Polymorphisms in the CLDN1 and CLDN7 genes are related to differentiation and tumor stage in colon carcinoma

Epigenetic Regulation of Claudin-1 in the Development of Ovarian Cancer Recurrence and Drug Resistance

Over 21,000 women are diagnosed with ovarian cancer (OC) in the United States each year and over half that number succumb to this disease annually, often due to recurrent disease. A deeper understanding of the molecular events associated with recurrent disease is needed to identify potential targets. Using genome-scale DNA methylation and gene expression data for 16 matched primary-recurrent advanced stage serous epithelial OCs, we discovered that Claudin-1 (CLDN1), a tight junction protein, shows a stronger correlation between expression and methylation in recurrent versus primary OC at multiple CpG sites (R= –0.47 to −0.64 versus R= -0.32 to −0.57, respectively). An independent dataset showed that this correlation is stronger in tumors from short-term (<3y) survivors than in tumors from long-term (>7y) survivors (R= −0.41 to −0.46 versus R= 0.06 to −0.19, respectively). The presence of this inverse correlation in short-term survivors and recurrent tumors suggests an important role for this relationship and potential predictive value for disease prognosis. CLDN1 expression increased following pharmacologic inhibition of DNA methyltransferase activity (p< 0.001), thus validating the role of methylation in CLDN1 gene inhibition. CLDN1 knockdown enhanced chemosensitivity and suppressed cell proliferation, migration, and wound healing (p< 0.05). Stable CLDN1 knockdown in vivo resulted in reduced xenograft tumor growth but did not reach significance. Our results indicate that the relationship between CLDN1 methylation and expression plays an important role in OC aggressiveness and recurrence.

Single nucleotide variants c.-13G → C (rs17429833) and c.108C → T (rs72466472) in the CLDN1 gene and increased risk for familial colorectal cancer

BACKGROUND

The Claudin-1 (CLDN1) protein plays an important role in the function of the tight junction and studies have shown it is aberrantly downregulated in many tumors including colorectal cancer (CRC). The aim of this study was to determine the relationship between four SNVs in the CLDN1 gene [c.-13G → C (rs17429833), c.108C → T (rs72466472), c.369T → C (rs9869263), and c.370G → A (rs140846629)] and the risk of familial colorectal cancer (FCC).

METHODS

A case-control study was conducted with peripheral blood DNAs from 50 patients with CRC that belong to FCC families and 96 healthy control individuals. The analysis of genetic variants was performed by PCR and restriction enzymatic digestion.

RESULTS

The patients and control groups presented in Hardy-Weinberg equilibrium for all evaluated SNVs. No significant differences occurred in wild-type homozygous, heterozygous and variant homozygous genotypes, separately or together, in patient and control groups for the SNVs rs72466472, rs9869263, and rs140846629. However, for the SNV rs17429833, increased frequency of GC genotype occurred in patients compared to healthy individuals (58.30% vs. 41.70%), with an OR = 3.28 (95%CI = 1.22 to 9.09) for CRC. In the patients' group, individuals harboring combined genotypes rs17429833 (GC) and rs72466472 (CC) (26% vs. 8.42%) showed an OR = 3.78 (95%CI = 1.33 to 11.48). Moreover, patients harboring GC genotype for SNV rs17429833 presented significantly association with well differentiated adenocarcinoma when compared to moderately differentiated adenocarcinoma [60% vs. 22.58%, OR = 6.3 (95%CI = 1.15 to 39.76)].

CONCLUSIONS

The GC genotype for the SNV rs17429833 or combined genotypes for SNVs rs17429833 (GC) and rs72466472 (CC) seems to be risk factors for patients with FCC in Brazilian patients; however, a larger number of patients needs to be evaluated to confirm our results.

