Multi-omic analysis suggests tumor suppressor genes evolved specific promoter features to optimize cancer resistance.

Tumor suppressor genes (TSGs) exhibit distinct evolutionary features. We speculated that TSG promoters could have evolved specific features that facilitate their tumor-suppressing functions. We found that the promoter CpG dinucleotide frequencies of TSGs are significantly higher than that of non-cancer genes across vertebrate genomes, and positively correlated with gene expression across tissue types. The promoter CpG dinucleotide frequencies of all genes gradually increase with gene age, for which young TSGs have been subject to a stronger evolutionary pressure. Transcription-related features, namely chromatin accessibility, methylation and ZNF263-, SP1-, E2F4- and SP2-binding elements, are associated with gene expression. Moreover, higher promoter CpG dinucleotide frequencies and chromatin accessibility are positively associated with the ability of TSGs to resist downregulation during tumorigenesis. These results were successfully validated with independent datasets. In conclusion, TSGs evolved specific promoter features that optimized cancer resistance through achieving high expression in normal tissues and resistance to downregulation during tumorigenesis.

New guidelines for DNA methylome studies regarding 5-hydroxymethylcytosine for understanding transcriptional regulation.

Many DNA methylome profiling methods cannot distinguish between 5-methylcytosine (5mC) and 5-hydroxymethylcytosine (5hmC). Because 5mC typically acts as a repressive mark whereas 5hmC is an intermediate form during active demethylation, the inability to separate their signals could lead to incorrect interpretation of the data. Is the extra information contained in 5hmC signals worth the additional experimental and computational costs? Here we combine whole-genome bisulfite sequencing (WGBS) and oxidative WGBS (oxWGBS) data in various human tissues to investigate the quantitative relationships between gene expression and the two forms of DNA methylation at promoters, transcript bodies, and immediate downstream regions. We find that 5mC and 5hmC signals correlate with gene expression in the same direction in most samples. Considering both types of signals increases the accuracy of expression levels inferred from methylation data by a median of 18.2% as compared to having only WGBS data, showing that the two forms of methylation provide complementary information about gene expression. Differential analysis between matched tumor and normal pairs is particularly affected by the superposition of 5mC and 5hmC signals in WGBS data, with at least 25%-40% of the differentially methylated regions (DMRs) identified from 5mC signals not detected from WGBS data. Our results also confirm a previous finding that methylation signals at transcript bodies are more indicative of gene expression levels than promoter methylation signals. Overall, our study provides data for evaluating the cost-effectiveness of some experimental and analysis options in the study of DNA methylation in normal and cancer samples.

Loss of tumor suppressor IGFBP4 drives epigenetic reprogramming in hepatic carcinogenesis.

Genomic sequencing of hepatocellular carcinoma (HCC) uncovers a paucity of actionable mutations, underscoring the necessity to exploit epigenetic vulnerabilities for therapeutics. In HCC, EZH2-mediated H3K27me3 represents a major oncogenic chromatin modification, but how it modulates the therapeutic vulnerability of signaling pathways remains unknown. Here, we show EZH2 acts antagonistically to AKT signaling in maintaining H3K27 methylome through epigenetic silencing of IGFBP4. ChIP-seq revealed enrichment of Ezh2/H3K27me3 at silenced loci in HBx-transgenic mouse-derived HCCs, including Igfbp4 whose down-regulation significantly correlated with EZH2 overexpression and poor survivals of HCC patients. Functional characterizations demonstrated potent growth- and invasion-suppressive functions of IGFBP4, which was associated with transcriptomic alterations leading to deregulation of multiple signaling pathways. Mechanistically, IGFBP4 stimulated AKT/EZH2 phosphorylation to abrogate H3K27me3-mediated silencing, forming a reciprocal feedback loop that suppressed core transcription factor networks (FOXA1/HNF1A/HNF4A/KLF9/NR1H4) for normal liver homeostasis. Consequently, the in vivo tumorigenicity of IGFBP4-silenced HCC cells was vulnerable to pharmacological inhibition of EZH2, but not AKT. Our study unveils chromatin regulation of a novel liver tumor suppressor IGFBP4, which constitutes an AKT-EZH2 reciprocal loop in driving H3K27me3-mediated epigenetic reprogramming. Defining the aberrant chromatin landscape of HCC sheds light into the mechanistic basis of effective EZH2-targeted inhibition.

