Decreased PITX1 homeobox gene expression in human lung cancer

PITX1 plays essential functions in cancer

PITX1, also known as the pituitary homeobox 1 gene, has emerged as a key regulator in animal growth and development, attracting significant research attention. Recent investigations have revealed the implication of dysregulated PITX1 expression in tumorigenesis, highlighting its involvement in cancer development. Notably, PITX1 interacts with p53 and exerts control over crucial cellular processes including cell cycle progression, apoptosis, and chemotherapy resistance. Its influence extends to various tumors, such as esophageal, colorectal, gastric, and liver cancer, contributing to tumor progression and metastasis. Despite its significance, a comprehensive review examining PITX1's role in oncology remains lacking. This review aims to address this gap by providing a comprehensive overview of PITX1 in different cancer types, with a particular focus on its clinicopathological significance.

Homeobox Gene Expression Dysregulation as Potential Diagnostic and Prognostic Biomarkers in Bladder Cancer

Homeobox genes serve as master regulatory transcription factors that regulate gene expression during embryogenesis. A homeobox gene may have either tumor-promoting or tumor-suppressive properties depending on the specific organ or cell lineage where it is expressed. The dysregulation of homeobox genes has been reported in various human cancers, including bladder cancer. The dysregulated expression of homeobox genes has been associated with bladder cancer clinical outcomes. Although bladder cancer has high risk of tumor recurrence and progression, it is highly challenging for clinicians to accurately predict the risk of tumor recurrence and progression at the initial point of diagnosis. Cystoscopy is the routine surveillance method used to detect tumor recurrence. However, the procedure causes significant discomfort and pain that results in poor surveillance follow-up amongst patients. Therefore, the development of reliable non-invasive biomarkers for the early detection and monitoring of bladder cancer is crucial. This review provides a comprehensive overview of the diagnostic and prognostic potential of homeobox gene expression dysregulation in bladder cancer.

The expression and methylation of PITX genes is associated with the prognosis of head and neck squamous cell carcinoma

Background: The PITX gene family, comprising PITX1, PITX2, and PITX3, is critical in organogenesis and has been evolutionary conserved in animals. PITX genes are associated with the advanced progression and poor prognosis of multiple cancers. However, the relationship between the PITX genes and head and neck squamous cell carcinoma (HNSC) has not been reported.

Methods: We used data from The Cancer Genome Atlas (TCGA) to analyze the association between PITX mRNA expression and clinicopathological parameters of patients with HNSC. The prognostic value of PITX genes was evaluated using the Kaplan-Meier plotter. Multivariate Cox analysis was used to screen out prognosis-associated genes to identify better prognostic indicators. The potential roles of PITX1 and PITX2 in HNSC prognosis were investigated using the protein-protein interaction (PPI) network, Gene Ontology (GO) analysis, and the Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis. The correlation between PITX1 and PITX2 expression or methylation and immune cell infiltration was evaluated using the tumor-immune system interaction database (TISIDB). MethSurv was used to identify DNA methylation and its effect on HNSC prognosis.

Results:PITX genes expression was correlated with different cancers. PITX1 and PITX2 expression was lower in the patients with HNSC. In HNSC, PITX1 expression was significantly related to the clinical stage, histologic grade, and N stage, while PITX2 expression was only significantly related to the histologic grade. The high expression of PITX3 was significantly related to the histologic grade, T stage, and N stage. Survival analysis revealed that PITX genes had prognostic value in HNSC, which was supported by multivariate Cox analysis. PPI network and enrichment analysis showed that the genes interacting with PITX1 and PITX2 belonged predominantly to signaling pathways associated with DNA binding and transcription. Of the CpG DNA methylation sites in PITX1 and PITX2, 28 and 22 were related to the prognosis of HNSC, respectively. Additionally, PITX1 and PITX2 expression and methylation was associated with tumor-infiltrating lymphocytes (TILs).

Conclusion: The PITX genes were differentially expressed in patients with HNSC, highlighting their essential role in DNA methylation and tumor-infiltrating immune cell regulation, as well as overall prognostic value in HNSC.

Transcription factor CDX2 up-regulates proto-oncogenic miR-744 via a promoter activation mechanism in non-small-cell lung cancer

Background

The role of caudal-related homeobox 2 (CDX2) in the pathogenesis of non-small cell lung cancer (NSCLC) is unclear. The purpose of this study was to investigate the mRNA (message RNA) expression of CDX2 in NSCLC, and to determine its relationship with miR-744 (microRNA744) and its potential as a biomarker of NSCLC.

Methods

MiR-744 is overexpressed in A549, H460, and H1299 cell lines. Real-time quantitative polymerase chain reaction (qRT-PCR) was used to detect the mRNA expression. A chromatin immunoprecipitation (ChIP) essay was performed to determine the CDX2 binding sites. We then conducted a luciferase reporter essay to analyze interaction between MiR-744 and 3'UTRs (the 3' untranslated sequences). The migration and Boyden chamber method were used to study cell mobility.

Results

In this study, we found that ectopic CDX2 increased the expression of miR-744, while the attenuation of CDX2 reduced the expression of miR-744 by qRT-PCR. Chromatin immunoprecipitation experiments confirmed that CDX2 directly binds to the promoter of miR-744. The luciferase reporter assay further verified the binding sites of −347 to −358 bp in the most likely promoter like sequence of miR-744. CDX2-induced up-regulation of miR-744 can significantly promote the migration and invasion of NSCLC cells, while overexpression CDX2 is sufficient to rescue the migration and invasion capacity of these cells following knockdown of miR-744.

Conclusions

In summary, our results confirmed for the first time the regulatory mechanism of CDX2 on miR-744 transcription and provided a potential mechanism for CDX2 as an oncogene in lung cancer.

PITX1 inhibits the growth and proliferation of melanoma cells through regulation of SOX family genes

Melanoma is one of the most aggressive types of cancer wherein resistance to treatment prevails. Therefore, it is important to discover novel molecular targets of melanoma progression as potential treatments. Here we show that paired-like homeodomain transcription factor 1 (PITX1) plays a crucial role in the inhibition of melanoma progression through regulation of SRY-box transcription factors (SOX) gene family mRNA transcription. Overexpression of PITX1 in melanoma cell lines resulted in a reduction in cell proliferation and an increase in apoptosis. Additionally, analysis of protein levels revealed an antagonistic cross-regulation between SOX9 and SOX10. Interestingly, PITX1 binds to the SOX9 promoter region as a positive regulatory transcription factor; PITX1 mRNA expression levels were positively correlated with SOX9 expression, and negatively correlated with SOX10 expression in melanoma tissues. Furthermore, transcription of the long noncoding RNA (lncRNA), survival-associated mitochondrial melanoma-specific oncogenic noncoding RNA (SAMMSON), was decreased in PITX1-overexpressing cells. Taken together, the findings in this study indicate that PITX1 may act as a negative regulatory factor in the development and progression of melanoma via direct targeting of the SOX signaling.

