PMCC PMCC

Search tips
Search criteria

Advanced
Results 1-25 (148)
 

Clipboard (0)
None

Select a Filter Below

Journals
more »
Year of Publication
more »
1.  A Safety and Survival Analysis of Neoadjuvant Bevacizumab With Standard Chemoradiation in a Phase I/II Study Compared With Standard Chemoradiation in Locally Advanced Rectal Cancer 
The oncologist  2010;15(8):845-851.
Introduction
Bevacizumab is increasingly being tested with neoadjuvant regimens in patients with localized cancer, but its effects on metastasis and survival remain unknown. This study examines the long-term outcome of clinical stage II/III rectal cancer patients treated in a prospective phase II study of bevacizumab with chemoradiation and surgery. As a benchmark, we used data from an analysis of 42 patients with locally advanced rectal cancer treated with a contemporary approach of preoperative fluoropyrimidine-based radiation therapy.
Materials and Methods
Outcome analyses were performed on 32 patients treated prospectively with neoadjuvant bevacizumab, 5-fluorouracil, radiation therapy, and surgery as well as 42 patients treated with standard fluoropyrimidine-based chemoradiation.
Results
Overall survival, disease-free survival, and local control showed favorable trends in patients treated with bevacizumab with chemoradiation followed by surgery. Acute and postoperative toxicity appeared acceptable.
Conclusions
Neoadjuvant bevacizumab with standard chemoradiation and surgery shows promising long-term efficacy and safety profiles in locally advanced rectal cancer patients.
doi:10.1634/theoncologist.2010-0030
PMCID: PMC3078712  PMID: 20667969
Bevacizumab; Neoadjuvant; Rectal cancer; Chemoradiation; Toxicity
2.  Changes in Biomarkers of Inflammation and Angiogenesis During Androgen Deprivation Therapy for Prostate Cancer 
The Oncologist  2012;17(2):212-219.
Inflammatory and angiogenic biomarkers were measured in androgen deprivation therapy–treated and control groups of men with prostate cancer. Significantly higher concentrations of some inflammatory biomarkers were found in the treatment group.
Introduction.
Angiogenesis and inflammation are both important to the pathogenesis of malignancies. Androgen deprivation therapy (ADT) for prostate cancer causes drastic hormonal changes that alter both disease and host factors. We measured inflammatory and angiogenic biomarkers in ADT-treated and control groups of men with prostate cancer.
Materials and Methods.
Baseline and 12-week plasma samples were collected from 37 ADT-naïve men with locally advanced or recurrent prostate cancer. Of those, 23 initiated ADT with a gonadotropin-releasing hormone (GnRH) agonist and 14 served as nontreatment controls. Samples were tested for a panel of angiogenic and inflammatory biomarkers.
Results.
The treatment group had significantly higher concentrations of the inflammatory biomarkers interleukin (IL)-1β, IL-6, IL-8, tumor necrosis factor (TNF)-α, and stromal cell–derived factor (SDF)-1α. None of the angiogenic biomarkers were significantly different between the groups at baseline. Among patients with a short prostate-specific antigen (PSA) doubling time (<6 months), the proangiogenic factor basic fibroblast growth factor (bFGF) was lower at baseline. In the treatment group, plasma placental growth factor (PlGF) increased and IL-6 decreased after 12 weeks of ADT. Moreover, the treatment group continued to have significantly higher concentrations of the inflammatory biomarkers IL-1β, IL-8, and SDF-1α as well as bFGF than controls.
Discussion.
These men were characterized by elevations in several traditional markers of aggressive disease and also by higher levels of several inflammatory biomarkers. Although ADT decreased IL-6 levels, IL-1β, IL-8, and SDF-1α remained significantly higher than in controls. The role of these biomarkers should be further explored.
doi:10.1634/theoncologist.2011-0321
PMCID: PMC3286170  PMID: 22302227
3.  Phase III Randomized Trial Comparing the Efficacy of Cediranib As Monotherapy, and in Combination With Lomustine, Versus Lomustine Alone in Patients With Recurrent Glioblastoma 
Journal of Clinical Oncology  2013;31(26):3212-3218.
Purpose
A randomized, phase III, placebo-controlled, partially blinded clinical trial (REGAL [Recentin in Glioblastoma Alone and With Lomustine]) was conducted to determine the efficacy of cediranib, an oral pan–vascular endothelial growth factor (VEGF) receptor tyrosine kinase inhibitor, either as monotherapy or in combination with lomustine versus lomustine in patients with recurrent glioblastoma.
Patients and Methods
Patients (N = 325) with recurrent glioblastoma who previously received radiation and temozolomide were randomly assigned 2:2:1 to receive (1) cediranib (30 mg) monotherapy; (2) cediranib (20 mg) plus lomustine (110 mg/m2); (3) lomustine (110 mg/m2) plus a placebo. The primary end point was progression-free survival based on blinded, independent radiographic assessment of postcontrast T1-weighted and noncontrast T2-weighted magnetic resonance imaging (MRI) brain scans.
Results
