[Venous pathomorphology in occlusive lesions of the arteries of the lower extremities]

Post-transcriptional regulation of cytokine expression and signaling

Cytokines and cytokine signaling pathways are crucial for regulating cellular functions, including cell growth, proliferation, differentiation, and cell death. Cytokines regulate physiological processes such as immune responses and maintain immune homeostasis, and they also mediate pathological conditions such as autoimmune diseases and cancer. Hence, the precise control of the expression of cytokines and the transduction of cytokine signals is tightly regulated at transcriptional and post-transcriptional levels. In particular, post-transcriptional regulation at the level of mRNA stability is critical for coordinating cytokine expression and cytokine signaling. Numerous cytokine transcripts contain AU-rich elements (AREs), whereas transcripts encoding numerous components of cytokine signaling pathways contain GU-rich elements (GREs). AREs and GREs are mRNA decay elements that mediate rapid mRNA degradation. Through ARE- and GRE-mediated decay mechanisms, immune cells selectively and specifically regulate cytokine networks during immune responses. Aberrant expression and stability of ARE- or GRE-containing transcripts that encode cytokines or components of cytokine signaling pathways are observed in disease states, including cancer. In this review, we focus on the role of AREs and GREs in regulating cytokine expression and signal transduction at the level of mRNA stability.

Cooperative Repression of Insulin-Like Growth Factor Type 2 Receptor Translation by MicroRNA 195 and RNA-Binding Protein CUGBP1

Insulin-like growth factor type 2 (IGF2) receptor (IGF2R) recognizes mannose 6-phosphate-containing molecules and IGF2 and plays an important role in many pathophysiological processes, including gut mucosal adaptation. However, the mechanisms that control cellular IGF2R abundance are poorly known. MicroRNAs (miRNAs) and RNA-binding proteins (RBPs) critically regulate gene expression programs in mammalian cells by modulating the stability and translation of target mRNAs. Here we report that miRNA 195 (miR-195) and RBP CUG-binding protein 1 (CUGBP1) jointly regulate IGF2R expression at the posttranscriptional level in intestinal epithelial cells. Both miR-195 and CUGBP1 interacted with the 3' untranslated region (3'-UTR) of Igf2r mRNA, and the association of CUGBP1 with Igf2r mRNA enhanced miR-195 binding to Igf2r mRNA. Ectopically expressed CUGBP1 and miR-195 repressed IGF2R translation cooperatively without altering the stability of Igf2r mRNA. Importantly, the miR-195- and CUGBP1-repressed levels of cellular IGF2R led to a disruption in the structure of the trans-Golgi network. These findings indicate that IGF2R expression is controlled posttranscriptionally by two factors that associate with Igf2r mRNA and suggest that miR-195 and CUGBP1 dampen IGF signaling by inhibiting IGF2R translation.

Downregulation of HuR Inhibits the Progression of Esophageal Cancer through Interleukin-18

Purpose

The purpose of this study was to investigate the effect of human antigen R (HuR) downregulation and the potential target genes of HuR on the progression of esophageal squamous cell carcinoma (ESCC).

Materials and Methods

In this study, a proteomics assay was used to detect the expression of proteins after HuR downregulation, and a luciferase assay was used to detect the potential presence of a HuR binding site on the 3’-untranslated region (3'-UTR) of interleukin 18 (IL-18). In addition, colony formation assay, MTT, EdU incorporation assay, Western blot, flow cytometry, immunohistochemistry, transwell invasion assay, and wound healing assay were used.