Development of a novel prognostic signature for predicting the overall survival of bladder cancer patients

Background: Bladder cancer is one of the most common malignancies. So far, no effective biomarker for bladder cancer prognosis has been identified. Aberrant DNA methylation is frequently observed in the bladder cancer and holds considerable promise as a biomarker for predicting the overall survival (OS) of patients. Materials and methods: We downloaded the DNA methylation and transcriptome data for bladder cancer from The Cancer Genome Atlas (TCGA), a public database, screened hypo-methylated and up-regulated genes, similarly, hyper-methylation with low expression genes, then retrieved the relevant methylation sites. Cox regression analysis was used to identify a nine-methylation site signature of a training group. Predictive ability was validated in a test group by receiver operating characteristic (ROC) analysis. Results: We identified nine bladder cancer-specific methylation sites as potential prognostic biomarkers and established a risk score system based on the methylation site signature to evaluate the OS. The performance of the signature was accurate, with area under curve was 0.73 in the training group and 0.71 in the test group. Taking clinical features into consideration, we constructed a nomogram consisting of the nine-methylation site signature and patients’ clinical variables, and found that the signature was an independent risk factor. Conclusions: Overall, the significant nine methylation sites could be novel prediction biomarkers, which could aid in treatment and also predict the overall survival likelihoods of bladder cancer patients.

The PITX gene family as potential biomarkers and therapeutic targets in lung adenocarcinoma

ABSTRACT

The PITX gene family of transcription factors have been reported to regulate the development of multiple organs. This study was designed to investigate the role of PITXs in lung adenocarcinoma (LUAD).In this study, the transcriptional levels of the 3 identified PITXs in patients with LUAD were examined using the gene expression profiling interactive analysis interactive web server. Meanwhile, the immunohistochemical data of the 3 PITXs were obtained in the Human Protein Atlas website, and western blotting was additionally conducted for further verification. Moreover, the association between the levels of PITXs and the stage plot as well as overall survival of patients with LUAD was analyzed.We found that the mRNA and protein levels of PITX1 and PITX2 were higher in LUAD tissues than those in normal lung tissues, while those of PITX3 displayed no significant differences. Additionally, PITX1 and PITX3 were found to be significantly associated with the stage of LUAD. The Kaplan-Meier Plot showed that the high level of PITX1 conferred a better overall survival of patients with LUAD while the high level of PITX3 was associated with poor prognosis.Our study implied that PITX1 and PITX3 are potential targets of precision therapy for patients with LUAD while PITX1 and PITX2 are regarded as novel biomarkers for the diagnosis of LUAD.

Bioinformatics analysis of prognostic value of PITX1 gene in breast cancer

BACKGROUND

Paired-like homeodomain transcription factor 1 (PITX1) participates in miscellaneous biological processes including cell growth, development, progression and invasion in various malignant tumors. However, the analysis of the association between PITX1 expression and the survival in breast cancer remains unclear.

METHODS

Clinical prognostic parameters and survival data related to PITX1 in breast cancer patients were performed using the bioinformatic analysis including Oncomine, Bc-GenExMiner v4.3, PrognoScan and UCSC Xena.

RESULTS

We found that PITX1 gene expression was significantly higher in different histological classification of breast cancer. The Scarff-Bloom-Richardson (SBR) grade, Nottingham prognostic index (NPI), estrogen receptor (ER) negative, epidermal growth factor receptor-2 (HER2) positive, lymph node positive, triple-negative status and basal-like status were positively correlated with PITX1 level, except for patients' age and the progesterone receptor (PR) status. We have found that the increased PITX1 expression correlated with worse relapse-free survival, disease specific survival and overall survival. PITX1 was positively correlated with metastatic relapse-free survival and distant metastasis-free survival. We also confirmed positive correlation between PITX1 and the nucleotide-binding oligomerization domain 2 (NOD2).

CONCLUSION

The lower expression of PITX1 was associated with better clinical prognostic parameters and clinical survival in breast cancer according to the bioinformatic analysis.

Paired like homeodomain 1 and SAM and SH3 domain-containing 1 in the progression and prognosis of head and neck squamous cell carcinoma

Head and neck squamous cell carcinoma (HNSCC) is an aggressive malignancy with high morbidity and mortality rates. In spite of numerous advancements have been made in therapeutic methods, the prognosis of HNSCC patients remains poor. Therefore, investigation of crucial genes during HNSCC tumorigenesis which could be exploited as biomarkers and therapeutic targets is greatly needed. In this study, original data of four independent datasets was downloaded from the Gene Expression Omnibus database and analyzed through R language to screen out differentially expressed genes. Paired like homeodomain 1 and SAM and SH3 domain-containing 1 were selected to be further explored through multiple online databases. Quantitative real-time polymerase chain reaction analysis and immunohistochemistry assay were adopted to validate the downregulation of paired like homeodomain 1 and SAM and SH3 domain-containing 1 in HNSCC and statistical analysis indicated their close associations with patient prognosis. In vitro experiments demonstrated the inhibitory effect of paired like homeodomain 1 and SAM and SH3 domain-containing 1 on HNSCC progression. Overall, we identified the aberrant downregulation of paired like homeodomain 1 and SAM and SH3 domain-containing 1 in HNSCC and suggested the potential of utilizing them as therapeutic targets or efficient biomarkers for diagnosis and prognosis evaluation. Our findings may provide novel evidences for the development of new strategies for HNSCC treatment.

Identifying Cell-Type Specific Genes and Expression Rules Based on Single-Cell Transcriptomic Atlas Data

Single-cell sequencing technologies have emerged to address new and longstanding biological and biomedical questions. Previous studies focused on the analysis of bulk tissue samples composed of millions of cells. However, the genomes within the cells of an individual multicellular organism are not always the same. In this study, we aimed to identify the crucial and characteristically expressed genes that may play functional roles in tissue development and organogenesis, by analyzing a single-cell transcriptomic atlas of mice. We identified the most relevant gene features and decision rules classifying 18 cell categories, providing a list of genes that may perform important functions in the process of tissue development because of their tissue-specific expression patterns. These genes may serve as biomarkers to identify the origin of unknown cell subgroups so as to recognize specific cell stages/states during the dynamic process, and also be applied as potential therapy targets for developmental disorders.

PITX1 protein interacts with ZCCHC10 to regulate hTERT mRNA transcription

Telomerase is a ribonucleoprotein ribonucleic enzyme that is essential for cellular immortalization via elongation of telomere repeat sequences at the end of chromosomes. Human telomerase reverse transcriptase (hTERT), the catalytic subunit of telomerase holoenzyme, is a key regulator of telomerase activity. Telomerase activity, which has been detected in the majority of cancer cells, is accompanied by hTERT expression, suggesting that this enzyme activity contributes to an unlimited replication potential of cancer cells via regulation of telomere length. Thus, hTERT is an attractive target for cancer-specific treatments. We previously reported that pared-like homeodomain 1 (PITX1) is a negative regulator of hTERT through direct binding to the hTERT promoter. However, the mechanism by which the function of PITX1 contributes to transcriptional silencing of the hTERT gene remains to be clarified. Here, we show that PITX1 and zinc finger CCHC-type containing 10 (ZCCHC10) proteins cooperate to facilitate the transcriptional regulation of the hTERT gene by functional studies via FLAG pull-down assay. Co-expression of PITX1 and ZCCHC10 resulted in inhibition of hTERT transcription, in melanoma cell lines, whereas mutate-deletion of homeodomain in PITX1 that interact with ZCCHC10 did not induce similar phenotypes. In addition, ZCCHC10 expression levels showed marked decrease in the majority of melanoma cell lines and tissues. Taken together, these results suggest that ZCCHC10-PITX1 complex is the functional unit that suppresses hTERT transcription, and may play a crucial role as a novel tumor suppressor complex.

