HOP/OB1/NECC1 promoter DNA is frequently hypermethylated and involved in tumorigenic ability in esophageal squamous cell carcinoma

hsa-miR-1301-3p Promotes the Proliferation and Migration of Nonsmall Cell Lung Cancer Cells and Reduces Radiosensitivity via Targeting Homeodomain-Only Protein Homeobox

Background: There is increasing evidence that abnormal expression of microRNAs is involved in the occurrence and progression of tumors. In previous experiments, we found that the content of hsa-miR-1301-3p in tumor tissues of patients with nonsmall cell lung cancer (NSCLC) showed an obvious upward trend compared with that in normal tissues. We performed a detailed study on the impact and underlying mechanism of hsa-miR-1301-3p in NSCLC cells. Methods: The impact of hsa-miR-1301-3p on NSCLC cell proliferation, apoptosis, migration, and invasion was examined using colony formation, flow cytometry, modified Boyden chamber, and wound healing assays. Different doses of radiation were applied to NSCLC cells to investigate their sensitivity to radiotherapy. The potential target gene of hsa-miR-1301-3p was determined by dual-luciferase reporter assay and immunoblotting. Result: hsa-miR-1301-3p was upregulated in NSCLC tissues and cells. hsa-miR-1301-3p effectively promoted the rapid proliferation, migration, and invasion of NSCLC cells, while inhibiting apoptosis. It also induced radioresistance in NSCLC cells. hsa-miR-1301-3p targeted the homeodomain-only protein homeobox (HOPX) mRNA 3' untranslated region and inhibited its transcription in NSCLC cells. Exogenous HOPX overexpression antagonized the mechanism by which hsa-miR-1301-3p regulates NSCLC cell proliferation, metastasis, and apoptosis. Conclusions: hsa-miR-1301-3p plays an oncogenic role in the occurrence and development of NSCLC. By targeting HOPX, hsa-miR-1301-3p can not only promote the proliferation and metastasis of NSCLC cells, but also alleviate apoptosis and reduce radiosensitivity.

HOPX is a tumor-suppressive biomarker that corresponds to T cell infiltration in skin cutaneous melanoma

BACKGROUND

Skin cutaneous melanoma (SKCM) is the most threatening type of skin cancer. Approximately 55,000 people lose their lives every year due to SKCM, illustrating that it seriously threatens human life and health. Homeodomain-only protein homeobox (HOPX) is the smallest member of the homeodomain family and is widely expressed in a variety of tissues. HOPX is involved in regulating the homeostasis of hematopoietic stem cells and is closely related to the development of tumors such as breast cancer, nasopharyngeal carcinoma, and head and neck squamous cell carcinoma. However, its function in SKCM is unclear, and further studies are needed.

METHODS

We used the R language to construct ROC (Receiver-Operating Characteristic) curves, KM (Kaplan‒Meier) curves and nomograms based on databases such as the TCGA and GEO to analyze the diagnostic and prognostic value of HOPX in SKCM patients. Enrichment analysis, immune scoring, GSVA (Gene Set Variation Analysis), and single-cell sequencing were used to verify the association between HOPX expression and immune infiltration. In vitro experiments were performed using A375 cells for phenotypic validation. Transcriptome sequencing was performed to further analyze HOPX gene-related genes and their signaling pathways.

RESULTS

Compared to normal cells, SKCM cells had low HOPX expression (p < 0.001). Patients with high HOPX expression had a better prognosis (p < 0.01), and the marker had good diagnostic efficacy (AUC = 0.744). GO/KEGG (Gene Ontology/ Kyoto Encyclopedia of Genes and Genomes) analysis, GSVA and single-cell sequencing analysis showed that HOPX expression is associated with immune processes and high enrichment of T cells and could serve as an immune checkpoint in SKCM. Furthermore, cellular assays verified that HOPX inhibits the proliferation, migration and invasion of A375 cells and promotes apoptosis and S-phase arrest. Interestingly, tumor drug sensitivity analysis revealed that HOPX also plays an important role in reducing clinical drug resistance.

CONCLUSION

These findings suggest that HOPX is a blocker of SKCM progression that inhibits the proliferation of SKCM cells and promotes apoptosis. Furthermore, it may be a new diagnostic and prognostic indicator and a novel target for immunotherapy in SKCM patients.

HOPX: A Unique Homeodomain Protein in Development and Tumor Suppression

Simple Summary

Homeobox (HOX) genes encode homeodomain proteins that regulate a wide range of molecular pathways. The homeodomain is highly conserved and binds to DNA. One exception is homeodomain-only protein (HOPX) that lacks DNA-binding capacity. HOPX plays a crucial role in development and its functional impairment is associated with a variety of diseases, including cancer. Loss of HOPX function occurs in a wide range of cancer types, where it functions as a tumor suppressor gene. Understanding the molecular mechanisms by which HOPX regulates carcinogenesis will likely lead to the development of new therapeutic approaches.

Abstract

Homeobox genes are master regulators of morphogenesis and differentiation by acting at the top of genetic hierarchies and their deregulation is associated with a variety of human diseases. They usually contain a highly conserved sequence that codes for the homeodomain of the protein, a specialized motif with three α helices and an N-terminal arm that aids in DNA binding. However, one homeodomain protein, HOPX, is unique among its family members in that it lacks the capacity to bind DNA and instead functions by interacting with transcriptional regulators. HOPX plays crucial roles in organogenesis and is expressed in both embryonic and adult stem cells. Loss of HOPX expression is common in cancer, where it functions primarily as a tumor suppressor gene. In this review, we describe the function of HOPX in development and discuss its role in carcinogenesis.