Results

In the present study, we found that the expression of both HuR protein and mRNA levels were higher in tumor tissues than in the adjacent tissues. HuR downregulation significantly suppressed cell proliferation. In addition, the metastasis of esophageal cancer cells was inhibited, while the expression of E-cadherin was increased and the expression of matrix metalloproteinase (MMP) 2, MMP9, and vimentin was decreased after HuR knockdown. Moreover, silencing of HuR disturbed the cell cycle of ESCC cells mainly by inducing G1 arrest. Furthermore, proteomics analysis showed that downregulation of HuR in TE-1 cells resulted in 100 upregulated and 122 downregulated proteins, including IL-18 as a significantly upregulated protein. The expression of IL-18 was inversely regulated by HuR. IL-18 expression was decreased in ESCC tissues, and exogenous IL-18 significantly inhibited the proliferation and metastasis of ESCC cells. The 3'-UTR of IL-18 harbored a HuR binding site, as shown by an in vitro luciferase assay.

Conclusion

HuR plays an important role in the progression of esophageal carcinoma by targeting IL-18, which may be a potential therapeutic target for the treatment of ESCC.

Post-transcriptional regulation of cytokine and growth factor signaling in cancer

Cytokines and growth factors regulate cell proliferation, differentiation, migration and apoptosis, and play important roles in coordinating growth signal responses during development. The expression of cytokine genes and the signals transmitted through cytokine receptors are tightly regulated at several levels, including transcriptional and post-transcriptional levels. A majority of cytokine mRNAs, including growth factor transcripts, contain AU-rich elements (AREs) in their 3' untranslated regions that control gene expression by regulating mRNA degradation and changing translational rates. In addition, numerous proteins involved in transmitting signals downstream of cytokine receptors are regulated at the level of mRNA degradation by GU-rich elements (GREs) found in their 3' untranslated regions. Abnormal stabilization and overexpression of ARE or GRE-containing transcripts had been observed in many malignancies, which is a consequence of the malfunction of RNA-binding proteins. In this review, we briefly summarize the role of AREs and GREs in regulating mRNA turnover to coordinate cytokine and growth factor expression, and we describe how dysregulation of mRNA degradation mechanisms contributes to the development and progression of cancer.

Short hairpin RNA-mediated silencing of insulin-like growth factor-Ⅰ receptor inhibits proliferation of hepatoma cells

AIM: To investigate the effect of short hairpin RNA (shRNA)-mediated silencing of insulin-like growth factor-Ⅰ  receptor (IGF-ⅠR) gene transcription on cell proliferation, cell cycle progression, apoptosis and sensitivity to targeted therapy and chemotherapy in hepatocellular carcinoma (HCC) cell lines PLC/PRF/5 and Bel-7404.

METHODS: Pairs of IGF-ⅠR shRNAs were designed and synthesized based on the IGF-ⅠR sequence, and inserted into the pGPU6/GFP/Neo vector to screen the most effective one. IGF-ⅠR expression was then down-regulated with the shRNA to observe its inhibitory effect on hepatoma cell proliferation.

RESULTS: After screening, the IGF-ⅠR-shRNA4 was found to be the most efficient one for interfering IGF-ⅠR gene transcription among the 4 pairs of successfully constructed plasmids, with a transfection efficiency of 71% in PLC/PRF/5 cells and 90% in Bel-7404 cells. The expression of IGF-ⅠR mRNA was down-regulated by 59.6% ± 2.8% in PLC/PRF/5 cells and 54.9% ± 2.6% in Bel-7404 cells. After the cells was transfected with shRNA4 for 72 h, the reduced rate of cell proliferation was 61.47% ± 1.70% in Bel-7404 cells (t = 5.493, P < 0.005) and 63.87 ± 3.90% (t = 19.244, P < 0.001) in PLC/PRF/5 cells. Meanwhile, the cell cycle was arrested in the G1 phase, and the expression of Cyclin D1 was significantly down-regulated with increasing cell apoptosis. Besides, the combination of shRNA4 with sorafenib or oxaliplatin showed higher inhibitory effects on cell survival than shRNA4 alone.

CONCLUSION: Silencing IGF-ⅠR gene transcription can inhibit hepatoma cell proliferation, induce apoptosis and enhance the sensitivity to targeted therapy and chemotherapy. IGF-ⅠR may be a potential target gene for HCC gene therapy.