The mechanisms and biological implications of coordinated receptor tyrosine kinase coactivation remain poorly appreciated. Epidermal growth factor receptor (EGFR) and c-Met are frequently coexpressed ...in cancers, including those associated with hepatocyte growth factor (HGF) overexpression, such as malignant astrocytoma. In a previous analysis of the HGF-induced transcriptome, we found that two EGFR agonists, transforming growth factor-alpha and heparin-binding epidermal growth factor-like growth factor (HB-EGF), are prominently up-regulated by HGF in human glioma cells. We now report that stimulating human glioblastoma cells with recombinant HGF induces biologically relevant EGFR activation. EGFR phosphorylation at Tyr(845) and Tyr(1068) increased 6 to 24 h after cell stimulation with HGF and temporally coincided with the induction of transforming growth factor-alpha (~5-fold) and HB-EGF (~23-fold) expression. Tyr(845) and Tyr(1068) phosphorylation, in response to HGF, was inhibited by cycloheximide and actinomycin D, consistent with a requirement for DNA transcription and RNA translation. Specifically, blocking HB-EGF binding to EGFR with the antagonist CRM197 inhibited HGF-induced EGFR phosphorylation by 60% to 80% and inhibited HGF-induced S-G(2)-M transition. CRM197 also inhibited HGF-induced anchorage-dependent cell proliferation but had no effect on HGF-mediated cytoprotection. These findings establish that EGFR can be activated with functional consequences by HGF as a result of EGFR ligand expression. This transcription-dependent cross-talk between the HGF receptor c-Met and EGFR expands our understanding of receptor tyrosine kinase signaling networks and may have considerable consequences for oncogenic mechanisms and cancer therapeutics.
The progesterone receptor (PR) plays roles in normal mammary development and breast cancer formation, where it may exert both stimulatory and inhibitory actions. Previously, the breast cancer ...susceptibility gene product BRCA1 was found to interact with and inhibit the transcriptional activity of estrogen receptor-α. In this study, we found that exogenous wild-type BRCA1 inhibited the activity of the PR in transient transfection assays utilizing a mouse mammary tumor virus-Luc reporter. Wild-type BRCA1 inhibited the activity of endogenous PR in human breast cancer cells (T47D and MCF-7) and inhibited the activity of exogenous PR-A, PR-B, and PR-A plus PR-B isoforms. On the other hand, knockdown of endogenous BRCA1 using small interfering RNA enhanced the progesterone-stimulated activity of the PR by about 4-fold. We documented an in vivo association of the endogenous BRCA1 with PR isoforms A and B and a direct in vitro interaction between BRCA1 and PR, which was partially mapped. Whereas down-regulation of the coactivator p300 contributes to the BRCA1-mediated repression of estrogen receptor-α, this mechanism does not contribute to inhibition of PR activity, because exogenous p300 did not rescue the BRCA1 repression of PR activity. The BRCA1-PR interaction has functional consequences. Thus, we showed that BRCA1 inhibits the expression of various endogenous progesterone-responsive genes and inhibits progesterone-stimulated proliferation of T47D cells. Finally, exogenous progesterone caused an exaggerated proliferative response in the mammary glands of mice harboring a mammary-targeted conditional deletion of the full-length isoform of Brca1. These findings suggest that BRCA1 regulates the activity of progesterone, a major hormone of pregnancy that may also participate in mammary carcinogenesis.