Silenced PITX1 promotes chemotherapeutic resistance to 5-fluorocytosine and cisplatin in gastric cancer cells

Resistance to chemotherapeutic drugs leads to a poor prognosis in gastric cancer (GC). The present study aimed to assess the association between pituitary homeobox paired homeodomain transcription 1 (PITX1) expression and the sensitivity of GC cells to the chemotherapeutic drugs 5-fluorouracil (5-FU) and cisplatin (CDDP). In the present study, the gastric cancer cell lines GES-1, AGS, BGC-823, MCG-803 and SGC-7901 were used. The expression of PITX1 was determined via reverse transcription-quantitative polymerase chain reaction in GC cell lines. AGS and BGC-823 cells, which exhibit a decreased PITX1 expression, were transfected with a PITX1 cDNA construct and its control vector. MCG-803 and SGC-7901 cells, which exhibit an increased PITX1 expression, were transfected with siRNA against PITX1 and its control scramble sequence. A Cell Counting kit-8 assay was performed to determine the impact of PITX1 expression on the sensitivity of GC cells to 5-FU and CDDP. The Cancer Genome Atlas database was used to analyze the expression of PITX1 with GC prognosis in the Asian population and to assess the potential mechanism of PITX1 in 5-FU and CDDP resistance. The results revealed that the overexpression of PIXT1 increased the sensitivity of GC cells to 5-FU/CDDP. The combination of 5-FU/CDDP and PITX1 overexpression also reduced the proliferation of GC cells. Additionally, PIXT1 knockdown decreased the sensitivity of GC cells to 5-FU/CDDP. TCGA data revealed that a lower expression of PITX1 is exhibited in Asian GC patients than in normal individuals. GC patients with a lower expression of PITX1 had a poor prognosis. The expression of PITX1 affected the sensitivity of GC cells to 5-FU/CDDP, indicating that PITX1 may increase the efficacy of treatment in GC patients.

De Novo PITX1 Expression Controls Bi-Stable Transcriptional Circuits to Govern Self-Renewal and Differentiation in Squamous Cell Carcinoma

Basal tumor propagating cells (TPCs) control squamous cell carcinoma (SCC) growth by self-renewing and differentiating into supra-basal SCC cells, which lack proliferative potential. While transcription factors such as SOX2 and KLF4 can drive these behaviors, their molecular roles and regulatory interactions with each other have remained elusive. Here, we show that PITX1 is specifically expressed in TPCs, where it co-localizes with SOX2 and TRP63 and determines cell fate in mouse and human SCC. Combining gene targeting with chromatin immunoprecipitation sequencing (ChIP-seq) and transcriptomic analyses reveals that PITX1 cooperates with SOX2 and TRP63 to sustain an SCC-specific transcriptional feed-forward circuit that maintains TPC-renewal, while inhibiting KLF4 expression and preventing KLF4-dependent differentiation. Conversely, KLF4 represses PITX1, SOX2, and TRP63 expression to prevent TPC expansion. This bi-stable, multi-input network reveals a molecular framework that explains self-renewal, aberrant differentiation, and SCC growth in mice and humans, providing clues for developing differentiation-inducing therapeutic strategies.

Abnormal PITX1 gene methylation in adolescent idiopathic scoliosis: a pilot study

Background

The gene of pituitary homeobox 1 (PITX1) has been reported to be down-regulated in adolescent idiopathic scoliosis (AIS), of which the cause has not been well addressed. The abnormal DNA methylation was recently assumed to be an important mechanism for the down-regulated genes expression. However, the association between PITX1 promoter methylation and the etiology of AIS was not clear.

Methods

The peripheral blood samples of 50 AIS patients and 50 healthy controls were collected and the genomic DNA was extracted. The pyrosequencing assay was used to assess the methylation status of PITX1 promoter and real-time quantitative polymerase chain reaction (PCR) was used to detect the PITX1 gene expression. Comparison analysis was performed using independent t test and Chi-square tests, while correlation analysis were performed with 2-tailed Pearson coefficients.

Results

The mean methylation level was (3.52 ± 0.96)% in AIS and (1.40 ± 0.81)% in healthy controls (P < 0.0001). The PITX1 gene expression was 0.15 ± 0.08 in AIS and 0.80 ± 0.55 in healthy controls (P < 0.0001). The comparative analysis showed significant difference in age (P = 0.021) and Cobb angle of the main curve (P = 0.0001) between AIS groups with positive and negative methylation. The methylation level of 6 CpG sites in PITX1 promoters was significantly associated with Cobb angle of the main curve (P < 0.001) in AIS. No statistical relationship between PITX1 promoter methylation and gene expression was found in AIS (P = 0.842).

Conclusion

Significantly higher methylation level and lower PITX1 gene expression are found in AIS patients. PITX1 methylation is associated with Cobb angles of the main curves in AIS. DNA methylation thus plays an important role in the etiology and curve progression in AIS.

DNA hypermethyation and silencing of PITX1 correlated with advanced stage and poor postoperative prognosis of esophageal squamous cell carcinoma

Esophageal squamous cell carcinoma (ESCC) is associated with the accumulation of genetic and epigenetic changes in the background mucosa. Dysregulated DNA methylation is known to lead to the inactivation of tumor suppressor genes and the activation of oncogenes. To identify the genes whose expression is perturbed by abnormal DNA methylation in ESCC, integrative transcriptomics by serial analysis of gene expression (SAGE) and methylome sequencing by methyl-DNA immunoprecipitation (MeDIP) analysis were performed. We found 159 genes with significantly decreased expression in ESCC compared to that in noncancerous esophageal mucosa. MeDIP-seq analysis identified hypermethylation in the promoter region of 56 of these genes. Using surgically resected tissues of 40 cases, we confirmed that the paired-like homeodomain 1 (PITX1) gene was hypermethylated in ESCC compared to that in normal tissues (P < 0.0001) by pyrosequencing. PITX1 overexpression in ESCC cell lines inhibited cell growth and colony formation, whereas PITX1 knockdown accelerated cell growth. A PITX1-transfected ESCC cell line, KYSE30, formed smaller tumors in nude mice than in mock-transfected cells. Hypermethylation of PITX1 was associated with tumor depth (P = 0.0011) and advanced tumor stage (P = 0.0052) and predicted poor survival in ESCC (hazard ratio, 0.1538; 95% confidence interval, 0.03159–0.7488; P = 0.0169). In this study, we found a novel tumor suppressor gene of ESCC, PITX1, which is silenced by DNA hypermethylation. Downregulation of PITX1 contributes to the growth and progression of ESCC. Hypermethylation of the PITX1 in ESCC correlated with tumor progression and advanced stage cancer, and may predict a poor prognosis.

