Downregulation of miR-145-5p correlates with poor prognosis in gastric cancer.

OBJECTIVE: The aim of this study was to explore the clinical significance of miR-145-5p expression in gastric cancer (GC). PATIENTS AND METHODS: Expression of miR-145-5p was evaluated by qRT- PCR in tumor and normal gastric tissues in 145 GC patients. The correlation between the miR-145-5p expression and clinicopathological parameters was investigated. Finally, the survival was assessed by the Kaplan-Meier method and proportional hazards model. RESULTS: Expression levels of miR-145-5p in GC tissues were significantly lower than those in adjacent normal tissues (p < 0.001). MiR-145-5p expression was significantly associated with lymph node metastasis, metastasis stage, and distant metastasis (all p < 0.05). Furthermore, Patients with low miR-145-5p expression had poorer overall survival time than those with high miR-145-5p expression (p = 0.014). Moreover, univariate and multivariate Cox analysis showed that miR-145-5p was an independent prognostic indicator for OS (p = 0.011). CONCLUSIONS: MiR-145-5p is down-expressed in GC, and can be used as a marker of poor prognosis in GC patients.

Adenovirus KH901 promotes 5-FU antitumor efficacy and S phase in LoVo cells.

A combination of oncolytic and chemotherapeutic agents has been used to kill cancer cells. However, the effect of oncolytic adenoviruses on the cell cycle remains to be determined. Cytotoxicity assays were performed to determine cell death in cells treated with 5-fluorouracil (5-FU) alone or in combination with the oncolytic adenovirus KH901. Dynamic changes in the cell cycle, cell proliferation, and apoptosis-related proteins including p-AKT, Bcl-2, Bax, and caspase 3 were investigated after treatment with 5-FU with or without KH901. A higher proportion of S-phase cells were observed after treatment with KH901 and 5-FU than with 5-FU alone. p-AKT, Bcl-2, and Bax expression was increased upon treatment with KH901, whereas the expression of caspase-3 was not induced upon treatment with KH901 with or without 5-FU. KH901 exhibited significant potential as an oncolytic adenovirus and increased cell death in combination with 5-FU in LoVo cells, as compared to 5-FU alone. In conclusion, KH901 stimulates LoVo cells to enter the S-phase by activation of p-AKT, which could partly explain its synergistic effect with 5-FU on LoVo cell cytotoxicity.

Inhibition of epidermal growth factor-like growth factor secretion in tracheobronchial epithelial cells by vitamin A.

Vitamin A deficiency of respiratory tract epithelium results in the phenomenon of squamous cell metaplasia. The mechanisms by which vitamin A regulates airway epithelial cell growth and differentiation are not completely understood. In this study, we focused on the effects of vitamin A (retinol) on growth of human and non-human primate tracheobronchial epithelial (TBE) cells in culture. Retinol and its derivatives have little growth-stimulatory effect on TBE cells that are maintained in primary culture in a serum-free medium supplemented with 6 hormonal supplements: insulin, transferrin, epidermal growth factor (EGF), hydrocortisone, cholera toxin, and bovine hypothalamus extract. However, it was observed that retinol exhibited dose-dependent inhibition of TBE cell growth when EGF was removed from this serum-free culture condition. This inhibition can be reversed if EGF or the conditioned medium of primary TBE cells that are maintained in vitamin A-deficient condition is added. This type of EGF-retinol interacting phenomenon was not observed with the 5 remaining hormonal supplements. Analysis of 125I-labeled EGF binding shows a down-regulation of the high affinity binding sites (Kd = 0.09 nM) on TBE cells grown in the absence of vitamin A. These results suggest that TBE cells are capable of secreting an EGF-like growth factor in the absence of vitamin A. The possibility that transforming growth factor-alpha (TGF-alpha) is involved in this phenomenon is further examined by antibodies specific to TGF-alpha and its binding to an EGF-receptor. Using the TGF-alpha antibody, the presence of a TGF-alpha-specific antigen was found to be 3-fold higher in the conditioned medium obtained from the vitamin A-deficient cultures than that derived from retinol-treated cultures. Furthermore, the antibody neutralizing the TGF-alpha binding to an EGF receptor was able to reduce the DNA synthesis associated with the vitamin A deficiency. These results suggest that vitamin A plays an important regulatory role in the paracrine/autocrine secretion of EGF/TGF-alpha-like mitogen in TBE cell cultures.

Regulation of DNA replication in vitro by the transcriptional activation domain of GAL4-VP16.

Studies of DNA viruses have provided evidence that eukaryotic transcriptional activator proteins can enhance the efficiency of DNA replication as well as transcription. The mechanism of this effect was studied in vitro using the chimeric transcription factor GAL4-VP16 and a DNA template containing GAL4 binding sites adjacent to the simian virus 40 origin of DNA replication. The binding of GAL4-VP16 prevented the repression of DNA replication which otherwise occurred when the template was assembled into chromatin. Relief of repression by GAL4-VP16 required both its DNA-binding and transcriptional activation domains but did not require RNA synthesis. The results are consistent with a general model in which transcriptional activators stimulate eukaryotic DNA replication by modifying the outcome of the competition between initiation factors and histones for occupancy of the origin.