HOPX+ injury-resistant intestinal stem cells drive epithelial recovery after severe intestinal ischemia

Intestinal ischemia is a life-threatening emergency with mortality rates of 50%-80% due to epithelial cell death and resultant barrier loss. Loss of the epithelial barrier occurs in conditions including intestinal volvulus and neonatal necrotizing enterocolitis. Survival depends on effective epithelial repair; crypt-based intestinal epithelial stem cells (ISCs) are the source of epithelial renewal in homeostasis and after injury. Two ISC populations have been described: 1) active ISC [aISC; highly proliferative; leucine-rich-repeat-containing G protein-coupled receptor 5 (LGR5⁺)-positive or sex-determining region Y-box 9 -antigen Ki67-positive (SOX9⁺Ki67⁺)] and 2) reserve ISC [rISC; less proliferative; homeodomain-only protein X positive (HOPX⁺)]. The contributions of these ISCs have been evaluated both in vivo and in vitro using a porcine model of mesenteric vascular occlusion to understand mechanisms that modulate ISC recovery responses following ischemic injury. In our previously published work, we observed that rISC conversion to an activated state was associated with decreased HOPX expression during in vitro recovery. In the present study, we wanted to evaluate the direct role of HOPX on cellular proliferation during recovery after injury. Our data demonstrated that during early in vivo recovery, injury-resistant HOPX⁺ cells maintain quiescence. Subsequent early regeneration within the intestinal crypt occurs around 2 days after injury, a period in which HOPX expression decreased. When HOPX was silenced in vitro, cellular proliferation of injured cells was promoted during recovery. This suggests that HOPX may serve a functional role in ISC-mediated regeneration after injury and could be a target to control ISC proliferation.NEW & NOTEWORTHY This paper supports that rISCs are resistant to ischemic injury and likely an important source of cellular renewal following near-complete epithelial loss. Furthermore, we have evidence that HOPX controls ISC activity state and may be a critical signaling pathway during ISC-mediated repair. Finally, we use multiple novel methods to evaluate ISCs in a translationally relevant large animal model of severe intestinal injury and provide evidence for the potential role of rISCs as therapeutic targets.

HOPX Exhibits Oncogenic Activity during Squamous Skin Carcinogenesis

Cutaneous squamous cell carcinomas (SCCs) are frequent heterogeneous tumors arising from sun-exposed regions of the skin and characterized by complex pathogenesis. HOPX is a member of the homeodomain-containing superfamily of proteins holding an atypical homeodomain unable to bind to DNA. First discovered in the heart as a regulator of cardiac development, in the skin, HOPX modulates the terminal differentiation of keratinocytes. There is a particular interest in studying HOPX in squamous skin carcinogenesis because it has the atypical structure and the functional duality as an oncogene and a tumor suppressor gene, reported in different malignancies. In this study, we analyzed the effects of HOPX knockdown and overexpression on SCC tumorigenicity in vitro and in vivo. Our data show that HOPX knockdown in SCC cells inhibits their proliferative and invasive activity through the acceleration of apoptosis. We established that methylation of two alternative HOPX promoters leads to differential expression of HOPX transcripts in normal keratinocytes and SCC cells. Importantly, we report that HOPX acts as an oncogene in the pathogenesis of SCC probably through the activation of the second alternative promoter and the modulation of apoptosis.

The role of HOPX in normal tissues and tumor progression

The homeodomain-only protein homeobox (HOPX) as the smallest homeodomain protein, lacks certain conserved residues required for DNA binding. Through our literature search, we reviewed the current understandings of HOPX in normal tissues and tumor progression. HOPX was initially identified as a critical transcription factor in various normal tissues, which interacted with serum response factor (SRF) or other substance to regulate normal physiological function. However, HOPX is at a low expression or methylation level in tumors. These data indicated that HOPX may play a very important role in regulating differentiation phenotype and tumor suppressive function. We predicted the prognosis of HOPX in tumors from TCGA database and discussed the downstream genes of HOPX. To understand how HOPX is involved in the mechanisms between physical and pathological conditions could lead to novel therapeutic strategies for treatment.

Knock-out of Hopx disrupts stemness and quiescence of hematopoietic stem cells in mice

HOPX is a stem cell marker in hair follicles and intestines. It was shown critical for primitive hematopoiesis. We previously showed an association between higher HOPX expression and clinical characteristics related to stemness and quiescence of leukemic cells in acute myeloid leukemia (AML) patients. To further explore its physiologic functions in hematopoietic system, we generated a mouse model with hematopoietic cell-specific knockout of Hopx (Hopx^-/-). In young Hopx^-/- mice, the hematopoietic stem cells (HSC) showed decreased reconstitution ability after serial transplantation. Further transcriptomic study revealed decreased HSC signatures in long-term HSCs from the Hopx^-/- mice. At 18 months of age, half of the Hopx^-/- mice developed cytopenia and splenomegaly. Bone marrow (BM) from the sick mice showed myeloid hyperplasia with predominant mature neutrophils, and decreased progenitor cells and lymphocytes. These phenotypes suggested critical functions of Hopx in maintaining HSC quiescence. Transcriptomic study of the Hopx^-/- marrow cells showed significant downregulation of the Cxcl12-Cxcr4 axis, which is critical for maintenance of HSC quiescence. We next examined the role of Hopx in AML by using the MN1 overexpression murine leukemia model. Mice transplanted with MN1-overexpressed Hopx^-/- BM cells developed AML with more aggressive phenotypes compared with those transplanted with MN1-overexpressed Hopx-wild cells. Hopx^-/- MN1-overexpressed leukemia cells showed higher proliferation rate and downregulation of Cxcl12 and Cxcr4. Furthermore, in human AML, BM plasma CXCL12 levels were lower in patients with lower HOPX expression. In conclusion, our study highlights the roles of Hopx in maintenance of quiescence of the hematopoietic stem cells through CXCL12 pathway in vivo and provides implication of this protein in normal and malignant hematopoiesis.

Epigenetic silencing of HOPX is critically involved in aggressive phenotypes and patient prognosis in papillary thyroid cancer

HOPX is involved in multiple organ development and acts as a tumor suppressor in various cancers. Epigenetic silencing of HOPX via its promoter methylation has been shown frequent and cancer-specific in human cancers. The proliferation of thyroid cancer cells and cancer progression are strongly influenced by epigenetic alterations as well as genetic changes. Papillary thyroid cancer (PTC) comprises the vast majority of thyroid cancers and exhibits slow progression. However, ~10% of patients still show disease recurrence and refractoriness to treatment. Accordingly, it is important approach to research epigenetic mechanisms in PTC progression to find useful biomarkers. Here, we aimed to seek into the roles and clinical impact of epigenetic silencing of HOPX in PTC.