E2F6 functions as a competing endogenous RNA, and transcriptional repressor, to promote ovarian cancer stemness.

Ovarian cancer is the most lethal cancer of the female reproductive system. In that regard, several epidemiological studies suggest that long-term exposure to estrogen could increase ovarian cancer risk, although its precise role remains controversial. To decipher a mechanism for this, we previously generated a mathematical model of how estrogen-mediated upregulation of the transcription factor, E2F6, upregulates the ovarian cancer stem/initiating cell marker, c-Kit, by epigenetic silencing the tumor suppressor miR-193a, and a competing endogenous (ceRNA) mechanism. In this study, we tested that previous mathematical model, showing that estrogen treatment of immortalized ovarian surface epithelial cells upregulated both E2F6 and c-KIT, but downregulated miR-193a. Luciferase assays further confirmed that microRNA-193a targets both E2F6 and c-Kit. Interestingly, ChIP-PCR and bisulphite pyrosequencing showed that E2F6 also epigenetically suppresses miR-193a, through recruitment of EZH2, and by a complex ceRNA mechanism in ovarian cancer cell lines. Importantly, cell line and animal experiments both confirmed that E2F6 promotes ovarian cancer stemness, whereas E2F6 or EZH2 depletion derepressed miR-193a, which opposes cancer stemness, by alleviating DNA methylation and repressive chromatin. Finally, 118 ovarian cancer patients with miR-193a promoter hypermethylation had poorer survival than those without hypermethylation. These results suggest that an estrogen-mediated E2F6 ceRNA network epigenetically and competitively inhibits microRNA-193a activity, promoting ovarian cancer stemness and tumorigenesis.

Mechanotransduction and Cytoskeleton Remodeling Shaping YAP1 in Gastric Tumorigenesis.

The essential role of Hippo signaling pathway in cancer development has been elucidated by recent studies. In the gastrointestinal tissues, deregulation of the Hippo pathway is one of the most important driving events for tumorigenesis. It is widely known that Yes-associated protein 1 (YAP1) and WW domain that contain transcription regulator 1 (TAZ), two transcriptional co-activators with a PDZ-binding motif, function as critical effectors negatively regulated by the Hippo pathway. Previous studies indicate the involvement of YAP1/TAZ in mechanotransduction by crosstalking with the extracellular matrix (ECM) and the F-actin cytoskeleton associated signaling network. In gastric cancer (GC), YAP1/TAZ functions as an oncogene and transcriptionally promotes tumor formation by cooperating with TEAD transcription factors. Apart from the classic role of Hippo-YAP1 cascade, in this review, we summarize the current investigations to highlight the prominent role of YAP1/TAZ as a mechanical sensor and responder under mechanical stress and address its potential prognostic and therapeutic value in GC.

The oncogenic role of Epstein-Barr virus-encoded microRNAs in Epstein-Barr virus-associated gastric carcinoma.

Epstein-Barr virus (EBV) infection is detected in various epithelial malignancies, such as nasopharyngeal carcinoma (NPC) and gastric cancer (GC). EBV comprises some unique molecular features and encodes viral genes and microRNAs (miRNAs) by its own DNA sequence. EBV genes are required to maintain latency and contribute to oncogenic property. miRNAs encoded by EBV have been shown to contribute to initiation and progression of EBV-related malignancies. By a number of genomic profiling studies, some EBV miRNAs were confirmed to be highly expressed in EBV-associated gastric cancer (EBVaGC) samples and cell lines. The majority host targets of the EBV miRNAs are important for promoting cell growth and inhibiting apoptosis, facilitating cell survival and immune evasion. However, the integrated molecular mechanisms related to EBV miRNAs remain to be investigated. In this review, we summarized the crucial role of EBV miRNAs in epithelial malignancies, especially in EBVaGC. Collectively, EBV miRNAs play a significant role in the viral and host gene regulation network. Understanding the comprehensive potential targets and relevant functions of EBV miRNAs in gastric carcinogenesis might provide better clinical translation.

Oncogenes without a Neighboring Tumor-Suppressor Gene Are More Prone to Amplification.

