Antiangiogenic Cancer Therapy Research Articles

Phase II trial of levocetirizine with capecitabine and bevacizumab to overcome the resistance of antiangiogenic therapies in refractory metastatic colorectal cancer.

763 Background: Despite clinical success of VEGF blockade in mCRC, resistance to anti-angiogenic drugs invariably develops. IL-8 and other cytokines have been implicated in resistance development to anti-angiogenic therapy. Levocetirizine is a third generation antihistamine with anti-inflammatory and IL-8 suppression properties. We conducted a phase II trial combining levocetirizine with capecitabine and bevacizumab to potentially overcome anti-angiogenic therapy resistance in patients with refractory mCRC. Methods: This was a single-center open-label prospective trial in refractory mCRC patients. Treatment consisted of oral capecitabine 850mg/m2 – 7 days on and 7 days off, IV bevacizumab 5 mg/kg every 14 days and oral levocetirizine 5 mg daily in 14 day cycles. The primary end point was PFS and secondary endpoints included ORR and tolerability. An exploratory endpoint included correlation of PFS with cytokine (IL-8 & IL-6) levels. A sample size of 36 evaluable patients could identify a median PFS of 3.4 months at a 0.05 significance level. To document cytokine changes related to levocetirizine treatment, patients were randomized to Arm A where levocetirizine was started 7 days after starting chemotherapy or to Arm B where levocetirizine was started 7 days prior to chemotherapy. For PFS determination both arms were combined for analysis. Cytokine levels were measured at baseline and with each cycle of chemotherapy (up to three cycles). Results: 43 patients were enrolled in the trial to have 36 evaluable patients. Arm A enrolled 20 patients and Arm B enrolled 23 patients. Of the patients evaluable for best response, 19 had SD and 12 had PD. Median PFS of all patients on the study was 3.4 months (ranging 0.9 to 10.6 months). Conclusions: Median PFS in the trial was comparable to and possibly better than other regimens used in the refractory setting (e.g., median PFS of 1.9 months for regorafenib). Cytokine analysis is in progress and these results and correlations with patient outcomes will be presented to assess the impact of cytokine blockade on mCRC treatment. Clinical trial information: NCT01722162.

Angiogenesis and Anti-angiogenic Therapies in Epithelial Ovarian Cancer

Ovarian cancer has a poor prognosis even after a complete resection and a platinum adjuvant chemotherapy because of its high rate of relapses. Clinical research has shown the role of angiogenesis in the development and progression of ovarian carcinoma. Several factors are involved, specially the VEGF. Bevacizumab is a humanized anti-VEGF antibody that was approved by the European Medicines Agency in first line for the treatments of advanced epithelial ovarian cancer, fallopian tube cancer and primary peritoneal cancer. It has to be combined with carboplatin and paclitaxel followed by maintenance therapy with bevacizumab alone. Bevacizumab has also been approved by EMA for the treatment of platinum-sensitive ovarian cancer recurrence in combination with carboplatin and gemcitabine. This literature review aims to provide updates about angiogenesis in ovarian cancer, pro-and anti-angiogenic factors that regulate angiogenesis, and lists new anti-angiogenic therapies in different phases of clinical development that aim to improve survival in patients with ovarian cancer. Keywords: Angiogenesis, anti-angiogenic therapies, bevacizumab, ovarian cancer, VEGF.

