The putative tumor suppressor microRNA-497 modulates gastric cancer cell proliferation and invasion by repressing eIF4E

Accumulating evidence has shown that microRNAs are involved in multiple processes in gastric cancer (GC) development and progression. Aberrant expression of miR-497 has been frequently reported in cancer studies; however, the role and mechanism of its function in GC remains unknown. Here, we reported that miR-497 was frequently downregulated in GC tissues and associated with aggressive clinicopathological features of GC patients. Further in vitro observations showed that the enforced expression of miR-497 inhibited cell proliferation by blocking the G1/S transition and decreased the invasion of GC cells, implying that miR-497 functions as a tumor suppressor in the progression of GC. In vivo study indicated that restoration of miR-497 inhibited tumor growth and metastasis. Luciferase assays revealed that miR-497 inhibited eIF4E expression by targeting the binding sites in the 3′-untranslated region of eIF4E mRNA. qRT-PCR and Western blot assays verified that miR-497 reduced eIF4E expression at both the mRNA and protein levels. A reverse correlation between miR-497 and eIF4E expression was noted in GC tissues. Taken together, our results identify a crucial tumor suppressive role of miR-497 in the progression of GC and suggest that miR-497 might be an anticancer therapeutic target for GC patients.     

MiR-150 promotes gastric cancer proliferation by negatively regulating the pro-apoptotic gene EGR2

Accumulating evidence suggests small non-coding RNAs (microRNAs) play important roles in human cancer progression. In the present study, we found miR-150 was overexpressed in gastric cancer cell lines and tissues. Ectopic expression of miR-150 promoted tumorigenesis and proliferation of gastric cancer cells. Luciferase reporter assay demonstrated that EGR2 was a direct target of miR-150. Collectively, our study demonstrated that overexpression of miR-150 in gastric cancer could promote proliferation and growth of cancer cells at least partially through directly targeting the tumor-suppressor EGR2, suggesting a potential strategy for the development of miRNA-based treatment of gastric cancer.     

MicroRNA-650 targets ING4 to promote gastric cancer tumorigenicity

MicroRNAs (miRNAs) are non-coding RNAs that regulate the expression of target mRNAs. Altered expression of specific miRNAs in human gastric cancer progression has been reported; however, the role of miR-650 in gastric cancer is poorly understood. In this study, we show that miR-650 is involved in lymphatic and distant metastasis in human gastric cancer, and we find that ectopic expression of miR-650 promotes tumorigenesis and proliferation of gastric cancer cells. A luciferase reporter assay demonstrates that Inhibitor of Growth 4 (ING4) is a direct target of miR-650. Collectively, our study demonstrates that over-expression of miR-650 in gastric cancer may promote proliferation and growth of cancer cells, at least partially through directly targeting ING4. These findings help clarify the molecular mechanisms involved in gastric carcinogenesis and indicate that miR-650 modulation may be a bona fide miRNA-based treatment of gastric cancer.     

Cytokine-stimulated T lymphocyte proliferation is regulated by p27Kip1

T lymphocyte growth is regulated by the cyclin-dependent kinase inhibitor p27(Kip1). Mice deficient in p27(Kip1) have increased proliferative responses to multiple cytokines, including IL-2, IL-4, and IL-12, but not to anti-CD3. In the absence of p27(Kip1), T cells proliferate faster than control cells, as evidenced by increased [(3)H]thymidine uptake, increased cell growth and division, and an increased number of cells in S phase. Importantly, this regulation is specific for p27(Kip1) in T cells, because hyperproliferation of T cells from mice deficient in p21(Cip1/Waf1) was not observed. In vivo, there is an expansion of activated/memory CD4(+) cells in p27(Kip1)-deficient mice before and after immunization. Furthermore, Ag-stimulated spleen cells from immunized p27(Kip1)-deficient mice demonstrated increased proliferative responses to IL-2 and increased secretion of IFN-gamma. Although IL-4 stimulated proliferative responses are diminished in Stat6-deficient T cells, activated T cells from mice doubly deficient in both p27(Kip1) and Stat6 recover normal proliferative responses to IL-4. Together, these data firmly support a role for p27(Kip1) as a negative regulator of cytokine-stimulated T cell growth.     

miR-17-5p promotes proliferation by targeting SOCS6 in gastric cancer cells

This study aimed to test the exact functions and potential mechanisms of miR-17-5p in gastric cancer. Using real-time PCR, miR-17-5p was found to be expressed more highly in gastric cancer compared with-normal tissues. Gain- and loss-of-function assays demonstrated that miR-17-5p increased the proliferation and growth of gastric cancer cells in vitro and in vivo. Through reporter gene and western blot assays, SOCS6 was shown to be a direct target of miR-17-5p, and proliferative assays confirmed that SOCS6 exerted opposing function to that of miR-17-5p in gastric cancer. In short, miR-17-5p might function as a pro-proliferative factor by repressing SOCS6 in gastric cancer.     

