The retinal determination gene network: from developmental regulator to cancer therapeutic target

Deletion of adipocyte Sine Oculis Homeobox Homolog 1 prevents lipolysis and attenuates skin fibrosis

Background

The cardinal feature of systemic sclerosis (SSc) is skin thickening and tightening. Targetable mechanisms for skin features remain elusive. Drugs successful in treating internal organ manifestations have failed efficacy in skin. Dermal white adipose tissue (DWAT) is amongst the understudied contributors to skin manifestations. This study proposes the role of sine oculis homeobox homolog 1 (SIX1), a gene previously unrecognized as a contributor to dermal lipoatrophy characteristic of early skin fibrosis in SSc.

Methods

Skin gene expression of SIX1 was analyzed in the GENISOS and PRESS SSc cohorts. Correlation analysis was performed with Spearman rank analysis. Novel mouse models were developed using the Cre-loxp system to knock out Six1 in all cells and mature adipocytes. Subcutaneous bleomycin was used to model early DWAT atrophy and dermal fibrosis characteristic of SSc.

Findings

SIX1 was upregulated in SSc skin, the expression of which correlates with adipose-associated genes and molecular pathways. Genetic deletion of Six1 in all cells in mice challenged with bleomycin abrogated end-stage fibrotic gene expression and dermal adipocyte shrinkage. Adipocyte specific Six1 deletion was able to attenuate the early increase in skin thickness, a hallmark of experimental skin fibrosis. Further studies revealed a link between elevated SIX1 and increased expression of SERPINE1 and its protein PAI-1 which are known pro-fibrotic mediators.

Interpretation

This work identifies SIX1 as an early marker of skin fibrosis in SSc. We also demonstrate a causative role of Six1 in skin fibrosis by promoting adipocyte loss and show that deletion of Six1 in adipocytes has the potential of impacting early disease progression.

All eyes on Eya: A unique transcriptional co-activator and phosphatase in cancer

The Eya family of proteins (consisting of Eyas1-4 in mammals) play vital roles in embryogenesis by regulating processes such as proliferation, migration/invasion, cellular survival and pluripotency/plasticity of epithelial and mesenchymal states. Eya proteins carry out such diverse functions through a unique combination of transcriptional co-factor, Tyr phosphatase, and PP2A/B55α-mediated Ser/Thr phosphatase activities. Since their initial discovery, re-expression of Eyas has been observed in numerous tumor types, where they are known to promote tumor progression through a combination of their transcriptional and enzymatic activities. Eya proteins thus reinstate developmental processes during malignancy and represent a compelling class of therapeutic targets for inhibiting tumor progression.

S100A8/A9 as a risk factor for breast cancer negatively regulated by DACH1

BACKGROUND

S100A8 and S100A9 are members of Ca2+-binding EF-hand superfamily, mainly expressed by macrophages and neutrophils. Limited by the poor stability of homodimers, they commonly exist as heterodimers. Beyond acting as antibacterial cytokines, S100A8/A9 is also associated with metabolic and autoimmune diseases such as obesity, diabetes, and rheumatoid arthritis. While the involvement of S100A8/A9 in breast cancer development has been documented, its prognostic significance and the precise regulatory mechanisms remain unclear.

METHODS

S100A8/A9 protein in breast cancer samples was evaluated by immunohistochemistry staining with tumor tissue microarrays. The serum S100A8 concentration in patients was measured by enzyme-linked immunosorbent assay (ELISA). The S100A8 secreted by breast cancer cells was detected by ELISA as well. Pooled analyses were conducted to explore the relationships between S100A8/A9 mRNA level and clinicopathological features of breast cancer patients. Besides, the effects of S100A8/A9 and DACH1 on patient outcomes were analyzed by tissue assays. Finally, xenograft tumor assays were adopted to validate the effects of DACH1 on tumor growth and S100A8/A9 expression.

RESULTS

The level of S100A8/A9 was higher in breast cancer, relative to normal tissue. Increased S100A8/A9 was related to poor differentiation grade, loss of hormone receptors, and Her2 positive. Moreover, elevated S100A8/A9 predicted a worse prognosis for breast cancer patients. Meanwhile, serum S100A8 concentration was upregulated in Grade 3, basal-like, and Her2-overexpressed subtypes. Additionally, the results of public databases showed S100A8/A9 mRNA level was negatively correlated to DACH1. Stable overexpressing DACH1 in breast cancer cells significantly decreased the generation of S100A8. The survival analysis demonstrated that patients with high S100A8/A9 and low DACH1 achieved the shortest overall survival. The xenograft models indicated that DACH1 expression significantly retarded tumor growth and downregulated S100A8/A9 protein abundance.

CONCLUSION

S100A8/A9 is remarkedly increased in basal-like and Her2-overexpressed subtypes, predicting poor prognosis of breast cancer patients. Tumor suppressor DACH1 inhibits S100A8/A9 expression. The combination of S100A8/A9 and DACH1 predicted the overall survival of breast cancer patients more preciously.

