A role of the protein Cbl in FGF-2-induced angiogenesis in murine brain endothelial cells

MiR-378 as a biomarker for response to anti-angiogenic treatment in ovarian cancer

OBJECTIVE

To determine the role of miR-378 as a biomarker for anti-angiogenic therapy response in ovarian cancer.

METHODS

Expression of miR-378 was analyzed in ovarian cancer cell lines and human tumors vs. normal ovarian epithelial cells by qRT-PCR. After miR-378 transfection in SKOV3 cells, dysregulated genes were identified using microarray. Data from The Cancer Genome Atlas (TCGA) was utilized to correlate miR-378 expression with progression-free survival (PFS) among patients treated with anti-angiogenic therapy by using Kaplan-Meier and Cox proportional hazards.

RESULTS

MiR-378 was overexpressed in ovarian cancer cells and tumors vs. normal ovarian epithelial cells. Overexpressing miR-378 in ovarian cancer cells altered expression of genes associated with angiogenesis (ALCAM, EHD1, ELK3, TLN1), apoptosis (RPN2, HIPK3), and cell cycle regulation (SWAP-70, LSM14A, RDX). In the TCGA dataset, low vs. high miR-378 expression was associated with longer PFS in a subset of patients with recurrent ovarian cancer treated with bevacizumab (9.2 vs. 4.2months; p=0.04). On multivariate analysis, miR-378 expression was an independent predictor for PFS after anti-angiogenic treatment (HR=2.04, 95% CI: 1.12-3.72; p=0.02). Furthermore, expression levels of two miR-378 targets (ALCAM and EHD1) were associated with PFS in this subgroup of patients who received anti-angiogenic therapy (9.4 vs. 4.2months, p=0.04 for high vs. low ALCAM; 7.9 vs. 2.3months, p<0.01 for low vs. high EHD1).

CONCLUSIONS

Our data suggest that miR-378 is overexpressed in ovarian cancer cells and tumors vs. normal ovarian epithelial cells. MiR-378 and its downstream targets may serve as markers for response to anti-angiogenic therapy.

Radiation-Triggered NF-κB Activation is Responsible for the Angiogenic Signaling Pathway and Neovascularization for Breast Cancer Cell Proliferation and Growth

Tumors require blood supply to survive, grow, and metastasize. This involves the process of angiogenesis signaling for new blood vessel growth into a growing tumor mass. Understanding the mechanism of the angiogenic signaling pathway and neovascularization for breast cancer cell proliferation and growth would help to develop molecular interventions and achieve disease free survival. Our hypothesis is that the surviving cancer cell(s) after radiotherapy can initiate angiogenic signaling pathway in the neighboring endothelial cells resulting in neovascularization for breast cancer cell growth. The angiogenic signaling pathway is initiated by angiogenic factors, VEGF and FGF-2, through activation of a transcriptional regulator NF-κB, which in turn is triggered by therapeutic doses of radiation exposure Human breast adenocarcinoma cells (MCF-7 cells) were exposed to Cesium-137 ((137)Cs) γ rays to a total dose of 2 Gy at a dose rate of 1.03 Gy/min. The results of mobility shift assay showed that radiation at clinical doses (2 Gy) could induce NF-κB DNA-binding activity. Then, we examined the communication of angiogenic signals from irradiated MCF-7 cells to vascular endothelial cells. At the protein level, the western blot showed induction of angiogenic factors VEGF and FGF-2 in MCF-7 cells irradiated with 2 Gy. Inhibition of NF-κB activation attenuated VEGF and FGF-2 levels. These factors are secreted into the medium. The levels of VEGF and FGF-2 in the extra cellular medium were both increased, after 2 Gy exposures. We also observed corresponding expression of VEGFR2 and FGFR1 in non-irradiated endothelial cells that were co-cultured with irradiated MCF-7 cells. In support of this, in vitro tube formation assays provided evidence that irradiated MCF-7 cells transmit signals to potentiate cultured non-irradiated endothelial cells to form tube networks, which is the hallmark of neovascularization. Inhibition of NF-κB activation attenuated irradiated MCF-7-induced tube network formation. The data provide evidence that the radiation exposure is responsible for tumor growth and maintenance by inducing an angiogenic signaling pathway through activation of NF-κB.

Angiopoietin-1-induced ubiquitylation of Tie2 by c-Cbl is required for internalization and degradation

Tie2 [where ‘Tie’ is an acronym from tyrosine kinase with Ig and EGF (epidermal growth factor) homology domains] is a receptor tyrosine kinase expressed predominantly on the surface of endothelial cells. Activated by its ligands, the angiopoietins, Tie2 initiates signalling pathways that modulate vascular stability and angiogenesis. Deletion of either the Tie2 or Ang1 (angiopoietin-1) gene in mice results in lethal vascular defects, signifying their importance in vascular development. The mechanism employed by the Tie2 signalling machinery to attenuate or cause receptor trafficking is not well defined. Stimulation of Tie2-expressing cells with Ang1 results in its ubiquitylation, suggesting that this may provide the necessary signal for receptor turnover. Using a candidate molecule approach, we demonstrate that Tie2 co-immunoprecipitates with c-Cbl in an Ang1-dependent manner and its ubiquitylation can be inhibited by the dominant-interfering molecule v-Cbl (a viral form of c-Cbl that contains only the tyrosine kinase-binding domain region). Inhibition of the Tie2–Cbl interaction by overexpression of v-Cbl blocks ligand-induced Tie2 internalization and degradation. In summary, our results illustrate that c-Cbl interacts with the Tie2 signalling complex in a stimulation-dependent manner, and that this interaction is required for Tie2 ubiquitylation, internalization and degradation.