Altered expression of MiR-148a and MiR-152 in gastrointestinal cancers and its clinical significance

MicroRNA-148b suppresses cell growth by targeting cholecystokinin-2 receptor in colorectal cancer

MicroRNAs (miRNAs) play an important role in the regulation of a variety of cellular processes, including cell growth, differentiation, apoptosis and carcinogenesis. The purpose of this study was to elucidate the molecular mechanisms by which miR-148b acts as a tumor suppressor in colorectal cancer. The expression of miR-148b was significantly downregulated in 96 pairs of human colorectal cancer tissues (p<0.0001) and three cell lines (p<0.01) compared with non-tumor adjacent tissues by quantitative real-time PCR. The results of in situ hybridization highlighted that miR-148b was important in the cancer transformation process. Using statistical analysis, we found that the expression level of miR-148b was associated with tumor size (p=0.033) in colorectal cancer patients. Moreover, overexpression of miR-148b in HCT-116 and HT-29 cells could inhibit cell proliferation in vitro and suppress tumorigenicity in vivo. Importantly, the result of luciferase activity assay and western blot showed that the cholecystokinin-2 receptor gene (CCK2R) was a target of miR-148b and was downregulated by miR-148b at the translational level. Then, we used siRNA, radioimmunoassay and ELISA to demonstrate that miR-148b might have an effect on cell proliferation by regulating the expression of CCK2R which functioned depending on the gastrin in colorectal cancer. Taken together, our data provides the first evidences that miR-148b acts as a tumor suppressor in colorectal cancer and should be further evaluated as a biomarker and therapeutic tool against colorectal cancer.

MicroRNA-148a suppresses tumor cell invasion and metastasis by downregulating ROCK1 in gastric cancer

PURPOSE

MicroRNAs (miRNA) have been documented playing a critical role in cancer development and progression. In this study, we investigate the role of miR-148a in gastric cancer metastasis.

EXPERIMENTAL DESIGN

We examined miR-148a levels in 90 gastric cancer samples by qRT-PCR and analyzed the clinicopathologic significance of miR-148a expression. The gastric cancer cells stably expressing miRNA-148a were analyzed for migration and invasion assays in vitro and metastasis assays in vivo; the target genes of miR-148a were further explored.

RESULTS

We found that miR-148a expression was suppressed by more than 4-fold in gastric cancer compared with their corresponding nontumorous tissues, and the downregulated miR-148a was significantly associated with tumor-node-metastasis (TNM) stage and lymph node-metastasis. Functional assays showed that overexpression of miR-148a suppressed gastric cancer cell migration and invasion in vitro and lung metastasis formation in vivo. In addition, overexpression of miR-148a in GC cells could reduce the mRNA and protein levels of ROCK1, whereas miR-148a silencing significantly increased ROCK1 expression. Luciferase assays confirmed that miR-148a could directly bind to the 2 sites of 3' untranslated region of ROCK1. Moreover, in gastric cancer tissues, we observed an inverse correlation between miR-148a and ROCK1 expression. Knockdown of ROCK1 significantly inhibited gastric cancer cell migration and invasion resembling that of miR-148a overexpression. We further found that ROCK1 was involved in miR-148a-induced suppression of gastric cancer cell migration and invasion.

CONCLUSIONS

miR-148a functions as a tumor metastasis suppressor in gastric cancer, and downregulation of miR-148a contributes to gastric cancer lymph node-metastasis and progression. miR-148a may have a therapeutic potential to suppress gastric cancer metastasis.

MicroRNA-148a is down-regulated in human pancreatic ductal adenocarcinomas and regulates cell survival by targeting CDC25B

