RUNX3 protein is overexpressed in human basal cell carcinomas

Aberrant Upregulation of RUNX3 Activates Developmental Genes to Drive Metastasis in Gastric Cancer

Gastric cancer metastasis is a major cause of mortality worldwide. Inhibition of RUNX3 in gastric cancer cell lines reduced migration, invasion, and anchorage-independent growth in vitro. Following splenic inoculation, CRISPR-mediated RUNX3-knockout HGC-27 cells show suppression of xenograft growth and liver metastasis. We interrogated the potential of RUNX3 as a metastasis driver in gastric cancer by profiling its target genes. Transcriptomic analysis revealed strong involvement of RUNX3 in the regulation of multiple developmental pathways, consistent with the notion that Runt domain transcription factor (RUNX) family genes are master regulators of development. RUNX3 promoted "cell migration" and "extracellular matrix" programs, which are necessary for metastasis. Of note, we found pro-metastatic genes WNT5A, CD44, and VIM among the top differentially expressed genes in RUNX3 knockout versus control cells. Chromatin immunoprecipitation sequencing and HiChIP analyses revealed that RUNX3 bound to the enhancers and promoters of these genes, suggesting that they are under direct transcriptional control by RUNX3. We show that RUNX3 promoted metastasis in part through its upregulation of WNT5A to promote migration, invasion, and anchorage-independent growth in various malignancies. Our study therefore reveals the RUNX3-WNT5A axis as a key targetable mechanism for gastric cancer metastasis.

SIGNIFICANCE

Subversion of RUNX3 developmental gene targets to metastasis program indicates the oncogenic nature of inappropriate RUNX3 regulation in gastric cancer.

p53 Deficiency-Dependent Oncogenicity of Runx3

The RUNX transcription factors are frequently dysregulated in human cancers, suggesting their potential as attractive targets for drug treatment. However, all three transcription factors have been described as both tumor suppressors and oncogenes, indicating the need to determine their molecular mechanisms of action. Although RUNX3 has long been considered a tumor suppressor in human cancers, several recent studies have shown that RUNX3 is upregulated during the development or progression of various malignant tumors, suggesting it may act as a "conditional" oncogene. Resolving this paradox and understanding how a single gene can exhibit both oncogenic and tumor-suppressive properties is essential for successful drug targeting of RUNX. This review describes the evidence for the activities of RUNX3 in human cancer and proposes an explanation for the duality of RUNX3 involving the status of p53. In this model, p53 deficiency causes RUNX3 to become oncogenic, leading to aberrant upregulation of MYC.

Runt-Related Transcription Factor 3 Promotes Acute Myeloid Leukemia Progression

Acute myeloid leukemia (AML) is an aggressive hematological malignancy with high relapse/refractory rate. Genetic and epigenetic abnormalities are driving factors for leukemogenesis. RUNX1 and RUNX2 from the Runt-related transcription factor (RUNX) family played important roles in AML pathogenesis. However, the relationship between RUNX3 and AML remains unclear. Here, we found that RUNX3 was a super-enhancer-associated gene and highly expressed in AML cells. The Cancer Genome Atlas (TCGA) database showed high expression of RUNX3 correlated with poor prognosis of AML patients. We observed that Runx3 knockdown significantly inhibited leukemia progression by inducing DNA damage to enhance apoptosis in murine AML cells. By chromatin immunoprecipitation sequencing (ChIP-seq) analysis, we discovered that RUNX3 in AML cells mainly bound more genes involved in DNA-damage repair and antiapoptosis pathways compared to that in normal bone marrow cells. Runx3 knockdown obviously inhibited the expression of these genes in AML cells. Overall, we identified RUNX3 as an oncogene overexpressed in AML cells, and Runx3 knockdown suppressed AML progression by inducing DNA damage and apoptosis.

Hydrochlorothiazide Use and Risk of Nonmelanoma Skin Cancers: A Biological Plausibility Study

Recent studies reported the association between increased risk of nonmelanoma skin cancers (NMSCs) and the use of hydrochlorothiazide (HCTZ), one of the most commonly prescribed diuretic, antihypertensive drug, over the world. Although HCTZ is known to be photosensitizing, the mechanisms involved in its potential prophotocarcinogenic effects remain unclear. Under acute exposure, therapeutically relevant concentrations of HCTZ (70, 140, and 370 ng/mL) amplified UVA-induced double-strand breaks, oxidative DNA, and protein damage in HaCaT human keratinocytes, and this effect was associated to a defective activity of the DNA repair enzyme, OGG1. Oxidative damage to DNA, but not that to proteins, was reversible within few hours. After chronic, combined exposure to HCTZ (70 ng/mL) and UVA (10 J/cm2), for 9 weeks, keratinocytes acquired a dysplastic-like phenotype characterized by a multilayered morphology and alterations in cell size, shape, and contacts. At the ultrastructural level, several atypical and enlarged nuclei and evident nucleoli were also observed. These transformed keratinocytes were apoptosis resistant, exhibited enhanced clonogenicity capacity, increased DNA damage and inflammation, defective DNA repair ability, and increased expression of the oncogene ΔNp63α and intranuclear β-catenin accumulation (a hallmark of Wnt pathway activation), compared to those treated with UVA alone. None of these molecular, morphological, or functional effects were observed in cells treated with HCTZ alone. All these features resemble in part those of preneoplastic lesions and NMSCs and provide evidence of a biological plausibility for the association among exposure to UVA, use of HCTZ, and increased risk of NMSCs. These results are of translational relevance since we used environmentally relevant UVA doses and tested HCTZ at concentrations that reflect the plasma levels of doses used in clinical practice. This study also highlights that drug safety data should be followed by experimental evaluations to clarify the mechanistic aspects of adverse events.

Small peptide inhibitor from the sequence of RUNX3 disrupts PAK1-RUNX3 interaction and abrogates its phosphorylation-dependent oncogenic function

P21 Activated Kinase 1 (PAK1) is an oncogenic serine/threonine kinase known to play a significant role in the regulation of cytoskeleton and cell morphology. Runt-related transcription factor 3 (RUNX3) was initially known for its tumor suppressor function, but recent studies have reported the oncogenic role of RUNX3 in various cancers. Previous findings from our laboratory provided evidence that Threonine 209 phosphorylation of RUNX3 acts as a molecular switch in dictating the tissue-specific dualistic functions of RUNX3 for the first time. Based on these proofs and to explore the translational significance of these findings, we designed a small peptide (RMR) from the protein sequence of RUNX3 flanking the Threonine 209 phosphorylation site. The selection of this specific peptide from multiple possible peptides was based on their binding energies, hydrogen bonding, docking efficiency with the active site of PAK1 and their ability to displace PAK1-RUNX3 interaction in our prediction models. We found that this peptide is stable both in in vitro and in vivo conditions, not toxic to normal cells and inhibits the Threonine 209 phosphorylation in RUNX3 by PAK1. We also tested the efficacy of this peptide to block the RUNX3 Threonine 209 phosphorylation mediated tumorigenic functions in in vitro cell culture models, patient-derived explant (PDE) models and in in vivo tumor xenograft models. These results proved that this peptide has the potential to be developed as an efficient therapeutic molecule for targeting RUNX3 Threonine 209 phosphorylation-dependent tumor phenotypes.