DACH1 regulates macrophage activation and tumour progression in hypopharyngeal squamous cell carcinoma

Dachshund family transcription factor 1 (DACH1) has been shown to exhibit a tumour-suppressive role in a number of human cancers. However, the role of DACH1 in hypopharyngeal squamous cell carcinoma (HPSCC) and its function in the tumour microenvironment (TME) are still not clear. Crosstalk between cancer cells and tumour-associated macrophages (TAMs) mediates tumour progression in HPSCC. The expression of DACH1, CD86 and CD163 was detected in 71 matched HPSCC-non-cancerous tissue pairs using quantitative real-time polymerase chain reaction and IHC analysis. Cell proliferation, migration and invasion were monitored by colony formation, Transwell and EdU incorporation assays. ChIP-qPCR and dual-luciferase reporter assays were applied to verify the targeting relationships between DACH1 and IGF-1. Stably transfected HPSCC cells were co-cultured with MΦ macrophages to assess macrophage polarization and secretory signals. DACH1 was decreased in HPSCC tissues and was indicative of a poor prognosis for HPSCC patients. Decreased DACH1 expression in HPSCC was associated with fewer CD86+ TAMs and more CD163+ TAMs. Knockdown of DACH1 inhibited the proliferation, migration and invasion of FaDu cells via Akt/NF-κB/MMP2/9 signalling. Additionally, DACH1 was found to directly bind to the promoter region of IGF-1 to downregulate the secretion of IGF-1, which inhibited TAMs polarization through the IGF-1R/JAK1/STAT3 axis. Furthermore, in nude mice, the effects of DACH1 inhibition on tumour progression and M2-like TAMs polarization were confirmed. These findings suggest that IGF-1 is a critical downstream effector of DACH1 that suppresses cell migration and invasion and inhibits TAMs polarization. DACH1 could be a therapeutic target and prognostic marker for HPSCC.

The DACH1 gene is frequently deleted in prostate cancer, restrains prostatic intraepithelial neoplasia, decreases DNA damage repair, and predicts therapy responses

Prostate cancer (PCa), the second leading cause of death in American men, includes distinct genetic subtypes with distinct therapeutic vulnerabilities. The DACH1 gene encodes a winged helix/Forkhead DNA-binding protein that competes for binding to FOXM1 sites. Herein, DACH1 gene deletion within the 13q21.31-q21.33 region occurs in up to 18% of human PCa and was associated with increased AR activity and poor prognosis. In prostate OncoMice, prostate-specific deletion of the Dach1 gene enhanced prostatic intraepithelial neoplasia (PIN), and was associated with increased TGFβ activity and DNA damage. Reduced Dach1 increased DNA damage in response to genotoxic stresses. DACH1 was recruited to sites of DNA damage, augmenting recruitment of Ku70/Ku80. Reduced Dach1 expression was associated with increased homology directed repair and resistance to PARP inhibitors and TGFβ kinase inhibitors. Reduced Dach1 expression may define a subclass of PCa that warrants specific therapies.

The value of EYA1/3/4 in clear cell renal cell carcinoma: a study from multiple databases

There is evidence from multiple studies that dysregulation of the Eyes Absent (EYA) protein plays multiple roles in many cancers. Despite this, little is known about the prognostic significance of the EYAs family in clear cell renal cell carcinoma (ccRCC). We systematically analyzed the value of EYAs in Clear Cell Renal Cell Carcinoma. Our analysis included examining transcriptional levels, mutations, methylated modifications, co-expression, protein-protein interactions (PPIs), immune infiltration, single-cell sequencing, drug sensitivity, and prognostic values. We based our analysis on data from several databases, including the Cancer Genome Atlas database (TCGA), the Gene Expression Omnibus database (GEO), UALCAN, TIMER, Gene Expression Profiling Interactive Analysis (GEPIA), STRING, cBioPortal and GSCALite. In patients with ccRCC, the EYA1 gene was significantly highly expressed, while the expression of EYA2/3/4 genes showed the opposite trend. The level of expression of the EYA1/3/4 gene was significantly correlated with the prognosis and clinicopathological parameters of ccRCC patients. Univariate and multifactorial Cox regression analyses revealed EYA1/3 as an independent prognostic factor for ccRCC, establishing nomogram line plots with good predictive power. Meanwhile, the number of mutations in EYAs was also significantly correlated with poor overall survival (OS) and progression-free survival (PFS) of patients with ccRCC. Mechanistically, EYAs genes play an essential role in a wide range of biological processes such as DNA metabolism and double-strand break repair in ccRCC. The majority of EYAs members were related to the infiltration of immune cells, drug sensitivity, and methylation levels. Furthermore, our experiment confirmed that EYA1 gene expression was upregulated, and EYA2/3/4 showed low expression in ccRCC. The increased expression of EYA1 might play an important role in ccRCC oncogenesis, and the decreased expression of EYA3/4 could function as a tumor suppressor, suggesting EYA1/3/4 might serve as valuable prognostic markers and potential new therapeutic targets for ccRCC.