MicroRNAs (miRNAs: short non-coding RNAs) are emerging as a class of potential novel tumor markers, as their dysregulation is being increasingly reported in various types of cancers. In the present study, we investigated the transcription status of miRNA-148a (miR-148a) in human pancreatic ductal adenocarcinoma (PDAC) and its role in the regulation of the dual specificity protein phosphatase CDC25B. We observed that miR-148a exhibited a significant 4-fold down-regulation in PDAC as opposed to normal pancreatic ductal cells. In addition, we observed that stable lentiviral-mediated overexpression of miR-148a in the pancreatic cancer cell line IMIM-PC2, inhibited tumor cell growth and colony formation. Furthermore, CDC25B was identified as a potential target of miR-148a by in silico analysis using PicTar, Targetscan and miRanda in conjunction with gene ontology analysis. The proposed interaction between miR-148a and the 3' untranslated region (UTR) of CDC25B was verified by in-vitro luciferase assays. We demonstrate that the activity of a luciferase reporter containing the 3'UTR of CDC25B was repressed in the presence of miR-148a mimics, confirming that miR-148a targets the 3'UTR of CDC25B. Finally, CDC25B was down-regulated at the protein level in miR-148a overexpressing IMIM-PC2-cells, and in transiently transfected pancreatic cell lines (as detected by Western blot analysis), as well as in patient tumor samples (as detected by immunohistochemistry). In summary, we identified CDC25B as a novel miR-148a target which may confer a proliferative advantage in PDAC.

miR-152 is a tumor suppressor microRNA that is silenced by DNA hypermethylation in endometrial cancer

The etiology and development of human cancers that remain little understood might be enlightened by defining tumor suppressor microRNAs (TS-miRNA). In this study, we identified TS-miRNAs silenced by aberrant DNA hypermethylation in endometrial cancer. Functional screening of 327 synthetic miRNAs in an endometrial cancer cell proliferation assay identified 103 miRNAs that inhibited cell growth. We then determined the sequence, DNA methylation status, and expression levels of these miRNAs in endometrial cancer cell lines and primary tumors. These determinations led to the identification of miR-152 as a candidate TS-miRNA gene in endometrial cancer. Epigenetic silencing documented in miR-152 was consistent with its location at 17q21.32 in intron 1 of the COPZ2 gene, which is also silenced often in endometrial cancer by DNA hypermethylation, and also with evidence that miR-152 targets the DNA methyltransferase DNMT1. Notably, restoration of miR-152 expression in endometrial cancer cell lines was sufficient to inhibit tumor cell growth in vitro and in vivo. We identified E2F3, MET, and Rictor as novel candidate targets of miR-152, suggesting how its epigenetic silencing can drive endometrial carcinogenesis. Our findings define a central role for miR-152 in endometrial cancer, and they also suggest its use in new therapeutic strategies to treat this cancer.

Inverse association between miR-194 expression and tumor invasion in gastric cancer

BACKGROUND

MiR-194 has been shown to be specifically expressed in the human gastrointestinal tract and may play an antimetastatic role in primary liver cancer cells. However, the role of miR-194 in gastric cancer is still unclear.

METHODS

Total RNA was extracted from tissues of 119 patients with gastric cancer and three gastric cancer cell lines (SGC-7901, MGC-803, and BGC-823). Expression levels of miR-194 were determined by real-time polymerase chain reaction (PCR). Moreover, a MTT proliferation assay and transwell cell invasion assay were performed to study the effect of miR-194 on SGC-7901 cell proliferation and invasion. Finally, we used real-time PCR and western blot to verify which gene was the target of miR-194 in gastric cancer.

RESULTS

Though there was no significant difference between cancerous and matching noncancerous tissues, we found patients with lower expression of miR-194 tended to have larger tumor size (P = 0.002) and more advanced pT stage (P = 0.028) in gastric cancer. Moreover, the expression of miR-194 was significantly lower in Borrmann IV type gastric cancer than in Borrmann I, II, and III types (P = 0.019). Furthermore, an in vitro invasion assay indicated that the penetrated cell intensity after miR-194 mimics transfection was significantly lower than the control. However, overexpression of miR-194 had little effect on the SGC-7901 cell cycle and proliferation. The results of real-time PCR and western blot highlighted that miR-194 interacted with N-cadherin and negatively regulated its expression at the translational level.

CONCLUSION

These findings imply that miR-194 might play an important role in gastric cancer invasion and progression.

