LIM homeobox transcription factors, a novel subfamily which plays an important role in cancer (Review)

Epigenetic aberrations of gene expression in a rat model of hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is mostly triggered by environmental and life-style factors and may involve epigenetic aberrations. However, a comprehensive documentation of the link between the dysregulated epigenome, transcriptome, and liver carcinogenesis is lacking. In the present study, Fischer-344 rats were fed a choline-deficient (CDAA, cancer group) or choline-sufficient (CSAA, healthy group) L-amino acid-defined diet. At the end of 52 weeks, transcriptomic alterations in livers of rats with HCC tumours and healthy livers were investigated by RNA sequencing. DNA methylation and gene expression were assessed by pyrosequencing and quantitative reverse-transcription PCR (qRT-PCR), respectively. We discovered 1,848 genes that were significantly differentially expressed in livers of rats with HCC tumours (CDAA) as compared with healthy livers (CSAA). Upregulated genes in the CDAA group were associated with cancer-related functions, whereas macronutrient metabolic processes were enriched by downregulated genes. Changes of highest magnitude were detected in numerous upregulated genes that govern key oncogenic signalling pathways, including Notch, Wnt, Hedgehog, and extracellular matrix degradation. We further detected perturbations in DNA methylating and demethylating enzymes, which was reflected in decreased global DNA methylation and increased global DNA hydroxymethylation. Four selected upregulated candidates, Mmp12, Jag1, Wnt4, and Smo, demonstrated promoter hypomethylation with the most profound decrease in Mmp12. MMP12 was also strongly overexpressed and hypomethylated in human HCC HepG2 cells as compared with primary hepatocytes, which coincided with binding of Ten-eleven translocation 1 (TET1). Our findings provide comprehensive evidence for gene expression changes and dysregulated epigenome in HCC pathogenesis, potentially revealing novel targets for HCC prevention/treatment.

Hsa_circ_0008726 regulates the proliferation, migration, and invasion of trophoblast cells in preeclampsia through modulating the miR-1290-LHX6 signaling pathway

Background

Preeclampsia (PE) is a serious complication of pregnancy, with a global incidence of about 2%–8%. It is one of the important causes of morbidity and mortality among the pregnant women and perinatal infants. Circular RNA (circRNA) has been confirmed to play an important regulatory role in PE. This study aimed to evaluate the role of hsa_circ_0008726 in the occurrence and development of PE.

Methods

The expression of hsa_circ_0008726 in PE placental tissue and blood was detected by qRT‐PCR. CCK‐8, wound closure, and Transwell assay were used to measure cell proliferation, migration, and invasion. Bioinformatics prediction, Western blotting, and dual‐luciferase reporter gene detection were used to explore the mechanism of hsa_circ_0008726 in HTR8/SVneo cells.

Results

The expression level of circ_0008726 in the placental tissue and blood samples of PE patients was significantly higher than that of normal controls. The overexpression of circ_0008726 can significantly inhibit the proliferation, migration, and invasion ability of HTR‐8/SVneo cells. While the silence of circ_0008726 showed an opposite effect. Furthermore, hsa_circ_0008726 can modulate the expression of LHX6 by adsorbing miR‐1290.

Conclusion

Hsa_circ_000872 can regulate LHX6 by adsorbing miR‐1290 to inhibit PE progression, thus establishing hsa_circ_000872 as a potential target for predicting and treating PE.