DACH1 inhibits the proliferation and migration of papillary thyroid carcinoma

DACH1 is an important component of the retinal determinate gene network (RDGN), which regulates the expression of target genes by directly binding or interacting with other factors. DACH1 shows inhibitory effects in most tumors, but its role in papillary thyroid carcinoma is unclear and warrants further investigation. We assessed the expression of DACH1 in different tissues and correlation with immune infiltration by The Cancer Genome Atlas (TCGA) and Tumor Immune Estimation Resource (TIMMER2.0 databases). The effects of DACH1 on the proliferation and migration of TPC-1 and Bcpap cells were assessed by cell viability assay, colony formation assay, wound healing assay, transwell migration assay, and flow cytometry. Finally, the effects of DACH1 on CXCL8, CXCL10, and CXCL12 expression in Nthy-ori-3-1, TPC-1 and Bcpap cells were assessed by enzyme-linked immunosorbent assay kit and real-time polymerase chain reaction, respectively. The results showed that DACH1 was differentially expressed in different tumors and tissues. Basal expression of DACH1 was lower in thyroid and papillary thyroid carcinoma than in other normal tissues and corresponding tumors, and positively correlated with CD8⁺ T cell infiltration. In Nthy-ori-3-1, TPC-1 and Bcpap cells, overexpression of DACH1 inhibited cell migration and proliferation, and the opposite results was obtained by knocking down DACH1 using small interfering RNA. We also demonstrated that DACH1 regulated chemokines CXCL8, CXCL10, and CXCL12, thereby modulating tumor immunity.

Retinal determination gene networks: from biological functions to therapeutic strategies

The retinal determinant gene network (RDGN), originally discovered as a critical determinator in Drosophila eye specification, has become an important regulatory network in tumorigenesis and progression, as well as organogenesis. This network is not only associated with malignant biological behaviors of tumors, such as proliferation, and invasion, but also regulates the development of multiple mammalian organs. Three members of this conservative network have been extensively investigated, including DACH, SIX, and EYA. Dysregulated RDGN signaling is associated with the initiation and progression of tumors. In recent years, it has been found that the members of this network can be used as prognostic markers for cancer patients. Moreover, they are considered to be potential therapeutic targets for cancer. Here, we summarize the research progress of RDGN members from biological functions to signaling transduction, especially emphasizing their effects on tumors. Additionally, we discuss the roles of RDGN members in the development of organs and tissue as well as their correlations with the pathogenesis of chronic kidney disease and coronary heart disease. By summarizing the roles of RDGN members in human diseases, we hope to promote future investigations into RDGN and provide potential therapeutic strategies for patients.

The DACH1 gene is frequently deleted in prostate cancer, restrains prostatic intraepithelial neoplasia, decreases DNA damage repair, and predicts therapy responses

Prostate cancer (PCa), the second leading cause of death in American men, includes distinct genetic subtypes with distinct therapeutic vulnerabilities. The DACH1 gene encodes a winged helix/Forkhead DNA-binding protein that competes for binding to FOXM1 sites. Herein, DACH1 gene deletion within the 13q21.31-q21.33 region occurs in up to 18% of human PCa and was associated with increased AR activity and poor prognosis. In prostate OncoMice, prostate-specific deletion of the Dach1 gene enhanced prostatic intraepithelial neoplasia (PIN), and was associated with increased TGFb activity and DNA damage. Reduced Dach1 increased DNA damage in response to genotoxic stresses. DACH1 was recruited to sites of DNA damage, augmenting recruitment of Ku70/Ku80. Reduced Dach1 expression was associated with increased homology directed repair and resistance to PARP inhibitors and TGFb kinase inhibitors. Reduced Dach1 expression may define a subclass of PCa that warrants specific therapies.

VEGF-C mediates tumor growth and metastasis through promoting EMT-epithelial breast cancer cell crosstalk

It is well established that a subset of cells within primary breast cancers can undergo an epithelial-to-mesenchymal transition (EMT), although the role of EMT in metastasis remains controversial. We previously demonstrated that breast cancer cells that had undergone an oncogenic EMT could increase metastasis of neighboring cancer cells via non-canonical paracrine-mediated activation of GLI activity that is dependent on SIX1 expression in the EMT cancer cells. However, the mechanism by which these SIX1-expressing EMT cells activate GLI signaling remained unclear. In this study, we demonstrate a novel mechanism for activation of GLI-mediated signaling in epithelial breast tumor cells via EMT cell-induced production and secretion of VEGF-C. We show that VEGF-C, secreted by breast cancer cells that have undergone an EMT, promotes paracrine-mediated increases in proliferation, migration, and invasion of epithelial breast cancer cells, via non-canonical activation of GLI-signaling. We further show that the aggressive phenotypes, including metastasis, imparted by EMT cells on adjacent epithelial cancer cells can be disrupted by either inhibiting VEGF-C in EMT cells or by knocking down NRP2, a receptor which interacts with VEGF-C, in neighboring epithelial cancer cells. Interrogation of TCGA and GEO public datasets supports the relevance of this pathway in human breast cancer, demonstrating that VEGF-C strongly correlates with activation of Hedgehog signaling and EMT in the human disease. Our study suggests that the VEGF-C/NRP2/GLI axis is a novel and conserved paracrine means by which EMT cells enhance metastasis, and provides potential targets for therapeutic intervention in this heterogeneous disease.

RDGN-based predictive model for the prognosis of breast cancer

Background

Breast cancer is the most diagnosed malignancy in females in the United States. The members of retinal determination gene network (RDGN) including DACH, EYA, as well as SIX families participate in the proliferation, apoptosis, and metastasis of multiple tumors including breast cancer. A comprehensive predictive model of RDGN might be helpful to herald the prognosis of breast cancer patients.