The promoter methylation of HOPX was observed in five of six human thyroid cancer cell lines. Down-regulation of HOPX was seen in three cell lines including PTC line K1, and demethylating agents restored HOPX expression. The promoter methylation was observed with high sensitivity and specificity in human PTC tissues. HOPX promoter methylation independently predicted disease recurrence in PTC patients. Epigenetic silencing of HOPX was associated with Ki-67 expression. Of note, HOPX promoter methylation was dramatically associated with worse prognosis especially in patients with stage I PTC. Forced HOPX expression suppressed cell proliferation, invasive activities, and anchorage-independent growth in vitro.

HOPX promoter methylation is frequent and cancer-specific event, leading to aggressive phenotype in PTC. Epigenetic silencing of HOPX may be a clue to tackle cancer progression and have clinical impact as a novel biomarker in PTC.

ΜicroRNA‑421 promotes the progression of non‑small cell lung cancer by targeting HOPX and regulating the Wnt/β‑catenin signaling pathway

MicroRNAs (miRNAs) function as key regulators of numerous types of cancers. miRNA (miR)-421 expression is dysregulated in a variety of tumors; however, its role in non-small cell lung cancer (NSCLC) remains unclear. In the present study, the role and molecular mechanism of miR-421 in NSCLC was investigated. In this study, miRNA (miR)-421 was upregulated in NSCLC tissues and cell lines used the reverse transcriptase quantitative polymerase chain reaction. Ectopic expression of miR-421 significantly promoted cell proliferation in vitro and tumor growth in vivo by promoting cell cycle progression via CCK-8, colony formation, EdU assay, xenograft model and cell cycle assay. In addition, miR-421 inhibited NSCLC cell apoptosis by flow cytometry apoptosis assay, as evidenced by anti-apoptosis gene Bcl-2 and apoptosis gene cleaved caspase-3 and cleaved PARP using western blot assay. Furthermore, miR-421 promoted cell migration and invasion through EMT process using Transwell and western blot assay. It was also demonstrated that miR-421 can directly target HOPX by the EGFP reporter assay and western blot assay. MiR-421 overexpression promoted the protein expression levels of β-catenin, cyclin D1 and c-myc by western blot assay, which are the downstream genes of Wnt pathway. These data indicated that miR-421 may act as an oncogene through the effects of HOPX on the Wnt/β-catenin signaling pathway and may provide insight into the mechanisms underlying carcinogenesis and the identification of potential biomarkers associated with NSCLC.

Preservation of reserve intestinal epithelial stem cells following severe ischemic injury

Intestinal ischemia is an abdominal emergency with a mortality rate >50%, leading to epithelial barrier loss and subsequent sepsis. Epithelial renewal and repair after injury depend on intestinal epithelial stem cells (ISC) that reside within the crypts of Lieberkühn. Two ISC populations critical to epithelial repair have been described: 1) active ISC (aISC; highly proliferative; leucine-rich-repeat-containing G protein-coupled receptor 5 positive, sex determining region Y-box 9 positive) and 2) reserve ISC [rISC; less proliferative; homeodomain only protein X (Hopx)⁺]. Yorkshire crossbred pigs (8-10 wk old) were subjected to 1-4 h of ischemia and 1 h of reperfusion or recovery by reversible mesenteric vascular occlusion. This study was designed to evaluate whether ISC-expressing biomarkers of aISCs or rISCs show differential resistance to ischemic injury and different contributions to the subsequent repair and regenerative responses. Our data demonstrate that, following 3-4 h ischemic injury, aISC undergo apoptosis, whereas rISC are preserved. Furthermore, these rISC are retained ex vivo in spheroids in which cell populations are enriched in the rISC biomarker Hopx. These cells appear to go on to provide a proliferative pool of cells during the recovery period. Taken together, these data indicate that Hopx⁺ cells are resistant to injury and are the likely source of epithelial renewal following prolonged ischemic injury. It is therefore possible that targeting reserve stem cells will lead to new therapies for patients with severe intestinal injury. NEW & NOTEWORTHY The population of reserve less-proliferative intestinal epithelial stem cells appears resistant to injury despite severe epithelial cell loss, including that of the active stem cell population, which results from prolonged mesenteric ischemia. These cells can change to an activated state and are likely indispensable to regenerative processes. Reserve stem cell targeted therapies may improve treatment and outcome of patients with ischemic disease.

Prediction of onset of remnant gastric cancer by promoter DNA methylation of CDO1/HOPX/Reprimo/E-cadherin

Background

Early detection of remnant gastric cancer (RGC) is required to reduce the risk of death, but long-term endoscopic surveillance is difficult after gastrectomy. In this study, data for the methylation status of 4 methylation genes (CDO1, HOPX, Reprimo, and E-cadherin) to predict the onset of RGC are presented.

Results

The 4 genes showed hypermethylation in RGC tumors in contrast to the corresponding non-cancerous mucosa tissues. The methylation level in the non-cancerous mucosa tissues of the initial surgery was obviously high in initial malignant disease for CDO1 (P = 0.0001), while in initial benign one for E-cadherin (P = 0.003). Promoter DNA methylation status in the remnant non-cancerous mucosa tissues together with the basic clinical data in turn predicted either initial malignant disease or initial benign disease with a high AUC score of 0.94, suggesting that methylation events are differentially recognized between the initial malignant and benign disease. We then finally confirmed that 4 genes hypermethylation of the non-cancerous tissues by biopsy prior to onset of RGC could predict terms until RGC occurred (P < 0.0001).

Methods

A total of 58 RGC patients were used to establish the model. The 4 genes promoter methylation were analyzed for DNA obtained from the patient's specimens using quantitative methylation specific polymerase chain reaction.

