Cell Fate Determination Factor Research Articles

Lack of Musashi-2 induces type IIa fiber-dominated muscle atrophy.

Skeletal muscle is a highly plastic tissue, adapting its structure and metabolism in response to diverse conditions such as contractile activity, nutrients, and diseases. Finding a novel master regulator of muscle mass and quality will provide new therapeutic targets for the prevention and treatment of muscle weakness. Musashi is an RNA-binding protein that dynamically regulates protein expression; it was originally discovered as a cell fate determination factor in neural cells. Here, we report that Musashi-2 (Msi2) is dominantly expressed in slow-type muscle fibers, fibers characterized by high metabolism and endurance. Msi2 knockout (KO) mice exhibited a decrease in both soleus myofiber size and number compared to control mice. Biochemical and histological analyses revealed that type IIa fibers, which are of the fast type but have high metabolic capacity, were decreased in Msi2 KO mice. The contraction force of isolated soleus muscle was lower in KO mice, and the expression of the metabolic proteins, cytochrome c oxidase and myoglobin, was also decreased in KO muscle. Our data demonstrate the critical role of Msi2 in the maintenance of normal fiber-type composition and metabolism.

Nuclear poly(A) binding protein 1 (PABPN1) mediates zygotic genome activation-dependent maternal mRNA clearance during mouse early embryonic development.

An embryo starts its life with maternal mRNA clearance, which is crucial for embryonic development. The elimination of maternal transcripts occurs by the joint action of two pathways: the maternally encoded mRNA decay pathway (M-decay) and the zygotic genome activation (ZGA)-dependent pathway (Z-decay). However, zygotic factors triggering maternal mRNA decay in early mammalian embryos remain largely unknown. In this study, we identified the zygotically encoded nuclear poly(A) binding protein 1 (PABPN1) as a factor required for maternal mRNA turnover, with a previously undescribed cytoplasmic function. Cytoplasmic PABPN1 docks on 3′-uridylated transcripts, downstream of terminal uridylyl transferases TUT4 and TUT7, and recruits 3′-5′ exoribonuclease DIS3L2 to its targets, facilitating maternal mRNA decay. Pabpn1-knockout in mice resulted in preimplantation stage mortality due to early developmental arrest at the morula stage. Maternal mRNAs to be eliminated via the Z-decay pathway failed to be removed from Pabpn1-depleted embryos. Furthermore, PABPN1-mediated Z-decay is essential for major ZGA and regulates the expression of cell fate-determining factors in mouse preimplantation embryos. This study revealed an unforeseen cytoplasmic function of PABPN1 coupled with early embryonic development, characterized the presence of a zygotic destabilizer of maternal mRNA, and elucidated the Z-decay process mechanisms, which potentially contribute to human fertility.

Transcriptome-wide association analysis identifies DACH1 as a kidney disease risk gene that contributes to fibrosis.

Genome-wide association studies (GWAS) for kidney function identified hundreds of risk regions; however, the causal variants, target genes, cell types, and disease mechanisms remain poorly understood. Here, we performed transcriptome-wide association studies (TWAS), summary Mendelian randomization, and MetaXcan to identify genes whose expression mediates the genotype effect on the phenotype. Our analyses identified Dachshund homolog 1 (DACH1), a cell-fate determination factor. GWAS risk variant was associated with lower DACH1 expression in human kidney tubules. Human and mouse kidney single-cell open chromatin data (snATAC-Seq) prioritized estimated glomerular filtration rate (eGFR) GWAS variants located on an intronic regulatory region in distal convoluted tubule cells. CRISPR-Cas9-mediated gene editing confirmed the role of risk variants in regulating DACH1 expression. Mice with tubule-specific Dach1 deletion developed more severe renal fibrosis both in folic acid and diabetic kidney injury models. Mice with tubule-specific Dach1 overexpression were protected from folic acid nephropathy. Single-cell RNA sequencing, chromatin immunoprecipitation, and functional analysis indicated that DACH1 controls the expression of cell cycle and myeloid chemotactic factors, contributing to macrophage infiltration and fibrosis development. In summary, integration of GWAS, TWAS, single-cell epigenome, expression analyses, gene editing, and functional validation in different mouse kidney disease models identified DACH1 as a kidney disease risk gene.