Methods

In this study, the Gene Expression Ominibus (GEO) and Gene Set Expression Analysis (GSEA) algorithm were used to investigate the effect of RDGN members on downstream signaling pathways. Besides, based on The Cancer Genome Atlas (TCGA) database, we explored the expression patterns of RDGN members in tumors, normal tissues, and different breast cancer subtypes. Moreover, we estimated the relationship between RDGN members and the outcomes of breast cancer patients. Lastly, we constructed a RDGN-based predictive model by Cox proportional hazard regression and verified the model in two separate GEO datasets.

Results

The results of GSEA showed that the expression of DACH1 was negatively correlated with cell cycle and DNA replication pathways. On the contrary, the levels of EYA2 and SIX1 were significantly positively correlated with DNA replication, mTOR, and Wnt pathways. Further investigation in TCGA database indicated that DACH1 expression was lower in breast cancers especially basal-like subtype. In the meanwhile, SIX1 was remarkably upregulated in breast cancers while EYA2 level was increased in Basal-like and Her-2 enriched subtypes. Survival analyses demonstrated that DACH1 was a favorable factor while EYA2 and SIX1 were risk factors for breast cancer patients. Given the results of Cox proportional hazard regression analysis, two members of RDGN were involved in the present predictive model and patients with high model index had poorer outcomes.

Conclusion

This study showed that aberrant RDGN expression was an unfavorable factor for breast cancer. This RDGN-based comprehensively framework was meaningful for predicting the prognosis of breast cancer patients.

The PAX-SIX-EYA-DACH network modulates GATA-FOG function in fly hematopoiesis and human erythropoiesis

The GATA and PAX-SIX-EYA-DACH transcriptional networks (PSEDNs) are essential for proper development across taxa. Here, we demonstrate novel PSEDN roles in vivo in Drosophila hematopoiesis and in human erythropoiesis in vitro Using Drosophila genetics, we show that PSEDN members function with GATA to block lamellocyte differentiation and maintain the prohemocyte pool. Overexpression of human SIX1 stimulated erythroid differentiation of human erythroleukemia TF1 cells and primary hematopoietic stem-progenitor cells. Conversely, SIX1 knockout impaired erythropoiesis in both cell types. SIX1 stimulation of erythropoiesis required GATA1, as SIX1 overexpression failed to drive erythroid phenotypes and gene expression patterns in GATA1 knockout cells. SIX1 can associate with GATA1 and stimulate GATA1-mediated gene transcription, suggesting that SIX1-GATA1 physical interactions contribute to the observed functional interactions. In addition, both fly and human SIX proteins regulated GATA protein levels. Collectively, our findings demonstrate that SIX proteins enhance GATA function at multiple levels, and reveal evolutionarily conserved cooperation between the GATA and PSEDN networks that may regulate developmental processes beyond hematopoiesis.

SIX1 Activates STAT3 Signaling to Promote the Proliferation of Thyroid Carcinoma via EYA1

As a critical member of the Retinal Determination Gene Network (RDGN), SIX1 has been regarded as a tumor promoter in various types of cancer. However, its role in papillary thyroid carcinoma (PTC) has never been investigated. In this study, thyroid carcinoma tissue microarray staining was employed to identify the expression patterns of SIX1 and its co-activator EYA1. Papillary thyroid cancer cell lines, BCPAP, and TPC-1 cells were used to investigate the potential mechanism of SIX1 in vitro and in vivo. Flow cytometry analysis, MTT assay, the growth curve assay, colony formation assay, EdU incorporation and xenograft assay were performed to demonstrate the role of SIX1 in the malignant change of PTC cells. Western blot and Real-time PCR were used to detect the interaction among the SIX1, EYA1, and STAT3 signaling. In comparison with normal tissue, high expressions of SIX1 and EYA1 were associated with a malignant tumor. Importantly, SIX1 strongly correlated with EYA1 in thyroid carcinoma tissue microarray. Functional assays indicated SIX1 increased EYA1 expression by stabilizing EYA1 at the post-transcriptional level. Besides, SIX1 promoted the proliferation and invasion of thyroid carcinoma via activation of STAT3 signaling and its downstream targets in an EYA1-dependent manner. SIX1 can integrate with EYA1 to contribute to PTC development via activation of the classical STAT3 signaling. These data suggested targeting the abnormal activation of the SIX1/EYA1 complex may represent a novel therapeutic strategy for advanced PTC patients.

Integrated transcriptomics reveals master regulators of lung adenocarcinoma and novel repositioning of drug candidates

BACKGROUND

Lung adenocarcinoma is the major cause of cancer-related deaths in the world. Given this, the importance of research on its pathophysiology and therapy remains a key health issue. To assist in this endeavor, recent oncology studies are adopting Systems Biology approaches and bioinformatics to analyze and understand omics data, bringing new insights about this disease and its treatment.

METHODS

We used reverse engineering of transcriptomic data to reconstruct nontumorous lung reference networks, focusing on transcription factors (TFs) and their inferred target genes, referred as regulatory units or regulons. Afterwards, we used 13 case-control studies to identify TFs acting as master regulators of the disease and their regulatory units. Furthermore, the inferred activation patterns of regulons were used to evaluate patient survival and search drug candidates for repositioning.

