Dachshund inhibits oncogene-induced breast cancer cellular migration and invasion through suppression of interleukin-8

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.

Epigenetic silencing of DACH1 induces loss of transforming growth factor-β1 antiproliferative response in human hepatocellular carcinoma

Human dachshund homolog 1 (DACH1) is a major component of the Retinal Determination Gene Network (RDGN) and functions as a tumor suppressor. However, the regulation of DACH1 expression and its function in hepatocellular carcinoma (HCC) remain unclear. In this study, epigenetic changes of DACH1 were analyzed in HCC cell lines and primary cancers. We found that promoter region hypermethylation was correlated with loss or reduction of DACH1 expression, and restoration of DACH1 expression was induced by 5-aza-2'-deoxycytidine (5-AZA) in HCC cell lines. Promoter region methylation was found in 42% of primary HCC. Reduced expression of DACH1 was associated with poor differentiation of HCC nodules and higher serum aspartate aminotransferase/alanine aminotransferase ratio. DACH1 suppressed cellular growth by reactivating transforming growth factor beta (TGF-β) signaling. Ectopic expression of DACH1 enhanced chemosensitivity to 5-fluorouracil (5-FU) by inducing p21 expression in HCC cells.

CONCLUSION

DACH1 is frequently methylated in HCC and DACH1 expression is regulated by promoter hypermethylation. Down-regulation of DACH1 is a novel mechanism for gaining resistance to the antiproliferative signaling of TGF-β1 and 5-FU resistance.

Luteolin 8-C-β-fucopyranoside inhibits invasion and suppresses TPA-induced MMP-9 and IL-8 via ERK/AP-1 and ERK/NF-κB signaling in MCF-7 breast cancer cells

Matrix metalloproteinase 9 (MMP-9) and interleukin-8 (IL-8) play major roles in tumor progression and invasion of breast cancer cells. The present study was undertaken to investigate the inhibitory mechanism of cell invasion by luteolin 8-C-β-fucopyranoside (named as LU8C-FP), a C-glycosylflavone, in human breast cancer cells. We investigated whether LU8C-FP would inhibit MMP-9 activation and IL-8 expression in 12-O-tetradecanoylphorbol-13-acetate (TPA)-treated MCF-7 breast cancer cells. LU8C-FP suppressed TPA-induced MMP-9 and IL-8 secretion and mRNA expression via inhibition of the MAPK signaling pathway and down-regulation of nuclear AP-1 and NF-κB. TPA-induced phosphorylation of ERK 1/2 was suppressed by LU8C-FP, whereas JNK and p38 MAPK phosphorylation were unaffected. In addition, LU8C-FP blocked the ERK 1/2 pathways following expression of MMP-9 and IL-8. These results suggest LU8C-FP may function to suppress invasion of breast cancer cells through the ERK/AP-1 and ERK/NF-κB signaling cascades.

EYA1 phosphatase function is essential to drive breast cancer cell proliferation through cyclin D1

The Drosophila Eyes Absent Homologue 1 (EYA1) is a component of the retinal determination gene network and serves as an H2AX phosphatase. The cyclin D1 gene encodes the regulatory subunits of a holoenzyme that phosphorylates and inactivates the pRb protein. Herein, comparison with normal breast showed that EYA1 is overexpressed with cyclin D1 in luminal B breast cancer subtype. EYA1 enhanced breast tumor growth in mice in vivo, requiring the phosphatase domain. EYA1 enhanced cellular proliferation, inhibited apoptosis, and induced contact-independent growth and cyclin D1 abundance. The induction of cellular proliferation and cyclin D1 abundance, but not apoptosis, was dependent upon the EYA1 phosphatase domain. The EYA1-mediated transcriptional induction of cyclin D1 occurred via the AP-1-binding site at -953 and required the EYA1 phosphatase function. The AP-1 mutation did not affect SIX1-dependent activation of cyclin D1. EYA1 was recruited in the context of local chromatin to the cyclin D1 AP-1 site. The EYA1 phosphatase function determined the recruitment of CBP, RNA polymerase II, and acetylation of H3K9 at the cyclin D1 gene AP-1 site regulatory region in the context of local chromatin. The EYA1 phosphatase regulates cell-cycle control via transcriptional complex formation at the cyclin D1 promoter.

