Dual targeting of vascular endothelial growth factor and bone morphogenetic protein‐9/10 impairs tumor growth through inhibition of angiogenesis

Clinical development of anti‐angiogenic agents has been a major landmark in cancer therapy for several types of cancers. Signals mediated by both vascular endothelial growth factor (VEGF) and bone morphogenetic protein (BMP)‐9 and 10 have been implicated in tumor angiogenesis. However, previous studies have shown that targeting the individual signals was not sufficiently effective in retarding tumor growth in certain preclinical and clinical conditions. In the present study, we developed a novel decoy chimeric receptor that traps both VEGF and BMP‐9/10. Single targeting of either VEGF or BMP‐9/10 signals significantly reduced the formation of tumor vessels in a mouse xenograft model of human pancreatic cancer; however, it did not show significant therapeutic effects on tumor growth. In contrast, dual targeting of the angiogenic signals resulted in more significant inhibition of tumor angiogenesis, leading to delay of tumor growth. Our findings suggest that simultaneous blockade of VEGF and BMP‐9/10 signals is a promising therapeutic strategy for the cancers that are resistant to anti‐VEGF and BMP‐9/10 therapies.     

Anti‐VEGF antibody enhances the antitumor effect of CD40

As its central immunomodulatory effects, CD40 induces interleukin (IL)‐12‐dependent antitumor immune responses; as its local protumor effects, CD40 induces the expression of vascular endothelial growth factor (VEGF) that promotes tumor angiogenesis and growth. Therefore, using a previously established tumor model in mouse, we examined if the antitumor functions of CD40 are self‐limited by VEGF induction. We observed that as the tumor mass grew during day 6 to day 18, VEGF expression in the tumor peaked with concomitant decrease in expressions of CD40 and IL‐12 but not of IL‐10. Among the angiogenic factors, VEGF‐B, VEGFR‐1, VEGFR‐2, angiopoietin‐1 and Tie2 expressions decreased, whereas the expressions of angiopoietin‐2 and angiopoietin‐3 increased with tumor growth. As significant changes in the expressions of these factors were observed on day 6, we treated the tumor‐bearing mice with the agonistic anti‐CD40 antibody or neutralizing anti‐VEGF antibody—alone or in combination—from the fifth day after the injection of tumor cells. The anti‐VEGF antibody significantly enhanced the antitumor effects of the anti‐CD40 antibody, as observed through increased survival of the mice, accompanied by reduced angiogenesis and angiopoietin‐2 expression but higher T‐cell proliferation in response to tumor antigens, increased interferon‐γ production and tumor cell cytotoxicity and higher levels of tumor antigen‐specific serum IgM, IgG1 and IgG2a, indicating B‐cell activation. Thus, our data show for the first time that the combined treatment with an agonistic anti‐CD40 antibody and a neutralizing anti‐VEGF antibody, which increases antitumor immune response or reduces local angiogenesis, respectively, is a novel antitumor strategy.     

Anti‐VEGF antibody therapy induces tumor hypoxia and stanniocalcin 2 expression and potentiates growth of human colon cancer xenografts

Tumor angiogenesis plays a critical role in colorectal cancer progression. Recent randomized clinical trials have revealed the additive effect of bevacizumab, a humanized monoclonal antibody against vascular endothelial growth factor (VEGF)‐A, to conventional chemotherapy in the improved survival of patients with metastatic colorectal cancer. However, a number of preclinical reports indicate the development of resistance to anti‐angiogenic therapy. In this study, we addressed the effects of anti‐VEGF antibodies on the growth and malignant behavior of colorectal cancer cells. TK‐4, a solid tumor strain derived from a colon cancer patient, was subcutaneously or orthotopically implanted into nude mice. Short‐term administration of anti‐VEGF antibodies inhibited the growth of cecal tumors at day 14 by suppressing mitosis, but prolonged treatment resulted in the recovery of cellular proliferation and suppression of apoptosis at day 35. Intratumoral hypoxia induced by anti‐VEGF antibody treatment resulted in activation of hypoxia inducible factor‐1α protein and an increased number of aldehyde dehydrogenase 1‐positive tumor cells. In microarray analysis, stanniocalcin 2 (STC2) was the most highly upregulated gene in anti‐VEGF antibody‐treated tumors. In vitro analyses showed that the growth and migration of SW480 colon cancer cells under hypoxic conditions were significantly inhibited by knockdown of STC2. In vivo serial transplantation of TK‐4 revealed that long‐term administration of anti‐VEGF antibodies increased the tumorigenicity of colon cancers and accelerated tumor growth when transplanted into secondary recipient mice. Our data provide a potential molecular explanation for the limited clinical effectiveness of anti‐VEGF antibodies.     