Correlation between single nucleotide polymorphisms of DACH1 gene microRNA binding site and susceptibility of patients with endometrial cancer

Objective:To study the relationship between single nucleotide polymorphism (SNP) of the 3 primer untranslated region (UTR) variants of the cell fate determination factor Dachshund 1(DACH1) gene and the susceptibility of patients with endometrial cancer (EC).Methods:Genomic DNA was extracted from the peripheral venous blood of 235 EC patients and 235 healthy controls, and the DACH1 gene rs9285274, rs9529895, rs17088351, and rs59352399 loci were analyzed by Sanger sequencing. Patients progression-free survival (PFS) was recorded after 3 years follow-up from October 2016 to October 2019.Results:Carriers of the C allele of the DACH1 gene rs9529895 locus had a significantly lower risk for EC than T allele carriers (odds ratio = 0.56, 95%confidence interval: 0.38–0.84, P < .01). The correlation between DACH1 gene rs9529895 locus SNP and the risk for EC was affected by age, body mass index, smoking, drinking, and diabetes. Age, and rs9285274, rs9529895, and rs59352399 locus SNP were the best models for predicting the risk for EC. The accuracy rate was 57.02%, and the Cross-validation Consistency was 10/10 (x2 = 4.33, P = .04). The DACH1 gene rs9529895 locus C allele (TC+CC) carriers had significantly higher PFS than the TT genotype carriers (P = .04). The DACH1 gene was expressed in decreased amounts in the cancer tissues of EC patients, and the DACH1 mRNA expression level in the CC genotype, TC genotype, and TT genotype of rs9529895 locus was also decreased (P = .02).Conclusion:DACH1 gene rs9529895 locus SNP is significantly related to the risk for EC and PFS of EC patients. The possible mechanism behind this relationship is that the DACH1 gene rs9529895 locus SNP affects DACH1 expression level.

MicroRNA-200c promotes tumor cell proliferation and migration by directly targeting dachshund family transcription factor 1 by the Wnt/β-catenin signaling pathway in nasopharyngeal carcinoma.

The purpose of the present study was to determine the crucial role of microRNAs (miRNAs/miRs) involved in the proliferation and migration of nasopharyngeal carcinoma (NPC) and to investigate their underlying mechanisms. In this study, we focused on the expression and function of miR-200c in NPC. First, we found the expression level of miR-200c in NPC cells and tissues was upregulated, and it was suggested that the high expression of miR-200c accelerated the proliferation and migration of NPC cells in vitro. Notably, a result of the present study was that the cell fate determination factor dachshund family transcription factor 1 (DACH1) was identified as a direct target of miR-200c. Suppression of miR-200c expression in NPC cells increased endogenous DACH1 mRNA and protein levels, which was negatively correlated with miR-200c. Meanwhile, DACH1 was shown to regulate the Wnt/β-catenin signaling pathway. Accordingly, it was concluded that miR-200c exerted a tumor-promoting role in NPC development by targeting DACH1, which may contribute to the increase in the rates of NPC proliferation and migration. miR-200c may be a potential diagnostic and prognostic biomarker for NPC.

