Gaoxiang Ma

Genetic variants in lncRNA HOTAIR are associated with risk of colorectal cancer

Long non-coding RNA HOX transcript antisenseRNA (HOTAIR) has been widely identified to participate in tumour pathogenesis, acting as a promoter in colorectal cancer carcinogenesis. However, the association between genetic variants in HOTAIR and cancer risk has not yet been reported. In the present study, we performed a two-stage case-control study to investigate the association between HOTAIR tagSNPs and the risk of colorectal cancer. We found that individuals with rs7958904 CC genotype had a significantly decreased risk of colorectal cancer in both Stage 1 and 2, compared with those carrying GG genotype [odds ratio (OR) = 0.70, 95% confidence interval (CI) = 0.51-0.97 in Stage 1; OR = 0.58, 95% CI = 0.37-0.91 in Stage 2; OR = 0.67, 95% CI = 0.51-0.87 in combined stage]. The subsequently stratified analyses showed that the protective effect of rs7958904 was more pronounced in several subgroups. In summary, our study showed that genetic variants in HOTAIR were associated with risk of colorectal cancer and rs7958904 may act as a potential biomarker for predicting the risk of colorectal cancer.

The association analysis of lncRNA HOTAIR genetic variants and gastric cancer risk in a Chinese population.

The HOX transcript antisense intergenic RNA (HOTAIR), a well-known long noncoding RNA, is involved in pathogenesis and progress of multiple tumors. Its ectopic expression and biological functions have been observed in gastric cancer. In this study, we conducted a two-stage case-control study to evaluate whether genetic variations of HOTAIR were associated with gastric cancer risk. We identified that a single nucleotide polymorphism (SNP) rs4759314 was significantly associated with the increased gastric cancer risk with an odds ratio (OR) of 1.39 [95% confidence interval (CI) = 1.13–1.71, P = 0.002] in the combined sets. Further functional experiments revealed the allele-specific effects on HOTAIR and HOXC11 expressions in gastric cancer tissues, of which HOTAIR and HOXC11 expressions of individuals carrying with AG genotype were much higher than those with AA genotype; similarly, the effects occurred in intronic promoter activities, of which the promoter activity of G allele was more pronounced than that of A allele. Interestingly, we identified a novel potential oncogene HOXC11 in gastric cancer pathogenesis with differential expression in gastric cancer tissues by association analysis with candidate gene strategy. These results suggest that SNP rs4759314 of HOTAIR acts as a potential biomarker for predicting gastric cancer, and the role of HOXC11 in gastric cancer etiology is warranted to further investigation.

Genome-wide analysis of long noncoding RNA signature in human colorectal cancer.

Long noncoding RNAs (lncRNAs) have been widely regarded as crucial regulators in various biological processes involved in carcinogenesis. However, the comprehensive lncRNA expression signature in colorectal cancer remains fully unknown. We performed a high throughput microarray assay to detect lncRNA expression profile in three paired human colorectal cancer tissues and their adjacent normal tissues. Additional 90 paired colorectal samples were collected to verify differently expression levels of two selected lncRNAs using q-RT-PCR assay. Bioinformatic approaches were performed to explore into the functions of these differently expressed lncRNAs. Microarray assay showed a series of lncRNAs were differently expressed in colorectal cancer. Two of the lncRNAs, HOTAIR and a novel lncRNA, lncRNA-422 were confirmed in more samples (P=0.015 for HOTAIR and P=0.027 for lncRNA-422, respectively). GSEA indicated that gene sets most correlated with them were those named up-regulated in KRAS-over, down-regulated in JAK2-knockout, down-regulated in PDGF-over and down-regulated in TBK1-knockout, all of which were cancer-related. Subsequently, GO analyses of most significantly correlated coding genes of HOTAIR and lncRNA-422 showed that these two lncRNAs may participate in carcinogenesis by regulating protein coding genes involved in special biological process relevant to cancer. Our study demonstrated that different lncRNA expression patterns were involved in colorectal cancer. Besides, HOTAIR and lncRNA-422 were identified to participate in colorectal cancer. Further studies into biological mechanisms of differently expressed lncRNAs identified in our study will help to provide new perspective in colorectal cancer pathogenesis.