Delta-like ligand 4-targeted nanomedicine for antiangiogenic cancer therapy

Tumor angiogenesis is a multistep process involved with multiple molecular events in cancer microenvironment. Several molecular-targeted agents aiming to suppress tumor angiogenesis have been successfully translated into cancer clinic. However, new strategies are still urgently desired to be excavated to overcome the poor response and resistance in some antiangiogenic therapies. Recently, Delta-like ligand 4 (Dll4) is identified to be specifically over-expressed on tumor vascular endothelial cells (EC), and the Dll4-Notch pathway serves as a critical regulator in the development and maintenance of tumor angiogenesis. The intensively up-regulated phenotype of Dll4 on the membrane of tumor vascular EC implies that Dll4 may act as a targetable address for drug delivery system (DDS) to achieve targeted antiangiogenic cancer therapy. Here, a nano-DDS, GD16 peptide (H2N-GRCTNFHNFIYICFPD-CONH2, containing a disulfide bond between Cys3 and Cys13) conjugated nanoparticles loading paclitaxel (GD16-PTX-NP), which can specifically target the angiogenic marker Dll4, was fabricated for the investigation of antiangiogenic therapeutic efficacy in human head and neck cancer FaDu (Dll4-negative) xenograft in nude mice. The results demonstrate that GD16-PTX-NP achieved controlled drug release and exhibited favorable in vivo long-circulating feature. GD16-PTX-NP exerted enhanced antiangiogenic activity in the inhibition of human umbilical vein endothelial cell (HUVEC) viability, motility, migration, and tube formation, and in the Matrigel plug model as well, which can be definitely ascribed to the active internalization mediated by the interaction of GD16 and the over-expressed Dll4 on EC. GD16-PTX-NP showed accurate in vivo tumor neovasculature targeting property in FaDu tumor, where the paclitaxel was specifically delivered into the tumor vascular EC, leading to significant apoptosis of tumor vascular EC and necrosis of tumor tissues. The antiangiogenic activity of GD16-PTX-NP significantly contributed to its in vivo anticancer efficacy in Fadu tumor; moreover, no overt toxicity to the mice was observed. Our research firstly presents the potency and significance of a Dll4-targeted nanomedicine in antiangiogenic cancer therapy.

Raddeanin A, a triterpenoid saponin isolated from Anemone raddeana, suppresses the angiogenesis and growth of human colorectal tumor by inhibiting VEGFR2 signaling

Raddeanin A (RA) is an active triterpenoid saponin from a traditional Chinese medicinal herb, Anemone raddeana Regel. It was previously reported that RA possessed attractive antitumor activity through inhibiting proliferation and inducing apoptosis of multiple cancer cells. However, whether RA can inhibit angiogenesis, an essential step in cancer development, remains unknown. In this study, we found that RA could significantly inhibit human umbilical vein endothelial cell (HUVEC) proliferation, motility, migration, and tube formation. RA also dramatically reduced angiogenesis in chick embryo chorioallantoic membrane (CAM), restrained the trunk angiogenesis in zebrafish, and suppressed angiogenesis and growth of human HCT-15 colorectal cancer xenograft in mice. Western blot assay showed that RA suppressed VEGF-induced phosphorylation of VEGFR2 and its downstream protein kinases including PLCγ1, JAK2, FAK, Src, and Akt. Molecular docking simulation indicated that RA formed hydrogen bonds and hydrophobic interactions within the ATP binding pocket of VEGFR2 kinase domain. Our study firstly provides the evidence that RA has high antiangiogenic potency and explores its molecular basis, demonstrating that RA is a potential agent or lead candidate for antiangiogenic cancer therapy.

Biglycan up-regulated vascular endothelial growth factor (VEGF) expression and promoted angiogenesis in colon cancer.

Biglycan is an important component of the extracellular matrix, which belongs to the small leucine-rich proteoglycan family. Recent studies have shown that biglycan expression is elevated in many tumor tissues and implies poor prognosis, such as colon cancer. However, the molecular mechanism of biglycan in colon cancer has not been investigated. The present study aimed to investigate the effects of biglycan on vascular endothelial growth factor (VEGF) expression in colon cancer cells and on tumor angiogenesis in vivo. Biglycan overexpression vectors were constructed, and the stable biglycan overexpression in human colon cancer cell lines (HCT116 cells) was established by G418 screening. The stable cell clones were subsequently used to initiate tumor xenografts in nude mice. Our results showed that biglycan overexpression notably up-regulated the levels of VEGF in colon cancer cells, which was further confirmed by immunohistochemistry analysis in the xenograft colon tumors. Moreover, high levels of biglycan promoted angiogenesis and colon tumor growth, as evidenced by the increased cell viability, colon tumor size, and weight, as well as the CD34 expression. Additionally, we found that the extracellular signal-regulated kinase (ERK) signaling pathway was activated by biglycan in colon cancer cells. The ERK inhibitor PD98059 dramatically reversed the increased expression of VEGF induced by biglycan. Taken together, our results indicated that biglycan up-regulated VEGF expression in colon cancer cells and promoted tumor angiogenesis. Biglycan-mediated VEGF regulation may correlate with the activation of the ERK signaling pathway. Therefore, biglycan may be a promising target for anti-angiogenic therapy for cancer.