Abstract 5906: EGFR and SOX2 crosstalk determines EGFR-TKI

Abstract Activating mutations in the epidermal growth factor receptor (EGFR), while initiating lung tumorigenesis, render tumors susceptible to EGFR-tyrosine kinase inhibitors (TKIs). SOX2 functions as a cell fate determination factor in lung progenitor cells. However, how SOX2 expression affects TKI treatment and tumor invasion in lung cancer is obscure. Here we report that EGFR mutations crosstalk with SOX2 to maintain cell proliferation and barrier properties in lung cancer cells, some of which generate heterogeneity by switching off SOX2 expression, thus promoting TKI resistance and invasiveness. Downregulation of SOX2 expression by shRNA against SOX2 or TGF-beta treatment induced epithelial-to-mesenchymal transition (EMT) and endowed cell resistant to TKIs. TKI treatment selected EGFR-mutated lung cancer cells harboring low SOX2 expression with the EMT signature. TKI naïve EGFR-mutated lung cancer cells harboring low SOX2 expression exhibits intrinsic TKI resistance. Conversely, enhancing endogenous SOX2 expression reverses EMT and increases sensitivity to TKIs. Immunohistochemistry analysis revealed that low SOX2 expression predicts a poor survival in patients harboring EGFR mutations. Taken together, our findings show how cancer plasticity elicited by SOX2 expression and TKI selection generates distinct oncogenic properties and TKI sensitivity, providing critical insights into tumor progression in EGFR-mutated lung cancer. Citation Format: An-Chun Lee, Chia-Cherng Yu, Yuan-Hung Wang, Yu-Ting Chou. EGFR and SOX2 crosstalk determines EGFR-TKI [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 5906.

MicroRNA-552 promotes tumor cell proliferation and migration by directly targeting DACH1 via the Wnt/β-catenin signaling pathway in colorectal cancer.

The purpose of the present study was to analyze the crucial role of microRNAs (miRNAs/miRs) involved in the proliferation and migration of colorectal cancer (CRC) and to investigate their underlying mechanisms. The present study discusses the expression and function of miR-552 in CRC. The expression level of miR-552 in CRC cells and tissues was observed, and it was suggested that the high expression of miR-552 accelerated the proliferation and migration of CRC cells in vitro. Notably, a result of the present study was that the cell fate determination factor Dachshund family transcription factor 1 (DACH1) was identified as a direct target of miR-552. Suppressing miR-552 expression in CRC cells increased endogenous DACH1 mRNA and protein levels, which was negatively correlated with miR-552. DACH1 performs an important role in the development of a number of neoplasms, and has the ability to regulate the Wnt/β-catenin signaling pathway as a novel predictive and diagnostic biomarker. Accordingly, it was concluded that miR-552 exerted a tumor-promoting role in CRC development by targeting DACH1, which may contribute to the increase in the rates of CRC proliferation and migration. miR-552 may serve as a potential diagnostic and prognostic biomarker for CRC.

DACH1 suppresses breast cancer as a negative regulator of CD44

Dachshund homolog 1 (DACH1), a key cell fate determination factor, contributes to tumorigenesis, invasion, metastasis of human breast neoplasm. However, the exact molecular mechanisms for the anti-tumor roles of DACH1 in breast carcinoma are still lack of extensive understanding. Herein, we utilized immunohistochemistry (IHC) staining and public microarray data analysis showing that DACH1 was higher in normal breast, low-grade and luminal-type cancer in comparison with breast carcinoma, high-grade and basal-like tumors respectively. Additionally, both correlation analysis of public databases of human breast carcinoma and IHC analysis of mice xenograft tumors demonstrated that DACH1 inversely related to cancer stem cells (CSCs) markers, epithelial-mesenchymal transition (EMT) inducers and basal-enriched molecules, while cluster of differentiation 44 (CD44) behaved in an opposite manner. Furthermore, mice transplanted tumor model indicated that breast cancer cells Met-1 with up-regulation of DACH1 were endowed with remarkably reduced potential of tumorigenesis. Importantly, meta-analysis of 19 Gene Expression Omnibus (GEO) databases of breast cancer implicated that patients with higher DACH1 expression had prolonged time to death, recurrence and metastasis, while CD44 was a promising biomarker predicting worse overall survival (OS) and metastasis-free survival (MFS). Collectively, our study indicated that CD44 might be a novel target of DACH1 in breast carcinoma.

Decreased DACH1 expression in glomerulopathy is associated with disease progression and severity.

