Selective interactions of Kruppel-like factor 9/basic transcription element-binding protein with progesterone receptor isoforms A and B determine transcriptional activity of progesterone-responsive genes in endometrial epithelial cells

Krüppel-like factor 12 decreases progestin sensitivity in endometrial cancer by inhibiting the progesterone receptor signaling pathway

OBJECTIVE

This study aimed to clarify the mechanism by which Krüppel-like factor 12 (KLF12) affects progesterone sensitivity in endometrial cancer (EC) through the progesterone receptor PGR signaling pathway.

METHODS

The relationship of KLF12 with PGR in EC patients was examined by immunohistochemistry, and the expression of KLF12 and PGR in EC cell lines was detected by real-time PCR and western blotting. Cell proliferation assay, plate clone formation, cell apoptosis assay, and cell cycle analysis were conducted to determine the impact of KLF12 intervention on progesterone therapy. CUT&Tag analysis and the dual-luciferase reporter experiment were used to determine the underlying regulatory effect of KLF12 on the PGR DNA sequence. A subcutaneous xenograft nude mouse model was established to validate the in vivo effect of KLF12 on progesterone sensitivity via PGR expression modulation.

RESULTS

KLF12 demonstrated decreased progesterone sensitivity and a negative correlation with PGR expression in EC tissues. Progesterone sensitivity was increased by KLF12 deficiency through PGR overexpression, a result that could be significantly reversed by PGR downregulation. PGR was identified as a target gene of KLF12, which could directly bind to the PGR promotor region and inhibit its expression.

CONCLUSION

This study is the first to investigate the effect of KLF12 expression on EC cell resistance to progesterone. Our results offer important mechanistic insight into the direct regulation of the PGR promoter region, demonstrating that KLF12 expression strongly suppressed the PGR signaling pathway and, as a result, reduced progesterone sensitivity in EC patients.

Krüppel-like factor 9 (KLF9) links hormone dysregulation and circadian disruption to breast cancer pathogenesis

BACKGROUND

Circadian disruption is an emerging driver of breast cancer (BCa), with epidemiological studies linking shift work and chronic jet lag to increased BCa risk. Indeed, several clock genes participate in the gating of mitotic entry, regulation of DNA damage response, and epithelial-to-mesenchymal transition, thus impacting BCa etiology. Dysregulated estrogen (17β-estradiol, E2) and glucocorticoid (GC) signaling prevalent in BCa may further contribute to clock desynchrony by directly regulating the expression and cycling dynamics of genes comprising the local breast oscillator. In this study, we investigated the tumor suppressor gene, Krüppel-like factor 9 (KLF9), as an important point of crosstalk between hormone signaling and the circadian molecular network, and further examine its functional role in BCa.

METHODS

Through meta-analysis of publicly available RNA- and ChIP-sequencing datasets from BCa tumor samples and cell lines, and gene expression analysis by RT-qPCR and enhancer- reporter assays, we elucidated the molecular mechanism behind the clock and hormone regulation of KLF9. Lentiviral knockdown and overexpression of KLF9 in three distinct breast epithelial cell lines (MCF10A, MCF7 and MDA-MB-231) was generated to demonstrate the role of KLF9 in orthogonal assays on breast epithelial survival, proliferation, apoptosis, and migration.

RESULTS

We determined that KLF9 is a direct GC receptor target in mammary epithelial cells, and that induction is likely mediated through coordinate transcriptional activation from multiple GC-responsive enhancers in the KLF9 locus. More interestingly, rhythmic expression of KLF9 in MCF10A cells was abolished in the highly aggressive MDA-MB-231 line. In turn, forced expression of KLF9 altered the baseline and GC/E2-responsive expression of several clock genes, indicating that KLF9 may function as a regulator of the core clock machinery. Characterization of the role of KLF9 using complementary cancer hallmark assays in the context of the hormone-circadian axis revealed that KLF9 plays a tumor-suppressive role in BCa regardless of molecular subtype. KLF9 potentiated the anti-tumorigenic effects of GC in E2 receptor + luminal MCF7 cells, while it restrained GC-enhanced oncogenicity in triple-negative MCF10A and MDA-MB-231 cells.

CONCLUSIONS

Taken together, our findings support that dysregulation of KLF9 expression and oscillation in BCa impinges on circadian network dynamics, thus ultimately affecting the BCa oncogenic landscape.

Decreased Krüppel-like factor 4 in adenomyosis impairs decidualization by repressing autophagy in human endometrial stromal cells

Background

Poor decidualization and abnormal autophagy conditions in the endometria of adenomyosis patients have been reported previously. However, the specific regulatory mechanism of decidualization in adenomyosis and its relationship with autophagy levels have not been clarified.

Methods

Endometrial tissues from adenomyosis patients and uteri from an adenomyosis mouse model were collected for the detection of different expression patterns of KLF4 and autophagy markers (LC3-B/LC3-A and Beclin-1) compared with control groups. Human endometrial stromal cells (hESCs) isolated from adenomyosis and control endometrial tissues were employed to elucidate the biological functions of KLF4 in autophagy and decidualization. Gene expression regulation was examined by quantitative real-time PCR (qRT-PCR), western blotting and luciferase reporter assays. In addition, DNA promoter-protein interactions were examined by chromatin immunoprecipitation (ChIP)/PCR assay and avidin–biotin conjugate DNA precipitation (ABCD) assay.

Results

KLF4 expression was decreased in endometrial tissues from adenomyosis patients compared with those from fertile controls, especially in stromal compartments. The opposite results were observed for autophagy marker (LC3-B/LC3-A and Beclin-1) expression. At the same time, KLF4 reversed the poor decidualization of hESCs from adenomyosis patients. In addition, KLF4 could induce hESC decidualization by promoting the autophagy level. Mechanistically, KLF4 bound to a conserved site in the autophagy-related 5 (ATG5) promoter region and promoted ATG5 expression. Similar expression patterns of KLF4 and autophagy markers were detected in adenomyotic mice.

Conclusions

KLF4 overexpression increases the autophagy level of hESCs by transcriptionally promoting ATG5 expression, and abnormally decreased KLF4 in adenomyosis impairs hESC decidualization by repressing autophagy.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12860-022-00425-6.

The role of progesterone receptor isoforms in the myometrium

Myometrial contraction is stringently controlled throughout pregnancy and parturition. Progesterone signaling, effecting through the progesterone receptor (PR), is pivotal in modulating uterine activity. Evidence has shown that two major PR isoforms, PR-A and PR-B, have distinct activities on gene regulation, and the ratio between these isoforms determines the contractility of the myometrium at different gestational stages. Herein, we focus on the regulation of PR activity in the myometrium, especially the differential actions of the two PR isoforms, which maintain uterine quiescence during pregnancy and regulate the switch to a contractile state at the onset of labor. To demonstrate the PR regulatory network and its mechanisms of actions on myometrial activity, we summarized the findings into three parts: Regulation of PR Expression and Isoform Levels, Progesterone Receptor Interacting Factors, and Biological Processes Regulated by Myometrial Progesterone Receptor Isoforms. Recent genomic and epigenomic data, from human specimens and mouse models, are recruited to support the existing knowledge and offer new insights and future directions in myometrial biology.

miR-338-3p blocks TGFβ-induced myofibroblast differentiation through the induction of PTEN

Idiopathic pulmonary fibrosis (IPF) is a chronic interstitial lung disease. The pathogenesis of IPF is not completely understood. However, numerous genes are associated with the development and progression of pulmonary fibrosis, indicating there is a significant genetic component to the pathogenesis of IPF. Epigenetic influences on the development of human disease, including pulmonary fibrosis, remain to be fully elucidated. In this paper, we identify miR-338-3p as a microRNA severely downregulated in the lungs of patients with pulmonary fibrosis and in experimental models of pulmonary fibrosis. Treatment of primary human lung fibroblasts with miR-338-3p inhibits myofibroblast differentiation and matrix protein production. Published and proposed targets of miR-338-3p such as TGFβ receptor 1, MEK/ERK 1/2, Cdk4, and Cyclin D are also not responsible for the regulation of pulmonary fibroblast behavior by miR-338-3p. miR-338-3p inhibits myofibroblast differentiation by preventing TGFβ-mediated downregulation of phosphatase and tensin homolog (PTEN), a known antifibrotic mediator.