Clinicopathological features and pituitary homeobox 1 gene expression in the progression and prognosis of cutaneous malignant melanoma

The evidence that PITX1 (pituitary homeobox 1) is a significant tumor suppressor in human cancer remains largely circumstantial, but it clearly warrants further study as little is known about the tumor-inhibitory roles of PITX1 in cutaneous malignant melanoma. The aims of this study were to investigate PITX1 gene expression in patients with cutaneous malignant melanoma and to evaluate its potential relevance to clinicopathological characteristics and tumor cell proliferation. Clinicopathological findings of patients with cutaneous malignant melanoma were analyzed retrospectively. PITX1 and Ki-67 expression were detected by immunohistochemistry in malignant melanoma and healthy tissue samples from each patient. Labeling indices were calculated based on PITX1 gene and Ki-67 expression. The correlation between PITX1and Ki-67 expressions was analyzed in cutaneous malignant melanoma cases. The relationship between PITX1 expression intensity and clinicopathological characteristics was also analyzed. PITX1 expression was observed in all (100%) normal healthy skin tissue samples. In addition, PITX1 expression was found in 56 (80%) and was absent in 14 (20%) of the 70 cutaneous malignant melanoma cases. Ki-67 positive expression was only detected in the 14 (20%) PITX1-negative cases. PITX1-positive tumor cells were observed on the surface, but Ki-67 positive tumor cells were observed in deeper zones of the tumor nests. PITX1 expression was downregulated in human cutaneous malignant melanoma lesions compared with healthy skin tissue, but Ki-67 expression was upregulated in concordance with the progression of cutaneous malignant melanoma. PITX1 expression may be involved in tumor progression and is a potential tumor suppressor gene and prognostic marker for cutaneous malignant melanoma.

Protein tyrosine phosphatase 1B dephosphorylates PITX1 and regulates p120RasGAP in hepatocellular carcinoma

The effective therapeutic targets for hepatocellular carcinoma remain limited. Pituitary homeobox 1 (PITX1) functions as a tumor suppressor in hepatocarcinogenesis by regulating the expression level of Ras guanosine triphosphatase-activating protein. Here, we report that protein tyrosine phosphatases 1B (PTP1B) directly dephosphorylated PITX1 at Y160, Y175, and Y179 to further weaken the protein stability of PITX. The PTP1B-dependent decline of PITX1 reduced its transcriptional activity for p120RasGAP (RASA1), a Ras guanosine triphosphatase-activating protein. Both silencing of PTP1B and PTP1B inhibitor up-regulated the PITX1-p120RasGAP axis through hyperphosphorylation of PITX1. Sorafenib, the first and only targeted drug approved for hepatocellular carcinoma, directly decreased PTP1B activity and promoted the expression of PITX1 and p120RasGAP by PITX1 hyperphosphorylation. Molecular docking also supported the potential interaction between PTP1B and sorafenib. PTP1B overexpression impaired the sensitivity of sorafenib in vitro and in vivo, implying that PTP1B has a significant effect on sorafenib-induced apoptosis. In sorafenib-treated tumor samples, we further found inhibition of PTP1B activity and up-regulation of the PITX1-p120RasGAP axis, suggesting that PTP1B inhibitor may be effective for the treatment of hepatocellular carcinoma. By immunohistochemical staining of hepatic tumor tissue from 155 patients, the expression of PTP1B was significantly in tumor parts higher than nontumor parts (P = 0.02). Furthermore, high expression of PTP1B was significantly associated with poor tumor differentiation (P = 0.031).

CONCLUSION

PTP1B dephosphorylates PITX1 to weaken its protein stability and the transcriptional activity for p120RasGAP gene expression and acts as a determinant of the sorafenib-mediated drug effect; targeting the PITX1-p120RasGAP axis with a PTP1B inhibitor may provide a new therapy for patients with hepatocellular carcinoma.

PITX1 is a novel predictor of the response to chemotherapy in head and neck squamous cell carcinoma

The pituitary homeobox 1 (PITX1) protein is essential for developmental processes in humans. Previously, PITX1 was identified as a possible tumor suppressor gene in various types of human carcinoma. However, the association between PITX1 and human head and neck squamous cell carcinoma (HNSCC) remains to be elucidated. Immunohistochemical analysis was performed to examine the expression levels of PITX1 in 47 cases of HNSCC, and in 4 control cases. The expression of p53 was also examined in these cases. The labeling indices (LIs) were calculated, and the correlations between clinical factors (chemosensitivity, prognosis and the degree of differentiation) and the LIs were assessed. The PITX1 LI in HNSCC was 27.4±14.5%, which was significantly lower compared with the LIs of the control samples: 76.9±6.97% (P<0.05). Additionally, the PITX1 LIs were 39.9±6.2, 26.9±16.9 and 24.2±11.8% in the complete response (CR), partial response (PR), stable disease or progressive disease (SD/PD) groups, respectively. The PITX1 LI in the CR group revealed the highest result between the all groups, and it was significantly greater compared with that in the SD/PD group (P<0.01). The p53 LIs were 24.5±19.9, 25.7±16.9 and 19.8±13.8 in the CR, PR and SD/PD groups, respectively (P>0.05). Neither the PITX1 nor the p53 LIs were a statistically significant indicator of the prognosis. PITX1 is a candidate tumor suppressor gene and a possible predictive biomarker of chemosensitivity of human HNSCC.

Studies of Tumor Suppressor Genes via Chromosome Engineering

The development and progression of malignant tumors likely result from consecutive accumulation of genetic alterations, including dysfunctional tumor suppressor genes. However, the signaling mechanisms that underlie the development of tumors have not yet been completely elucidated. Discovery of novel tumor-related genes plays a crucial role in our understanding of the development and progression of malignant tumors. Chromosome engineering technology based on microcell-mediated chromosome transfer (MMCT) is an effective approach for identification of tumor suppressor genes. The studies have revealed at least five tumor suppression effects. The discovery of novel tumor suppressor genes provide greater understanding of the complex signaling pathways that underlie the development and progression of malignant tumors. These advances are being exploited to develop targeted drugs and new biological therapies for cancer.

Biophysical Characterization of G-Quadruplex Recognition in the PITX1 mRNA by the Specificity Domain of the Helicase RHAU

Nucleic acids rich in guanine are able to fold into unique structures known as G-quadruplexes. G-quadruplexes consist of four tracts of guanylates arranged in parallel or antiparallel strands that are aligned in stacked G-quartet planes. The structure is further stabilized by Hoogsteen hydrogen bonds and monovalent cations centered between the planes. RHAU (RNA helicase associated with AU-rich element) is a member of the ATP-dependent DExH/D family of RNA helicases and can bind and resolve G-quadruplexes. RHAU contains a core helicase domain with an N-terminal extension that enables recognition and full binding affinity to RNA and DNA G-quadruplexes. PITX1, a member of the bicoid class of homeobox proteins, is a transcriptional activator active during development of vertebrates, chiefly in the anterior pituitary gland and several other organs. We have previously demonstrated that RHAU regulates PITX1 levels through interaction with G-quadruplexes at the 3’-end of the PITX1 mRNA. To understand the structural basis of G-quadruplex recognition by RHAU, we characterize a purified minimal PITX1 G-quadruplex using a variety of biophysical techniques including electrophoretic mobility shift assays, UV-VIS spectroscopy, circular dichroism, dynamic light scattering, small angle X-ray scattering and nuclear magnetic resonance spectroscopy. Our biophysical analysis provides evidence that the RNA G-quadruplex, but not its DNA counterpart, can adopt a parallel orientation, and that only the RNA can interact with N-terminal domain of RHAU via the tetrad face of the G-quadruplex. This work extends our insight into how the N-terminal region of RHAU recognizes parallel G-quadruplexes.