Oestrogen up-regulates DNMT1 and leads to the hypermethylation of RUNX3 in the malignant transformation of ovarian endometriosis

RESEARCH QUESTION

What is the mechanism of hypermethylation of runt-related transcription factor 3 (RUNX3) in the eutopic endometrium of endometriosis as biomarker in the malignant transformation of endometriosis?

DESIGN

Methylation-specific polymerase chain reaction was used to analyse the methylation status of RUNX3 in endometriosis-associated ovarian cancer (EAOC). Primary eutopic endometrial stromal cells (ESC) were isolated from the uteri of patients with ovarian endometriosis. After RUNX3 knockdown by RNA interference technology or ESC treated with oestradiol, the proliferation and invasion ability were evaluated in ESC by using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) and transwell assays.

RESULTS

The frequency of methylation of RUNX3 in neoplastic tissue in the EAOC group was significantly higher than that in the ectopic endometrium of the endometriosis group (P < 0.001), and the frequency of methylation of RUNX3 in the eutopic endometrium of the EAOC group was significantly higher than that in the endometriosis group (P < 0.001). However, there was no significant difference in the eutopic endometrium when compared between the endometriosis group and the control endometrium group (P = 0.233). Silencing RUNX3 promoted the proliferation and invasion of ESC (P < 0.001 and P < 0.001). Following intervention with oestrogen, it was observed that the oestradiol group showed higher levels of RUNX3 methylation (P < 0.001) and DNA methyltransferase 1 (DNMT1) mRNA and protein expression (P < 0.001 and P < 0.001), and lower RUNX3 mRNA and protein expression when compared with the ESC group (P < 0.001 and P < 0.001).

CONCLUSION

This study demonstrated that hypermethylation of the RUNX3 was related to the malignant transformation of endometriosis and that this process was related to corresponding changes in the eutopic endometrium. Furthermore, the 'oestrogen-DNMT1' signalling pathway may induce the hypermethylation of RUNX3 to promote the malignant transformation of endometriosis.

Distinct association of RUNX family expression with genetic alterations and clinical outcome in acute myeloid leukemia

BACKGROUND

The runt-related transcription factor family (RUNXs) including RUNX1, RUNX2, and RUNX3 are key transcriptional regulators in normal hematopoiesis. RUNXs dysregulations caused by aberrant expression or mutation are frequently seen in various human cancers especially in acute myeloid leukemia (AML).

OBJECTIVE

We systemically analyzed the expression of RUNXs and their relationship with clinic-pathological features and prognosis in AML patients.

METHODS

Expression of RUNXs was analyzed between AML patients and normal controls from The Cancer Genome Atlas (TCGA) and Genotype-Tissue Expression (GTEx) projects. Correlations between RUNXs expression and clinical features together with survival were further analyzed.

RESULTS

All RUNXs expression in AML patients was significantly increased as compared with controls. RUNXs expression was found to be significantly associated with genetic abnormalities such as RUNX1 mutation, t(8;21) and inv(16)/t(16;16). By Kaplan-Meier analysis, only RUNX3 overexpression was associated with shorter overall survival (OS) and disease-free survival (DFS) among non-M3 AML patients. Notably, in high RUNX3 expression groups, patients received hematopoietic stem cell transplantation (HSCT) had markedly better OS and DFS than patients without HSCT among both all AML and non-M3 AML. In low RUNX3 expression groups, there were no significant differences in OS and DFS between HSCT and non-HSCT groups among both all AML and non-M3 AML. In addition, a total of 835 differentially expressed genes and 69 differentially expressed microRNAs were identified to be correlated with RUNX3 expression in AML.

CONCLUSION

RUNXs overexpression was a frequent event in AML, and was closely associated with diverse genetic alterations. Moreover, RUNX3 expression may be associated with clinical outcome, and helpful for guiding treatment choice between HSCT and chemotherapy in AML.

Epigenetic Alterations in Keratinocyte Carcinoma

Basal cell carcinoma (BCC) and squamous cell carcinoma (SCC) are both derived from epidermal keratinocytes but are phenotypically diverse. To improve the understanding of keratinocyte carcinogenesis, it is critical to understand epigenetic alterations, especially those that govern gene expression. We examined changes to the enhancer-associated histone acetylation mark H3K27ac by mapping matched tumor-normal pairs from 11 patients (five with BCC and six with SCC) undergoing Mohs surgery. Our analysis uncovered cancer-specific enhancers on the basis of differential H3K27ac peaks between matched tumor-normal pairs. We also uncovered biological pathways potentially altered in keratinocyte carcinoma, including enriched epidermal development and Wnt signaling pathways enriched in BCCs and enriched immune response and cell activation pathways in SCCs. We also observed enrichment of transcription factors that implicated SMAD and JDP2 in BCC pathogenesis and FOXP1 in SCC pathogenesis. On the basis of these findings, we prioritized three loci with putative regulation events (FGFR2 enhancer in BCC, intragenic regulation of FOXP1 in SCC, and WNT5A promoter in both subtypes) and validated our findings with published gene expression data. Our findings highlight unique and shared epigenetic alterations in histone modifications and potential regulators for BCCs and SCCs that likely impact the divergent oncogenic pathways, paving the way for targeted drug discoveries.

RUNX3 Transcript Variants Have Distinct Roles in Ovarian Carcinoma and Differently Influence Platinum Sensitivity and Angiogenesis

Simple Summary

Epithelial ovarian cancer treatment is limited by missing predictive markers, frequent chemotherapy resistance and an incomplete understanding of the biology of tumors. Earlier work proved that hypermethylation of the gene RUNX3 coding for a transcription factor has prognostic value, and RUNX3 transcript variant overexpression, regulated by this epigenetic mechanism, influences cisplatin sensitivity and malignant properties of cells contrary. The present data validate RUNX3 transcript variant-specific effects for high-grade serous ovarian cancer and identify RUNX3-regulated genes and processes. Specifically, DNA damage repair and angiogenesis are influenced by RUNX3, and transcript variant 1 mediates stronger carcinogenic properties.

Abstract

The prognosis of late-stage epithelial ovarian cancer (EOC) patients is affected by chemotherapy response and the malignant potential of the tumor cells. In earlier work, we identified hypermethylation of the runt-related transcription factor 3 gene (RUNX3) as a prognostic biomarker and contrary functions of transcript variants (TV1 and TV2) in A2780 and SKOV3 cells. The aim of the study was to further validate these results and to increase the knowledge about RUNX3 function in EOC. New RUNX3 overexpression models of high-grade serous ovarian cancer (HGSOC) were established and analyzed for phenotypic (IC₅₀ determination, migration, proliferation and angiogenesis assay, DNA damage analysis) and transcriptomic consequences (NGS) of RUNX3 TV1 and TV2 overexpression. Platinum sensitivity was affected by a specific transcript variant depending on BRCA background. RUNX3 TV2 induced an increased sensitivity in BRCA1^wt cells (OVCAR3), whereas TV1 increased the sensitivity and induced a G2/M arrest under treatment in BRCA1^mut cells (A13-2-12). These different phenotypes relate to differences in DNA repair: homologous recombination deficient A13-2-12 cells show less γH2AX foci despite higher levels of Pt-DNA adducts. RNA-Seq analyses prove transcript variant and cell-line-specific RUNX3 effects. Pathway analyses revealed another clinically important function of RUNX3—regulation of angiogenesis. This was confirmed by thrombospondin1 analyses, HUVEC spheroid sprouting assays and proteomic profiling. Importantly, conditioned media (CM) from RUNX3 TV1 overexpressing A13-2-12 cells induced an increased HUVEC sprouting. Altogether, the presented data support the hypothesis of different functions of RUNX3 transcript variants related to the clinically relevant processes—platinum resistance and angiogenesis.

