== The graph shows average percentage of vascularized area of histological sections of tumors from each of the experimental groups. cells utilized for the experiments did not express VEGFR2 and because the treatment morpholino targeted mouse rather than human VEGFR2, it is likely that treatment morpholino was acting on the mouse PX-866 (Sonolisib) endothelial cells rather than directly on the tumor cells. Keywords:VEGFR2, angiogenesis inhibitors, morpholinos, option polyadenylation == 1. Introduction == Angiogenesis, or the growth of new blood vessels, plays a key role in tumor growth and invasion [1,2]. Because of this, the reduction of tumor angiogenesis is an important target in malignancy treatment. Multiple factors influencing blood vessel growth have been recognized, including vascular endothelial growth factor (VEGF), platelet derived growth factor (PDGF), fibroblast growth factor (FGF), neuropilin (NRP), and cadherin [3,4,5,6,7]. VEGF has been shown to play a particularly important role in tumor angiogenesis and is the target of several anti-cancer medications [8,9]. Targeting VEGF has been shown to be useful in treatment of several cancers, including colon cancer, ovarian cancer, and glioblastoma multiforme [10,11,12]. VEGF binds to several different receptors [13]. The primary angiogenic PX-866 (Sonolisib) receptor for VEGF is vascular endothelial growth factor receptor 2 (VEGFR2), which is also referred to as KDR [14,15]. Because of alternative polyadenylation, VEGFR2 is expressed in two different isoforms, membrane-bound VEGFR2 (mVEGFR2) and soluble VEGFR2 (sVEGFR2) [16,17]. mVEGFR2 is pro-angiogenic and consists of 7 extracellular domains, HNPCC2 a transmembrane domain, and tyrosine kinase domains [14,15]. sVEGFR2 is composed of only the extracellular portion of the molecule and does not contain the tyrosine kinase domains; therefore sVEGFR2 is anti-angiogenic and anti-lymphangiogenic [16,18]. Anti-sense technology has been used in the past to induce alternative splicing [19,20]. Our laboratory has previously developed and reported an antisense morpholino oligomer directed against the exon 13-intron 13 junction that shifts expression from mVEGFR2 to sVEGFR2 [18]. We previously showed that this morpholino reduces mVEGFR2 and increases sVEGFR2 at both an mRNA and protein level. Using this morpholino, we successfully reduced laser photocoagulation induced choroidal neovascularization with intravitreal injection, decreased corneal neovascularization with subconjunctival injection, and suppressed corneal graft rejection with subconjunctival injection [18]. As our morpholino was successful in treating ocular models of neovascularization, we hypothesized that the morpholino would successfully reduce tumor neovascularization and growth. == 2. Results and Discussion == == 2.1. In Vitro HCT 116 Cells Do Not Express VEGFR2 in Either Isoform == To ensure that the treatment morpholino was acting only on the effects of VEGFR2 on the vasculature, we used a xenograft model and verified that the human cancer cells that we used (HCT116) did not express VEGR2. RT-PCR showed thatin vitroHCT 116 cells did not express VEGFR2 in either of its isoforms, while HUVEC control did (Figure 1). This result was confirmed with real-time PCR (Figure 2). == Figure 1. == PCR was used to evaluatein vitroHCT 116 cells for VEGFR2 expression. This 1 1.2% agarose electrophoresis image shows no expression of mVEGFR2 and sVEGFR2 by HCT 116 cells, but positive expression of both by HUVEC controls. == Figure 2. == Real-time PCR also showed that thein vitroHCT 116 cells did not express VEGFR2 in either isoform. This confirmed the RT-PCR results presented inFigure 1. In this figure, the HCT116 does show some elevation, however the melting curve does not show a peak so this is a false positive result. == 2.2. sVEGFR2-Inducing Morpholino Decreases Proliferation of Endothelial Cells but Does Not Decrease Proliferation of HCT116 Cells in Vitro == To confirm that the sVEGFR2-inducing morpholino decreases endothelial cell proliferation but does not have direct effect on HCT116 cells,in vitrocell proliferation assays were performed. At a lower concentration of 4 micrograms/milliliter, neither the standard morpholino nor the sVEGFR2-inducing morpholino affected proliferation of both Human aortic endothelial cells (HAEC) and HCT116. At a higher concentration of 40 micrograms/milliliter, the sVEGFR-2 inducing morpholino decreased proliferation PX-866 (Sonolisib) of HAEC but the standard morpholino did not. However, at the higher concentration, both the standard morpholino and the sVEGFR2-inducing morpholino decreased HCT116 proliferation (p< 0.001) (Figure 3). As both the control and treatment morpholino exhibited this effect, it is most likely related to toxicity of the morpholino at a high concentration on the more fragile HCT 116 cells rather than changes of VEGFR2 expression. This toxicity is possible due to dendrimer formation [21]. These results suggest that the sVEGFR2-inductin morpholino has a direct effect on the endothelial cells but no direct effect on the HCT-116 cells. == Figure 3. == At concentrations of 4 g/mL, the control and treatment morpholino did not affect neither HAEC proliferation nor HCT 116 proliferation at both 24 and 48 h. At higher concentrations of 40 g/mL, the treatment morpholino decreased proliferation of HAEC but the control morpholino did PX-866 (Sonolisib) not..