Lowering bone mineral affinity of bisphosphonates as a therapeutic strategy to optimize skeletal tumor growth inhibition in vivo

Bisphosphonates bind avidly to bone mineral and are potent inhibitors of osteoclast-mediated bone destruction. They also exhibit antitumor activity in vitro. Here, we used a mouse model of human breast cancer bone metastasis to examine the effects of risedronate and NE-10790, a phosphonocarboxylate analogue of the bisphosphonate risedronate, on osteolysis and tumor growth. Osteolysis was measured by radiography and histomorphometry. Tumor burden was measured by fluorescence imaging and histomorphometry. NE-10790 had a 70-fold lower bone mineral affinity compared with risedronate. It was 7-fold and 8,800-fold less potent than risedronate at reducing, respectively, breast cancer cell viability in vitro and bone loss in ovariectomized animals. We next showed that risedronate given at a low dosage in animals bearing human B02-GFP breast tumors reduced osteolysis by inhibiting bone resorption, whereas therapy with higher doses also inhibited skeletal tumor burden. Conversely, therapy with NE-10790 substantially reduced skeletal tumor growth at a dosage that did not inhibit osteolysis, a higher dosage being able to also reduce bone destruction. The in vivo antitumor activity of NE-10790 was restricted to bone because it did not inhibit the growth of subcutaneous B02-GFP tumor xenografts nor the formation of B16-F10 melanoma lung metastases. Moreover, NE-10790, in combination with risedronate, reduced both osteolysis and skeletal tumor burden, whereas NE-10790 or risedronate alone only decreased either tumor burden or osteolysis, respectively. In conclusion, our study shows that decreasing the bone mineral affinity of bisphosphonates is an effective therapeutic strategy to inhibit skeletal tumor growth in vivo.     

Bevacizumab Inhibits Breast Cancer-Induced Osteolysis, Surrounding Soft Tissue Metastasis, and Angiogenesis in Rats as Visualized by VCT and MRI

The aim of this study was to evaluate the effect of an antiangiogenic treatment with the vascular endothelial growth factor antibody bevacizumab in an experimental model of breast cancer bone metastasis and to monitor osteolysis, soft tissue tumor, and angiogenesis in bone metastasis noninvasively by volumetric computed tomography (VCT) and magnetic resonance imaging (MRI). After inoculation of MDA-MB-231 human breast cancer cells into nude rats, bone metastasis was monitored with contrast-enhanced VCT and MRI from day 30 to day 70 after tumor cell inoculation, respectively. Thereby, animals of the treatment group (10 mg/kg bevacizumab IV weekly, n = 15) were compared with sham-treated animals (n = 17). Treatment with bevacizumab resulted in a significant difference versus control in osteolytic as well as soft tissue lesion sizes (days 50 to 70 and 40 to 70 after tumor cell inoculation, respectively; P < .05). This observation was paralleled with significantly reduced vascularization in the treatment group as shown by reduced increase in relative signal intensity in dynamic contrast-enhanced MRI from days 40 to 70 (P < .05). Contrast-enhanced VCT and histology confirmed decreased angiogenesis as well as new bone formation after application of bevacizumab. In conclusion, bevacizumab significantly inhibited osteolysis, surrounding soft tissue tumor growth, and angiogenesis in an experimental model of breast cancer bone metastasis as visualized by VCT and MRI.     