Conclusions

This risk model would help provide guidance for endoscopic surveillance plan of RGC after gastrectomy.

Epigenetic biomarkers of promoter DNA methylation in the new era of cancer treatment

Promoter DNA methylation, which occurs on cytosine nucleotides across CpG islands, results in gene silencing and represents a major epigenetic alteration in human cancer. Methylation-specific PCR can amplify these modifications as markers in cancer cells. In the present work, we rigorously review the published literatures describing DNA methylation in the promoters of critical tumor suppressor genes; detection of promoter DNA methylation in various body fluids permits early detection of cancer cells during perioperative courses of clinical treatment. The latest whole-genome comprehensive explorations identified excellent epigenetic biomarkers that could be detected at high frequency with high specificity; these biomarkers, which are designated highly relevant methylation genes (HRMG), permit the discrimination of tumor tissues from the corresponding normal tissues; these markers are also associated with unique cancer phenotypes, including dismal prognosis. In humans, HRMG include the CDO1, GSHR, RASSF1 and SFRP1 genes, with these markers permitting discrimination depending on the organs tested. The combination of several HRMG increased the early detection of cancer and exhibited reliable surveillance potential in human body fluids. Cancer clinics using such epigenetic biomarkers are entering a new era of enhanced decision-making with the potential for improved cancer prognosis.

HOPX homeobox methylation in differentiated thyroid cancer and its clinical relevance

BACKGROUND

The inactivation of the tumor-suppressor homeodomain-only protein X (HOPX) usually involves promoter methylation in several cancer types. This study aimed to investigate the HOPX-β mRNA expression and promoter methylation and their clinical relevance in differentiated thyroid cancer (DTC).

PATIENTS AND METHODS

Clinicopathological data and paraffin-embedded thyroid tumor tissues from 21 patients with DTC and 6 with benign tumors (T) and their non-tumor parenchyma (NT) were investigated. Tumor cell lines (FTC238, FTC236 and WRO) were treated with demethylating agent. HOPX-β mRNA expression was assessed by qRT-PCR and methylation status by Q-MSP. Thyroid cancer data from Cancer Genome Atlas (TCGA) was also collected.

RESULTS

HOPX-β mRNA re-expression in two cell lines treated with demethylating agent was observed concomitantly with reduced promoter methylation. Reduced mRNA expression in T group compared to their NT was observed, and reduced protein expression in T compared to NT was observed in three cases. Low mRNA expression with high methylation status was detected in 6/14 DTC samples. High methylation status was associated with older age at diagnosis, recurrent or progressive disease and with the presence of new neoplasm event post initial therapy while hyper-methylation correlated with worse overall survival, worse disease-free status and older age.

CONCLUSION

A moderate coupling of downregulation of HOPX-β mRNA expression in DTC followed by high HOPX-β promoter methylation was observed however; high HOPX promoter methylation status was associated with the worse prognosis of DTC patients.

DNA diagnosis of peritoneal fluid cytology test by CDO1 promoter DNA hypermethylation in gastric cancer

BACKGROUND

Minimal residual disease of the peritoneum is challenging for early cancer detection in gastric cancer (GC). Utility of PCR amplification of cancer-derived DNA has been considered feasible due to its molecular stability, however such markers have never been available in GC clinics. We recently discovered cancer-specific methylation of CDO1 gene in GC, and investigated the clinical potential to detect the minimal residual disease.

METHODS

One hundred and two GC patients were investigated for peritoneal fluid cytology test (CY), and detection level of the promoter DNA methylation of CDO1 gene was assessed by quantitative methylation specific PCR (Q-MSP) in the sediments (DNA CY).

RESULTS

(1) CY1 was pathologically confirmed in 8 cases, while DNA CY1 was detected in 18 cases. All 8 CY1 were DNA CY1. (2) DNA CY1 was recognized in 14.3, 25.0, 20.0, and 42.9%, in macroscopic Type II, small type III, large type III, and type IV, respectively, while it was not recognized in Type 0/I/V. (3) DNA CY1 was prognostic relevance in gastric cancer (p = 0.0004), and its significance was robust among Type III/IV gastric cancer (p = 0.006 for overall survival and p = 0.0006 for peritoneal recurrence free survival). (4) The peritoneal recurrence was hardly seen in GC patients with potent perioperative chemotherapy among those with DNA CY1.

CONCLUSIONS

DNA CY1 detected by Q-MSP for CDO1 gene promoter DNA methylation has a great potential to detect minimal residual disease of the peritoneum in GC clinics as a novel DNA marker.

Higher HOPX expression is associated with distinct clinical and biological features and predicts poor prognosis in de novo acute myeloid leukemia

Homeodomain-only protein homeobox (HOPX) is the smallest homeodomain protein. It was regarded as a stem cell marker in several non-hematopoietic systems. While the prototypic homeobox genes such as the HOX family have been well characterized in acute myeloid leukemia (AML), the clinical and biological implications of HOPX in the disease remain unknown. Thus we analyzed HOPX and global gene expression patterns in 347 newly diagnosed de novo AML patients in our institute. We found that higher HOPX expression was closely associated with older age, higher platelet counts, lower white blood cell counts, lower lactate dehydrogenase levels, and mutations in RUNX1, IDH2, ASXL1, and DNMT3A, but negatively associated with acute promyelocytic leukemia, favorable karyotypes, CEBPA double mutations and NPM1 mutation. Patients with higher HOPX expression had a lower complete remission rate and shorter survival. The finding was validated in two independent cohorts. Multivariate analysis revealed that higher HOPX expression was an independent unfavorable prognostic factor irrespective of other known prognostic parameters and gene signatures derived from multiple cohorts. Gene set enrichment analysis showed higher HOPX expression was associated with both hematopoietic and leukemia stem cell signatures. While HOPX and HOX family genes showed concordant expression patterns in normal hematopoietic stem/progenitor cells, their expression patterns and associated clinical and biological features were distinctive in AML settings, demonstrating HOPX to be a unique homeobox gene. Therefore, HOPX is a distinctive homeobox gene with characteristic clinical and biological implications and its expression is a powerful predictor of prognosis in AML patients.

