Cdx1 inhibits human colon cancer cell proliferation by reducing beta-catenin/T-cell factor transcriptional activity

High-fat diet plus HNF1A variant promotes polyps by activating β-catenin in early-onset colorectal cancer

The incidence of early-onset colorectal cancer (EO-CRC) is rising and is poorly understood. Lifestyle factors and altered genetic background possibly contribute. Here, we performed targeted exon sequencing of archived leukocyte DNA from 158 EO-CRC participants, which identified a missense mutation at p.A98V within the proximal DNA binding domain of Hepatic Nuclear Factor 1 α (HNF1AA98V, rs1800574). The HNF1AA98V exhibited reduced DNA binding. To test function, the HNF1A variant was introduced into the mouse genome by CRISPR/Cas9, and the mice were placed on either a high-fat diet (HFD) or high-sugar diet (HSD). Only 1% of the HNF1A mutant mice developed polyps on normal chow; however, 19% and 3% developed polyps on the HFD and HSD, respectively. RNA-Seq revealed an increase in metabolic, immune, lipid biogenesis genes, and Wnt/β-catenin signaling components in the HNF1A mutant relative to the WT mice. Mouse polyps and colon cancers from participants carrying the HNF1AA98V variant exhibited reduced CDX2 and elevated β-catenin proteins. We further demonstrated decreased occupancy of HNF1AA98V at the Cdx2 locus and reduced Cdx2 promoter activity compared with WT HNF1A. Collectively, our study shows that the HNF1AA98V variant plus a HFD promotes the formation of colonic polyps by activating β-catenin via decreasing Cdx2 expression.

Two circPPFIA1s negatively regulate liver metastasis of colon cancer via miR-155-5p/CDX1 and HuR/RAB36

Background

Circular RNAs (circRNAs) play a critical role in colorectal cancer (CRC) progression, including metastasis. However, the detailed molecular mechanism is not fully understood.

Methods

Differentially expressed circRNAs between primary KM12C and liver metastatic KM12L4 colon cancer cells were identified by microarray. The expression of circRNAs was measured by semi-quantitative (semi-qPCR) and real time-quantitative PCR (RT-qPCR). Metastatic potential including invasive and migratory abilities, and liver metastasis were examined by transwell assays and intrasplenic injection, respectively. CircPPFIA1-associated microRNA (miRNA) and RNA-binding protein (RBP) were screened by an antisense oligonucleotide (ASO) pulldown experiment. The effects of circPPFIA1 on target gene expression were evaluated by RT-qPCR and western blot analyses.

Results

By analyzing circRNA microarray data, we identified two anti-metastatic circRNAs generated from PPFIA1 with different length, which named circPPFIA1-L (long) and -S (short). They were significantly downregulated in liver metastatic KM12L4 cells compared to primary KM12C cells. The knockdown of circPPFIA1s in KM12C enhanced metastatic potential and increased liver metastasis. Conversely, overexpression of circPPFIA1s weakened metastatic potential and inhibited liver metastasis. circPPFIA1s were found to function as sponges of oncogenic miR-155-5p and Hu antigen R (HuR) by an ASO pulldown experiment. circPPFIA1s upregulated tumor-suppressing CDX1 expression and conversely downregulated oncogenic RAB36 by decoying miR-155-5p and by sequestering HuR, respectively.

Conclusion

Our findings demonstrate that circPPFIA1s inhibit the liver metastasis of CRC via the miR-155-5p/CDX1 and HuR/RAB36 pathways.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12943-022-01667-w.

Association between germline variants and somatic mutations in colorectal cancer

Colorectal cancer (CRC) is a heterogeneous disease with evidence of distinct tumor types that develop through different somatically altered pathways. To better understand the impact of the host genome on somatically mutated genes and pathways, we assessed associations of germline variations with somatic events via two complementary approaches. We first analyzed the association between individual germline genetic variants and the presence of non-silent somatic mutations in genes in 1375 CRC cases with genome-wide SNPs data and a tumor sequencing panel targeting 205 genes. In the second analysis, we tested if germline variants located within previously identified regions of somatic allelic imbalance were associated with overall CRC risk using summary statistics from a recent large scale GWAS (n≃125 k CRC cases and controls). The first analysis revealed that a variant (rs78963230) located within a CNA region associated with TLR3 was also associated with a non-silent mutation within gene FBXW7. In the secondary analysis, the variant rs2302274 located in CDX1/PDGFRB frequently gained/lost in colorectal tumors was associated with overall CRC risk (OR = 0.96, p = 7.50e-7). In summary, we demonstrate that an integrative analysis of somatic and germline variation can lead to new insights about CRC.

Serum Periostin Level and Genetic Polymorphisms Are Associated with Vertebral Fracture in Chinese Postmenopausal Women

Purposes: In order to investigate the association between serum periostin levels and the variation of its encoding gene POSTN and the prevalence of vertebral fractures and bone mineral density (BMD) in Chinese postmenopausal women, an association study was performed. Materials and Methods: 385 postmenopausal women were recruited. For participants without a history of vertebral fracture, lateral X-rays of the spine covering the fourth thoracic spine to the fifth lumbar spine were performed to detect any asymptomatic vertebral fractures. Ten tag-single nucleotide polymorphisms (SNP) of POSTN were genotyped. Serum periostin levels, biochemical parameters, and BMD were measured individually. Results: rs9603226 was significantly associated with vertebral fractures. Compared to allele G, the minor allele A carriers of rs9603226 had a 1.722-fold higher prevalence of vertebral fracture (p = 0.037). rs3923854 was significantly associated with the serum periostin level. G/G genotype of rs3923854 had a higher serum periostin level than C/C and C/G (67.26 ± 19.90 ng/mL vs. 54.57 ± 21.44 ng/mL and 54.34 ± 18.23 ng/mL). Furthermore, there was a negative correlation between the serum level of periostin and BMD at trochanter and total hip. Conclusion: Our study suggested that genetic variation of POSTN could be a predicting factor for the risk of vertebral fractures. The serum level of periostin could be a potential biochemical parameter for osteoporosis in Chinese postmenopausal women.

Genetic architectures of proximal and distal colorectal cancer are partly distinct

OBJECTIVE

An understanding of the etiologic heterogeneity of colorectal cancer (CRC) is critical for improving precision prevention, including individualized screening recommendations and the discovery of novel drug targets and repurposable drug candidates for chemoprevention. Known differences in molecular characteristics and environmental risk factors among tumors arising in different locations of the colorectum suggest partly distinct mechanisms of carcinogenesis. The extent to which the contribution of inherited genetic risk factors for CRC differs by anatomical subsite of the primary tumor has not been examined.

DESIGN

To identify new anatomical subsite-specific risk loci, we performed genome-wide association study (GWAS) meta-analyses including data of 48 214 CRC cases and 64 159 controls of European ancestry. We characterised effect heterogeneity at CRC risk loci using multinomial modelling.

RESULTS

We identified 13 loci that reached genome-wide significance (p<5×10-8) and that were not reported by previous GWASs for overall CRC risk. Multiple lines of evidence support candidate genes at several of these loci. We detected substantial heterogeneity between anatomical subsites. Just over half (61) of 109 known and new risk variants showed no evidence for heterogeneity. In contrast, 22 variants showed association with distal CRC (including rectal cancer), but no evidence for association or an attenuated association with proximal CRC. For two loci, there was strong evidence for effects confined to proximal colon cancer.

CONCLUSION

Genetic architectures of proximal and distal CRC are partly distinct. Studies of risk factors and mechanisms of carcinogenesis, and precision prevention strategies should take into consideration the anatomical subsite of the tumour.

Long noncoding RNA ATB promotes ovarian cancer tumorigenesis by mediating histone H3 lysine 27 trimethylation through binding to EZH2

Ovarian cancer (OC) remains one of the most lethal gynecological malignancies. The unfavourable prognosis is mainly due to the lack of early‐stage diagnosis, drug resistance and recurrence. Therefore, it needs to investigate the mechanism of OC tumorigenesis and identify effective biomarkers for the clinical diagnosis. It is reported that long noncoding RNAs (lncRNAs) play important roles during the tumorigenesis of OC. Therefore, the present study aimed to study the role and clinical significance of LncRNAs ATB (lnc‐ATB) in the development and progression of OC. In our research, lnc‐ATB expression in OC tissues was elevated compared with adjacent normal tissues and high expression of lnc‐ATB was associated with poor outcomes of OC patients. The silencing of lnc‐ATB blocked cell proliferation, invasion and migration in SKOV3 and A2780 cells. RNA immunoprecipitation and RNA pull‐down results showed that lnc‐ATB positively regulated the expression of EZH2 via directly interacting with EZH2. Besides, the overexpression of EZH2 partly rescued lnc‐ATB silencing‐inducing inhibition of cell proliferation, invasion and migration. Chromatin immunoprecipitation assay results demonstrated that the silencing of lnc‐ATB reduced the occupancy of caudal‐related homeobox protein 1, Forkhead box C1, Large tumour suppressor kinase 2, cadherin‐1 and disabled homolog 2 interacting protein promoters on EZH2 and H3K27me3. These data revealed the oncogenic of lnc‐ATB and provided a novel biomarker for OC diagnosis. Furthermore, these findings indicated the mechanism of lnc‐ATB functioning in the progression of OC, which provided a new target for OC therapy.