Identification and validation of an immune-related gene signature predictive of overall survival in colon cancer

The heterogeneity and complexity of tumor-immune microenvironments lead to diverse immunotherapy effects among colon cancer patients. It is crucial to identify immune microenvironment-related biomarkers and construct prognostic risk models. In this study, the immune and stromal scores of 415 cases from TCGA were calculated using the ESTIMATE algorithm. AXIN2, CCL22, CLEC10A, CRIP2, RUNX3, and TRPM5 were screened and established a prognostic immune-related gene (IRG) signature using by univariate, LASSO, and multivariate Cox regression models. The predicted performance of IRG signature was external validated by GSE39582 (n=519). Stratified survival analysis showed IRG signature was an effective predictor of survival in patients with different clinical characteristics. The protein expression level of six genes was validated by immunohistochemistry analysis. Difference analysis indicated the mutation rate, immune cell of resting NK cells and regulatory T cells infiltration and four immune checkpoints of PD-1, PD-L1, LAG3 and VSIR expression levels in the high-risk group were significantly higher than those in the low-risk group. A nomogram incorporating the gene signatures and clinical factors was demonstrated had a good accuracy (1-, 3-, and 5-year AUC= 0.799, 0.791, 0.738). Our study identified a novel IRG signature, which may provide some references for the clinical precision immunotherapy of patients.

Oncosuppressive Role of RUNX3 in Human Astrocytomas

Background

Gliomas are the most common and aggressive among primary malignant brain tumours with significant inter- and intratumour heterogeneity in histology, molecular profile, and patient outcome. However, molecular targets that could provide reliable diagnostic and prognostic information on this type of cancer are currently unknown. Recent studies show that certain phenotypes of gliomas such as malignancy, resistance to therapy, and relapses are associated with the epigenetic alterations of tumour-specific genes. Runt-related transcription factor 3 (RUNX3) is feasible tumour suppressor gene since its inactivation was shown to be related to carcinogenesis.

Aim

The aim of the study was to elucidate RUNX3 changes in different regulation levels of molecular biology starting from epigenetics to function in particular cases of astrocytic origin tumours of different grade evaluating significance of molecular changes of RUNX3 for patient clinical characteristics as well as evaluate RUNX3 reexpression effect to GBM cells.

Methods

The methylation status and protein expression levels of RUNX3 were measured by methylation-specific PCR and Western blot in 136 and 72 different malignancy grade glioma tissues, respectively. Lipotransfection and MTT were applied for proliferation assessment in U87-MG cells.

Results

We found that RUNX3 was highly methylated and downregulated in GBM. RUNX3 promoter methylation was detected in 69.4% of GBM (n=49) as compared to 0 to 17.2% in I-III grade astrocytomas (n=87). Weighty lower RUNX3 protein level was observed in GMB specimens compared to grade II-III astrocytomas. Correlation test revealed a weak but significant link among Runx3 methylation and protein level. Kaplan-Meier analysis showed that increased RUNX3 methylation and low protein level were both associated with shorter patient survival (p<0.05). Reexpression of RUNX3 in U87-MG cells significantly reduced glioma cell viability compared to control transfection.

Conclusions

The results demonstrate that RUNX3 gene methylation and protein expression downregulation are glioma malignancy dependent and contribute to tumour progression.

RUNX3 Promotes the Tumorigenic Phenotype in KGN, a Human Granulosa Cell Tumor-Derived Cell Line

Granulosa cell tumors of the ovary (GCT) are the predominant type of ovarian sex cord/stromal tumor. Although prognosis is generally favorable, the outcome for advanced and recurrent GCT is poor. A better understanding of the molecular pathogenesis of GCT is critical to developing effective therapeutic strategies. Here we have examined the potential role of the runt-related transcription factor RUNX3. There are only two GCT cell lines available. While RUNX3 is silenced in the GCT cell line KGN cells, it is highly expressed in another GCT cell line, COV434 cells. Re-expression of RUNX3 promotes proliferation, anchorage-independent growth, and motility in KGN cells in vitro and tumor formation in mice in vivo. Furthermore, expression of a dominant negative form of RUNX3 decreases proliferation of COV434 cells. To address a potential mechanism of action, we examined expression of cyclin D2 and the CDK inhibitor p27^Kip1, two cell cycle regulators known to be critical determinants of GCT cell proliferation. We found that RUNX3 upregulates the expression of cyclin D2 at the mRNA and protein level, and decreases the level of the p27^Kip1 protein, but not p27^Kip1 mRNA. In conclusion, we demonstrate that RUNX proteins are expressed in GCT cell lines and human GCT specimens, albeit at variable levels, and RUNX3 may play an oncogenic role in a subset of GCTs.

RUNX3 suppresses metastasis and stemness by inhibiting Hedgehog signaling in colorectal cancer

Disabled tumor suppressor genes and hyperactive oncogenes greatly contribute to cell fates during cancer development because of their genetic alterations such as somatic mutations. However, little is known about how tumor suppressor genes react to diverse oncogenes during tumor progression. Our previous study showed that RUNX3 inhibits invasiveness by preventing vascular endothelial growth factor secretion and suppressed endothelial cell growth and tube formation in colorectal cancer (CRC). Hedgehog signaling is crucial for the physiological maintenance and self-renewal of stem cells, and its deregulation is responsible for their tumor development. The mechanisms that inhibit this pathway during proliferation remain poorly understood. Here, we found that the tumor suppressor RUNX3 modulates tumorigenesis in response to cancer cells induced by inhibiting oncogene GLI1 ubiquitination. Moreover, we demonstrated that RUNX3 and GLI1 expression were inversely correlated in CRC cells and tissues. We observed a direct interaction between RUNX3 and GLI1, promoting ubiquitination of GLI1 at the intracellular level. Increased ubiquitination of GLI1 was induced by the E3 ligase β-TrCP. This novel RUNX3-dependent regulatory loop may limit the extent and duration of Hedgehog signaling during extension of the tumor initiation capacity. On the basis of our results, identification of agents that induce RUNX3 may be useful for developing new and effective therapies for CRC.

Low RUNX3 expression alters dendritic cell function in patients with systemic sclerosis and contributes to enhanced fibrosis

Objectives

Systemic sclerosis (SSc) is an autoimmune disease with unknown pathogenesis manifested by inflammation, vasculopathy and fibrosis in skin and internal organs. Type I interferon signature found in SSc propelled us to study plasmacytoid dendritic cells (pDCs) in this disease. We aimed to identify candidate pathways underlying pDC aberrancies in SSc and to validate its function on pDC biology.