Focal copy number gains or losses are important genomic hallmarks of cancer. The genomic distribution of oncogenes and tumor-suppressor genes (TSG) in relation to focal copy number aberrations is unclear. Our analysis revealed that the mean distance of TSGs from oncogenes was significantly shorter than that of noncancer genes, suggesting that oncogenes and TSGs tend to be in close physical proximity in the human genome. Such relationship was conserved in mouse and drosophila. Pan-cancer analysis using data from The Cancer Genome Atlas indicated that oncogenes without a nearby TSG are more prone to amplification. In conclusion, our study provides evidence for the nonrandom distribution of oncogenes and TSGs across different species. Our data also support that the existence of a neighboring TSG can suppress amplification of an oncogene, shedding new light on a previously unappreciated protective mechanism of TSGs.

PIEZO1 functions as a potential oncogene by promoting cell proliferation and migration in gastric carcinogenesis.

Gastric cancer (GC) is one of the most common malignancies in Asian areas. PIEZO1 has been implied to regulate epithelial homeostasis to play an important role in physiological processes. It is also related to tumor initiation and progression. However, the role of PIEZO1 has not yet been explored in GC. The expression of PIEZO1 in GC cell lines and primary samples was determined by qRT-PCR and Western blot. The clinical correlation of PIEZO1 in GC was evaluated by immunohistochemistry on tissue microarray. The oncogenic role of PIEZO1 was demonstrated in gastric tumorigenesis through a series of functional assays, including cell proliferation, cell invasion, and flow cytometry analysis. Drug sensitivity was also assessed by PIEZO1 knockdown experiment. PIEZO1 exhibited an upregulation in most of the GC cell lines and primary samples compared with non-tumorous gastric epithelial tissues. Increase of PIEZO1 was associated with poor disease specific survival. PIEZO1 knockdown led to inhibitory effect by suppressing cell proliferation and invasion and inhibiting xenograft formation. Decreased PIEZO1 enhanced the sensitivity of Cisplatin or 5-FU treatment. Morphological alteration was also observed in siPIEZO1 treated cells. GTP-Rac1 showed accumulated activated form, while total-RhoA was decreased accompanied with PIEZO1 knockdown. In the present study, PIEZO1 is required for cell proliferation, migration and invasion to promote GC progression. PIEZO1 also maintains cellular morphology related to GC cell motility by regulating the activity of Rho GTPase family members. Our data not only suggested a novel prognostic marker, but also provided a useful clinical therapeutic target for GC.

The physiological role of Motin family and its dysregulation in tumorigenesis.

Members in Motin family, or Angiomotins (AMOTs), are adaptor proteins that localize in the membranous, cytoplasmic or nuclear fraction in a cell context-dependent manner. They control the bioprocesses such as migration, tight junction formation, cell polarity, and angiogenesis. Emerging evidences have demonstrated that AMOTs participate in cancer initiation and progression. Many of the previous studies have focused on the involvement of AMOTs in Hippo-YAP1 pathway. However, it has been controversial for years that AMOTs serve as either positive or negative growth regulators in different cancer types because of the various cellular origins. The molecular mechanisms of these opposite roles of AMOTs remain elusive. This review comprehensively summarized how AMOTs function physiologically and how their dysregulation promotes or inhibits tumorigenesis. Better understanding the functional roles of AMOTs in cancers may lead to an improvement of clinical interventions as well as development of novel therapeutic strategies for cancer patients.

IGF2BP3 functions as a potential oncogene and is a crucial target of miR-34a in gastric carcinogenesis.

BACKGROUND: Gastric cancer (GC) is one of the frequent causes of cancer-related death in eastern Asian population. IGF2BP2 lists in the top rank up-regulated genes in GC, but its functional role is unclear. METHOD: The expression of IGF2BP3 in GC cell lines and primary samples was examined by qRT-PCR and Western blot. The biological role of IGF2BP3 was revealed by a series of functional in vitro studies. Its regulation by microRNAs (miRNAs) was predicted by TargetScan and confirmed by luciferase assays and rescue experiments. RESULTS: IGF2BP3 ranked the No.1 of the up-regulated genes by expression microarray analysis in GC cell lines. The expression level of IGF2BP3 was observed in GC tissues comparing with non-tumorous gastric epitheliums. The up-regulated IGF2BP3 expression was associated with poor disease specific survival. IGF2BP3 knockdown significantly inhibited cell proliferation and invasion. Apart from copy number gain, IGF2BP3 has been confirmed to be negatively regulated by tumor-suppressive miRNA, namely miR-34a. The expression of miR-34a showed negative correlation with IGF2BP3 mRNA expression in primary GC samples and more importantly, re-overexpression of IGF2BP3 rescued the inhibitory effect of miR-34a. CONCLUSION: We compressively revealed the oncogenic role of IGF2BP3 in gastric tumorigenesis and confirmed its activation is partly due to the silence of miR-34a. Our findings identified useful prognostic biomarker and provided clinical translational potential.

