A polymorphic minisatellite region of BORIS regulates gene expression and its rare variants correlate with lung cancer susceptibility

Association between PDCD6-VNTR polymorphism and urinary cancer susceptibility

BACKGROUND

Programmed cell death 6 (PDCD6) is known to be involved in apoptosis and tumorigenesis. Given the reported association with urinary cancer susceptibility through SNP analysis, we further analyzed the entire genomic structure of PDCD6.

METHODS

Three VNTR regions (MS1-MS3) were identified through the analysis of the genomic structure of PDCD6. To investigate the association between these VNTR regions and urinary cancer susceptibility, genomic DNA was extracted from 413 cancer-free male controls, 267 bladder cancer patients, and 331 prostate cancer patients. Polymerase chain reaction (PCR) was performed to analyze the PDCD6-MS regions. Statistical analysis was performed to determine the association between specific genotypes and cancer risk. In addition, the effect of specific VNTRs on PDCD6 expression was also confirmed using a reporter vector.

RESULTS

Among the three VNTR regions, MS1 and MS2 exhibited monomorphism, while the MS3 region represented polymorphism, with its transmission to subsequent generations through meiosis substantiating its utility as a DNA typing marker. In a case-control study, the presence of rare alleles within PDCD6-MS3 exhibited significant associations with both bladder cancer (OR = 2.37, 95% CI: 1.33-4.95, P = 0.019) and prostate cancer (OR = 2.11, 95% CI: 1.03-4.36, P = 0.038). Furthermore, through luciferase assays, we validated the impact of the MS3 region on modulating PDCD6 expression.

CONCLUSIONS

This study suggests that the PDCD6-MS3 region could serve as a prognostic marker for urinary cancers, specifically bladder cancer and prostate cancer. Moreover, the subdued influence exerted by PDCD6-MS3 on the expression of PDCD6 offers another insight concerning the progression of urinary cancer.

BORIS variant SF2(C2/A4) promotes the malignant development of liver cancer by activating epithelial-mesenchymal transition and hepatic stellate cells

The underlying mechanisms of metastasis and recurrence of liver cancer remain largely unknown. Here, we found that Brother of the Regulator of Imprinted Sites (BORIS) variant SF2(C2/A4) was highly expressed in high metastatic potential hepatocellular carcinoma (HCC) cells and clinical tumor samples, related to the formation of satellite nodules. Its over expression promoted self-renewal, the expression of tumor stem cell markers, chemoresistance, wound healing rate, invasion and metastasis of HepG2 and Hep3B cells; reinforced epithelial-mesenchymal transition (EMT), decreased the expression of E-cadherin and increased N-cadherin and Vimentin. Subcellular localization experiment showed that BORIS SF2(C2/A4) was localized in nucleus and cytoplasm. Further double luciferase reporter gene experiment confirmed that it bound to TWIST1 gene promoter and significantly increased latter expression. BORIS SF2(C2/A4) knock down induced apoptosis of HCCLM3 and PLC/PRF/5 cells, and increased the protein content of cleaved caspase 3. Additionally, BORIS SF2(C2/A4) over expression increased the expression of fibroblast growth factor 2 (FGF2) in HepG2 and Hep3B cells. FGF2 expressed higher in HCC tumor tissues than in paired peri-tumor tissues, and its expression was positively correlated with BORIS SF2(C2/A4). Interestingly, high expression of FGF2 is also associated with the formation of satellite nodules. Moreover, using the medium from BORIS SF2(C2/A4) overexpressed cell lines to coculture hepatic stellate cell (HSCs) line LX-2, the latter could be activated and increased the expression of CD90 and PIGF, which is consistent with the effect of adding bFGF alone. These results indicate that BORIS SF2(C2/A4) plays a role in deterioration of liver cancer by regulating TWIST1 to induce EMT, and by FGF2 to activate HSCs.

The function of brother of the regulator of imprinted sites in cancer development

As Douglas Hanahan and Robert Weinberg compiled, there are nine hallmarks of cancer that are conducive to cancer cell development and survival. Previous studies showed that brother of the regulator of imprinted sites (BORIS) might promote cancer progression through these aspects. The competition between BORIS and CCCTC-binding factor (CTCF), which is crucial in the formation of chromatin loops, affects the normal function of CTCF and leads to neoplasia and deformity. In addition, BORIS belongs to the cancer-testis antigen families, which are potential targets in cancer diagnosis and treatment. Herein, we discuss the function and mechanisms of BORIS, especially in cancer development.