Aberrant activation of hepatocyte growth factor/MET signaling promotes β-catenin-mediated prostatic tumorigenesis

Co-occurrence of aberrant hepatocyte growth factor (HGF)/MET proto-oncogene receptor tyrosine kinase (MET) and Wnt/β-catenin signaling pathways has been observed in advanced and metastatic prostate cancers. This co-occurrence positively correlates with prostate cancer progression and castration-resistant prostate cancer development. However, the biological consequences of these abnormalities in these disease processes remain largely unknown. Here, we investigated the aberrant activation of HGF/MET and Wnt/β-catenin cascades in prostate tumorigenesis by using a newly generated mouse model in which both murine Met transgene and stabilized β-catenin are conditionally co-expressed in prostatic epithelial cells. These compound mice displayed accelerated prostate tumor formation and invasion compared with their littermates that expressed only stabilized β-catenin. RNA-Seq and quantitative RT-PCR analyses revealed increased expression of genes associated with tumor cell proliferation, progression, and metastasis. Moreover, Wnt signaling pathways were robustly enriched in prostate tumor samples from the compound mice. ChIP-qPCR experiments revealed increased β-catenin recruitment within the regulatory regions of the Myc gene in tumor cells of the compound mice. Interestingly, the occupancy of MET on the Myc promoter also appeared in the compound mouse tumor samples, implicating a novel role of MET in β-catenin-mediated transcription. Results from implanting prostate graft tissues derived from the compound mice and controls into HGF-transgenic mice further uncovered that HGF induces prostatic oncogenic transformation and cell growth. These results indicate a role of HGF/MET in β-catenin-mediated prostate cancer cell growth and progression and implicate a molecular mechanism whereby nuclear MET promotes aberrant Wnt/β-catenin signaling-mediated prostate tumorigenesis.

Polymorphisms in CLDN1 are associated with age and differentiation of triple-negative breast cancer patients

Purpose: Triple-negative breast cancer (TNBC) is a highly heterogeneous disease. It is very important to explore novel biomarkers to better clarify the characteristics of TNBC. It has been reported that polymorphisms in claudin 1 (CLDN1) are associated with risk of several cancers. But till now, there is no report about these polymorphisms and TNBC. Patients and methods: Between January 2004 and December 2013, 267 patients with stage I-III primary TNBC were included in our study. We investigated the association between polymorphisms in CLDN1 gene and clinicopathological characteristics or survival of these patients. We used Haploview 4.2 software to identify Tag single nucleotide polymorphisms (SNPs). MassARRAY MALDI-TOF System was used for genotyping. Results: We found that rs10513846 GA genotype was associated with older age [P=0.013, hazard ratios (HR) = 2.231, 95% confidence interval (CI): 1.186-4.195]. Rs10513846 AA genotype carriers were more likely to develop grade 3 tumors (P=0.005, HR = 2.889, 95% CI: 1.389-6.007). And rs9283658 genotypes were also related to grade, more patients with grade 3 tumors were rs9283658 CC genotype carriers (P=0.023, HR = 0.446, 95% CI: 0.222-0.894). There was no association between polymorphisms in CLDN1 and survival of TNBC patients. After multivariate analysis, tumor size (P=0.021, HR = 3.146, 95% CI: 1.185-8.354) and lymph node status (P<0.001, HR = 10.930, 95% CI: 3.276-36.470) were demonstrated to be independent prognostic factors. Conclusion: We first demonstrated that polymorphisms in CLDN1 gene were associated with age and differentiation of TNBC patients.

Effects of claudin-1 downregulation on the physiological processes of gallbladder cancer SGC996 cells

Gallbladder cancer has a high recurrence and mortality rate, with limited treatment options. Therefore, elucidating the underlying molecular mechanisms of this disease would be beneficial to achieve an earlier diagnosis and potentially identify novel treatment targets. Claudin-1 is a tight junction protein associated with the development and prognosis of several types of cancer, and our preliminary studies have demonstrated that claudin-1 expression is elevated in gallbladder cancer tissues. Therefore, the aim of the present study was to investigate the effects of downregulating claudin-1 on the physiological processes of gallbladder cancer cells. The gallbladder cancer SGC996 cell line was transfected with claudin-1-RNA interference lentivirus (LV-CLDN1-RNAi) to downregulate claudin-1 expression, and the downstream effects on cell proliferation, the cell cycle, apoptosis and cell invasion were investigated. Following transfection with LV-CLDN1-RNAi, the results of an MTT assay revealed that downregulating claudin-1 did not affect the proliferation of the SGC996 cells. However, flow cytometry analysis demonstrated that the number of cells arrested in the G₁ phase increased significantly, whereas the amount of cells arrested in the S phase was significantly reduced. Annexin V-APC single-color staining demonstrated that downregulating claudin-1 expression increased the ratio of cell apoptosis, which was confirmed by the results of western blot analysis, in which levels of the pro-apoptotic B-cell lymphoma 2 (Bcl-2)-associated X protein and anti-apoptotic Bcl-2 protein were increased and decreased, respectively. Finally, a Transwell assay indicated that claudin-1 downregulation inhibited cell invasion. Overall, the results from the present study indicated that downregulating claudin-1 expression promoted the apoptosis of gallbladder cancer cells and inhibited cell invasion, indicating that claudin-1 may be involved in the recurrence and metastasis of gallbladder cancer. These insights provide theoretical and experimental foundations for considering claudin-1 as a novel target for the treatment of gallbladder cancer.