RESULTS

The regulatory units under the influence of ATOH8, DACH1, EPAS1, ETV5, FOXA2, FOXM1, HOXA4, SMAD6, and UHRF1 transcription factors were consistently associated with the pathological phenotype, suggesting that they may be master regulators of lung adenocarcinoma. We also observed that the inferred activity of FOXA2, FOXM1, and UHRF1 was significantly associated with risk of death in patients. Finally, we obtained deptropine, promazine, valproic acid, azacyclonol, methotrexate, and ChemBridge ID compound 5109870 as potential candidates to revert the molecular profile leading to decreased survival.

CONCLUSION

Using an integrated transcriptomics approach, we identified master regulator candidates involved with the development and prognostic of lung adenocarcinoma, as well as potential drugs for repurposing.

MiR-150-5p regulates melanoma proliferation, invasion and metastasis via SIX1-mediated Warburg Effect

Aerobic glycolysis is a hallmark of cancer. Sine oculis homeobox 1 (SIX1), a key transcription factor in terms of regulating aerobic glycolysis (the Warburg Effect), plays a critical role in tumorigenesis of various cancer types, including breast cancer, liver cancer, and lung cancer. However, the upstream regulating mechanisms of SIX1 in melanoma remain to be determined. MicroRNAs (miRNAs) have emerged as key regulators in tumorigenesis and progression. Here, we initially showed that microRNA-150-5p (miR-150-5p) inhibits SIX1 expression by directly targeting its 3'-UTR in melanoma cells. miR-150-5p suppressed melanoma cell proliferation, migration, and invasion through inhibition of SIX1. Mechanistically, miR-150-5p dampens glycolysis by decreasing the glucose uptake, lactate production, ATP generation, and extracellular acidification rate (ECAR), and increasing oxygen consumption rate (OCR) by targeting SIX1. Importantly, glycolysis regulated by miR-150-5p/SIX1 axis is critical for its regulation of melanoma growth and metastasis both in vitro and in vivo. Collectively, our study demonstrates the importance of miR-150-5p/SIX1 axis in melanoma, which could be a promising therapeutic target in melanoma.

EYA1 promotes cell migration and tumor metastasis in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) patients are at high risk for both local recurrence and distant metastasis and tightly associated with poor prognosis. Exploring the molecular mechanism will provide a new opportunity in developing personal treatment for advanced HCC patients. As a critical member of the Retinal Determination Gene Network (RDGN), EYA1 has been identified as a tumor promoter in various cancers; however, its role in HCC has never been investigated. The present study was aimed to explore the role of EYA1 in HCC development. By analyzing public microarray datasets, we found that the EYA1 mRNA level was enhanced in HCC, which was significantly correlated with an aggressive phenotype and poor prognosis. Besides, EYA1 was coordinated with the fibronectin type III domain containing 3B (FNDC3B) to promote the migration and invasion of HCC cells. Western blot assays indicated that EYA1 not only increased the abundance of FNDC3B but also contributed to Epithelial-Mesenchymal Transition (EMT)-like phenotype change, like increased N-cadherin and decreased E-cadherin expression. Collectively, this study suggested that EYA1 activated FNDC3B to promote the migration and invasion in HCC. The aberrant expressions of EYA1 and FNDC3B may become the poor predictors for HCC patients.

EYA2 Correlates With Clinico-Pathological Features of Breast Cancer, Promotes Tumor Proliferation, and Predicts Poor Survival

Eyes absent homolog 2 (EYA2), a transcriptional activator, is pivotal for organ development, but aberrant regulation of EYA2 has been reported in multiple human tumors. However, the role of EYA2 in breast cancer is still lack of full understanding. To explore the biological significance of EYA2 in breast cancer, we conducted data analysis on public breast cancer datasets, and performed immunohistochemistry (IHC) analysis, colony-forming unit assays, EdU assay, western blotting, and immunofluorescence (IF). Meta-analysis showed that EYA2 mRNA expression was correlated with tumor grade, the status of estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor 2 (HER2). IHC analysis displayed that EYA2 protein abundance was inversely associated with the status of ER and PR, and enriched in triple-negative breast cancer in comparison with luminal-type tumors. Additionally, correlation analysis reflected that EYA2 mRNA was negatively correlated with luminal markers, and positively associated with markers of basal cells, epithelial-mesenchymal transition and cancer stem cells. Clone-forming assay and EdU experiment showed that EYA2 overexpression enhanced proliferation of breast cancer cells. Results from western blotting and IF displayed that overexpression of EYA2 up-regulated the protein abundance of proliferation markers. Importantly, survival analysis indicated that higher EYA2 mRNA level predicted worse overall survival, relapse-free survival and metastasis-free survival among whole enrolled breast cancer patients. Collectively, EYA2 was closely correlated with clinico-pathological characteristics, and served as a proliferation stimulator for breast cancer cells and an unfavorable prognostic element for breast cancer patients, suggesting that EYA2 is involved in the progression of breast carcinoma.