Identification of a Potential Regulatory Variant for Colorectal Cancer Risk Mapping to Chromosome 5q31.1: A Post-GWAS Study

Large-scale genome-wide association studies (GWAS) have established chromosome 5q31.1 as a susceptibility locus for colorectal cancer (CRC), which was still lack of causal genetic variants. We searched potentially regulatory single nucleotide polymorphisms (SNPs) in the overlap region between linkage disequilibrium (LD) block of 5q31.1 and regulatory elements predicted by histone modifications, then tested their association with CRC via a case-control study. Among three candidate common variants, we found rs17716310 conferred significantly (heterozygous model: OR = 1.273, 95% confidence interval (95%CI) = 1.016–1.595, P = 0.036) and marginally (dominant model: OR = 1.238, 95%CI = 1.000–1.532, P = 0.050) increase risk for CRC in a Chinese population including 695 cases and 709 controls. This variation was suggested to be regulatory altering the activity of enhancer that control PITX1 expression. Using epigenetic information such as chromatin immunoprecipitation-sequencing (ChIP-seq) data might help researchers to interpret the results of GWAS and locate causal variants for diseases in post-GWAS era.

Strong expression of paired-like homeodomain transcription factor 1 (PITX1) is associated with a favorable outcome in human osteosarcoma

Paired-like homeodomain transcription factor 1 (PITX1) has been implicated as a tumor suppressor in various cancers. However, the biological and clinical significance of PITX1 in osteosarcoma has not been fully elucidated. Here, we studied the expression and clinical significance of PITX1 in 6 normal lower limb bone tissue specimens and 35 osteosarcoma tissue samples by immunohistochemistry. PITX1 was expressed in all normal tissues (6/6, 100 %) and in 85.7 % (30/35) of tumor tissues (P > 0.05). In addition, all normal tissue specimens showed high PITX1 expression (6/6, 100 %) while only 23.3 % (7/30) osteosarcoma tissue specimens had high PITX1 expression (P < 0.05). Patients with median overall survival (OS) >12 months had significantly higher PITX1 levels compared with those whose median OS was less than or equal to 12 months (P < 0.05 or 0.001). Furthermore, patients with lung metastasis had significantly lower PITX1 levels than patients without lung metastasis. In conclusion, PITX1 expression is downregulated in osteosarcoma and correlates with patient survival and lung metastasis.

miR-19b regulates hTERT mRNA expression through targeting PITX1 mRNA in melanoma cells

Human telomerase reverse transcriptase (hTERT) plays a crucial role in cancer development. We previously identified paired-like homeodomain1 (PITX1) as an hTERT suppressor gene. However, the underlying mechanisms that are involved in the regulation of PITX1 remain unknown. Here, we report that the microRNA-19b (miR-19b) regulates hTERT expression and cell proliferation through inhibition of PITX1. Compared with normal melanocyte cells, miR-19b expression was higher in most melanoma cells and was accompanied by downregulation of PITX1. Moreover, overexpression of miR-19b inhibited PITX1 mRNA translation through a miR-19b binding site within the 3'UTR of the PITX1 mRNA. Our combined findings indicate the participation of miR-19b as a novel upstream effector of hTERT transcription via direct targeting of PITX1.

miR‑886‑3p upregulation in clear cell renal cell carcinoma regulates cell migration, proliferation and apoptosis by targeting PITX1

miR‑886‑3p has been discovered to be involved in the oncogenesis, progression and metastasis of several types of human cancer. The aim of the present study was to identify the biological function of miR‑886‑3p in clear cell renal cell carcinoma (ccRCC) and to determine its possible molecular mechanisms. miR‑886‑3p was found to be significantly upregulated in ccRCC tissues (P<0.05), in accordance with a previous sequencing result. Functional experiments revealed that forced downregulation of miR‑886‑3p significantly inhibited cellular migration, suppressed cell proliferation and induced cell apoptosis of renal cancer cells. Paired‑like homeodomain 1 (PITX1), which has been identified as a tumor suppressor, was found to be downregulated in ccRCC tissues and identified as a target gene of miR‑886‑3p. Further experiments demonstrated that the protein level, and not the mRNA level, of PITX1 was significantly decreased or increased when miR‑886‑3p was upregulated or downregulated, respectively, indicating that miR‑886‑3p acted as an oncogene by directly regulating the protein expression of PITX1 at a post‑transcriptional level. In conclusion, this study revealed that miR‑886‑3p was upregulated in ccRCC and was involved in cellular migration, proliferation and apoptosis of renal cancer cells by directly targeting the tumor suppressor gene, PITX1.

Single nucleotide polymorphisms associated with colorectal cancer susceptibility and loss of heterozygosity in a Taiwanese population

Given the significant racial and ethnic diversity in genetic variation, we are intrigued to find out whether the single nucleotide polymorphisms (SNPs) identified in genome-wide association studies of colorectal cancer (CRC) susceptibility in East Asian populations are also relevant to the population of Taiwan. Moreover, loss of heterozygosity (LOH) may provide insight into how variants alter CRC risk and how regulatory elements control gene expression. To investigate the racial and ethnic diversity of CRC-susceptibility genetic variants and their relevance to the Taiwanese population, we genotyped 705 CRC cases and 1,802 healthy controls (Taiwan Biobank) for fifteen previously reported East Asian CRC-susceptibility SNPs and four novel genetic variants identified by whole-exome sequencing. We found that rs10795668 in FLJ3802842 and rs4631962 in CCND2 were significantly associated with CRC risk in the Taiwanese population. The previously unreported rs1338565 was associated with a significant increased risk of CRC. In addition, we also genotyped tumor tissue and paired adjacent normal tissues of these 705 CRC cases to search for LOH, as well as risk-associated and protective alleles. LOH analysis revealed preferential retention of three SNPs, rs12657484, rs3802842, and rs4444235, in tumor tissues. rs4444235 has been recently reported to be a cis-acting regulator of BMP4 gene; in this study, the C allele was preferentially retained in tumor tissues (p = 0.0023). rs4631962 and rs10795668 contribute to CRC risk in the Taiwanese and East Asian populations, and the newly identified rs1338565 was specifically associated with CRC, supporting the ethnic diversity of CRC-susceptibility SNPs. LOH analysis suggested that the three CRC risk variants, rs12657484, rs3802842, and rs4444235, exhibited somatic allele-specific imbalance and might be critical during neoplastic progression.

PITX1 is a reliable biomarker for predicting prognosis in patients with oral epithelial dysplasia

Paired-like homeodomain 1 (PITX1) genes are essential in human development. In the present study, PITX1 protein expression was evaluated in human normal oral mucosa, oral epithelial dysplasia and oral squamous cell carcinoma (OSCC), with the aim of examining the expression patterns of these critical genes during the multi-stage transformation of oral epithelial dysplasia to OSCC. PITX1 and Ki-67 expression were assessed by immunohistochemistry in 26 individuals with normal oral mucosa, 106 patients with oral epithelial dysplasia and 97 OSCC patients. The labeling indices (LIs) of PITX1 and Ki-67 were calculated and their correlation with the incidence of malignancy was evaluated. The PITX1 LI of the dysplasia specimens was significantly lower than that of the normal oral mucosa samples, but significantly higher than that of the OSCC samples. The oral epithelial dysplasia patients that exhibited low PITX1 expression showed a significantly higher incidence of malignant transformation than those exhibiting high PITX1 expression, regardless of the histological grades of their oral epithelial dysplasias. On the other hand, no correlation was observed between the Ki-67 LI and the incidence of malignancy. These results suggested that PITX1 suppression is associated with malignant transformation in the oral epithelium and that PITX1 expression may serve as a novel biomarker for predicting prognosis in oral epithelial dysplasia.