Role of HOX Genes in Stem Cell Differentiation and Cancer

HOX genes encode an evolutionarily conserved set of transcription factors that control how the phenotype of an organism becomes organized during development based on its genetic makeup. For example, in bilaterian-type animals, HOX genes are organized in gene clusters that encode anatomic segment identity, that is, whether the embryo will form with bilateral symmetry with a head (anterior), tail (posterior), back (dorsal), and belly (ventral). Although HOX genes are known to regulate stem cell (SC) differentiation and HOX genes are dysregulated in cancer, the mechanisms by which dysregulation of HOX genes in SCs causes cancer development is not fully understood. Therefore, the purpose of this manuscript was (i) to review the role of HOX genes in SC differentiation, particularly in embryonic, adult tissue-specific, and induced pluripotent SC, and (ii) to investigate how dysregulated HOX genes in SCs are responsible for the development of colorectal cancer (CRC) and acute myeloid leukemia (AML). We analyzed HOX gene expression in CRC and AML using information from The Cancer Genome Atlas study. Finally, we reviewed the literature on HOX genes and related therapeutics that might help us understand ways to develop SC-specific therapies that target aberrant HOX gene expression that contributes to cancer development.

RNA sequencing analyses reveal novel differentially expressed genes and pathways in pancreatic cancer

Gene expression microarrays have identified many tumor markers and therapeutic targets for pancreatic ductal adenocarcinoma (PDAC). However, microarray profilings have limited sensitivity and are prone to cross-hybridization between homologous DNA fragments. Here, we perform a transcriptome analysis of paired tumor and adjacent benign pancreatic tissues from 10 patients who underwent resection for PDAC. We identify a total of 2736 differentially expressed genes (DEGs) with false discovery rate less than 0.05, including 1554 upregulated, 1182 downregulated, and 6 microRNAs (miR-614, miR-217, miR-27b, miR-4451, miR-3609, and miR-612). Overexpression of five DEGs, i.e. KRT16, HOXA10, CDX1, SI, and SERPINB5 in tumors is confirmed by RT-PCR in 20 additional tissues. Overexpression of KRT16 in PDAC is also verified on protein level. In addition, top canonical pathways such as granulocyte adhesion and diapedesis pathway have been identified. Our study represents a comprehensive characterization of the PDAC transcriptome and provides insight to the mechanisms of pancreatic carcinogenesis and potential biomarkers and novel therapeutic targets for pancreatic cancer.

CDX2 expression is concordant between primary colorectal cancer lesions and corresponding liver metastases independent of chemotherapy: a single-center retrospective study in Japan

Objective

Loss of caudal-type homeobox transcription factor 2 (CDX2) expression in colorectal cancers (CRCs) has recently been proposed as a promising predictive biomarker for not only prognosis but also response to chemotherapy. However, the relationship between alterations in CDX2 expression during cancer progression and response to chemotherapy remains unclear. We herein aimed to determine the concordance of CDX2 expression between primary CRCs and corresponding liver metastases, in association with chemotherapy.

Results

Primary CRCs exhibited heterogeneous CDX2 expression. Seven of the 144 CRCs in the cohort (4.9%, 95% confidential interval, 2.0%–9.8%) were CDX2-negative. The concordance rate of the CDX2 expression status in patients who did not receive chemotherapy was 100% (P = 0.041), whereas the concordance rate among patients who received chemotherapy only after primary resection was 96.3% (P = 0.005). Moreover, the concordance rate in patients who received chemotherapy before both primary resection and liver metastasectomy was 100% (P < 0.001).

Conclusion

CDX2 expression status was highly concordant between primary CRCs and corresponding liver metastases, independent of chemotherapy, suggesting that the CDX2 expression status in CRCs was not affected by metastasis or chemotherapy.

Methods

A total of 144 consecutive patients with CRC who were treated at a single center in Japan between 2006 and 2014 were included. Formalin-fixed paraffin-embedded whole sections of surgically resected primary CRCs and corresponding liver metastases were assessed for CDX2 expression by immunohistochemistry.

Colon cancers carrying BRAF V600E and β-catenin T41A activating mutations are resistant to numerous common anticancer drugs

Colorectal cancer is a common malignancy with a high prevalence and associated mortality rate. However, the preclinical tools currently used for drug development are insufficient. The aim of the present study was to establish and characterize a specific patient-derived colon cancer xenograft (PDCCX) mouse model for drug testing. Primary colon tumors were obtained from 10 patients by surgical resection, and tumor tissues were subsequently grafted into nude mice followed by consecutive passages. Primary tumors and xenograft tumors were collected and processed for DNA sequencing, histological evaluation and immunohistochemical staining. The responses of fifth-generation PDCCX mice to 5-fluorouracil, oxaliplatin, and cetuximab were assessed. Two PDCCX cell lines were successfully established. The histology and protein expression levels of SMAD family member 3, epidermal growth factor receptor, c-MET, caudal type homeobox 2, E-cadherin and β-catenin in the xenograft tumors were consistently maintained from the primary cancer tissues. BRAF V600E and β-catenin T41A double mutations were identified in one cell line, and were associated with a lack of response to 5-fluorouracil, oxaliplatin and cetuximab treatment. This PDCCX cell line may provide a reliable tool for preclinical evaluation of the efficacy of novel therapies that may target the BRAF V600E and β-catenin mutations.

Identification of novel candidate variants including COL6A6 polymorphisms in early-onset atopic dermatitis using whole-exome sequencing

Background

The prevalence of atopic dermatitis has increased over the last 10 years. Atopic dermatitis tends to run in families and commonly begins to manifest in childhood. The prevalence of atopic dermatitis is as high as 20% in children. Thus, early diagnosis and treatment of atopic dermatitis are important. Understanding its genetic basis is also needed to facilitate early detection.

Methods

To identify family-specific candidate genetic variants associated with early-onset atopic dermatitis in Koreans, we carried out whole-exome sequencing of three separate families with this condition. Additional validation was performed in 112 AD patients and 61 controls using Sanger sequencing.

Results

We focused on both common functional variants with a minor allele frequency higher than 1% and rare variants with a minor allele frequency less than 1%. The relevance of the respective variants was supported by a program that could predict whether the mutations resulted in damaged protein function. Fourteen overlapping genes were identified during exome sequencing. Three variants of the COL6A6 gene appeared in all three families and were in close proximity to atopic dermatitis-related loci on chromosome 3q21. The homozygous frequency for the rs16830494 minor allele (AA) and the rs59021909 (TT) allele and the rs200963433 heterozygous (CT) frequency were all higher in AD cases compared to controls in a population-based case-control study.

Conclusion

Identifying family-specific COL6A6 polymorphisms and genetic variants of other candidate genes associated with AD using WES is a novel approach. Our study suggests that COL6A6 variants may be risk factors for atopic dermatitis. This study provides a genetic basis for early-onset AD diagnosis in Korean patients and the development of new therapies.

Trial registration

Trial registration number: IRB NO. C2008030 (133); Name of registry: The collection research of clinical data and patient blood to identify genetic and protein biomarker of atopic dermatitis; Date of registration: 09-July-2008.

Trial registration number: IRB NO. C2015258 (1716); Name of registry: The collection study of patient blood and clinical data for the development of the prognosis prediction and early diagnosis of atopic dermatitis; Date of registration: 15-jan-2016.

Electronic supplementary material

The online version of this article (doi:10.1186/s12881-017-0368-9) contains supplementary material, which is available to authorized users.

Application of unique sequence index (USI) barcode to gene expression profiling in gastric adenocarcinoma

Accurate expression profiling is imperative for understanding the biological roles of mRNAs. Real-time PCR have been at the forefront of biological innovation in detection and monitoring of gene expression, however, fluorophore-labeled oligonucleotides and double-stranded DNA binding dyes, the two most frequently used dyes in RNA detection, are not very cost effective and have poor specificity, respectively. We have developed a cost effective and specific approach for mRNA expression profiling via added unique sequence index (USI) to cDNAs before amplification. USI is a barcode which enable the detection of each target RNA. Using this method, caudal type homeobox 1 (CDX1) and FAT atypical cadherin 4 (FAT4) expressions were investigated in tumoral and non-tumoral tissues of gastric cancer patients and compared with commercial ABI kit. Both methods indicated that FAT4 and CDX1 expression were significantly reduced in gastric cancer tissues compared with adjacent noncancerous tissues. Moreover, we have shown that this assay is highly sensitive, linear and reproducible. USI barcode not only provides a powerful tool for mRNA detection due to its sensitivity, specificity and cost-effectiveness, but also allows comfortable design for real-time qPCR assays within the least time and empowers the analysis of many transcripts of virtually any organism. Furthermore, USI barcode is highly affordable for large numbers of different samples or small sample sizes without microarray and expensive commercial platforms.