Cell fate determination factor dachshund1 (DACH1) is a chromosome-associated protein that regulates cellular differentiation throughout development. Recent genome-wide association studies have show that missense mutation in DACH1 leads to hereditary renal hypodysplasia. Renal DACH1 expression can be used to estimate glomerular filtration rate (eGFR). We firstly characterized the function of DACH1 in normal and diseased renal tissue using immunohistochemistry to assess DACH1 in human renal biopsy specimens from 40 immunoglobulin A nephropathy (IgAN) patients, 20 idiopathic membranous nephropathy (IMN) patients, and 15 minimal change disease (MCD) patients. We found that DACH1 expression was decreased in the nephropathy group relative to healthy controls. DACH1 staining in the glomerulus correlated positively with eGFR (r = 0.41, p < 0.001) but negatively with serum creatinine (r = −0.37, p < 0.01). In vitro, DACH1 overexpression in human podocytes or HK2 cells decreased expression of cyclin D1, but increased expression of p21 and p53, which suggested that DACH1 overexpression in human podocytes or HK2 cells increased the G1/S phase or G2/M cell arrest. Together, These findings indicate that DACH1 expression is decreased in glomerulopathy imply a potential role for DACH1 in the this development of human chornic glomerulopathy. These data suggest that DACH1 is a potential a marker of disease progression and severity for glomerular diseases.

Notch Signaling: A Potential Therapeutic Target for Hematologic Malignancies.

Notch signaling is a well-conserved cell-fate determining factor in embryo development, and the dyregulation of this signaling is frequently observed in many types of cancers, including hematological malignancies. In this review, we briefly describe the Notch signaling pathway, and we primarily focus on the relationship between Notch and hematological malignancies. We also discuss the clinical development of promising agents including γ-secretase inhibitors (GSIs) and monoclonal antibodies (mAbs). Complete response has been observed among patients with T-cell acute lymphoblastic leukemia (T-ALL) when treated with GSIs. Furthermore, a recent study has suggested that targeting Zmiz1, a direct, selective cofactor of Notch1, rather than targeting Notch directly, maybe helpful to reduce the current target-related toxicities. Taken together, we summarize the role of Notch signaling in hematological malignancies and discuss the treatment strategies for these diseases through targeting Notch signaling.

ASPM regulates symmetric stem cell division by tuning Cyclin E ubiquitination.

We generate a mouse model for the human microcephaly syndrome by mutating the ASPM locus, and demonstrate a premature exhaustion of the neuronal progenitor pool due to dysfunctional self-renewal processes. Earlier studies have linked ASPM mutant progenitor excessive cell cycle exit to a mitotic orientation defect. Here, we demonstrate a mitotic orientation-independent effect of ASPM on cell cycle duration. We pinpoint the cell fate-determining factor to the length of time spent in early G1 before traversing the restriction point. Characterization of the molecular mechanism reveals an interaction between ASPM and the Cdk2/Cyclin E complex, regulating the Cyclin activity by modulating its ubiquitination, phosphorylation and localization into the nucleus, before the cell is fated to transverse the restriction point. Thus, we reveal a novel function of ASPM in mediating the tightly coordinated Ubiquitin- Cyclin E- Retinoblastoma- E2F bistable-signalling pathway controlling restriction point progression and stem cell maintenance.

Abstract 1074: Epigenetic silencing of DACH1 in triple negative breast cancer contributes to the tumorigenesis