Previously, we reported that BRCA1 strongly represses the transcriptional activity of estrogen receptor-α (ER-α) in human breast and prostate cancer cells but only weakly inhibits ER-α in cervical ...cancer cells. We now report that introduction of the human papillomavirus E7 or E6 oncogenes into human papillomavirus-negative cells rescues the BRCA1 repression of ER-α activity and that the E7 and E6 oncoproteins interact directly with BRCA1 in vitro and associate with BRCA1 in vivo in cultured cells. This interaction involves at least two contact points on BRCA1, one within an N-terminal site shown previously to interact with ER-α and the other in a C-terminal region of BRCA1 containing the first BRCA1 C-terminal domain. Point mutations within the zinc finger domains of E7 and E6 inactivated the binding to the N terminus of BRCA1 and reduced their ability to rescue BRCA1 inhibition of ER-α. E6 and E7 also antagonized the ability of BRCA1 to inhibit c-Myc E-box-mediated transactivation and human telomerase reverse transcriptase promoter activity, in a manner dependent upon the zinc finger domains. Finally, the ability of E6 and E7 to antagonize BRCA1 did not involve proteolytic degradation of BRCA1. These findings suggest functional interactions of BRCA1 with E7 and E6. The potential significance of these findings is discussed.
The cyclin D1 gene is frequently overexpressed in human breast cancer and is capable of inducing mammary tumorigenesis when overexpressed in transgenic mice. The BRCA1 breast tumor susceptibility ...gene product inhibits breast cancer cellular growth and the activity of several transcription factors. Herein, cyclin D1 antagonized BRCA1-mediated repression of estrogen receptor alpha (ERalpha)-dependent gene expression. Cyclin D1 repression of BRCA1 function was mediated independently of its cyclin-dependent kinase, retinoblastoma protein, or p160 (SRC-1) functions in human breast and prostate cancer cells. In vitro, cyclin D1 competed with BRCA1 for ERalpha binding. Cyclin D1 and BRCA1 were both capable of binding ERalpha in a common region of the ERalpha hinge domain. A novel domain of cyclin D1, predicted to form a helix-loop-helix structure, was required for binding to ERalpha and for rescue of BRCA1-mediated ERalpha transcriptional repression. In chromatin immunoprecipitation assays, 17beta-estradiol (E2) enhanced ERalpha and cyclin D1 recruitment to an estrogen response element (ERE). Cyclin D1 expression enhanced ERalpha recruitment to an ERE. E2 reduced BRCA1 recruitment and BRCA1 expression inhibited E2-induced ERalpha recruitment at 12 hours. Cyclin D1 expression antagonized BRCA1 inhibition of ERalpha recruitment to an ERE, providing a mechanism by which cyclin D1 antagonizes BRCA1 function at an ERE. As cyclin D1 abundance is regulated by oncogenic and mitogenic signals, the antagonism of the BRCA1-mediated ERalpha repression by cyclin D1 may contribute to the selective induction of BRCA1-regulated target genes.
Objective: To evaluate the efficacy of empagliflozin combined with sacubitril/valsartan in treating hypertensive patients with heart failure (HF), focusing on its effects on blood pressure ...variability (BPV) and cardiac function. Methods: This retrospective study included 101 patients with hypertension and heart failure with reduced ejection fraction treated at Baoji High-Tech Hospital from October 2021 to October 2023. Patients were divided into two groups: an observation group (n=51), treated with both empagliflozin and sacubitril/valsartan, and a control group (n=50), treated with sacubitril/valsartan alone. We compared the therapeutic effects, BPV (including 24-hour, daytime, and nighttime systolic and diastolic BPV), cardiac function indicators, levels of N-terminal pro-brain natriuretic peptide (NT-proBNP) and cardiac troponin I (cTnI) before and after treatment, and the incidence of adverse reactions between the groups. Independent risk factors affecting treatment efficacy were also analyzed. Results: The total effective rate of treatment in the observation group was significantly higher than in the control group (P<0.05). Both groups showed reductions in daytime and nighttime systolic and diastolic BPV after treatment, with the observation group displaying more pronounced improvements (all P<0.05). Enhancements in cardiac ultrasound measurements, NT-proBNP levels, and cTnI levels were more significant in the observation group compared to the control group post-treatment (both P<0.05). There was no significant difference in the incidence of adverse reactions during treatment between the two groups (P>0.05). Age and comorbid diabetes were identified as independent risk factors for poor prognosis, while treatment with empagliflozin combined with sacubitril/valsartan was a protective factor. Conclusion: Empagliflozin combined with sacubitril/valsartan significantly enhances treatment efficacy in hypertensive patients with heart failure, effectively improves cardiac function and BPV, and demonstrates good safety.