The RNA helicase RHAU (DHX36) suppresses expression of the transcription factor PITX1

RNA Helicase associated with AU-rich element (RHAU) (DHX36) is a DEAH (Aspartic acid, Glumatic Acid, Alanine, Histidine)-box RNA helicase that can bind and unwind G4-quadruplexes in DNA and RNA. To detect novel RNA targets of RHAU, we performed an RNA co-immunoprecipitation screen and identified the PITX1 messenger RNA (mRNA) as specifically and highly enriched. PITX1 is a homeobox transcription factor with roles in both development and cancer. Primary sequence analysis identified three probable quadruplexes within the 3′-untranslated region of the PITX1 mRNA. Each of these sequences, when isolated, forms stable quadruplex structures that interact with RHAU. We provide evidence that these quadruplexes exist in the endogenous mRNA; however, we discovered that RHAU is tethered to the mRNA via an alternative non–quadruplex-forming region. RHAU knockdown by small interfering RNA results in significant increases in PITX1 protein levels with only marginal changes in mRNA, suggesting a role for RHAU in translational regulation. Involvement of components of the microRNA machinery is supported by similar and non-additive increases in PITX1 protein expression on Dicer and combined RHAU/Dicer knockdown. We also demonstrate a requirement of argonaute-2, a key RNA-induced silencing complex component, to mediate RHAU-dependent changes in PITX1 protein levels. These results demonstrate a novel role for RHAU in microRNA-mediated translational regulation at a quadruplex-containing 3′-untranslated region.

A gene signature of bone metastatic colonization sensitizes for tumor-induced osteolysis and predicts survival in lung cancer

Bone metastasis of lung adenocarcinoma (AC) is a frequent complication of advanced disease. The purpose of this study was to identify key mediators conferring robust prometastatic activity with clinical significance. We isolated highly metastatic subpopulations (HMS) using a previously described in vivo model of lung AC bone metastasis. We performed transcriptomic profiling of HMS and stringent bioinformatics filtering. Functional validation was assessed by overexpression and lentiviral silencing of single, double and triple combination in vivo and in vitro. We identified HDAC4, PITX1 and ROBO1 that decreased bone metastatic ability after their simultaneous abrogation. These effects were solely linked to defects in osseous colonization. The molecular mechanisms related to bone colonization were mediated by non-cell autonomous effects that include the following: (1) a marked decrease in osteoclastogenic activity in vitro and in vivo, an effect associated with reduced pro-osteoclastogenic cytokines IL-11 and PTHrP expression levels, as well as decreased in vitro expression of stromal rankl in conditions mimicking tumor-stromal interactions; (2) an abrogated response to TGF-β signaling by decreased phosphorylation and levels of Smad2/3 in tumor cells and (3) an impaired metalloproteolytic activity in vitro. Interestingly, coexpression of HDAC4 and PITX1 conferred high prometastatic activity in vivo. Further, levels of both genes correlated with patients at higher risk of metastasis in a clinical lung AC data set and with a poorer clinical outcome. These findings provide functional and clinical evidence that this metastatic subset is an important determinant of osseous colonization. These data suggest novel therapeutic targets to effectively block lung AC bone metastasis.

Genome-wide association analyses in East Asians identify new susceptibility loci for colorectal cancer

To identify novel genetic factors for colorectal cancer (CRC), we conducted a genome-wide association study in East Asians. By analyzing genome-wide data in 2,098 cases and 5,749 controls, we selected 64 promising SNPs for replication in an independent set of samples including up to 5,358 cases and 5,922 controls. We identified four SNPs with a P-value of 8.58 × 10⁻⁷ to 3.77 × 10⁻¹⁰ in the combined analysis of all East Asian samples. Three of the four SNPs were replicated in a study conducted among 26,060 European descendants with a combined P-value of 1.22 × 10⁻¹⁰ for rs647161 (5q31.1), 6.64 × 10⁻⁹ for rs2423279 (20p12.3), and 3.06 × 10⁻⁸ for rs10774214 (12p13.32 near the CCND2 gene), respectively, derived from the meta-analysis of data from both East Asian and European populations. This study identified three new CRC susceptibility loci and provides additional insight into the genetics and biology of CRC.

Loss of desmocollin 1-3 and homeobox genes PITX1 and CDX2 are associated with tumor progression and survival in colorectal carcinoma

BACKGROUND

Genomewide expression profiling has identified a number of genes differentially expressed in colorectal carcinomas (CRCs) compared to normal tissue. Some of these genes were linked to epithelial-mesenchymal transition. We tested whether genes including desmocollins and homeobox genes were distinct on the protein level and correlated the expression with clinicopathological data.

METHODS

Tissue microarrays of 402 R0-resected colorectal carcinomas of UICC stage II or III were constructed to evaluate ten biomarkers. Furthermore, mRNA expression of desmocollins was evaluated in eight colon cancer cell lines. Demethylation test was performed by treatment with 5-aza-2´-deoxycytide in five colon cancer cell lines.

RESULTS

On protein level, high expression of desmocollin 1 (DSC1) was observed in 41.6%, DSC2 in 58.0%, DSC3 in 61.4%, E-cadherin in 71.4%, CDX2 in 58.0%, PITX1 in 55.0%, CDK4 in 0.2%, TLE1 in 1.3%, Factor H in 42.5%, and MDM2 in 0.2%. Reduced expression of DSC1-3 was statistically linked to higher grading and DSC2, E-cadherin and CDX2 with shorter survival in high-grade carcinomas. Multivariate analysis showed that pathological stage and low PITX1 expression were statistically associated with shorter patients survival. On mRNA level, seven out of eight cell lines exhibited no expression of DSC1, and four out of seven restored DSC1 expression after demethylation test.

CONCLUSIONS

Reduced expression of PITX1 was independently correlated to shorter patients survival and could serve as a prognostic marker. Decreased expression of DSC1-3 is significantly correlated with higher tumor grading. Downregulation of DSC1 could be explained by DNA hypermethylation in colon cancer cells.

Conditional over-expression of PITX1 causes skeletal muscle dystrophy in mice

Paired-like homeodomain transcription factor 1 (PITX1) was specifically up-regulated in patients with facioscapulohumeral muscular dystrophy (FSHD) by comparing the genome-wide mRNA expression profiles of 12 neuromuscular disorders. In addition, it is the only known direct transcriptional target of the double homeobox protein 4 (DUX4) of which aberrant expression has been shown to be the cause of FSHD. To test the hypothesis that up-regulation of PITX1 contributes to the skeletal muscle atrophy seen in patients with FSHD, we generated a tet-repressible muscle-specific Pitx1 transgenic mouse model in which expression of PITX1 in skeletal muscle can be controlled by oral administration of doxycycline. After PITX1 was over-expressed in the skeletal muscle for 5 weeks, the mice exhibited significant loss of body weight and muscle mass, decreased muscle strength, and reduction of muscle fiber diameters. Among the muscles examined, the tibialis anterior, gastrocnemius, quadricep, bicep, tricep and deltoid showed significant reduction of muscle mass, while the soleus, masseter and diaphragm muscles were not affected. The most prominent pathological change was the development of atrophic muscle fibers with mild necrosis and inflammatory infiltration. The affected myofibers stained heavily with NADH-TR with the strongest staining in angular-shaped atrophic fibers. Some of the atrophic fibers were also positive for embryonic myosin heavy chain using immunohistochemistry. Immunoblotting showed that the p53 was up-regulated in the muscles over-expressing PITX1. The results suggest that the up-regulation of PITX1 followed by activation of p53-dependent pathways may play a major role in the muscle atrophy developed in the mouse model.