Dual function of ERRα in breast cancer and bone metastasis formation: implication of VEGF and osteoprotegerin

Bone metastasis is a complication occurring in up to 70% of advanced breast cancer patients. The estrogen receptor-related receptor alpha (ERRα) has been implicated in breast cancer and bone development, prompting us to examine whether ERRα may function in promoting the osteolytic growth of breast cancer cells in bone. In a mouse xenograft model of metastatic human breast cancer, overexpression of wild-type ERRα reduced metastasis, whereas overexpression of a dominant negative mutant promoted metastasis. Osteoclasts were directly affected and ERRα upregulated the osteoclastogenesis inhibitor, osteoprotegerin (OPG), providing a direct mechanistic basis for understanding how ERRα reduced breast cancer cell growth in bone. In contrast, ERRα overexpression increased breast cancer cell growth in the mammary gland. ERRα-overexpressing primary tumors were highly vascularized, consistent with an observed upregulation of angiogenic growth factor, the VEGF. In support of these findings, we documented that elevated expression of ERRα mRNA in breast carcinomas was associated with high expression of OPG and VEGF and with disease progression. In conclusion, our results show that ERRα plays a dual role in breast cancer progression in promoting the local growth of tumor cells, but decreasing metastatic growth of osteolytic lesions in bone.     

Bevacizumab reduces tumor targeting of antiepidermal growth factor and anti‐insulin‐like growth factor 1 receptor antibodies

Bevacizumab (antivascular endothelial growth factor [anti‐VEGF]) and cetuximab (antiepidermal growth factor receptor [anti‐EGFR]) are approved antibodies for treatment of cancer. However, in advanced colorectal cancer, the combination fails to improve survival. As the reason for the lack of activity is unknown, our study aims to determine the effect of bevacizumab on targeting of anti‐EGFR and insulin‐like growth factor 1 receptor (IGF‐1R) antibodies in tumors with single‐photon emission computed tomography (SPECT)/CT imaging. Mice with subcutaneous EGFR and IGF‐1R‐expressing SUM149 xenografts received a single dose of bevacizumab (10 mg/kg) or saline. After 4 days, mice were injected with radiolabeled cetuximab or R1507, an anti‐IGF‐1R antibody. A control group received a radiolabeled irrelevant IgG (hLL2). Three days later, SPECT/CT images were acquired and mice were dissected to determine the concentration of antibodies in the tissues. Tumors were analyzed immunohistochemically to determine vascular density (CD34), VEGF, EGFR and IGF‐1R expression. SPECT/CT imaging revealed that bevacizumab treatment significantly reduced tumor targeting of radiolabeled cetuximab by 40% from 33.1 ± 1.1 %ID/g to 19.8 ± 5.7 %ID/g (p = 0.009) for untreated and bevacizumab‐treated tumors, respectively. A similar effect was found for ¹¹¹In‐R1507: tumor targeting of R1507 decreased by 35%. No significant differences in tumor uptake were observed in mice that received an irrelevant IgG. Uptake in normal organs was not altered by bevacizumab. Immunohistochemical analysis showed that vascular density decreased with 43%, whereas EGFR and IGF‐1R expression was unaltered. In conclusion, bevacizumab treatment significantly reduces tumor targeting of anti‐EGFR and anti‐IGF‐1R antibodies. This emphasizes the importance of timing and sequencing of bevacizumab in combination with other antibodies.     

Novel human Ab against vascular endothelial growth factor receptor 2 shows therapeutic potential for leukemia and prostate cancer

Vascular endothelial growth factor receptor 2 (VEGFR2) is highly expressed in tumor‐associated endothelial cells, where it modulates tumor‐promoting angiogenesis, and it is also found on the surface of tumor cells. Currently, there are no Ab therapeutics targeting VEGFR2 approved for the treatment of prostate cancer or leukemia. Therefore, development of novel efficacious anti‐VEGFR2 Abs will benefit cancer patients. We used the Institute of Cellular and Organismic Biology human Ab library and affinity maturation to develop a fully human Ab, anti‐VEGFR2‐AF, which shows excellent VEGFR2 binding activity. Anti‐VEGFR2‐AF bound Ig‐like domain 3 of VEGFR2 extracellular region to disrupt the interaction between VEGF‐A and VEGFR2, neutralizing downstream signaling of the receptor. Moreover, anti‐VEGFR2‐AF inhibited capillary structure formation and exerted Ab‐dependent cell‐mediated cytotoxicity and complement‐dependent cytotoxicity in vitro. We found that VEGFR2 is expressed in PC‐3 human prostate cancer cell line and associated with malignancy and metastasis of human prostate cancer. In a PC‐3 xenograft mouse model, treatment with anti‐VEGFR2‐AF repressed tumor growth and angiogenesis as effectively and safely as US FDA‐approved anti‐VEGFR2 therapeutic, ramucirumab. We also report for the first time that addition of anti‐VEGFR2 Ab can enhance the efficacy of docetaxel in the treatment of a prostate cancer mouse model. In HL‐60 human leukemia‐xenografted mice, anti‐VEGFR2‐AF showed better efficacy than ramucirumab with prolonged survival and reduced metastasis of leukemia cells to ovaries and lymph nodes. Our findings suggest that anti‐VEGFR2‐AF has strong potential as a cancer therapy that could directly target VEGFR2‐expressing tumor cells in addition to its anti‐angiogenic action.     