ISL2 is a putative tumor suppressor whose epigenetic silencing reprograms the metabolism of pancreatic cancer

Pancreatic ductal adenocarcinoma (PDA) cells reprogram their transcriptional and metabolic programs to survive the nutrient-poor tumor microenvironment. Through in vivo CRISPR screening, we discovered islet-2 (ISL2) as a candidate tumor suppressor that modulates aggressive PDA growth. Notably, ISL2, a nuclear and chromatin-associated transcription factor, is epigenetically silenced in PDA tumors and high promoter DNA methylation or its reduced expression correlates with poor patient survival. The exogenous ISL2 expression or CRISPR-mediated upregulation of the endogenous loci reduces cell proliferation. Mechanistically, ISL2 regulates the expression of metabolic genes, and its depletion increases oxidative phosphorylation (OXPHOS). As such, ISL2-depleted human PDA cells are sensitive to the inhibitors of mitochondrial complex I in vitro and in vivo. Spatial transcriptomic analysis shows heterogeneous intratumoral ISL2 expression, which correlates with the expression of critical metabolic genes. These findings nominate ISL2 as a putative tumor suppressor whose inactivation leads to increased mitochondrial metabolism that may be exploitable therapeutically.

MicroRNAs as the critical regulators of tyrosine kinase inhibitors resistance in lung tumor cells

Lung cancer is the second most common and the leading cause of cancer related deaths globally. Tyrosine Kinase Inhibitors (TKIs) are among the common therapeutic strategies in lung cancer patients, however the treatment process fails in a wide range of patients due to TKIs resistance. Given that the use of anti-cancer drugs can always have side effects on normal tissues, predicting the TKI responses can provide an efficient therapeutic strategy. Therefore, it is required to clarify the molecular mechanisms of TKIs resistance in lung cancer patients. MicroRNAs (miRNAs) are involved in regulation of various pathophysiological cellular processes. In the present review, we discussed the miRNAs that have been associated with TKIs responses in lung cancer. MiRNAs mainly exert their role on TKIs response through regulation of Tyrosine Kinase Receptors (TKRs) and down-stream signaling pathways. This review paves the way for introducing a panel of miRNAs for the prediction of TKIs responses in lung cancer patients.

Alternative LIM homeodomain splice variants are dynamically regulated at key developmental steps in vertebrates

BACKGROUND

Alternative splicing provides a broad strategy to amplify the genome. Yet how alternative splicing influences neurodevelopment or indeed which variants are translated at developmental choice points remains poorly explored. Here we focused on a gene important for neurodevelopment, the Lim homeodomain transcription factor, Lhx9. Lhx9 has two non-canonical splice variants, Lhx9a and Lhx9b which compared with the canonical variant Lhx9c have a truncated homeodomain and an alternative C-terminal sequence, suggesting that, if translated, these variants could differently impact on cellular function.

RESULTS

We created a unique antibody tool designed to selectively detect non-canonical Lhx9 variants (Lhx9ab) and used this to examine the protein expression dynamics in embryos. Lhx9ab variants were translated and dynamically expressed similarly between mouse and chicken at key developmental choice points in the spinal cord, limbs and urogenital ridge. Within the spinal cord, enrichment of Lhx9c versus Lhx9ab expression was observed during key migration and axonal projection choice points.

CONCLUSIONS

These data support the notion that the expression dynamics between canonical and non-canonical Lhx9 variants could play an important role in spinal neuron maturation. More broadly, determining the temporal dynamics of alternative protein variants is a key entry point to understand how splicing influences developmental processes. This article is protected by copyright. All rights reserved.

LIM Homeobox-2 Suppresses Hallmarks of Adult and Pediatric Liver Cancers by Inactivating MAPK/ERK and Wnt/Beta-Catenin Pathways

INTRODUCTION

Hepatocellular carcinoma and hepatoblastoma are two liver cancers characterized by gene deregulations, chromosomal rearrangements, and mutations in Wnt/beta-catenin (Wnt) pathway-related genes. LHX2, a transcriptional factor member of the LIM homeobox gene family, has important functions in embryogenesis and liver development. LHX2 is oncogenic in many solid tumors and leukemia, but its role in liver cancer is unknown.

METHODS

We analyzed the expression of LHX2 in hepatocellular carcinoma and hepatoblastoma samples using various transcriptomic datasets and biological samples. The role of LHX2 was studied using lentiviral transduction, in vitro cell-based assays (growth, migration, senescence, and apoptosis), molecular approaches (phosphokinase arrays and RNA-seq), bioinformatics, and two in vivo models in chicken and Xenopus embryos.

