Project description:Heat shock factor 1 (HSF1) is a key regulator of transcriptional responses to proteotoxic stress. It has been recently linked to signaling of estrogen via ESR1. To study the cooperation of HSF1 and ESR1 in the transcriptional response to estrogen, we established estrogen receptor (ER)-positive breast cancer cell lines with reduced HSF1 levels using specific shRNA or CRISPR/Cas9 approach. HSF1 deficiency led to the inhibition of the mitogenic effect of estrogen in MCF7 and T47D cells. RNA-seq analyses revealed that the stimulatory effect of E2 on the transcriptome was smaller in HSF1-deficient MCF7 cells. This could partially result from the higher basal expression of E2-dependent genes in these cells as a consequence of the enhanced binding of unliganded ESR1 to chromatin, which was revealed by ChIP-seq analyses. Thus, we postulate that some fraction of ESR1 could be released from the inhibitory complex with HSP90 and gain transcriptional competence without E2-stimulation.
Project description:Heat shock factor 1 (HSF1) is a key regulator of transcriptional responses to proteotoxic stress. It has been recently linked to signaling of estrogen via ESR1. To study the cooperation of HSF1 and ESR1 in the transcriptional response to estrogen, we established estrogen receptor (ER)-positive breast cancer cell lines with reduced HSF1 levels using specific shRNA or CRISPR/Cas9 approach. HSF1 deficiency led to the inhibition of the mitogenic effect of estrogen in MCF7 and T47D cells. RNA-seq analyses revealed that the stimulatory effect of E2 on the transcriptome was smaller in HSF1-deficient MCF7 cells. This could partially result from the higher basal expression of E2-dependent genes in these cells as a consequence of the enhanced binding of unliganded ESR1 to chromatin, which was revealed by ChIP-seq analyses. Thus, we postulate that some fraction of ESR1 could be released from the inhibitory complex with HSP90 and gain transcriptional competence without E2-stimulation.
Project description:Heat shock factor 1 (HSF1) is a key regulator of transcriptional responses to proteotoxic stress. It has been recently linked to signaling of estrogen via ESR1. To study the cooperation of HSF1 and ESR1 in the transcriptional response to estrogen, we established estrogen receptor (ER)-positive breast cancer cell lines with reduced HSF1 levels using specific shRNA or CRISPR/Cas9 approach. HSF1 deficiency led to the inhibition of the mitogenic effect of estrogen in MCF7 and T47D cells. RNA-seq analyses revealed that the stimulatory effect of E2 on the transcriptome was smaller in HSF1-deficient MCF7 cells. This could partially result from the higher basal expression of E2-dependent genes in these cells as a consequence of the enhanced binding of unliganded ESR1 to chromatin, which was revealed by ChIP-seq analyses. Thus, we postulate that some fraction of ESR1 could be released from the inhibitory complex with HSP90 and gain transcriptional competence without E2-stimulation.
Project description:Heat shock factor 1 (HSF1), a key regulator of transcriptional responses to proteotoxic stress, was linked to estrogen (E2) signaling through estrogen receptor α (ERα). We found that an HSF1 deficiency may decrease ERα level, attenuate the mitogenic action of E2, counteract E2-stimulated cell scattering, and reduce adhesion to collagens and cell motility in ER-positive breast cancer cells. The stimulatory effect of E2 on the transcriptome is largely weaker in HSF1-deficient cells, in part due to the higher basal expression of E2-dependent genes, which correlates with the enhanced binding of unliganded ERα to chromatin in such cells. HSF1 and ERα can cooperate directly in E2-stimulated regulation of transcription, and HSF1 potentiates the action of ERα through a mechanism involving chromatin reorganization. Furthermore, HSF1 deficiency may increase the sensitivity to hormonal therapy (4-hydroxytamoxifen) or CDK4/6 inhibitors (palbociclib). Analyses of data from The Cancer Genome Atlas database indicate that HSF1 increases the transcriptome disparity in ER-positive breast cancer and can enhance the genomic action of ERα. Moreover, only in ER-positive cancers an elevated HSF1 level is associated with metastatic disease.
Project description:Heat-shock factor 1 (HSF1) is the master transcriptional regulator of the cellular response to heat and a wide variety of other stressors. We previously reported that HSF1 promotes the survival and proliferation of malignant cells. At this time, however, the clinical and prognostic significance of HSF1 in cancer is unknown. To address this issue breast cancer samples from 1,841 participants in the Nurses' Health Study were scored for levels of nuclear HSF1. Associations of HSF1 status with clinical parameters and survival outcomes were investigated by Kaplan-Meier analysis and Cox proportional hazard models. The associations were further delineated by Kaplan-Meier analysis using publicly available mRNA expression data. Our results show that nuclear HSF1 levels were elevated in ?80% of in situ and invasive breast carcinomas. In invasive carcinomas, HSF1 expression was associated with high histologic grade, larger tumor size, and nodal involvement at diagnosis (P < 0.0001). By using multivariate analysis to account for the effects of covariates, high HSF1 levels were found to be independently associated with increased mortality (hazards ratio: 1.62; 95% confidence interval: 1.21-2.17; P < 0.0013). This association was seen in the estrogen receptor (ER)-positive population (hazards ratio: 2.10; 95% confidence interval: 1.45-3.03; P < 0.0001). In public expression profiling data, high HSF1 mRNA levels were also associated with an increase in ER-positive breast cancer-specific mortality. We conclude that increased HSF1 is associated with reduced breast cancer survival. The findings indicate that HSF1 should be evaluated prospectively as an independent prognostic indicator in ER-positive breast cancer. HSF1 may ultimately be a useful therapeutic target in cancer.