A mechanism-based combination therapy reduces local tumor growth and metastasis in an orthotopic model of prostate cancer

Therapy-induced stimulation of angiogenic molecules can promote tumor angiogenesis leading to enhanced tumor growth and cancer metastasis. Several standard and emerging therapies, such as radiation and photodynamic therapy (PDT), can induce angiogenic molecules, thus limiting their effectiveness. PDT is approved for the treatment of several cancers; however, its induction of vascular endothelial growth factor (VEGF) creates conditions favorable to enhanced tumor growth and metastasis, therefore mitigating its cytotoxic and antivascular effects. This is the first report showing that subcurative PDT in an orthotopic model of prostate cancer (LNCaP) increases not only VEGF secretion (2.1-fold) but also the fraction of animals with lymph node metastases. PDT followed by administration of an antiangiogenic agent, TNP-470, abolished this increase and reduced local tumor growth. On the other hand, administration of TNP-470 before PDT was less effective at local tumor control. In addition, animals in all groups, except in the PDT + TNP-470 group, had a weight loss of >3 g at the time of sacrifice; the weight of the animals in the PDT + TNP-470 group did not change. The significant reduction (P < 0.05) in tumor weight and volume observed between the PDT + TNP-470 group and the control group suggests that the combination of PDT and antiangiogenic treatment administered in the appropriate sequence was not only more effective at controlling local tumor growth and metastases but also reduced disease-related toxicities. Such molecular response-based combinations merit further investigations as they enhance both monotherapies and lead to improved treatment outcomes.     

Lessons from phase III clinical trials on anti-VEGF therapy for cancer

In randomized phase III trials two anti-vascular endothelial growth factor (VEGF) approaches have yielded survival benefit in patients with metastatic cancer. In one approach, the addition of bevacizumab, a VEGF-specific antibody, to standard chemotherapy improved overall survival in colorectal and lung cancer patients and progression-free survival in breast cancer patients. In the second approach, multitargeted tyrosine kinase inhibitors that block VEGF receptor and other kinases in both endothelial and cancer cells, demonstrated survival benefit in gastrointestinal stromal tumor and renal-cell-carcinoma patients. By contrast, adding bevacizumab to chemotherapy failed to increase survival in patients with previously treated and refractory metastatic breast cancer. Furthermore, addition of vatalanib, a kinase inhibitor developed as a VEGF receptor-selective agent, to chemotherapy did not show a similar benefit in metastatic colorectal cancer patients. These contrasting responses raise critical questions about how these agents work and how to combine them optimally. We summarize three of the many potential mechanisms of action of anti-VEGF agents, and also discuss progress relating to the identification of potential biomarkers for anti-VEGF-agent efficacy in humans.     

Cathepsin G-mediated enhanced TGF-β signaling promotes angiogenesis via upregulation of VEGF and MCP-1

Transforming growth factor (TGF)-β signaling makes a significant contribution to the pathogenesis of breast cancer bone metastasis. In other tumor types, TGF-β has been shown to promote tumor vascularity. Here, we report that inhibition of TGF-β significantly reduces microvessel density in mammary tumor-induced bone lesions, mediated by decreased expression of both vascular endothelial growth factor (VEGF) and monocyte chemotactic protein (MCP)-1, both known angiogenic factors. Cathepsin G upregulation at the tumor–bone interface has been linked to increased TGF-β signaling, and we also report that inhibition of Cathepsin G reduced tumor vascularity, as well as VEGF and MCP-1 expression.     