RESULTS

We found a strong connection between LHX2 downregulation and Wnt activation in these two liver cancers. In hepatoblastoma, LHX2 downregulation correlated with multiple poor outcome parameters including higher patient age, intermediate- and high-risk tumors, and low patient survival. Forced expression of LHX2 reduced the proliferation, migration, and survival of liver cancer cells in vitro through the inactivation of MAPK/ERK and Wnt signals. In vivo, LHX2 impeded the development of tumors in chick embryos and repressed the Wnt pathway in Xenopus embryos. RNA-sequencing data and bioinformatic analyses confirmed the deregulation of many biological functions and molecular processes associated with cell migration, cell survival, and liver carcinogenesis in LHX2-expressing hepatoma cells. At a mechanistic level, LHX2 mediated the disassembling of beta-catenin/T-cell factor 4 complex and induced expression of multiple inhibitors of Wnt (e.g., TLE/Groucho) and MAPK/ERK (e.g., DUSPs) pathways.

CONCLUSION

Collectively, our findings demonstrate a tumor suppressive function of LHX2 in adult and pediatric liver cancers.

Identification of key genes involved in the recurrence of glioblastoma multiforme using weighted gene co-expression network analysis and differential expression analysis

Glioblastoma multiforme (GBM) is the most fatal malignancy, and despite extensive treatment, tumors inevitably recur. This study aimed to identify recurrence-associated molecules in GBM. The gene expression profile GSE139533, containing 70 primary and 47 recurrent GBM tissues and their corresponding clinical traits, was downloaded from the Gene Expression Omnibus (GEO) database and used for weighted gene co-expression network analysis (WGCNA) and differentially expressed gene (DEG) analysis. After identifying the hub genes which differentially expressed in recurrent GBM tissues and in the gene modules correlated with recurrence, data from the Chinese Glioma Genome Atlas (CCGA) and The Cancer Genome Atlas (TCGA) databases were analyzed with GSE43378 to determine the relationship between hub genes and patient prognosis. The diagnostic value of the identified hub genes was verified using 52 GBM tissues. Three gene modules were correlated with recurrence and 2623 genes were clustered in these clinically significant modules. Among these, 13 genes - EHF, TRPM1, FXYD4, CDH15, LHX5, TP73, FBN3, TLX1, C1QL4, COL2A, SEC61G, NEUROD4 and GPR139 - were differentially expressed in recurrent GBM samples; low LHX5 and TLX1 expression predicted poor outcomes. LHX5 and TLX1 expression showed weak positive relationships with Karnofsky performance scale scores. Additionally, LHX5 and TLX1 expression was found to be decreased in our recurrent GBM samples compared with that in primary samples; these genes exhibited high diagnostic value in distinguishing recurrent samples from primary samples. Our findings indicate that LHX5 and TLX1 might be involved in GBM recurrence and act as potential biomarkers for this condition.

LIM Homeodomain (LIM-HD) Genes and Their Co-Regulators in Developing Reproductive System and Disorders of Sex Development

LIM homeodomain (LIM-HD) family genes are transcription factors that play crucial roles in a variety of functions during embryonic development. The activities of the LIM-HD proteins are regulated by the co-regulators LIM only (LMO) and LIM domain-binding (LDB). In the mouse genome, there are 13 LIM-HD genes (Lhx1-Lhx9, Isl1-2, Lmx1a-1b), 4 Lmo genes (Lmo1-4), and 2 Ldb genes (Ldb1-2). Amongst these, Lhx1 is required for the development of the müllerian duct epithelium and the timing of the primordial germ cell migration. Lhx8 is necessary for oocyte differentiation and Lhx9 for somatic cell proliferation in the genital ridges and control of testosterone production in the Leydig cells. Lmo4 is involved in Sertoli cell differentiation. Mutations in LHX1 are associated with müllerian agenesis or Mayer-Rokitansky-Kuster-Hauser (MRKH) syndrome. LHX9 gene variants are reported in cases with disorders of sex development (DSD). Mutations in LHX3 and LHX4 are reported in patients with combined pituitary hormone deficiency having absent or delayed puberty. A transcript map of the Lhx, Lmo, and Ldb genes reveal that multiple LIM-HD genes and their co-regulators are expressed in a sexually dimorphic pattern in the developing mouse gonads. Unraveling the roles of LIM-HD genes during development will aid in our understanding of the causes of DSD.