Cancer stem cells

Cancer stem cells (CSCs) are a small subpopulation of cells within tumors with capabilities of self-renewal, differentiation, and tumorigenicity when transplanted into an animal host. A number of cell surface markers such as CD44, CD24, and CD133 are often used to identify and enrich CSCs. A regulatory network consisting of microRNAs and Wnt/β-catenin, Notch, and Hedgehog signaling pathways controls CSC properties. The clinical relevance of CSCs has been strengthened by emerging evidence, demonstrating that CSCs are resistant to conventional chemotherapy and radiation treatment and that CSCs are very likely to be the origin of cancer metastasis. CSCs are believed to be an important target for novel anti-cancer drug discovery. Herein we summarize the current understanding of CSCs, with a focus on the role of miRNA and epithelial-mesenchymal transition (EMT), and discuss the clinical application of targeting CSCs for cancer treatment.

BLT2 up-regulates interleukin-8 production and promotes the invasiveness of breast cancer cells

BACKGROUND

The elevated production of interleukin (IL)-8 is critically associated with invasiveness and metastatic potential in breast cancer cells. However, the intracellular signaling pathway responsible for up-regulation of IL-8 production in breast cancer cells has remained unclear.

METHODOLOGY/PRINCIPAL FINDINGS

In this study, we report that the expression of BLT2 is markedly up-regulated in the highly aggressive human breast cancer cell lines MDA-MB-231 and MDA-MB-435 compared with MCF-10A immortalized human mammary epithelial cells, as determined by RT-PCR, real-time PCR and FACS analysis. Blockade of BLT2 with BLT2 siRNA knockdown or BLT2 inhibitor treatment downregulated IL-8 production and thereby diminished the invasiveness of aggressive breast cancer cells, analyzed by Matrigel invasion chamber assays. We further characterized the downstream signaling mechanism by which BLT2 stimulates IL-8 production and identified critical mediatory roles for the generation of reactive oxygen species (ROS) and the consequent activation of the transcription factor NF-κB. Moreover, blockade of BLT2 suppressed the formation of metastatic lung nodules by MDA-MB-231 cells in both experimental and orthotopic metastasis models.

CONCLUSIONS/SIGNIFICANCE

Taken together, our study demonstrates that a BLT2-ROS-NF-κB pathway up-regulates IL-8 production in MDA-MB-231 and MDA-MB-435 cells, thereby contributing to the invasiveness of these aggressive breast cancer cells. Our findings provide insight into the molecular mechanism of invasiveness in breast cancer.

DACH1 Expresison in Osteosarcoma and Its Relationship with Proliferation and Angiogenesis