Genetic variant in 8q24 is associated with prognosis for gastric cancer in a Chinese population.

Single nucleotide polymorphisms (SNPs) located in long noncoding RNA CASC8 gene may influence the process of splicing and stability of messenger RNA conformation, resulting in the modification of its interacting partners. Genome‐wide association studies have identified the SNP rs10505477 and SNP rs1562430 in CASC8 were associated with risk of the colorectal cancer (CRC) and breast cancer, respectively.

miR-107 regulates tumor progression by targeting NF1 in gastric cancer

Our previous genome-wide miRNA microarray study revealed that miR-107 was upregulated in gastric cancer (GC). In this study we aimed to explore its biological role in the pathogenesis of GC. Integrating in silico prediction algorithms with western blotting assays revealed that miR-107 inhibition enhanced NF1 (neurofibromin 1) mRNA and protein levels, suggesting that NF1 is one of miR-107 targets in GC. Luciferase reporter assay revealed that miR-107 suppressed NF1 expression by binding to the first potential binding site within the 3′-UTR of NF1 mRNA. mRNA stable assay indicated this binding could result in NF1 mRNA instability, which might contribute to its abnormal protein expression. Functional analyses such as cell growth, transwell migration and invasion assays were used to investigate the role of interaction between miR-107 and its target on GC development and progression. Moreover, We investigated the association between the clinical phenotype and the status of miR-107 expression in 55 GC tissues, and found the high expression contributed to the tumor size and depth of invasion. The results exhibited that down regulation of miR-107 opposed cell growth, migration, and invasion, whereas NF1 repression promoted these phenotypes. Our findings provide a mechanism by which miR-107 regulates NF1 in GC, as well as highlight the importance of interaction between miR-107 and NF1 in GC development and progression.

Functional POR A503V is associated with the risk of bladder cancer in a Chinese population

Human cytochrome P450 oxidoreductase (POR) plays important roles in the metabolism of exogenous carcinogens and endogenous sterol hormones. However, few studies have explored the association between POR variants and the risk of bladder cancer. In this study, we first sequenced all 16 POR exons among 50 randomly selected controls, and found three variants, rs1135612, rs1057868 (A503V) and rs2228104, which were then assessed the relation to risk of bladder cancer in a case-control study of 1,050 bladder cancer cases and 1,404 cancer-free controls in a Chinese population. People with A503V TT genotype have a decreased risk of bladder cancer in a recessive model (TT vs. CC/CT, OR = 0.73, 95% CI = 0.57–0.93), which was more pronounced among elderly male, non-smoking, subjects. Especially, A503V TT genotype showed a protective effect in the invasive tumor stage. Functional analysis revealed that A503V activity decreased in cytochrome c reduction (50.5 units/mg vs. 135.4 units/mg), mitomycin C clearance (38.3% vs. 96.8%), and mitomycin C-induced colony formation (78.0 vs 34.3 colonies per dish). The results suggested that POR A503V might decrease the risk of bladder cancer by reducing its metabolic activity, and should be a potential biomarker for predicting the susceptibility to human bladder cancer.

Rare variants in BRCA2 and CHEK2 are associated with the risk of urinary tract cancers

Previous studies have shown that two rare variants, rs11571833 in BRCA2 and rs17879961 in CHEK2 were associated with lung cancer. However, the associations between these two variants and urinary tract cancers risk remain largely unexplored. We applied imputation of three genome-wide association studies published in the database of Genotypes and Phenotypes (dbGaP). Unconditional logistic regression analysis and meta-analysis were performed to assess the association between these two variants and the risk of urinary tract cancers. Our results showed that rs11571833[T] had an effect on urinary tract cancers predisposition (ORmeta = 1.45, Pmeta = 0.013), especially associated with increased the risk of bladder cancer (ORmeta = 1.60, Pmeta = 0.010). Moreover, rs17879961[C] had a protective effect on the urinary tract cancers (ORmeta = 0.67, Pmeta = 1.0 × 10−3) and was mostly associated with a lower incidence of renal cell carcinoma (ORmeta = 0.51, Pmeta = 2.0 × 10−3). Together, our study indicates that BRCA2 and CHEK2 play an important role in the genetic susceptibility to urinary tract cancers.