Abstract BACKGROUND: Increasing evidence indicates that cell fate determination factor DACH1 functions as a tumor suppressor. Specifically, in estrogen receptor positive (luminal), highly expression of DACH1 predicted longer cancer specific survival and disease free interval, as well as reduced metastasis formation. Our analysis of over 2,000 patients demonstrated increased nuclear DACH1 expression correlated inversely with cellular mitosis and predicted 40 months survival advantage in breast cancer patients. But, endogenous DACH1 was dramatically reduced in breast cancer cell lines with high expression of tumor initiation cell markers and in patient samples of triple negative breast cancer, the most aggressive subtype. We proposed that epigenetically change might contribute to the loss expression of DACH1 in breast cancer. MATERIALS AND METHODS: Clinical samples included 10cases of normal breast tissues, 26 cases of luminal breast cancer(ER+,PR+,HER1-2+), and 32 cases of triple negative breast cancer(ER-,PR-,HER-). Genomic DNA was extracted from formalin-fixed tissue and methylation-specific PCR of DACH1 promoter was performed. DACH1 protein expression was detected in human breast cancer tissue arrays by immunohistochemistry. Human triple negative breast cancer cell lines MDA-MB-231 and sum159 were cultured in DME medium supplied with 10% fetal bovine serum and growth factors. Stable cell lines expressing DACH1 were established in MDA-MB-231 and Sum159 though lentivirus transfection. In vitro cell growth was evaluated by MTT assay and colony formation. In vivo tumor growth was measured in xenograft mice model. RESULTS: There is no methylation of DACH1 promoter region was found in normal breast tissues, but methylation was found in 2 out of 26 (7.7%) in luminal breast cancer and 10 of 32(32%) in triple negative breast cancer. Consisting with previous report, immunohistochemical stain revealed nuclear stain of DACH1 in all normal and majority of luminal type breast cancer tissues, but lost or very weak expression of DACH1 in triple negative cancer tissues. Correspondingly, expression microarrays demonstrated that DACH1 mRNA levels in triple negative breast cancer cell lines were dramatically less than that of normal breast cell line and luminal breast cancer cell lines. Treatment of MDA-MB-231 and Sum159 cells with 5-Aza-2′-deoxyazacytidine induced the expression of DACH1 and decreased cellular proliferation. Ectopic expression of DACH1 inhibited in vitro cell growth and in vivo tumor formation. CONCLUSION: Promoter hypermethylation is a main factor leading to the inactivation of DACH1 in triple negative breast cancer; Re-expression of DACH1by epigenetic modification might provide a novel therapeutic strategy for this aggressive cancer. Citation Format: Qian Chu, Na Han, Yan Dong, Xun Yuan, Mingzhou Guo, Hanxiao Xu, Shiying Yu, Kongming Wu. Epigenetic silencing of DACH1 in triple negative breast cancer contributes to the tumorigenesis. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 1074. doi:10.1158/1538-7445.AM2015-1074

Abstract 515: Cell fate determination factor DACH1 inhibits lung adenocarcinoma invasion and tumor growth through repression of CXCL5 signaling

Abstract The onset of human lung cancer involves the loss of tumor suppressor genes and activation of tumor inducing genes. Current studies have proved EGFR, RAS, ALK as as key driver genes, however, in about 50% lung cancer samples there are no known genes to explain tumorigenesis, suggesting many novel pathways remain to be elucidated. Recent study on whole-genome and transcriptome sequencing NSCLC identified cell fate determinatiton gene DACH1 as novel alteration in genes involved in NSCLC. However, the role of DACH1 in NSCLC and its downstrem targets are largely unknown. We showed that expression of DACH1 was significantly decreased in human NSCLC tissues andits protein abundance was inversely correlated with the tumor stage and grade. Restoration of DACH1 function in NSCLC cells significantly reduced cellular proliferation, clone formation, migrasion and invasion in vitro, as well as tumor growth in vivo. By unbiased screen of secreting factors, we found out that CXCL5 was dramaticcaly repressed by DACH1. Furthermore, functional study suggested that CXCL5 was contribute to the DACH1-mediated repression of migrative in vitro and tumorigenesis in vivo. Consistingly, there was a inverse relationship between the mRNA level of DACH1 and CXCL5 in both lung cancer cell lines and huamn NSCLC tissues. Moreover, Kaplan-Meier analysis of human NSCLC samples demonstrated that high mRNA abundance of DACH1 was predicted favorate prognosis for both relaspse-free survivl and overall survival; in contrast, high CXCL5 expression predict worse prognosis for survival. To our understanding, this is the first study to demonstrate DACH1 regulated paracrine signaling in lung cancer and DACH1 could predict prognosis. In conclusion, DACH1 acts as a tumor suppressor gene through repression of paracrine signaling and is a potential biomarker for prognosis. Citation Format: Na Han, Xun Yuan, Hua Wu, Hanxiao Xu, Qian Chu, Mingzhou Guo, Shiying Yu, Yuan Chen, Kongming Wu. Cell fate determination factor DACH1 inhibits lung adenocarcinoma invasion and tumor growth through repression of CXCL5 signaling. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 515. doi:10.1158/1538-7445.AM2015-515

DACH1 is a novel predictive and prognostic biomarker in hepatocellular carcinoma as a negative regulator of Wnt/β-catenin signaling.

