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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.

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 Res; 73(14); 4488–99. ©2013 AACR.

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 >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

Lung cancer is the leading cause of cancer death worldwide. A key driver to the proliferation of lung cancer includes increased activity of the gene encoding the epidermal growth factor receptor (EGFR) and mutation of K-ras oncogene. Target therapies through small molecules to inhibit the tyrosine kinase domain of EGFR (Gefitinib) or monoclonal antibody to EGFR (Cetuximab) have demonstrated clinical benefit. Unfortunately, development of resistance to those treatments occurs in most patients within one year. Studies of the hyperactive EGFR in drosophila identified a genetic inhibitor of EGFR signaling, known as dachshund (dac). Activate ras inhibits DACH1 expression in malignant peripheral nerve sheath tumor. Dachshund can activate or represses transcription, and regulates cell proliferation and differentiation in multiple context-dependent manners. Our studies have proved that DACH1, human homolog of dac, functions as a potential tumor suppressor of breast and prostate cancer. Expression of DACH1 is lost during cancer progression and re-expression of DACH1 gene inhibited cellular proliferation, migration and tumor formation. The expression levels and the role of DACH1 in lung cancer are largely unknown. As both EGFR and Ras signaling interact with DACH1, we hypotheses that loss of endogenous DACH1 may contribute to the lung tumorigenesis. The mRNA expression of DACH1 was decreased in lung adenocarcinoma compared with normal lung tissues. Ectopic expression of DACH1 by stably transduction inhibited cellular proliferation of lung cancer cell lines A549 and SKLU, cell cycle progression and clone formation rate in contact-dependent and -independent growth. ELISA using conditional medium from A549 cells expressing vector control or DACH1 demonstrated remarkable inhibition of secreting factors, such as CXCL1, CXCL2, CXCL5 and CXCL8. Those chemokines have already been proved to positively regulating angiogenesis and proliferation. To test in vivo tumorigenesis, 2x106 A549 cells expressing DACH1 or vector control were injected subcutaneously into nude mouse and tumor size was monitored weekly. Tumor growth was dramatically blocked by DACH1. Tumor weight was 297.8 ± 38.6mg for vector control and 31 ± 6.1mg for cells expressing DACH1(p value Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 4157. doi:1538-7445.AM2012-4157