An Intact Krüppel-like factor 9 Gene Is Required for Acute Liver Period 1 mRNA Response to Restraint Stress

The clock protein period 1 (PER1) is a central component of the core transcription-translation feedback loop governing cell-autonomous circadian rhythms in animals. Transcription of Per1 is directly regulated by the glucocorticoid (GC) receptor (GR), and Per1 mRNA is induced by stressors or injection of GC. Circulating GCs may synchronize peripheral clocks with the central pacemaker located in the suprachiasmatic nucleus of the brain. Krüppel-like factor 9 (KLF9) is a zinc finger transcription factor that, like Per1, is directly regulated by liganded GR, and it associates in chromatin at clock and clock-output genes, including at Per1. We hypothesized that KLF9 modulates stressor-dependent Per1 transcription. We exposed wild-type (WT) and Klf9 null mice (Klf9-/-) of both sexes to 1 hour restraint stress, which caused similar 2- to 2.5-fold increases in plasma corticosterone (B) in each genotype and sex. Although WT mice of both sexes showed a 2-fold increase in liver Per1 mRNA level after restraint stress, this response was absent in Klf9-/- mice. However, injection of B in WT and Klf9-/- mice induced similar increases in Per1 mRNA. Our findings support that an intact Klf9 gene is required for liver Per1 mRNA responses to an acute stressor, but a possible role for GCs in this response requires further investigation.

Metformin regulation of progesterone receptor isoform-B expression in human endometrial cancer cells is glucose-dependent

Metformin (MET) constitutes the first-line treatment against type 2 diabetes. Growing evidence linking insulin resistance and cancer risk has expanded the therapeutic potential of MET to several cancer types. However, the oncostatic mechanisms of MET are not well understood. MET has been shown to promote the expression of progesterone receptor (PGR) and other antitumor biomarkers in patients with non-diabetic endometrial cancer (EC) and in Ishikawa EC cells cultured in normal glucose (5.5 mM) media. Therefore, the present study aimed to assess the effects of MET on EC cells under conditions simulating diabetes. Ishikawa cells treated with 10 nM 17β-estradiol (E2) and/or 100 µM MET and exposed to normal and high (17.5 mM) concentrations of glucose were evaluated for proliferative and PGR expression status. Under normal glucose conditions, MET attenuated E2-induced cell proliferation and cyclin D1 gene expression, and increased total PGR and PGR-B transcript levels. MET inhibited Ishikawa cell spheroid formation only in the absence of E2 treatment. In E2-treated cells under high glucose conditions, MET showed no effects on cell proliferation and spheroid formation, and increased total PGR but not PGR-B transcript levels. Transfection with Krüppel-like factor 9 small interfering RNA increased PGR-A transcript levels, irrespective of glucose environment. Medroxyprogesterone acetate downregulated PGR-A expression more effectively with metformin under high compared with normal glucose conditions. To evaluate the potential mechanisms underlying the targeting of PGR by MET, E2-treated cells were incubated with MET and the AMPK inhibitor Compound C, or with the AMPK activator 5-aminoimidazole-4-carboxamide ribonucleotide (AICAR), under normal glucose conditions. Compound C abrogated the effects of MET on PGR-B while AICAR increased PGR-B transcript levels, albeit less effectively compared with MET. The present results demonstrate the glucose-dependent effects of MET on PGR-B isoform expression, which may inform the response to progestin therapy in diabetic women with EC.

Metformin Promotes Anti-tumor Biomarkers in Human Endometrial Cancer Cells

Metformin (MET) is increasingly implicated in reducing the incidence of multiple cancer types in patients with diabetes. However, similar effects of MET in non-diabetic women with endometrial cancer (EC) remain unknown. In a pilot study, obese non-diabetic women diagnosed with type 1, grade 1/2 EC, and consenting to participate were randomly assigned to receive MET or no MET (control (CON)) during the pre-surgical window between diagnosis and hysterectomy. Endometrial tumors obtained at surgery (MET, n = 4; CON, n = 4) were analyzed for proliferation (Ki67), apoptosis (TUNEL), and nuclear expression of ERα, PGR, PTEN, and KLF9 proteins in tumor glandular epithelial (GE) and stromal (ST) cells. The percentages of immunopositive cells for PGR and for KLF9 in GE and for PTEN in ST were higher while those for ERα in GE but not ST were lower, in tumors of MET vs. CON patients. The numbers of Ki67- and TUNEL-positive cells in tumor GE and ST did not differ between groups. In human Ishikawa endometrial cancer cells, MET treatment (60 μM) decreased cell numbers and elicited distinct temporal changes in ESR1, KLF9, PGR, PGR-B, KLF4, DKK1, and other tumor biomarker mRNA levels. In the context of reduced KLF9 expression (by siRNA targeting), MET rapidly amplified PGR, PGR-B, and KLF4 transcript levels. Our findings suggest that MET acts directly in EC cells to modify steroid receptor expression and signaling network and may constitute a preventative strategy against EC in high-risk non-diabetic women.

Hypermethylated KLF9 Is An Independent Prognostic Factor For Favorable Outcome In Breast Cancer

Background and objective

Breast cancer (BC) is the most lethal human malignancy and is the leading cause of cancer-associated death in women worldwide. Krüppel-like factor 9 (KLF9) belongs to a family of transcriptional regulators and its role in BC has not been fully investigated.

Method

Data mining was used to analyze BC data from The Cancer Genome Atlas (TCGA) database, which was downloaded using the UCSC Xena browser. The differential expression and methylation level of KLF9 was analyzed in patients with BC and corresponding normal controls enrolled from our hospital. Besides, the correlation of KLF9 methylation and prognosis was explored, and gene set enrichment analysis (GSEA) was conducted to identify the potential signaling pathway of KLF9 involved.

Results

Both TCGA and BC tissues indicated hypermethylation of the KLF9 promoter region in patients with BC compared with normal controls, which might account for the dysregulation of KLF9 in patients with BC. Besides, hypermethylation of KLF9 was detected in patients with estrogen or progesterone receptor-positive and non-triple-negative disease. Further, hypermethylation of KLF9 was demonstrated to be a potential independent biomarker in obtaining favorable outcomes in BC. By GSEA, tumor-associated biological processes and signaling pathway were identified, which indicated that KLF9 might play a vital role in the carcinogenesis of BC.

Conclusion

KFL9 plays an important role in the carcinogenesis of BC through the multiple tumor-associated signaling pathway. The hypermethylation of KLF9 resulted in its reduced expression in BC, while the hypermethylation of KLF9 has potential in the prediction of favorable outcomes in BC.

Serine Threonine Kinase Receptor-Associated Protein Deficiency Impairs Mouse Embryonic Stem Cells Lineage Commitment Through CYP26A1-Mediated Retinoic Acid Homeostasis

Retinoic acid (RA) signaling is essential for the differentiation of embryonic stem cells (ESCs) and vertebrate development. RA biosynthesis and metabolism are controlled by a series of enzymes, but the molecular regulators of these enzymes remain largely obscure. In this study, we investigated the functional role of the WD-domain protein STRAP (serine threonine kinase receptor-associated protein) in the pluripotency and lineage commitment of murine ESCs. We generated Strap knockout (KO) mouse ESCs and subjected them to spontaneous differentiation. We observed that, despite the unchanged characteristics of ESCs, Strap KO ESCs exhibited defects for lineage differentiation. Signature gene expression analyses revealed that Strap deletion attenuated intracellular RA signaling in embryoid bodies (EBs), and exogenous RA significantly rescued this deficiency. Moreover, loss of Strap selectively induced Cyp26A1 expression in mouse EBs, suggesting a potential role of STRAP in RA signaling. Mechanistically, we identified putative Krüppel-like factor 9 (KLF9) binding motifs to be critical in the enhancement of non-canonical RA-induced transactivation of Cyp26A1. Increased KLF9 expression in the absence of STRAP is partially responsible for Cyp26A1 induction. Interestingly, STRAP knockdown in Xenopus embryos influenced anterior-posterior neural patterning and impaired the body axis and eye development during early Xenopus embryogenesis. Taken together, our study reveals an intrinsic role for STRAP in the regulation of RA signaling and provides new molecular insights for ESC fate determination. Stem Cells 2018;36:1368-1379.