Impact of homeobox genes in gastrointestinal cancer

Homeobox genes, including HOX and non-HOX genes, have been identified to be expressed aberrantly in solid tumors. In gastrointestinal (GI) cancers, most studies have focused on the function of non-HOX genes including caudal-related homeobox transcription factor 1 (CDX1) and CDX2. CDX2 is a crucial factor in the development of pre-cancerous lesions such as Barrett’s esophagus or intestinal metaplasia in the stomach, and its tumor suppressive role has been investigated in colorectal cancers. Recently, several HOX genes were reported to have specific roles in GI cancers; for example, HOXA13 in esophageal squamous cell cancer and HOXB7 in stomach and colorectal cancers. HOXD10 is upregulated in colorectal cancer while it is silenced epigenetically in gastric cancer. Thus, it is essential to examine the differential expression pattern of various homeobox genes in specific tumor types or cell lineages, and understand their underlying mechanisms. In this review, we summarize the available research on homeobox genes and present their potential value for the prediction of prognosis in GI cancers.

Computational Identification of Key Regulators in Two Different Colorectal Cancer Cell Lines

Transcription factors (TFs) are gene regulatory proteins that are essential for an effective regulation of the transcriptional machinery. Today, it is known that their expression plays an important role in several types of cancer. Computational identification of key players in specific cancer cell lines is still an open challenge in cancer research. In this study, we present a systematic approach which combines colorectal cancer (CRC) cell lines, namely 1638N-T1 and CMT-93, and well-established computational methods in order to compare these cell lines on the level of transcriptional regulation as well as on a pathway level, i.e., the cancer cell-intrinsic pathway repertoire. For this purpose, we firstly applied the Trinity platform to detect signature genes, and then applied analyses of the geneXplain platform to these for detection of upstream transcriptional regulators and their regulatory networks. We created a CRC-specific position weight matrix (PWM) library based on the TRANSFAC database (release 2014.1) to minimize the rate of false predictions in the promoter analyses. Using our proposed workflow, we specifically focused on revealing the similarities and differences in transcriptional regulation between the two CRC cell lines, and report a number of well-known, cancer-associated TFs with significantly enriched binding sites in the promoter regions of the signature genes. We show that, although the signature genes of both cell lines show no overlap, they may still be regulated by common TFs in CRC. Based on our findings, we suggest that canonical Wnt signaling is activated in 1638N-T1, but inhibited in CMT-93 through cross-talks of Wnt signaling with the VDR signaling pathway and/or LXR-related pathways. Furthermore, our findings provide indication of several master regulators being present such as MLK3 and Mapk1 (ERK2) which might be important in cell proliferation, migration, and invasion of 1638N-T1 and CMT-93, respectively. Taken together, we provide new insights into the invasive potential of these cell lines, which can be used for development of effective cancer therapy.

Cdx1 and Cdx2 function as tumor suppressors

In humans, colorectal cancer is often initiated through APC loss of function, which leads to crypt hyperplasia and polyposis driven by unrestricted canonical Wnt signaling. Such polyps typically arise in the colorectal region and are at risk of transforming to invasive adenocarcinomas. Although colorectal cancer is the third most common cause of cancer-related death worldwide, the processes impacting initiation, transformation, and invasion are incompletely understood. Murine APC(Min/+) mutants are often used to model colorectal cancers; however, they develop nonmetastatic tumors confined largely to the small intestine and are thus not entirely representative of the human disease. APC(Min/+) alleles can collaborate with mutations impacting other pathways to recapitulate some aspects of human colorectal cancer. To this end, we assessed APC(Min/+)-induced polyposis following somatic loss of the homeodomain transcription factor Cdx2, alone or with a Cdx1 null allele, in the adult gastrointestinal tract. APC(Min/+)-Cdx2 mutants recapitulated several aspects of human colorectal cancer, including an invasive phenotype. Notably, the concomitant loss of Cdx1 led to a significant increase in the incidence of tumors in the distal colon, relative to APC(Min/+)-Cdx2 offspring, demonstrating a previously unrecognized role for this transcription factor in colorectal tumorigenesis. These findings underscore previously unrecognized roles for Cdx members in intestinal tumorigenesis.

Modeling human gastrointestinal inflammatory diseases using microphysiological culture systems

Gastrointestinal illnesses are a significant health burden for the US population, with 40 million office visits each year for gastrointestinal complaints and nearly 250,000 deaths. Acute and chronic inflammations are a common element of many gastrointestinal diseases. Inflammatory processes may be initiated by a chemical injury (acid reflux in the esophagus), an infectious agent (Helicobacter pylori infection in the stomach), autoimmune processes (graft versus host disease after bone marrow transplantation), or idiopathic (as in the case of inflammatory bowel diseases). Inflammation in these settings can contribute to acute complaints (pain, bleeding, obstruction, and diarrhea) as well as chronic sequelae including strictures and cancer. Research into the pathophysiology of these conditions has been limited by the availability of primary human tissues or appropriate animal models that attempt to physiologically model the human disease. With the many recent advances in tissue engineering and primary human cell culture systems, it is conceivable that these approaches can be adapted to develop novel human ex vivo systems that incorporate many human cell types to recapitulate in vivo growth and differentiation in inflammatory microphysiological environments. Such an advance in technology would improve our understanding of human disease progression and enhance our ability to test for disease prevention strategies and novel therapeutics. We will review current models for the inflammatory and immunological aspects of Barrett's esophagus, acute graft versus host disease, and inflammatory bowel disease and explore recent advances in culture methodologies that make these novel microphysiological research systems possible.

The clinical perspectives of CDX2 expression in colorectal cancer: a qualitative systematic review

INTRODUCTION

Homeobox genes are often deregulated in cancer. They can have both oncogenic and tumor-suppressing potential. The Caudal-related homeobox transcription factor 2 (CDX2) is an intestine-specific transcription factor. It is implicated in differentiation, proliferation, cell-adhesion, and migration. CDX2 has been proposed as a tumor suppressor in colorectal cancer but its role is still controversial. This systematic review were undertaken in order to clarify CDX2s role in colorectal cancer.

METHODS

A literature search was performed in the MEDLINE database from 1966 to February 2014. Only studies in which all or a part of the experimental design were performed on human colorectal cancer tissue were included. Thus, studies solely performed in cell-lines or animal models were excluded.

RESULTS

Fifty-two articles of relevance were identified. CDX2 expression was rarely lost in colorectal cancers, however the expression pattern may often be heterogeneous within the tumor and can be selectively down regulated at the invasive front and in tumor buddings. Loss of CDX2 expression is probably correlated to tumor grade, stage, right-sided tumor location, MMR-deficiency, CIMP, and BRAF mutations. The CDX2 gene is rarely mutated but the locus harboring the gene is often amplified and may suggest CDX2 as a linage-survival oncogene. CDX2 might be implicated in cell proliferation and migration through cross-talk with the Wnt-signaling pathway, tumor-stroma proteins, and inflammatory cytokines.

CONCLUSION

A clear role for CDX2 expression in colorectal cancer remains to be elucidated, and it might differ in relation to the underlying molecular pathways leading to the cancer formation.

The impact of sphingosine kinase-1 in head and neck cancer

Head and neck squamous cell carcinoma (HNSCC) has a high reoccurrence rate and an extremely low survival rate. There is limited availability of effective therapies to reduce the rate of recurrence, resulting in high morbidity and mortality of advanced cases. Late presentation, delay in detection of lesions, and a high rate of metastasis make HNSCC a devastating disease. This review offers insight into the role of sphingosine kinase-1 (SphK1), a key enzyme in sphingolipid metabolism, in HNSCC. Sphingolipids not only play a structural role in cellular membranes, but also modulate cell signal transduction pathways to influence biological outcomes such as senescence, differentiation, apoptosis, migration, proliferation, and angiogenesis. SphK1 is a critical regulator of the delicate balance between proliferation and apoptosis. The highest expression of SphK1 is found in the advanced stage of disease, and there is a positive correlation between SphK1 expression and recurrent tumors. On the other hand, silencing SphK1 reduces HNSCC tumor growth and sensitizes tumors to radiation-induced death.  Thus, SphK1 plays an important and influential role in determining HNSCC proliferation and metastasis. We discuss roles of SphK1 and other sphingolipids in HNSCC development and therapeutic strategies against HNSCC.