Yin Yang 1-mediated epigenetic silencing of tumour-suppressive microRNAs activates nuclear factor-κB in hepatocellular carcinoma.

Enhancer of zeste homolog 2 (EZH2) catalyses histone H3 lysine 27 trimethylation (H3K27me3) to silence tumour-suppressor genes in hepatocellular carcinoma (HCC) but the process of locus-specific recruitment remains elusive. Here we investigated the transcription factors involved and the molecular consequences in HCC development. The genome-wide distribution of H3K27me3 was determined by chromatin immunoprecipitation coupled with high-throughput sequencing or promoter array analyses in HCC cells from hepatitis B virus (HBV) X protein transgenic mouse and human cell models. Transcription factor binding site analysis was performed to identify EZH2-interacting transcription factors followed by functional characterization. Our cross-species integrative analysis revealed a crucial link between Yin Yang 1 (YY1) and EZH2-mediated H3K27me3 in HCC. Gene expression analysis of human HBV-associated HCC specimens demonstrated concordant overexpression of YY1 and EZH2, which correlated with poor survival of patients in advanced stages. The YY1 binding motif was significantly enriched in both in vivo and in vitro H3K27me3-occupied genes, including genes for 15 tumour-suppressive microRNAs. Knockdown of YY1 reduced not only global H3K27me3 levels, but also EZH2 and H3K27me3 promoter occupancy and DNA methylation, leading to the transcriptional up-regulation of microRNA-9 isoforms in HCC cells. Concurrent EZH2 knockdown and 5-aza-2'-deoxycytidine treatment synergistically increased the levels of microRNA-9, which reduced the expression and transcriptional activity of nuclear factor-κB (NF-κB). Functionally, YY1 promoted HCC tumourigenicity and inhibited apoptosis of HCC cells, at least partially through NF-κB activation. In conclusion, YY1 overexpression contributes to EZH2 recruitment for H3K27me3-mediated silencing of tumour-suppressive microRNAs, thereby activating NF-κB signalling in hepatocarcinogenesis.

The Interplay of LncRNA-H19 and Its Binding Partners in Physiological Process and Gastric Carcinogenesis.

Long non-coding RNA (lncRNA), a novel and effective modulator in carcinogenesis, has become a study hotspot in recent years. The imprinted oncofetal lncRNA H19 is one of the first identified imprinted lncRNAs with a high expression level in embryogenesis but is barely detectable in most tissues after birth. Aberrant alterations of H19 expression have been demonstrated in various tumors, including gastric cancer (GC), implicating a crucial role of H19 in cancer progression. As one of the top malignancies in the world, GC has already become a serious concern to public health with poor prognosis. The regulatory roles of H19 in gastric carcinogenesis have been explored by various research groups, which leads to the development of GC therapy. This review comprehensively summarizes the current knowledge of H19 in tumorigenesis, especially in GC pathogenesis, with emphasis on the underneath molecular mechanisms depicted from its functional partners. Furthermore, the accumulated knowledge of H19 will provide better understanding on targeted therapy of GC.

NOTCH receptors in gastric and other gastrointestinal cancers: oncogenes or tumor suppressors?

Gastric cancer (GC) ranks the most common cancer types and is one of the leading causes of cancer-related death. Due to delayed diagnosis and high metastatic frequency, 5-year survival rate of GC is rather low. It is a complex disease resulting from the interaction between environmental factors and host genetic alterations that deregulate multiple signaling pathways. The Notch signaling pathway, a highly conserved system in the regulation of the fate in several cell types, plays a pivotal role in cell differentiation, survival and proliferation. Notch is also one of the most commonly activated signaling pathways in tumors and its aberrant activation plays a key role in cancer advancement. Whether Notch cascade exerts oncogenic or tumor suppressive function in different cancer types depends on the cellular context. Mammals have four NOTCH receptors that modulate Notch pathway activity. In this review, we provide a comprehensive summary on the functional role of NOTCH receptors in gastric and other gastrointestinal cancers. Increasing knowledge of NOTCH receptors in gastrointestinal cancers will help us recognize the underlying mechanisms of Notch signaling and develop novel therapeutic strategies for GC.

miR-508-3p concordantly silences NFKB1 and RELA to inactivate canonical NF-κB signaling in gastric carcinogenesis.