The cell fate determination factor Dachshund (DACH1) functions as a novel suppressor in the progression of various neoplasms. Previous study has suggested that hypermethylation of promoter region was responsible for the reduction of DACH1 expression in hepatocellular carcinoma (HCC), and associated with the progression of HCC, but the clinical significance and the exact molecular mechanisms of DACH1 in the progression of HCC remain unclear. In this study, we employed public microarray data analysis and tissue microarrays (TMAs) technologies and showed that DACH1 expression was reduced in HCC even at early stage and associated with the tumor progression. Notably, Kaplan-Meier analysis further indicated DACH1 could be an independent prognostic factor for the overall survival of HCC. Further, mechanistic studies revealed that overexpression of DACH1 inhibited the growth and migration of HCC cell line, which were dependent in part on the inactivation of Wnt pathway via phosphorylation of GSK3β to suppress β-catenin. In agreement, the abundance of DACH1 was inversely correlated with several Wnt target genes. Collectively, our study indicated β-catenin is a novel target of DACH1 in HCC.

Mutations in MAB21L2 result in ocular Coloboma, microcornea and cataracts.

Ocular coloboma results from abnormal embryonic development and is often associated with additional ocular and systemic features. Coloboma is a highly heterogeneous disorder with many cases remaining unexplained. Whole exome sequencing from two cousins affected with dominant coloboma with microcornea, cataracts, and skeletal dysplasia identified a novel heterozygous allele in MAB21L2, c.151 C>G, p.(Arg51Gly); the mutation was present in all five family members with the disease and appeared de novo in the first affected generation of the three-generational pedigree. MAB21L2 encodes a protein similar to C. elegans mab-21 cell fate-determining factor; the molecular function of MAB21L2 is largely unknown. To further evaluate the role of MAB21L2, zebrafish mutants carrying a p.(Gln48Serfs*5) frameshift truncation (mab21l2Q48Sfs*5) and a p.(Arg51_Phe52del) in-frame deletion (mab21l2R51_F52del) were developed with TALEN technology. Homozygous zebrafish embryos from both lines developed variable lens and coloboma phenotypes: mab21l2Q48Sfs*5 embryos demonstrated severe lens and retinal defects with complete lethality while mab21l2R51_F52del mutants displayed a milder lens phenotype and severe coloboma with a small number of fish surviving to adulthood. Protein studies showed decreased stability for the human p.(Arg51Gly) and zebrafish p.(Arg51_Phe52del) mutant proteins and predicted a complete loss-of-function for the zebrafish p.(Gln48Serfs*5) frameshift truncation. Additionally, in contrast to wild-type human MAB21L2 transcript, mutant p.(Arg51Gly) mRNA failed to efficiently rescue the ocular phenotype when injected into mab21l2Q48Sfs*5 embryos, suggesting this allele is functionally deficient. Histology, immunohistochemistry, and in situ hybridization experiments identified retinal invagination defects, an increase in cell death, abnormal proliferation patterns, and altered expression of several ocular markers in the mab21l2 mutants. These findings support the identification of MAB21L2 as a novel factor involved in human coloboma and highlight the power of genome editing manipulation in model organisms for analysis of the effects of whole exome variation in humans.

MiR-217 Promotes Tumor Proliferation in Breast Cancer via Targeting DACH1.