Ectopic expression of Ptf1a induces spinal defects, urogenital defects, and anorectal malformations in Danforth's short tail mice

Danforth's short tail (Sd) is a semidominant mutation on mouse chromosome 2, characterized by spinal defects, urogenital defects, and anorectal malformations. However, the gene responsible for the Sd phenotype was unknown. In this study, we identified the molecular basis of the Sd mutation. By positional cloning, we identified the insertion of an early transposon in the Sd candidate locus approximately 12-kb upstream of Ptf1a. We found that insertion of the transposon caused overexpression of three neighboring genes, Gm13344, Gm13336, and Ptf1a, in Sd mutant embryos and that the Sd phenotype was not caused by disruption of an as-yet-unknown gene in the candidate locus. Using multiple knockout and knock-in mouse models, we demonstrated that misexpression of Ptf1a, but not of Gm13344 or Gm13336, in the notochord, hindgut, cloaca, and mesonephros was sufficient to replicate the Sd phenotype. The ectopic expression of Ptf1a in the caudal embryo resulted in attenuated expression of Cdx2 and its downstream target genes T, Wnt3a, and Cyp26a1; we conclude that this is the molecular basis of the Sd phenotype. Analysis of Sd mutant mice will provide insight into the development of the spinal column, anus, and kidney.

Caudal regression syndrome (CRS) is a congenital heterogeneous constellation of caudal anomalies that includes varying degrees of agenesis of the spinal column, anorectal malformations, and genitourinary anomalies. Its pathogenesis is unclear. However, it could be the result of excessive physiologic regression of the embryonic caudal region based on analyses of the various mouse mutants carrying caudal agenesis. Among the mouse mutants, the Danforth's short tail (Sd) mouse is considered a best model for human CRS. Sd is a semidominant mutation, characterized by spinal defects, urogenital defects, and anorectal malformations, thus showing phenotypic similarity to human CRS. Although Sd is known to map to mouse chromosome 2, little is known about the molecular nature of the mutation. Here, we demonstrate an insertion of one type of retrotransposon near the Ptf1a gene. This resulted in ectopic expression of Ptf1a gene in the caudal region of the embryo and downregulation of Cdx2 and its downstream targets, leading to characteristic phenotypes in Sd mouse. Thus, Sd mutant mice will provide insight into the development of the spinal column, anus, and kidney.

CDX2 serves as a Wnt signaling inhibitor and is frequently methylated in lung cancer

Aberrant promoter region hypermethylation of upstream transcription factors may be responsible for silencing entire anti-neoplastic gene networks. In this study, we explored whether transcription factor coding gene, caudal-related homeobox 2 (CDX2), is silenced by promoter hypermethylation in lung cancer, and examined its potential tumor-suppressive functions. Semi-quantitative RT-PCR showed that four of six lung cancer cell lines exhibited no or weak CDX2 expression. Expression of CDX2 was correlated to CDX2 promoter region methylation status, as determined by methylation-specific PCR (MSP) and bisulfite sequencing. Restoration of CDX2 expression was induced by treatment with demethylating drug 5-aza-2'-deoxycytidine (5-AZA) in lung cancer cell lines. Methylation of CDX2 was common in human primary lung cancer (61 of 110 tumors, 55.45%), but no methylation was found in normal lung tissues. Re-expression of CDX2 suppressed lung cancer cell proliferation and blocked cells in G1 phase. β-catenin/TCF activity and downstream genes expression were inhibited by re-expression of CDX2, and increased by depletion of CDX2. In conclusion, CDX2 is frequently methylated in lung cancer, and expression of CDX2 is regulated by promoter region hypermethylation. CDX2 may serve as a tumor suppressor in lung cancer and inhibits lung cancer cell proliferation by suppressing Wnt signaling.

Association of CDX1 binding site of periostin gene with bone mineral density and vertebral fracture risk

SUMMARY

Periostin (POSTN) as a regulator of osteoblast differentiation and bone formation may affect susceptibility to osteoporosis. This study suggests POSTN as a candidate gene for bone mineral density (BMD) variation and vertebral fracture risk, which could better our understanding about the genetic pathogenesis of osteoporosis and will be useful in clinic in the future.

INTRODUCTION

The genetic determination of osteoporosis is complex and ill-defined. Periostin (POSTN), an extracellular matrix secreted by osteoblasts and a regulator of osteoblast differentiation and bone formation, may affect susceptibility to osteoporosis.

METHODS

We adopted a tag-single nucleotide polymorphism (SNP) based association method followed by imputation-based verification and identification of a causal variant. The association was investigated in 1,572 subjects with extreme-BMD and replicated in an independent population of 2,509 subjects. BMD was measured by dual X-ray absorptiometry. Vertebral fractures were identified by assessing vertebral height from X-rays of the thoracolumbar spine. Association analyses were performed with PLINK toolset and imputation analyses with MACH software. The top imputation finding was subsequently validated by genotyping. Interactions between POSTN and another BMD-related candidate gene sclerostin (SOST) were analyzed using MDR program and validated by logistical regression analyses. The putative transcription factor binding with target sequence was confirmed by electrophoretic mobility shift assay (EMSA).

RESULTS

Several SNPs of POSTN were associated with BMD or vertebral fractures. The most significant polymorphism was rs9547970, located at the -2,327 bp upstream (P = 6.8 × 10(-4)) of POSTN. Carriers of the minor allele G per copy of rs9547970 had 1.33 higher risk of vertebral fracture (P = 0.007). An interactive effect between POSTN and SOST upon BMD variation was suggested (P < 0.01). A specific binding of CDX1 to the sequence of POSTN with the major allele A of rs9547970 but not the variant G allele was confirmed by EMSA.

CONCLUSIONS

Our results suggest POSTN as a candidate gene for BMD variation and vertebral fracture risk.

Cdx2 controls expression of the protocadherin Mucdhl, an inhibitor of growth and β-catenin activity in colon cancer cells

BACKGROUND & AIMS

The intestine-specific homeobox transcription factor Cdx2 is an important determinant of intestinal identity in the embryonic endoderm and regulates the balance between proliferation and differentiation in the adult intestinal epithelium. Human colon tumors often lose Cdx2 expression, and heterozygous inactivation of Cdx2 in mice increases colon tumorigenesis. We sought to identify Cdx2 target genes to determine how it contributes to intestinal homeostasis.

METHODS

We used expression profiling analysis to identify genes that are regulated by Cdx2 in colon cancer cells lines. Regulation and function of a potential target gene were further investigated using various cell assays.

RESULTS

In colon cancer cell lines, Cdx2 directly regulated the transcription of the gene that encodes the protocadherin Mucdhl. Mucdhl localized to the apex of differentiated cells in the intestinal epithelium, and its expression was reduced in most human colon tumors. Overexpression of Mucdhl inhibited low-density proliferation of colon cancer cells and reduced tumor formation in nude mice. One isoform of Mucdhl interacted with β-catenin and inhibited its transcriptional activity.

CONCLUSIONS

The transcription factor Cdx2 activates expression of the protocadherin Mucdhl, which interacts with β-catenin and regulates activities of intestinal cells. Loss of Cdx2 expression in colon cancer cells might reduce expression of Mucdhl and thereby lead to tumor formation.

Assessment of epigenetic contributions to sexually-dimorphic Kiss1 expression in the anteroventral periventricular nucleus of mice

The Kiss1 gene, which encodes kisspeptin and is critical for reproduction, is sexually differentiated in the hypothalamic anteroventral periventricular (AVPV)/rostral periventricular (PeN) nuclei. Specifically, female rodents have higher AVPV/PeN Kiss1 expression than males, but how this Kiss1 sex difference is induced in early development is poorly understood. Here, we explored the contribution of epigenetic mechanisms to the establishment of the AVPV/PeN Kiss1 sex difference, focusing on histone deacetylation and DNA methylation. First, we utilized postnatal pharmacological blockade of histone deacetylation and analyzed Kiss1 expression in the AVPV/PeN. Postnatal disruption of histone deacetylase modestly increased AVPV Kiss1 cell number in both sexes but did not alter the Kiss1 sex difference. Next, we assessed whether the level of CpG methylation, which can influence transcription factor binding and gene expression, in the murine Kiss1 gene differs between males and females. We found significant sex differences in methylation at several CpG sites in the putative promoter and first intron of the Kiss1 gene in the AVPV/PeN, but not in the arcuate (which lacks adult Kiss1 sex differences), suggesting that differential methylation of the Kiss1 gene may influence sexually-dimorphic Kiss1 expression in the AVPV/PeN. Transgenic impairment of methyl CpG-binding protein-2 function did not eliminate the Kiss1 sex difference, indicating that other methylation factors are involved. Interestingly, CpG methylation in the AVPV/PeN was lower in males than females, suggesting that transcriptional repressors may contribute to the AVPV/PeN Kiss1 sex difference, a possibility supported by in silico identification of putative repressor binding sites near some of the sexually-dimorphic CpG.