Increased Krüppel-like factor 12 in recurrent implantation failure impairs endometrial decidualization by repressing Nur77 expression

BACKGROUND

Decidualization is a prerequisite for successful implantation and the establishment of pregnancy. A critical role of impaired decidualization in subfertility has been established. In human endometrial stromal cells (hESCs), Krüppel-like factor 12 (KLF12) and Nur77 are novel regulators of decidualization. We investigated whether KLF12 impaired the decidualization of hESCs in recurrent implantation failure (RIF) patients.

METHODS

Endometrial tissues and hESCs were collected from RIF patients (n = 34) and fertile controls (n = 30) for in vitro analysis. Primary hESCs isolated from RIF endometrial tissues were used to evaluate the biological functions of KLF12 and Nur77. In addition, their molecular mechanisms were investigated by adenovirus-mediated overexpression. Gene expression regulation was examined by real-time-quantitative PCR (qRT-PCR), immunostaining and luciferase reporter assay. Further, blastocyst-like spheroid (BLS) and blastocyst implantation models were performed to examine the roles of KLF12 and Nur77 during embryo expansion on hESCs.

RESULTS

hESCs from the RIF patients showed a poor decidual response, mainly characterized by decreased decidual prolactin (dPRL) secretion, impaired transformation and limited BLS expansion. In addition, KLF12 expression was increased in endometrial tissues from the RIF patients compared with those from the fertile controls, especially in stromal compartments. The opposite results were observed for Nur77 expression in these tissues. KLF12 repressed hESC decidualization by decreasing Nur77 expression. Mechanistically, KLF12 bound to a conserved site in the Nur77 promoter region. Nur77 overexpression significantly reversed the KLF12-mediated repression of dPRL expression, decidual transformation and BLS/blastocyst expansion.

CONCLUSIONS

KLF12 impairs endometrial decidualization by transcriptionally repressing Nur77, and Nur77 overexpression reverses the poor decidual response of hESCs in RIF patients.

Transcriptional Regulation of CYP2D6 Expression

CYP2D6-mediated drug metabolism exhibits large interindividual variability. Although genetic variations in the CYP2D6 gene are well known contributors to the variability, the sources of CYP2D6 variability in individuals of the same genotype remain unexplained. Accumulating data indicate that transcriptional regulation of CYP2D6 may account for part of CYP2D6 variability. Yet, our understanding of factors governing transcriptional regulation of CYP2D6 is limited. Recently, mechanistic studies of increased CYP2D6-mediated drug metabolism in pregnancy revealed two transcription factors, small heterodimer partner (SHP) and Krüppel-like factor 9, as a transcriptional repressor and an activator, respectively, of CYP2D6. Chemicals that increase SHP expression (e.g., retinoids and activators of farnesoid X receptor) were shown to downregulate CYP2D6 expression in the humanized mice as well as in human hepatocytes. This review summarizes the series of studies on the transcriptional regulation of CYP2D6 expression, potentially providing a basis to better understand the large interindividual variability in CYP2D6-mediated drug metabolism.

High-Fat Diet Promotion of Endometriosis in an Immunocompetent Mouse Model is Associated With Altered Peripheral and Ectopic Lesion Redox and Inflammatory Status

Endometriosis is a benign gynecological condition that causes considerable morbidity due to associated infertility, debilitating pelvic pain and inflammatory dysfunctions. Diet is a highly modifiable risk factor for many chronic diseases, but its contribution to endometriosis has not been extensively investigated, due partly to the paradoxical inverse association between obesity and disease incidence. Nevertheless, chronic exposure to dietary high-fat intake has been linked to greater systemic inflammation and oxidative stress, both features of women with endometriosis. Here, we evaluated the effects of a high-fat diet (HFD) (45% fat kcal) on endometriosis progression using an immunocompetent mouse model where ectopic lesion incidence was induced in wild-type recipients by ip administration of endometrial fragments from transcription factor Krüppel-like factor 9-null donor mice. We show that HFD significantly increased ectopic lesion numbers in recipient mice with no significant weight gain and modifications in systemic ovarian steroid hormone and insulin levels, relative to control diet-fed (17% fat kcal) mice. HFD promotion of lesion establishment was associated with reductions in stromal estrogen receptor 1 isoform and progesterone receptor expression, increased F4/80-positive macrophage infiltration, higher stromal but not glandular epithelial proliferation, and enhanced expression of proinflammatory and prooxidative stress pathway genes. Lesion-bearing HFD-fed mice also displayed higher peritoneal fluid TNFα and elevated local and systemic redox status than control diet-fed counterparts. Our results suggest that HFD intake exacerbates endometriosis outcome in the absence of ovarian dysfunction and insulin resistance in mice and warrants further consideration with respect to clinical management of endometriosis progression and recurrence in nonobese patients.

Asperosaponin VI promotes progesterone receptor expression in decidual cells via the notch signaling pathway

Recurrent spontaneous abortion (RSA) is a common clinical condition, but its reasons remain unknown in 37-79% of the affected women. The steroid hormone progesterone (P4) is an integral mediator of early pregnancy events, exerting its effects via the progesterone receptor (PR). Dipsaci Radix (DR) has long been used for treating gynecological diseases in Chinese medicine, while its molecular mechanisms and active ingredients are still unclear. We report here the progesterone-like effects of the alcohol extraction and Asperosaponin VI from DR in primary decidual cells and HeLa cell line. We first determined the safe concentration of Asperosaponin VI in the cells with MTT assay and then found by using dual luciferase reporter and Western blotting that Asperosaponin VI significantly increased PR expression. Moreover, we explored the mechanisms of action of the DR extracts and Asperosaponin VI, and the results showed that they could activate Notch signaling, suggesting that they may function by promoting decidualization.

A Mechanism to Enhance Cellular Responsivity to Hormone Action: Krüppel-Like Factor 9 Promotes Thyroid Hormone Receptor-β Autoinduction During Postembryonic Brain Development

Thyroid hormone (TH) receptor (TR)-β (trb) is induced by TH (autoinduced) in Xenopus tadpoles during metamorphosis. We previously showed that Krüppel-like factor 9 (Klf9) is rapidly induced by TH in the tadpole brain, associates in chromatin with the trb upstream region in a developmental stage and TH-dependent manner, and forced expression of Klf9 in the Xenopus laevis cell line XTC-2 accelerates and enhances trb autoinduction. Here we investigated whether Klf9 can promote trb autoinduction in tadpole brain in vivo. Using electroporation-mediated gene transfer, we transfected plasmids into premetamorphic tadpole brain to express wild-type or mutant forms of Klf9. Forced expression of Klf9 increased baseline trb mRNA levels in thyroid-intact but not in goitrogen-treated tadpoles, supporting that Klf9 enhances liganded TR action. As in XTC-2 cells, forced expression of Klf9 enhanced trb autoinduction in tadpole brain in vivo and also increased TH-dependent induction of the TR target genes klf9 and thbzip. Consistent with our previous mutagenesis experiments conducted in XTC-2 cells, the actions of Klf9 in vivo required an intact N-terminal region but not a functional DNA binding domain. Forced expression of TRβ in tadpole brain by electroporation-mediated gene transfer increased baseline and TH-induced TR target gene transcription, supporting a role for trb autoinduction during metamorphosis. Our findings support that Klf9 acts as an accessory transcription factor for TR at the trb locus during tadpole metamorphosis, enhancing trb autoinduction and transcription of other TR target genes, which increases cellular responsivity to further TH action on developmental gene regulation programs.

