Potential protective role of Grainyhead-like genes in the development of clear cell renal cell carcinoma

Vitamin D Receptor Regulates the Expression of the Grainyhead-Like 1 Gene

Vitamin D plays an important pleiotropic role in maintaining global homeostasis of the human body. Its functions go far beyond skeletal health, playing a crucial role in a plethora of cellular functions, as well as in extraskeletal health, ensuring the proper functioning of multiple human organs, including the skin. Genes from the Grainyhead-like (GRHL) family code for transcription factors necessary for the development and maintenance of various epithelia. Even though they are involved in many processes regulated by vitamin D, a direct link between vitamin D-mediated cellular pathways and GRHL genes has never been described. We employed various bioinformatic methods, quantitative real-time PCR, chromatin immunoprecipitation, reporter gene assays, and calcitriol treatments to investigate this issue. We report that the vitamin D receptor (VDR) binds to a regulatory region of the Grainyhead-like 1 (GRHL1) gene and regulates its expression. Ectopic expression of VDR and treatment with calcitriol alters the expression of the GRHL1 gene. The evidence presented here indicates a role of VDR in the regulation of expression of GRHL1 and correspondingly a role of GRHL1 in mediating the actions of vitamin D.

GRHL2 Enhances Phosphorylated Estrogen Receptor (ER) Chromatin Binding and Regulates ER-Mediated Transcriptional Activation and Repression

Phosphorylation of estrogen receptor α (ER) at serine 118 (pS118-ER) is induced by estrogen and is the most abundant posttranslational mark associated with a transcriptionally active receptor. Cistromic analysis of pS118-ER from our group revealed enrichment of the GRHL2 motif near pS118-ER binding sites. In this study, we used cistromic and transcriptomic analyses to interrogate the relationship between GRHL2 and pS118-ER. We found that GRHL2 is bound to chromatin at pS118-ER/GRHL2 co-occupancy sites prior to ligand treatment, and GRHL2 binding is required for maximal pS118-ER recruitment. pS118-ER/GRHL2 co-occupancy sites were enriched at active enhancers marked by H3K27ac and H3K4me1, along with FOXA1 and p300, compared to sites where each factor binds independently. Transcriptomic analysis yielded four subsets of ER/GRHL2-coregulated genes revealing that GRHL2 can both enhance and antagonize E2-mediated ER transcriptional activity. Gene ontology analysis indicated that coregulated genes are involved in cell migration. Accordingly, knockdown of GRHL2, combined with estrogen treatment, resulted in increased cell migration but no change in proliferation. These results support a model in which GRHL2 binds to selected enhancers and facilitates pS118-ER recruitment to chromatin, which then results in differential activation and repression of genes that control estrogen-regulated ER-positive breast cancer cell migration.

Grainyhead-like (Grhl) Target Genes in Development and Cancer

Grainyhead-like (GRHL) factors are essential, highly conserved transcription factors (TFs) that regulate processes common to both natural cellular behaviours during embryogenesis, and de-regulation of growth and survival pathways in cancer. Serving to drive the transcription, and therefore activation of multiple co-ordinating pathways, the three GRHL family members (GRHL1-3) are a critical conduit for modulating the molecular landscape that guides cellular decision-making processes during proliferation, epithelial-mesenchymal transition (EMT) and migration. Animal models and in vitro approaches harbouring GRHL loss or gain-of-function are key research tools to understanding gene function, which gives confidence that resultant phenotypes and cellular behaviours may be translatable to humans. Critically, identifying and characterising the target genes to which these factors bind is also essential, as they allow us to discover and understand novel genetic pathways that could ultimately be used as targets for disease diagnosis, drug discovery and therapeutic strategies. GRHL1-3 and their transcriptional targets have been shown to drive comparable cellular processes in Drosophila, C. elegans, zebrafish and mice, and have recently also been implicated in the aetiology and/or progression of a number of human congenital disorders and cancers of epithelial origin. In this review, we will summarise the state of knowledge pertaining to the role of the GRHL family target genes in both development and cancer, primarily through understanding the genetic pathways transcriptionally regulated by these factors across disparate disease contexts.

