Liqing Zhou

Silencing of Long Noncoding RNA MALAT1 by miR-101 and miR-217 Inhibits Proliferation, Migration, and Invasion of Esophageal Squamous Cell Carcinoma Cells

Background: MALAT1, a highly conserved long non-coding RNA (lncRNA), acts as oncogene in multiple human cancers. Results: miR-101 and miR-217 can silence MALAT1 expression and then inhibit esophageal cancer proliferation, migration and invasion. Conclusion: Tumor suppressor miR-101 and miR-217 can negatively regulate MALAT1 expression. Significance: These data provide a new mechanism for MALAT1 regulation. MALAT1, a highly conserved long noncoding RNA, is deregulated in several types of cancers. However, its role in esophageal squamous cell carcinoma (ESCC) and its posttranscriptional regulation remain poorly understood. In this study we provide first evidences that a posttranscriptional regulation mechanism of MALAT1 by miR-101 and miR-217 exists in ESCC cells. This posttranscriptional silencing of MALAT1 could significantly suppress the proliferation of ESCC cells through the arrest of G2/M cell cycle, which may be due to MALAT1-mediated up-regulation of p21 and p27 expression and the inhibition of B-MYB expression. Moreover, we also found the abilities of migration and invasion of ESCC cells were inhibited after overexpression of miR-101, miR-217, or MALAT1 siRNA. This might be attributed to the deregulation of downstream genes of MALAT1, such as MIA2, HNF4G, ROBO1, CCT4, and CTHRC1. A significant negative correlation exists between miR-101 or miR-217 and MALAT1 in 42 pairs of ESCC tissue samples and adjacent normal tissues. Mice xenograft data also support the tumor suppressor role of both miRNAs in ESCCs.

The identification of an ESCC susceptibility SNP rs920778 that regulates the expression of lncRNA HOTAIR via a novel intronic enhancer

Long noncoding RNA (lncRNA) HOX transcript antisense RNA (HOTAIR), which could induce genome-wide retargeting of polycomb-repressive complex 2, trimethylates histone H3 lysine-27 (H3K27me3) and deregulation of multiple downstream genes, is involved in development and progression of esophageal squamous cell carcinoma (ESCC). We hypothesized that the functional single nucleotide polymorphisms (SNP) in HOTAIR may affect HOTAIR expression and/or its function and, thus, ESCC risk. Therefore, we examined the association between three haplotype-tagging SNPs (htSNP) across the whole HOTAIR locus and ESCC risk as well as the functional relevance of an ESCC susceptibility SNP rs920778. Genotypes were determined in three independent case-control sets consisted of 2098 ESCC patients and 2150 controls. The allele-specific regulation on HOTAIR expression by the rs920778 SNP was investigated in vitro and in vivo. We found that the HOTAIR rs920778 TT carriers had a 1.37-fold, 1.78-fold and 2.08-fold increased ESCC risk in Jinan, Shijiazhuang and Huaian populations, respectively, compared with the CC carriers (P = 0.003, 7.7 × 10(-4) and 5.9 × 10(-4)). During inspecting functional relevance of the rs920778 SNP, we identified a novel intronic HOTAIR enhancer locating between +1719bp and +2353bp from the transcriptional start site through reporter assays. Moreover, there is an allelic regulation of rs920778 on HOTAIR expression via this enhancer in both ESCC cell lines and normal esophageal tissue specimens, with higher HOTAIR expression among T allele carriers. These results demonstrate that functional genetic variants influencing lncRNA regulation may explain a fraction of ESCC genetic basis.

Functional FEN1 genetic variants contribute to risk of hepatocellular carcinoma, esophageal cancer, gastric cancer and colorectal cancer