The aim of this study was to investigate the expression of DACH1 in osteosarcoma as well as its relationship with cell proliferation and angiogenesis in the tumor. DACH1 expression was detected by immunohistochemical staining in the serial sections of the osteosarcoma. The microvessel density (MVD) was counted by CD34 immunohistochemical staining, and immunohistochemical staining of PCNA staining showed the cell proliferation. The impacts of DACH1 expression on tumor proliferation and angiogenesis were evaluated by statistics. The DACH1 had different expression patterns in different osteosarcoma. Conventional osteosarcoma showed stronger DACH1 staining (conventional vs. parosteal: P = 0.037; conventional vs. periosteal: P = 0.028) and more PCNA-positive tumor cells than parosteal and periosteal osteosarcoma (conventional vs. parosteal: P = 0.041; conventional vs. periosteal: P = 0.045), the difference was significant. In addition, conventional osteosarcoma showed more cytoplasmic staining of DACH1 than parosteal and periosteal (conventional vs. parosteal: P = 0.023; conventional vs. periosteal: P = 0.030). Parosteal and periosteal osteosarcoma showed no significant difference in DACH1 expression and cell proliferation index. On the other hand, DACH1 different expression patterns showed significantly different impacts on angiogenesis. In spite of the different subtypes of osteosarcoma, the MVD showed a significant difference in cytoplasmic and nuclear expression patterns of DACH1 (nuclear expression vs. cytoplasmic expression: 5.72 ± 1.19 vs. 9.65 ± 1.24, P = 0.042). Moreover, in the conventional osteosarcoma, the MVD also showed a significant difference in DACH1 cytoplasmic and nuclear staining (nuclear expression vs. cytoplasmic expression: 5.58 ± 0.71 vs. 13.65 ± 1.30, P = 0.019). However, the DACH1 expression intensity showed no significant different impacts on MVD of all kinds of osteosarcoma. DACH1 had different expression patterns and intensity. Cytoplasmic and nuclear expression of DACH1 might play different roles in cell proliferation and angiogenesis of osteosarcoma. Cytoplasmic DACH1 might promote cell proliferation and be associated with angiogenesis.

The Eyes Absent proteins in development and disease

The Eyes Absent (EYA) proteins, first described in the context of fly eye development, are now implicated in processes as disparate as organ development, innate immunity, DNA damage repair, photoperiodism, angiogenesis, and cancer metastasis. These functions are associated with an unusual combination of biochemical activities: tyrosine phosphatase and threonine phosphatase activities in separate domains, and transactivation potential when associated with a DNA-binding partner. EYA mutations are linked to multiorgan developmental disorders, as well as to adult diseases ranging from dilated cardiomyopathy to late-onset sensorineural hearing loss. With the growing understanding of EYA biochemical and cellular activity, biological function, and association with disease, comes the possibility that the EYA proteins are amenable to the design of targeted therapeutics. The availability of structural information, direct links to disease states, available animal models, and the fact that they utilize unconventional reaction mechanisms that could allow specificity, suggest that EYAs are well-positioned for drug discovery efforts. This review provides a summary of EYA structure, activity, and function, as they relate to development and disease, with particular emphasis on recent findings.

Gankyrin promotes breast cancer cell metastasis by regulating Rac1 activity

Tumor metastasis is responsible for most cancer patients' deaths. Understanding the mechanism of metastasis is crucial for improving the cure rate for cancer. Here, we report that Gankyrin, a chaperone of ubiquitin-proteasome, has an essential role in breast cancer metastasis. We find that Gankyrin is highly overexpressed in human breast cancers and the expression correlates strongly with lymph node metastasis. Knocking down Gankyrin expression in highly metastatic human breast cancer cells significantly decreases cancer cell migration and invasion. Furthermore, we demonstrate that depletion of Gankyrin inhibits intrinsic Rac1 activity and induces large focal adhesions. Overexpression of Gankyrin accelerates focal adhesion turnover and increases cell migration. Notably, reduction of Gankyrin expression in mouse mammary tumor cell significantly decreases tumor metastasis to lung in animal models. Therefore, our findings suggest that Gankyrin is crucial for breast cancer metastasis and highlight the potential of Gankyrin as a therapeutic target for tumor metastasis.

Increased expression of dachshund homolog 1 in ovarian cancer as a predictor for poor outcome

OBJECTIVE

This study aimed to determine the functional relationship between the levels of dachshund homolog 1 (DACH1) expression and different subtypes of ovarian cancer and to investigate the possible prognostic value of DACH1 in ovarian cancer.

METHODS

Immunohistochemical staining was deployed to determine the protein levels of DACH1. Staining was performed on patient samples, for whom the detailed follow-up data have been acquired during the last 10 years. Normal, benign, borderline, cancer, and metastatic ovarian cancer samples were included in this study.