Impact of physiological, pathological and environmental factors on the expression and activity of human cytochrome P450 2D6 and implications in precision medicine

With only 1.3-4.3% in total hepatic CYP content, human CYP2D6 can metabolize more than 160 drugs. It is a highly polymorphic enzyme and subject to marked inhibition by a number of drugs, causing a large interindividual variability in drug clearance and drug response and drug-drug interactions. The expression and activity of CYP2D6 are regulated by a number of physiological, pathological and environmental factors at transcriptional, post-transcriptional, translational and epigenetic levels. DNA hypermethylation and histone modifications can repress the expression of CYP2D6. Hepatocyte nuclear factor-4α binds to a directly repeated element in the promoter of CYP2D6 and thus regulates the expression of CYP2D6. Small heterodimer partner represses hepatocyte nuclear factor-4α-mediated transactivation of CYP2D6. GW4064, a farnesoid X receptor agonist, decreases hepatic CYP2D6 expression and activity while increasing small heterodimer partner expression and its recruitment to the CYP2D6 promoter. The genotypes are key determinants of interindividual variability in CYP2D6 expression and activity. Recent genome-wide association studies have identified a large number of genes that can regulate CYP2D6. Pregnancy induces CYP2D6 via unknown mechanisms. Renal or liver diseases, smoking and alcohol use have minor to moderate effects only on CYP2D6 activity. Unlike CYP1 and 3 and other CYP2 members, CYP2D6 is resistant to typical inducers such as rifampin, phenobarbital and dexamethasone. Post-translational modifications such as phosphorylation of CYP2D6 Ser135 have been observed, but the functional impact is unknown. Further functional and validation studies are needed to clarify the role of nuclear receptors, epigenetic factors and other factors in the regulation of CYP2D6.

Endometriosis Located Proximal to or Remote From the Uterus Differentially Affects Uterine Gene Expression

The mechanisms that lead to the altered uterine gene expression in women with endometriosis are poorly understood. Are these changes in gene expression mediated by proximity to endometriotic lesions or is endometriosis a systemic disease where the effect is independent of proximity to the uterus? To answer this question, we created endometriosis in a murine model either in the peritoneal cavity (proximal) or at a subcutaneous remote site (distal). The expression of several genes that are involved in endometrial receptivity (homeobox A10 [Hoxa10], homeobox A11 [Hoxa11], insulin-like growth factor binding protein 1 [Igfbp1], Kruppel-like factor 9 [Klf9], and progesterone receptor [Pgr]) was measured in the eutopic endometrium of mice transplanted with either proximal or distal endometriosis lesions. Decreased expression of Hoxa10, Igfbp1, Klf9, and total Pgr genes was observed in the eutopic endometrium of mice with peritoneal endometriosis. In the mice with distal lesions, overall expression of these genes was not as severely affected, however, Igfbp1 expression was similarly decreased and the effect on Pgr was more pronounced. Endometriosis does have a systemic effect that varies with distance to the end organ. However, even remote disease selectively and profoundly alters the expression of genes such as Pgr. This is the first controlled experiment demonstrating that endometriosis is not simply a local peritoneal disease. Selective alteration of genes critical for endometrial receptivity and endometriosis propagation may be systemic. Similarly, systemic effects of endometriosis on other organs may also be responsible for the widespread manifestations of the disease.

Extensive shift in placental transcriptome profile in preeclampsia and placental origin of adverse pregnancy outcomes

One in five pregnant women suffer from gestational complications, prevalently driven by placental malfunction. Using RNASeq, we analyzed differential placental gene expression in cases of normal gestation, late-onset preeclampsia (LO-PE), gestational diabetes (GD) and pregnancies ending with the birth of small-for-gestational-age (SGA) or large-for-gestational-age (LGA) newborns (n = 8/group). In all groups, the highest expression was detected for small noncoding RNAs and genes specifically implicated in placental function and hormonal regulation. The transcriptome of LO-PE placentas was clearly distinct, showing statistically significant (after FDR) expressional disturbances for hundreds of genes. Taqman RT-qPCR validation of 45 genes in an extended sample (n = 24/group) provided concordant results. A limited number of transcription factors including LRF, SP1 and AP2 were identified as possible drivers of these changes. Notable differences were detected in differential expression signatures of LO-PE subtypes defined by the presence or absence of intrauterine growth restriction (IUGR). LO-PE with IUGR showed higher correlation with SGA and LO-PE without IUGR with LGA placentas. Whereas changes in placental transcriptome in SGA, LGA and GD cases were less prominent, the overall profiles of expressional disturbances overlapped among pregnancy complications providing support to shared placental responses. The dataset represent a rich catalogue for potential biomarkers and therapeutic targets.

Krüppel-Like Factor 13 Deficiency in Uterine Endometrial Cells Contributes to Defective Steroid Hormone Receptor Signaling but Not Lesion Establishment in a Mouse Model of Endometriosis

Krüppel-like Factor (KLF) 13 and the closely related KLF9 are members of the Sp/KLF family of transcription factors that have collectively emerged as essential regulators of tissue development, differentiation, proliferation, and programmed cell death. Steroid hormone-responsive tissues express multiple KLFs that are linked to progesterone receptor (PGR) and estrogen receptor (ESR) actions either as integrators or as coregulators. Endometriosis is a chronic disease characterized by progesterone resistance and dysregulated estradiol signaling; nevertheless, distinct KLF members' contributions to endometriosis remain largely undefined. We previously demonstrated promotion of ectopic lesion establishment by Klf9 null endometrium in a mouse model of endometriosis. Here we evaluated whether KLF13 loss of expression in endometrial cells may equally contribute to lesion formation. KLF13 transcript levels were lower in the eutopic endometria of women with versus women without endometriosis at menstrual midsecretory phase. In wild-type (WT) mouse recipients intraperitoneally administered WT or Klf13 null endometrial fragments, lesion incidence did not differ with donor genotype. No differences were noted for lesion volume, number, proliferation status, and apoptotic index as well. Klf13 null lesions displayed reduced total PGR and ESR1 (RNA and immunoreactive protein) and altered expression of several PGR and ESR1 target genes, relative to WT lesions. Unlike for Klf9 null lesions, changes in transcript levels for PGR-A, ESR1, and Notch/Hedgehog-associated pathway components were not observed for Klf13 null lesions. Results demonstrate lack of a causative relationship between endometrial KLF13 deficiency and lesion establishment in mice, and they support the broader participation of multiple signaling pathways, besides those mediated by steroid receptors, in the pathology of endometriosis.

The Krüppel-like factors in female reproductive system pathologies

Female reproductive tract pathologies arise largely from dysregulation of estrogen and progesterone receptor signaling, leading to aberrant cell proliferation, survival, and differentiation. The signaling pathways orchestrated by these nuclear receptors are complex, require the participation of many nuclear proteins serving as key binding partners or targets, and involve a range of paracrine and autocrine regulatory circuits. The members of the Krüppel-like factor (KLF) family of transcription factors are ubiquitously expressed in reproductive tissues and have been increasingly implicated as critical co-regulators and integrators of steroid hormone actions. Herein, we explore the involvement of KLF family members in uterine pathology, describe their currently known molecular mechanisms, and discuss their potential as targets for therapeutic intervention.

MicroRNA-181a is involved in the regulation of human endometrial stromal cell decidualization by inhibiting Krüppel-like factor 12

BACKGROUND

The transformation of endometrium into decidua is essential for normal implantation of the blastocyst. However, the post-transcriptional regulation and the miRNAs involved in decidualization remain poorly understood. Here, we examined microRNA-181a (miR-181a) expression in decidualized human endometrial stromal cell (hESC). In addition, we investigated the functional effect of miR-181a on hESC decidualization in vitro.

METHODS

Quantitative real-time PCR (qRT-PCR) was used to detect the profile of miR-181a in decidualized hESC. qRT-PCR, enzyme-linked fluorescent assay, and immunofluorescence assay were performed to investigate decidualization marker genes' expression after enhancing or inhibition of miR-181a expression in hESC. Luciferase reporter assay, western blotting, qRT-PCR, and immunofluorescence assay were carried out to identify the relationship between miR-181a and Krüppel-like factor 12 (KLF12).

RESULTS

miR-181a expression levels increased dramatically in hESC treated with 8-Br-cAMP and MPA. Increased miR-181a expression promoted hESC decidualization-related gene expression and morphological transformation; conversely, inhibition of miR-181a expression compromised hESC decidualization in vitro. Further analysis confirmed that miR-181a interacted with the 3' untranslated region of the transcription factor KLF12 and down-regulated KLF12 at the transcriptional and translational levels. KLF12 overexpression abolished miR-181a-induced decidualization.