As a DNA repair protein, Flap endonuclease 1 (FEN1) plays crucial parts in preventing carcinogenesis. Two functional germ line variants (-69G > A and 4150G > T) in the FEN1 gene have been associated with DNA damage levels in coke oven workers and lung cancer risk in general populations. However, the role of these genetic variants on gastrointestinal cancer susceptibility is unknown. Therefore, we evaluated the association between these polymorphisms and gastrointestinal cancer risk in two independent case-control cohorts consisted of a total of 1850 gastrointestinal cancer (hepatocellular carcinoma, esophageal cancer, gastric cancer and colorectal cancer) patients and 2222 healthy controls. The impact of these variations on FEN1 expression was also examined using liver, esophagus, stomach and colon normal tissues. It was found that the FEN1 -69GG genotypes were significantly correlated to increased risk for developing gastrointestinal cancer compared with the -69AA genotype in both cohorts [Jinan cohort: odds ratios (OR) = 2.14, 95% confidence interval (CI) = 1.47-2.80, P = 1.0 × 10(-)(6); Huaian cohort: OR = 1.93, 95% CI = 1.37-2.50, P = 0.5 × 10(-6)]. Similar results were observed for 4150G > T polymorphism. In the combined meta-analyses, OR for -69GG or 4150GG genotype was 2.02 (95% CI = 1.59-2.45) or 1.86 (95% CI = 1.45-2.28) compared with -69AA or 4150TT genotype. In vivo FEN1 messenger RNA expression analyses showed that the -69G or 4150G allele carriers had ∼2-fold decreased FEN1 expression in gastrointestinal tissues compared with -69A or 4150T carriers, indicating that lower FEN1 expression may lead to higher risk for malignant transformation of gastrointestinal cells. Our results highlight FEN1 as an important gene in human gastrointestinal oncogenesis and genetic polymorphisms in FEN1 confer susceptibility to gastrointestinal cancers.

A functional lncRNA HOTAIR genetic variant contributes to gastric cancer susceptibility.

Long noncoding RNA (lncRNA) HOX transcript antisense RNA (HOTAIR) acts as an oncogene in gastric cancer development. HOTAIR could induce genome‐wide retargeting of polycomb‐repressive complex 2, trimethylates histone H3 lysine‐27 (H3K27me3) and deregulation of multiple downstream genes. Additionally, as the ceRNA of miR‐331–3p, HOTAIR may modulate HER2 deregulation in gastric cancer cells. We hypothesized that the functional single nucleotide polymorphisms (SNP) in HOTAIR may affect HOTAIR expression and/or its function and, thus, gastric cancer risk. We examined the association between three haplotype‐tagging SNPs (htSNP) across the whole HOTAIR locus and gastric cancer risk as well as the functional relevance of a gastric cancer susceptibility SNP rs920778. Genotypes were determined in two independent hospital‐based case‐control sets that consisted of 800 gastric cancer patients and 1600 controls. The allele‐specific regulation on HOTAIR expression by the rs920778 SNP was examined in vitro and in vivo. We found that the HOTAIR rs920778 TT carriers had a 1.66‐ and 1.87‐fold increased gastric cancer risk in Jinan and Huaian populations compared with the CC carriers (P = 4.2 × 10−4 and 6.5 × 10−5). During inspecting functional relevance of the rs920778 SNP, we observed an allelic regulation of rs920778 on HOTAIR expression in both gastric cancer cell lines and tissue samples, with higher HOTAIR expression among T allele carriers. These findings elucidate that functional genetic variants influencing lncRNA expression may explain a portion of gastric cancer genetic basis.

fMiRNA-192 and miRNA-204 Directly Suppress lncRNA HOTTIP and Interrupt GLS1-Mediated Glutaminolysis in Hepatocellular Carcinoma

Accumulated evidence demonstrated that long non-coding RNAs (lncRNAs) play a pivotal role in tumorigenesis. However, it is still largely unknown how these lncRNAs were regulated by small ncRNAs, such as microRNAs (miRNAs), at the post-transcriptional level. We here use lncRNA HOTTIP as an example to study how miRNAs impact lncRNAs expression and its biological significance in hepatocellular carcinoma (HCC). LncRNA HOTTIP is a vital oncogene in HCC, one of the deadliest cancers worldwide. In the current study, we identified miR-192 and miR-204 as two microRNAs (miRNAs) suppressing HOTTIP expression via the Argonaute 2 (AGO2)-mediated RNA interference (RNAi) pathway in HCC. Interaction between miR-192 or miR-204 and HOTTIP were further confirmed using dual luciferase reporter gene assays. Consistent with this notion, a significant negative correlation between these miRNAs and HOTTIP exists in HCC tissue specimens. Interestingly, the dysregulation of the three ncRNAs was associated with overall survival of HCC patients. In addition, the posttranscriptional silencing of HOTTIP by miR-192, miR-204 or HOTTIP siRNAs could significantly suppress viability of HCC cells. On the contrary, antagonizing endogenous miR-192 or miR-204 led to increased HOTTIP expression and stimulated cell proliferation. In vivo mouse xenograft model also support the tumor suppressor role of both miRNAs. Besides the known targets (multiple 5’ end HOX A genes, i.e. HOXA13), glutaminase (GLS1) was identified as a potential downstream target of the miR-192/-204-HOTTIP axis in HCC. Considering glutaminolysis as a crucial hallmark of cancer cells and significantly inhibited cell viability after silencingGLS1, we speculate that the miR-192/-204-HOTTIP axis may interrupt HCC glutaminolysis through GLS1 inhibition. These results elucidate that the miR-192/-204-HOTTIP axis might be an important molecular pathway during hepatic cell tumorigenesis. Our data in clinical HCC samples highlight miR-192, miR-204 and HOTTIP with prognostic and potentially therapeutic implications.