MicroRNA-335 acts as a metastasis suppressor in gastric cancer by targeting Bcl-w and specificity protein 1

Aberrant expression of miR-335 has been frequently reported in cancer studies, suggesting that there is a close correlation between miR-335 and cancer during its development, progression, metastasis and prognosis. The expression of miR-335 in gastric cancer and its effects are not known. Relative expression of miR-335 in 4 gastric cancer cell lines and in 70 gastric cancer tissues was confirmed by real-time quantitative reverse transcriptase-PCR compared with controls. Transwell cell migration and Matrigel invasion assay in vitro and metastasis formation assay in vivo were used to examine the effects of miR-335 expression on gastric cancer cell invasion and metastasis. The effect of miR-335 expression on gastric cancer cell proliferation was estimated by the 3-(4,5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide assay. Luciferase reporter assay and western blot were used to examine the potential target genes and related pathways. Gene silencing with small-interfering RNA was used to examine the effects of target genes on gastric cancer cell invasion. miR-335 was dramatically downregulated in gastric cancer cell lines than in the normal gastric cell line GES-1. Low expression of miR-335 was significantly associated with lymph-node metastasis, poor pT stage, poor pN stage and invasion of lymphatic vessels. Overexpression of miR-335 suppressed gastric cancer cell invasion and metastasis in vitro and in vivo, but has no significant effects on cell proliferation. Furthermore, miR-335 might suppress gastric cancer invasion and metastasis by targeting Bcl-w and specificity protein 1 (SP1). Taken together, our results provide evidence that miR-335 might function as a metastasis suppressor in gastric cancer by targeting SP1 directly and indirectly through the Bcl-w-induced phosphoinositide 3-kinase-Akt-Sp1 pathway. miR-335 showing altered expression at different stages of gastric cancer could be a target for gastric cancer therapies and could be further developed as a potential prognostic factor.

miR-22 represses cancer progression by inducing cellular senescence

The microRNA miR-22 targets CDK6, SIRT1, and Sp1—genes involved in regulation of the senescence program—to suppress cell growth and proliferation.

Cellular senescence acts as a barrier to cancer progression, and microRNAs (miRNAs) are thought to be potential senescence regulators. However, whether senescence-associated miRNAs (SA-miRNAs) contribute to tumor suppression remains unknown. Here, we report that miR-22, a novel SA-miRNA, has an impact on tumorigenesis. miR-22 is up-regulated in human senescent fibroblasts and epithelial cells but down-regulated in various cancer cell lines. miR-22 overexpression induces growth suppression and acquisition of a senescent phenotype in human normal and cancer cells. miR-22 knockdown in presenescent fibroblasts decreased cell size, and cells became more compact. miR-22–induced senescence also decreases cell motility and inhibits cell invasion in vitro. Synthetic miR-22 delivery suppresses tumor growth and metastasis in vivo by inducing cellular senescence in a mouse model of breast carcinoma. We confirmed that CDK6, SIRT1, and Sp1, genes involved in the senescence program, are direct targets of miR-22. Our study provides the first evidence that miR-22 restores the cellular senescence program in cancer cells and acts as a tumor suppressor.

Integrative network analysis reveals active microRNAs and their functions in gastric cancer

BACKGROUND

MicroRNAs (miRNAs) are a class of endogenous, small and highly conserved noncoding RNAs that control gene expression either by degradation of target mRNAs or by inhibition of protein translation. They play important roles in cancer progression. A single miRNA can provoke a chain reaction and further affect protein interaction network (PIN). Therefore, we developed a novel integrative approach to identify the functional roles and the regulated PIN of oncomirs.

RESULTS

We integrated the expression profiles of miRNA and mRNA with the human PIN to reveal miRNA-regulated PIN in specific biological conditions. The potential functions of miRNAs were determined by functional enrichment analysis and the activities of miRNA-regulated PINs were evaluated by the co-expression of protein-protein interactions (PPIs). The function of a specific miRNA, miR-148a, was further examined by clinical data analysis and cell-based experiments. We uncovered several miRNA-regulated networks which were enriched with functions related to cancer progression. One miRNA, miR-148a, was identified and its function is to decrease tumor proliferation and metastasis through its regulated PIN. Furthermore, we found that miR-148a could reduce the invasiveness, migratory and adhesive activities of gastric tumor cells. Most importantly, elevated miR-148a level in gastric cancer tissues was strongly correlated with distant metastasis, organ and peritoneal invasion and reduced survival rate.