RESULTS

The results of our study show that DACH1 protein levels increase with the invasiveness of the ovarian cancer. As the cancer progresses from benign and borderline to metastatic, DACH1 protein expression increases as well. Moreover, with the increase in expression, the subcellular distribution of DACH1 changes from nucleus in normal tissue to cytoplasm in cancer. Finally, DACH1 expression levels were compared with estrogen receptor α (ERα) levels, and the results showed that overall DACH1 levels were higher, whereas also DACH1 exhibited increased cytoplasmic expression in ERα-positive ovarian cancer samples.

CONCLUSIONS

These results indicate that DACH1 is highly expressed in metastatic ovarian cancer compared with that of normal, benign, and borderline ovarian tissues and that it could play an important role in cancer growth.

CCR5 antagonist blocks metastasis of basal breast cancer cells

The roles of the chemokine CCL5 and its receptor CCR5 in breast cancer progression remain unclear. Here, we conducted microarray analysis on 2,254 human breast cancer specimens and found increased expression of CCL5 and its receptor CCR5, but not CCR3, in the basal and HER-2 genetic subtypes. The subpopulation of human breast cancer cell lines found to express CCR5 displayed a functional response to CCL5. In addition, oncogene transformation induced CCR5 expression, and the subpopulation of cells that expressed functional CCR5 also displayed increased invasiveness. The CCR5 antagonists maraviroc or vicriviroc, developed to block CCR5 HIV coreceptor function, reduced in vitro invasion of basal breast cancer cells without affecting cell proliferation or viability, and maraviroc decreased pulmonary metastasis in a preclinical mouse model of breast cancer. Taken together, our findings provide evidence for the key role of CCL5/CCR5 in the invasiveness of basal breast cancer cells and suggest that CCR5 antagonists may be used as an adjuvant therapy to reduce the risk of metastasis in patients with the basal breast cancer subtype.

Intra-ophthalmic artery chemotherapy triggers vascular toxicity through endothelial cell inflammation and leukostasis

Purpose. Super-selective intra-ophthalmic artery chemotherapy (SSIOAC) is an eye-targeted drug-delivery strategy to treat retinoblastoma, the most prevalent primary ocular malignancy in children. Unfortunately, recent clinical reports associate adverse vascular toxicities with SSIOAC using melphalan, the most commonly used chemotherapeutic. Methods. To explore reasons for the unexpected vascular toxicities, we examined the effects of melphalan, as well as carboplatin (another chemotherapeutic used with retinoblastoma), in vitro using primary human retinal endothelial cells, and in vivo using a non-human primate model, which allowed us to monitor the retina in real time during SSIOAC. Results. Both melphalan and carboplatin triggered human retinal endothelial cell migration, proliferation, apoptosis, and increased expression of adhesion proteins intracellullar adhesion molecule-1 [ICAM-1] and soluble chemotactic factors (IL-8). Melphalan increased monocytic adhesion to human retinal endothelial cells. Consistent with these in vitro findings, histopathology showed vessel wall endothelial cell changes, leukostasis, and vessel occlusion. Conclusions. These results reflect a direct interaction of chemotherapeutic drugs with both the vascular endothelium and monocytes. The vascular toxicity may be related to the pH, the pulsatile delivery, or the chemotherapeutic drugs used. Our long-term goal is to determine if changes in the drug of choice and/or delivery procedures will decrease vascular toxicity and lead to better eye-targeted treatment strategies.

MicroRNA-520/373 family functions as a tumor suppressor in estrogen receptor negative breast cancer by targeting NF-κB and TGF-β signaling pathways