Phosphorylation of islet-1 serine 269 by CDK1 increases its transcriptional activity and promotes cell proliferation in gastric cancer

Background

Despite recent advances in diagnostic and therapeutic approaches for gastric cancer (GC), the survival of patients with advanced GC remains very low. Islet-1 (ISL1) is a LIM-homeodomain transcription factor, which is upregulated and promotes cell proliferation in GC. The exact mechanism by which ISL1 influences GC development is unclear.

Methods

Co-immunoprecipitation (co-IP) and glutathione S-transferase (GST)-pulldown assays were employed to evaluate the interaction of ISL1 with CDK1. Western blot and immunohistochemistry analyses were performed to evaluate the ability of CDK1 to phosphorylate ISL1 at Ser 269 in GC cell and tissue specimens. Chromatin immunoprecipitation (ChIP), ChIP re-IP, luciferase reporter, and CCK-8 assays were combined with flow cytometry cell cycle analysis to detect the transactivation potency of ISL1-S269-p and its ability to promote cell proliferation. The self-stability and interaction with CDK1 of ISL1-S269-p were also determined.

Results

ISL1 is phosphorylated by CDK1 at serine 269 (S269) in vivo. Phosphorylation of ISL1 by CDK1 on serine 269 strengthened its binding on the cyclin B1 and cyclin B2 promoters and increased its transcriptional activity in GC. Furthermore, CDK1-dependent phosphorylation of ISL1 correlated positively with ISL1 protein self-stability in NIH3T3 cells.

Conclusions

ISL1-S269-p increased ISL1 transcriptional activity and self-stability while binding to the cyclinB1 and cyclinB2 promoters promotes cell proliferation. ISL1-S269-p is therefore crucial for tumorigenesis and potentially a direct therapeutic target for GC.

Supplementary Information

The online version contains supplementary material available at 10.1186/s10020-021-00302-6.

LHX6 Affects Erlotinib Resistance and Migration of EGFR-Mutant Non-Small-Cell Lung Cancer HCC827 Cells Through Suppressing Wnt/β-Catenin Signaling

Background

miR-214 has been reported to contribute to erlotinib resistance in non-small-cell lung cancer (NSCLC) through targeting LHX6; however, the molecular mechanisms underlying the involvement of LHX6 in mediating the resistance to EGFR-TKIs in erlotinib-resistant NSCLC HCC827 (HCC827/ER) cells remain unknown. This study aimed to investigate the mechanisms responsible for the contribution of LHX6 to EGFR-TKIs resistance in HCC827/ER cells.

Materials and Methods

HCC827/ER cells were generated by erlotinib treatment at a dose-escalation scheme. LHX6 knockout or overexpression was modeled in HCC827 and HCC827/ER cells, and then erlotinib IC₅₀ values were measured. The cell migration ability was evaluated using a transwell migration assay, and the TCF/LEF luciferase activity was assessed with a TCF/LEF reporter luciferase assay. LHX6, β-catenin and Cyclin D1 expression was quantified using qPCR and Western blotting assays. In addition, the LHX6 expression was detected in lung cancer and peri-cancer specimens using immunohistochemical staining, and the associations of LHX expression with the clinicopathological characteristics of lung cancer were evaluated.