Transcription factors Krüppel-like factor 4 and paired box 5 regulate the expression of the Grainyhead-like genes

Genes from the Grainyhead-like (GRHL) family code for transcription factors necessary for the development and maintenance of various epithelia. These genes are also very important in the development of many types of cancer. However, little is known about the regulation of expression of GRHL genes. Previously, there were no systematic analyses of the promoters of GRHL genes or transcription factors that bind to these promoters. Here we report that the Krüppel-like factor 4 (KLF4) and the paired box 5 factor (PAX5) bind to the regulatory regions of the GRHL genes and regulate their expression. Ectopic expression of KLF4 or PAX5 alters the expression of GRHL genes. In KLF4-overexpressing HEK293 cells, the expression of GRHL1 and GRHL3 genes was upregulated by 32% and 60%, respectively, whereas the mRNA level of GRHL2 gene was lowered by 28% when compared to the respective controls. The levels of GRHL1 and GRHL3 expression were decreased by 30% or 33% in PAX5-overexpressing HEK293 cells. The presence of minor frequency allele of single nucleotide polymorphism rs115898376 in the promoter of the GRHL1 gene affected the binding of KLF4 to this site. The evidence presented here suggests an important role of KLF4 and PAX5 in the regulation of expression of GRHL1-3 genes.

Regulation of S100A10 Gene Expression

S100A10, a member of the S100 family of Ca²⁺-binding proteins, is a widely distributed protein involved in many cellular and extracellular processes. The best recognized role of S100A10 is the regulation, via interaction with annexin A2, of plasminogen conversion to plasmin. Plasmin, together with other proteases, induces degradation of the extracellular matrix (ECM), which is an important step in tumor progression. Additionally, S100A10 interacts with 5-hydroxytryptamine 1B (5-HT1B) receptor, which influences neurotransmitter binding and, through that, depressive symptoms. Taking this into account, it is evident that S100A10 expression in the cell should be under strict control. In this work, we summarize available literature data concerning the physiological stimuli and transcription factors that influence S100A10 expression. We also present our original results showing for the first time regulation of S100A10 expression by grainyhead-like 2 transcription factor (GRHL2). By applying in silico analysis, we have found two highly conserved GRHL2 binding sites in the 1st intron of the gene encoding S100A10 protein. Using chromatin immunoprecipitation (ChIP) and luciferase assays, we have shown that GRHL2 directly binds to these sites and that this DNA region can affect transcription of S100A10.

Identification of TYROBP and FCER1G as Key Genes with Prognostic Value in Clear Cell Renal Cell Carcinoma by Bioinformatics Analysis

The involvement of aberrantly expressed genes in the pathogenesis and progression of various human malignancies has been widely reported, including clear cell renal cell carcinoma (ccRCC). This study aimed to identify potential crucial genes in ccRCC and further investigate the role of these genes in ccRCC prognosis. Three gene expression profiles (GSE3, GSE6344 and GSE53000) were downloaded from GEO database. GEO2R was performed to identify the differentially expressed genes (DEGs) between ccRCC and normal samples. GO analysis and KEGG pathway enrichment analysis were applied for the function analysis. The DEGs were mapped into the PPI network, then the hub genes were identified and verified using the ONCOMINE database. Kaplan-Meier plotter was used to evaluate of the prognostic value of the identified hub genes. A total of 113 DEGs were identified from the three gene expression profiles, including 64 up-regulated genes and 69 down-regulated genes. DEGs were observed to be enriched in biological processes related to the progress and pathogenesis of human cancers. According to PPI network, 5 hub genes were collected, including TYROBP, C1QB, ITGB2, CD53 and FCER1G. Among them, CD53 was newly identified, and Kaplan-Meier survival curves suggested that high expression of CD53 was significantly associated with poor survival in ccRCC patients (log-rank P < 0.01). The present results may provide new insight into the understanding of molecular mechanisms and the clinical prognosis of ccRCC.

