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Although it is well established that tumors initiate an angiogenic switch, the molecular basis of this process remains incompletely understood. Here we show that the miRNA miR-132 acts as an angiogenic switch by targeting p120RasGAP in the endothelium and thereby inducing neovascularization. We identified miR-132 as a highly upregulated miRNA in a human embryonic stem cell model of vasculogenesis and found that miR-132 was highly expressed in the endothelium of human tumors and hemangiomas but was undetectable in normal endothelium. Ectopic expression of miR-132 in endothelial cells in vitro increased their proliferation and tube-forming capacity, whereas intraocular injection of an antagomir targeting miR-132, anti–miR-132, reduced postnatal retinal vascular development in mice. Among the top-ranking predicted targets of miR-132 was p120RasGAP, which we found to be expressed in normal but not tumor endothelium. Endothelial expression of miR-132 suppressed p120RasGAP expression and increased Ras activity, whereas a miRNA-resistant version of p120RasGAP reversed the vascular response induced by miR-132. Notably, administration of anti–miR-132 inhibited angiogenesis in wild-type mice but not in mice with an inducible deletion of Rasa1 (encoding p120RasGAP). Finally, vessel-targeted nanoparticle delivery1 of anti–miR-132 restored p120RasGAP expression in the tumor endothelium, suppressed angiogenesis and decreased tumor burden in an orthotopic xenograft mouse model of human breast carcinoma. We conclude that miR-132 acts as an angiogenic switch by suppressing endothelial p120RasGAP expression, leading to Ras activation and the induction of neovascularization, whereas the application of anti–miR-132 inhibits neovascularization by maintaining vessels in the resting state.

Integrin ␣ ␤3 is found on a subset of tumor blood vessels where it is associated with angiogenesis and malignant tumor growth. We designed an ␣ ␤3-targeted nanoparticle (NP) encapsulating the cytotoxic drug doxorubicin (Dox) for targeted drug delivery to the ␣ ␤3-expressing tumor vasculature. We observed real-time targeting of this NP to tumor vessels and noted selective apoptosis in regions of the ␣ ␤3-expressing tumor vasculature. In clinically relevant pancreatic and renal cell orthotopic models of spontaneous metastasis, targeted delivery of Dox produced an antimetastatic effect. In fact, ␣ ␤3-mediated delivery of this drug to the tumor vasculature resulted in a 15-fold increase in antimetastatic activity without producing drug-associated weight loss as observed with systemic administration of the free drug. These findings reveal that NP-based delivery of cytotoxic drugs to the ␣ ␤3-positive tumor vasculature represents an approach for treating metastatic disease.antiangiogenic ͉ intravital microscopy ͉ pancreatic cancer ͉ renal cell carcinoma ͉ liposome A ngiogenesis contributes to tumor malignancy and is linked to a wide variety of inflammatory and ischemic diseases. Integrin ␣v␤3, an internalization receptor for a number of viruses (1, 2), was shown to be preferentially expressed on the angiogenic endothelium in malignant or diseased tissues (3, 4). These characteristics of integrin ␣v␤3 make it an attractive targeting molecule for molecular imaging and delivery of therapeutics for cancer. Previous studies have shown that ␣v␤3-targeted nanoparticles (NPs) coupled to contrast agents can readily image the tumor vasculature revealing ''hot spots'' of angiogenesis within the tumor (5, 6). Therapeutic studies using the ␣v integrin-targeting peptide, RGD-4C, demonstrated that this peptide effectively targeted doxorubicin (Dox) to the tumor neovasculature and enhanced efficacy in human breast cancer xenografts in mice (7). In another study, an ␣v␤3-targeted NP delivering a suicide gene to angiogenic blood vessels was capable of producing an anticancer response (8). Although integrin ␣v␤3 is a marker of angiogenic endothelium, histological analysis of breast cancer biopsy tissue revealed that ␣v␤3 was a primary marker of blood vessels within the most malignant tumors (4). In fact, a strong correlation was established between the percent of ␣v␤3-positive vessels within the tumor and disease progression (9).Here, we report the design and characterization of an ␣v␤3-targeted NP capable of delivering various pharmacological agents to the ␣v␤3-expressing tumor vasculature. Evidence is provided that an ␣v␤3-targeted NP carrying the cytotoxic drug Dox is capable of controlling the metastatic behavior of pancreatic and renal cell cancer in mice. Importantly, targeted delivery of Dox to the tumor vasculature provided a 15-fold increase in the efficacy of the drug while producing few, if any, side effects. Results Design of NPs Targeted to Angiogenic Endothelium.A schematic representation of the targeted NP (RGD-NP) (Fig. ...