Methods

In total, 1193 patients with SSc were compared with 1387 healthy donors and 8 patients with localised scleroderma. PCR-based transcription factor profiling and methylation status analyses, single nucleotide polymorphism genotyping by sequencing and flow cytometry analysis were performed in pDCs isolated from the circulation of healthy controls or patients with SSc. pDCs were also cultured under hypoxia, inhibitors of methylation and hypoxia-inducible factors and runt-related transcription factor 3 (RUNX3) levels were determined. To study Runx3 function, Itgax-Cre:Runx3f/f mice were used in in vitro functional assay and bleomycin-induced SSc skin inflammation and fibrosis model.

Results

Here, we show downregulation of transcription factor RUNX3 in SSc pDCs. A higher methylation status of the RUNX3 gene, which is associated with polymorphism rs6672420, correlates with lower RUNX3 expression and SSc susceptibility. Hypoxia is another factor that decreases RUNX3 level in pDC. Mouse pDCs deficient of Runx3 show enhanced maturation markers on CpG stimulation. In vivo, deletion of Runx3 in dendritic cell leads to spontaneous induction of skin fibrosis in untreated mice and increased severity of bleomycin-induced skin fibrosis.

Conclusions

We show at least two pathways potentially causing low RUNX3 level in SSc pDCs, and we demonstrate the detrimental effect of loss of Runx3 in SSc model further underscoring the role of pDCs in this disease.

Emerging role of RUNX3 in the regulation of tumor microenvironment

A number of genes have been therapeutically targeted to relieve cancer, but cancer relapse is still a growing issue. The concept that the surrounding tumor environment is critical for the progression of cancer may foster an answer to the issue of cancer malignancy. Runt domain transcription factors (RUNX1, 2, and 3) are evolutionarily conserved and have been intensively studied for their roles in normal development and pathological conditions. During tumor growth, a hypoxic microenvironment and infiltration of the tumor by immune cells are common phenomena. In this review, we briefly introduce the consequences of hypoxia and immune cell infiltration into the tumor microenvironment with a focus on RUNX3 as a critical regulator. Furthermore, based on our current knowledge of the functional role of RUNX3 in hypoxia and immune cell maintenance, a probable therapeutic intervention is suggested for the effective management of tumor growth and malignancy. [BMB Reports 2018; 51(4): 174-181].

Wnt Signaling in Adult Epithelial Stem Cells and Cancer

Wnt/β-catenin signaling is integral to the homeostasis and regeneration of many epithelial tissues due to its critical role in adult stem cell regulation. It is also implicated in many epithelial cancers, with mutations in core pathway components frequently present in patient tumors. In this chapter, we discuss the roles of Wnt/β-catenin signaling and Wnt-regulated stem cells in homeostatic, regenerative and cancer contexts of the intestines, stomach, skin, and liver. We also examine the sources of Wnt ligands that form part of the stem cell niche. Despite the diversity in characteristics of various tissue stem cells, the role(s) of Wnt/β-catenin signaling is generally coherent in maintaining stem cell fate and/or promoting proliferation. It is also likely to play similar roles in cancer stem cells, making the pathway a salient therapeutic target for cancer. While promising progress is being made in the field, deeper understanding of the functions and signaling mechanisms of the pathway in individual epithelial tissues will expedite efforts to modulate Wnt/β-catenin signaling in cancer treatment and tissue regeneration.

Roles of RUNX in Solid Tumors

All RUNX genes have been implicated in the development of solid tumors, but the role each RUNX gene plays in the different tumor types is complicated by multiple interactions with major signaling pathways and tumor heterogeneity. Moreover, for a given tissue type, the specific role of each RUNX protein is distinct at different stages of differentiation. A regulatory function for RUNX in tissue stem cells points sharply to a causal effect in tumorigenesis. Understanding how RUNX dysregulation in cancer impinges on normal biological processes is important for identifying the molecular mechanisms that lead to malignancy. It will also indicate whether restoration of proper RUNX function to redirect cell fate is a feasible treatment for cancer. With the recent advances in RUNX research, it is time to revisit the many mechanisms/pathways that RUNX engage to regulate cell fate and decide whether cells proliferate, differentiate or die.

UnPAKing RUNX3 functions-Both sides of the coin

Post translational modifications of RUNX3 have been shown to play an important role in directing RUNX3 functions. In this review we highlight the phosphorylation dependent functions of RUNX3 as regulated by PAK1 and its implications on tumorigenesis.

Wnt/β-catenin signaling in adult mammalian epithelial stem cells

Adult stem cells self-renew and replenish differentiated cells in various organs and tissues throughout a mammal's life. Over the last 25 years an ever-growing body of knowledge has unraveled the essential regulation of adult mammalian epithelia by the canonical Wnt signaling with its key intracellular effector β-catenin. In this review, we discuss the principles of the signaling pathway and its role in adult epithelial stem cells of the intestine and skin during homeostasis and tumorigenesis. We further highlight the research that led to the identification of new stem cell markers and methods to study adult stem cells ex vivo.

RUNX3 is oncogenic in natural killer/T-cell lymphoma and is transcriptionally regulated by MYC

RUNX3, runt-domain transcription factor, is a master regulator of gene expression in major developmental pathways. It acts as a tumor suppressor in many cancers but is oncogenic in certain tumors. We observed upregulation of RUNX3 mRNA and protein expression in nasal-type extranodal natural killer (NK)/T-cell lymphoma (NKTL) patient samples and NKTL cell lines compared to normal NK cells. RUNX3 silenced NKTL cells showed increased apoptosis and reduced cell proliferation. Potential binding sites for MYC were identified in the RUNX3 enhancer region. Chromatin immunoprecipitation-quantitative PCR revealed binding activity between MYC and RUNX3. Co-transfection of the MYC expression vector with RUNX3 enhancer reporter plasmid resulted in activation of RUNX3 enhancer indicating that MYC positively regulates RUNX3 transcription in NKTL cell lines. Treatment with a small-molecule MYC inhibitor (JQ1) caused significant downregulation of MYC and RUNX3, leading to apoptosis in NKTL cells. The growth inhibition resulting from depletion of MYC by JQ1 was rescued by ectopic MYC expression. In summary, our study identified RUNX3 overexpression in NKTL with functional oncogenic properties. We further delineate that MYC may be an important upstream driver of RUNX3 upregulation and since MYC is upregulated in NKTL, further study on the employment of MYC inhibition as a therapeutic strategy is warranted.