MicroRNAs (miRNAs) as modulators of gene expression have been described to display both tumor-promoting and tumor-suppressive functions. Although their role has been studied in different tumor types, little is known about how they regulate nuclear factor κB (NF-κB) signaling in breast cancer. Here, we performed an unbiased whole genome miRNA (miRome) screen to identify novel modulators of NF-κB pathway in breast cancer. The screen identified 13 miRNA families whose members induced consistent effects on NF-κB activity. Among those, the miR-520/373 family inhibited NF-κB signaling through direct targeting of RELA and thus strongly reduced expression and secretion of the pro-inflammatory cytokines interleukin (IL)-6 and IL-8. With a combination of in vitro and in vivo approaches, we propose a metastasis-suppressive role of miR-520/373 family. miR-520c and miR-373 abrogated both in vitro cell invasion and in vivo intravasation of highly invasive MDA-MB-231 cells. However, knockdown of RELA did not affect their metastatic ability. mRNA profiling of MDA-MB-231 cells on overexpression of miR-520/373 members revealed a strong downregulation of transforming growth factor-β (TGF-β) signaling. Mechanistically, the metastasis-suppressive role of miR-520/373 can be attributed to direct suppression of TGFBR2, as the silencing of TGFBR2 phenocopied the effects of miR-520/373 overexpression on suppression of Smad-dependent expression of the metastasis-promoting genes parathyroid hormone-related protein, plasminogen activator inhibitor-1 and angiopoietin-like 4 as well as tumor cell invasion, in vitro and in vivo. A negative correlation between miR-520c and TGFBR2 expression was observed in estrogen receptor negative (ER(-)) breast cancer patients but not in the ER positive (ER(+)) subtype. Remarkably, decreased expression of miR-520c correlated with lymph node metastasis specifically in ER(-) tumors. Taken together, our findings reveal that miR-520/373 family has a tumor-suppressive role in ER(-) breast cancer by acting as a link between the NF-κB and TGF-β pathways and may thus contribute to the interplay of tumor progression, metastasis and inflammation.

The role of breast cancer stem cells in metastasis and therapeutic implications

Cancer stem cells (CSCs) possess the capacity to self-renew and to generate heterogeneous lineages of cancer cells that comprise tumors. A substantial body of evidence supports a model in which CSCs play a major role in the initiation, maintenance, and clinical outcome of cancers. In contrast, analysis of the role of CSCs in metastasis has been mainly conceptual and speculative. This review summarizes recent data that support the theory of CSCs as the source of metastatic lesions in breast cancer, with a focus on the key role of the microenvironment in the stemness-metastasis link.

miR-520b regulates migration of breast cancer cells by targeting hepatitis B X-interacting protein and interleukin-8

MicroRNAs play important roles in tumor metastasis. Recently, we reported that the level of miR-520b is inversely related to the metastatic potential of breast cancer cells. In this study, we investigated the role of miR-520b in breast cancer cell migration. We found that miR-520b suppressed the migration of breast cancer cells with high metastatic potential, including MDA-MB-231 and LM-MCF-7 cells, although the inhibition of miR-520b enhanced the migration of low metastatic potential MCF-7 cells. We further discovered that miR-520b directly targets the 3'-untranslated region (3'UTR) of either hepatitis B X-interacting protein (HBXIP) or interleukin-8 (IL-8), which has been reported to contribute to cell migration. Surprisingly, tissue array assays showed that 75% (38:49) and 94% (36:38) of breast cancer tissues and metastatic lymph tissues, respectively, were positive for HBXIP expression. Moreover, overexpression of HBXIP was able to promote the migration of MCF-7 cells. Interestingly, HBXIP was able to regulate IL-8 transcription by NF-κB, suggesting that the two target genes of miR-520b are functionally connected. In addition, we found that miR-520b could indirectly regulate IL-8 transcription by targeting HBXIP. Thus, we conclude that miR-520b is involved in regulating breast cancer cell migration by targeting HBXIP and IL-8 via a network in which HBXIP promotes migration by stimulating NF-κB-mediated IL-8 expression. These studies point to HBXIP as a potential therapeutic target for breast cancer.