CONCLUSIONS

Our findings suggest that miR-181a plays a functionally important role in human endometrial stromal cell decidualization in vitro by inhibiting KLF12.

Prolonged pregnancy in women is associated with attenuated myometrial expression of progesterone receptor co-regulator Krüppel-like Factor 9

CONTEXT

Late-term pregnancy may lead to maternal and neonatal morbidity and mortality. Mice null for the progesterone receptor co-regulator Krüppel-like Factor 9 (KLF9) exhibit delayed parturition and increased incidence of neonatal deaths.

OBJECTIVE

Our aim is to evaluate the contribution of myometrial KLF9 to human parturition.

DESIGN

Myometrial biopsies were obtained from women with term (>37 to ≤41 wk) and late-term (>41 wk) pregnancies during cesarean delivery and assessed for gene and protein expression. Human myometrial cells transfected with nontargeting or KLF9 small interfering RNAs (siRNA) were treated with the progesterone antagonist RU486 and analyzed for pro-inflammatory chemokine/cytokine gene expression.

SETTING

The study took place in a University-affiliated tertiary care hospital and University research laboratory.

PATIENTS

Term patients (n = 8) were in spontaneous active labor whereas late-term patients (n = 5) were either in or were induced to active labor, prior to elective cesarean delivery.

OUTCOME MEASURES

Steroid hormone receptor, contractility, and inflammation-associated gene expression in myometrial biopsies and in siKLF9-transfected, RU486-treated human myometrial cells was associated with KLF9 expression levels.

RESULTS

Myometrium from women with late-term pregnancy showed lower KLF9, total PGR, and PGR-A/PGR-B isoform expression. Transcript levels of select chemokines/cytokines were up- (CSF3, IL1, IL12A, TGFB2) and down- (CCL3, CCL5, CXCL1, CXCL5, IL15) regulated in late-term relative to term myometrium. Knock-down of KLF9 expression in RU486-treated human myometrial cells modified the expression of PGR and labor-associated cytokines, relative to control siRNA-treated cells.

CONCLUSIONS

Myometrial KLF9 may contribute to the onset of human parturition through its regulation of PGR expression and inflammatory signaling networks.

Krüppel-like factor 9 inhibits glioma cell proliferation and tumorigenicity via downregulation of miR-21

Krüppel-like factors (KLFs) are zinc finger-containing transcription factors that play key roles in the regulation of differentiation and development as well as biological processes central to the development of malignancies. Increasing evidence indicates that Krüppel-like factor 9 (KLF9) plays a critical role in regulating tumorigenesis. However, the biological role and molecular mechanism of KLF9 in glioma progression remain unclear. Herein, we found that KLF9 expression was strongly reduced in gliomas. Reduced KLF9 expression promoted glioma cell proliferation. Importantly, re-constitution of KLF9 expression inhibited glioma cell proliferation and tumor growth in vivo. Furthermore, we determined that KLF9 interacted with the miR-21 promoter, leading to suppression of miR-21 expression and cell cycle arrest. Taken together, our findings indicate a novel mechanism for KLF function in tumorigenesis and may also suggest new targets for clinical intervention in human cancer.

Krüppel-like factor 9 promotes hepatic cytochrome P450 2D6 expression during pregnancy in CYP2D6-humanized mice

Cytochrome P450 2D6 (CYP2D6), a major drug-metabolizing enzyme, is responsible for metabolism of approximately 25% of marketed drugs. Clinical evidence indicates that metabolism of CYP2D6 substrates is increased during pregnancy, but the underlying mechanisms remain unclear. To identify transcription factors potentially responsible for CYP2D6 induction during pregnancy, a panel of genes differentially expressed in the livers of pregnant versus nonpregnant CYP2D6-humanized (tg-CYP2D6) mice was compiled via microarray experiments followed by real-time quantitative reverse-transcription polymerase chain reaction(qRT-PCR) verification. As a result, seven transcription factors-activating transcription factor 5 (ATF5), early growth response 1 (EGR1), forkhead box protein A3 (FOXA3), JUNB, Krüppel-like factor 9 (KLF9), KLF10, and REV-ERBα-were found to be up-regulated in liver during pregnancy. Results from transient transfection and promoter reporter gene assays indicate that KLF9 itself is a weak transactivator of CYP2D6 promoter but significantly enhances CYP2D6 promoter transactivation by hepatocyte nuclear factor 4 (HNF4α), a known transcriptional activator of CYP2D6 expression. The results from deletion and mutation analysis of CYP2D6 promoter activity identified a KLF9 putative binding motif at -22/-14 region to be critical in the potentiation of HNF4α-induced transactivation of CYP2D6. Electrophoretic mobility shift assays revealed a direct binding of KLF9 to the putative KLF binding motif. Results from chromatin immunoprecipitation assay showed increased recruitment of KLF9 to CYP2D6 promoter in the livers of tg-CYP2D6 mice during pregnancy. Taken together, our data suggest that increased KLF9 expression is in part responsible for CYP2D6 induction during pregnancy via the potentiation of HNF4α transactivation of CYP2D6.

Feed-forward transcriptional programming by nuclear receptors: regulatory principles and therapeutic implications

Nuclear receptors (NRs) are widely targeted to treat a range of human diseases. Feed-forward loops are an ancient mechanism through which single cell organisms organize transcriptional programming and modulate gene expression dynamics, but they have not been systematically studied as a regulatory paradigm for NR-mediated transcriptional responses. Here, we provide an overview of the basic properties of feed-forward loops as predicted by mathematical models and validated experimentally in single cell organisms. We review existing evidence implicating feed-forward loops as important in controlling clinically relevant transcriptional responses to estrogens, progestins, and glucocorticoids, among other NR ligands. We propose that feed-forward transcriptional circuits are a major mechanism through which NRs integrate signals, exert temporal control over gene regulation, and compartmentalize client transcriptomes into discrete subunits. Implications for the design and function of novel selective NR ligands are discussed.

Krüppel-like factors are effectors of nuclear receptor signaling

Binding of steroid and thyroid hormones to their cognate nuclear receptors (NRs) impacts virtually every aspect of postembryonic development, physiology and behavior, and inappropriate signaling by NRs may contribute to disease. While NRs regulate genes by direct binding to hormone response elements in the genome, their actions may depend on the activity of other transcription factors (TFs) that may or may not bind DNA. The Krüppel-like family of transcription factors (KLF) is an evolutionarily conserved class of DNA-binding proteins that influence many aspects of development and physiology. Several members of this family have been shown to play diverse roles in NR signaling. For example, KLFs (1) act as accessory transcription factors for NR actions, (2) regulate expression of NR genes, and (3) as gene products of primary NR response genes function as key players in NR-dependent transcriptional networks. In mouse models, deletion of different KLFs leads to aberrant transcriptional and physiological responses to hormones, underscoring the importance of these proteins in the regulation of hormonal signaling. Understanding the functional relationships between NRs and KLFs will yield important insights into mechanisms of NR signaling. In this review we present a conceptual framework for understanding how KLFs participate in NR signaling, and we provide examples of how these proteins function to effect hormone action.

Revisiting the roles of progesterone and allopregnanolone in the nervous system: resurgence of the progesterone receptors

Progesterone is commonly considered as a female reproductive hormone and is well-known for its role in pregnancy. It is less well appreciated that progesterone and its metabolite allopregnanolone are also male hormones, as they are produced in both sexes by the adrenal glands. In addition, they are synthesized within the nervous system. Progesterone and allopregnanolone are associated with adaptation to stress, and increased production of progesterone within the brain may be part of the response of neural cells to injury. Progesterone receptors (PR) are widely distributed throughout the brain, but their study has been mainly limited to the hypothalamus and reproductive functions, and the extra-hypothalamic receptors have been neglected. This lack of information about brain functions of PR is unexpected, as the protective and trophic effects of progesterone are much investigated, and as the therapeutic potential of progesterone as a neuroprotective and promyelinating agent is currently being assessed in clinical trials. The little attention devoted to the brain functions of PR may relate to the widely accepted assumption that non-reproductive actions of progesterone may be mainly mediated by allopregnanolone, which does not bind to PR, but acts as a potent positive modulator of γ-aminobutyric acid type A (GABA(A) receptors. The aim of this review is to critically discuss effects of progesterone on the nervous system via PR, and of allopregnanolone via its modulation of GABA(A) receptors, with main focus on the brain.