Runx Family Genes in Tissue Stem Cell Dynamics

The Runx family genes play important roles in development and cancer, largely via their regulation of tissue stem cell behavior. Their involvement in two organs, blood and skin, is well documented. This review summarizes currently known Runx functions in the stem cells of these tissues. The fundamental core mechanism(s) mediated by Runx proteins has been sought; however, it appears that there does not exist one single common machinery that governs both tissue stem cells. Instead, Runx family genes employ multiple spatiotemporal mechanisms in regulating individual tissue stem cell populations. Such specific Runx requirements have been unveiled by a series of cell type-, developmental stage- or age-specific gene targeting studies in mice. Observations from these experiments revealed that the regulation of stem cells by Runx family genes turned out to be far more complex than previously thought. For instance, although it has been reported that Runx1 is required for the endothelial-to-hematopoietic cell transition (EHT) but not thereafter, recent studies clearly demonstrated that Runx1 is also needed during the period subsequent to EHT, namely at perinatal stage. In addition, Runx1 ablation in the embryonic skin mesenchyme eventually leads to complete loss of hair follicle stem cells (HFSCs) in the adult epithelium, suggesting that Runx1 facilitates the specification of skin epithelial stem cells in a cell extrinsic manner. Further in-depth investigation into how Runx family genes are involved in stem cell regulation is warranted.

Runx3 and Cell Fate Decisions in Pancreas Cancer

The RUNX family transcription factors are critical regulators of development and frequently dysregulated in cancer. RUNX3, the least well characterized of the three family members, has been variously described as a tumor promoter or suppressor, sometimes with conflicting results and opinions in the same cancer and likely reflecting a complex role in oncogenesis. We recently identified RUNX3 expression as a crucial determinant of the predilection for pancreatic ductal adenocarcinoma (PDA) cells to proliferate locally or promulgate throughout the body. High RUNX3 expression induces the production and secretion of soluble factors that support metastatic niche construction and stimulates PDA cells to migrate and invade, while simultaneously suppressing proliferation through increased expression of cell cycle regulators such as CDKN1A/p21 ^WAF1/CIP1 . RUNX3 expression and function are coordinated by numerous transcriptional and post-translational inputs, and interactions with diverse cofactors influence whether the resulting RUNX3 complexes enact tumor suppressive or tumor promoting programs. Understanding these exquisitely context-dependent tumor cell behaviors has the potential to inform clinical decision-making including the most appropriate timing and sequencing of local vs. systemic therapies.

Runx3 in Immunity, Inflammation and Cancer

In this chapter we summarize the pros and cons of the notion that Runx3 is a major tumor suppressor gene (TSG). Inactivation of TSGs in normal cells provides a viability/growth advantage that contributes cell-autonomously to cancer. More than a decade ago it was suggested that RUNX3 is involved in gastric cancer development, a postulate extended later to other epithelial cancers portraying RUNX3 as a major TSG. However, evidence that Runx3 is not expressed in normal gastric and other epithelia has challenged the RUNX3-TSG paradigm. In contrast, RUNX3 is overexpressed in a significant fraction of tumor cells in various human epithelial cancers and its overexpression in pancreatic cancer cells promotes their migration, anchorage-independent growth and metastatic potential. Moreover, recent high-throughput quantitative genome-wide studies on thousands of human samples of various tumors and new investigations of the role of Runx3 in mouse cancer models have unequivocally demonstrated that RUNX3 is not a bona fide cell-autonomous TSG. Importantly, accumulating data demonstrated that RUNX3 functions in control of immunity and inflammation, thereby indirectly influencing epithelial tumor development.

Inhibition of Hedgehog-dependent tumors and cancer stem cells by a newly identified naturally occurring chemotype

Hedgehog (Hh) inhibitors have emerged as valid tools in the treatment of a wide range of cancers. Indeed, aberrant activation of the Hh pathway occurring either by ligand-dependent or -independent mechanisms is a key driver in tumorigenesis. The smoothened (Smo) receptor is one of the main upstream transducers of the Hh signaling and is a validated target for the development of anticancer compounds, as underlined by the FDA-approved Smo antagonist Vismodegib (GDC-0449/Erivedge) for the treatment of basal cell carcinoma. However, Smo mutations that confer constitutive activity and drug resistance have emerged during treatment with Vismodegib. For this reason, the development of new effective Hh inhibitors represents a major challenge for cancer therapy. Natural products have always represented a unique source of lead structures in drug discovery, and in recent years have been used to modulate the Hh pathway at multiple levels. Here, starting from an in house library of natural compounds and their derivatives, we discovered novel chemotypes of Hh inhibitors by mean of virtual screening against the crystallographic structure of Smo. Hh functional based assay identified the chalcone derivative 12 as the most effective Hh inhibitor within the test set. The chalcone 12 binds the Smo receptor and promotes the displacement of Bodipy-Cyclopamine in both Smo WT and drug-resistant Smo mutant. Our molecule stands as a promising Smo antagonist able to specifically impair the growth of Hh-dependent tumor cells in vitro and in vivo and medulloblastoma stem-like cells and potentially overcome the associated drug resistance.

WNT Signaling in Cutaneous Squamous Cell Carcinoma: A Future Treatment Strategy?

The molecular mechanisms underlying cutaneous squamous cell carcinoma are less well established than those for other common skin cancers, but recent evidence has highlighted a potentially critical role for WNT signaling in both the development and progression of cutaneous squamous cell carcinoma. WNT pathways are aberrantly regulated in multiple tumor types (albeit in a context-dependent manner), and this has stimulated the development of WNT inhibitory compounds for cancer treatment. In this review, we examine existing evidence for a role of WNT signaling in cutaneous squamous cell carcinoma and discuss if WNT inhibition represents a realistic therapeutic strategy for the future.

Basal cell carcinoma of the skin (part 1): epidemiology, pathology and genetic syndromes

Basal cell carcinoma (BCC) is the most common skin cancer worldwide with increasing incidence, but difficult to assess due to the current under registration practice. Despite the low mortality rate, BCC is a cause of great morbidity and an economic burden to health services. There are several risk factors that increase the risk of BCC and partly explain its incidence. Low-penetrance susceptibility alleles, as well as genetic alterations in signaling pathways, namely SHH pathway, also contribute to the carcinogenesis. BCC associate with several genetic syndromes, of which basal cell nevus syndrome is the most common.

The RUNX family: developmental regulators in cancer

RUNX proteins belong to a family of metazoan transcription factors that serve as master regulators of development. They are frequently deregulated in human cancers, indicating a prominent and, at times, paradoxical role in cancer pathogenesis. The contextual cues that direct RUNX function represent a fast-growing field in cancer research and could provide insights that are applicable to early cancer detection and treatment. This Review describes how RUNX proteins communicate with key signalling pathways during the multistep progression to malignancy; in particular, we highlight the emerging partnership of RUNX with p53 in cancer suppression.

Runx3 at the interface of immunity, inflammation and cancer

Inactivation of tumor suppressor genes (TSG) in normal cells provides a viability/growth advantage that contributes cell-autonomously to cancer. More than a decade ago claims arose that the RUNX3 member of the RUNX transcription factor family is a major TSG inactivated in gastric cancer, a postulate extended later to other cancers. However, evidence that Runx3 is not expressed in normal gastric and other epithelia has challenged the RUNX3-TSG paradigm. Here we critically re-appraise this paradigm in light of recent high-throughput, quantitative genome-wide studies on thousands of human samples of various tumors and new investigations of the role of Runx3 in mouse cancer models. Collectively, these studies unequivocally demonstrate that RUNX3 is not a bona fide cell-autonomous TSG. Accordingly, RUNX3 is not recognized as a TSG and is not included among the 2000 cancer genes listed in the "Cancer Gene Census" or "Network for Cancer Genes" repositories. In contrast, RUNX3 does play important functions in immunity and inflammation and may thereby indirectly influence epithelial tumor development.