Target practice: lessons from phase III trials with bevacizumab and vatalanib in the treatment of advanced colorectal cancer

Vascular endothelial growth factor (VEGF) is one of the most important factors involved in tumor angiogenesis and has become an important target for anticancer treatment. In 2004, this approach was validated in a randomized, controlled phase III clinical trial. It was shown that the addition of bevacizumab, a humanized monoclonal antibody against VEGF-A, to conventional chemotherapy prolonged survival over chemotherapy alone in patients with metastatic colorectal cancer. In this review, we discuss the results of the clinical trials that have led to the incorporation of antiangiogenic agents into the treatment of patients with advanced colorectal cancer. We limit ourselves to the two agents that have been tested extensively in phase III trials: bevacizumab and vatalanib, a small molecule tyrosine kinase inhibitor against VEGF receptors. In addition, we discuss the adverse effects of bevacizumab and vatalanib and the clinical management of the side effects.     

Anti‐bevacizumab idiotype antibody vaccination is effective in inducing vascular endothelial growth factor‐binding response,impairing tumor outgrowth

Tumors require blood supply and, to overcome this restriction, induce angiogenesis. Vascular endothelial growth factor (VEGF) plays an important role in this process, which explains the great number of antiangiogenic therapies targeting VEGF. The research and development of targeted therapy has led to the approval of bevacizumab, a humanized anti‐VEGF monoclonal antibody (mAb), in clinical settings. However, side effects have been reported, usually as a consequence of bolus‐dose administration of the antibody. This limitation could be circumvented through the use of anti‐idiotype (Id) antibodies. In the present study, we evaluated the efficacy of an active VEGF‐binding immune response generated by an anti‐bevacizumab idiotype mAb, 10.D7. The 10.D7 anti‐Id mAb vaccination led to detectable levels of VEGF‐binding anti‐anti‐Id antibodies. In order to examine whether this humoral immune response could have implications for tumor development, 10.D7‐immunized mice were challenged with B16‐F10 tumor cells. Mice immunized with 10.D7 anti‐Id mAb revealed reduced tumor growth when compared to control groups. Histological analyses of tumor sections from 10.D7‐immunized mice showed increased necrotic areas, decreased CD31‐positive vascular density and reduced CD68‐positive cell infiltration. Our results encourage further therapeutic studies, particularly if one considers that the anti‐Id therapeutic vaccination maintains stable levels of VEGF‐binding antibodies, which might be useful in the control of tumor relapse.     

In vitro the behaviors of metastasis with suppression of VEGF in human bone metastatic LNCaP-derivative C4-2B prostate cancer cell line

ABSTRACT: BACKGROUND: Vascular endothelial growth factor (VEGF) is a signal protein produced by cells that stimulates vasculogenesis and angiogenesis. VEGF is believed to implicate poor prognosis in various cancers. The overexpression of VEGF may be an early step in the process of metastasis. METHODS: ELISA was used to investigate the levels of VEGF, bFGF and IL8 in human bone metastatic LNCaP-derivative C4-2B prostate cancer cell line and its parental cell line, LNCa-P, and to determine the effect of bevacizumab on reducing the level of VEGF. Cell proliferation assay, invasion assay and in vitro angiogenesis assay were performed under the condition with bevacizumab or control IgG. RESULTS: Human bone metastatic LNCaP-derivative C4-2B prostate cancer cell line expressed a higher level of VEGF than its parental primary prostate cancer cell line LNCaP. The effect of bevacizumab is dose-dependent and time-dependent: 100 ug/mL of bevacizumab and 3-day treatment was more effective than low-dose and lesser-day treatment for decreasing the level of VEGF. Bevacizumab is able to suppress cell proliferation, angiogenesis and invasion in human bone metastatic C4-2B prostatic cancer cell line. CONCLUSIONS: The overexpression of VEGF can be inhibited by bevacizumab in human bone metastatic cancer cell line. The behaviors of metastasis involving proliferation, angiogenesis and invasion are suppressed by anti-VEGF therapy.     