Regulation of cancer stem cell properties by SIX1, a member of the PAX-SIX-EYA-DACH network

The PAX-SIX-EYA-DACH network (PSEDN) is a central developmental transcriptional regulatory network from Drosophila to humans. The PSEDN is comprised of four conserved protein families; including paired box (PAX), sine oculis (SIX), eyes absent (EYA), and dachshund (DACH). Aberrant expression of PSEDN members, particularly SIX1, has been observed in multiple human cancers, where SIX1 expression correlates with increased aggressiveness and poor prognosis. In conjunction with its transcriptional activator EYA, the SIX1 transcription factor increases cancer stem cell (CSC) numbers and induces epithelial-mesenchymal transition (EMT). SIX1 promotes multiple hallmarks and enabling characteristics of cancer via regulation of cell proliferation, senescence, apoptosis, genome stability, and energy metabolism. SIX1 also influences the tumor microenvironment, enhancing recruitment of tumor-associated macrophages and stimulating angiogenesis, to promote tumor development and progression. EYA proteins are multifunctional, possessing a transcriptional activation domain and tyrosine phosphatase activity, that each contributes to cancer stem cell properties. DACH proteins function as tumor suppressors in solid cancers, opposing the actions of SIX-EYA and reducing CSC prevalence. Multiple mechanisms can lead to increased SIX1 expression, including loss of SIX1-targeting tumor suppressor microRNAs (miRs), whose expression correlates inversely with SIX1 expression in cancer patient samples. In this review, we discuss the major mechanisms by which SIX1 confers CSC and EMT features and other important cancer cell characteristics. The roles of EYA and DACH in CSCs and cancer progression are briefly highlighted. Finally, we summarize the clinical significance of SIX1 in cancer to emphasize the potential therapeutic benefits of effective strategies to disrupt PSEDN protein interactions and functions.

The regulation of cytokine signaling by retinal determination gene network pathway in cancer

Tumor environment plays a pivotal role in determining cancer biology characteristics. Cytokine factors, as a critical component in tumor milieu, execute distinct functions in the process of tumorigenesis and progression via the autocrine or paracrine manner. The retinal determination gene network (RDGN), which mainly comprised DACH, SIX, and EYA family members, is required for the organ development in mammalian species. While the aberrant expression of RDGN is involved in the proliferation, apoptosis, angiogenesis, and metastasis of tumors via interacting with different cytokine-related signals, such as CXCL8, IL-6, TGF-β, FGF, and VEGF, in a cell- or tissue-dependent manner. Thus, joint detection of this pathway might be used as a potential biomarker for the stratification of target therapy and for the precision prediction of the prognosis of cancer patients.

The Protein Tyrosine Phosphatase Activity of Eyes Absent Contributes to Tumor Angiogenesis and Tumor Growth

DNA damage repair capacity is required for cells to survive catastrophic DNA damage and proliferate under conditions of intratumoral stress. The ability of the minor histone protein H2AX to serve as a hub for the assembly of a productive DNA damage repair complex is a necessary step in preventing DNA damage-induced cell death. The Eyes Absent (EYA) proteins dephosphorylate the terminal tyrosine residue of H2AX, thus permitting assembly of a productive DNA repair complex. Here, we use genetic and chemical biology approaches to separately query the roles of host vascular endothelial cell and tumor cell EYA in tumor growth. Deletion of Eya3 in host endothelial cells significantly reduced tumor angiogenesis and limited tumor growth in xenografts. Deletion of Eya3 in tumor cells reduced tumor cell proliferation and tumor growth without affecting tumor angiogenesis. A chemical inhibitor of the EYA tyrosine phosphatase activity inhibited both tumor angiogenesis and tumor growth. Simultaneously targeting the tumor vasculature and tumor cells is an attractive therapeutic strategy because it could counter the development of the more aggressive phenotype known to emerge from conventional antiangiogenic agents. Mol Cancer Ther; 17(8); 1659-69. ©2018 AACR.

DACH1 antagonizes CXCL8 to repress tumorigenesis of lung adenocarcinoma and improve prognosis

BACKGROUND

C-X-C motif ligand 8 (CXCL8), known as a proinflammatory chemokine, exerts multiple effects on the proliferation, invasion, and migration of tumor cells via the autocrine or paracrine manner. Conversely, the human Dachshund homologue 1 (DACH1) is recognized as a tumor suppressor which retards the progression of various cancers. In prostate cancer, it has been demonstrated that DACH1 was negatively correlated with the expression of CXCL8 and able to antagonize the effects of CXCL8 on cellular migration. Herein, we explored the mechanisms by which DACH1 regulated the CXCL8 in non-small cell lung cancer (NSCLC).

METHODS

Public microarray and Kaplan-Meier plotter datasets were analyzed. Blood serum samples from lung adenocarcinoma (ADC) patients were collected for enzyme-linked immunosorbent assay (ELISA) analysis. Immunohistochemical staining was conducted on tissue microarray. Cell lines with stable expression of DACH1 were established, and relative gene expression was measured by Western blot, ELISA, real-time PCR, and human cytokine array. Correspondingly, cell lines transfected with shDACH1 were established, and relative gene expression was measured by real-time PCR and immunofluorescence array. Functional studies were performed by transwell and xenograft mice models. Luciferase reporter gene assay was applied to measure the regulation of DACH1 on CXCL8.