Activation of hepatocyte growth factor/MET signaling initiates oncogenic transformation and enhances tumor aggressiveness in the murine prostate

Emerging evidence has shown that the hepatocyte growth factor (HGF) and its receptor, MET proto-oncogene, receptor tyrosine kinase (MET), promote cell proliferation, motility, morphogenesis, and angiogenesis. Whereas up-regulation of MET expression has been observed in aggressive and metastatic prostate cancer, a clear understanding of MET function in prostate tumorigenesis remains elusive. Here, we developed a conditional Met transgenic mouse strain, H11 ^Met/+ :PB-Cre4, to mimic human prostate cancer cells with increased MET expression in the prostatic luminal epithelium. We found that these mice develop prostatic intraepithelial neoplasia after HGF administration. To further assess the biological role of MET in prostate cancer progression, we bred H11 ^Met/+ /Pten^LoxP/LoxP:PBCre4 compound mice, in which transgenic Met expression and deletion of the tumor suppressor gene Pten occurred simultaneously only in prostatic epithelial cells. These compound mice exhibited accelerated prostate tumor formation and invasion as well as increased metastasis compared with Pten^LoxP/LoxP:PB-Cre4 mice. Moreover, prostatic sarcomatoid carcinomas and lesions resembling the epithelial-to-mesenchymal transition developed in tumor lesions of the compound mice. RNA-Seq and qRT-PCR analyses revealed a robust enrichment of known tumor progression and metastasis-promoting genes in samples isolated from H11 ^Met/+ /Pten^LoxP/LoxP:PB-Cre4 compound mice compared with those from Pten^LoxP/LoxP:PB-Cre4 littermate controls. HGF-induced cell proliferation and migration also increased in mouse embryonic fibroblasts (MEFs) from animals with both Met transgene expression and Pten deletion compared with Pten-null MEFs. The results from these newly developed mouse models indicate a role for MET in hastening tumorigenesis and metastasis when combined with the loss of tumor suppressors.

Emerging clinical significance of claudin-7 in colorectal cancer: a review

Tight junctions (TJs) play an important role in maintaining cell polarity and regulating cell permeability. In recent years, many studies have shown that TJ proteins, especially claudin-7, are closely related to inflammation and the development of various malignant tumors. Claudin-7 plays a significant role in maintaining the physiological functions and pathological conditions of the TJ barrier. The dysregulation of claudin-7 plays a tumor suppressor role or conversely has carcinogenic effects in different target tissues or cells, but the exact underlying mechanism is still unclear. In this review, we will summarize the expression pattern of claudin-7 in tumors, focusing on the expression and regulation of claudin-7 in colorectal cancer and discussing the correlation between claudin-7 and invasion, metastasis and epithelial–mesenchymal transition (EMT) in colorectal cancer. The construction of Cldn7^−/− mice and conventional claudin-7 knockout mouse models has helped determine the mechanisms by which claudin-7 promotes tumorigenesis. Elucidation of the expression and subcellular localization of claudin-7 under pathological conditions will help develop claudin-7 as a useful biomarker for detecting and diagnosing cancer, and thus may help combat the occurrence, development, and invasion of cancers.

Prognostic value of lymph node metastasis in patients with T1-stage colorectal cancer from multiple centers in China

AIM

To explore the features and prognostic value of lymph node metastasis in patients with T1-stage colorectal cancer (CRC).