Epithelial-Mesenchymal Transition: Role in Cancer Progression and the Perspectives of Antitumor Treatment

About 90% of all malignant tumors are of epithelial nature. The epithelial tissue is characterized by a close interconnection between cells through cell-cell interactions, as well as a tight connection with the basement membrane, which is responsible for cell polarity. These interactions strictly determine the location of epithelial cells within the body and are seemingly in conflict with the metastatic potential that many cancers possess (the main criteria for highly malignant tumors). Tumor dissemination into vital organs is one of the primary causes of death in patients with cancer. Tumor dissemination is based on the so-called epithelial-mesenchymal transition (EMT), a process when epithelial cells are transformed into mesenchymal cells possessing high mobility and migration potential. More and more studies elucidating the role of the EMT in metastasis and other aspects of tumor progression are published each year, thus forming a promising field of cancer research. In this review, we examine the most recent data on the intracellular and extracellular molecular mechanisms that activate EMT and the role they play in various aspects of tumor progression, such as metastasis, apoptotic resistance, and immune evasion, aspects that have usually been attributed exclusively to cancer stem cells (CSCs). In conclusion, we provide a detailed review of the approved and promising drugs for cancer therapy that target the components of the EMT signaling pathways.

Grainyhead-like transcription factors in cancer - Focus on recent developments

The role of grainyhead-like transcription factors in cancer has been widely investigated by the scientific community. However, some of its aspects do not seem to be adequately appreciated, and these are the topic of our article. In addition to their well-documented role as tumor suppressors, in many cases the grainyhead-like proteins perform tumor-promoting functions, which make them potential drug targets. However, it is difficult to directly target transcription factors, which is why we recommend an alternative approach. The transcriptional transactivation activity of grainyhead-like transcription factors is regulated by phosphorylation, and protein kinases are much more feasible drug targets. Studying the phosphorylation of grainyhead-like proteins may thus allow to identify protein kinases regulating the activity of these factors, and design inhibitors of these kinases to indirectly regulate the activity of grainyhead-like transcription factors. There are many somatic mutations in the GRHL genes that occur during cancer development. These mutations are widely distributed across the GRHL loci, and these mutations are very rare. For this reason, they are unlikely to become targets of future therapies, nevertheless some of them may be driver mutations and studying them may provide important novel information about the regulation of functioning of the GRHL genes and proteins. Analogous information may be obtained by studying single nucleotide polymorphisms in GRHL genes that are associated with disease risk. Such polymorphisms may also prove useful in identifying individuals with an increased risk of a particular disease.

Impact statement

In the present article, we focus on relatively little appreciated aspects of involvement of the grainyhead-like (GRHL) transcription factors in cancer. These aspects are nevertheless very important for the functioning of GRHL proteins, as well as for cancer development. Some of the GRHL factors perform tumor-promoting functions in certain types of cancer, which makes them potential drug targets. Much information is available about somatic cancer mutations in the GRHL genes, yet there are very few analyses of these mutations in the scientific literature. The activity of GRHL transcription factors is controlled by phosphorylation, and we suggest that regulating their phosphorylation with specific protein kinases provides an alternative approach to modify the activity of GRHL proteins. Some single nucleotide polymorphisms (SNPs) in the GRHL genes are associated with disease risk. Studying such SNPs may yield new information about the functioning of GRHL genes and proteins, and may also allow to identify people with an increased risk of a particular disease.

Grainyhead-like Protein 2: The Emerging Role in Hormone-Dependent Cancers and Epigenetics

In mammals, the grainyhead-like transcription factor (GRHL) family is composed of three nuclear proteins that are responsible for driving epithelial cell fate: GRHL1, GRHL2, and GRHL3. GRHL2 is important in maintaining proper tubulogenesis during development and in suppressing the epithelial-to-mesenchymal transition. Within the last decade, evidence indicates both tumor-suppressive and oncogenic roles for GRHL2 in various types of cancers. Recent studies suggest that GRHL2 may be especially important in hormone-dependent cancers, as correlative relationships exist between GRHL2 and various steroid receptors, such as the androgen and estrogen receptors. Acting as a pioneer factor and coactivator, GRHL2 may directly affect steroid receptor transcriptional activity. This review will highlight recent discoveries of GRHL2 activity in cancer and in maintaining the epithelial state, while also exploring recent literature on the role of GRHL2 in hormone-dependent cancers and epigenetics.