RESULTS

Our study indicated that CXCL8 both at the mRNA and protein level was associated with the high tumor burden of ADC. Correlational analyses in ADC cell lines and ADC tissues showed that DACH1 was inversely correlated with CXCL8. Meanwhile, patients with high DACH1 expression and low CXCL8 expression had prolonged time to death and recurrence. Moreover, we verified the inhibitory effects of DACH1 on CXCL8 both in vitro and in vivo. Mechanism studies proved that DACH1 transcriptionally repressed CXCL8 promoter activity through activator protein-1 (AP-1) and nuclear transcription factor-kappa B (NF-κB) sites.

CONCLUSIONS

Our study proved that CXCL8 acted as an unfavorable factor promoting to tumor progression and poor prognosis of ADC, while DACH1 antagonized CXCL8 to provide a favorable survival of ADC patients. Double detection of DACH1 and CXCL8 may provide a precise information for further evaluating the prognosis of ADC patients.

Alteration of DACH1 methylation patterns in lung cancer contributes to cell proliferation and migration

Lung cancer is the most common cause of cancer-related death. Non-small cell lung cancer (NSCLC) accounts for 80%-85% of total lung cancer cases. Dachshund homolog 1 (DACH1), is a protein encoded by the DACH1 gene in humans. DACH1 inhibits lung adenocarcinoma invasion and tumor growth but has a lower expression in NSCLC. To investigate the mechanisms of decreased DACH1 expression, its DNA methylation patterns were investigated. The results showed a higher methylation rate in NSCLC compared with the adjacent normal lung tissues. Cell transfection experiments showed that increased methylation impaired transcription factor transactivation. In vivo demethylation treatment and overexpression of DACH1 increased apoptosis and decreased migration and invasion in NSCLC A549 cells. Our research provides new insight into NSCLC pathogenesis and identifies a new therapeutic target.

EYA1 promotes tumor angiogenesis by activating the PI3K pathway in colorectal cancer

Blood vessels are one of the major routes for the dissemination of cancer cells. Malignant tumors release growth factors such as vascular endothelial growth factor(VEGF) to induce angiogenesis, thereby promoting metastasis. Here, we report that The Drosophila Eyes Absent Homologue 1 (EYA1), which is overexpressed in colorectal tumor cells, can promote colorectal tumor angiogenesis by coordinating with the hypoxia-inducible factor 1 (HIF-1α) to increase the expression of VEGF-A. Moreover, data indicated that the enhancement of HIF-1α expression by Eya1 depended on its ability to activate the phosphatidylinositol 3-kinase (PI3K) signaling pathways to increase the phosphorylation of AKT subunits. Overexpression of Eya1 increased tumor angiogenesis in vivo and in vitro. Our study suggested that Eya1 is essential in regulating cancer cell-mediated angiogenesis and contributes to tumor growth, and that Eya1 provides a potential and specific target for new anti-angiogenesis drug development.

EYA2 promotes lung cancer cell proliferation by downregulating the expression of PTEN

Lung cancer is the leading cause of cancer-related death worldwide. Despite advances have been made in diagnosis and therapeutic strategies, the prognosis of lung cancer is still very poor. Eyes absent transcriptional cofactor EYA2 has been shown to promote lung cancer cell growth, however, the underlying molecular mechanism is still not fully understood. In the present study, we found that EYA2 was up-regulated in lung cancer, and EYA2 led to increased cell proliferation by inhibiting Phosphatase and tensin homologue (PTEN) expression via modulation of miR-93. Additionally, survival analysis showed that lung cancer patients with higher EYA2 expression predicted a worse prognosis. Therefore, these findings demonstrate that EYA2 may play an important role in lung cancer occurrence and progression. Targeting EYA2 may provide a feasible approach in developing novel anticancer therapeutics.

The Eya phosphatase: Its unique role in cancer

The Eya proteins were originally identified as essential transcriptional co-activators of the Six family of homeoproteins. Subsequently, the highly conserved C-terminal domains of the Eya proteins were discovered to act as a Mg²⁺-dependent Tyr phosphatases, making Eyas the first transcriptional activators to harbor intrinsic phosphatase activity. Only two direct targets of the Eya Tyr phosphatase have been identified: H2AX, whose dephosphorylation directs cells to the DNA repair instead of the apoptotic pathway upon DNA damage, and ERβ, whose dephosphorylation inhibits its anti-tumor transcriptional activity. The Eya Tyr phosphatase mediates breast cancer cell transformation, migration, invasion, as well as metastasis, through targets not yet identified. Intriguingly, the N-terminal domain of Eya contains a separate Ser/Thr phosphatase activity implicated in innate immunity and in regulating c-Myc stability. Thus, Eya proteins are highly complex, containing two separable phosphatase domains and a transcriptional activation domain, thereby influencing tumor progression through multiple mechanisms.

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.

SIX3, a tumor suppressor, inhibits astrocytoma tumorigenesis by transcriptional repression of AURKA/B

BACKGROUND

SIX homeobox 3 (SIX3) is a member of the sine oculis homeobox transcription factor family. It plays a vital role in the nervous system development. Our previous study showed that the SIX3 gene is hypermethylated, and its expression is decreased in astrocytoma, but the role of SIX3 remains unknown.

