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. ...

Herein, we report enhanced intravenous mouse lung transfection using novel cyclic-head-group analogs of usually open-head cationic transfection lipids. Design and synthesis of the new cyclic-head lipid N,N-di-n-tetradecyl-3,4-dihydroxy-pyrrolidinium chloride (lipid 1) and its higher alkyl-chain analogs (lipids 2-4) and relative in vitro and in vivo gene transfer efficacies of cyclic-head lipids 1-4 to their corresponding open-head analogs [lipid 5, namely N,N-di-n-tetradecyl-N,N-(2-hydroxyethyl)ammonium chloride and its higher alkyl-chain analogs, lipids 6-8] have been described. In stark contrast to comparable in vitro transfection efficacies of both the cyclic- and open-head lipids, lipids 1-4 with cyclic heads were found to be significantly more efficient (by 5- to 11-fold) in transfecting mouse lung than their corresponding open-head analogs (5-8) upon intravenous administration. The cyclic-head lipid 3 with di-stearyl hydrophobic tail was found to be the most promising for future applications.

Cancer remains the second leading cause of death after heart disease in the US. While metastasized cancers such as breast, prostate, and colon are incurable, before their distant spread, these diseases will have invaded the lymphatic system as a first step in their progression. Hence, proper evaluation of the disease state of the lymphatics which drain a tumor site is crucial to staging and the formation of a treatment plan. Current lymphatic imaging modalities with visible dyes and radionucleotide tracers offer limited sensitivity and poor resolution; however, newer tools using nanocarriers, quantum dots, and magnetic resonance imaging promise to vastly improve the staging of lymphatic spread without needless biopsies. Concurrent with the improvement of lymphatic imaging agents, has been the development of drug carriers that can localize chemotherapy to the lymphatic system, thus improving the treatment of localized disease while minimizing the exposure of healthy organs to cytotoxic drugs. This review will focus on the use of various nanoparticulate and polymeric systems that have been developed for imaging and drug delivery to the lymph system, how these new devices improve upon current technologies, and where further improvement is needed.

Kinases are known to regulate fundamental processes in cancer including tumor proliferation, metastasis, neovascularization, and chemoresistance. Accordingly, kinase inhibitors have been a major focus of drug development, and several kinase inhibitors are now approved for various cancer indications. Typically, kinase inhibitors are selected via high-throughput screening using catalytic kinase domains at low ATP concentration, and this process often yields ATP mimetics that lack specificity and/or function poorly in cells where ATP levels are high. Molecules targeting the allosteric site in the inactive kinase conformation (type II inhibitors) provide an alternative for developing selective inhibitors that are physiologically active. By applying a rational design approach using a constrained aminotriazole scaffold predicted to stabilize kinases in the inactive state, we generated a series of selective type II inhibitors of PDGFRβ and B-RAF, important targets for pericyte recruitment and endothelial cell survival, respectively. These molecules were designed in silico and screened for antivascular activity in both cell-based models and a Tg (fli1-EGFP) zebrafish embryogenesis model. Dual inhibition of PDGFRβ and B-RAF cellular signaling demonstrated synergistic antiangiogenic activity in both zebrafish and murine models of angiogenesis, and a combination of previously characterized PDGFRβ and RAF inhibitors validated the synergy. Our lead compound was selected as an orally active molecule with favorable pharmacokinetic properties which demonstrated target inhibition in vivo leading to suppression of murine orthotopic tumors in both the kidney and pancreas.R AF is an important convergent point downstream of FGFR and VEGFR2 signaling in endothelial cells and has previously been shown to play a critical role in endothelial cell survival during angiogenesis (1-3). PDGFRβ is a receptor tyrosine kinase that is essential for promoting proper pericyte function, which stabilizes blood vessels and enables vessel maturation (4-6). We rationalized that inhibition of both RAF and PDGFRβ would produce a potent antiangiogenic effect by targeting the two primary cell types involved in angiogenesis and vascular remodeling, endothelial cells and pericytes, respectively. As such, we designed compounds predicted to inhibit both RAF and PDGFRβ in a selective manner.The recent approval of imatinib (7, 8) (1) and sorafenib (9) (2), inhibitors which target PDGFRβ (10) and/or B-RAF (11, 12), has created much enthusiasm for small molecules that stabilize the inactive kinase conformation (13-15). These two molecules were cocrystallized with their respective targets, B-RAF (16) and Abl (17) kinase domains, and shown to interact in part with the allosteric site in the "DFG-out" conformation, referred to as type II inhibition. Based on the binding mode of sorafenib and imatinib, we synthesized an amino-triazole scaffold designed to target the allosteric site of both PDGFRβ and B-RAF using a combination of in silico screening and in vitro bioass...