Promoter DNA methylation of CDO1 gene and its clinical significance in esophageal squamous cell carcinoma

We have demonstrated that CDO1 methylation is frequently found in various cancers, including esophageal squamous cell carcinoma (ESCC), but its clinical relevance has remained elusive. CDO1 methylation was investigated in 169 ESCC patients who underwent esophagectomy between 1996 and 2007. CDO1 methylation was assessed by Q-MSP (quantitative methylation specific PCR), and its clinical significance, including its relationship to prognosis, was analyzed. (i) The median TaqMeth value of CDO1 methylation was 9.4, ranging from 0 to 279.5. CDO1 methylation was significantly different between cStage I and cStage II/III (P = 0.02). (ii) On the log-rank plot, the optimal cut-off value was determined to be 8.9; ESCC patients with high CDO1 methylation showed a significantly worse prognosis than those with low CDO1 methylation (P = 0.02). (iii) A multivariate Cox proportional hazards model identified only CDO1 hypermethylation as an independent prognostic factor (HR 2.00, CI 1.09-3.78, P = 0.03). (iv) CDO1 hypermethylation stratified ESCC patients' prognosis in cStage II/III for both neoadjuvant chemo(radio)therapy (NAC)-positive and NAC-negative cases. Moreover, the CDO1 methylation level was significantly lower in cases with Grade 2/3 than in those with Grade 0/1 (P = 0.02) among cStage II/III ESCC patients with NAC. Promoter DNA hypermethylation of CDO1 could be an independent prognostic factor in ESCC; it may also reflect NAC eradication of tumor cells in the primary tumors.

HOPX hypermethylation promotes metastasis via activating SNAIL transcription in nasopharyngeal carcinoma

Nasopharyngeal carcinoma (NPC) is characterized by a high rate of local invasion and early distant metastasis. Increasing evidence indicates that epigenetic abnormalities play important roles in NPC development. However, the epigenetic mechanisms underlying NPC metastasis remain unclear. Here we investigate aberrantly methylated transcription factors in NPC tissues, and we identify the HOP homeobox HOPX as the most significantly hypermethylated gene. Consistently, we find that HOXP expression is downregulated in NPC tissues and NPC cell lines. Restoring HOPX expression suppresses metastasis and enhances chemosensitivity of NPC cells. These effects are mediated by HOPX-mediated epigenetic silencing of SNAIL transcription through the enhancement of histone H3K9 deacetylation in the SNAIL promoter. Moreover, we find that patients with high methylation levels of HOPX exhibit poor clinical outcomes in both the training and validation cohorts. In summary, HOPX acts as a tumour suppressor via the epigenetic regulation of SNAIL transcription, which provides a novel prognostic biomarker for NPC metastasis and therapeutic target for NPC treatment.

HOPX functions as a tumour suppressor in head and neck cancer

Head and neck squamous cell carcinoma (HNSCC) is generalized term that encompasses a diverse group of cancers that includes tumours of the oral cavity (OSCC), oropharynx (OPSCC) and nasopharynx (NPC). Genetic alterations that are common to all HNSCC types are likely to be important for squamous carcinogenesis. In this study, we have investigated the role of the homeodomain-only homeobox gene, HOPX, in the pathogenesis of HNSCC. We show that HOPX mRNA levels are reduced in OSCC and NPC cell lines and tissues and there is a general reduction of HOPX protein expression in these tumours and OPSCCs. HOPX promoter methylation was observed in a subset of HNSCCs and was associated with a worse overall survival in HPV negative tumours. RNAseq analysis of OSCC cells transfected with HOPX revealed a widespread deregulation of the transcription of genes related to epithelial homeostasis and ectopic over-expression of HOPX in OSCC and NPC cells inhibited cell proliferation, plating efficiency and migration, and enhanced sensitivity to UVA-induced apoptosis. Our results demonstrate that HOPX functions as a tumour suppressor in HNSCC and suggest a central role for HOPX in suppressing epithelial carcinogenesis.

Epigenetic silencing of HOPX contributes to cancer aggressiveness in breast cancer

Epigenetic silencing of HOPX has been shown to be frequent and specific in human cancers. HOPX is thought as a tumor suppressor gene and its promoter methylation is the main mechanism of down-regulation. In non-hereditary breast cancer, since roles of epigenetic modifications are more critical than in other cancers, the aim of this study is to seek into the roles and clinical relevance of epigenetic silencing of HOPX. Down-regulation of HOPX was observed in all human breast cancer cell lines tested. The promoter methylation was found in six of seven cell lines, and demethylating agents restored HOPX expression. The promoter methylation was cancer-specific in human breast tissues. Forced expression of HOPX attenuated anchorage-independent growth in vitro. HOPX promoter methylation independently predicted worse prognosis of breast cancer patients. Of note, HOPX promoter methylation was significantly associated with HER2 positivity as well as advanced lymph node metastasis. HOPX promoter methylation is not only frequent and cancer-specific but also associated with aggressive phenotype in breast cancer. Epigenetic silencing of HOPX may have clinical potential as a biomarker in the treatment strategy of breast cancer patients.

Homeobox-Only Protein Expression Is a Critical Prognostic Indicator of Pancreatic Neuroendocrine Tumor and Is Regulated by Promoter DNA Hypermethylation

OBJECTIVES

We have identified homeobox-only protein (HOPX) as a tumor suppressor gene in various human cancer, and its expression was reduced by promoter DNA hypermethylation. Homeobox-only protein is strongly expressed on pancreatic islet cells; however, clinical relevance of HOPX expression has remained elusive in pancreatic neuroendocrine tumor (pNET).

METHODS

We investigated 36 patients with pNET who undertook surgical resection between 1988 and 2012 for HOPX expression and DNA methylation to reveal its clinical significance.