METHODS

Chromatin-immunoprecipitation (ChIP) and luciferase reporter assay were used to confirm the binding of SIX3 to the promoter regions of aurora kinase A (AURKA) and aurora kinase B (AURKB). Confocal imaging and co-immunoprecipitation (Co-IP) were used to detect the interaction between AURKA and AURKB. Flow cytometry was performed to assess the effect of SIX3 on cell cycle distribution. Colony formation, EdU incorporation, transwell, and intracranial xenograft assays were performed to demonstrate the effect of SIX3 on the malignant phenotype of astrocytoma cells.

RESULTS

SIX3 is identified as a novel negative transcriptional regulator of AURKA and AURKB, and it decreases the expression of AURKA and AURKB in a dose-dependent manner in astrocytoma cells. Importantly, interactions between AURKA and AURKB stabilize and protect AURKA/B from degradation, and overexpression of SIX3 does not affect these interactions; SIX3 also acts as a tumor suppressor, and it increases p53 activity and expression at the post-translational level by the negative regulation of AURKA or AURKB, reduces the events of numerical centrosomal aberrations and misaligned chromosomes, and significantly inhibits the proliferation, invasion, and tumorigenesis of astrocytoma in vitro and in vivo. Moreover, experiments using primary cultured astrocytoma cells indicate that astrocytoma patients with a low expression of SIX3 and mutant p53 are more sensitive to treatment with aurora kinase inhibitors.

CONCLUSION

SIX3 is a novel negative transcriptional regulator and acts as a tumor suppressor that directly represses the transcription of AURKA and AURKB in astrocytoma. For the first time, the functional interaction of AURKA and AURKB has been found, which aids in the protection of their stability, and partially explains their constant high expression and activity in cancers. SIX3 is a potential biomarker that could be used to predict the response of astrocytoma patients to aurora kinase inhibitors.

Identification of Genes Mediating Drosophila Follicle Cell Progenitor Differentiation by Screening for Modifiers of GAL4::UAS Variegation

The Drosophila melanogaster ovarian follicle cell lineage provides a powerful system for investigating how epigenetic changes contribute to differentiation. Downstream from an epithelial stem cell, follicle progenitors undergo nine mitotic cell cycles before transitioning to the endocycle and initiating differentiation. During their proliferative phase, follicle progenitors experience Lsd1-dependent changes in epigenetic stability that can be monitored using GAL4::UAS variegation. Eventually, follicle progenitors acquire competence to respond to Delta, a Notch ligand present in the environment, which signals them to cease division and initiate differentiation. The time required to acquire competence determines the duration of mitotic cycling and hence the final number of follicle cells. We carried out a screen for dominant modifiers of variegation spanning nearly 70% of Drosophila euchromatin to identify new genes influencing follicle progenitor epigenetic maturation. The eight genes found include chromatin modifiers, but also cell cycle regulators and transcription factors. Five of the modifier genes accelerate the acquisition of progenitor competence and reduce follicle cell number, however, the other three genes affect follicle cell number in an unexpected manner.

The expression profile and clinic significance of the SIX family in non-small cell lung cancer

BACKGROUND

The SIX family homeobox genes have been demonstrated to be involved in the tumor initiation and progression, but their clinicopathological features and prognostic values in non-small cell lung cancer (NSCLC) have not been well defined. We analyzed relevant datasets and performed a systemic review and a meta-analysis to assess the profile of SIX family members in NSCLC and evaluate their importance as biomarkers for diagnosis and prediction of NSCLC.

METHODS

This meta-analysis included 17 studies with 2358 patients. Hazard ratio (HR) and 95 % confidence interval (CI) were calculated to represent the prognosis of NSCLC with expression of the SIX family genes. Heterogeneity of the ORs and HRs was assessed and quantified using the Cochrane Q and I 2 test. Begg's rank correlation method and Egger's weighted regression method were used to screen for potential publication bias. Bar graphs of representative datasets were plotted to show the correlation between the SIX expression and clinicopathological features of NSCLC. Kaplan-Meier survival curves were used to validate our prognostic analysis by pooled HR.

RESULTS

The systematic meta-analysis unveiled that the higher expressions of SIX1-5 were associated with the greater possibility of the tumorigenesis. SIX4 and SIX6 were linked to the lymph node metastasis (LNM). SIX2, SIX3, and SIX4 were correlated with higher TNM stages. Furthermore, the elevated expressions of SIX2, SIX4, and SIX6 predicted poor overall survival (OS) in NSCLC (SIX2: HR = 1.14, 95 % CI, 1.00-1.31; SIX4: HR = 1.39, 95 % CI, 1.16-1.66; SIX6: HR = 1.18, 95 % CI, 1.00-1.38) and poor relapse-free survival (RFS) in lung adenocarcinoma (ADC) (SIX2: HR = 1.42, 95 % CI, 1.14-1.77; SIX4: HR = 1.52, 95 % CI, 1.09-2.11; SIX6: HR = 1.25, 95 % CI, 1.01-1.56).

CONCLUSIONS

Our report demonstrated that the SIX family members play distinct roles in the tumorigenesis of NSCLC and can be potential biomarkers in predicting prognosis of NSCLC patients.