Cell fate determination factor Dachshund reprograms breast cancer stem cell function

The cell fate determination factor Dachshund was cloned as a dominant inhibitor of the hyperactive epidermal growth factor receptor ellipse. The expression of Dachshund is lost in human breast cancer associated with poor prognosis. Breast tumor-initiating cells (TIC) may contribute to tumor progression and therapy resistance. Here, endogenous DACH1 was reduced in breast cancer cell lines with high expression of TIC markers and in patient samples of the basal breast cancer phenotype. Re-expression of DACH1 reduced new tumor formation in serial transplantations in vivo, reduced mammosphere formation, and reduced the proportion of CD44(high)/CD24(low) breast tumor cells. Conversely, lentiviral shRNA to DACH1 increased the breast (B)TIC population. Genome-wide expression studies of mammary tumors demonstrated DACH1 repressed a molecular signature associated with stem cells (SOX2, Nanog, and KLF4) and genome-wide ChIP-seq analysis identified DACH1 binding to the promoter of the Nanog, KLF4, and Lin28 genes. KLF4/c-Myc and Oct4/Sox2 antagonized DACH1 repression of BTIC. Mechanistic studies demonstrated DACH1 directly repressed the Nanog and Sox2 promoters via a conserved domain. Endogenous DACH1 regulates BTIC in vitro and in vivo.

Transcription elongation regulator 1 is a co-integrator of the cell fate determination factor Dachshund homolog 1

DACH1 (Dachshund homolog 1) is a key component of the retinal determination gene network and regulates gene expression either indirectly as a co-integrator or through direct DNA binding. The current studies were conducted to understand, at a higher level of resolution, the mechanisms governing DACH1-mediated transcriptional repression via DNA sequence-specific binding. DACH1 repressed gene transcription driven by the DACH1-responsive element (DRE). Recent genome-wide ChIP-Seq analysis demonstrated DACH1 binding sites co-localized with Forkhead protein (FOX) binding sites. Herein, DACH1 repressed, whereas FOX proteins enhanced, both DRE and FOXA-responsive element-driven gene expression. Reduced DACH1 expression using a shRNA approach enhanced FOX protein activity. As DACH1 antagonized FOX target gene expression and attenuated FOX signaling, we sought to identify limiting co-integrator proteins governing DACH1 signaling. Proteomic analysis identified transcription elongation regulator 1 (TCERG1) as the transcriptional co-regulator of DACH1 activity. The FF2 domain of TCERG1 was required for DACH1 binding, and the deletion of FF2 abolished DACH1 trans-repression function. The carboxyl terminus of DACH1 was necessary and sufficient for TCERG1 binding. Thus, DACH1 represses gene transcription through direct DNA binding to the promoter region of target genes by recruiting the transcriptional co-regulator, TCERG1.

The Eyes Absent phosphatase-transactivator proteins promote proliferation, transformation, migration, and invasion of tumor cells

The Eyes Absent (EYA) proteins combine transactivation, tyrosine phosphatase, and threonine phosphatase activities in their function as part of a conserved regulatory cascade involved in embryonic organ development. EYA tyrosine phosphatase activity contributes to fly eye development, and vertebrate EYA is involved in promoting DNA damage repair subsequent to genotoxic stress. EYAs are known to be expressed at elevated levels in ovarian and breast cancers. Here, we show that the tyrosine phosphatase activity of the EYAs promotes tumor cell migration, invasion, and transformation. These cellular effects are accompanied by alterations of the actin cytoskeleton and increased levels of active Rac and Cdc42. The invasiveness conferred by EYA is reflected in vivo by inhibition of metastasis seen when EYA3 expression is silenced in the invasive breast cancer cell line MDA-MB-231. Together, our data directly associate the tyrosine phosphatase activity of the EYAs with the oncogenesis-associated cellular properties of motility and invasiveness.