Krüppel-like factors in cancer

Krüppel-like factors (KLFs) are a family of DNA-binding transcriptional regulators with diverse and essential functions in a multitude of cellular processes, including proliferation, differentiation, migration, inflammation and pluripotency. In this Review, we discuss the roles and regulation of the 17 known KLFs in various cancer-relevant processes. Importantly, the functions of KLFs are context dependent, with some KLFs having different roles in normal cells and cancer, during cancer development and progression and in different cancer types. We also identify key questions for the field that are likely to lead to important new translational research and discoveries in cancer biology.

Oestrogen and progesterone action on endometrium: a translational approach to understanding endometrial receptivity

Embryo attachment and implantation is critical to successful reproduction of all eutherian mammals, including humans; a better understanding of these processes could lead to improved infertility treatments and novel contraceptive methods. Experience with assisted reproduction, especially oocyte donation cycles, has established that despite the diverse set of hormones produced by the ovary in a cycle-dependent fashion, the sequential actions of only two of them, oestrogen and progesterone, are sufficient to prepare a highly receptive endometrium in humans. Further investigation on the endometrial actions of these two hormones is currently providing significant insight into the implantation process in women, strongly suggesting that an abnormal response to progesterone underlies infertility in some patients.

A novel role of the Sp/KLF transcription factor KLF11 in arresting progression of endometriosis

Endometriosis affects approximately 10% of young, reproductive-aged women. Disease associated pelvic pain; infertility and sexual dysfunction have a significant adverse clinical, social and financial impact. As precise disease etiology has remained elusive, current therapeutic strategies are empiric, unfocused and often unsatisfactory. Lack of a suitable genetic model has impaired further translational research in the field. In this study, we evaluated the role of the Sp/KLF transcription factor KLF11/Klf11 in the pathogenesis of endometriosis. KLF11, a human disease-associated gene is etiologically implicated in diabetes, uterine fibroids and cancer. We found that KLF11 expression was diminished in human endometriosis implants and further investigated its pathogenic role in Klf11-/- knockout mice with surgically induced endometriotic lesions. Lesions in Klf11-/- animals were large and associated with prolific fibrotic adhesions resembling advanced human disease in contrast to wildtype controls. To determine phenotype-specificity, endometriosis was also generated in Klf9-/- animals. Unlike in Klf11-/- mice, lesions in Klf9-/- animals were neither large, nor associated with a significant fibrotic response. KLF11 also bound to specific elements located in the promoter regions of key fibrosis-related genes from the Collagen, MMP and TGF-β families in endometrial stromal cells. KLF11 binding resulted in transcriptional repression of these genes. In summary, we identify a novel pathogenic role for KLF11 in preventing de novo disease-associated fibrosis in endometriosis. Our model validates in vivo the phenotypic consequences of dysregulated Klf11 signaling. Additionally, it provides a robust means not only for further detailed mechanistic investigation but also the ability to test any emergent translational ramifications thereof, so as to expand the scope and capability for treatment of endometriosis.

Krüppel-like factor 12 negatively regulates human endometrial stromal cell decidualization

Members of the KLFs family of transcription factors play roles in maternal endometrium development during embryo implantation. However, the specific role of KLF12 in endometrium development has not yet been described. In this study, we showed that KLF12 expression in human endometrial stromal cells (HESCs) was significantly decreased after decidualization stimulated by 8-Br-cAMP and medroxyprogesterone acetate (MPA). The adenovirus-mediated overexpression of KLF12 in HESCs significantly repressed the expression and secretion of decidualization biomarker genes and their products decidual prolactin (PRL) and insulin-like growth factor binding protein-1 (IGFBP-1) induced by 8-Br-cAMP and MPA. Moreover, CHIP and luciferase reporter assays demonstrated that KLF12 bound to a CAGTGGG element within the decidual prolactin promoter and decreased decidual PRL promoter (dPRL/-2000Luc) activation in a sequence-specific manner. Taken together, these findings suggest KLF12 is a negative regulator of human endometrial stromal cell decidualization.

Klf9 is necessary and sufficient for Purkinje cell survival in organotypic culture

During their phase of developmental programmed cell death (PCD), neurons depend on target-released trophic factors for survival. After this period, however, they critically change as their survival becomes target-independent. The molecular mechanisms underlying this major transition remain poorly understood. Here, we investigated, which transcription factors (TFs) might be responsible for the closure of PCD. We used Purkinje cells as a model since their PCD is restricted to the first postnatal week in the mouse cerebellum. Transcriptome analysis of Purkinje cells during or after PCD allowed the identification of Krüppel like factor 9 (Klf9) as a candidate for PCD closure, given its high increase of expression at the end of the 1st postnatal week. Klf9 function was tested in organotypic cultures, through lentiviral vector-mediated manipulation of Klf9 expression. In absence of trophic factors, the Purkinje cell survival rate is of 40%. Overexpression of Klf9 during PCD dramatically increases the Purkinje cell survival rate from 40% to 88%, whereas its down-regulation decreases it to 14%. Accordingly, in organotypic cultures of Klf9 knockout animals, Purkinje cell survival rate is reduced by half as compared to wild-type mice. Furthermore, the absence of Klf9 could be rescued by Purkinje cell trophic factors, Insulin growth factor-1 and Neurotrophin3. Altogether, our results ascribe a clear role of Klf9 in Purkinje cell survival. Thus, we propose that Klf9 might be a key molecule involved in turning off the phase of Purkinje PCD.

The reproductive phenotype of mice null for transcription factor Krüppel-like factor 13 suggests compensatory function of family member Krüppel-like factor 9 in the peri-implantation uterus

The ovarian hormones estrogen and progesterone promote uterine receptivity and successful pregnancy through their cognate receptors functioning in concert with context-dependent nuclear coregulators. Previously, we showed that the transcription factor Krüppel-like factor (KLF) 9 is a progesterone receptor (PGR) coactivator in the uterus and that mice null for Klf9 exhibit subfertility and reduced progesterone sensitivity. The highly related family member KLF13 displays increased expression in uteri of pregnant and nonpregnant Klf9 null mice and similarly regulates PGR-mediated transactivation in endometrial stromal cells. However, a uterine phenotype with loss of Klf13 has not been reported. In the present study, we demonstrate that Klf13 deficiency in mice did not compromise female fertility and pregnancy outcome. Klf13 null females had litter sizes, numbers of implanting embryos, uterine morphology, and ovarian steroid hormone production comparable to those of wild-type (WT) counterparts. Further, pregnant WT and Klf13 null females at Day Postcoitum (DPC) 3.5 had similar uterine Pgr, estrogen receptor, and Wnt-signaling component transcript levels. Nuclear levels of KLF9 were higher in Klf13 null than in WT uteri at DPC 3.5, albeit whole-tissue KLF9 protein and transcript levels did not differ between genotypes. The lack of a similar induction of nuclear KLF9 levels in uteri of virgin Klf13((-/-)) mice relative to WT uteri was associated with lower stromal PGR expression. In differentiating human endometrial stromal cells, coincident KLF9/KLF13 knockdown by small interfering RNA targeting reduced decidualization-associated PRL expression, whereas KLF9 and KLF13 knockdowns alone reduced transcript levels of WNT4 and BMP2, respectively. Results suggest that KLF9 and KLF13 functionally compensate in peri-implantation uterus for pregnancy success.

The regulation of embryo implantation and endometrial decidualization by progesterone receptor signaling

During the early stages of pregnancy, fertilized embryos must attach to the uterine epithelium, invade into the underlying uterine stroma, and the stroma must then differentiate in a process termed decidualization in order for a successful pregnancy to be initiated. The steroid hormone progesterone (P4) is an integral mediator of these early pregnancy events, exerting its effects via the progesterone receptor (PR). Insights gained from the use of mouse models and genomic profiling has identified many of the key molecules enlisted by PR to execute the paradigm of early pregnancy. This review describes several of the molecules through which the PR exerts its pleiotropic effects including ligands, receptors, chaperones, signaling proteins and transcription factors. Understanding these molecules and their concatenation is of vital importance to our ability to clinically treat reproductive health problems like infertility and endometriosis.