Molecular basis of the synergistic antiangiogenic activity of bevacizumab and mithramycin A

The impact of antiangiogenic therapy on the Sp1/vascular endothelial growth factor (VEGF) pathway and that of alteration of Sp1 signaling on the efficacy of antiangiogenic therapy is unclear, yet understanding their interactions has significant clinical implications. Treatment with bevacizumab, a neutralizing antibody against VEGF, suppressed human pancreatic cancer growth in nude mice. Gene expression analyses revealed that this treatment substantially up-regulated the expression of Sp1 and its downstream target genes, including VEGF and epidermal growth factor receptor, in tumor tissues, whereas it did not have this effect on pancreatic cancer cells in culture. Treatment with mithramycin A, an Sp1 inhibitor, suppressed the expression of Sp1 and its downstream target genes in both cell culture and tumors growing in nude mice. Combined treatment with bevacizumab and mithramycin A produced synergistic tumor suppression, which was consistent with suppression of the expression of Sp1 and its downstream target genes. Thus, treatment with bevacizumab may block VEGF function but activate the pathway of its expression via positive feedback. Given the fact that Sp1 is an important regulator of the expression of multiple angiogenic factors, bevacizumab-initiated up-regulation of Sp1 and subsequent overexpression of its downstream target genes may profoundly affect the potential angiogenic phenotype and effectiveness of antiangiogenic strategies for human pancreatic cancer. Therefore, this study is the first to show the significance and clinical implications of alteration of Sp1 signaling in antiangiogenic therapy for pancreatic cancer and other cancers.     

Human breast tumors override the antiangiogenic effect of stromal thrombospondin-1 in vivo

The antiangiogenic extracellular matrix protein thrombospondin-1 (TSP-1) inhibits tumor growth and metastasis in animals. However, the clinical relevance of such findings are equivocal as increased stromal TSP-1 expression has been associated with either good or poor prognosis. In an effort to obtain a more integrated understanding of the role of TSP-1 in breast cancer, we first used a breast tumorigenesis model in which tumor-associated stromal fibroblasts were engineered to produce high levels of TSP-1. We demonstrate here that stromal TSP-1 delayed human MDA-MB-231/B02 breast tumor growth. However, this delay in MDA-MB-231/B02 tumor growth upon exposure to TSP-1 was associated with an increased vascular endothelial growth factor (VEGF) expression in tumor cells themselves, leading to a tumor growth rate comparable to that of tumors whose fibroblasts did not overproduce TSP-1. Clinical evidence also suggested that primary breast carcinomas have adapted to escape the effects of stromal TSP-1. TSP-1 was found to be expressed in the stroma of human breast carcinomas where, although its level correlated with decreased vascularization, it was unexpectedly associated with a reduction of relapse-free survival. In metastatic axillary lymph nodes, tumor cells expressed high levels of VEGF and TSP-1 expression were no longer associated with a decreased vascularization. Overall, these results suggest that a resistance may develop early in human breast cancers as a result of high in situ exposure to stromal TSP-1, leading to disease progression.     

A cathepsin K inhibitor reduces breast cancer induced osteolysis and skeletal tumor burden

Osteoclasts mediate bone destruction in breast cancer skeletal metastases. Cathepsin K is a proteinase that is secreted by osteoclasts and degrades bone. Here, immunohistochemistry revealed that cathepsin K was expressed not only by osteoclasts but also by breast cancer cells that metastasize to bone. Following intratibial injection with cathepsin K-expressing human BT474 breast cancer cells, tumor-bearing mice treated with a clinical dosing regimen of cathepsin K inhibitor (CKI; 50 mg/kg, twice daily) had osteolytic lesions that were 79% smaller than those of tumor-bearing mice treated with the vehicle. The effect of CKI was also studied in a mouse model in which the i.v. inoculation of human B02 breast cancer cells expressing cathepsin K leads to bone metastasis formation. Drug administration was started before (preventive protocol) or after (treatment protocol) the occurrence of osteolytic lesions. In treatment protocols, CKI (50 mg/kg, twice daily) or a single clinical dose of 100 microg/kg zoledronic acid (osteoclast inhibitor) reduced the progression of osteolytic lesions by 59% to 66%. CKI therapy also reduced skeletal tumor burden by 62% compared with vehicle, whereas zoledronic acid did not decrease the tumor burden. The efficacy of CKI at inhibiting skeletal tumor burden was similar in the treatment and preventive protocols. By contrast, CKI did not block the growth of s.c. B02 tumor xenografts in animals. Thus, CKI may render the bone a less favorable microenvironment for tumor growth by inhibiting bone resorption. These findings raise the possibility that cathepsin K could be a therapeutic target for the treatment of bone metastases.     