Objective: The expression of DACH1 was frequently lost in human breast cancer, which significantly correlated with poor prognosis. Herein, we aim to investigate its underlying mechanisms.Methods: The expression of miR-217 was detected by Taqman PCR. The mRNA and protein level of DACH1 were investigated by real time PCR and western blot. The dual-luciferase reporter system was used to determine the direct interaction between miR-217 and DACH1. A series of gain&loss of function assays were performed to measure the affects of miR-217 on tumor proliferation and cell cycle distribution.Results: Compared to that in normal breast samples, the expression of miR-217 was significantly upregulated in breast cancer tissues. High level of miR-217 was notably correlated with highly histological grade, the triple negative subtype and advanced tumor stage. Moreover, the expression of miR-217 was negatively correlated with the expression of DACH1. The results of dual-luciferase reporter assay demonstrated that miR-217 directly targets and inhibits the transcriptive activity of DACH1. In vitro, treatment with miR-217 mimics significantly suppressed the proliferation of MCF-7 cells, induced G1 phase arrest and inhibited the expression of cyclin D1; while these effects were significantly reversed by the restoration of DACH1. In MDA-MB-231 cells, treatment with miR-217 inhibitors enhanced the cellular proliferation, promoted cell cycle progression and upregulated the expression of cyclin D1, which were neutralized by the pre-treatment of siRNA-DACH1. In vivo, inhibition of miR-217 significantly suppressed the xenografts growth and downregulated the expression of cyclin D1.Conclusion: We found that miR-217 was commonly overexpressed in breast cancer, which could enhance tumor proliferation via promoting cell cycle progression. Moreover, the DACH1 (the cell fate determination factor) was identified as a novel target of miR-217. Our results proposed inhibiting miR-217 to be a potent therapeutic strategy for breast cancer.

Cell Fate Factor DACH1 Represses YB-1–Mediated Oncogenic Transcription and Translation

The epithelial-mesenchymal transition (EMT) enhances cellular invasiveness and confers tumor cells with cancer stem cell-like characteristics, through transcriptional and translational mechanisms. The mechanisms maintaining transcriptional and translational repression of EMT and cellular invasion are poorly understood. Herein, the cell fate determination factor Dachshund (DACH1), suppressed EMT via repression of cytoplasmic translational induction of Snail by inactivating the Y box-binding protein (YB-1). In the nucleus, DACH1 antagonized YB-1-mediated oncogenic transcriptional modules governing cell invasion. DACH1 blocked YB-1-induced mammary tumor growth and EMT in mice. In basal-like breast cancer, the reduced expression of DACH1 and increased YB-1 correlated with poor metastasis-free survival. The loss of DACH1 suppression of both cytoplasmic translational and nuclear transcriptional events governing EMT and tumor invasion may contribute to poor prognosis in basal-like forms of breast cancer, a relatively aggressive disease subtype.

Abstract P5-11-04: Post-translational modification of the cell-fate factor Dachshund determines p53 binding and signaling modules in breast cancer

Abstract Breast cancer is a leading form of cancer in the world. Initially cloned as a dominant inhibitor of the hyperactive EGFR, Ellipse, in Drosophila, the mammalian DACH1 regulates expression of target genes in part through interacting with DNA-binding transcription factors (c-Jun, Smads, Six, ERα), and in part through intrinsic DNA-sequence specific binding to Forkhead binding sites. The Drosophila dac gene is a key member of the retinal determination gene network (RDGN), which also includes eyes absent (eya), ey, twin of eyeless (toy), teashirt (tsh) and sin oculis (so), that specifies eye tissue identity. Several lines of evidence suggest DACH1 may function as a tumor suppressor. Clinical studies have demonstrated a correlation between poor prognosis and reduced expression of the cell-fate determination factor DACH1 in breast cancer, and loss of DACH1 expression has been observed in prostate and endometrial cancer. DACH1 inhibits breast cancer tumor metastasis and reduces breast cancer stem cell expansion via Sox2/Nanog. Although these studies suggest DACH1 may function as a tumor suppressor, the molecular mechanisms remain poorly defined. Herein, endogenous DACH1 co-localized with p53 in a nuclear, extranucleolar compartment and bound to p53 in human breast cancer cell lines, p53 and DACH1 bound common genes in ChIP-Seq. Full inhibition of breast cancer contact-independent growth by DACH1 required p53. The p53 breast cancer mutants R248Q and R273H, evaded DACH1 binding. DACH1 phosphorylation at serine residue (S439) inhibited p53 binding and phosphorylation at p53 amino-terminal sites (S15, S20) enhanced DACH1 binding. DACH1 binding to p53 was inhibited by NAD-dependent deacetylation via DACH1 K628. DACH1 repressed p21CIP1 and induced RAD51, an association found in basal breast cancer. DACH1 inhibits breast cancer cellular growth in an NAD and p53 dependent manner through direct protein-protein association. Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P5-11-04.