Results

Lower LHX6 expression was detected in HCC827/ER cells than in HCC827 cells (P < 0.0001), while higher β-catenin expression was seen in HCC827/ER cells than in HCC827 cells (P < 0.001). LHX6 knockout increased erlotinib resistance and cell migration ability in HCC827 cells, and LHX6 overexpression inhibited erlotinib resistance and cell migration ability in HCC827/ER cells. In addition, LHX6 mediated erlotinib resistance and cell migration ability in HCC827/ER cells via the Wnt/β-catenin pathway. Immunohistochemical staining showed lower LHX6 expression in lung cancer specimens relative to peri-cancer specimens, and there were no associations of LHX6 expression with pathologic stage, gender, age or tumor size in lung cancer patients (P > 0.05).

Conclusion

LHX6 down-regulation may induce EGFR-TKIs resistance and increase the migration ability of HCC827/ER cells via activation of the Wnt/β-catenin pathway.

ISL2 modulates angiogenesis through transcriptional regulation of ANGPT2 to promote cell proliferation and malignant transformation in oligodendroglioma

Oligodendroglioma is an important type of lower-grade glioma (LGG), which is a slowly progressing brain tumor. Many LGGs eventually transform into a more aggressive or malignant type. Enhanced angiogenesis is a characteristic of malignantly transformed oligodendroglioma (m-oligodendroglioma). However, the pathogenesis and signaling pathways associated with angiogenesis and proliferation in m-oligodendroglioma are not well understood. In this study, we identified that Insulin Gene Enhancer Protein (ISL2) and its angiogenic capacity were inversely related to survival according to LGG patient data from an online database, and this was further confirmed with pathological LGG patient samples, including malignantly transformed samples, by detecting the expression of ISL2, the angiogenic markers vascular endothelial growth factor (VEGFA) and CD31 and the proliferation marker Ki-67. We then established novel oligodendroglioma patient tumor-derived orthotopic xenograft mouse models and cell lines to verify the role of ISL2 in regulating angiogenesis to promote oligodendroglioma growth and malignant transformation. Furthermore, ISL2 regulated ANGPT2 transcription by binding to the ANGPT2 promoter. Then, ANGPT2, a downstream gene, activated angiogenesis through VEGFA to promote oligodendroglioma malignant transformation. Finally, combining AAV-ISL2-shRNA with temozolomide suppressed oligodendroglioma progression more effectively than either monotherapy in vivo and in vitro. Thus, hypoxia-induced ISL2 regulated ANGPT2, which subsequently induced angiogenesis to promote oligodendroglioma growth and malignant transformation. Malignancy was accompanied by worsened hypoxia inside the tumor mass, creating a positive feedback loop. In conclusion, this study suggests that ISL2 is a biomarker for oligodendroglioma progression and that anti-ISL2 therapy may offer a potential clinical strategy for treating m-oligodendroglioma.

Epigenetic Silencing of LMX1A Contributes to Cancer Progression in Lung Cancer Cells

Epigenetic modification is considered a major mechanism of the inactivation of tumor suppressor genes that finally contributes to carcinogenesis. LIM homeobox transcription factor 1α (LMX1A) is one of the LIM-homeobox-containing genes that is a critical regulator of growth and differentiation. Recently, LMX1A was shown to be hypermethylated and functioned as a tumor suppressor in cervical cancer, ovarian cancer, and gastric cancer. However, its role in lung cancer has not yet been clarified. In this study, we used public databases, methylation-specific PCR (MSP), reverse transcription PCR (RT-PCR), and bisulfite genomic sequencing to show that LMX1A was downregulated or silenced due to promoter hypermethylation in lung cancers. Treatment of lung cancer cells with the demethylating agent 5-aza-2'-deoxycytidine restored LMX1A expression. In the lung cancer cell lines H23 and H1299, overexpression of LMX1A did not affect cell proliferation but suppressed colony formation and invasion. These suppressive effects were reversed after inhibition of LMX1A expression in an inducible expression system in H23 cells. The quantitative RT-PCR (qRT-PCR) data showed that LMX1A could modulate epithelial mesenchymal transition (EMT) through E-cadherin (CDH1) and fibronectin (FN1). NanoString gene expression analysis revealed that all aberrantly expressed genes were associated with processes related to cancer progression, including angiogenesis, extracellular matrix (ECM) remodeling, EMT, cancer metastasis, and hypoxia-related gene expression. Taken together, these data demonstrated that LMX1A is inactivated through promoter hypermethylation and functions as a tumor suppressor. Furthermore, LMX1A inhibits non-small cell lung cancer (NSCLC) cell invasion partly through modulation of EMT, angiogenesis, and ECM remodeling.