Novel analogs of antitumor agent calixarene 0118: Synthesis, cytotoxicity, click labeling with 2-[(18)F]fluoroethylazide, and in vivo evaluation.

Calixarene 0118 is a potent anti-angiogenic agent that effectively inhibited tumor growth in preclinical studies, and is currently being evaluated in a phase I clinical trial. We have designed two close mimetics of calixarene 0118 containing a terminal alkynyl-functional group, and developed an optimized semi-automated procedure for radiolabeling with 2-[(18)F]fluoroethylazide using click chemistry. Following semi-preparative HPLC purification and formulation, the lower-rim modified analog [(18)F]6 and the equatorially labeled [(18)F]13 were obtained in >97% radiochemical purity and overall decay-corrected isolated radiochemical yields of 18.7±2.7% (n=4) and 10.2±5.0% (n=4), respectively, in a total synthesis time of about 2h. Preliminary invivo studies in nude mice bearing human tumor xenografts revealed highest accumulation of both tracers in the liver, followed by spleen, kidney, lung and bone, with no substantial uptake in the tumor. Still, these first-in-class radiotracers are a valuable tool for pharmacokinetic profiling and improvement of calixarene-based anti-angiogenic therapeutics in the future, as similar radiolabeling strategies may be applied to other compounds in the calixarene series. The cold reference compounds of the radiotracers were characterized in terms of cytotoxicity and anti-proliferative effects on HUVEC cells and on MA148 human ovarian carcinoma cells, along with the respective precursors, a small series of 0118 analogs modified with short-chain linear alkyl substituents, and a PEG3-spaced calixarene dimer. While all of the new analogs proved at least equipotent to parent 0118, some of them inhibited HUVEC and MA148 cell growth almost 4- and 10-fold more effectively, rendering these analogs promising candidates for further evaluation in anti-angiogenic cancer therapy.

Anti-angiogenic therapy versus dose-dense paclitaxel therapy for frontline treatment of epithelial ovarian cancer: review of phase III randomized clinical trials.

The investigation of anti-angiogenic agents and dose-dense paclitaxel therapy in epithelial ovarian cancer is an active area of research. To date several phase III trials have shown both approaches to be effective strategies for the frontline treatment of ovarian cancer over standard every 21 day chemotherapy alone. However, most of the improvement is seen only in progression-free survival, with added toxicity (e.g., hypertension, diarrhea, sensory neuropathy, fatigue). Subset analyses based on clinical predictors (e.g., residual disease) have been able to identify patients more likely to benefit from anti-angiogenic agents. And more recently, molecular profiling of tumor genetics has shown similar promising results. Ongoing research will help enhance our ability to match patients to therapeutic strategies most likely to optimize outcomes and minimize risk.

Ramucirumab: a promising development in advanced non-small cell lung cancer

The VEGF pathway is a critical target for anti-angiogenic therapy in advanced non-small cell lung cancer (NSCLC). Bevacizumab, a monoclonal antibody targeting VEGF-A, is the only anti-angiogenic agent approved for first-line use in combination with platinum-based chemotherapy. Ramucirumab is another monoclonal antibody that specifically binds to the extracellular domain of the main angiogenic receptor VEGFR-2 on endothelial cells. Clinical development of ramucirumab demonstrated promising activity and a tolerable safety profile in combination with first-line chemotherapy in advanced NSCLC. Recently, the REVEL Phase III trial, including both squamous and nonsquamous carcinoma, demonstrated that the addition of ramucirumab to standard second-line docetaxel provided a significant improvement of overall survival, providing an evidence for VEGFR-targeted antiangiogenic therapy in advanced NSCLC.

