RTK signaling requires C3ar1/C5ar1 and IL-6R joint signaling to repress dominant PTEN, SOCS1/3 and PHLPP restraint

How receptor tyrosine kinase (RTK) growth signaling is controlled physiologically is incompletely understood. We have previously provided evidence that the survival and mitotic activities of vascular endothelial cell growth factor receptor-2 (VEGFR2) signaling are dependent on C3a/C5a receptor (C3ar1/C5ar1) and IL-6 receptor (IL-6R)-gp130 joint signaling in a physically interactive platform. Herein, we document that the platelet derived and epidermal growth factor receptors (PDGFR and EGFR) are regulated by the same interconnection and clarify the mechanism underlying the dependence. We show that the joint signaling is required to overcome dominant restraint on RTK function by the combined repression of tonically activated PHLPP, SOCS1/SOCS3, and CK2/Fyn dependent PTEN. Signaling studies showed that augmented PI-3Kɣ activation is the process that overcomes the multilevel growth restraint. Live-cell flow cytometry and single-particle tracking indicated that blockade of C3ar1/C5ar1 or IL-6R signaling suppresses RTK growth factor binding and RTK complex formation. C3ar1/C5ar1 blockade abrogated growth signaling of four additional RTKs. Active relief of dominant growth repression via joint C3ar1/C5ar1 and IL-6R joint signaling thus enables RTK mitotic/survival signaling.

VEGFR2 survival and mitotic signaling depends on joint activation of associated C3ar1/C5ar1 and IL-6R-gp130

Purified vascular endothelial cell (EC) growth factor receptor-2 (VEGFR2) auto-phosphorylates upon VEGF-A occupation in vitro, arguing that VEGR2 confers its mitotic and viability signaling in and of itself. Herein, we show that, in ECs, VEGFR2 function requires concurrent C3a/C5a receptor (C3ar1/C5ar1) and IL-6 receptor (IL-6R)-gp130 co-signaling. C3ar1/C5ar1 or IL-6R blockade totally abolished VEGFR2 auto-phosphorylation, downstream Src, ERK, AKT, mTOR and STAT3 activation, and EC cell cycle entry. VEGF-A augmented production of C3a/C5a/IL-6 and their receptors via a two-step p-Tyk2/p-STAT3 process. Co-immunoprecipitation analyses, confocal microscopy, ligand pulldown and bioluminescence resonance energy transfer assays all indicated that the four receptors are physically interactive. Angiogenesis in murine day 5 retinas and in adult tissues was accelerated when C3ar1/C5ar1 signaling was potentiated, but repressed when it was disabled. Thus, C3ar1/C5ar1 and IL-6R-gp130 joint activation is needed to enable physiological VEGFR2 function.

Abstract 3862: Isolation and nanoscale visualization of glioblastoma stem-like cells utilizing the Notch1 receptor

Tumor eradication is an elusive goal in modern medicine. This unmet goal is in part due to the imprecise therapeutic targeting of a specific population of cells having “stem-like” properties. These stem-like tumor cells can remain almost senescent during chemotherapeutic interventions to evade treatment and produce genetically different secondary tumor lineages than their parental tumors. Here we develop a novel approach that utilizes the Notch1 receptor, found on the surface of glioma cells, to isolate a population of cells bearing stem-like properties. We identified this population to be Nestin+GFAP-, capable of serum differentiation into Nestin-GFAP+ cells, and self-regenerating. In addition, this unique population of cells has increased stem-like qualities compared to the CD133 marker. Utilizing affinity nanocapture grids, we were able to visualize Notch1+ stem-like cells and the perforation of their plasma membranes by unlabeled gold nanorods via electron microscopy. Previous studies have shown that tumor stem-like cells can exist within the larger tumor milieu, representing a potential threat to recurrence. We propose that 1) Notch1 may serve as a novel marker to define glioblastoma stem-like cells, capable of being used for targeting chemotherapeutic approaches in the future, and 2) affinity nanocapture grids represent a unique method for examining individual living cells at the nanoscale.

Citation Format: Elliot Pohlmann, Susan Murphy, Debbie Kelly, Zhi Sheng. Isolation and nanoscale visualization of glioblastoma stem-like cells utilizing the Notch1 receptor. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 3862. doi:10.1158/1538-7445.AM2014-3862