Sphingosine kinase 1 is overexpressed and promotes proliferation in human thyroid cancer

Sphingosine kinase 1 (SphK1), an oncogenic kinase, has been previously found to be elevated in various types of human cancer and play a role in tumor development and progression. Nevertheless, the biological and clinical significance of SphK1 in thyroid cancer is largely unknown. Here, we demonstrate that the expression of SphK1 is generally up-regulated in thyroid cancer and that its expression level is correlated with the degree of thyroid malignancy. Silencing SphK1 by specific RNA interference is able to suppress the proliferation of thyroid cancer cells, and SphK1 expression level is strongly associated with the expression of proliferation cell nuclear antigen in thyroid cancer tissues. Of particular note is that depletion of SphK1 results in dephosphorylation of protein kinase B and glycogen synthase kinase-3β and subsequent inactivation of β-catenin-T-cell factor/lymphoid enhancing factor transcriptional activity. Hence, taken together, our study has identified SphK1 as a proproliferative oncogenic kinase, an Akt/glycogen synthase kinase-3β/β-catenin activator, and probably a biomarker for thyroid cancer as well.

Regulation of self-renewal and differentiation by the intestinal stem cell niche

The gastrointestinal epithelium is a highly organised tissue that is constantly being renewed. In order to maintain homeostasis, the balance between intestinal stem cell (ISC) self-renewal and differentiation must be carefully regulated. In this review, we describe how the intestinal stem cell niche provides a unique environment to regulate self-renewal and differentiation of ISCs. It has traditionally been believed that the mesenchymal myofibroblasts play an important role in the crosstalk between ISCs and the niche. However, recent evidence in Drosophila and in vertebrates suggests that epithelial cells also contribute to the niche. We discuss the multiple signalling pathways that are utilised to regulate stemness within the niche, including members of the Wnt, BMP and Hedgehog pathways, and how aberrations in these signals lead to disruption of the normal crypt-villus axis. Finally, we also discuss how CDX1 and inhibition of the Notch pathway are important in specifying enterocyte and goblet cell differentiation respectively.

HOXB7 as a prognostic factor and mediator of colorectal cancer progression

PURPOSE

This study was to investigate the clinicopathologic significance and potential role of HOXB7 in the development and progression of colorectal cancer (CRC).

EXPERIMENTAL DESIGN

The relationship between HOXB7 expression and clinical characteristics of CRC was analyzed in 224 paraffin-embedded archived CRC specimens by immunohistochemistry (IHC). The effects of HOXB7 on cell growth and proliferation, as well as on tumorigenesis, were examined both in vitro and in vivo, using MTT assay, colony formation assay, cell cycle analysis, soft agar assay, and tumorigenesis in nude mice. Western blotting and real-time reverse transcriptase-PCR were performed to examine the impact of HOXB7 on the PI3K/Akt and MAPK signaling pathways.

RESULTS

HOXB7 protein level was significantly correlated with advanced Dukes stage (P < 0.001), T stage (P = 0.012), distant metastasis (P = 0.042), higher proliferation index (P = 0.007) and poor survival of patients (P = 0.005). Enforced expression of HOXB7 in CRC cell lines significantly enhanced cell growth, proliferation and tumorigenesis. Conversely, knockdown of HOXB7 caused an inhibition of cell growth, proliferation, and tumorigenesis. We also showed that HOXB7 accelerated G(0)-G(1) to S-phase transition concomitantly with upregulation of cyclin D1 and downregulation of p27Kip1. On the contrary, knockdown of HOXB7 caused G(1)-S-phase arrest, downregulation of cyclin D1 and upregulation of p27Kip1. Enforced expression of HOXB7 could enhance PI3K/AKT and MAPK pathway activity.

CONCLUSION

Our findings suggest that HOXB7 protein, as a valuable marker of CRC prognosis, plays an important role in the development and progression of human CRC.

Ectopic Cdx2 expression in murine esophagus models an intermediate stage in the emergence of Barrett's esophagus

Barrett's esophagus (BE) is an intestinal metaplasia that occurs in the setting of chronic acid and bile reflux and is associated with a risk for adenocarcinoma. Expression of intestine-specific transcription factors in the esophagus likely contributes to metaplasia development. Our objective was to explore the effects of an intestine-specific transcription factor when expressed in the mouse esophageal epithelium. Transgenic mice were derived in which the transcription factor Cdx2 is expressed in squamous epithelium using the murine Keratin-14 gene promoter. Effects of the transgene upon cell proliferation and differentiation, gene expression, and barrier integrity were explored. K14-Cdx2 mice express the Cdx2 transgene in esophageal squamous tissues. Cdx2 expression was associated with reduced basal epithelial cell proliferation and altered cell morphology. Ultrastructurally two changes were noted. Cdx2 expression was associated with dilated space between the basal cells and diminished cell-cell adhesion caused by reduced Desmocollin-3 mRNA and protein expression. This compromised epithelial barrier function, as the measured trans-epithelial electrical resistance (TEER) of the K14-Cdx2 epithelium was significantly reduced compared to controls (1189 Ohm*cm(2) ±343.5 to 508 Ohm*cm(2)±92.48, p = 0.0532). Secondly, basal cells with features of a transitional cell type, intermediate between keratinocytes and columnar Barrett's epithelial cells, were observed. These cells had reduced keratin bundles and increased endoplasmic reticulum levels, suggesting the adoption of secretory-cell features. Moreover, at the ultrastructural level they resembled "Distinctive" cells associated with multilayered epithelium. Treatment of the K14-Cdx2 mice with 5'-Azacytidine elicited expression of BE-associated genes including Cdx1, Krt18, and Slc26a3/Dra, suggesting the phenotype could be advanced under certain conditions. We conclude that ectopic Cdx2 expression in keratinocytes alters cell proliferation, barrier function, and differentiation. These altered cells represent a transitional cell type between normal squamous and columnar BE cells. The K14-Cdx2 mice represent a useful model to study progression from squamous epithelium to BE.

Cdx2 levels modulate intestinal epithelium maturity and Paneth cell development

BACKGROUND & AIMS

Caudal-related homeobox protein 2 (Cdx2) is an intestine-specific transcription factor that is important for intestinal development and intestine-specific gene expression. Cdx2 regulates intestinal cell-cell adhesion, proliferation, and the transcriptional activities of Wnt and β-catenin in cell culture systems. We generated transgenic mice that overexpress Cdx2 in the small intestinal and colonic epithelium to investigate the role of Cdx2 in differentiation and function of the intestinal epithelium.

METHODS

We established 4 different lines of villin-Cdx2 transgenic mice. Intestines were collected from infant, 3-month old, and wild-type mice. Genes of interest and cell lineage markers were examined by polymerase chain reaction and immunohistochemistry.

RESULTS

Villin-Cdx2 transgenic mice had complex phenotypes that were associated with transgene expression levels. The 2 lines that had the greatest levels of transgene expression had significant, preweaning failure to grow and death; these were the result of early epithelial maturation and alterations in nutrient digestion and absorption. Fat malabsorption was a prominent feature. Other effects associated with the transgene expression included loss of Paneth cell markers, increases in goblet cells, and migration of proliferating, EphB2-expressing cells to the crypt base. Loss of Paneth cell markers was associated with reduced nuclear localization of β-catenin but not homeotic posteriorization of the epithelium by Cdx2.

CONCLUSIONS

Overexpression of Cdx2 in the small intestine is associated with reduced post-natal growth, early epithelial maturation, alterations in crypt base organization, and changes in Paneth and goblet cell lineages. Cdx2 is a critical regulator not only of intestine-specific genes, but also processes that determine epithelial maturity and function.

Intestine-specific transcription factor Cdx2 induces E-cadherin function by enhancing the trafficking of E-cadherin to the cell membrane

Cdx2 is an intestine-specific transcription factor required for normal intestinal epithelium development. Cdx2 regulates the expression of intestine-specific genes and induces cell adhesion and columnar morphogenesis. Cdx2 also has tumor-suppressor properties, including the reduction of colon cancer cell proliferation and cell invasion, the latter due to its effects on cell adhesion. E-cadherin is a cell adhesion protein required for adherens junction formation and the establishment of intestinal cell polarity. The objective of this study was to elucidate the mechanism by which Cdx2 regulates E-cadherin function. Two colon cancer cell lines were identified in which Cdx2 expression was associated with increased cell-cell adhesion and diminished cell migration. In both cell lines, Cdx2 did not directly alter E-cadherin levels but increased its trafficking to the cell membrane compartment. Cdx2 enhanced this trafficking by altering receptor tyrosine kinase (RTK) activity. Cdx2 expression diminished phosphorylated Abl and phosphorylated Rac levels, which are downstream effectors of RTKs. Specific chemical inhibition or short interfering RNA (shRNA) knockdown of c-Abl kinase phenocopied Cdx2's cell-cell adhesion effects. In Colo 205 cells, Cdx2 reduced PDGF receptor and IGF-I receptor activation. This was mediated by caveolin-1, which was induced by Cdx2. Targeted shRNA knockdown of caveolin-1 restored PDGF receptor and reversed E-cadherin membrane trafficking, despite Cdx2 expression. We conclude that Cdx2 regulates E-cadherin function indirectly by disrupting RTK activity and enhancing E-cadherin trafficking to the cell membrane compartment. This novel mechanism advances Cdx2's prodifferentiation and antitumor properties and suggests that Cdx2 may broadly regulate RTK activity in normal intestinal epithelium by modulating membrane trafficking of proteins.