Rare minisatellite alleles of MUC2-MS8 influence susceptibility to rectal carcinoma

BACKGROUND

Previously, we identified eight novel minisatellites in the MUC2, of which allelic variants in MUC2-MS6 were examined to influence susceptibility to gastric cancer. However, studies on the susceptibility to gastrointestinal cancer of other minisatellites in the MUC2 region still remain unprogressive.

OBJECTIVE

In this study, we investigated whether polymorphic variations in the MUC2-MS8 region are related to susceptibility to gastrointestinal cancer.

METHODS

We assessed the association between MUC2-MS8 and gastrointestinal cancers by a case-control study with 1229 controls, 486 gastric cancer cases, 220 colon cancer cases and 278 rectal cancer cases. To investigate whether intronic minisatellites affect gene expression, various minisatellites were inserted into the luciferase-reporter vector and their expression levels were examined. We also examined the length of MUC2-MS8 alleles in blood and cancer tissue matching samples of 107 gastric cancer patients, 125 colon cancer patients, and 85 rectal cancer patients, and investigated whether the repeat sequence affects genome instability.

RESULTS

A statistically significant association was identified between rare MUC2-MS8 alleles and the occurrence of rectal cancer: odds ratio (OR), 6.66; 95% confidence interval (CI), 1.11-39.96; and P = 0.0165. In the younger group (age, < 55), rare alleles were significant associated with an increased risk of rectal cancer (odds ratio, 24.93 and P = 0.0001). Suppression of expression was found in the reporter vector inserted with minisatellites, and loss of heterozygosity (LOH) of the MUC2-MS8 region was confirmed in cancer tissues of gastrointestinal cancer patients (0.8-5.9%).

CONCLUSION

Our results suggest that the rare alleles of MUC2-MS8 could be used to identify the risk of rectal cancer and that this repeat region is related to genomic instability.

Genome-wide characterization of human minisatellite VNTRs: population-specific alleles and gene expression differences

Variable Number Tandem Repeats (VNTRs) are tandem repeat (TR) loci that vary in copy number across a population. Using our program, VNTRseek, we analyzed human whole genome sequencing datasets from 2770 individuals in order to detect minisatellite VNTRs, i.e., those with pattern sizes ≥7 bp. We detected 35 638 VNTR loci and classified 5676 as commonly polymorphic (i.e. with non-reference alleles occurring in >5% of the population). Commonly polymorphic VNTR loci were found to be enriched in genomic regions with regulatory function, i.e. transcription start sites and enhancers. Investigation of the commonly polymorphic VNTRs in the context of population ancestry revealed that 1096 loci contained population-specific alleles and that those could be used to classify individuals into super-populations with near-perfect accuracy. Search for quantitative trait loci (eQTLs), among the VNTRs proximal to genes, indicated that in 187 genes expression differences correlated with VNTR genotype. We validated our predictions in several ways, including experimentally, through the identification of predicted alleles in long reads, and by comparisons showing consistency between sequencing platforms. This study is the most comprehensive analysis of minisatellite VNTRs in the human population to date.

Brother of regulator of imprinted sites inhibits cisplatin-induced DNA damage in non-small cell lung cancer