Abstract P1-07-05: The cell fate factor DACH1 represses YB-1-mediated oncogenic transcription and translation

Abstract The epithelial-mesenchymal transition (EMT) enhances cellular invasiveness and confers tumor cells with cancer stem cell like characteristics, through transcriptional and translational mechanisms. The mechanisms maintaining transcriptional and translational repression of EMT and cellular invasion are poorly understood. The Drosophila homologue of DACH1, the Dac gene is a key member of the retinal determination gene network that specifies organismal development. The dachshund (dac), eya1, eyes-absent (eya), twin of eyeless (toy), teashirt (tsh) and sinoculues (so) are expressed in progenitor cells, contributing to development of the eye and genitalia. Loss of DACH1 expression contributes to the expansion of neural progenitors, muscle satellite cell differentiation and breast cancer stem cells. In recent studies Dachshund repressed breast cancer stem cell expansion. DACH1 expression is reduced in a variety of human cancers including prostate, ovarian and human breast cancer. Herein, the cell fate-determination factor Dachshund (DACH1), suppressed EMT via repression of cytoplasmic translational induction of Snail by inactivating the Y box-binding protein (YB-1). In the nucleus, DACH1 antagonized YB-1-mediated oncogenic transcriptional modules governing cell invasion. DACH1 blocked YB-1-induced mammary tumor growth and EMT in mice. In basal-like breast cancer (BLBC) the reduced expression of DACH1 and increased YB-1, correlated with poor metastasis free survival. The loss of DACH1 suppression of both cytoplasmic translational and nuclear transcriptional events governing EMT and tumor invasion may contribute to poor prognosis in BLBC. Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P1-07-05.

Abstract 1319: Regulation of AR transcriptional activity and prostate cancer cellular proliferation by DACH1/Eya1/Six1 pathway.

Abstract Prostate cancer progression from androgen responsive to androgen-depletion therapy resistance is a major cause of treatment failures. Novel therapies targeting this patient are a major clinical challenge. We previously reported that the cell fate determination factor DACH1 inhibits androgen signaling though binding the AR and enhancing co-repressor recruitment in the context of local chromatin at AR responsive genes. The repression of AR function of by DACH1 was partly rescued by the co-activators p300 and SRC. The repression was enhanced by ectopic expression of HDACs. We had previously shown that DACH1 inhibited proliferation of androgen-dependent LnCAP cells. To further explore the significance of DACH1 in human prostate cancer, we established stable cell lines expressing DACH1 or its DS domain deleted mutant (ΔDS) in androgen-independent C4-2 cells and AR-negative PC-3 cells by retrovirus infection. Stable expression of DACH1 inhibited cellular proliferation in both cell lines, requiring the DS domain. Ectopic expression of DACH1 inhibited colony formation of the androgen-independent 22RV1 cells. DACH1 inhibited migration, invasion and tumor growth of AR-negative PC-3 cells. Since DACH1, Eya1 and Six1 function together as a network to control cellular differentiation and organ formation during development, we examined whether other components of RDGN pathway, could regulate androgen signaling. In hormone responsive LnCAP cells, ligand stimulation (DHT, 50nM) induced 17 folds activation of MMTV Luc, co-expression of Eya1 reduced AR transactivation, and the repression required the EYA phophatase domain. Expressions of the AR co-repressors, HDAC1, HDAC3 or SirT1 inhibited the ligand-induced AR activity. Eya1 enhanced co-repressor function at the PSA and MMTV promoters. Consistent with our previous publication, DACH1 repressed ligand-induced activity &amp;gt;70%, Eya1 modified DACH1 repression of AR activity. Together, our studies demonstrated that the RDGN regulates both androgen dependent and independent prostate cancer cellular proliferation and tumorigenesis. Citation Format: Jing Wang, Shaoxin Cai, Ke Chen, Sean Li, Richard Pestell, Kongming Wu. Regulation of AR transcriptional activity and prostate cancer cellular proliferation by DACH1/Eya1/Six1 pathway. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 1319. doi:10.1158/1538-7445.AM2013-1319