Pinin modulates expression of an intestinal homeobox gene, Cdx2, and plays an essential role for small intestinal morphogenesis

Pinin (Pnn), a nuclear speckle-associated protein, has been shown to function in maintenance of epithelial integrity through altering expression of several key adhesion molecules. Here we demonstrate that Pnn plays a crucial role in small intestinal development by influencing expression of an intestinal homeobox gene, Cdx2. Conditional inactivation of Pnn within intestinal epithelia resulted in significant downregulation of a caudal type homeobox gene, Cdx2, leading to obvious villus dysmorphogenesis and severely disrupted epithelial differentiation. Additionally, in Pnn-deficient small intestine, we observed upregulated Tcf/Lef reporter activity, as well as misregulated expression/distribution of beta-catenin and Tcf4. Since regulation of Cdx gene expression has been closely linked to Wnt/beta-catenin signaling activity, we explored the possibility of Pnn's interaction with beta-catenin, a major effector of the canonical Wnt signaling pathway. Co-immunoprecipitation assays revealed that Pnn, together with its interaction partner CtBP2, a transcriptional co-repressor, was in a complex with beta-catenin. Moreover, both of these proteins were found to be recruited to the proximal promoter area of Cdx2. Taken together, our results suggest that Pnn is essential for tight regulation of Wnt signaling and Cdx2 expression during small intestinal development.

Modelling Barrett's oesophagus

Barrett's oesophagus is the replacement of normal squamous oesophageal epithelium with an intestinalized columnar epithelium. Although some insight has been gained as to what Barrett's oesophagus is, how this columnar epithelium emerges from within a stratified squamous epithelium remains an unanswered question. We have sought to determine whether oesophageal keratinocytes can be trans-differentiated into Barrett's oesophagus cells. Using an Affymetrix microarray, we found unexpectedly that gene-expression patterns in the Barrett's oesophagus were only slightly more similar to the normal small intestine than they were to the normal oesophagus. Thus gene-expression patterns suggest significant molecular similarities remain between Barrett's oesophagus cells and normal squamous oesophageal epithelium, despite their histological resemblance with intestine. We next determined whether directed expression of intestine-specific transcription factors could induce intestinalization of keratinocytes. Retroviral-mediated Cdx2 (Caudal-type homeobox 2) expression in immortalized human oesophageal keratinocytes engineered with human telomerase reverse transcriptase (EPC2-hTERT cells) could be established transiently, but not maintained, and was associated with a reduction in cell proliferation. Co-expression of cyclin D1 rescued proliferation in the Cdx2-expressing cells, but co-expression of dominant-negative p53 did not. Cdx2 expression in the EPC2-hTERT.D1 cells did not induce intestinalization. However, when combined with treatments that induce chromatin remodelling, there was a significant induction of Barrett's oesophagus-associated genes. Studies are ongoing to determine whether other intestinal transcription factors, either alone or in combination, can provoke greater intestinalization of oesophageal keratinocytes. We conclude that, on the basis of gene-expression patterns, Barrett's oesophagus epithelial cells may represent an intermediate between oesophageal keratinocytes and intestinal epithelial cells. Moreover, our findings suggest that it may be possible to induce Barrett's oesophagus epithelial cells from oesophageal keratinocytes by altering the expression of certain critical genes.

Cdx genes, inflammation, and the pathogenesis of intestinal metaplasia

Intestinal metaplasia (IM) is a biologically interesting and clinically relevant condition in which one differentiated type of epithelium is replaced by another that is morphologically similar to normal intestinal epithelium. Two classic examples of this are gastric IM and Barrett's esophagus (BE). In both, a chronic inflammatory microenvironment, provoked either by Helicobacter pylori infection of the stomach or acid and bile reflux into the esophagus, precedes the metaplasia. The Caudal-related homeodomain transcription factors Cdx1 and Cdx2 are critical regulators of the normal intestinal epithelial cell phenotype. Ectopic expression of Cdx1 and Cdx2 occurs in both gastric IM as well as in BE. This expression precedes the onset of the metaplasia and implies a causal role for these factors in this process. We review the observations regarding the role of chronic inflammation and the Cdx transcription factors in the pathogenesis of gastric IM and BE.

The intestine-specific transcription factor Cdx2 inhibits beta-catenin/TCF transcriptional activity by disrupting the beta-catenin-TCF protein complex

Cdx2 is an intestine-specific transcription factor known to regulate proliferation and differentiation. We have reported previously that Cdx2 limits the proliferation of human colon cancer cells by inhibiting the transcriptional activity of the beta-catenin-T-cell factor (TCF) bipartite complex. Herein we further elucidate this mechanism. Studies with a classic Cdx2 target gene and a canonical Wnt/beta-catenin/TCF reporter suggest that Cdx2 regulates these promoters by distinctly different processes. Specifically, inhibition of beta-catenin/TCF activity by Cdx2 does not require Cdx2 transcriptional activity. Instead, Cdx2 binds beta-catenin and disrupts its interaction with the DNA-binding TCF factors, thereby silencing beta-catenin/TCF target gene expression. Using Cdx2 mutants, we map the Cdx2 domains required for the inhibition of beta-catenin/TCF activity. We identify a subdomain in the N-terminus that is highly conserved and when mutated significantly reduces Cdx2 inhibition of beta-catenin/TCF transcriptional activity. Mutation of this subdomain also abrogates Cdx2's anti-proliferative effects in colon cancer cells. In summary, we conclude that Cdx2 binds beta-catenin and disrupts the beta-catenin-TCF complex. Considering the pivotal role of beta-catenin/TCF activity in driving proliferation of normal intestinal epithelial and colon cancer cells, our findings suggest a novel mechanism for Cdx2-mediated regulation of Wnt/beta-catenin signaling and cell proliferation.

Calcium-sensing receptor in cancer: good cop or bad cop?

The extracellular calcium-sensing receptor (CaR) is a versatile 'sensor' for di- and polycationic molecules in the body. CaR plays a key role in the defense against hypercalcemia by "sensing" extracellular calcium levels in the parathyroid and kidney, the key organs maintaining systemic calcium homeostasis. Although mutation of CaR gene has so far not been associated with any malignancy, aberrant functions of CaR have implications in malignant progression. One situation is loss of CaR expression, resulting in loss of growth suppressing effects of elevated extracellular Ca(2+) by CaR, reported in parathyroid adenoma and in colon carcinoma. Another situation is activation of CaR, resulting in increased production of parathyroid hormone-related peptide (PTHrP), a primary causal factor in hypercalcemia of malignancy and a contributor to metastatic processes involving bone. CaR signaling and effects have been studied in several cancers including ovarian cancers, gastrinomas, and gliomas in addition to comparatively detailed studies in breast, prostate, and colon cancers. Studies on H-500 rat Leydig cells, a xenotransplantable model of humoral hypercalcemia of malignancy has shed much light on the mechanisms of CaR-induced cancer cell growth and survival. Pharmacological agonists and antagonists of CaR hold therapeutic promise depending on whether activation of CaR is required such as in case of colon cancer or inactivating the receptor is required as in the case of breast- and prostate tumors.

Induction of intestinalization in human esophageal keratinocytes is a multistep process

Barrett's esophagus (BE) is the replacement of normal squamous esophageal mucosa with an intestinalized columnar epithelium. The molecular mechanisms underlying its development are not understood. Cdx2 is an intestine-specific transcription factor that is ectopically expressed in BE, but its role in this process is unclear. Herein, we describe a novel cell culture model for BE. Retroviral-mediated Cdx2 expression in immortalized human esophageal keratinocytes [EPC-human telomerase reverse transcriptase (hTERT)] could transiently be established but not maintained and was associated with a reduction in cell proliferation. Coexpression of cyclin D1, but not a dominant-negative p53, rescued proliferation in the Cdx2-expressing cells. Cdx2 expression in the EPC-hTERT.D1 cells decreased cell proliferation but did not induce intestinalization. We investigated for other treatments to enhance intestinalization and found that acidic culture conditions uniformly killed EPC-hTERT.D1.Cdx2 cells. However, treatment with 5-aza-2-deoxycytidine (5-AzaC) to demethylate epigenetically silenced genes did appear to be tolerated. Multiple Cdx2 target genes, markers of intestinal differentiation and markers of BE, were induced by this 5-AzaC treatment. More interestingly, the expression level of several of these genes was enhanced only in the EPC-hTERT.D1-Cdx2 cells treated with 5-AzaC. Two of these, SLC26a3/DRA (downregulated in adenoma) and Na+/H+ exchanger 2 (NHE2), were not previously known to be elevated in BE; however, we confirmed their elevation in BE tissue samples. 5-AzaC treatment also induced cell senescence, even at low doses. We conclude that ectopic proliferation signals, alterations in epigenetic gene regulation and the inhibition of tumor suppressor mechanisms are required for Cdx2-mediated intestinalization of human esophageal keratinocytes in BE.

