Down-Regulation of PDCD4 Promotes Proliferation, Angiogenesis and Tumorigenesis in Glioma Cells

The programmed cell death 4 (PDCD4) tumor-suppressor gene regulates cell apoptosis, protein translation, signal transduction, and induction of mediators of inflammation. However, the mechanism by which PDCD4 is down-regulated and regulates tumor growth remains elusive. In this study, we showed that PDCD4 is down-regulated in glioma cells and acts as a tumor suppressor. Based on the TCGA data, we confirmed that AKT2, but not AKT1 or AKT3, interacts with PDCD4, thus leading to the suppression of PDCD4 in glioma cells. Moreover, the analysis suggested that PDCD4 regulates the expression of IL-5, CCL-5, VEGF, and CXCL10 via the NF-kB pathway. Additionally, depletion of levels of PDCD4 promoted angiogenic activity of glioma cells via the VEGF-STAT3 pathway. When tumor cells over-expressing PDCD4 were injected into nude mice, the increased expression of PDCD4 blocked tumorigenesis and prolonged overall survival. Our study indicates the need to develop drugs that can modulate the expression of PDCD4 and test their efficacy in clinical trials.

Gastrin Enhances Autophagy and Promotes Gastric Carcinoma Proliferation via Inducing AMPKα

Gastric cancer (GC) is one of the most frequent epithelial malignancies worldwide. The gastrointestinal (GI) peptide gastrin is an important regulator of the secretion and release of gastric acid from stomach parietal cells, and it also plays a vital role in the development and progression of GC. The aim of the current study was to investigate the role and underlying mechanism of gastrin and autophagy in regulating GC tumorigenesis. Gastrin-17 amide (G-17) was applied in the GC cell lines SGC7901 and MGC-803. The results showed that G-17 maintained the high viability of SGC7901 and MGC-803. The expression of autophagy marker proteins LC3II and Beclin1 was significantly increased, while the autophagy substrate p62 was obviously decreased in the gastrin group compared with the control group. Moreover, G-17 strengthened the expressions of AMPKα, Ras, Raf, MEK, and ERK1/2. Additionally, administration of AMPKα siRNA counteracted the effect of gastrin in SGC7901 cells. Finally, in an in vivo study of the tumor growth and survival rate of rats, the levels of AMPKα/Ras/Raf/MEK/ERK were significantly increased in the gastrin group and decreased following AMPKα shRNA injection. In conclusion, these findings indicate that gastrin plays a tumorigenic role by promoting autophagy in GC and may provide a novel therapeutic target for GC treatment.