CONCLUSIONS

This study provides a novel method to identify active oncomirs and their potential functions in gastric cancer progression. The present data suggest that miR-148a could be a potential prognostic biomarker of gastric cancer and function as a tumor suppressor through repressing the activity of its regulated PIN.

Epigenetically silenced miR-34b/c as a novel faecal-based screening marker for colorectal cancer

BACKGROUND

MicroRNAs are tiny non-coding small endogenous RNAs that regulate gene expression by translational repression, mRNA cleavage and mRNA inhibition. The aim of this study was to investigate the hypermethylation of miR-34b/c and miR-148a in colorectal cancer, and correlate this data to clinicopathological features. We also aimed to evaluate the hypermethylation of miR-34b/c in faeces specimens as a novel non-invasive faecal-DNA-based screening marker.

METHODS

The 5-aza-2'-deoxycytidine treatment and methylation-specific PCR were carried out to detect the hypermethylation of miR-34b/c and miR-148a.

RESULTS

The miR-34b/c hypermethylation was found in 97.5% (79 out of 82) of primary colorectal tumours, P=0.0110. In 75% (21 out of 28) of faecal specimens we found a hypermethylation of miR-34b/c while only in 16% (2 out of 12) of high-grade dysplasia. In addition, miR-148a was found to be hypermethylated in 65% (51 out of 78) of colorectal tumour tissues with no significant correlation to clinicopathological features. However, a trend with female gender and advanced age was found, P=0.083. We also observed a trend to lower survival rate in patients with miR-148a hypermethylation with 10-year survival probability: 48 vs 65%, P=0.561.

CONCLUSIONS

These findings show that aberrant hypermethylation of miR-34b/c could be an ideal class of early screening marker, whereas miR-148a could serve as a disease progression follow-up marker.

miR-148a promoted cell proliferation by targeting p27 in gastric cancer cells

Accumulating evidence has shown that miRNAs are aberrantly expressed in human gastric cancer and crucial to tumorigenesis. Herein, we identified the role of miR-148a in gastric cell proliferation. miR-148a knockdown inhibited cell proliferation in gastric cancer cell lines. Conversely, miR-148a overexpression promoted cell proliferation and cell cycle progression. p27, a key inhibitor of cell cycle, was verified as the target of miR-148a, indicating miR-148a might downregulate p27 expression to promote gastric cell proliferation. Moreover, we confirmed that miR-148a expression was frequently and dramatically downregulated in human advanced gastric cancer tissues, and observed a good inverse correlation between miR-148a and p27 expression in tumor samples. Thus, our results demonstrated that miR-148a downregulation might exert some sort of antagonistic function in cell proliferation, rather than promote cell proliferation in gastric cancer.

Colon cancer-related microRNAs: implications for translational research

Colon carcinogenesis is a stepwise progression from polyps to adenocarcinomas and distant metastasis. These pathologic changes are contributed by aberrant activation or inactivation of protein-coding proto-oncogenes and tumor suppressor genes. However, recent discoveries in microRNA research have reshaped our understanding of the role of non-protein-coding genes in carcinogenesis. In this regard, a remarkable number of microRNAs exhibit differential expression in colon cancer tissues. These microRNAs alter cell proliferation, apoptosis and metastasis through their interactions with intracellular signaling networks. From a clinical perspective, polymorphisms within microRNA-binding sites are associated with the risk for colon cancer while microRNAs isolated from feces or blood may serve as biomarkers for early diagnosis. Altered expression of microRNAs or polymorphisms in microRNA-related genes have also been shown to correlate with patient survival or treatment outcome. Further insights into microRNA dysregulation in colon cancer and the advancement of RNA delivery technology will make it very likely to develop novel microRNA-based therapeutics.