Anti-angiogenic therapies for advanced esophago-gastric cancer.

Neo-vascularization is a vital process for tumor growth and development which involves the interaction between tumor cells and stromal endothelial cells through several growth factors and membranous receptors which ultimately activate pro-angiogenic intracellular signaling pathways. Inhibition of angiogenesis has become a standard treatment option for several tumor types including colorectal cancer, glioblastoma and ovarian cancer. In gastric cancer, the therapeutic role of anti-angiogenic agents is more controversial. Bevacizumab and ramucirumab, two monoclonal antibodies, which target vascular endothelial growth factor-A and vascular endothelial growth factor receptor-2, respectively, have been demonstrated antitumor activity in patients with tumors of the stomach or esophagogastric junction. However, especially for bevacizumab, this antitumor activity has not consistently translated into a survival advantage over standard treatment in randomized trials. In this article, we provide an overview of the role of angiogenesis in gastric cancer and discuss the results of clinical trials that investigated safety and effectiveness of antiangiogenic therapies in this disease. A review of the literature has been done using PubMed, ClinicalTrials.gov website and the ASCO Annual Meeting Library.

Highlights of This Issue

Trop-2 is highly expressed in diverse epithelial cancers with limited presence on normal tissues. Here, Rossi and colleagues report redirected T-cell therapy targeting Trop-2 on solid tumors with a trivalent bispecific antibody (bsAb). Studies with human blood and animal models showed that interferon-α enhanced T-cell mediated antitumor activity significantly, without causing increased cytokine production that is often associated with adverse side effects. Additionally, this group discovered that following association of T cells with target cells, Trop-2, and possibly other tumor cell proteins, was translocated to the cell surface of T cells. This target/T-cell phenomenon mediated by bsAb warrants further investigation.MAPK reactivation through BRAF spliced variants, NRAS mutation, and RTK activation is the major resistant mechanism to BRAF inhibition in melanoma. In this study, Yadav and colleagues studied in vivo and in vitro melanoma models of acquired resistance to vemurafenib, and described that reactivation of MAPK and overexpression of cyclin D1 were common features across the resistant models. Treatment with LY2835219, a CDK4/6 selective inhibitor, was sufficient to induce growth regression in vemurafenib-resistant tumors and enhanced apoptosis in vemurafenib-resistant cells, suggesting that targeting cyclin-D1/CDK4 signaling by LY2835219 could be an effective strategy to overcome MAPK-mediated resistance to BRAF inhibitors.Endoglin has emerged as an attractive target for antiangiogenic therapy in various cancers. Only a few studies explored the effect of targeting tumor cell–specific endoglin. Pal and colleagues have analyzed the effects of targeting tumor cell–specific endoglin in pancreatic cancer. Their results indicate that endoglin-targeted antiangiogenic therapy in pancreatic cancer may offer an additional advantage by targeting the tumor cells as well. Moreover, inhibition of endoglin also contributed to drug sensitivity, making it ideal for combination therapies in case of chemotherapy-resistant tumors. Overall, their data suggests endoglin-targeted therapy could be a double-speared approach for pancreatic cancer treatment.Lymphangiogenesis in tumors is an integral step in the metastatic spread of cancer cells and there is a need to identify novel antilymphangiogenic agents. Astin and colleagues used a zebrafish-based chemical screen to identify compounds that have antilymphatic activity in both zebrafish and mouse models of lymphangiogenesis. One compound, kaempferol, a natural product found in plants, was shown to inhibit VEGFR signaling and was able to reduce the density of tumoral lymphatics and lymph node metastases in a breast cancer xenograft model. These findings reveal that zebrafish are a viable platform for the identification and development of mammalian antilymphatic compounds.