Cisplatin (DDP) chemotherapy is the primary modality of treatment for non-small cell lung cancer (NSCLC). However, due to the occurrence of DDP resistance, only a limited number of patients benefit from this treatment regimen. Brother of Regulator of Imprinted Sites (BORIS) is expressed elevated in NSCLC. Whether BORIS is involved in the DDP resistance of NSCLC is currently undetermined. The association between BORIS expression and overall survival rate of 156 patients with NSCLC who received DDP chemotherapy was analyzed in the present study. In order to investigate the function of BORIS in DDP chemotherapy, BORIS was silenced or overexpressed in four NSCLC cell lines. The cell viabilities, apoptosis and DNA damage induced by DDP were evaluated in these cell lines. In addition, the regulations of DNA repair genes were assessed, including POLH, ERCC1, BRCA1, MSH6 and XPA. The present study demonstrated that high BORIS expression was associated with decreased overall survival rate in patients with NSCLC who received DDP chemotherapy. The patients who benefited and went into remission following DDP therapy expressed a relatively low level of BORIS, suggesting the potential function of BORIS in DDP resistance. Cell experiments revealed that NSCLC cells that had a higher proliferation rate and resisted DDP treatment expressed a relatively higher level of BORIS. Knockdown of BORIS in NSCLC cells induced DNA damage; inhibiting cell proliferation and sensitizing cells to DDP treatment. In contrast, BORIS overexpression suppressed DDP-induced DNA damage. Notably, the mismatch repair factor mutS homolog 6 (MSH6) was regulated by BORIS, indicating its association with BORIS-associated DDP resistance in NSCLC. The findings of the present study suggest that BORIS suppresses DNA damage and promotes the progression of NSCLC and DDP resistance. The present study indicates the potential application of BORIS in NSCLC therapy and prognosis.

Short rare minisatellite variant of BORIS-MS2 is related to bladder cancer susceptibility

BACKGROUND

BORIS/CTCFL, a paralog of CTCF and member of the cancer-testicular antigen family, is abnormally activated in multiple cancers.

OBJECTIVE

We investigated the relationship between polymorphic variants of the BORIS minisatellite 2 (BORIS-MS2), located within the 5' upstream promoter region of BORIS, and bladder cancer.

METHODS

We used case-control study with 516 controls and 113 bladder cancer patients. To evaluate whether minisatellite variants play a role in BORIS expression, we examined the transcript levels of a reporter gene linked to these minisatellites in cell lines. We also examined BORIS expression in cancerous and non-cancerous bladder tissue.

RESULTS

A statistically significant association was identified between the short rare allele (13-repeat) and bladder cancer incidence (odds ratio (OR) 2.97, 95% confidence interval (CI) [1.14, 7.74]; P = 0.020). In particular, short rare alleles in the younger group (aged < 65) were associated with statistically significant increase in bladder cancer risk (OR 5.38, CI [1.32, 21.87]; P = 0.01). The BORIS-MS2 region acted as a negative regulator, and the expression level of the luciferase reporter in bladder cancer cells was less effectively inhibited than in normal cells. Furthermore, the expression of BORIS mRNA significantly differed (P < 0.05) between normal and cancerous muscle-invasive bladder cancer tissues, and relationship to clinical parameters was observed.

CONCLUSIONS

The short rare allele of BORIS-MS2 could be used to identify bladder cancer risk. BORIS expression levels have been shown to increase with the progression of bladder cancer, could be used as a biomarker for its progression.

Brother of Regulator of Imprinted Sites (BORIS) suppresses apoptosis in colorectal cancer

Identifying oncogenes that promote cancer cell proliferation or survival is critical for treatment of colorectal cancer. The Brother of Regulator of Imprinted Sites (BORIS) is frequently expressed in most types of cancer, but rarely in normal tissues. Aberrantly expressed BORIS relates to colorectal cancer, but its function in colorectal cancer cells remains unclear. In addition, previous studies indicated the significance of cytoplasm-localized BORIS in cancer cells. However, none of them investigated its function. Herein, we investigated the functions of BORIS in cancer cell proliferation and apoptosis and the role of cytoplasm-localized BORIS in colorectal cancer. BORIS expression correlated with colorectal cancer proliferation. BORIS overexpression promoted colorectal cancer cell growth, whereas BORIS knockdown suppressed cell proliferation. Sensitivity of colorectal cancer cells to 5-fluorouracil (5-FU) was inversely correlated with BORIS expression. These data suggest that BORIS functions as an oncogene in colorectal cancer. BORIS silencing induced reactive oxygen species (ROS) production and apoptosis, whereas BORIS supplementation inhibited apoptosis induced by BORIS short interfering RNA (siRNA), hydrogen peroxide (H₂O₂) or 5-FU. Introduction of BORIS-ZFdel showed that cytoplasmic localization of BORIS inhibited apoptosis but not ROS production. Our study highlights the anti-apoptotic function of BORIS in colorectal cancer.