MiR-148a promotes apoptosis by targeting Bcl-2 in colorectal cancer

Apoptosis has a vital role in maintaining tissue homeostasis, and dysregulation of the apoptotic pathway is now widely recognized as a key step in tumourigenesis. Increasingly, evidence has demonstrated that microRNA (miRNA) can exert various biological functions in tumours by targeting oncogenes or tumour suppressors. Nevertheless, the role of miRNA in apoptosis remains unclear. Here we show that ectopical expression of miR-148a can induce apoptosis in colorectal cancer cells. In addition, MYB can inhibit miR-148a by directly acting on the transcription factor binding site in miR-148a gene and miR-148a can posttranscriptionally silence Bcl-2. Subsequently, the intrinsic apoptosis pathway is activated by releasing cytochrome c, cleaving caspase 9, caspase 3 and PARP, which eventually induce cancer-cell apoptosis. These findings are part of a hitherto undocumented apoptotic regulatory pathway in which a pleiotropic transcription factor controls the expression of a miRNA and the miRNA inhibits the target, leading to activation of an intrinsic mitochondrial pathway and tumour apoptosis.

miR-449 inhibits cell proliferation and is down-regulated in gastric cancer

BACKGROUND

Gastric cancer is the fourth most common cancer in the world and the second most prevalent cause of cancer related death. The development of gastric cancer is mainly associated with H. Pylori infection leading to a focus in pathology studies on bacterial and environmental factors, and to a lesser extent on the mechanistic development of the tumour. MicroRNAs are small non-coding RNA molecules involved in post-transcriptional gene regulation. They are found to regulate genes involved in diverse biological functions and alterations in microRNA expression have been linked to the pathogenesis of many malignancies. The current study is focused on identifying microRNAs involved in gastric carcinogenesis and to explore their mechanistic relevance by characterizing their targets.

RESULTS

Invitrogen NCode miRNA microarrays identified miR-449 to be decreased in 1-year-old Gastrin KO mice and in H. Pylori infected gastric tissues compared to tissues from wild type animals. Growth rate of gastric cell lines over-expressing miR-449 was inhibited by 60% compared to controls. FACS cell cycle analysis of miR-449 over-expressing cells showed a significant increase in the sub-G1 fraction indicative of apoptosis. ß-Gal assays indicated a senescent phenotype of gastric cell lines over-expressing miR-449. Affymetrix 133v2 arrays identified GMNN, MET, CCNE2, SIRT1 and CDK6 as miR-449 targets. Luciferase assays were used to confirm GMNN, MET, CCNE2 and SIRT1 as direct targets. We also show that miR-449 over-expression activated p53 and its downstream target p21 as well as the apoptosis markers cleaved CASP3 and PARP. Importantly, qPCR analyses showed a loss of miR-449 expression in human clinical gastric tumours compared to normal tissues.

CONCLUSIONS

In this study, we document a diminished expression of miR-449 in Gastrin KO mice and further confirmed its loss in human gastric tumours. We investigated the function of miR-449 by identifying its direct targets. Furthermore we show that miR-449 induces senescence and apoptosis by activating the p53 pathway.

Glycomic and glycoproteomic analysis of serum from patients with stomach cancer reveals potential markers arising from host defense response mechanisms

Despite the reduced incidence of gastric cancer in the developed world, a diagnosis of stomach carcinoma still carries a poor prognosis due to the asymptomatic nature of the disease in the early stages, subsequent advanced stage diagnosis, and a low 5 year survival rate. Endoscopy remains the primary standard for diagnosis of stomach carcinoma and the current marker, carbohydrate antigen 19-9 (CA19-9) lacks the levels of sensitivity and specificity required in order to make it clinically useful for diagnostic monitoring. Therefore, there is a current need for additional markers to improve the diagnostic accuracy for the early stages of stomach cancer. Together, glycomic, proteomic, and glycoproteomic analyses of serum have the potential to identify such probable markers. A discovery study is reported here using preoperative serum from 80 stomach cancer patients, 10 patients bearing benign stomach disease, and 20 matched controls. Glycomic analysis of the total and immunoaffinity depleted serum revealed statistically significant increases in the levels of sialyl Lewis X epitopes (SLe(X)) present on triantennary glycans accompanied by increased levels of core fucosylated agalactosyl biantennary glycans present on IgG (referred to as the IgG G0 glycoform) which are associated with increasing disease pathogenesis. Protein expression analysis using 2D-DiGE returned a number of differentially expressed protein candidates in the depleted serum, many of which were shown to carry triantennary SLe(X) during subsequent glycomic investigations. Biological pathway analysis of the experimental data returned complement activation and acute phase response signaling as the most significantly altered pathways in the stomach cancer patient serum. Upon the basis of these findings, it is suggested that increased expression of IgG G0 and complement activation are a host response to the presence of the stomach tumor while the increased expression of SLe(X) and acute phase response proteins is a result of pro-inflammatory cytokine signaling, including IL-6, during carcinogenesis. The approach presented herein provides an insight into the underlying mechanisms of disease and the resulting changes in the glycome and glycoproteome offer promise as potential markers for diagnosis and prognostic monitoring in stomach cancer.