MicroRNA-490-5p inhibits proliferation of bladder cancer by targeting c-Fos

MicroRNAs (miRNAs) are non-protein-coding sequences that play a crucial role in tumorigenesis by negatively regulating gene expression. Here, we found that miR-490-5p is down-regulated in human bladder cancer tissue and cell lines compared to normal adjacent tissue and a non-malignant cell line. To better characterize the function of miR-490-5p in bladder cancer, we over-expressed miR-490-5p in bladder cancer cell lines with chemically synthesized mimics. Enforced expression of miR-490-5p in bladder cancer cells significantly inhibited the cell proliferation via G1-phase arrest. Further studies found the decreased c-Fos expression at both mRNA and protein levels and Luciferase reporter assays demonstrated that c-Fos is a direct target of miR-490-5p in bladder cancer. These findings indicate miR-490-5p to be a novel tumor suppressor of bladder cancer cell proliferation through targeting c-Fos.     

Down-regulation of microRNA-200b is a potential prognostic marker of lung cancer in southern-central Chinese population

MicroRNAs (miRNAs) may regulate diverse biological processes and play an important role in cancer. And MiRNAs have been proposed as a useful tool for lung cancer diagnosis and therapeutics in cancer. The purpose of the present study was to investigate the association among the expression level of mature miR-200b-5p in peripheral blood and the risk of lung cancer and clinic pathological characteristics. This case-control study included 24 patients with lung cancer and 12 healthy controls. MiR-200b expression was deleted using real-time PCR. and the miR-200b expression of normal controls was significantly higher than that in lung cancer patients (1732.13?pg/mL vs 881.67?pg/mL, P?<?0.05), no difference with age, sex, tissue type and clinical stage of lung cancer patients (P?>?0.05). Furthermore, miR-200b expression level fluctuated with tumor progression in lung cancer, and there was highly significant for clinical stage II compared with the clinical stage III (P?<?0.05). In addition, the down-regulation of miR-200b showed a highly discriminative receiver operating characteristic (ROC) curve profile, clearly distinguishing cancer patients from cancer-free subjects with an area under the ROC curve (AUROC) of 0.87. The detection of miR-200b expression yielded 83.30% sensitivity and 100.00% specificity in the diagnosis of lung cancer. Therefore, these findings suggested that miR-200b may be used as a marker for the detection and diagnosis of lung cancer in peripheral blood.     

Upregulation of MicroRNA-107 induces proliferation in human gastric cancer cells by targeting the transcription factor FOXO1

MicroRNA-107 (miR-107) has been demonstrated to regulate proliferation and apoptosis in many types of cancers. Nevertheless, its biological function in gastric cancer remains largely unexplored. Here, we found that the expression level of miR-107 was increased in gastric cancer in comparison with the adjacent normal tissues. The enforced expression of miR-107 was able to promote cell proliferation in NCI-N87 and AGS cells, while miR-107 antisense oligonucleotides (antisense miR-107) blocked cell proliferation. At the molecular level, our results further revealed that expression of FOXO1 was negatively regulated by miR-107. Therefore, the data reported here demonstrate that miR-107 is an important regulator in gastric cancer, which will contribute to a better understanding of the important mis-regulated miRNAs in gastric cancer.     

Regulatory effects of lncRNA ATB targeting miR-200c on proliferation and apoptosis of colorectal cancer cells

This investigation was intended to elucidate whether long noncoding RNA (lncRNA)-activated by transforming growth factor-β (ATB) interacting with miR-200c could mediate colorectal cancer (CRC) progression, offering potential strategies for diagnosing and treating CRC. Here totally 315 patients with CRC were recruited, and their CRC tissues and adjacent normal tissues were gathered. Concurrently, four colon cancer cell lines (ie, SW620, Lovo, HCT116, and SW480) and the human colon mucosal epithelial cell line (NCM460) were also purchased. Moreover, si-ATB, si-NC, miR-200c mimic, miR-200c inhibitor, and miR-NC were prepared for transfection into the CRC cells, and their effects on CRC cell lines were evaluated based on the conduction of 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay, colony formation assay, and flow cytometry assay. Eventually, the Luciferase reporter gene assay was carried out to judge if there existed a targeted relationship between ATB and miR-200c. The results of Cox regression analyses suggested that overexpressed lncRNA ATB, underexpressed miR-200c, poor tumor differentiation, lymph-vascular invasion, and perineural invasion were symbolic of shortened survival of the patients with CRC (all P < .05). Besides, transfection of pcDNA3.1-ATB and miR-200c inhibitor could boost the viability and proliferation of Lovo and SW620 cell lines (all P < .05). Meanwhile, the expressions of p53 and p21 were also reduced under treatments of pcDNA3.1-ATB and miR-200c inhibitor (P < .05). In addition, CDK2 seemed to reverse the contribution of miR-200c to intensifying viability and proliferation of Lovo and SW420 cell lines (P < .05). Furthermore, ATB might downregulate miR-200c expression by targeting it (P < .05), and CDK2 was subjected to dual regulation of both ATB and miR-200c (P < .05). In conclusion, the lncRNA ATB/miR-200c/CDK2 signaling was responsible for intensified proliferation and prohibited apoptosis of CRC cells, which might provide effective approaches for diagnosing and treating CRC.     

