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MicroRNA expression changes associated with specific STAT3 activation

ABSTRACT: Signal transducer and activator of transcription 3 (STAT3) is a critical transcription factor in cancer. However, while the protein-coding target genes of STAT3 have been extensively studied, the microRNA target genes of STAT3 are less understood. MicroRNAs are short, non-coding RNAs that regulate messenger RNAs through translational inhibition and transcript degradation. They have been found to be involved in all aspects of cancer biology. Given the roles of both STAT3 and miRNAs in cancer, the function of STAT3 as a transcription factor, and the dearth of known STAT3 miRNA targets, our goal was to identify novel STAT3 miRNA targets relevant to cancer. To do so, we engineered MCF-10A cells with doxycycline-inducible expression of STAT3C. STAT3C is a constitutively-active mutant version of STAT3. Although STAT3 can be activated by various growth factors and kinases, other pathways can be activated as well, which would confound analysis of the results. Thus, the advantage of STAT3C is that it allowed specific and focused activation of STAT3 alone, and this screen represents the first genome-wide survey of miRNA expression changes associated specifically with STAT3 activity. MCF-10A, a non-transformed breast epithelial cell line, was chosen because STAT3C has been reported to be sufficient to cause their neoplastic transformation. Therefore, we reasoned that analysis of STAT3C’s effects in MCF-10A cells would be especially informative for STAT3-regulated miRNAs relevant to cancer. As a result of our study, we identified previously-known as well as novel miRNA targets of STAT3.

ORGANISM(S): Homo sapiens

PROVIDER: GSE44089 | GEO | 2014/02/05

SECONDARY ACCESSION(S): PRJNA188553

REPOSITORIES: GEO

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Project description:Signal transducer and activator of transcription 3 (STAT3) is a critical transcription factor in cancer. However, while the protein-coding target genes of STAT3 have been extensively studied, the microRNA target genes of STAT3 are less understood. MicroRNAs are short, non-coding RNAs that regulate messenger RNAs through translational inhibition and transcript degradation. They have been found to be involved in all aspects of cancer biology. Given the roles of both STAT3 and miRNAs in cancer, the function of STAT3 as a transcription factor, and the dearth of known STAT3 miRNA targets, our goal was to identify novel STAT3 miRNA targets relevant to cancer. To do so, we engineered MCF-10A cells with doxycycline-inducible expression of STAT3C. STAT3C is a constitutively-active mutant version of STAT3. Although STAT3 can be activated by various growth factors and kinases, other pathways can be activated as well, which would confound analysis of the results. Thus, the advantage of STAT3C is that it allowed specific and focused activation of STAT3 alone, and this screen represents the first genome-wide survey of miRNA expression changes associated specifically with STAT3 activity. MCF-10A, a non-transformed breast epithelial cell line, was chosen because STAT3C has been reported to be sufficient to cause their neoplastic transformation. Therefore, we reasoned that analysis of STAT3C’s effects in MCF-10A cells would be especially informative for STAT3-regulated miRNAs relevant to cancer. As a result of our study, we identified previously-known as well as novel miRNA targets of STAT3. Doxycycline-inducible MCF-10A cells were seeded, and then untreated (grown in standard growth media alone) or treated with 2?g/ml doxycycline for 48hr. Each condition was performed in biological triplicate (labeled A, B, and C), for a total of 6 samples. Total RNA was harvested and submitted to the Dana-Farber Cancer Institute Molecular Diagnostics Laboratory. MicroRNA expression profiling was performed using TaqMan Low-Density Arrays (TLDA), human miRNA version 2.0A and version 3.0B cards (Applied Biosystems).

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.

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/ER? 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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MicroRNA expression changes associated with specific STAT3 activation

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