RESULTS

(1) Homeobox-only protein is strongly expressed on pancreatic islet cells by immunohistochemistry (IHC). Homeobox-only protein expression was recognized on pNET tumor cells for 1+ in 15, for 2+ in 16, and for 3+ in 5. (2) Homeobox-only protein IHC expression was significantly associated with prognosis (P = 0.03), and survival rate was 37.5%, 70.3%, and 100% in HOPX 1+, 2+, and 3+, respectively. (3) Promoter DNA methylation was quantitatively assessed, and HOPX hypermethylation is found in 6.3%, 11.8%, and 66.7% of G1/G2/G3 pNET, respectively (P = 0.02). (4) Multivariate Cox proportional hazards model identified HOPX IHC expression and HOPX promoter DNA hypermethylation as independent prognostic factors in pNET.

CONCLUSIONS

Homeobox-only protein expression is a critical prognostic indicator of pNET, and its regulation may be made through promoter DNA methylation.

HOPX: The Unusual Homeodomain-Containing Protein

The homeodomain-only protein homeobox (HOPX) is the smallest known member of the homeodomain-containing protein family, atypically unable to bind DNA. HOPX is widely expressed in diverse tissues, where it is critically involved in the regulation of proliferation and differentiation. In human skin, HOPX controls epidermal formation through the regulation of late differentiation markers, and HOPX expression correlates with the level of differentiation in cutaneous pathologies. In mouse skin, Hopx was additionally identified as a lineage tracing marker of quiescent hair follicle stem cells. This review discusses current knowledge of HOPX structure and function in normal and pathological conditions.

Serum Response Factor Protects Retinal Ganglion Cells Against High-Glucose Damage

Serum response factor (SRF), which encodes the MADS-box family of related proteins, is a common transcription factor related to the expression of genes associated with cell survival. However, SRF's role in retinal ganglion cells (RGCs) after high-glucose injury remains unclear. In this study, we investigate the protective role of SRF after high-glucose injury and its underlying mechanism. The in vitro RGC model subjected to high glucose was established by employing a 50 mmol/L glucose culture environment. As detected by real-time quantitative PCR and Western blot, SRF was significantly upregulated in RGCs treated with high glucose. Overexpression of SRF significantly promoted survival among RGCs exposed to high glucose and inhibited RGC apoptosis. Knockdown of SRF exerted an inverse effect. Moreover, SRF upregulation enhanced expression of an antioxidant protein, nuclear factor erythroid 2-related factor (Nrf2), via control of the Fos-related antigen 1 (Fra-1). SRF upregulation also affected RGC survival after high-glucose treatment. Our findings showed that overexpression of SRF promoted survival of RGCs after high-glucose injury by regulating Fra-1 and Nrf2.

Exclusive Association of p53 Mutation with Super-High Methylation of Tumor Suppressor Genes in the p53 Pathway in a Unique Gastric Cancer Phenotype

Background

A comprehensive search for DNA methylated genes identified candidate tumor suppressor genes that have been proven to be involved in the apoptotic process of the p53 pathway. In this study, we investigated p53 mutation in relation to such epigenetic alteration in primary gastric cancer.

Methods

The methylation profiles of the 3 genes: PGP9.5, NMDAR2B, and CCNA1, which are involved in the p53 tumor suppressor pathway in combination with p53 mutation were examined in 163 primary gastric cancers. The effect of epigenetic reversion in combination with chemotherapeutic drugs on apoptosis was also assessed according to the tumor p53 mutation status.

Results

p53 gene mutations were found in 44 primary gastric tumors (27%), and super-high methylation of any of the 3 genes was only found in cases with wild type p53. Higher p53 pathway aberration was found in cases with male gender (p = 0.003), intestinal type (p = 0.005), and non-infiltrating type (p = 0.001). The p53 pathway aberration group exhibited less recurrence in lymph nodes, distant organs, and peritoneum than the p53 non-aberration group. In the NUGC4 gastric cancer cell line (p53 wild type), epigenetic treatment augmented apoptosis by chemotherapeutic drugs, partially through p53 transcription activity. On the other hand, in the KATO III cancer cell line (p53 mutant), epigenetic treatment alone induced robust apoptosis, with no trans-activation of p53.

Conclusion

In gastric cancer, p53 relevant and non-relevant pathways exist, and tumors with either pathway type exhibited unique clinical features. Epigenetic treatments can induce apoptosis partially through p53 activation, however their apoptotic effects may be explained largely by mechanism other than through p53 pathways.

Lineage factors and differentiation states in lung cancer progression

Lung cancer encompasses a heterogeneous group of malignancies. Here we discuss how the remarkable diversity of major lung cancer subtypes is manifested in their transforming cell of origin, oncogenic dependencies, phenotypic plasticity, metastatic competence and response to therapy. More specifically, we review the increasing evidence that links this biological heterogeneity to the deregulation of cell lineage-specific pathways and the transcription factors that ultimately control them. As determinants of pulmonary epithelial differentiation, these poorly characterized transcriptional networks may underlie the etiology and biological progression of distinct lung cancers, while providing insight into innovative therapeutic strategies.

Identification of EGFR expression status association with metastatic lymph node density (ND) by expression microarray analysis of advanced gastric cancer

Metastatic lymph node density (ND) has been reproducibly proven to be a prognostic factor in gastric cancer. The molecular mechanisms that underlie this aggressiveness are underexplored. Here, we aimed to identify molecules associated with this unique phenotype. Tumor specimens from patients with stage III gastric cancer with high or low ND (n = 4 for both) were compared at the mRNA level using Affymetrix microarray (harboring 54,675 genes). The expression data were prioritized, and genes that correlated with ND were selected. Ultimately, the EGFR was validated as such a candidate molecule in patients with primary advanced gastric cancer who underwent standard treatment (n = 167). Expression data of the microarray were prioritized based on gene expression ratio and frequency of gene expression. The first priority genes to be selected were genes that are known to be amplified in cancer, which included NKX2.1, CHST9, CTNND2, SLC25A27, FGFR2, EGFR, and PTGER1. Of these genes, the EGFR gene was of particular interest. EGFR expression in primary gastric cancer was examined using immunohistochemistry (IHC). The Student's t-test elucidated a significant difference in EGFR expression between IHC 2+/3+ and IHC 1+ according to ND (P = 0.0035). The Chi-square test also indicated a significant difference between high and low levels of EGFR immunohistochemical staining (IHC2+/3+ and IHC1+, respectively) and ND status (P = 0.0023). According to the least squares method, as ND increased, the risk that EGFR staining levels changed from IHC 1+ to IHC 2+ also increased. In this study, we determined that high EGFR expression may underlie the aggressive mechanism of advanced gastric cancer with high ND.