Progesterone receptors, their isoforms and progesterone regulated transcription

This review discusses mechanisms by which progesterone receptors (PR) regulate transcription. We examine available data in different species and tissues regarding: (1) regulation of PR levels; and (2) expression profiling of progestin-regulated genes by total PRs, or their PRA and PRB isoforms. (3) We address current views about the composition of progesterone response elements, and postulate that PR monomers acting through "half-site" elements are common, entailing cooperativity with neighboring DNA-bound transcription factors. (4) We summarize transcription data for multiple progestin-regulated promoters as directed by total PR, or PRA vs. PRB. We conclude that current models and methods used to study PR function are problematical, and recommend that future work employ cells and receptors appropriate to the species, focusing on analyses of the effects of endogenous receptors targeting endogenous genes in native chromatin.

Krüppel-like factors KLF2 and 6 and Ki-67 are direct targets of zoledronic acid in MCF-7 cells

Bisphosphonates (BP) are used for the treatment of osteoporosis and bone metastases due to breast and prostate cancer. Recent clinical studies indicated a benefit in survival and tumor relapse with the supportive treatment of breast cancer using zoledronic acid (ZA), thus stimulating the debate about its putative anti-tumor activity in vivo. MCF-7 breast cancer cells were treated for 3 h (pulse treatment) and 72 h (permanent treatment) with ZA, and apoptosis rates and cell viability, defined as ATP content, were determined after 72 h. Permanent and pulse stimulation with ZA inhibited the viability of MCF-7 cells, which could partly be rescued by atorvastatin (Ator) pre-treatment but not by geranylgeranyl pyrophosphate (GGPP) co-treatment. Microarray analysis of ZA treated MCF-7 cells identified genes of the mevalonate pathway as significantly upregulated, which was verified by qPCR. Additionally the putative tumor suppressors krüppel-like factor 2 and 6 (KLF2 and KLF6) were markedly upregulated, while the classical proliferation marker Ki-67 was clearly downregulated. The expression of all three genes was confirmed by qPCR on mRNA level and by immunocytochemistry or Western blot staining. Expression of target genes were also analyzed in other breast (MDA-MB-231, BT-20, ZR75-1, T47D) and prostate (LNCaP, PC3) cancer cell lines by qPCR. ZA responsiveness of KLF2, KLF6 and Ki-67 could be verified in PC3 and T47D cells, KLF6 responsiveness in LNCaP and KLF2 responsiveness in MDA-MB-231 and BT-20 cells. Here we demonstrate in the apoptosis insensitive MCF-7 cell line a remarkable impact of ZA exposure on cell viability and on the regulation of putative tumor suppressors of the KLF family. The molecular mechanism involved might be the accumulation of isopentenyl pyrophosphate (IPP) and ApppI, since we could partly rescue the ZA effect by Ator pre-treatment and GGPP co-treatment. These data should stimulate further research into both the role of the mevalonate pathway and the accumulation of pyrophosphate compounds like ApppI in tumorigenesis and differentiation and their potential apart from the inhibition of mitochondrial ADP/ATP translocase and apoptosis, since such effects might well be responsible for the adjuvant ZA treatment benefit of patients suffering from breast cancer.

Krüppel-like factor 9 and progesterone receptor coregulation of decidualizing endometrial stromal cells: implications for the pathogenesis of endometriosis

CONTEXT

Endometriosis is characterized by progesterone resistance and associated with infertility. Krüppel-like factor 9 (KLF9) is a progesterone receptor (PGR)-interacting protein, and mice null for Klf9 are subfertile. Whether loss of KLF9 expression contributes to progesterone resistance of eutopic endometrium of women with endometriosis is unknown.

OBJECTIVE

The aims were to investigate 1) KLF9 expression in eutopic endometrium of women with and without endometriosis, 2) effects of attenuated KLF9 expression on WNT-signaling component expression and on WNT inhibitor Dickkopf-1 promoter activity in human endometrial stromal cells (HESC), and 3) PGR and KLF9 coregulation of the stromal transcriptome network.

METHODS

Transcript levels of KLF9, PGR, and WNT signaling components were measured in eutopic endometrium of women with and without endometriosis. Transcript and protein levels of WNT signaling components in HESC transfected with KLF9 and/or PGR small interfering RNA were analyzed by quantitative RT-PCR and Western blot. KLF9 and PGR coregulation of Dickkopf-1 promoter activity was evaluated using human Dickkopf-1-luciferase promoter/reporter constructs and by chromatin immunoprecipitation. KLF9 and PGR signaling networks were analyzed by gene expression array profiling.

RESULTS

Eutopic endometrium from women with endometriosis had reduced expression of KLF9 mRNA together with those of PGR-B, WNT4, WNT2, and DKK1. KLF9 and PGR were recruited to the DKK1 promoter and modified each other's transactivity. In HESC, KLF9 and PGR coregulated components of the WNT, cytokine, and IGF gene networks that are implicated in endometriosis and infertility.

CONCLUSION

Loss of KLF9 coregulation of endometrial stromal PGR-responsive gene networks may underlie progesterone resistance in endometriosis.

Krüppel-like factor 9 loss-of-expression in human endometrial carcinoma links altered expression of growth-regulatory genes with aberrant proliferative response to estrogen

Endometrial cancer is the most commonly diagnosed female genital tract malignancy. Krüppel-like factor 9 (KLF9), a member of the evolutionarily conserved Sp family of transcription factors, is expressed in uterine stroma and glandular epithelium, where it affects cellular proliferation, differentiation, and apoptosis. Deregulated expression of a number of Sp proteins has been associated with multiple types of human tumors, but a role for KLF9 in endometrial cancer development and/or progression is unknown. Here, we evaluated KLF9 expression in endometrial tumors and adjacent uninvolved endometrium of women with endometrial carcinoma. KLF9 mRNA and protein levels were lower in endometrial tumors coincident with decreased expression of family member KLF4 and growth-regulators FBJ murine osteosarcoma viral oncogene homolog (FOS) and myelocytomatosis viral oncogene homolog (MYC) and with increased expression of telomerase reverse transcriptase (TERT) and the chromatin-modifying enzymes DNA methyltransferase 1 (DNMT1) and histone deacetylase 3 (HDAC3). Expression of estrogen receptor alpha (ESR1) and the tumor-suppressor phosphatase and tensin homolog deleted in chromosome 10 (PTEN) did not differ between tumor and normal tissue. The functional relevance of attenuated KLF9 expression in endometrial carcinogenesis was further evaluated in the human endometrial carcinoma cell line Ishikawa by siRNA targeting. KLF9 depletion resulted in loss of normal cellular response to the proliferative effects of estrogen concomitant with reductions in KLF4 and MYC and with enhancement of TERT and ESR1 gene expression. Silencing of KLF4 did not mimic the effects of silencing KLF9 in Ishikawa cells. We suggest that KLF9 loss-of-expression accompanying endometrial carcinogenesis may predispose endometrial epithelial cells to mechanisms of escape from estrogen-mediated growth regulation, leading to progression of established neoplasms.

Krüppel-like family of transcription factor 9, a differentiation-associated transcription factor, suppresses Notch1 signaling and inhibits glioblastoma-initiating stem cells

Tumor-initiating stem cells (alternatively called cancer stem cells, CSCs) are a subpopulation of tumor cells that plays unique roles in tumor propagation, therapeutic resistance, and tumor recurrence. It is becoming increasingly important to understand the molecular signaling that regulates the self-renewal and differentiation of CSCs. Transcription factors are critical for the regulation of normal and neopolastic stem cells. Here, we examined the expression and function of the Krüppel-like family of transcription factors (KLFs) in human glioblastoma (GBM)-derived neurosphere lines and low-passage primary GBM-derived neurospheres that are enriched for tumor-initiating stem cells. We identify KLF9 as a relatively unique differentiation-induced transcription factor in GBM-derived neurospheres. KLF9 is shown to induce neurosphere cell differentiation, inhibit neurosphere formation, and inhibit neurosphere-derived xenograft growth in vivo. We also show that KLF9 regulates GBM neurosphere cells by binding to the Notch1 promoter and suppressing Notch1 expression and downstream signaling. Our results show for the first time that KLF9 has differentiating and tumor-suppressing functions in tumor-initiating stem cells.