Regulation of the human catalytic subunit of telomerase (hTERT)

Over the past decade, there has been much interest in the regulation of telomerase, the enzyme responsible for maintaining the integrity of chromosomal ends, and its crucial role in cellular immortalization, tumorigenesis, and the progression of cancer. Telomerase activity is characterized by the expression of the telomerase reverse transcriptase (TERT) gene, suggesting that TERT serves as the major limiting agent for telomerase activity. Recent discoveries have led to characterization of various interactants that aid in the regulation of human TERT (hTERT), including numerous transcription factors; further supporting the pivotal role that transcription plays in both the expression and repression of telomerase. Several studies have suggested that epigenetic modulation of the hTERT core promoter region may provide an additional level of regulation. Although these studies have provided essential information on the regulation of hTERT, there has been ambiguity of the role of methylation within the core promoter region and the subsequent binding of various activating and repressive agents. As a result, we found it necessary to consolidate and summarize these recent developments and elucidate these discrepancies. In this review, we focus on the co-regulation of hTERT via transcriptional regulation, the presence or absence of various activators and repressors, as well as the epigenetic pathways of DNA methylation and histone modifications.

Cytoplasmic ezrin and moesin correlate with poor survival in head and neck squamous cell carcinoma

Members of the 4.1 superfamily of proteins, including ezrin, moesin, merlin, and willin regulate many normal physiologic processes such as cellular shape, motility, and proliferation. In addition, they contribute both to tumor development and tumor progression. We reported previously that strong cytoplasmic ezrin expression was independently associated with poorer patient survival. One hundred and thirty-one histologically confirmed primary head and neck squamous cell carcinomas were examined prospectively for cancer progression and survival at a large health care center in the Bronx, NY, USA. Immunohistochemical analysis of ezrin, moesin, merlin, and willin expression in tissue microarray samples of primary head and neck squamous cell carcinoma revealed a significant association of increased cytoplasmic ezrin with poor cancer survival. Global RNA analyses suggest that cancers with high cytoplasmic ezrin have a more invasive phenotype. This study supports our previous findings associating cytoplasmic ezrin with more aggressive behavior and poorer outcome and indicates the need for a multi-institutional study to validate the use of cytoplasmic ezrin as a biomarker for treatment planning in head and neck squamous cell carcinoma.

Gene expression signatures differentiate ovarian/peritoneal serous carcinoma from breast carcinoma in effusions

Ovarian/primary peritoneal carcinoma and breast carcinoma are the gynaecological cancers that most frequently involve the serosal cavities.With the objective of improving on the limited diagnostic panel currently available for the differential diagnosis of these two malignancies,as well as to define tumour-specific biological targets, we compared their global gene expression patterns. Gene expression profiles of 10 serous ovarian/peritoneal and eight ductal breast carcinoma effusions were analysed using the HumanRef-8 BeadChip from Illumina.Differentially expressed candidate genes were validated using quantitative real-time PCR and immunohistochemistry. Unsupervised hierarchical clustering using all 54,675 genes in the array separated ovarian from breast carcinoma samples. We identified 288 unique probes that were significantly differentially expressed in the two cancers by greater than 3.5-fold, of which 81 and 207 were overexpressed in breast and ovarian/peritoneal carcinoma, respectively. SAM analysis identified 1078 differentially expressed probes with false discovery rate less than 0.05. Genes overexpressed in breast carcinoma included TFF1, TFF3, FOXA1, CA12, GATA3, SDC1, PITX1, TH, EHFD1, EFEMP1, TOB1 and KLF2. Genes overexpressed in ovarian/peritoneal carcinoma included SPON1, RBP1, MFGE8, TM4SF12, MMP7, KLK5/6/7, FOLR1/3,PAX8, APOL2 and NRCAM. The differential expression of 14 genes was validated by quantitative real-time PCR, and differences in 5 gene products were confirmed by immunohistochemistry. Expression profiling distinguishes ovarian/peritoneal carcinoma from breast carcinoma and identifies genes that are differentially expressed in these two tumour types. The molecular signatures unique to these cancers may facilitate their differential diagnosis and may provide a molecular basis for therapeutic target discovery.

Gene expression signatures differentiate ovarian/peritoneal serous carcinoma from breast carcinoma in effusions

Ovarian/primary peritoneal carcinoma and breast carcinoma are the gynaecological cancers that most frequently involve the serosal cavities. With the objective of improving on the limited diagnostic panel currently available for the differential diagnosis of these two malignancies, as well as to define tumour-specific biological targets, we compared their global gene expression patterns. Gene expression profiles of 10 serous ovarian/peritoneal and eight ductal breast carcinoma effusions were analysed using the HumanRef-8 BeadChip from Illumina. Differentially expressed candidate genes were validated using quantitative real-time PCR and immunohistochemistry. Unsupervised hierarchical clustering using all 54,675 genes in the array separated ovarian from breast carcinoma samples. We identified 288 unique probes that were significantly differentially expressed in the two cancers by greater than 3.5-fold, of which 81 and 207 were overexpressed in breast and ovarian/peritoneal carcinoma, respectively. SAM analysis identified 1078 differentially expressed probes with false discovery rate less than 0.05. Genes overexpressed in breast carcinoma included TFF1, TFF3, FOXA1, CA12, GATA3, SDC1, PITX1, TH, EHFD1, EFEMP1, TOB1 and KLF2. Genes overexpressed in ovarian/peritoneal carcinoma included SPON1, RBP1, MFGE8, TM4SF12, MMP7, KLK5/6/7, FOLR1/3, PAX8, APOL2 and NRCAM. The differential expression of 14 genes was validated by quantitative real-time PCR, and differences in 5 gene products were confirmed by immunohistochemistry. Expression profiling distinguishes ovarian/peritoneal carcinoma from breast carcinoma and identifies genes that are differentially expressed in these two tumour types. The molecular signatures unique to these cancers may facilitate their differential diagnosis and may provide a molecular basis for therapeutic target discovery.

Clinical significance of RASAL1 expression in colorectal carcinoma

AIM: To investigate the expression of RASAL1 (Ras GTPase-activating-like protein 1) mRNA and protein in human colorectal carcinoma (CRC) and to analyze its correlation with tumor clinicopathological features.

METHODS: Fifty paraffin-embedded surgical CRC specimens, matched tumor-adjacent tissue specimens, and normal colorectal tissue specimens were used to detect the distribution of RASAL1 by immunohistochemistry (IHC). Twenty fresh CRC specimens, matched tumor-adjacent tissue specimens, and normal colorectal tissue specimens were used to determine the levels of RASAL1 mRNA expression by RT-PCR. The correlation between RASAL1 expression and tumor clinicopathological parameters was analyzed.