Matrix metalloproteinase 11 depletion inhibits cell proliferation in gastric cancer cells

Our previous study has shown that matrix metalloproteinase 11 (MMP11) is highly expressed in tumor cell lines and primary tumor of gastric cancer (GC). In order to reveal the correlation between expression of MMP11 and biological features of GC cell, we have constructed the recombinant plasmids producing hairpin small interfering RNA (siRNA) to target MMP11 mRNA using a vector-based RNA interference technology. Stable transfection of recombinants into GC cell line BGC823 specifically depleted the mRNA and protein of MMP11 as demonstrated by RT-PCR and Western blotting analysis. The siRNA-treated cells exhibited significantly decreased growth ability compared with mock transfectants and parental BGC823 cells. Furthermore, colony formation of MMP11 deficient cells was dramatically inhibited in soft agar and tumorigenicity was reduced in nude mice, respectively. These results provide new insights into the function of MMP11 and suggest that MMP11 may play an important role in the control of cell proliferation and tumor development in GC.     

Connexin32 inhibits gastric carcinogenesis through cell cycle arrest and altered expression of p21Cip1 and p27Kip1

Gap junctions and their structural proteins, connexins (Cxs), have been implicated in carcinogenesis. To explore the involvement of Cx32 in gastric carcinogenesis, immunochemical analysis of Cx32 and proliferation marker Ki67 using tissue-microarrayed human gastric cancer and normal tissues was performed. In addition, after Cx32 overexpression in the human gastric cancer cell line AGS, cell proliferation, cell cycle analyses, and p21^Cip1 and p27^Kip1 expression levels were examined by bromodeoxyuridine assay,flow cytometry, real-time RT-PCR, and western blotting. Immunohistochemical study noted a strong inverse correlation between Cx32 and Ki67 expression pattern as well as theirlocation. In vitro, overexpression of Cx32 in AGS cells inhibited cell proliferation significantly. G₁ arrest, up-regulation of cell cycle-regulatory proteins p21^Cip1 and p27^Kip1 was also found at both mRNA and protein levels. Taken together, Cx32 plays some roles in gastric cancer development by inhibiting gastric cancer cell proliferation through cell cycle arrest and cell cycle regulatory proteins. [BMB Reports 2013; 46(1): 25-30]     

Antibiotic drug tigecycline inhibited cell proliferation and induced autophagy in gastric cancer cells

Tigecycline acts as a glycylcycline class bacteriostatic agent, and actively resists a series of bacteria, specifically drug fast bacteria. However, accumulating evidence showed that tetracycline and their derivatives such as doxycycline and minocycline have anti-cancer properties, which are out of their broader antimicrobial activity. We found that tigecycline dramatically inhibited gastric cancer cell proliferation and provided an evidence that tigecycline induced autophagy but not apoptosis in human gastric cancer cells. Further experiments demonstrated that AMPK pathway was activated accompanied with the suppression of its downstream targets including mTOR and p70S6K, and ultimately induced cell autophagy and inhibited cell growth. So our data suggested that tigecycline might act as a candidate agent for pre-clinical evaluation in treatment of patients suffering from gastric cancer.     

MicroRNA-490-3p inhibits proliferation of A549 lung cancer cells by targeting CCND1

MicroRNAs (miRNAs) are small non-coding RNAs that negatively regulate the translation of messenger RNAs by binding their 3′-untranslated region (3′UTR). In this study, we found that miR-490-3p is significantly down-regulated in A549 lung cancer cells compared with the normal bronchial epithelial cell line. To better characterize the role of miR-490-3p in A549 cells, we performed a gain-of-function analysis by transfecting the A549 cells with chemically synthesized miR-490-3P mimics. Overexpression of miR-490-3P evidently inhibits cell proliferation via G1-phase arrest. We also found that forced expression of miR-490-3P decreased both mRNA and protein levels of CCND1, which plays a key role in G1/S phase transition. In addition, the dual-luciferase reporter assays indicated that miR-490-3P directly targets CCND1 through binding its 3′UTR. These findings indicated miR-490-3P could be a potential suppressor of cellular proliferation.