METHODS

In all, 321 cases of T1-stage CRC were selected from 10132 patients with CRC who received surgical therapy in six large-scale hospitals in China and were retrospectively analyzed. Univariate and multivariate analyses were performed to analyze the risk factors for lymphatic metastasis. A survival analysis was then performed to analyze the prognostic value of lymph node metastasis.

RESULTS

The occurrence rate of T1 stage was 3.17% (321/10132); of these patients, the lymph node metastasis rate was 8.41% (27/321), and the non-lymph node metastasis rate was 91.59% (294/321). Univariate analysis showed that preoperative serum CEA, preoperative serum CA199, preoperative serum CA724, vascular invasion, and degree of differentiation were associated with lymph node metastasis in T1-stage CRC (P < 0.05 for all). Multivariate analysis indicated that preoperative serum CA724, vascular invasion, and degree of differentiation were closely related to lymph node metastasis (P < 0.05 for all). Log-rank survival analysis showed that age, preoperative serum CEA, preoperative serum CA199, vascular invasion, degree of differentiation, and lymph node metastasis (χ² = 24.180, P < 0.001) were predictors of 5-year overall survival (OS) (P < 0.05 for all). COX regression analysis demonstrated that preoperative serum CA199 and lymph node metastasis (HR = 5.117; P < 0.05; 95%CI: 0.058-0.815) were independent prognostic indicators of 5-year OS in patients with T1-stage CRC (P < 0.05 for both).

CONCLUSION

The morbidity of T1-stage CRC was 3.17% for all CRC cases. Preoperative serum CA724, vascular invasion, and degree of differentiation are independent risk factors for lymph node metastasis. Lymph node metastasis is an independent prognostic factor for OS in patients with T1-stage CRC.

3'UTR Polymorphism in ACSL1 Gene Correlates with Expression Levels and Poor Clinical Outcome in Colon Cancer Patients

Strong evidence suggests that lipid metabolism (LM) has an essential role in tumor growth to support special energetic and structural requirements of tumor cells. Recently, overexpression of LM-related genes, apolipoproteins related to metabolic syndrome, and ACSL/SCD network involved in fatty acid activation have been proposed as prognostic markers of colon cancer (CC). Furthermore, activation of this latter lipid network has been recently demonstrated to confer invasive and stem cell properties to tumor cells promoting tumor aggressiveness and patient relapse. With the aim of elucidating whether any genetic variation within these genes could influence basal expression levels and consequent susceptibility to relapse, we genotype, in 284 CC patients, 57 polymorphisms located in the 7 genes of these lipid networks previously associated with worse clinical outcome of CC patients (ABCA1, ACSL1, AGPAT1, APOA2, APOC1, APOC2 and SCD), some of them related to CC aggressiveness. After adjusting with clinical confounding factors and multiple comparisons, an association between genotype and disease-free survival (DFS) was shown for rs8086 in 3'-UTR of ACSL1 gene (HR 3.08; 95% CI 1.69-5.63; adjusted p = 0.046). Furthermore, the risk T/T genotype had significantly higher ACSL1 gene expression levels than patients carrying C/T or C/C genotype (means = 5.34; 3.73; 2.37 respectively; p-value (ANOVA) = 0.019), suggesting a functional role of this variant. Thus, we have identified a "risk genotype" of ACSL1 gene that confers constitutive high levels of the enzyme, which is involved in the activation of fatty acids through conversion to acyl-CoA and has been recently related to increased invasiveness of tumor cells. These results suggest that rs8086 of ACSL1 could be a promising prognostic marker in CC patients, reinforcing the relevance of LM in the progression of CC.

Identification of Claudin 1 Transcript Variants in Human Invasive Breast Cancer

BACKGROUND

The claudin 1 tight junction protein, solely responsible for the barrier function of epithelial cells, is frequently down regulated in invasive human breast cancer. The underlying mechanism is largely unknown, and no obvious mutations in the claudin 1 gene (CLDN1) have been identified to date in breast cancer. Since many genes have been shown to undergo deregulation through splicing and mis-splicing events in cancer, the current study was undertaken to investigate the occurrence of transcript variants for CLDN1 in human invasive breast cancer.

METHODS

RT-PCR analysis of CLDN1 transcripts was conducted on RNA isolated from 12 human invasive breast tumors. The PCR products from each tumor were resolved by agarose gel electrophoresis, cloned and sequenced. Genomic DNA was also isolated from each of the 12 tumors and amplified using PCR CLDN1 specific primers. Sanger sequencing and single nucleotide polymorphism (SNP) analyses were conducted.