The homeobox only protein homeobox (HOPX) and colorectal cancer

The HOP (homeobox only protein) homeobox (HOPX) is most closely related to the homeobox protein that contains a homeobox-like domain but lacks certain conserved residues required for DNA binding. Here, we review the current understanding of HOPX in the progression of colorectal cancer (CRC). HOPX was initially reported as a differentiation marker and is expressed in various normal tissues. In the colon, HOPX is expressed uniquely in the quiescent stem cell, +4, and in differentiated mucosal cells of the colon. HOPX expression is markedly suppressed in a subset of cancers, mainly in an epigenetic manner. CRC may include separate entities which are differentially characterized by HOPX expression from a prognostic point of view. HOPX itself can regulate epigenetics, and defective expression of HOPX can result in loss of tumor suppressive function and differentiation phenotype. These findings indicate that HOPX may be both a central regulator of epigenetic dynamics and a critical determinant for differentiation in human cells. HOPX downstream targets were identified in CRC cell lines and hold promise as candidates for therapeutic targets of CRC, such as EphA2 or AP-1. Further analysis will elucidate and confirm the precise role of such proteins in CRC progression.

Epigenetic silencing of HOPX promotes cancer progression in colorectal cancer

Homeodomain-only protein X (HOPX)-β promoter methylation was recently shown to be frequent in human cancers and was suggested as tumor suppressor gene in esophageal and gastric cancer. The aim of this study was to investigate the mechanistic roles of HOPX-β promoter methylation and its clinical relevance in colorectal cancer (CRC). HOPX-β promoter methylation was assessed in human CRC cell lines and 294 CRC tissues. HOPX mRNA and protein levels were measured in relation to HOPX-β promoter methylation. The effects of forced HOPX expression on tumorigenesis were studied using in vitro and in vivo assays. The association between HOPX-β promoter methylation and clinical relevance of CRC patients was determined. HOPX-β promoter methylation is cancer-specific and frequently found in CRC cell lines and tissues, resulting in the down-regulation of HOPX mRNA and protein levels. In CRC cell lines, forced expression of HOPX suppressed proliferation, invasion, and anchorage-independent growth. DNA microarray analyses suggested critical downstream genes that are associated with cancer cell proliferation, invasion or angiogenesis. In a mouse xenograft model, HOPX inhibited tumorigenesis and angiogenesis. Finally, HOPX-β promoter methylation was associated with worse prognosis of stage III CRC patients (hazard ratio= 1.40, P = .035) and also with poor differentiation (P = .014). In conclusion, HOPX-β promoter methylation is a frequent and cancer-specific event in CRC progression. This epigenetic alteration may have clinical ramifications in the diagnosis and treatment of CRC patients.

Cancer specific promoter CpG Islands hypermethylation of HOP homeobox (HOPX) gene and its potential tumor suppressive role in pancreatic carcinogenesis

Background

We have recently identified HOP hoemobox (HOPX) as a tumor suppressor gene candidate, characterized by tumor-specific promoter DNA hypermethylation in human cancers, and it can remarkably inhibit tumors’ aggressive phenotypes. In this current study, we for the first time examined methylation level of HOPX and tested the functional relevance in pancreatic cancer (PC).

Methods

Clinical features of HOPX promoter hypermethylation was investigated in 89 PC tissues, and immunohistochemistry was added. We also examined its functional relevance in phenotype assays such as soft agar, proliferation, invasion, and cell cycle analysis.

Results

PC tissues had HOPX gene hypermethylation as compared to the corresponding normal pancreas tissues, and its uniqueness was robust to discriminate tumor from normal tissues (AUC = 0.85, P < 0.0001). Unexpectedly, HOPX was increased in expression in tumor tissues, and immunohistochemistry revealed its predominant expression in the Langerhans islet cells, where HOPX was reduced in expression for PC cells with promoter hypermethylation. HOPX transfectants exhibited G1 arrest with subG1 accumulation, and inhibited tumor forming and invasive ability.

Conclusion

Defective expression of HOPX which is consistent with promoter DNA hypermethylation may explain aggressive phenotype of pancreatic cancer, and intense expression of HOPX in the Langerhans cells may in turn uniquely contribute to pancreatic carcinogenesis.

Promoter methylation of tumor suppressor genes in esophageal squamous cell carcinoma

Esophageal squamous cell carcinoma (ESCC) is a prevalent and fatal cancer in China and other Asian countries. Epigenetic silencing of key tumor suppressor genes (TSGs) is critical to ESCC initiation and progression. Recently, many novel TSGs silenced by promoter methylation have been identified in ESCC, and these genes further serve as potential tumor markers for high-risk group stratification, early detection, and prognosis prediction. This review summarizes recent discoveries on aberrant promoter methylation of TSGs in ESCC, providing better understanding of the role of disrupted epigenetic regulation in tumorigenesis and insight into diagnostic and prognostic biomarkers for this malignancy.