RUNX3 facilitates growth of Ewing sarcoma cells

Ewing sarcoma is an aggressive pediatric small round cell tumor that predominantly occurs in bone. Approximately 85% of Ewing sarcomas harbor the EWS/FLI fusion protein, which arises from a chromosomal translocation, t(11:22)(q24:q12). EWS/FLI interacts with numerous lineage-essential transcription factors to maintain mesenchymal progenitors in an undifferentiated state. We previously showed that EWS/FLI binds the osteogenic transcription factor RUNX2 and prevents osteoblast differentiation. In this study, we investigated the role of another Runt-domain protein, RUNX3, in Ewing sarcoma. RUNX3 participates in mesenchymal-derived bone formation and is a context dependent tumor suppressor and oncogene. RUNX3 was detected in all Ewing sarcoma cells examined, whereas RUNX2 was detected in only 73% of specimens. Like RUNX2, RUNX3 binds to EWS/FLI via its Runt domain. EWS/FLI prevented RUNX3 from activating the transcription of a RUNX-responsive reporter, p6OSE2. Stable suppression of RUNX3 expression in the Ewing sarcoma cell line A673 delayed colony growth in anchorage independent soft agar assays and reversed expression of EWS/FLI-responsive genes. These results demonstrate an important role for RUNX3 in Ewing sarcoma.

Lineage-specific RUNX3 hypomethylation marks the preneoplastic immune component of gastric cancer

Runt domain transcription factor 3 (RUNX3) is widely regarded as a tumour-suppressor gene inactivated by DNA hypermethylation of its canonical CpG (cytidine-phosphate-guanidine) island (CGI) promoter in gastric cancer (GC). Absence of RUNX3 expression from normal gastric epithelial cells (GECs), the progenitors to GC, coupled with frequent RUNX3 overexpression in GC progression, challenge this longstanding paradigm. However, epigenetic models to better describe RUNX3 deregulation in GC have not emerged. Here, we identify lineage-specific DNA methylation at an alternate, non-CGI promoter (P1) as a new mechanism of RUNX3 epigenetic control. In normal GECs, P1 was hypermethylated and repressed, whereas in immune lineages P1 was hypomethylated and widely expressed. In human GC development, we detected aberrant P1 hypomethylation signatures associated with the early inflammatory, preneoplastic and tumour stages. Aberrant P1 hypomethylation was fully recapitulated in mouse models of gastric inflammation and tumorigenesis. Cell sorting showed that P1 hypomethylation reflects altered cell-type composition of the gastric epithelium/tumour microenvironment caused by immune cell recruitment, not methylation loss. Finally, via long-term culture of gastric tumour epithelium, we revealed that de novo methylation of the RUNX3 canonical CGI promoter is a bystander effect of oncogenic immortalization and not likely causal in GC pathogenesis as previously argued. We propose a new model of RUNX3 epigenetic control in cancer, based on immune-specific, non-CGI promoter hypomethylation. This novel epigenetic signature may have utility in early detection of GC and possibly other epithelial cancers with premalignant immune involvement.

RUNX3 expression is associated with sensitivity to pheophorbide a-based photodynamic therapy in keloids

Runt-related transcription factor 3 (RUNX3) has recently been reported to be a possible predictor of sensitivity of cancer cells for photodynamic therapy (PDT), a promising therapeutic modality for keloids. In this study, we aimed to elucidate the implications of RUNX3 for keloid pathogenesis and sensitivity to pheophorbide a-based PDT (Pa-PDT). RUNX3 and proliferating cell nuclear antigen (PCNA) expression were examined in 6 normal skin samples and 32 keloid tissue samples by immunohistochemistry. We found that RUNX3 expression was detected more often in keloid tissues than in dermis of normal skin. In keloid tissues, RUNX3 expression was significantly increased in patients presenting with symptoms of pain or pruritus, and was also significantly related to PCNA expression. The therapeutic effect of Pa-PDT was comparatively investigated in keloid fibroblasts (KFs) with and without RUNX3 expression. Significant differences were found after Pa-PDT between KFs with and without RUNX3 expression in cell viability, proliferative ability, type I collagen expression, generation of reactive oxygen species (ROS), and apoptotic cell death. In addition, RUNX3 expression was significantly decreased after Pa-PDT in KFs, and KFs with downregulation of RUNX3 showed significantly increased cell viability after Pa-PDT. Pa-PDT may be a potential therapeutic modality for keloids, and RUNX3, as a possible contributor to keloid pathogenesis, may improve sensitivity to Pa-PDT in KFs.

RUNX family members are covalently modified and regulated by PIAS1-mediated sumoylation

Transcription factors of the RUNX family (RUNXs), which play pivotal roles in normal development and neoplasia, are regulated by various post-translational modifications. To understand the molecular mechanisms underlying the regulation of RUNXs, we performed a large-scale functional genetic screen of a fly mutant library. The screen identified dPias (the fly ortholog of mammalian PIASs), an E3 ligase for the SUMO (small ubiquitin-like modifier) modification, as a novel genetic modifier of lz (the fly ortholog of mammalian RUNX3). Molecular biological analysis revealed that lz/RUNXs are sumoylated by dPias/PIAS1 at an evolutionarily conserved lysine residue (K372 of lz, K144 of RUNX1, K181 of RUNX2 and K148 of RUNX3). PIAS1-mediated sumoylation inhibited RUNX3 transactivation activity, and this modification was promoted by the AKT1 kinase. Importantly, PIAS1 failed to sumoylate some RUNX1 mutants associated with breast cancer. In nude mice, tumorigenicity was promoted by RUNX3 bearing a mutation in the sumoylation site, but suppressed by wild-type RUNX3. Our results suggest that RUNXs are sumoylated by PIAS1, and that this modification could play a critical role in the regulation of the tumor-suppressive activity of these proteins.

Expression of RUNX3 and β-catenin in the carcinogenesis of sporadic colorectal tubular adenoma

The aim of this study is to investigate the possible roles of runt-related transcription factor 3 (RUNX3) and β-catenin in the carcinogenesis of sporadic colorectal tubular adenomas. The expression of the RUNX3 and β-catenin proteins was evaluated by immunohistochemistry in 23 normal colorectal mucosa (NCM), 81 sporadic colorectal tubular adenomas with different dysplasias (SCTA-D) (mild n=33, moderate n=23, and severe n=25 dysplasia), and 48 sporadic colorectal tubular adenomas with cancerous changes (SCTA-Ca). RUNX3 methylation was assessed by methylation-specific polymerase chain reaction (MSP), combined with laser capture microdissection (LCM), in 17 NCM, 41 SCTA-D (mild n=15, moderate n=12, and severe n=14 dysplasia), and 17 SCTA-Ca tissues. Compared to NCM (82.6 %), RUNX3 in SCTA-D (54.3 %) and SCTA-Ca (27.1 %) was significantly downregulated (P<0.05). In NCM, SCTA-D, and SCTA-Ca, the incidence of positive expression for β-catenin was 13.0, 60.5, and 79.2 %, respectively. A statistically significant difference was observed (P<0.05). RUNX3 levels were markedly higher in adenoma with mild dysplasia (75.8 %) and moderate dysplasia (60.9 %) than in adenoma with severe dysplasia (20.0 %) (both with P<0.05). Likewise, the expression of β-catenin in severe dysplasia adenoma was 84.0 %, which was significantly higher than that in mild dysplasia adenoma (39.4 %). An inverse correlation was found between the protein expression of RUNX3 and β-catenin in SCTA-D and SCTA-Ca (P<0.05). MSP results showed that RUNX3 methylation in NCM, SCTA-D, and SCTA-Ca was 5.9, 17.1, and 41.2 %, respectively, with a statistically significant difference between NCM and SCTA-Ca (P<0.05). However, no significant difference of RUNX3 methylation was observed among different dysplasia groups. RUNX3 and β-catenin play important roles in the carcinogenesis of sporadic colorectal tubular adenomas. In addition, hypermethylation of RUNX3 can downregulate its expression.