Abstract 4946: Developing anti-angiogenic therapies for human hepatocellular cancer (HCC)- studies of suntinib in the woodchuck model of hepatitis B related HCC

Abstract Introduction: Better animal models that recapitulate the liver milieu of human HCC are needed. The eastern woodchuck is an established model of human hepatitis B viral infection and spontaneously develops HCC in the context of chronic woodchuck hepatitis viral infection (WHV). The translational relevance of this model for developing anti-angiogenic therapies was evaluated using sunitinib (S), a potent oral, anti-angiogenic agent. Methods: Woodchucks were bred and inoculated at birth with titered infectious WHV pools obtained from chronic WHV carriers. By 12 months of age, the rate of chronic WHV infection was >60%. Carriers were followed by USG, upon developing HCC, 12 animals were randomized 1:1 to S or placebo (P) given once orally daily for 30 days. From a single treatment S PK study at 4 dose levels, n=3/group, simulations showed 12mg/kg daily was expected to be optimal for achieving steady state serum concentrations between 50- 100 ng/ml in woodchucks. Tumor size and blood flow were assessed using dynamic contrast enhanced magnetic resonance imaging (DCE-MRI) before treatment and on day 28 using standardized protocols. At study completion or when animals were humanely euthanized, tumors and any other small nodules were fixed overnight in 10% buffered formalin. After standard processing and embedding in paraffin, 4 μm sections were prepared, deparaffinized, stained with hematoxylin-eosin (H&E), studied with a Zeiss Axio Imager A1 microscope by a pathologist blinded to the treatment arm. Morphometric study of areas of necrosis were compared to the size of the tumor sections by counting view fields at medium objective magnification, and differences in percentages between the groups were compared by the Excel student's two tailed, two-sample unequal variance t-test. Results: The median age was 30 months. Four animals died during the course of the study (1P, 3 S) and were replaced. Median therapy duration was 28 days. Morphologically, portal hepatitis and pre-neoplastic lesions (foci of altered hepatocytes [FAH]) and larger areas of altered hepatocytes (AAH) were seen in all livers. Areas of tumor necrosis of varying size (20-100%) adjacent to terminal hepatic venules seen in both high grade and in rare, low grade tumor sections of S treated woodchucks were rare in P animals. The difference was highly significant (p= 6.0 E-13) between the two groups. By DCE-MRI, median tumor volume change was + 17% and -13% and necrotic tumor volume change was +22% and +190% in P and S treated animals respectively. However all MRI parameters (k trans, AUC90, median tumor volume) were not statistically significantly different between the groups. Conclusions: Angiogenic response across different stages of hepatocarcinogenesis can be studied in woodchucks. Histological necrosis in S treated woodchucks without significant DCE-MRI change and the toxicities seen with S have translational significance to human HCC. Citation Format: Alexander Pomakov, Ilia Toshkov, Sandra Buitrago, Leslie Curtin, Donald Trump, Candace Johnson, Edward Ashton, Bud Tennant, Renuka Iyer. Developing anti-angiogenic therapies for human hepatocellular cancer (HCC)- studies of suntinib in the woodchuck model of hepatitis B related HCC. [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 4946. doi:10.1158/1538-7445.AM2014-4946

Abstract 2749: SRPK1 inhibition and modulation of VEGF alternative splicing as a potential therapeutic strategy in prostate cancer