Cigarette smoke induces promoter methylation of single-stranded DNA-binding protein 2 in human esophageal squamous cell carcinoma

Esophageal squamous cell carcinoma (ESCC) is the sixth most frequent cause of cancer death in the world, and cigarette smoke is a key factor in esophageal carcinogenesis. To identify molecular changes during cigarette smoke-induced ESCC, we examined the methylation status of 13 gene promoters in the human immortalized, nontumorigenic esophageal epithelial cell line (Het-1A) that were exposed to mainstream (MSE) or sidestream cigarette smoke extract (SSE) for 6 months in culture. The promoter of sequence-specific single-stranded DNA-binding protein 2 (SSBP2) was methylated in the Het-1A cells exposed to MSE (MSE-Het-1A). Promoter methylation (86%, 56/70) and downregulation of SSBP2 expression were frequently detected in tumor tissues from ESCC patients. In addition, reintroduction of SSBP2 in an ESCC cell line (TE1) that does not express SSBP2 and in the MSE-Het-1A cells inhibited expression of LRP6 and Dvl3, which are mediators of the Wnt signaling pathway. SSBP2 expression markedly decreased the colony-forming ability of ESCC cell lines and significantly inhibited cell growth of the MSE-Het-1A cells. Our results indicate that cigarette smoking is a cause of SSBP2 promoter methylation and that SSBP2 harbors a tumor suppressive role in ESCC through inhibition of the Wnt signaling pathway.

Promoter methylation of heat shock protein B2 in human esophageal squamous cell carcinoma

Hypermethylation of gene promoters and the corresponding loss of gene expression are recognized as a hallmark of human cancer, and DNA methylation has emerged as a promising biomarker for the detection of human esophageal squamous cell carcinoma (ESCC). To identify novel genes methylated in ESCC, we screened 35 candidate genes identified from an oligonucleotide microarray. Among them, the heat shock protein B2 (HSPB2) was methylated in 95.7% (67/70) of primary ESCCs, whereas no methylation was found in normal esophageal tissues from ESCC patients (0%, 0/20). RT-PCR analysis revealed that HSPB2 expression was silenced or weakly expressed in most ESCC cell lines, and re-activated by the demethylating agent 5-aza-2'-deoxy-cytidine. These results indicate that promoter methylation of HSPB2 is one of the causal factors for loss or down-regulation of HSPB2 expression. mRNA expression of HSPB2 in ESCC tissues was significantly down-regulated compared to normal tissues. Our data suggest that promoter methylation of HSPB2 deserves further attention as a novel molecular biomarker in human ESCC.

Potential utility of HOP homeobox gene promoter methylation as a marker of tumor aggressiveness in gastric cancer

HOP homeobox (HOPX) is an unusual homeobox gene encoding three spliced transcript variants, among which the only HOPX-beta promoter harbors CpG islands. The characteristics of its promoter methylation was analyzed using bisulfite sequencing and quantitative-methylation-specific polymerase chain reaction (Q-MSP), and the effects of HOPX expression were also examined. HOPX-beta expression was silenced in all gastric cancer cell lines tested; its expression could be restored by treatment with demethylating agent. On Q-MSP, HOPX-beta hypermethylation (cut-off value of 3.55) was found in 84% (67 out of 80) of primary tumor tissues and 10% (8 out of 80) of the corresponding normal tissues and could discriminate normal from tumor tissues (P<0.0001). The prognosis of the advanced cases with HOPX-beta hypermethylation was as poor as those with stage IV disease when cut-off value was set at 11.28. This finding was validated in an independent cohort of 90 advanced gastric cancers. The HOPX-beta hypermethylation was also an independent prognostic factor (P=0.029) on multivariate analysis. Exogenous HOPX expression significantly inhibited cell proliferation, colony formation and invasion as well as enhanced apoptosis. Taken together, HOPX-beta promoter methylation is a frequent and cancer-specific event in gastric cancer. Quantitative assessment of HOPX-beta methylation has great clinical potential as a marker of tumor aggressiveness.

Expression of the homeobox gene, HOPX, is modulated by cell differentiation in human keratinocytes and is involved in the expression of differentiation markers

Homeodomain only protein X (HOPX), an unusual homeodomain protein, was originally identified as a key regulator of cardiac development. We first demonstrated that the expression of HOPX was dependent on the differentiation of human keratinocytes and has an effect on the expression of differentiation markers. HOPX was suppressed in proliferating human keratinocytes and was gradually induced by calcium-triggered differentiation of human keratinocytes. In the epidermis, HOPX is highly expressed in the terminally differentiated suprabasal layers. Among the transcript variants of HOPX, the variant 3 driven by promoter A was the main transcript and it was regulated by cell differentiation in human keratinocytes. The expression of HOPX was induced through the phorbol-12-myristate-13-acetate (PMA)-dependent protein kinase C (PKC) signaling pathway, and not by the demethylating agent, 5-aza-dC (5-aza-2'-deoxycitidine) suggesting the suppression of HOPX is not associated with DNA methylation in human keratinocytes. The RNA interference (RNAi) silencing experiment showed that the knockdown of HOPX expression resulted in the increase of such differentiation markers as involucrin and loricrin. Exogenous expression of HOPX down-regulated the expression of differentiation marker genes in immortalized human keratinocytes (HaCaT). Collectively, HOPX is modulated by cell differentiation in human keratinocytes and this might contribute to homeostasis of keratinocytes by controlling differentiation-dependent genes.

Homeobox gene HOPX is epigenetically silenced in human uterine endometrial cancer and suppresses estrogen-stimulated proliferation of cancer cells by inhibiting serum response factor

HOPX (homeodomain only protein X) is a newly identified homeobox gene whose loss of expression has been reported for several types of neoplasm. Although we found most human uterine endometrial cancers (HEC) defective in HOPX expression, genetic mutations in the HOPX gene were undetectable. As is the case with several tumor suppressor genes, the promoter region of HOPX is densely methylated in HEC tissue samples obtained by laser capture microdissection. HOPX mRNA and protein levels were reduced in the majority of samples, and this correlated with hypermethylation of the HOPX promoter. Forced expression of HOPX resulted in a partial block in cell proliferation, in vivo tumorigenicity and c-fos gene expression in HEC and MCF7 cells in response to 17beta-estradiol (E(2)) stimulation. Analysis of the serum response element (SRE) of c-fos gene promoter showed that the effect of HOPX expression is associated with inhibition of E(2)-induced c-fos activation through the serum response factor (SRF) motif. Knockdown of HOPX in immortalized human endometrial cells resulted in accelerated proliferation. Our study indicates that transcriptional silencing of HOPX results from hypermethylation of the HOPpromoter, which leads to HEC development.