thus, the combined phosphoproteome and transcriptome dataset analyses revealed distinct signal-transcription programs in tumor cells and provided a novel molecular target to understand tamoxifen resistance. The MCF-7 human breast cancer cell line and tamoxifen-resistant MCF-7 cells were stimulated by the growth hormone heregulin (HRG) or 17beta-estradiol (E2) in the presence or absence of tamoxifen. Control was set as non-treated cells.

ORGANISM(S): Homo sapiens

SUBMITTER: Okada Mariko

PROVIDER: S-ECPF-GEOD-21618 | biostudies-other |

REPOSITORIES: biostudies-other

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Project description:Introduction: Although changes in microRNA (miRNA) expression correlate with breast cancer diagnostic markers, comparatively little is known about miRNA regulation by selective estrogen receptor modulators (SERMs), e.g., tamoxifen (TAM), or their role in endocrine-resistance. Methods: A microarray approach was used to identify miRNAs differentially expressed and regulated by 4-hydroxyTAM (4-OHT) in MCF-7/TAM-sensitive versus LY2 TAM/endocrine-resistant human breast cancer cells after 6 h treatment. The expression of specific miRNAs was validated by quantitative, real-time PCR. Control miRNAs and time-course studies showed important gene-, time-, and cell- specific differences in miRNA expression. Results: 97 miRNAs were differentially expressed in MCF-7 versus LY2 cells. Bioinformatic analyses to impute the biological significance of these miRNAs by identifying 36 predicted gene targets of these miRNAs from amongst those reported to be regulated by MCF-7 cells was performed and agreement was found in direction of anticipated regulation for 12 of those putative targets. Among the miRNAs differentially expressed in MCF-7 versus LY2 cells, and that putatively target mRNAs regulated by 4-OHT in MCF-7 cells, are: miRs- 10a, 21, 22, 29a, 93, 125b, 181, 200a, 200b, 200c; 205, 221, and 222. Q-PCR assessment showed agreement with microarray data: miR- 10a, 22, 125b, 181, and 222 are higher in LY2 whereas miR-21 and miR-200a are lower in LY2 than MCF-7. 4-OHT increased miR-10a, miR-21, miR-22, miR-125b, miR-181a, miR-200a, and miR-222 in MCF-7 cells and reduced miR-10a in LY2 cells. E2 reduced the miR-21expression in MCF-7 cells. Treatment with ICI 182,780 revealed that ER suppresses miR-10a, miR-21, miR-22, miR-200a, miR-221, and miR-222 expression in MCF-7 cells. Time-dependent changes in select miRNA expression were observed in control, E2, and 4-OHT-treated MCF-7 cells. ESR1/ERα was significantly lower in LY2 than MCF-7, commensurate with higher let-7 family member, miR-221, and miR-222 expression in LY2. Reflecting inverse association with miR-200 family expression, the expression of ZEB1 was higher in LY2 than MCF-7 cells and concomitantly, E-cadherin expression was absent in LY2 cells indicating that LY2 have undergone epithelial to mesenchymal transition. Conclusions: Our studies identifying miRNAs with opposite expression between the two cell lines, indicate the involvement of these miRNAs in endocrine resistance. The purpose of this experiment is: 1. To identify miRNAs that are regulated (up or down) by 4-OHT in MCF-7 and LY2 cell lines (comparison of values from EtOH versus 4-OHT treated cells). 2. To identify miRNAs that are differentially regulated under basal (EtOH) conditions between MCF-7 and LY2 cell lines. 3. To identify miRNAs that are differentially regulated by 4-OHT in MCF-7 versus LY2 cells.

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Expression profiling of ligand-stimulated wild type and tamoxifen-resistant MCF-7

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