Repression of the desmocollin 2 gene expression in human colon cancer cells is relieved by the homeodomain transcription factors Cdx1 and Cdx2

Desmosomes are intracellular junctions that provide strong cell-cell adhesion in epithelia and cardiac muscle. Their disruption causes several human diseases and contributes to the epithelial-to-mesenchymal transition observed in cancer. Desmocollin 2 (DSC2) is a cadherin superfamily member and a critical component of desmosomes found in intestinal epithelium. However, the mechanism regulating DSC2 gene expression in intestinal cells is not known. Cdx1 and Cdx2 are homeodomain transcription factors that regulate intestine-specific gene expression. Cdx expression in the past has been associated with the induction of desmosomes. We now show that the DSC2 gene is a transcriptional target for Cdx1 and Cdx2. Colon cancer cell lines retaining Cdx2 expression typically express DSC2. Restoration of Cdx expression in Colo 205 cells induced DSC2 mRNA and protein and the formation of desmosomes. The 5'-flanking region of the DSC2 promoter contains two consensus Cdx-binding sites. Electrophoretic mobility shift assays show that Cdx1 and Cdx2 bind these sites in vitro, and chromatin immunoprecipitation confirmed Cdx2 binding in vivo. DSC2 promoter truncations established that these regions are Cdx responsive. The truncations also identify a region of the promoter in which potent transcriptional repressors act. This repressor activity is relieved by Cdx binding. We conclude that the homeodomain transcription factors Cdx1 and Cdx2 regulate DSC2 gene expression in intestinal epithelia by reversing the actions of a transcriptional repressor. The regulation of desmosomal junctions by Cdx contributes to normal intestinal epithelial columnar morphology and likely antagonizes the epithelial-to-mesenchymal transition necessary for the metastasis of colon cancer cells in humans.

Biology of intestinal metaplasia in 2008: more than a simple phenotypic alteration

This review concentrates on one main aspect of cancerization in the oesophagus and stomach: principally, intestinal metaplasia. There are at least two other important pathways that lead to cancer and do not need such a morphological transformation. One is the gastric type of carcinoma on the Lauren classification, which arises directly from the stem cell zone and is the signet ring form of cancer, while the other is spasmolytic polypeptide-expressing metaplasia (SPEM)--spasmolytic polypeptide (TFF2) expressing metaplasia, where the gastric glands become filled with TFF2-expressing cells and may also lead to gastric dysplasia and cancer. The development of intestinal metaplasia is complex. Here, we examine intestinal metaplasia in molecular terms, noting the over-expression of Cdx1, Cdx2, Pdx1, Oct1, TFF3 and the downregulation of Hedgehog signalling; Runx3 is deactivated by epigenetic silencing, and pathways such as Wnt and MARK/ERK are involved. These changes start to explain the principles of the development of intestinal metaplasia and suggest that the regulation of these genes is of importance in the development of gastric cancer.

The homeodomain transcription factor Cdx1 does not behave as an oncogene in normal mouse intestine

The Caudal-related homeobox genes Cdx1 and Cdx2 are intestine-specific transcription factors that regulate differentiation of intestinal cell types. Previously, we have shown Cdx1 to be antiproliferative and to promote cell differentiation. However, other studies have suggested that Cdx1 may be an oncogene. To test for oncogenic behavior, we used the murine villin promoter to ectopically express Cdx1 in the small intestinal villi and colonic surface epithelium. No changes in intestinal architecture, cell differentiation, or lineage selection were observed with expression of the transgene. Classic oncogenes enhance proliferation and induce tumors when ectopically expressed. However, the Cdx1 transgene neither altered intestinal proliferation nor induced spontaneous intestinal tumors. In a murine model for colitis-associated cancer, the Cdx1 transgene decreased, rather than increased, the number of adenomas that developed. In the polyps, the expression of the endogenous and the transgenic Cdx1 proteins was largely absent, whereas endogenous Villin expression was retained. This suggests that transgene silencing was specific and not due to a general Villin inactivation. In conclusion, neither the ectopic expression of Cdx1 was associated with changes in intestinal cell proliferation or differentiation nor was there increased intestinal cancer susceptibility. Our results therefore suggest that Cdx1 is not an oncogene in normal intestinal epithelium.

Wnt5a secretion stimulated by the extracellular calcium-sensing receptor inhibits defective Wnt signaling in colon cancer cells

To understand the role of the colonic extracellular calcium-sensing receptor (CaSR) in calcium chemoprotection against colon cancer, we activated the CaSR with 5 mM Ca(2+) on HT-29 cells, an adenocarcinoma cell line. High Ca(2+) stimulated the upregulation (as assessed by RT-PCR) and the secretion of Wnt5a (assessed by Western blot), a noncanonical Wnt family member. Inhibiting CaSR activity with a short interfering RNA (siRNA) duplex against the CaSR reduced CaSR protein and prevented the secretion of Wnt5a. Dominant negative CaSR (R185Q) or siRNA blocked the high Ca(2+)-mediated inhibition of the beta-catenin reporter TOPflash. The CaSR/Wnt5a inhibition of beta-catenin reporter was prevented by dominant negative ubiquitin ligase seven in absentia homolog 2 (Siah2). In low-calcium medium, overexpressing Wnt5a increased Siah2 amplicons and protein. Inducing the expression of full-length adenomatous polyposis coli (APC) prevented CaSRmediated increases of Siah2 and Wnt5a. Overexpressing the receptor tyrosine kinase-like orphan receptor 2 (Ror2) increased Wnt5a and CaSR-mediated inhibition of TOPflash. Conditioned medium from Wnt5a-transfected cells added to HT-29 cells in low-Ca(2+) medium inhibited the beta-catenin reporter. This inhibition was blocked dose responsively by Frizzled-8/Fc chimeric antibody. Overexpression of Ror2 in HT-29 cells in low-Ca(2+) medium increased the inhibition of beta-catenin reporter caused by recombinant Wnt5a protein compared with addition of Wnt5a protein alone. Our findings demonstrate that APC status plays a key role as a determinant of Wnt5a secretion and suggest that CaSR-mediated secretion of Wnt5a will inhibit defective Wnt signaling in APC-truncated cells in an autocrine manner.

The homeodomain transcription factors Cdx1 and Cdx2 induce E-cadherin adhesion activity by reducing beta- and p120-catenin tyrosine phosphorylation

The homeodomain transcription factors Cdx1 and Cdx2 are regulators of intestine-specific gene expression. They also regulate intestinal cell differentiation and proliferation; however, these effects are poorly understood. Previously, we have shown that expression of Cdx1 or Cdx2 in human Colo 205 cells induces a mature colonocyte morphology characterized by the induction of a polarized, columnar shape with apical microvilli and strong cell-cell adhesion. To elucidate the mechanism underlying this phenomenon, we investigated the adherens junction complex. Cdx1 or Cdx2 expression reduced Colo 205 cell migration and invasion in vitro, suggesting a physiologically significant change in cadherin function. However, Cdx expression did not significantly effect E-cadherin, alpha-, beta-, or gamma-catenin, or p120-catenin protein levels. Additionally, no alteration in their intracellular distribution was observed. Cdx expression did not alter the coprecipitation of beta-catenin with E-cadherin; however, it did reduce p120-catenin-E-cadherin coprecipitation. Tyrosine phosphorylation of beta- and p120-catenin is known to disrupt E-cadherin-mediated cell adhesion and is associated with robust p120-catenin/E-cadherin interactions. We specifically investigated beta- and p120-catenin for tyrosine phosphorylation and found that it was significantly diminished by Cdx1 or Cdx2 expression. We restored beta- and p120-catenin tyrosine phosphorylation in Cdx2-expressing cells by knocking down the expression of protein tyrosine phosphatase 1B and noted a significant decline in cell-cell adhesion. We conclude that Cdx expression in Colo 205 cells induces E-cadherin-dependent cell-cell adhesion by reducing beta- and p120-catenin tyrosine phosphorylation. Ascertaining the mechanism for this novel Cdx effect may improve our understanding of the regulation of cell-cell adhesion in the colonic epithelium.