Abstract Angiogenesis is required for tumor growth and is induced principally by VEGF-A. VEGF-A pre-mRNA is alternatively spliced at the terminal exon to produce two families of isoforms, pro- and anti-angiogenic, only the former of which is upregulated in prostate cancer. In renal epithelial cells and colon cancer cells, the choice of VEGF splice isoforms is controlled by the splicing factor SRSF1, phosphorylated by SRPK1. Immunohistochemistry staining of human samples revealed a significant increase in SRPK1 expression both in prostate intra-epithelial neoplasia lesions as well as malignant adenocarcinoma compared to benign prostate tissue. We therefore tested the hypothesis that the selective upregulation of pro-angiogenic VEGF in prostate cancer may be under control of SRPK1 activity. SRPK1 levels were up-regulated in several prostate cancer cell lines in comparison with normal prostate epithelial cells. A switch in the expression of VEGF165 towards the anti-angiogenic isoform, VEGF165b, was seen in PC-3 cells with SRPK1 knock-down (KD). PC-3 -SRPK1 KD cells resulted in tumors that grew more slowly in xenografts, with decreased microvessel density. No effect was seen as a result of SRPK1 KD on growth, proliferation, migration and invasion capabilities of PC-3 cells in vitro. Moreover, VEGF over-expression from a splicing-insensitive construct in PC-3/SRPK1 KD cells rescued tumor growth. Small molecule inhibitors of SRPK1 are able to switch splicing towards the anti-angiogenic isoform, VEGF165b in PC3 cells in vitro and decrease tumor growth when administered intraperitoneally in vivo in a mouse model of orthotopic prostate cancer. Our study suggests that modulation of SRPK1 and subsequent inhibition of tumor angiogenesis by regulation of VEGF splicing can alter prostate tumor growth and supports further studies into the use of SRPK1 inhibition as a potential anti-angiogenic therapy in prostate cancer. Note: This abstract was not presented at the meeting. Citation Format: Athina Mavrou, Dave Bates, Sebastian Oltean. SRPK1 inhibition and modulation of VEGF alternative splicing as a potential therapeutic strategy in prostate cancer. [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 2749. doi:10.1158/1538-7445.AM2014-2749

Dual receptor-specific peptides modified liposomes as VEGF siRNA vector for tumor-targeting therapy.

Tumor angiogenesis involves multiple signaling pathways that provide potential therapeutic targets to inhibit tumor growth and metastasis. Regarding the significant role of vascular endothelial growth factor (VEGF) in angiogenesis and tumor progression, VEGF sequence-specific small interfering RNA (siRNA) for anti-angiogenic tumor therapy are under development. In the present study, dual-modified liposomes (At-Lp) was designed by attaching two receptorspecific peptides, Angiopep and tLyP-1, which specifically targeting low-density lipoprotein receptor (LRP) for brain tumor targeting and neuropilin-1 receptor (NRP-1) for tumor penetration, respectively. Gene transfection and silencing, and antitumor effect of the At-Lp loaded with VEGF siRNA were evaluated in vitro and in orthotopic xenograft models of U87 MG tumor. The At-Lp significantly enhanced cellular uptake (2-fold) and down-regulated expression of VEGF in U87 MG glioblastoma cells compared with non-modified and single-modified liposomes. The internalization of the At-Lp into tumor cells was taken via the enhanced permeability and retention effect and receptor-mediated endocytosis, followed by an effective endosomal escape of loaded siRNA into the cytoplasm. The At-Lp showed great superiority in inhibition of tumor growth, anti-angiogenesis, expression of VEGF and apoptosis effect after in vivo application against nude mice bearing U87 MG glioblastoma without activation of system-associated toxicity and the innate immune response. These results demonstrated that the combination of two receptor-specific peptides-mediated liposomes presented a promising platform for effective targeting delivery of siRNA for cancer anti-angiogenic therapy.

Ageing-related responses to antiangiogenic effects of sunitinib in atherosclerosis-prone mice

Antiangiogenic therapies in cancer exert their effects in the context of age-related comorbidities, which affect the entirety of the vascular system. Among those conditions, the impact of atherosclerosis is especially prevalent, but poorly understood, and not reflected in mouse models routinely used for testing antiangiogenic therapeutics. Our earlier work suggested that these obstacles can be overcome with the use of atherosclerosis-prone ApoE−/− mice harbouring syngeneic transplantable Lewis Lung Carcinoma (LLC). Here we report that, sunitinib, the clinically approved, antiangiogenic inhibitor impedes global tumor growth to a greater extent in aged then in young mice. This activity was coupled with changes in the tumor microenvironment, which in aged mice was characterized by pronounced hypoxia, reduction in microvascular density (MVD) and lower pericyte coverage, relative to young controls. We also detected soluble VEGR2 in plasma of sunitinib treated mice. Interestingly, sunitinib modulated tumor infiltration with bone marrow-derived cells (CD45+), recruitment of M2-like macrophages (CD163+) and activation of inflammatory pathways (phospho-STAT3) in a manner that was age-dependent. We suggest that age and atherosclerosis may alter the effects of sunitinib on the tumor microenvironment, and that these considerations may also apply more broadly to other forms of antiangiogenic treatment in cancer.