RESULTS

A number of CLDN1 transcript variants were identified in these breast tumors. All variants were shorter than the classical CLDN1 transcript. Sequence analysis of the PCR products revealed several splice variants, primarily in exon 1 of CLDN1; resulting in truncated proteins. One variant, V1, resulted in a premature stop codon and thus likely led to nonsense mediated decay. Interestingly, another transcript variant, V2, was not detected in normal breast tissue samples. Further, sequence analysis of the tumor genomic DNA revealed SNPs in 3 of the 4 coding exons, including a rare missense SNP (rs140846629) in exon 2 which represents an Ala124Thr substitution. To our knowledge this is the first report of CLDN1 transcript variants in human invasive breast cancer. These studies suggest that alternate splicing may also be a mechanism by which claudin 1 is down regulated at both the mRNA and protein levels in invasive breast cancer and may provide novel insights into how CLDN1 is reduced or silenced in human breast cancer.

Tight Junctions and the Tumor Microenvironment

PURPOSE OF REVIEW

Tight junctions (TJs) are specialized differentiations of epithelial and endothelial cell membranes. TJs play an important role in the adhesion of cells and their interaction with each other. Most cancers originate from epithelial cells. Thus, it is of significance to examine the role of TJs in the tumor microenvironment (TME) and how they affect cancer metastasis.

RECENT FINDINGS

In epithelium-derived cancers, intactness of the primary tumor mass is influenced by intercellular structures as well as cell-to-cell adhesion. Irregularities of these factors may lead to tumor dissociation and subsequent metastasis. Low expression of TJs is observed among highly metastatic cancer cells.

SUMMARY

In this review, we summarized findings from current literature in consideration of the role of TJs in relation to the TME and cancer. Deeper understanding of the mechanisms leading to TJ dysregulation is needed to facilitate the design and conceptualization of new and better therapeutic strategies for cancer.

Genetic markers of recurrence in colorectal cancer

Colorectal cancer (CRC) worldwide belongs to one of the most frequent cancers affecting both genders. Surgery and 5-fluorouracil-based adjuvant chemotherapy are recommended for patients with high-risk stage II and stage III colon carcinoma. Mutations of genes encoding for specific proteins may have an impact on the time to recurrence. These proteins act over specific signaling pathways, are implicated in metabolic processes and regulate the cell cycle. Though many retrospective studies show strong associations between genetic mutations and the clinical outcome of patients with CRC, currently no validated biomarkers are used in clinical routine settings. Therefore, large prospective validation studies should be carried out in order to strengthen the position of genetic mutations in personalized treatment of patients with CRC.

Single-Nucleotide Polymorphisms of Tight Junction Component Claudin-1 Associated with Leukoaraiosis

BACKGROUND

The blood-brain barrier (BBB) plays a major role in the development of leukoaraiosis (LA). The junctional complex of BBB consists of tight junction (TJ) and adherens junction (AJ). Claudin-1 is the integral component of TJ. The aim of this study was to evaluate whether genetic variations in claudin-1 gene are associated with the development of LA.

METHODS

LA has to be diagnosed based on images. A total of 228 LA cases and 203 controls were enrolled from the individuals who underwent brain magnetic resonance imaging with obtainable vascular risk factors. Genotyping of claudin-1 single-nucleotide polymorphisms (SNPs) (rs17501010, rs893051, and rs9290927) was performed by real-time polymerase chain reaction with LightSNiP reagents (coupled primer and probe) and FastStart DNAMaster HybProbe (Roche Diagnostic, GmBH, Mannheim, Germany) in LightCycler 2.0.

RESULTS

Among the 3 SNPs of claudin-1, a significant genetic difference was found only between control and LA (both LA-periventricular white matter [PVWM] and LA-subcortical deep white matter) with SNP rs9290927. However, their haplotypes G-G-T and G-C-A were significantly different between LA-PVWM and control, which increase the development of LA-PVWM with odds ratios of 1.45 and .57, respectively.

CONCLUSIONS

This study demonstrated first evidence of genetic polymorphism of TJ component claudin-1 and their haplotypes associated with LA.