The Role of ISL1 and LHX5 LIM Homeobox Genes in Bladder Tumourigenesis

Introduction

Lin-11, Isl-1 and Mec-3 domains (LIM) homeobox genes are among the most important sub-families of homeobox genes. These genes are thought to play an important role in cancer. In this study, the protein expression of these genes was examined in urothelial carcinoma of the bladder. The expression pattern of Islet-1 (ISL1) and LIM homeobox 5 (LHX5) across different cancer stages and grades, as well as the association between the protein expression of these genes and patient demographics and clinicopathological features, were examined.

Methods

A total of 100 formalin-fixed paraffin-embedded urothelial carcinoma tissues were selected from the Department of Pathology, Hospital Kuala Lumpur and the protein expression of ISL1 and LHX5 was determined using immunohistochemistry.

Results

Positive expression of ISL1 and LHX5 was detected in 94% and 98% of the samples, respectively. There were no distinct LHX5 expression patterns associated with different cancer stages, but the proportion of high-expressing tumours was higher in high-grade tumours. In addition, there was a significant association between the expression of LHX5 and tumour grade. The proportion of tumours expressing high levels of ISL1 was found to be highest in later stage tumours.

Conclusion

The high percentage of tumours expressing both these genes suggests that ISL1 and LHX5 play an important role in bladder tumourigenesis across multiple stages.

Inherited Eye Diseases with Retinal Manifestations through the Eyes of Homeobox Genes

Retinal development is under the coordinated control of overlapping networks of signaling pathways and transcription factors. The paper was conceived as a review of the data and ideas that have been formed to date on homeobox genes mutations that lead to the disruption of eye organogenesis and result in inherited eye/retinal diseases. Many of these diseases are part of the same clinical spectrum and have high genetic heterogeneity with already identified associated genes. We summarize the known key regulators of eye development, with a focus on the homeobox genes associated with monogenic eye diseases showing retinal manifestations. Recent advances in the field of genetics and high-throughput next-generation sequencing technologies, including single-cell transcriptome analysis have allowed for deepening of knowledge of the genetic basis of inherited retinal diseases (IRDs), as well as improve their diagnostics. We highlight some promising avenues of research involving molecular-genetic and cell-technology approaches that can be effective for IRDs therapy. The most promising neuroprotective strategies are aimed at mobilizing the endogenous cellular reserve of the retina.

ISL1 is upregulated in breast cancer and promotes cell proliferation, invasion, and angiogenesis

ISL1 plays a key role in several cancers, including pheochromocytoma, gastrointestinal, pancreatic, and lung tumors and bile duct carcinoma. In order to elucidate the role of ISL1 in breast cancer, we performed quantitative real-time polymerase chain reaction and Western blotting analysis, and we found that ISL1 was upregulated in breast cancer cells and tissues. Moreover, high expression of ISL1 was correlated with tumor size, metastasis, and poor prognosis. Colony formation analysis and CCK-8 analysis revealed that ISL1 facilitated breast cancer cell proliferation. In addition, wound healing analysis and transwell invasion analysis demonstrated that ISL1 played a role in cell migration and invasion. Interestingly, the expression of ISL1 was also associated with the expression of vascular endothelial growth factor (VEGF) in breast cancer, and ISL1 promoted angiogenesis in breast cancer. In conclusion, reducing the expression of ISL1 suppresses proliferation, migration, invasion, and angiogenesis in breast cancer, suggesting that ISL1 might serve as a novel molecular therapy target in breast cancer.