Attenuation of Forkhead signaling by the retinal determination factor DACH1

The Drosophila Dachshund (Dac) gene, cloned as a dominant inhibitor of the hyperactive growth factor mutant ellipse, encodes a key component of the retinal determination gene network that governs cell fate. Herein, cyclic amplification and selection of targets identified a DACH1 DNA-binding sequence that resembles the FOX (Forkhead box-containing protein) binding site. Genome-wide in silico promoter analysis of DACH1 binding sites identified gene clusters populating cellular pathways associated with the cell cycle and growth factor signaling. ChIP coupled with high-throughput sequencing mapped DACH1 binding sites to corresponding gene clusters predicted in silico and identified as weight matrix resembling the cyclic amplification and selection of targets-defined sequence. DACH1 antagonized FOXM1 target gene expression, promoter occupancy in the context of local chromatin, and contact-independent growth. Attenuation of FOX function by the cell fate determination pathway has broad implications given the diverse role of FOX proteins in cellular biology and tumorigenesis.

The Dachshund gene in development and hormone-responsive tumorigenesis

The dachshund (dac) gene was initially described as a mutant phenotype in flies featuring extremely short legs relative to their body length. Functioning as a dominant suppressor of the ellipse mutation, a hypermorphic allele of the Epidermal Growth Factor Receptor (EGFR), the dac gene plays a key role in metazoan development, regulating ocular, limb, brain, and gonadal development. In the Drosophila eye, dac is a key component of the Retinal Determination Gene Network (RDGN) governing the normal initiation of the morphogenetic furrow and thereby eye development. Recent studies have demonstrated an important role for human Dachshund homologue (DACH1) in tumorigenesis, in particular, breast, prostate and ovarian cancer. The molecular mechanisms by which DACH1 regulates differentiation and tumorigenesis are discussed herein.

Inhibition of Eyes Absent Homolog 4 expression induces malignant peripheral nerve sheath tumor necrosis

Malignant peripheral nerve sheath tumors (MPNSTs) are aggressive sarcomas without effective therapeutics. Bioinformatics was used to identify potential therapeutic targets. Paired Box (PAX), Eyes Absent (EYA), Dachsund (DACH), and Sine Oculis (SIX) genes, which form a regulatory interactive network in drosophila, were found to be dysregulated in human MPNST cell lines and solid tumors. We identified a decrease in DACH1 expression, and increases in expression of PAX6, EYA1, EYA2, EYA4, and SIX1- 4. Consistent with the observation that half of MPNSTs develop in neurofibromatosis type 1 patients, subsequent to NF1 mutation, we found that exogenous expression of the NF1-GAP related domain (GRD) normalized DACH1 expression. EYA4 mRNA was elevated more than 100-fold as estimated by quantitative real time PCR in most MPSNT cell lines. In vitro, suppression of EYA4 expression using shRNA reduced cell adhesion and migration and caused cellular necrosis without affecting cell proliferation or apoptotic cell death. MPNST cells expressing sh-EYA4 either failed to form tumors in nude mice or formed very small tumors, with extensive necrosis but similar levels of proliferation and apoptosis as control cells. Our findings identify a role for EYA4 and possibly interacting SIX and DACH proteins in MPNSTs and suggest the EYA4 pathway as a rational therapeutic target.

The cell fate determination factor DACH1 is expressed in estrogen receptor-alpha-positive breast cancer and represses estrogen receptor-alpha signaling

The Dachshund (dac) gene, initially cloned as a dominant inhibitor of the Drosophila hyperactive EGFR mutant ellipse, encodes a key component of the cell fate determination pathway involved in Drosophila eye development. Analysis of more than 2,200 breast cancer samples showed improved survival by some 40 months in patients whose tumors expressed DACH1. Herein, DACH1 and estrogen receptor-alpha (ERalpha) expressions were inversely correlated in human breast cancer. DACH1 bound and inhibited ERalpha function. Nuclear DACH1 expression inhibited estradiol (E(2))-induced DNA synthesis and cellular proliferation. DACH1 bound ERalpha in immunoprecipitation-Western blotting, associated with ERalpha in chromatin immunoprecipitation, and inhibited ERalpha transcriptional activity, requiring a conserved DS domain. Proteomic analysis identified proline, glutamic acid, and leucine rich protein 1 (PELP1) as a DACH1-binding protein. The DACH1 COOH terminus was required for binding to PELP1. DACH1 inhibited induction of ERalpha signaling. E(2) recruited ERalpha and disengaged corepressors from DACH1 at an endogenous ER response element, allowing PELP1 to serve as an ERalpha coactivator. DACH1 expression, which is lost in poor prognosis human breast cancer, functions as an endogenous inhibitor of ERalpha function.