The RUNX family in breast cancer: relationships with estrogen signaling

The three RUNX family members are lineage specific master regulators, which also have important, context-dependent roles in carcinogenesis as either tumor suppressors or oncogenes. Here we review evidence for such roles in breast cancer (BCa). RUNX1, the predominant RUNX family member in breast epithelial cells, has a tumor suppressor role reflected by many somatic mutations found in primary tumor biopsies. The classical tumor suppressor gene RUNX3 does not consist of such a mutation hot spot, but it too seems to inhibit BCa; it is often inactivated in human BCa tumors and its haploinsufficiency in mice leads to spontaneous BCa development. The tumor suppressor activities of RUNX1 and RUNX3 are mediated in part by antagonism of estrogen signaling, a feature recently attributed to RUNX2 as well. Paradoxically, however RUNX2, a master osteoblast regulator, has been implicated in various aspects of metastasis in general and bone metastasis in particular. Reciprocating the anti-estrogenic tumor suppressor activity of RUNX proteins, inhibition of RUNX2 by estrogens may help explain their context-dependent anti-metastatic roles. Such roles are reserved to non-osseous metastasis, because ERα is associated with increased, not decreased skeletal dissemination of BCa cells. Finally, based on diverse expression patterns in BCa subtypes, the successful use of future RUNX-based therapies will most likely require careful patient selection.

Genome-wide analysis of DNA methylation in tongue squamous cell carcinoma

Tongue squamous cell carcinoma (TSCC) is one of the most common types of oral cancer; however, its molecular mechanisms remain unclear. In this study, methylated DNA immunoprecipitation (MeDIP) coupled with methylation microarray analysis was performed to screen for aberrantly methylated genes in adjacent normal control and TSCC tissues from 9 patients. Roche NimbleGen Human DNA Methylation 385K Promoter Plus CpG Island Arrays were used to detect 28,226 CpG sites. A total of 1,269 hypermethylated CpG sites covering 330 genes and 1,385 hypomethylated CpG sites covering 321 genes were found in TSCC tissue, compared to the adjacent normal tissue. Furthermore, we chose three candidate genes (FBLN1, ITIH5 and RUNX3) and validated the DNA methylation status by methylation-specific PCR (MS-PCR) and the mRNA expression levels by reverse transcription PCR (RT-PCR). In TSCC tissue, FBLN1 and ITIH5 were shown to be hypermethylated and their expression was found to be decreased, and RUNX3 was shown to be hypomethylated, however, its mRNA expression was found to be increased. In addition, another three genes (BCL2L14, CDCP1 and DIRAS3) were tested by RT-PCR. In TSCC tissue, BCL2L14 and CDCP1 expressions were markedly upregulated, and DIRAS3 expression was significantly downregulated. Our data demonstrated that aberrant DNA methylation is observed in TSCC tissue and plays an important role in the tumorigenesis, development and progression of TSCC.

Wnt signaling in skin development, homeostasis, and disease

The skin and its appendages constitute the largest organ of the body. Its stratified epithelia offer protection from environmental stresses such as dehydration, irradiation, mechanical trauma, and pathogenic infection, whereas its appendages, like hair and sebaceous glands, help regulate body temperature as well as influence animal interaction and social behavior through camouflage and sexual signaling. To respond to and function effectively in a dynamic external environment, the skin and its appendages possess a remarkable ability to regenerate in a carefully controlled fashion. When this finely tuned homeostatic process is disrupted, skin diseases such as cancers may result. At present, the molecular signals that orchestrate cell proliferation, differentiation, and patterning in the skin remain incompletely understood. It is increasingly apparent that many morphogenetic pathways with key roles in development are also important in regulating skin biology. Of these, Wnt signaling has emerged as the dominant pathway controlling the patterning of skin and influencing the decisions of embryonic and adult stem cells to adopt the various cell lineages of the skin and its appendages, as well as subsequently controlling the function of differentiated skin cells. Here we will review established concepts and present recent advances in our understanding of the diverse roles that Wnt signaling plays in skin development, homeostasis, and disease.

Discovery of SLC3A2 cell membrane protein as a potential gastric cancer biomarker: implications in molecular imaging

Despite decreasing incidence and mortality, gastric cancer remains the second leading cause of cancer-related deaths in the world. Successful management of gastric cancer is hampered by lack of highly sensitive and specific biomarkers especially for early cancer detection. Cell surface proteins that are aberrantly expressed between normal and cancer cells are potentially useful for cancer imaging and therapy due to easy accessibility of these targets. Combining two-phase partition and isobaric tags for relative and absolute quantification methods, we compared the relative expression levels of membrane proteins between noncancer and gastric cancer cells. About 33% of the data set was found to be plasma membrane and associated proteins using this approach (compared to only 11% in whole cell analysis), several of which have never been previously implicated in gastric cancer. Upregulation of SLC3A2 in gastric cancer cells was validated by immunoblotting of a panel of 13 gastric cancer cell lines and immunohistochemistry on tissue microarrays comprising 85 matched pairs of normal and tumor tissues. Immunofluorescence and immunohistochemistry both confirmed the plasma membrane localization of SLC3A2 in gastric cancer cells. The data supported the notion that SLC3A2 is a potential biomarker that could be exploited for molecular imaging-based detection of gastric cancer.

RUNX3 downregulation in human lung adenocarcinoma is independent of p53, EGFR or KRAS status

RUNX3 aberrations play a pivotal role in the oncogenesis of breast, gastric, colon, skin and lung tissues. The aim of this study was to characterize further the expression of RUNX3 in lung cancers. To achieve this, a lung cancer tissue microarray (TMA), frozen lung cancer tissues and lung cell lines were examined for RUNX3 expression by immunohistochemistry, while the TMA was also examined for EGFR and p53 expression. RUNX3 promoter methylation status, and EGFR and KRAS mutation status were also investigated. Inactivation of RUNX3 was observed in 70% of the adenocarcinoma samples, and this was associated with promoter hypermethylation but not biased to EGFR/KRAS mutations. Our results suggest a central role of RUNX3 downregulation in pulmonary adenocarcinoma, which may not be dependent of other established cancer-causing pathways and may have important diagnostic and screening implications.