Combination of fractionated irradiation with anti‐VEGF expressing vaccinia virus therapy enhances tumor control by simultaneous radiosensitization of tumor associated endothelium

Oncolytic viruses are currently in clinical trials for a variety of tumors, including high grade gliomas. A characteristic feature of high grade gliomas is their high vascularity and treatment approaches targeting tumor endothelium are under investigation, including bevacizumab. The aim of this study was to improve oncolytic viral therapy by combining it with ionizing radiation and to radiosensitize tumor vasculature through a viral encoded anti‐angiogenic payload. Here, we show how vaccinia virus‐mediated expression of a single‐chain antibody targeting VEGF resulted in radiosensitization of the tumor‐associated vasculature. Cell culture experiments demonstrated that purified vaccinia virus encoded antibody targeting VEGF reversed VEGF‐induced radioresistance specifically in endothelial cells but not tumor cells. In a subcutaneous model of U‐87 glioma, systemically administered oncolytic vaccinia virus expressing anti‐VEGF antibody (GLV‐1h164) in combination with fractionated irradiation resulted in enhanced tumor growth inhibition when compared to nonanti‐VEGF expressing oncolytic virus (GLV‐1h68) and irradiation. Irradiation of tumor xenografts resulted in an increase in VACV replication of both GLV‐1h68 and GLV‐1h164. However, GLV‐1h164 in combination with irradiation resulted in a drastic decrease in intratumoral VEGF levels and tumor vessel numbers in comparison to GLV‐1h68 and irradiation. These findings demonstrate the incorporation of an oncolytic virus expressing an anti‐VEGF antibody (GLV‐1h164) into a fractionated radiation scheme to target tumor cells by enhanced VACV replication in irradiated tumors as well as to radiosensitize tumor endothelium which results in enhanced efficacy of combination therapy of human glioma xenografts.     

CXCR4 peptide antagonist inhibits primary breast tumor growth,metastasis and enhances the efficacy of anti‐VEGF treatment or docetaxel in a transgenic mouse model

CXCR4 is a chemokine receptor implicated in the homing of cancer cells to target metastatic organs, which overexpress its ligand, stromal cell‐derived factor (SDF)‐1. To determine the efficacy of targeting CXCR4 on primary tumor growth and metastasis, we used a peptide inhibitor of CXCR4, CTCE‐9908, that was administered in a clinically relevant approach using a transgenic breast cancer mouse model. We first performed a dosing experiment of CTCE‐9908 in the PyMT mouse model, testing 25, 50 and 100 mg/kg versus the scrambled peptide in groups of 8–16 mice. We then combined CTCE‐9908 with docetaxel or DC101 (an anti‐VEGFR2 monoclonal antibody). We found that increasing doses of CTCE‐9908 alone slowed the rate of tumor growth, with a 45% inhibition of primary tumor growth at 3.5 weeks of treatment with 50 mg/kg of CTCE‐9908 (p = 0.005). Expression levels of VEGF were also found to be reduced by 42% with CTCE‐9908 (p = 0.01). In combination with docetaxel, CTCE‐9908 administration decreased tumor volume by 38% (p = 0.02), an effect that was greater than that observed with docetaxel alone. In combination with DC101, CTCE‐9908 also demonstrated an enhanced effect compared to DC101 alone, with a 37% decrease in primary tumor volume (p = 0.01) and a 75% reduction in distant metastasis (p = 0.009). In combination with docetaxel or an anti‐angiogenic agent, the anti‐tumor and anti‐metastatic effects of CTCE‐9908 were markedly enhanced, suggesting potentially new effective combinatorial therapeutic strategies in the treatment of breast cancer, which include targeting the SDF‐1/CXCR4 ligand/receptor pair.