MicroRNA-148b is frequently down-regulated in gastric cancer and acts as a tumor suppressor by inhibiting cell proliferation

BACKGROUND

MicroRNAs (miRNAs) are involved in cancer development and progression, acting as tumor suppressors or oncogenes. Our previous studies have revealed that miR-148a and miR-152 are significantly down-regulated in gastrointestinal cancers. Interestingly, miR-148b has the same "seed sequences" as miR-148a and miR-152. Although aberrant expression of miR-148b has been observed in several types of cancer, its pathophysiologic role and relevance to tumorigenesis are still largely unknown. The purpose of this study was to elucidate the molecular mechanisms by which miR-148b acts as a tumor suppressor in gastric cancer.

RESULTS

We showed significant down-regulation of miR-148b in 106 gastric cancer tissues and four gastric cancer cell lines, compared with their non-tumor counterparts by real-time RT-PCR. In situ hybridization of ten cases confirmed an overt decrease in the level of miR-148b in gastric cancer tissues. Moreover, the expression of miR-148b was demonstrated to be associated with tumor size (P = 0.027) by a Mann-Whitney U test. We also found that miR-148b could inhibit cell proliferation in vitro by MTT assay, growth curves and an anchorage-independent growth assay in MGC-803, SGC-7901, BGC-823 and AGS cells. An experiment in nude mice revealed that miR-148b could suppress tumorigenicity in vivo. Using a luciferase activity assay and western blot, CCKBR was identified as a target of miR-148b in cells. Moreover, an obvious inverse correlation was observed between the expression of CCKBR protein and miR-148b in 49 pairs of tissues (P = 0.002, Spearman's correlation).

CONCLUSIONS

These findings provide important evidence that miR-148b targets CCKBR and is significant in suppressing gastric cancer cell growth. Maybe miR-148b would become a potential biomarker and therapeutic target against gastric cancer.

Knockdown of microRNA-21 inhibits proliferation and increases cell death by targeting programmed cell death 4 (PDCD4) in pancreatic ductal adenocarcinoma

OBJECTIVE

This study aims to examine the expression of a panel of five microRNAs (miRNA) in pancreatic ductal adenocarcinoma (PDAC) and the functional effect of miR-21 inhibition in PDAC cell lines.

BACKGROUND

miRNA are short, non-coding RNA molecules, which play important roles in several cellular processes by silencing expression of their target genes through translational repression or mRNA degradation. They are often aberrantly expressed in cancer, and this dysregulation can promote carcinogenesis by altering the expression of tumour suppressor or oncogenes.

METHODS

miRNA expression levels were measured in 24 PDAC tumour/matched adjacent normal tissue samples and three PDAC cell lines using reverse transcription polymerase chain reaction. Levels of cell proliferation and death and expression of programmed cell death 4 (PDCD4; tumour suppressor) were studied in PDAC cells (MIA-Pa-Ca-2) in the absence or presence of a miR-21 inhibitor.

RESULTS

PDAC primary tissues and cell lines displayed a consistent upregulation of miR-21 (P < 0.0001) and downregulation of both miR-148a (P < 0.0001) and miR-375 (P < 0.0001) relative to adjacent normal tissue. Furthermore, miR-21 levels in the primary tumours correlated with disease stage (P < 0.0001). Inhibition of miR-21 in MIA-Pa-Ca-2 PDAC cells led to reduced cell proliferation (P < 0.01) and increased cell death (P < 0.01), with simultaneous increase in levels of the tumour suppressor, PDCD4 (P < 0.01).

CONCLUSION

miRNA expression profiles may be used as biomarkers for detecting pancreatic cancer. Moreover, miR-21 could be a predictor of disease progression and a possible therapeutic target in part by upregulating PDCD4 in pancreatic cancer.