BACKGROUND: NF-κB signaling pathway plays an important role in gastric carcinogenesis. The basic expression and functional role of NFKB1 and RELA (components of canonical NF-κB pathway) in gastric cancer (GC) have not been well elucidated. In this study, the role of NFKB1 and RELA in gastric tumorigenesis will be investigated and their regulation by microRNAs (miRNAs) will be deeply explored. METHODS: The mRNA and protein expression of NFKB1 and RELA were investigated by qRT-PCR and Western blot in GC cell lines and primary tumors. The functional roles of NFKB1 and RELA in GC were demonstrated by MTT proliferation assay, monolayer colony formation, cell invasion and migration, cell cycle analysis and in vivo study through siRNA mediated knockdown. Identification of NFKB1 as a direct target of tumor suppressor miRNA miR-508-3p was achieved by expression regulation assays together with dual luciferase activity experiments. RESULTS: NFKB1 and RELA were up-regulated in GC cell lines and primary tumors compared with normal gastric epithelium cells and their upregulation correlation with poor survival in GC. siRNA mediated knockdown of NFKB1 or RELA exhibited anti-oncogenic effect both in vitro and in vivo. NFKB1 was further revealed to be a direct target of miR-508-3p in gastric tumorigenesis and their expression showed negative correlation in primary GC samples. miR-508-3p was down-regulated in GC cells compared with normal gastric epithelium samples and its ectopic expression in GC cell lines also exerts tumor suppressor function. NFKB1 re-expression was found to partly abolish the tumor-suppressive effect of miR-508-3p in GC. CONCLUSION: All these findings supports that canonical NF-κB signaling pathway is activated in GC at least by the inactivation of miR-508-3p and this might have therapeutic potential in GC treatment.

CUL4B: a novel epigenetic driver in Wnt/ß-catenin-dependent hepatocarcinogenesis.

Emerging evidence indicates that Cullin 4B (CUL4B), a major component of ubiquitin ligase complexes, is over-expressed in diverse cancer types with pro-tumourigenic effects. In this issue of the Journal of Pathology, Yuan and colleagues [6] elucidated the oncogenic activity of CUL4B in hepatocellular carcinoma (HCC) and delineated its role in driving Wnt/ß-catenin signalling. In addition to the stabilization of ß-catenin protein against proteasomal degradation, CUL4B also acts in concert with enhancer of Zeste homologue 2 (EZH2) to concordantly silence multiple Wnt inhibitors. These findings provide significant mechanistic insights into the epigenetic activation of the Wnt/ß-catenin pathway in HCC and shed light on the functional importance of ubiquitination in this intricate regulatory system.

Truncated HBx-dependent silencing of GAS2 promotes hepatocarcinogenesis through deregulation of cell cycle, senescence and p53-mediated apoptosis.

Hepatocellular carcinoma (HCC) is a worldwide threat to public health, especially in China, where chronic hepatitis B virus (HBV) infection is found in 80-90% of all HCCs. The HBV-encoded X antigen (HBx) is a trans-regulatory protein involved in virus-induced hepatocarcinogenesis. Although the carboxyl-terminus-truncated HBx, rather than the full-length counterpart, is frequently overexpressed in human HCCs, its functional mechanisms are not fully defined. We investigated the molecular function of a naturally occurring HBx variant which has 35 amino acids deleted at the C-terminus (HBxΔ35). Genome-wide scanning analysis and PCR validation identified growth arrest-specific 2 (GAS2) as a direct target of HBxΔ35 at transcriptional level in human immortalized liver cells. HBxΔ35 was found to bind the promoter region of GAS2 and attenuate its expression to promote hepatocellular proliferation and tumourigenicity. Further functional assays demonstrated that GAS2 induces p53-dependent apoptosis and senescence to counteract HBxΔ35-mediated tumourigenesis. Notably, GAS2 expression was significantly down-regulated in HCCs compared with the corresponding normal tissues. In conclusion, our integrated study uncovered a novel viral mechanism in hepatocarcinogenesis, wherein HBxΔ35 deregulates cell growth via direct silencing of GAS2 and thereby provides a survival advantage for pre-neoplastic hepatocytes to facilitate cancer development.