COX-2 inhibition potentiates antiangiogenic cancer therapy and prevents metastasis in preclinical models.

Antiangiogenic agents that block vascular endothelial growth factor (VEGF) signaling are important components of current cancer treatment modalities but are limited by alternative ill-defined angiogenesis mechanisms that allow persistent tumor vascularization in the face of continued VEGF pathway blockade. We identified prostaglandin E2 (PGE2) as a soluble tumor-derived angiogenic factor associated with VEGF-independent angiogenesis. PGE2 production in preclinical breast and colon cancer models was tightly controlled by cyclooxygenase-2 (COX-2) expression, and COX-2 inhibition augmented VEGF pathway blockade to suppress angiogenesis and tumor growth, prevent metastasis, and increase overall survival. These results demonstrate the importance of the COX-2/PGE2 pathway in mediating resistance to VEGF pathway blockade and could aid in the rapid development of more efficacious anticancer therapies.

Tie1, The 0rphan Receptor No Longer in the Shadows

Angiogenesis, the formation of new blood vessels from pre-existing ones, occurs during physiological conditions such as wound healing, pregnancy and the menstrual cycle. It is also a fundamental process in pathological conditions such as tumor development, ocular disease, diabetes, atherosclerosis and arthritis. Angiogenesis as a therapeutic target (especially Vascular Endothelial Growth Factor (VEGF) inhibitors) has been heavily pursued in numerous cancer settings with promising results yet fallen short of its expectations. The discovery of the endothelial cell specific Angiopoietin/Tie axis and its role in normal and pathological angiogenesis led to the development of second-generation anti-angiogenic agents. Most of the effort has been to target the pro-angiogenic factor Ang-2 and its receptor Tie2. The present research highlight focuses on a study by D’Amico et al., “Tie1 deletion inhibits tumor growth and improves angiopoietin antagonist therapy” published in the Journal of Clinical Investigation, that demonstrates for the first time the therapeutic benefit of targeting the orphan receptor, Tie1, involved in the complex biological axis of the Angiopoietin/Tie2 system in angiogenesis. This study shows tremendous implications for future considerations in anti-angiogenic therapy for cancer and other angiogenesis related diseases.

Erratum to: Anti-angiogenic therapy for cancer: current progress, unresolved questions and future directions

The online version of the original article can be found under doi:10.1007/s10456-014-9420-y.

OLC1 is overexpressed in breast cancer and its expression correlates with poor patient survival.

The overexpressed in lung cancer 1 (OLC1) has been demonstrated to be associated with numerous biological and pathological processes. However, the role of OLC1 in breast cancer has not been thoroughly elucidated. The purpose of this study was to assess OLC1 expression and to explore its contribution to the breast cancer. Real-time quantitative reverse transcription polymerase chain reaction (qRT-PCR) was conducted to detect OLC1 messenger RNA (mRNA) expression in 45 pairs of fresh-frozen breast cancer tissues and corresponding noncancerous tissues. Immunohistochemistry was performed to detect the expression of OLC1 in 145 breast cancer tissues. The relationship between the expression of OLC1 and clinicopathological characteristics and prognosis was statistically analyzed. We found that the expression levels of OLC1 mRNA and protein in breast cancer tissues were significantly higher than those in adjacent noncancerous tissues (P < 0.001). In addition, OLC1 expression was significantly correlated with tumor size (P = 0.034), grade (P = 0.015), stage (P < 0.001), and lymph node metastases (P = 0.028). Kaplan-Meier survival analysis showed that a high expression level of OLC1 resulted in a significantly poor prognosis of breast cancer patients. Further, Cox multivariate analysis indicated that OLC1 expression level was an independent prognostic factor for the overall survival rate of breast cancer patients. These findings provide evidence that a high expression level of OLC1 serves as a biomarker for poor prognosis for breast cancer. Thus, we speculate that OLC1 may be a potential target of antiangiogenic therapy for breast cancer.