Mammalian Krüppel-like factors in health and diseases

The Krüppel-like factor (KLF) family of transcription factors regulates diverse biological processes that include proliferation, differentiation, growth, development, survival, and responses to external stress. Seventeen mammalian KLFs have been identified, and numerous studies have been published that describe their basic biology and contribution to human diseases. KLF proteins have received much attention because of their involvement in the development and homeostasis of numerous organ systems. KLFs are critical regulators of physiological systems that include the cardiovascular, digestive, respiratory, hematological, and immune systems and are involved in disorders such as obesity, cardiovascular disease, cancer, and inflammatory conditions. Furthermore, KLFs play an important role in reprogramming somatic cells into induced pluripotent stem (iPS) cells and maintaining the pluripotent state of embryonic stem cells. As research on KLF proteins progresses, additional KLF functions and associations with disease are likely to be discovered. Here, we review the current knowledge of KLF proteins and describe common attributes of their biochemical and physiological functions and their pathophysiological roles.

Functional differentiation of uterine stromal cells involves cross-regulation between bone morphogenetic protein 2 and Kruppel-like factor (KLF) family members KLF9 and KLF13

The inability of the uterine epithelium to enter a state of receptivity for the embryo to implant is a significant underlying cause of early pregnancy loss. We previously showed that mice null for the progesterone receptor (PGR)-interacting protein Krüppel-like factor (KLF) 9 are subfertile and exhibit reduced uterine progesterone sensitivity. KLF9 expression is high in predecidual stroma, undetectable in decidua, and enhanced in uteri of mice with conditional ablation of bone morphogenetic protein 2 (BMP2). Given the individual importance of KLF9 and BMP2 for implantation success, we hypothesized that the establishment of uterine receptivity involves KLF9 and BMP2 functional cross-regulation. To address this, we used early pregnant wild-type and Klf9 null mice and KLF9 small interfering RNA-transfected human endometrial stromal cells (HESCs) induced to differentiate under standard conditions. Loss of KLF9 in mice and HESCs enhanced BMP2 expression, whereas recombinant BMP2 treatment of HESCs attenuated KLF9 mRNA levels. IGFBP1 and KLF9-related KLF13 expression were positively associated with BMP2 and inversely associated with KLF9. Prolonged, but not short-term, knockdown of KLF9 in HESCs reduced IGFBP1 expression. Mouse uterine Igfbp1 expression was similarly reduced with Klf9 ablation. PGR-A and PGR-B expression were positively associated with KLF9 in predecidual HESCs but not decidualizing HESCs. KLF13 knockdown attenuated BMP2 and PGR-B and abrogated BMP2-mediated inhibition of KLF9 expression. Results support cross-regulation among BMP2, KLF9, and KLF13 to maintain progesterone sensitivity in stromal cells undergoing differentiation and suggest that loss of this regulatory network compromises establishment of uterine receptivity and implantation success.

HOXA10 inhibits Kruppel-like factor 9 expression in the human endometrial epithelium

Kruppel-like factor 9 (KLF9) is a zinc finger transcription factor that regulates estrogen and progesterone action by modulating the activity of progesterone receptor (PGR). The transition from proliferative to secretory endometrial epithelium involves loss of estrogen receptor/PGR expression and loss of direct response to sex steroids. HOXA10 partially mediates progesterone responsiveness in the endometrium. Here, we demonstrate that HOXA10 directly regulates KLF9 in endometrial epithelial cells and not in stromal cells. Immunohistochemistry performed on endometrial tissue obtained from normal, reproductive-age women revealed that KLF9 expression was decreased in the secretory phase of the menstrual cycle compared to the proliferative phase. In vitro, HOXA10 transfection of human endometrial epithelial cells (Ishikawa), but not stromal cells (HESC), resulted in a greater than 50% decrease in KLF9 mRNA and protein expression. Reporter constructs driven by the KLF9 promoter were repressed by cotransfection with HOXA10. Electrophoretic mobility shift assay was used to demonstrate direct binding of HOXA10 to the KLF9 promoter. Targeted mutation of the HOXA10-binding site in the KLF9 promoter resulted in loss of HOXA10 binding and loss of repression by HOXA10 in reporter assays. HOXA10 directly and selectively repressed KLF9 expression in endometrial epithelial cells. HOXA10 repression of KLF9 likely contributes to the loss of sex steroid responsiveness in secretory-phase endometrial epithelium.

Response of adult mouse uterus to early disruption of estrogen receptor-alpha signaling is influenced by Krüppel-like factor 9

Inappropriate early exposure of the hormone-responsive uterus to estrogenic compounds is associated with increased risk for adult reproductive diseases including endometrial cancers. While the dysregulation of estrogen receptor-alpha (ESR1) signaling is well acknowledged to mediate early events in tumor initiation, mechanisms contributing to sustained ESR1 activity later in life and leading to induction of oncogenic pathways remain poorly understood. We had shown previously that the transcription factor Krüppel-like factor 9 (KLF9) represses ESR1 expression and activity in Ishikawa endometrial glandular epithelial cells. We hypothesized that KLF9 functions as a tumor suppressor, and that loss of its expression enhances ESR1 signaling. Here, we evaluated the contribution of KLF9 to early perturbations in uterine ESR1 signaling pathways elicited by the administration of synthetic estrogen diethylstilbestrol (DES) to wild-type (WT) and Klf9 null (KO) mice on postnatal days (PNDs) 1-5. Uterine tissues collected at PND84 were subjected to histological, immunological, and molecular analyses. Compared with WT mice, KO mice demonstrated larger endometrial glands and lower endometrial gland numbers; DES exposure exacerbated these differences. Loss of KLF9 expression resulted in increased glandular ESR1 immunoreactivity with DES, without effects on serum estradiol levels. Quantitative RT-PCR analyses indicated altered expression of uterine genes commonly dysregulated in endometrial cancers (Akt1, Mmp9, Slpi, and Tgfbeta1) and of those involved in growth regulation (Fos, Myc, Tert, and Syk), with loss of Klf9, alone or in concert with DES. Our data support a molecular network between KLF9 and ESR1 in the uterus, and suggest that silencing of KLF9 may contribute to endometrial dysfunctions initiated by aberrant estrogen action.

The emerging role of Krüppel-like factors in endocrine-responsive cancers of female reproductive tissues

Krüppel-like factors (KLFs), of which there are currently 17 known protein members, belong to the specificity protein (Sp) family of transcription factors and are characterized by the presence of Cys(2)/His(2) zinc finger motifs in their carboxy-terminal domains that confer preferential binding to GC/GT-rich sequences in gene promoter and enhancer regions. While previously regarded to simply function as silencers of Sp1 transactivity, many KLFs are now shown to be relevant to human cancers by their newly identified abilities to mediate crosstalk with signaling pathways involved in the control of cell proliferation, apoptosis, migration, and differentiation. Several KLFs act as tumor suppressors and/or oncogenes under distinct cellular contexts, underscoring their prognostic potential for cancer survival and outcome. Recent studies suggest that a number of KLFs can influence steroid hormone signaling through transcriptional networks involving steroid hormone receptors and members of the nuclear receptor family of transcription factors. Since inappropriate sensitivity or resistance to steroid hormone actions underlies endocrine-related malignancies, we consider the intriguing possibility that dysregulation of expression and/or activity of KLF members is linked to the pathogenesis of endometrial and breast cancers. In this review, we focus on recently described mechanisms of actions of several KLFs (KLF4, KLF5, KLF6, and KLF9) in cancers of the mammary gland and uterus. We suggest that understanding the mode of actions of KLFs and their functional networks may lead to the development of novel therapeutics to improve current prospects for cancer prevention and cure.