The cell fate determination factor dachshund inhibits androgen receptor signaling and prostate cancer cellular growth

Initially isolated as the dominant suppressor of the mutant epidermal growth factor receptor (ellipse), the Dachshund gene plays a key role in metazoan development regulating the Retinal Determination Gene Network. Herein, the DACH1 gene was expressed in normal prostate epithelial cells with reduced expression in human prostate cancer. DACH1 inhibited prostate cancer cellular DNA synthesis, growth in colony forming assays, and blocked contact-independent growth in soft agar assays. DACH1 inhibited androgen receptor (AR) activity, requiring a conserved DS Domain (Dachshund domain conserved with Ski/Sno) that bound NCoR/HDAC and was recruited to an androgen-responsive gene promoter. DACH1 inhibited ligand-dependent activity of AR mutations identified in patients with androgen-insensitive prostate cancer. The DS domain was sufficient for repression of the AR wild-type but failed to repress an AR acetylation site point mutant. These studies show a role for the Retinal Determination Gene Network in regulating cellular growth and signaling in prostate cancer.

The six family of homeobox genes in development and cancer

The homeobox gene superfamily encodes transcription factors that act as master regulators of development through their ability to activate or repress a diverse range of downstream target genes. Numerous families exist within the homeobox gene superfamily, and are classified on the basis of conservation of their homeodomains as well as additional motifs that contribute to DNA binding and to interactions with other proteins. Members of one such family, the Six family, form a transcriptional complex with Eya and Dach proteins, and together these proteins make up part of the retinal determination network first identified in Drosophila. This network is highly conserved in both invertebrate and vertebrate species, where it influences the development of numerous organs in addition to the eye, primarily through regulation of cell proliferation, survival, migration, and invasion. Mutations in Six, Eya, and Dach genes have been identified in a variety of human genetic disorders, demonstrating their critical role in human development. In addition, aberrant expression of Six, Eya, and Dach occurs in numerous human tumors, and Six1, in particular, plays a causal role both in tumor initiation and in metastasis. Emerging evidence for the importance of Six family members and their cofactors in numerous human tumors suggests that targeting of this complex may be a novel and powerful means to inhibit both tumor growth and progression.

A new cross-talk between the aryl hydrocarbon receptor and RelB, a member of the NF-kappaB family

The discovery of the new crosstalk between the aryl hydrocarbon receptor (AhR) and the NF-kappaB subunit RelB may extend our understanding of the biological functions of the AhR and at the same time raises a number of questions, which will be addressed in this review. The characteristics of this interaction differ from that of AhR with RelA in that the latter appears to be mostly negative unlike the collaborative interactions of AhR/RelB. The AhR/RelB dimer is capable of binding to DNA response elements including the dioxin response element (DRE) as well as NF-kappaB binding sites supporting the activation of target genes of the AhR as well as NF-kappaB pathway. Further studies show that AhR/RelB complexes can be found not only in lymphoid cells but also in a human hepatoma cell line (HepG2) or breast cancer cell line (MDA-MB-231). RelB has been implicated in carcinogenesis of breast cancer for instance and RelB is known to be a critical factor for the function and differentiation of dendritic cells; interestingly the participation of AhR in both processes has been suggested recently, which offers the great potential to expand the scope of the physiological roles of the AhR. There is evidence indicating that RelB may serve as a pro-survival factor, including its ability to promote "inflammation resolution" besides the association of RelB with inflammatory disorders. Based on such information, a hypothesis has been proposed in this review that AhR together with RelB functions as a coordinator of inflammatory responses.