Tissular and soluble miRNAs for diagnostic and therapy improvement in digestive tract cancers

Digestive cancers (e.g., gastric, colorectal, pancreatic or hepatocarcinoma) are among the most frequently reported cancers in the world, and are characterized by invasivity, metastatic potential and poor outcomes. This group includes some of the most critical cancers (among them, are those ranked second to forth in cancer-related mortality) and, despite all sustained efforts, they maintain a profile of low survival rates and lack successful therapies. Discovery of biomarkers that improve disease characterization may make optimized or personalized therapy possible. Novel biomarkers are expected to provide, hopefully, less-invasive or noninvasive diagnostic tools that make possible earlier detection of disease. Also, they may provide a more reliable selection instrument in the drug discovery process. miRNAs, short noncoding RNAs, have emerged in the last few years as significant regulators of cellular activities, controlling protein expression at the post-transcriptional level, with a significant implication in pathology in general and, of most relevance, in cancers. Deregulation of miRNA expression levels and some genetic alterations were demonstrated in various cancers, including digestive cancers. Investigations in tissue samples have provided a considerable amount of knowledge, identifying altered expressions of miRNAs associated with tumorigenesis and tumor progression. Overexpression of some tumor-inducing or tumor-promoting miRNAs was demonstrated, as well as the downregulation of tumor-suppressor miRNAs. Both individual miRNAs, as well as sets of multiple miRNAs, were set up as candidate biomarkers for diagnostics or monitoring, offering relevant insights into tumorigenic mechanisms. Circulating miRNAs were demonstrated as valuable instruments in tumor diagnosis and the prognosis of digestive cancers (affecting the esophagus, stomach, intestine, colorectum, liver and pancreas), and are being investigated thoroughly in order to generate and validate less-invasive diagnostic tools with enhanced sensitivity.

Aberrant expression of miR-203 and its clinical significance in gastric and colorectal cancers

BACKGROUND

MicroRNAs (miRNAs) are small, non-coding RNAs of endogenous origin, they have been increasingly shown to have aberrant expression in many tumor types. miR-203 has not been comprehensively investigated in gastric and colorectal cancers.

METHODS

Total RNA was extracted from tissues of 212 patients with gastric or colorectal cancer as well as from seven gastric and colorectal cell lines. We determined the expression of miR-203 by real-time PCR and calculated using the 2-ΔΔCt method. Then, we assessed miR-203 expression and clinicopathologic characteristics. Finally, we studied the effect of miR-203 on cell proliferation in SGC-7901 cells by MTT.

RESULTS

miR-203 has significantly low expression in colorectal cancer tissues (p < 0.001, paired t test) and cancer cell lines compared to non-tumor counterparts. Moreover, low expression of miR-203 was correlated with tumor size (p = 0.015, non-parametric test) and pT stage (p = 0.005) in colorectal cancer. Although expression of miR-203 was not significant in gastric cancer tissues (p = 0.124), interestingly, miR-203 was correlated with tumor size (p = 0.023), macroscopic type (p = 0.045), and pT stage (p = 0.013). Furthermore, we found miR-203 can inhibit the cell proliferation in SGC-7901 cells.

CONCLUSION

miR-203 may be related to the proliferation and invasion of gastric and colorectal cancers.

MicroRNA in colorectal cancer: from benchtop to bedside

Colon carcinogenesis represents a stepwise progression from benign polyps to invasive adenocarcinomas and distant metastasis. It is believed that these pathologic changes are contributed by aberrant activation or inactivation of protein-coding proto-oncogenes and tumor suppressor genes. However, recent discoveries in microRNA (miRNA) research have reshaped our understanding of the role of non-protein-coding genes in carcinogenesis. In this regard, a remarkable number of miRNAs exhibit differential expression in colon cancer tissues. These miRNAs alter cell proliferation, apoptosis and metastasis through their interactions with intracellular signaling networks. From a clinical perspective, polymorphisms within miRNA-binding sites are associated with the risk for colon cancer, whereas miRNAs isolated from feces or blood may serve as biomarkers for early diagnosis. Altered expression of miRNA or polymorphisms in miRNA-related genes have also been shown to correlate with patient survival or treatment outcome. With further insights into miRNA dysregulation in colon cancer and the advancement of RNA delivery technology, it is anticipated that novel miRNA-based therapeutics will emerge.