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In this study, we present data showing that Cdc42-dependent lumen formation by endothelial cells (ECs) in three-dimensional (3D) collagen matrices involves coordinated signaling by PKCϵ in conjunction with the Src-family kinases (SFKs) Src and Yes. Activated SFKs interact with Cdc42 in multiprotein signaling complexes that require PKCϵ during this process. Src and Yes are differentially expressed during EC lumen formation and siRNA suppression of either kinase, but not Fyn or Lyn, results in significant inhibition of EC lumen formation. Concurrent with Cdc42 activation, PKCϵ- and SFK-dependent signaling converge to activate p21-activated kinase (Pak)2 and Pak4 in steps that are also required for EC lumen formation. Pak2 and Pak4 further activate two Raf kinases, B-Raf and C-Raf, leading to ERK1 and ERK2 (ERK1/2) activation, which all seem to be necessary for EC lumen formation. This work reveals a multicomponent kinase signaling pathway downstream of integrin-matrix interactions and Cdc42 activation involving PKCϵ, Src, Yes, Pak2, Pak4, B-Raf, C-Raf and ERK1/2 to control EC lumen formation in 3D collagen matrices.

Non-small cell lung cancer patients carrying oncogenic EGFR mutations initially respond to EGFR-targeted therapy, but later elicit minimal response due to dose-limiting toxicities and acquired resistance. EGF816 is a novel, irreversible mutant-selective EGFR inhibitor that specifically targets EGFR-activating mutations arising de novo and upon resistance acquisition, while sparing wild-type (WT) EGFR. EGF816 potently inhibited the most common EGFR mutations L858R, Ex19del, and T790M in vitro, which translated into strong tumor regressions in vivo in several patient-derived xenograft models. Notably, EGF816 also demonstrated antitumor activity in an exon 20 insertion mutant model. At levels above efficacious doses, EGF816 treatment led to minimal inhibition of WT EGFR and was well tolerated. In single-dose studies, EGF816 provided sustained inhibition of EGFR phosphorylation, consistent with its ability for irreversible binding. Furthermore, combined treatment with EGF816 and INC280, a cMET inhibitor, resulted in durable antitumor efficacy in a xenograft model that initially developed resistance to firstgeneration EGFR inhibitors via cMET activation. Thus, we report the first preclinical characterization of EGF816 and provide the groundwork for its current evaluation in phase I/II clinical trials in patients harboring EGFR mutations, including T790M.

What determines the degree of cell-resistance or sensitivity to ionizing radiation is not yet known. As a corollary to the ability of ceramide to induce apoptosis, some questions arise as to whether malignant cells escape apoptosis because of their inability to mount a ceramide response to inducers of apoptosis. To shed more light on the molecular mechanisms of tumor cell response to radiation, we tested whether exposure to ionizing radiation (of 200-1000 cGy) is associated with changes in ceramide levels in A431 tumor epithelial cells and whether the ability of ceramide to induce apoptosis is inhibited by protein kinase C (PKC) activation. Our studies demonstrate an immediate decrease in cellular levels of ceramide in response to radiation, while sphingosine levels increase. Under the same conditions the cellular 1,2-diacylglycerol (DAG) levels decrease as well, being accompanied by the translocation of PKC alpha from the membrane to the cytoplasm. Elevation of membrane PKC levels by 12-O-tetradecanoylphorbol 13-acetate (TPA) treatment had no effect on cell survival after irradiation, while treatment with EGF during and after irradiation augmented cell survival. Moreover, monoclonal antibodies to the EGF receptor (EGFR) sensitize cells to radiation by facilitating radiation-induced apoptosis. It is thus plausible that in human Squamous carcinoma cells, radiation activates predominantly the EGFR to induce resistance, while both sphingomyelin and PKC signal transduction pathways are deactivated and demonstrate no significant role in the modulation of the sensitivity or the resistance of A431 cells to ionizing radiation.

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