Abstract The application of shape memory alloy (SMA) actuated soft grippers is limited by their slow recovery speed. In order to further expand their application range, as one of the solutions to ...address this limitation, this paper proposes a fast actuated soft gripper based on SMA wire active heat dissipation and elastic rib combination to meet the rapid actuation and recovery. The structure primarily consists of a heat dissipation module capable of winding SMA wire and a soft structure resembling a scorpion tail with embedded supper elastic SMA wire. The geometric structure model, dynamics and SMA constitutive model and finite element model of the soft gripper are established, and the lateral deformation of soft bionic scorpion tail end is analyzed through simulations and experiments. In addition, the force in designed soft gripper tip and its ability to grasp different objects are also studied through experiments. The results show that the addition of a cooling fan increased the recovery rate by about 25%, and the force in soft bionic scorpion tail end can reach about 0.12 N. The designed soft gripper can successfully grasp objects with different softness, shape, size and weight. It lays a theoretical foundation and technical support for the development of soft grippers actuated by SMA in the future.
Loss of full-length Brca1 in mammary epithelial cells of the mouse mammary tumor virus (MMTV)-Cre Brca1 conditional exon 11 deletion mouse model results in the development of mammary adenocarcinomas ...with similar genetic changes to those found in human BRCA1-mutation-related breast cancers. We used this experimental model to evaluate the chemopreventive effect of tamoxifen on the development of mammary preneoplasia and adenocarcinoma. No protective effects of tamoxifen administration on mammary cancer development were found. Instead, tamoxifen treatment significantly increased rates of mammary epithelial cell proliferation and the prevalence of mammary hyperplasia at 6 months of age. Tamoxifen-exposed mice developed adenocarcinomas at younger ages than control mice and a higher percentage of mice developed adenocarcinomas by 12 months of age. Both whole mouse and tissue culture cell models were used to test if loss of full-length Brca1 was associated with a relative increase in the agonist activity of tamoxifen. Tamoxifen induced increased ductal growth in MMTV-Cre Brca1 conditional mice compared to wild type. Estrogen receptor alpha (ERalpha) expression was downregulated in the tamoxifen-induced hyperplasias. Reducing BRCA1 levels in MCF-7 cells using siRNA resulted in a relative increase in the agonist activity of tamoxifen. Results suggest a model of mammary cancer progression in which loss of full-length Brca1 altered the agonist/antagonist activity of tamoxifen, resulting in tamoxifen-induced mammary epithelial cell proliferation with subsequent loss of ERalpha expression and development of ERalpha-negative hyperplasias and adenocarcinomas.
Purpose We previously identified small molecules that fit into a BRCA1-binding pocket within estrogen receptor-alpha (ERalpha), mimic the ability of BRCA1 to inhibit ERalpha activity ...("BRCA1-mimetics"), and overcome antiestrogen resistance. One such compound, the hydrochloride salt of NSC35446 ("NSC35446.HCl"), also inhibited the growth of antiestrogen-resistant LCC9 tumor xenografts. The purpose of this study was to investigate the down-stream effects of NSC35446.HCl and its mechanism of action. Methods Here, we studied antiestrogen-resistant (LCC9, T47DCO, MCF-7/RR, LY2), ERalpha-negative (MDA-MB-231, HCC1806, MDA-MB-468), and antiestrogen-sensitive (MCF-7) cell lines. Techniques utilized include RNA-seq, qRT-PCR, cell growth analysis, cell-cycle analysis, Western blotting, luciferase reporter assays, TUNEL assays, in silico analysis of the IKKB gene, and ChIP assays. Results SC35446.HCl inhibited proliferation and induced apoptosis in antiestrogen-resistant LCC9, T47DCO, MCF-7/RR, and LY2 cells but not in ERalpha-negative breast cancer cell lines. IKKB (IKKbeta, IKBKB), an upstream activator of NF-kappaB, was identified as a BRCA1-mimetic-regulated gene based on an RNA-seq analysis. NSC35446.HCl inhibited IKKB, IKKA, and IKKG/NEMO mRNA and protein expression in LCC9 cells. NSC35446.HCl also inhibited NF-kappaB activity and expression of NF-kappaB target genes. Insilico analysis of the IKKB promoter identified nine estrogen response element (ERE) half-sites and one ERE-like full-site. ChIP assays revealed that ERalpha was recruited to the ERE-like full-site and five of the nine half-sites and that ERalpha recruitment was inhibited by NSC35446.HCl in LCC9 and T47DCO cells. Conclusions These studies identify functional EREs in the IKKB promoter and identify IKKB as an ERalpha and NSC35446.HCl-regulated gene, and they suggest that NF-kappaB and IKKB, which were previously linked to antiestrogen resistance, are targets for NSC35446.HCl in reversing antiestrogen resistance.