The malignant phenotype-associated microRNA in gastroenteric, hepatobiliary and pancreatic carcinomas

IMPORTANCE OF THE FIELD

MicroRNA (miRNA) is a newly discovered class of small and endogenous non-coding RNAs. Many miRNAs exhibit altered expression levels in cancer, and they can affect the cancerous phenotype of malignant cells.

AREAS COVERED IN THIS REVIEW

We review the recent advances in miRNA involvement in human gastroenteric tumor and analyze the clinical and therapeutic opportunities they provide. We envisage future developments toward molecular mechanisms of miRNAs and their potential applications to cancer treatment.

WHAT THE READER WILL GAIN

MiRNAs may reasonably become novel anticancer tools. More investigations should be performed to promote the success of therapeutic-clinical use of miRNAs in cancer.

TAKE HOME MESSAGE

Future studies should focus on identification of new miRNAs and targets, the function and mechanism of miRNA-regulated cancer pathogenesis, the reliable delivery strategy and the novel type of miRNA-based therapy.

MicroRNA dysregulation in gastric cancer: a new player enters the game

Gastric carcinogenesis is a multistep process involving genetic and epigenetic alteration of protein-coding proto-oncogenes and tumor-suppressor genes. Recent discoveries have shed new light on the involvement of a class of noncoding RNA known as microRNA (miRNA) in gastric cancer. A substantial number of miRNAs show differential expression in gastric cancer tissues. Genes coding for these miRNAs have been characterized as novel proto-oncogenes and tumor-suppressor genes based on findings that these miRNAs control malignant phenotypes of gastric cancer cells. In this connection, miRNA dysregulation promotes cell-cycle progression, confers resistance to apoptosis, and enhances invasiveness and metastasis. Moreover, certain polymorphisms in miRNA genes are associated with increased risks for atrophic gastritis and gastric cancer, whereas circulating levels of miRNAs may serve as biomarkers for early diagnosis. Several miRNAs have also been shown to correlate with gastric cancer progression, and thus may be used as prognostic markers. Elucidating the biological aspects of miRNA dysregulation may help us better understand the pathogenesis of gastric cancer and promote the development of miRNA-directed therapeutics against this deadly disease.

MicroRNA expression and its implication for the diagnosis and therapeutic strategies of gastric cancer

MicroRNAs (miRNAs) are a recently discovered category of small RNA molecules that regulate gene expression at the post-transcriptional level. Accumulating evidence indicated that miRNAs are aberrantly expressed in a variety of human cancers and crucial to tumorigenesis. We herein provide a brief review of miRNA biogenesis, function, deregulation and their possible role as oncogenes or tumor suppressors in the pathogenesis of gastric cancer. The role of miRNAs in the carcinogenic effect of Helicobacter pylori infection was also discussed. Finally, we comment on the potential role of miRNAs in improving the current management of gastric cancer.

MicroRNAs in autoimmunity and inflammatory bowel disease: crucial regulators in immune response

MicroRNAs (miRNAs) have recently emerged as a new class of modulators of gene expression at the post-transcriptional level. The function of miRNA is the control of protein production by targeting mRNAs for translational repression or degradation. MiRNAs play a critical role in many biological processes such as cellular proliferation and maturation, apoptosis, regulation of chronic inflammation and development of cancer. It has recently been discovered that miRNAs are differentially expressed in autoimmune diseases (AID) and miRNA regulation may impact in the development or prevention of AID. In this paper we review the importance of miRNAs in AID in particular in inflammatory bowel disease (IBD). IBD is an AID whose pathophysiology remains uncertain. It is generally hypothesized that IBD is caused by the enteric microflora in genetically predisposed patients with an immune dysregulation in the gastrointestinal tract. Knowing the typical miRNA pattern of IBD will improve our knowledge of the pathogenesis of this disease and will lead to future well-focused projects to study the regulatory function of such miRNAs. Furthermore, it is possible that some miRNAs are specific to IBD and could serve as biomarkers with clinical applications for the diagnosis or assessment of disease activity.