RESULTS: RASAL1 was mainly localized in the cytoplasm of glands cells. The positive rate of RASAL1 protein expression in CRC was significantly lower than those in tumor-adjacent tissue and normal colorectal tissue [46% (23/50) vs 85% (17/20), 96% (48/50), both P < 0.05]. The positive rate of RASAL1 mRNA expression was also significantly lower in CRC than in tumor-adjacent tissue and normal colorectal tissue [50% (10/20) vs 90% (18/20), 95% (19/20), both P < 0.05]. The expression of RASAL1 protein was positively related with that of RASAL1 mRNA (r = 0.686, P < 0.01), but negatively with tumor differentiation degree (P < 0.05), invasive depth (P < 0.01), lymph node metastasis (P < 0.05), and TNM stage (P < 0.05).

CONCLUSION: The expression of RASAL1 mRNA and protein is reduced in CRC. RASAL1 expression is negatively related to tumor progression. RASAL1 may be a novel therapeutic target for CRC.

Identification of PITX1 as a TERT suppressor gene located on human chromosome 5

Telomerase, a ribonucleoprotein enzyme that maintains telomere length, is crucial for cellular immortalization and cancer progression. Telomerase activity is attributed primarily to the expression of telomerase reverse transcriptase (TERT). Using microcell-mediated chromosome transfer (MMCT) into the mouse melanoma cell line B16F10, we previously found that human chromosome 5 carries a gene, or genes, that can negatively regulate TERT expression (H. Kugoh, K. Shigenami, K. Funaki, J. Barrett, and M. Oshimura, Genes Chromosome Cancer 36:37-47, 2003). To identify the gene responsible for the regulation of TERT transcription, we performed cDNA microarray analysis using parental B16F10 cells, telomerase-negative B16F10 microcell hybrids with a human chromosome 5 (B16F10MH5), and its revertant clones (MH5R) with reactivated telomerase. Here, we report the identification of PITX1, whose expression leads to the downregulation of mouse tert (mtert) transcription, as a TERT suppressor gene. Additionally, both human TERT (hTERT) and mouse TERT (mtert) promoter activity can be suppressed by PITX1. We show that three and one binding site within the hTERT and mtert promoters, respectively, that express a unique conserved region are responsible for the transcriptional activation of TERT. Furthermore, we showed that PITX1 binds to the TERT promoter both in vitro and in vivo. Thus, PITX1 suppresses TERT transcription through direct binding to the TERT promoter, which ultimately regulates telomerase activity.

The gene expression profiles of primary and metastatic melanoma yields a transition point of tumor progression and metastasis

Background

The process of malignant transformation, progression and metastasis of melanoma is poorly understood. Gene expression profiling of human cancer has allowed for a unique insight into the genes that are involved in these processes. Thus, we have attempted to utilize this approach through the analysis of a series of primary, non-metastatic cutaneous tumors and metastatic melanoma samples.

Methods

We have utilized gene microarray analysis and a variety of molecular techniques to compare 40 metastatic melanoma (MM) samples, composed of 22 bulky, macroscopic (replaced) lymph node metastases, 16 subcutaneous and 2 distant metastases (adrenal and brain), to 42 primary cutaneous cancers, comprised of 16 melanoma, 11 squamous cell, 15 basal cell skin cancers. A Human Genome U133 Plus 2.0 array from Affymetrix, Inc. was utilized for each sample. A variety of statistical software, including the Affymetrix MAS 5.0 analysis software, was utilized to compare primary cancers to metastatic melanomas. Separate analyses were performed to directly compare only primary melanoma to metastatic melanoma samples. The expression levels of putative oncogenes and tumor suppressor genes were analyzed by semi- and real-time quantitative RT-PCR (qPCR) and Western blot analysis was performed on select genes.

Results

We find that primary basal cell carcinomas, squamous cell carcinomas and thin melanomas express dramatically higher levels of many genes, including SPRR1A/B, KRT16/17, CD24, LOR, GATA3, MUC15, and TMPRSS4, than metastatic melanoma. In contrast, the metastatic melanomas express higher levels of genes such as MAGE, GPR19, BCL2A1, MMP14, SOX5, BUB1, RGS20, and more. The transition from non-metastatic expression levels to metastatic expression levels occurs as melanoma tumors thicken. We further evaluated primary melanomas of varying Breslow's tumor thickness to determine that the transition in expression occurs at different thicknesses for different genes suggesting that the "transition zone" represents a critical time for the emergence of the metastatic phenotype. Several putative tumor oncogenes (SPP-1, MITF, CITED-1, GDF-15, c-Met, HOX loci) and suppressor genes (PITX-1, CST-6, PDGFRL, DSC-3, POU2F3, CLCA2, ST7L), were identified and validated by quantitative PCR as changing expression during this transition period. These are strong candidates for genes involved in the progression or suppression of the metastatic phenotype.

Conclusion

The gene expression profiling of primary, non-metastatic cutaneous tumors and metastatic melanoma has resulted in the identification of several genes that may be centrally involved in the progression and metastatic potential of melanoma. This has very important implications as we continue to develop an improved understanding of the metastatic process, allowing us to identify specific genes for prognostic markers and possibly for targeted therapeutic approaches.

Expression of pituitary homeobox 1 gene in human gastric carcinogenesis and its clinicopathological significance

AIM: To investigate the effect of pituitary homeobox 1 (PITX1) expression in cases of human gastric cancer on cancer differentiation and progression, and carcinogenesis.

METHODS: Using polyclonal PITX1 antibodies, we studied the expression of PITX1 in normal gastric mucosa, atypical hyperplasia, intestinal metaplasia, and cancer tissue samples from 83 gastric cancer patients by immunohistochemistry. Moreover, semi-reverse transcription polymerase chain reaction (semi-RT-PCR) was performed to detect the mRNA level of PITX1 in three gastric cancer cell lines and a normal gastric epithelial cell line. Subsequently, somatic mutations of the PITX1 gene in 71 gastric cancer patients were analyzed by a combination of denaturing high performance liquid chromatography (DHPLC) and DNA sequencing.

RESULTS: Immunohistochemistry showed that PITX1 was strongly or moderately expressed in the parietal cells of normal gastric mucosa (100%), while 55 (66.3%) out of 83 samples of gastric cancers showed decreased PITX1 expression. Moreover, PITX1 expression was reduced in 20 out of 28 cases (71.5%) of intestinal metaplasia, but in only 1 out of 9 cases (11%) of atypical hyperplasia. More importantly, PITX1 expression was significantly associated with the differentiation, position and invasion depth of gastric cancers (r = -0.316, P < 0.01; r = 0.213, P < 0.05; r = -0.259, P < 0.05, respectively). Similarly, levels of PITX1 mRNA were significantly decreased in 2 gastric cancer cell lines, BGC-823 and SGC-7901, compared with the normal gastric epithelial cell line GES-1 (0.306 ± 0.060 vs 0.722 ± 0.102, P < 0.05; 0.356 ± 0.081 vs 0.722 ± 0.102, P < 0.05, respectively). Nevertheless, no somatic mutation of PITX1 gene was found in 71 samples of gastric cancer by DHPLC analysis followed by sequencing.

CONCLUSION: Down-regulation of PITX1 may be a frequent molecular event in gastric carcinogenesis. Aberrant levels of PITX1 expression may be closely correlated with the progression and differentiation of gastric cancer.