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Objective: To investigate the expression of long non-coding RNA (lncRNA) H19 in mouse GC-1 cells in vitro and its effects on the proliferation and apoptosis of GC-1 cells., Methods: We established an in vitro hypoxia-reoxygenation model in GC-1 cells and detected the expression of lncRNA H19 in the GC-1 cells at different time points of reoxygenation injury by qRT-PCR. We determined the effects of silencing lncRNA H19 on the proliferation and apoptosis of the GC-1 cells by MTT and flow cytometry, the expressions of apoptosis-related proteins Bax and caspase-3 in the GC-1 cells by Western blot, and the expressions of microRNA-203a and PTEN by qRT-PCR and Western blot, respectively., Results: With the prolonging of the time of reoxygenation injury, the expression of lncRNA H19 was increased significantly in the GC-1 cells and peaked at 3-hour hypoxia and 12-hour reoxygenation, but that of microRNA-203a markedly decreased. Silencing lncRNA H19 enhanced the proliferation and inhibited the apoptosis of the GC-1 cells, and up-regulated the expression of microRNA-203a and down-regulated that of PTEN in the GC-1 cells., Conclusions: LncRNA H19 is highly expressed in GC-1 cells in vitro, which may influence the proliferation and apoptosis of GC-1 cells by regulating the microRNA-203a /PTEN signaling pathway.

MicroRNAs (miRNAs) play critical roles in tumorigenesis by modulating the expression of target gene mRNAs. However, their role in cell signaling is not well defined. In this study, we identified miR-30d as a downstream effector of the phosphoinositide 3-kinase (PI3K)/Akt signaling pathway in renal cell carcinoma (RCC) cells. We show that Akt inhibition transcriptionally up-regulates miR-30d expression through activation of the transcription factor forkhead box O (FOXO) 3A. Functional analysis revealed that miR-30d overexpression suppresses cell proliferation and induces apoptosis in RCC cells, suggesting that miR-30d acts as a tumor suppressor. In searching for downstream targets of miR-30d, we found that miR-30d post-transcriptionally suppresses expression of the oncoprotein metadherin (MTDH) by destabilizing its mRNA. Furthermore, we found that FOXO down-regulates MTDH expression through up-regulating expression of miR-30d. Thus, our findings reveal a new Akt/FOXO/miR-30d/MTDH signaling transduction pathway and identify miR-30d as a tumor suppressor, providing a new potential target for the treatment of RCC., (Copyright © 2013 Elsevier Inc. All rights reserved.)

DNA fragmentation factor (DFF)/caspase-activated DNase (CAD) is responsible for DNA fragmentation, a hallmark event during apoptosis. Although DNA fragmentation is an evolutionarily conserved process across species, its biological function is not clearly understood. In this study, we constructed cell lines expressing a mutant ICAD (inhibitor of CAD) protein that is resistant to caspase cleavage and therefore constantly binds to DFF/CAD and inhibits DNA fragmentation. We found that irradiation of these cells led to increased chromosome aberrations and aneuploidy when compared with their parental controls. The increased chromosome instability is observed irrespective of cellular P53 status, suggesting that the effect of DFF/CAD is independent of P53. Inhibition of apoptotic DNA fragmentation resulted in increased clonogenic survival of irradiated cells and a delay in removal of cells with DNA damages induced by radiation, an effect similar to that in cells with p53 mutations. Consistent with DFF/CAD's effect on clonogenic survival, tumors established from cells deficient in DNA fragmentation showed enhanced growth in nude mice. Therefore, our results suggest that DFF/CAD plays an important and P53-independent role in maintaining chromosome stability and suppressing tumor development.