Association of a Genetic Variation in a miR-191 Binding Site in MDM4 with Risk of Esophageal Squamous Cell Carcinoma

As an oncoprotein, MDM4 plays a key part in P53 tumor suppressor pathway through negatively regulating P53 function. It has been reported that an rs4245739 A>C polymorphism locating in the MDM4 3′-untranslated region creates a miR-191 target site and results in decreased MDM4 expression. Therefore, we investigated the association between this polymorphism and esophageal squamous cell carcinoma (ESCC) risk as well as its biological function in vivo. Genotypes were determined in two independent case-control sets consisted of 1128 ESCC cases and 1150 controls from two regions of China. Odds ratios (ORs) and 95% confidence intervals (CIs) were estimated by logistic regression. The impact of the polymorphism on MDM4 expression was examined with esophagus tissues. Our results demonstrated that the MDM4 rs4245739 AC and CC genotypes were significantly associated with decreased ESCC risk compared with the AA genotype in both case-control sets (Jinan set: OR = 0.54, 95% CI = 0.35–0.82, P = 0.004; Huaian set: OR = 0.68, 95% CI = 0.45–0.99, P = 0.049). Stratified analyses revealed that a multiplicative interaction between rs4245739 and smoking or drinking was evident (Gene-smoking: P interactioin = 0.022; gene-drinking: P interactioin = 0.032). After detecting In vivo MDM4 mRNA expression, we found that the rs4245739 AC and CC genotype carriers had significantly decreased MDM4 expression in normal esophagus tissues compared with AA genotype carriers, indicating a consistent genotype-phenotype correlation. Our results elucidate that the MDM4 rs4245739 polymorphism contributes to susceptibility of ESCC and support the hypothesis that genetic variants, interrupting miRNA-mediated gene regulation, may modify cancer risk.

A functional BRCA1 coding sequence genetic variant contributes to risk of esophageal squamous cell carcinoma.

As a tumor suppressor, breast cancer susceptibility gene 1 (BRCA1) plays a pivotal role in maintaining genomic stability. A functional rs799917 T>C polymorphism located in the BRCA1 coding sequence could influence miR-638-mediated regulation of BRCA1 expression. Therefore, we examined the association between this polymorphism and esophageal squamous cell carcinoma (ESCC) risk as well as its biological function. Genotypes were determined in two independent case-control studies consisted of 1128 ESCC patients and 1150 controls. Odds ratios (ORs) and 95% confidence intervals (CIs) were estimated by logistic regression. The allele-specific regulation on BRCA1 expression by the polymorphism was investigated in vitro and in vivo. We found that the BRCA1 rs799917 CC genotype was significantly associated with increased ESCC risk compared with the TT genotype in both studies (Jinan population: OR = 1.28, 95% CI = 1.04-1.58, P = 0.020; Huaian population: OR = 1.46, 95% CI = 1.17-1.83, P = 0.001). Stratified analyses with pooled data indicated that a multiplicative interaction between rs799917 and smoking or drinking in intensifying ESCC risk was evident (gene-smoking: P interactio n = 5.8 × 10(-5); gene-drinking: P interaction = 7.1 × 10(-7)). In vitro experiments indicate that miR-638 could negatively regulate BRCA1 expression and enhance proliferation of ESCC cells. In vivo BRCA1 messenger RNA expression analyses showed that the rs799917 C allele carriers had significantly decreased BRCA1 expression in both normal and cancerous esophagus tissues compared with T allele carriers, suggesting that lower BRCA1 expression may lead to higher risk for malignant transformation of esophagus cells. These results suggest that BRCA1 functional rs799917 polymorphism is involved in susceptibility to developing ESCC, alone and in a gene-environment interaction manner.