The TEAD Family and Its Oncogenic Role in Promoting Tumorigenesis.

The TEAD family of transcription factors is necessary for developmental processes. The family members contain a TEA domain for the binding with DNA elements and a transactivation domain for the interaction with transcription coactivators. TEAD proteins are required for the participation of coactivators to transmit the signal of pathways for the downstream signaling processes. TEADs also play an important role in tumor initiation and facilitate cancer progression via activating a series of progression-inducing genes, such as CTGF, Cyr61, Myc and Gli2. Recent studies have highlighted that TEADs, together with their coactivators, promote or even act as the crucial parts in the development of various malignancies, such as liver, ovarian, breast and prostate cancers. Furthermore, TEADs are proposed to be useful prognostic biomarkers due to the ideal correlation between high expression and clinicopathological parameters in gastric, breast, ovarian and prostate cancers. In this review, we summarize the functional role of TEAD proteins in tumorigenesis and discuss the key role of TEAD transcription factors in the linking of signal cascade transductions. Improved knowledge of the TEAD proteins will be helpful for deep understanding of the molecular mechanisms of tumorigenesis and identifying ideal predictive or prognostic biomarkers, even providing clinical translation for anticancer therapy in human cancers.

Autophagy Mediates HBx-Induced Nuclear Factor-κB Activation and Release of IL-6, IL-8, and CXCL2 in Hepatocytes.

Hepatitis B virus (HBV) and one of its encoded proteins, HBV X protein (HBx), have been shown to induce autophagy in hepatoma cells. Substantial evidence indicates that autophagy is a potent suppressor of inflammation. However, sporadic reports suggest that autophagy could promote pro-inflammatory cytokine expression and inflammation in some biological contexts. Here, we show that overexpression of HBx induces LC3B-positive autophagosome formation, increases autophagic flux and enhances the expression of ATG5, ATG7, and LC3B-II in normal hepatocytes. Abrogation of autophagy by small interfering RNA against ATG5 and ATG7 prevents HBx-induced formation of autophagosomes. Autophagy inhibition also abrogates HBx-induced activation of nuclear factor-κB (NF-κB) and production of interleukin-6 (IL-6), IL-8, and CXCL2. These findings suggest that autophagy is required for HBx-induced NF-κB activation and pro-inflammatory cytokine production and could shed new light on the complex role of autophagy in the modulation of inflammation.

Targeting of YAP1 by microRNA-15a and microRNA-16-1 exerts tumor suppressor function in gastric adenocarcinoma.

BACKGROUND: MicroRNAs (miRNAs) have been reported to play an important role in tumorigenesis. In this study, the role of miR-15a and miR-16-1 in gastric adenocarcinoma (GAC) was investigated. METHODS: The expression of miR-15a and miR-16-1 in cell lines and primary tumors was examined by miRNA qRT-PCR. Proliferative assays, colony formation, cell invasion and migration, flow cytometry analysis and in vivo study were performed by ectopic expression of miR-15a and miR-16-1. The putative target genes of miR-15a and miR-16-1 were explored by TargetScan and further validated. RESULTS: We found that miR-15a and miR-16-1 were down-regulated in GAC cell lines and primary tumor samples compared with normal gastric epithelium. Functional study demonstrated that ectopic expression of miR-15a and miR-16-1 suppressed cell proliferation, monolayer colony formation, invasion and migration, and xenograft formation in vivo. In addition, miR-15a and miR-16-1 induced G0/G1 cell cycle arrest which was further confirmed by Western blot and qRT-PCR of related cell cycle regulators. YAP1 was confirmed to be a functional target of miR-15a and miR-16-1 in GAC. YAP1 re-expression partly abrogated the inhibitory effect of miR-15a and miR-16-1 in GAC cells. In clinical samples, YAP1 protein expression shows negative correlation with miR-15a and miR-16-1 expression. CONCLUSION: In conclusion, targeting YAP1 by tumor suppressor miRNA miR-15a and miR-16-1 plays inhibitory effect and this might have a therapeutic potential in GAC.