Absence of Runx3 expression in normal gastrointestinal epithelium calls into question its tumour suppressor function

The Runx3 transcription factor regulates cell fate decisions during embryonic development and in adults. It was previously reported that Runx3 is strongly expressed in embryonic and adult gastrointestinal tract (GIT) epithelium (Ep) and that its loss causes gastric cancer. More than 280 publications have based their research on these findings and concluded that Runx3 is indeed a tumour suppressor (TS). In stark contrast, using various measures, we found that Runx3 expression is undetectable in GIT Ep. Employing a variety of biochemical and genetic techniques, including analysis of Runx3-GFP and R26LacZ/Runx3^Cre or R26tdTomato/Runx3^Cre reporter strains, we readily detected Runx3 in GIT-embedded leukocytes, dorsal root ganglia, skeletal elements and hair follicles. However, none of these approaches revealed detectable Runx3 levels in GIT Ep. Moreover, our analysis of the original Runx3^LacZ/LacZ mice used in the previously reported study failed to reproduce the GIT expression of Runx3. The lack of evidence for Runx3 expression in normal GIT Ep creates a serious challenge to the published data and undermines the notion that Runx3 is a TS involved in cancer pathogenesis.

Role of DNA methylation in head and neck cancer

Head and neck cancer (HNC) is a heterogenous and complex entity including diverse anatomical sites and a variety of tumor types displaying unique characteristics and different etilogies. Both environmental and genetic factors play a role in the development of the disease, but the underlying mechanism is still far from clear. Previous studies suggest that alterations in the genes acting in cellular signal pathways may contribute to head and neck carcinogenesis. In cancer, DNA methylation patterns display specific aberrations even in the early and precancerous stages and may confer susceptibility to further genetic or epigenetic changes. Silencing of the genes by hypermethylation or induction of oncogenes by promoter hypomethylation are frequent mechanisms in different types of cancer and achieve increasing diagnostic and therapeutic importance since the changes are reversible. Therefore, methylation analysis may provide promising clinical applications, including the development of new biomarkers and prediction of the therapeutic response or prognosis. In this review, we aimed to analyze the available information indicating a role for the epigenetic changes in HNC.

Critical regions and spreading of runt-related transcription factor-3 C-phosphate-G (CpG) island methylation in human salivary gland adenoid cystic carcinoma

We investigated the spreading pattern of runt-related transcription factor-3 (RUNX3) C-phosphate-G (CpG) island (3478 base pairs) methylation in salivary gland adenoid cystic carcinoma. The methylation status of multiple regions within the runt-related transcription factor-3 promoter CpG island (3478 base pairs) was detected by real-time methylation-specific polymerase chain reaction, and the runt-related transcription factor-3 protein was detected with a Western blot in 19 salivary gland adenoid cystic carcinoma samples and the corresponding nonneoplastic salivary glands. The risk ratio between runt-related transcription factor-3 CpG island methylation and salivary gland adenoid cystic carcinoma progression was analyzed by the logistic analysis of variance model. A possible association between runt-related transcription factor-3 methylation, clinicopathologic parameters, and runt-related transcription factor-3 protein was analyzed. Hypermethylation initially occurs the most at the 5' region of runt-related transcription factor-3 CpG island before spreading to the transcription start site. The extent of methylation was found to be the highest in region nos. 1 and 2 among the successive 10 regions, which extend from the 5' region to the transcription start site within the runt-related transcription factor-3 CpG island. The extent of methylation is lowest at the transcription start site, both in salivary gland adenoid cystic carcinoma and in normal salivary glands. No methylation in the transcription start site was found in normal salivary glands. Logistic analysis of variance model indicates that the transcription start site within the runt-related transcription factor-3 promoter CpG island is critical for gene silencing. Western blots revealed that levels of the runt-related transcription factor-3 protein in adenoid cystic carcinoma samples are significantly lower than those in normal salivary glands (P < .001). Methylation of the runt-related transcription factor-3 CpG island spreads the most from 5' region to the transcription start site in adenoid cystic carcinoma tissues, and the transcription start site may be a critical region for the runt-related transcription factor-3 methylation. The spreading pattern of the runt-related transcription factor-3 methylation may play an a role in the progression of adenoid cystic carcinoma.

Expression of RUNX3 in skin cancers

BACKGROUND

Expression of Runt-related transcription factor 3 (RUNX3) is reduced in a large number of cancers. However, a few studies have reported higher expression of RUNX3 in several cancers, including basal cell carcinoma (BCC). In light of this, we explored the expression of RUNX3 in skin cancers generally, to determine whether it acts as an oncogene or a tumour-suppressor gene in skin tumours.

AIM

To investigate the expression of RUNX3 in normal skin and malignant skin tumours.

METHODS

RUNX3 expression was evaluated by western blotting in 24 specimens, comprising 6 malignant melanoma (MM), 6 squamous cell carcinoma (SCC), 6 BCC and 6 normal skin specimens. Immunohistochemical staining was carried out to analyse RUNX3 expression in 16 MM, 16 SCC and 16 BCC specimens. To identify where the protein was expressed, the cytoplasmic and nuclear protein expression of RUNX3 in skin cancer tissues was determined. A cell-proliferation study was performed on an MM line (G361) by small interfering (si)RNA transfection.

RESULTS

The western blotting experiments showed that RUNX3 was not expressed in normal skin tissues, but it was overexpressed in all MM and SCC samples, and in five of the six BCC samples. Using immunochemistry, RUNX3 was found to be overexpressed in all cancer tissues analysed. Subcellular fraction analysis revealed that RUNX3 was expressed in the nuclei but not the cytoplasm of all the skin cancer tissues analysed, and RUNX3 silencing by siRNA in G361 cells resulted in a decrease in proliferation.

CONCLUSIONS

Based on these results, we suggest that RUNX3 has an oncogenic potential and does not act as a tumour suppressor in skin cancers.

RUNX3 functions as an oncogene in ovarian cancer

OBJECTIVE

The Runt domain transcription factor, RUNX3, has been shown to be a tumor suppressor in a variety of cancers including gastric, colon and breast cancer. Interestingly, an oncogenic role for RUNX3 has also been suggested in basal cell carcinoma and head and neck cancer. Here, we explore the role of RUNX3 in ovarian cancer.

METHODS

Expression of RUNX3 mRNA and protein was evaluated in human ovarian cancer cell lines. In addition, subcellular localization of RUNX3 was also examined in cell lines and ovarian cancer tissues. Effect of exogenous RUNX3 expression and knockdown on cell proliferation was investigated by proliferation assays and a soft agar assay.

RESULTS

Expression of RUNX3 was detected in the nucleus of ovarian cancer cell lines and ovarian cancer tissues and was found to play a growth stimulatory role. RUNX3 knockdown resulted in a decrease in cell proliferation in liquid media as well as in soft agar. Despite the fact that exogenous expression of RUNX3 strongly inhibits cell growth in many cell types, RUNX3 promoted cell growth in ovarian cancer cell lines not expressing RUNX3.

CONCLUSION

RUNX3 is frequently expressed in the nuclei of ovarian cancer cell lines and plays an oncogenic role in ovarian cancer.