A functional role of Cdx2 in beta-catenin signaling during transdifferentiation in endometrial carcinomas

Nuclear beta-catenin is required for changes in morphology from glandular to morular phenotypes of endometrial carcinoma (Em Ca) cells, with activation of p14(ARF)/p53/p21(Waf1) and alteration of p16(INK4A)/pRb pathways. Having demonstrated previously that the homeodomain transcription factor Cdx2 increases markedly during intestinal epithelial cell differentiation, we have examined its effects in beta-catenin signaling during transdifferentiation of Em Ca cells. In clinical cases, Cdx2 immunoreactivity, along with increased mRNA signals, was found to overlap with nuclear accumulation of beta-catenin and p21(Waf1) in morules, demonstrating an inverse correlation with cell proliferation. In cell lines, over-expression of active form beta-catenin resulted in a significant increase in endogenous Cdx2 expression at both mRNA and protein levels. Furthermore, the Cdx2 promoter was activated by T-cell factor 4 (TCF4) -independent activated beta-catenin, as well as Cdx2 itself, through the region from -39 to +9 bp relative to transcription start site. Cells over-expressing exogenous Cdx2 showed high levels of p21(Waf1) expression due to stabilization of the mRNA status, resulting in significant decrease in the proliferation rate, in contrast to the lack of apparent changes in morphology. Moreover, transfected Cdx2 could inhibit beta-catenin/TCF4-mediated transcriptional activation of target genes, including p14(ARF) and cyclin D1, probably through indirect mechanisms. These data suggest that over-expression of Cdx2 mediated by nuclear beta-catenin and Cdx2 itself can cause an inhibition of Em Ca cell proliferation through up-regulation of p21(Waf1) expression, modulating beta-catenin/TCF4-mediated transcription. We therefore conclude that an association between Cdx2 and beta-catenin signaling may participate in induction of transdifferentiation of Em Ca cells.

Wnt signaling and gastrointestinal tumorigenesis in mouse models

The canonical Wnt signaling plays important roles in embryonic development and tumorigenesis. For the latter, induced mutations in mice have greatly contributed to our understanding of the molecular mechanisms of cancer initiation and progression. Here, I will review recent reports on gastrointestinal cancer model mice, with an emphasis on the roles of the Wnt signal pathway. They include: mouse models for familial adenomatous polyposis; modifying factors that affect mouse intestinal polyposis, including the genes that help cancer progression; Wnt target genes that affect mouse intestinal polyposis; and a mouse model of gastric cancer that mimics Helicobacter pyroli infection.

CDX2 does not suppress tumorigenicity in the human gastric cancer cell line MKN45

CDX2 is a Drosophila caudal-related homeobox transcription factor that is expressed specifically in the intestine. In mice, ectopic expression of CDX2 in the gastric mucosa gives rise to intestinal metaplasia and in one model, gastric carcinoma. In humans, increased CDX2 expression is associated with gastric intestinal metaplasia and tubular adenocarcinomas. These patterns of expression have shown that CDX2 is important for the initiation of intestinal metaplasia in the gastric mucosa, but the role of CDX2 in established gastric cancer remains unclear. We sought to determine whether CDX2 contributes to tumorigenic potential in established gastric cancer. The CDX2 gene in MKN45 gastric carcinoma cells was disrupted using targeted homologous recombination. The resulting CDX2-/- cells are essentially identical to their parental cells, with the exception of CDX2 ablation. We found no significant differences in the proliferation of CDX2-/- cells compared to CDX2+/+ cells, in vitro or in vivo. Molecular analyses show that loss of CDX2 predominantly altered the expression of genes involved in intestinal glandular differentiation and adhesion. However, there were no microscopic differences in tumor differentiation. We conclude that disruption of CDX2 in MKN45 cells does not significantly affect their tumorigenic potential.

MUC4 expression is regulated by cystic fibrosis transmembrane conductance regulator in pancreatic adenocarcinoma cells via transcriptional and post-translational mechanisms

MUC4 mucin is a high molecular weight transmembrane glycoprotein that plays important roles in tumour biology. It is aberrantly expressed in pancreatic adenocarcinoma, while not being detectable in the normal pancreas. Previous studies have demonstrated that the cystic fibrosis transmembrane conductance regulator (CFTR), a chloride channel that is defective in CF, is implicated in multiple cellular functions, including gene regulation. In the present study, using a CFTR-defective pancreatic cancer cell line and its derived subline expressing functional CFTR, we report that MUC4 expression is negatively regulated by CFTR. Short-interfering RNA (siRNA)-mediated silencing of CFTR also leads to an increased expression of MUC4. Additionally, our results suggest that CFTR-mediated regulation of MUC4 is cell density-dependent and is achieved by transcriptional and posttranslational mechanisms. Moreover, in a panel of pancreatic cancer cell lines and normal pancreas, we observed that CFTR was downregulated in pancreatic cancer cells and negatively correlated with MUC4 in most cases. An aberrant expression of MUC4 was also detected in the CF pancreas. Downregulation of CFTR in pancreatic adenocarcinoma and its inverse association with the tumour-linked mucin, MUC4, indicate novel function(s) of CFTR in pancreatic tumour biology and suggest the implication of new signalling pathway(s) in MUC4 regulation.

Runx3 controls growth and differentiation of gastric epithelial cells in mammals

Runx3 is a transcription factor expressed by gastric epithelial cells. In the Runx3(-/-) mouse, gastric epithelia exhibited hyperplasia, and epithelial apoptosis was suppressed. By analyzing growth of the epithelial cells in primary culture, we found that Runx3(-/-) gastric epithelial cells are less sensitive to the growth-inhibitory and apoptosis-inducing activities of TGF-beta, suggesting that Runx3 is a major growth regulator of gastric epithelial cells by regulating their response to TGF-beta. We also found that Runx3 plays an important role in the control of gastric epithelial differentiation. When subcutaneously implanted into nude mice, Runx3(-/-) gastric epithelial cells formed tumors in which some cells differentiated into intestinal-type cells. Clonal analysis showed that gastric epithelial cells transdifferentiate into intestinal-type cells in the tumor. Considering that gastric epithelial differentiation is very stable, and that intestinal-type cells never differentiate in the mouse stomach, it is remarkable that gastric epithelial cells transdifferentiate into intestinal-type cells. We conclude that Runx3 is deeply involved in the control of both growth and differentiation of gastric epithelial cells. The role of Runx3 in the specification of gastric epithelial cells is discussed.

CDX2 has tumorigenic potential in the human colon cancer cell lines LOVO and SW48

CDX2 is a Drosophila caudal-related homeobox transcription factor that is important for the establishment and maintenance of intestinal epithelial cells. CDX2 is a marker of colon cancer, with strong staining in up to 90% of colonic adenocarcinomas. CDX2 heterozygous-null mice develop colonic neoplasms, which have suggested that CDX2 is a tumor suppressor. However, CDX2 has not been reported to affect xenograft growth. Furthermore, CDX2 is rarely mutated in colon cancer, which has led to suggestions that it may play only a minor role as a tumor suppressor in colon cancer. To understand the functional contributions of CDX2 to colon cancer, we disrupted CDX2 in LOVO and SW48 human colon cancer cell lines by targeted homologous recombination. Consistent with the literature, disruption of CDX2 enhanced anchorage-dependent cell proliferation. However, homozygous loss of CDX2 led to significant inhibition of anchorage-independent growth in LOVO cells, and cell lethality in SW48 cells. Further analyses revealed that disruption of CDX2 led to anchorage-independent G1 to S growth arrest and anoikis. In vivo xenograft studies confirmed that disruption of CDX2 inhibited LOVO tumor growth. These data demonstrate that CDX2 mediates anchorage-independent growth and survival. Thus, CDX2 has tumorigenic potential in the human colon cancer cell lines LOVO and SW48.

Cdx2 modulates proliferation in normal human intestinal epithelial crypt cells

The homeobox gene Cdx2 is involved in the regulation of the expression of intestine specific markers such as sucrase-isomaltase and lactase-phlorizin hydrolase. Previous studies performed with immortalized or transformed intestinal cell lines have provided evidence that Cdx2 can promote morphological and functional differentiation in these experimental models. However, no data exist concerning the implication of this factor in normal human intestinal cell physiology. In the present work, we have investigated the role of Cdx2 in normal human intestinal epithelial crypt (HIEC) cells that lack this transcription factor. The establishment of HIEC cells expressing Cdx2 in an inducible manner shows that forced expression of Cdx2 significantly alters the proliferation of intestinal crypt cells and stimulates dipeptidylpeptidase IV expression but is not sufficient to trigger intestinal terminal differentiation. These observations suggest that Cdx2 requires additional factors to activate the enterocyte differentiation program in normal undifferentiated cells.