Direct cytosolic siRNA delivery by reconstituted high density lipoprotein for target-specific therapy of tumor angiogenesis

We described here the mechanisms by which small interfering RNA (siRNA) molecules incorporated in reconstituted high density lipoprotein (rHDL) were efficiently transferred into the cytoplasm of cells to perform target-specific therapy of tumor angiogenesis. Using fluorescent-tagged apolipoprotein A-I (apoA-I) and cholesterol-conjugated siRNA (Chol-siRNA), it was confirmed with FACS and confocal microscopic measurements that Chol-siRNA-loaded rHDL nanoparticles (rHDL/Chol-siRNA complexes) were successfully established and apoA-I certainly was attached to the surface of Chol-siRNA-loaded lipoplexes (Lipos/Chol-siRNA complexes). Stably assembled rHDL/Chol-siRNA complexes demonstrated proper nanosize, quasi-spherical shape and improved nuclease protection over naked Chol-siRNA. It was also interesting to note that rHDL provided a highly effective approach to transfer Chol-siRNA across the membrane directly into the cytoplasm via the scavenger receptor BI (SR-BI)-mediated non-endocytotic mechanism, thereby bypassing endo-lysosomal trapping. We also showed clear evidence that the in vitro implementation of rHDL for Chol-siRNA-VEGF (Chol-siRNA targeting vascular endothelial growth factor gene) delivery markedly promoted RNA interference (RNAi)-mediated degradation of VEGF mRNA, resulting in down-regulation of secreted VEGF protein. In vivo fluorescence imaging indicated that near-infrared (NIR) dye Cy5 labeled Chol-siRNA-loaded rHDL nanoparticles (rHDL/Cy5-Chol-siRNA complexes) displayed long circulation time, SR-BI positive tumor-selective targeting, and efficient cytosolic delivery capabilities. Furthermore, intravenous administration of Chol-siRNA-VEGF-loaded rHDL nanoparticles (rHDL/Chol-siRNA-VEGF complexes) significantly enhanced anti-tumor efficacy against breast cancer, decreased VEGF expression level, and inhibited formation of intratumoral microvessels at the tumor tissue. It was concluded that rHDL possessed therapeutic potential and versatility in mediating Chol-siRNA-VEGF direct cytosolic delivery for target-specific anti-angiogenic therapy in breast cancer.

Prostate-specific membrane antigen (PSMA) immunoexpression in the neovasculature of colorectal carcinoma in Egyptian patients

In Egypt colorectal carcinoma (CRC) is the most common type of malignancy of the digestive system. Selectively inhibiting neoangiogenesis by targeting tumor-associated blood vessels is an important therapeutic strategy. Prostate specific membrane antigen (PSMA) is expressed in the tumor-associated neovasculature of most solid cancers making it an interesting therapeutic target. We thought to study the expression of PSMA in a series of CRCs in order to test for its possible use as a target for antiangiogenic cancer therapy in Egyptian patients. One hundred CRC cases were retrieved. Representative sections from each tumor were subjected to immunohistochemistry using PSMA antibodies and CD31 antibodies as reference marker. Accordingly vascular endothelial cell immunoreactivity was semiquantitatively scored. PSMA immunostaining was positive in the neovasculature of 75% of tumors. A statistically significant relation was found between PSMA immunostaining and distant metastasis as well as vascular invasion. The present findings strengthen the evidence on the potential usefulness of PSMA as a therapeutic vascular target. This study is the first to demonstrate a positive relation between PSMA expression in CRC and distant metastasis as well vascular invasion, suggesting that PSMA may play a significant role in vascular invasion and subsequent metastasis.