E2F1 promote the aggressiveness of human colorectal cancer by activating the ribonucleotide reductase small subunit M2.

As the ribonucleotide reductase small subunit, the high expression of ribonucleotide reductase small subunit M2 (RRM2) induces cancer and contributes to tumor growth and invasion. In several colorectal cancer (CRC) cell lines, we found that the expression levels of RRM2 were closely related to the transcription factor E2F1. Mechanistic studies were conducted to determine the molecular basis. Ectopic overexpression of E2F1 promoted RRM2 transactivation while knockdown of E2F1 reduced the levels of RRM2 mRNA and protein. To further investigate the roles of RRM2 which was activated by E2F1 in CRC, CCK-8 assay and EdU incorporation assay were performed. Overexpression of E2F1 promoted cell proliferation in CRC cells, which was blocked by RRM2 knockdown attenuation. In the migration and invasion tests, overexpression of E2F1 enhanced the migration and invasion of CRC cells which was abrogated by silencing RRM2. Besides, overexpression of RRM2 reversed the effects of E2F1 knockdown partially in CRC cells. Examination of clinical CRC specimens demonstrated that both RRM2 and E2F1 were elevated in most cancer tissues compared to the paired normal tissues. Further analysis showed that the protein expression levels of E2F1 and RRM2 were parallel with each other and positively correlated with lymph node metastasis (LNM), TNM stage and distant metastasis. Consistently, the patients with low E2F1 and RRM2 levels have a better prognosis than those with high levels. Therefore, we suggest that E2F1 can promote CRC proliferation, migration, invasion and metastasis by regulating RRM2 transactivation. Understanding the role of E2F1 in activating RRM2 transcription will help to explain the relationship between E2F1 and RRM2 in CRC and provide a novel predictive marker for diagnosis and prognosis of the disease.

GATA2/FGF21 Axis Regulates the Effects of High Glucose on the Apoptosis, Autophagy and Oxidative Stress of Human Umbilical Vein Endothelial Cell via PI3K/AKT/mTOR Pathway.

OBJECTIVE: We investigated the role and mechanism of GATA-binding factor 2/Fibroblast growth factor 21 (GATA2/FGF21) axis in high glucose (HG)-induced injury in human umbilical vein endothelial cells (HUVEC). METHODS: After HG treatment and transfection, the viability and apoptosis of HUVECs were determined via Cell Counting Kit-8 and Hoechst 33258 staining methods, and the content of lactate dehydrogenase (LDH) and reactive oxygen species (ROS) was measured via colorimetric assay and DCFH-DA staining. The potential transcription factor of FGF21 was predicted with bioinformatic analysis and confirmed via dual-luciferase reporter assay and chromatin immunoprecipitation. The expressions of GATA2/FGF21, apoptosis-, autophagy- and phosphatidylinositol 3-kinase (PI3K)/AKT/mammalian target of rapamycin (mTOR) pathway-related factors were quantified with quantitative real-time polymerase chain reaction or Western blot. RESULTS: Overexpressed FGF21 abolished the effects of HG on repressing the expressions of FGF21 and cell viability, and promoting apoptosis, the levels of LDH and ROS and autophagy in HUVECs, with increased Bcl-2 and p62 expression yet decreased Bax, Cleaved PARP, Cleaved caspase-3, LC3 II/LC3 I ratio and Beclin 1. GATA2 was the transcription factor of FGF21 and was downregulated after HG treatment, and the effects of overexpressed FGF21 in HG-treated HUVECs were all reversed after the silence of GATA2. Besides, overexpressed FGF21 promoted the activation of PI3K/AKT/mTOR pathway, with increased phosphorylation levels of PI3K, AKT and mTOR, whereas silencing GATA2 abolished the trend. CONCLUSION: GATA2/FGF21 axis has a protective function against HG in HUVEC via regulating PI3K/AKT/mTOR pathway.