The association analysis of hOGG1 genetic variants and gastric cancer risk in a Chinese population.

Human 8-oxoguanine DNA glycosylase (hOGG1) is known to play an important role in the prevention of carcinogenesis, including gastric cancer (GC). We performed a case-control study to investigate whether single nucleotide polymorphisms (SNPs) of hOGG1 are associated with GC risk in a Chinese population. Two potential functional tagSNPs (rs159153 and rs1052133) and a previously reported risk SNP (rs125701) were genotyped in 1,275 GC patients and 1,436 controls. We found that SNP rs125701 G > A was significantly associated with the increased GC risk [adjusted odds ratio (OR) = 1.38, 95% confidence interval (CI) = 1.05-1.79 in additive model]. Besides, the functional studies demonstrated that the minor A allele of rs125701 significantly reduced the transcriptional activity of hOGG1 promoter and enhanced the methylation level of CpG site of cg15357639. In conclusion, our results suggested that the SNP rs125701 in hOGG1 promoter was associated with the elevated GC risk, which could act as a new potential biomarker for GC susceptibility. Further functional verification of rs125701 in GC pathogenesis is warranted.

KCNMA1 cooperating with PTK2 is a novel tumor suppressor in gastric cancer and is associated with disease outcome

BackgroundInactivation of tumor suppressor genes by promoter hypermethylation plays a key role in the tumorgenesis. It is necessary to uncover the detailed pattern of whole genome-wide abnormal DNA methylation during the development of gastric cancer (GC).MethodWe performed a genome-wide methylation detection using 12 paired of GC tissues and their corresponding normal tissues. Methylation-specific PCR (MSP) and bisulphite sequencing (BSP) were used to measure methylation status of specific CpG site. Based on the bioinformatic analysis, the cell phenotypes and mouse model experiments were constructed to detect effect of the target gene. Using the Kaplan–Meier survival curve, the clinical value of KCNMA1 was assessed in GC patients.ResultsThe CpG site cg24113782 located at the promoter of KCNMA1 showed the most significant difference, contributing to the commonly silenced KCNMA1in gastric cancer cells and primary GC tissues. The promoter methylation of KCNMA1 was detected in 68.7% (77/112) of tumor tissues, compared with 16.2% (18/112) of normal tissues (P < 0.001). The survival curve indicated that KCNMA1 hypermethylation was significantly associated with the shortened survival in GC patients (P = 0.036). KCNMA1 significantly inhibited biological malignant behavior of gastric cancer cell by inducing cell apoptosis in vitro, and suppressed xenograft tumor growth in subcutaneous mouse models (both P < 0.001). Furthermore, the anti-tumor effect of KCNMA1was mediated through suppressing the expression of PTK2.ConclusionKCNMA1 is a critical tumor suppressor in gastric carcinogenesis and its hypermethylation is an independent prognostic factor in patients with gastric cancer.

Evaluation of genome-wide genotyping concordance between tumor tissues and peripheral blood

Tumor tissues were potential resources in cancer susceptibility studies. To assess the genotyping concordance between tumor tissues and peripheral blood, we conducted this study in a large sample size and genome-wide scale. Genome-wide genotypes of human colon adenocarcinoma (COAD) retrieved from The Cancer Genome Atlas (TCGA) was analyzed. A total of 387 pairs of matched fresh frozen tumor tissues and peripheral blood samples passed the quality control processes. High concordant rate (94.85% with no-calls and 97.89% without no-calls) was found between tumor tissues and peripheral blood. The discordant rate raised with the increase of heterozygote rate, and the tendency was statistically significant. The total missing rate was 3.10%. We also verified 14 susceptibility SNPs and the average genotyping concordant rate was 97.42%. These findings suggest that majority of SNPs could be accurately genotyped using DNA isolated from tumor tissues.