ISL1, a novel regulator of CCNB1, CCNB2 and c-MYC genes, promotes gastric cancer cell proliferation and tumor growth

Islet-1 (ISL1) belongs to the LIM homeodomain transcription factor family, which is specifically expressed in certain tissue types only. Previously, we reported that ISL1 is aberrantly overexpressed in gastric cancer (GC). However, its role in GC is not clear. Here, we report that ISL1 is aberrantly upregulated not only in human gastric carcinoma tissues but also in some GC cell lines. Upregulated ISL1 expression enhanced xenografted gastric carcinoma development, while ISL1 knockdown inhibited GC growth in nude mice. ISL1 overexpression promoted GC cell proliferation, colony formation, and cell growth in soft agar, and facilitated cell cycle transition in GC cells, demonstrated an increase in the proportion of cells in the G₂/M and S phases and a decrease in the proportion of cells in the G₁ phase. Furthermore, we provide evidence that ISL1 is a novel regulator of the cyclin B1 (CCNB1), cyclin B2 (CCNB2) and c-myc (c-MYC) genes. ISL1 activated the expression of these genes in GC cells by binding to the conserved binding sites on their promoters or enhancers. The expression levels of the genes were decreased in response to ISL1 knockdown. Therefore, ISL1 may serve as a potential therapeutic target in GC.

Down-regulation of miR-214 reverses erlotinib resistance in non-small-cell lung cancer through up-regulating LHX6 expression

Epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs) are standard treatments for advanced non-small-cell lung cancer (NSCLC) patients. However, acquired resistance to EGFR-TKIs is widely detected across the world, and the exact mechanisms have not been fully demonstrated until now. This study aimed to examine the role of miR-214 in the acquired resistance to erlotinib in NSCLC, and elucidate the underlying mechanisms. qRT-PCR assay detected higher miR-214 expression in the plasma of NSCLC patients with acquired EGFR-TKI resistance than prior to EGFR-TKI therapy, and in the generated erlotinib-resistant HCC827 (HCC827/ER) cells than in HCC827 cells. Bioinformatics analysis and dual-luciferase reporter assay indentified LHX6 as a direct target gene of miR-214, and LHX6 expression was detected to be down-regulated in erlotinib-resistant HCC827 cells. Transwell invasion assay revealed that overexpressing LHX6 reversed the increase in the invasive ability of HCC827 cells induced by miR-214 overexpression, and the CRISPR-Cas9 system-mediated LHX6 knockdown reversed the reduction in the invasion of erlotinib-resistant HCC827 cells caused by miR-214 down-regulation. The results of the present study demonstrate that down-regulation of miR-214 may reverse acquired resistance to erlotinib in NSCLC through mediating its direct target gene LHX6 expression.

Hepatocyte nuclear factor 1 beta induces transformation and epithelial-to-mesenchymal transition

Gene amplification can be a cause of cancer, and driver oncogenes have been often identified in amplified regions. However, comprehensive analysis of other genes coamplified with an oncogene is rarely performed. We focused on the 17q12-21 amplicon, which contains ERBB2. We established a screening system for oncogenic activity with the NMuMG epithelial cell line. We identified a homeobox gene, HNF1B, as a novel cooperative transforming gene. HNF1B induced cancerous phenotypes, which were enhanced by the coexpression of ERBB2, and induced epithelial-to-mesenchymal transition and invasive phenotypes. These results suggest that HNF1B is a novel oncogene that can work cooperatively with ERBB2.