Leukocyte telomere length-related genetic variants in 1p34.2 and 14q21 loci contribute to the risk of esophageal squamous cell carcinoma

Short leukocyte telomere length has been associated with significantly increased risk of esophageal cancer. A previous genome‐wide association study demonstrated that four SNPs (rs398652 on 14q21, rs621559 on 1p34.2, rs6028466 on 20q11.22 and rs654128 on 6q22.1) were associated with leukocyte telomere length in Caucasians. However, the role of these genetic variants on esophageal squamous cell carcinoma (ESCC) susceptibility is still unknown. Therefore, we investigated whether these polymorphisms have impact on leukocyte telomere length and the risk of ESCC in Chinese. After measuring leukocyte telomere length of 550 healthy individuals, we observed that both rs621559 and rs398652 genetic variants are significantly associated with leukocyte telomere length. On the basis of analyzing 1550 ESCC patients and frequency‐matched 1620 controls from 4 medical centers in China, we found that 0.71‐fold decreased risk of ESCC is associated with the rs621559 AA genotype compared with the rs621559 GG genotype (p = 5.9 × 10−6). We also detected a moderately increased OR for ESCC that was associated with the 14q21 rs398652 G allele (p = 6.5 × 10−4). It has been shown that both rs621559 and rs398652 polymorphisms were significantly associated with ESCC risk in additive, recessive or dominant genetic models. Stratified analyses demonstrated that these associations were more pronounced in males. Our results highlight the complexity of genetic regulation of telomere length and further support the important role of telomere in carcinogenesis.

Whole exome sequencing identifies lncRNA GAS8-AS1 and LPAR4 as novel papillary thyroid carcinoma driver alternations

Papillary thyroid carcinoma (PTC) is the most common type of thyroid cancer. However, we know little of mutational spectrum in the Chinese population. Thus, here we report the identification of somatic mutations for Chinese PTC using 402 tumor-normal pairs (Discovery: 91 pairs via exome sequencing; validation: 311 pairs via Sanger sequencing). We observed three distinct mutational signatures, evidently different from the two mutational signatures among Caucasian PTCs. Ten significantly mutated genes were identified, most previously uncharacterized. Notably, we found that long non-coding RNA (lncRNA) GAS8-AS1 is the secondary most frequently altered gene and acts as a novel tumor suppressor in PTC. As a mutation hotspot, the c.713A>G/714T>C dinucleotide substitution was found among 89.1% patients with GAS8-AS1 mutations and associated with advanced PTC disease (P = 0.009). Interestingly, the wild-type lncRNA GAS8-AS1 (A713T714) showed consistently higher capability to inhibit cancer cell growth compared to the mutated lncRNA (G713C714). Further studies also elucidated the oncogene nature of the G protein-coupled receptor LPAR4 and its c.872T>G (p.Ile291Ser) mutation in PTC malignant transformation. The BRAF c.1799T>A (p.Val600Glu) substitution was present in 59.0% Chinese PTCs, more frequently observed in patients with lymph node metastasis (P = 1.6 × 10(-4)). Together our study defines a exome mutational spectrum of PTC in the Chinese population and highlights lncRNA GAS8-AS1 and LPAR4 as potential diagnostics and therapeutic targets.

Association of functional FEN1 genetic variants and haplotypes and breast cancer risk.

AIM As a tumor suppressor, FEN1 plays an essential role in preventing tumorigenesis. Two functional germline variants (-69G>A and 4150G>T) in the FEN1 gene have been associated with DNA damage levels in coke-oven workers and multiple cancer risk in general populations. However, it is still unknown how these genetic variants are involved in breast cancer susceptibility. METHODS We investigated the association between these polymorphisms and breast cancer risk in two independent case-control sets consisted of a total of 1100 breast cancer cases and 1400 controls. The influence of these variations on FEN1 expression was also examined using breast normal tissues. RESULTS It was found that the FEN1-69GG genotypes were significantly correlated to increased risk for developing breast cancer compared with the -69AA genotype in both sets [Jinan set: odds ratios (OR)=1.41, 95% confidence interval (CI)=1.20-1.65, P=1.9×10(-5); Huaian set: OR=1.51, 95% CI=1.22-1.86, P=1.7×10(-4)]. Similar results were observed for 4150G>T polymorphism. The genotype-phenotype correlation analyses demonstrated that the -69G or 4150G allele carriers had more than 2-fold decreased FEN1 expression in breast tissues compared with -69A or 4150T carriers, suggesting that lower FEN1 expression may lead to higher risk for malignant transformation of breast cells. CONCLUSION Our findings highlight FEN1 as an important gene in human breast carcinogenesis and genetic variants in FEN1 confer susceptibility to breast cancer.