BRCA1 regulation of transcription Rosen, Eliot M.; Fan, Saijun; Ma, Yongxian
Cancer letters,
05/2006, Letnik:
236, Številka:
2
Journal Article
Recenzirano
BRCA1, a tumor suppressor gene on chromosome 17q21, was identified in 1994 based on its linkage to hereditary breast and ovarian cancer syndromes. The BRCA1 gene encodes a 220
kDa nuclear ...phosphoprotein. Studies aimed at elucidating the mechanisms of its tumor suppressor activity have revealed, in part, that BRCA1 participates in the DNA damage response and acts to maintain the integrity of the genome. This activity is generic and does not account for the propensity of
BRCA1 mutation carriers to develop specific tumor types rather than a broad spectrum of cancers. In addition to genome maintenance, BRCA1 has been found to broadly regulate gene transcription, even though it is not itself a sequence-specific DNA-binding transcription factor. The ability of BRCA1 to function as a coregulator of transcription may underlie some of its tumor suppressor activity and may explain the tissue-specific nature of this activity. This review will focus on how BRCA1 selectively regulates transcription and how this regulatory function may relate to tumor suppression.
Inherited mutations of the breast cancer susceptibility gene BRCA1 confer a high risk for breast cancer development. The 300RXKK and 266KXK motifs have been identified previously as sites for ...acetylation of the estrogen receptor-α (ER-α), and 302K was also found to be a site for BRCA1-mediated mono-ubiquitination of ER-α in vitro. Here we show that ER-α proteins with single or double lysine mutations of these motifs (including K303R, a cancer-associated mutant) are resistant to inhibition by BRCA1, even though the mutant ER-α proteins retain the ability to bind to BRCA1. We also found that BRCA1 overexpression reduced and knockdown increased the level of acetylated wild-type ER-α, without changing the total ER-α protein level. Increased acetylation of ER-α due to BRCA1 small interfering RNA was dependent upon phosphatidylinositol 3-kinase/Akt signaling and on up-regulation of the coactivator p300. In addition, using an in vitro acetylation assay, we found that in vitro-translated wild-type BRCA1 but not a cancer-associated point mutant (C61G) inhibited p300-mediated acetylation of ER-α. Furthermore, BRCA1 overexpression increased the levels of mono-ubiquitinated ER-α protein, and a BRCA1 mutant that is defective for ubiquitin ligase activity but retains other BRCA1 functions (I26A) did not ubiquitinate ER-α or repress its activity in vivo. Finally, ER-α proteins with mutations of the 300RXKK or 266KXK motifs showed modest or no BRCA1-induced ubiquitination. We propose a model in which BRCA1 represses ER-α activity, in part, by regulating the relative degree of acetylation vs. ubiquitination of ER-α.
In this report, we show that BRCA1 inhibits estrogen receptor activity, in part, by inhibiting its acetylation and increasing its ubiquitination.
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