Oncofetal Epigenetic Bivalency in Breast Cancer Cells: H3K4 and H3K27 Tri-Methylation as a Biomarker for Phenotypic Plasticity

Alterations in the epigenetic landscape are fundamental drivers of aberrant gene expression that contribute to cancer progression and pathology. Understanding specific modes of epigenetic regulation can be used to identify novel biomarkers or targets for therapeutic intervention to clinically treat solid tumors and leukemias. The bivalent marking of gene promoters by H3K4me3 and H3K27me3 is a primary mechanism to poise genes for expression in pluripotent embryonic stem cells (ESC). In this study we interrogated three well-established mammary cell lines to model epigenetic programming observed among breast cancer subtypes. Evidence is provided for a distinct bivalent signature, activating and repressive histone marks co-residing at the same gene promoter, in the MCF7 (ESR/PGR+) luminal breast cancer cell line. We identified a subset of genes, enriched for developmental pathways that regulate cellular phenotype and signaling, and partially recapitulate the bivalent character observed in ESC. We validated the biological relevance of this "oncofetal epigenetic" signature using data from ESR/PGR+ tumor samples from breast cancer patients. This signature of oncofetal epigenetic control is an informative biomarker and may provide novel therapeutic targets, selective for both recurring and treatment-resistant cancers. J. Cell. Physiol. 231: 2474-2481, 2016. © 2016 Wiley Periodicals, Inc.

Cell fate determination, neuronal maintenance and disease state: The emerging role of transcription factors Lmx1a and Lmx1b

LIM-homeodomain (LIM-HD) proteins are evolutionary conserved developmental transcription factors. LIM-HD Lmx1a and Lmx1b orchestrate complex temporal and spatial gene expression of the dopaminergic pathway, and evidence shows they are also involved in adult neuronal homeostasis. In this review, the multiple roles played by Lmx1a and Lmx1b will be discussed. Controlled Lmx1a and Lmx1b expression and activities ensure the proper formation of critical signaling centers, including the embryonic ventral mesencephalon floor plate and sharp boundaries between lineage-specific cells. Lmx1a and Lmx1b expression persists in mature dopaminergic neurons of the substantia nigra pars compacta and the ventral tegmental area, and their role in the adult brain is beginning to be revealed. Notably, LMX1B expression was lower in brain tissue affected by Parkinson's disease. Actual and future applications of Lmx1a and Lmx1b transcription factors in stem cell production as well as in direct conversion of fibroblast into dopaminergic neurons are also discussed. A thorough understanding of the role of LMX1A and LMX1B in a number of disease states, including developmental diseases, cancer and neurodegenerative diseases, could lead to significant benefits for human healthcare.

Homeodomain proteins: an update

Here, we provide an update of our review on homeobox genes that we wrote together with Walter Gehring in 1994. Since then, comprehensive surveys of homeobox genes have become possible due to genome sequencing projects. Using the 103 Drosophila homeobox genes as example, we present an updated classification. In animals, there are 16 major classes, ANTP, PRD, PRD-LIKE, POU, HNF, CUT (with four subclasses: ONECUT, CUX, SATB, and CMP), LIM, ZF, CERS, PROS, SIX/SO, plus the TALE superclass with the classes IRO, MKX, TGIF, PBC, and MEIS. In plants, there are 11 major classes, i.e., HD-ZIP (with four subclasses: I to IV), WOX, NDX, PHD, PLINC, LD, DDT, SAWADEE, PINTOX, and the two TALE classes KNOX and BEL. Most of these classes encode additional domains apart from the homeodomain. Numerous insights have been obtained in the last two decades into how homeodomain proteins bind to DNA and increase their specificity by interacting with other proteins to regulate cell- and tissue-specific gene expression. Not only protein-DNA base pair contacts are important for proper target selection; recent experiments also reveal that the shape of the DNA plays a role in specificity. Using selected examples, we highlight different mechanisms of homeodomain protein-DNA interaction. The PRD class of homeobox genes was of special interest to Walter Gehring in the last two decades. The PRD class comprises six families in Bilateria, and tinkers with four different motifs, i.e., the PAIRED domain, the Groucho-interacting motif EH1 (aka Octapeptide or TN), the homeodomain, and the OAR motif. Homologs of the co-repressor protein Groucho are also present in plants (TOPLESS), where they have been shown to interact with small amphipathic motives (EAR), and in yeast (TUP1), where we find an EH1-like motif in MATα2.