The primary end point of progression-free survival (PFS) was not significantly different for either cediranib alone (hazard ratio [HR] = 1.05; 95% CI, 0.74 to 1.50; two-sided P = .90) or cediranib in combination with lomustine (HR = 0.76; 95% CI, 0.53 to 1.08; two-sided P = .16) versus lomustine based on independent or local review of postcontrast T1-weighted MRI.
Conclusion
This study did not meet its primary end point of PFS prolongation with cediranib either as monotherapy or in combination with lomustine versus lomustine in patients with recurrent glioblastoma, although cediranib showed evidence of clinical activity on some secondary end points including time to deterioration in neurologic status and corticosteroid-sparing effects.
doi:10.1200/JCO.2012.47.2464
PMCID: PMC4021043  PMID: 23940216
4.  A Safety and Survival Analysis of Neoadjuvant Bevacizumab with Standard Chemoradiation in a Phase I/II Study Compared with Standard Chemoradiation in Locally Advanced Rectal Cancer 
The Oncologist  2010;15(8):845-851.
This study examines the long-term outcome of clinical stage II/III rectal cancer patients treated in a prospective phase II study of bevacizumab with chemoradiation and surgery. Neoadjuvant bevacizumab with standard chemoradiation and surgery shows promising long-term efficacy and safety profiles in locally advanced rectal cancer patients.
Introduction.
Bevacizumab is increasingly being tested with neoadjuvant regimens in patients with localized cancer, but its effects on metastasis and survival remain unknown. This study examines the long-term outcome of clinical stage II/III rectal cancer patients treated in a prospective phase II study of bevacizumab with chemoradiation and surgery. As a benchmark, we used data from an analysis of 42 patients with locally advanced rectal cancer treated with a contemporary approach of preoperative fluoropyrimidine-based radiation therapy.
Materials and Methods.
Outcome analyses were performed on 32 patients treated prospectively with neoadjuvant bevacizumab, 5-fluorouracil, radiation therapy, and surgery as well as 42 patients treated with standard fluoropyrimidine-based chemoradiation.
Results.
Overall survival, disease-free survival, and local control showed favorable trends in patients treated with bevacizumab with chemoradiation followed by surgery. Acute and postoperative toxicity appeared acceptable.
Conclusions.
Neoadjuvant bevacizumab with standard chemoradiation and surgery shows promising long-term efficacy and safety profiles in locally advanced rectal cancer patients.
doi:10.1634/theoncologist.2010-0030
PMCID: PMC3078712  PMID: 20667969
Bevacizumab; Neoadjuvant; Rectal cancer; Chemoradiation; Toxicity
5.  Plasma Soluble VEGFR-1 Is a Potential Dual Biomarker of Response and Toxicity for Bevacizumab with Chemoradiation in Locally Advanced Rectal Cancer 
The Oncologist  2010;15(6):577-583.
The article explores plasma and urinary concentrations of two members of the vascular endothelial growth factor family and their receptors as potential response and toxicity biomarkers of bevacizumab with neoadjuvant chemoradiation in patients with localized rectal cancer.
We explored plasma and urinary concentrations of two members of the vascular endothelial growth factor (VEGF) family and their receptors as potential response and toxicity biomarkers of bevacizumab with neoadjuvant chemoradiation in patients with localized rectal cancer. The concentrations of VEGF, placental growth factor (PlGF), soluble VEGF receptor 1 (sVEGFR-1), and sVEGFR-2 were measured in plasma and urine at baseline and during treatment. Pretreatment values and changes over time were analyzed as potential biomarkers of pathological response to treatment as well as for acute toxicity in patients with locally advanced rectal cancer treated prospectively in 2002–2008 with neoadjuvant bevacizumab, 5-fluorouracil, radiation therapy, and surgery in a phase I/II trial. Of all biomarkers, pretreatment plasma sVEGFR-1—an endogenous blocker of VEGF and PlGF, and a factor linked with “vascular normalization”—was associated with both primary tumor regression and the development of adverse events after neoadjuvant bevacizumab and chemoradiation. Based on the findings in this exploratory study, we propose that plasma sVEGFR-1 should be further studied as a potential biomarker to stratify patients in future studies of bevacizumab and/or cytotoxics in the neoadjuvant setting.
doi:10.1634/theoncologist.2010-0029
PMCID: PMC3061828  PMID: 20484123
Bevacizumab; sVEGFR-1; Biomarker; Rectal cancer; Chemoradiation; Toxicity
6.  Effects of Vascular-Endothelial Protein Tyrosine Phosphatase Inhibition on Breast Cancer Vasculature and Metastatic Progression 
Background
The solid tumor microvasculature is characterized by structural and functional abnormality and mediates several deleterious aspects of tumor behavior. Here we determine the role of vascular endothelial protein tyrosine phosphatase (VE-PTP), which deactivates endothelial cell (EC) Tie-2 receptor tyrosine kinase, thereby impairing maturation of tumor vessels.
Methods
AKB-9778 is a first-in-class VE-PTP inhibitor. We examined its effects on ECs in vitro and on embryonic angiogenesis in vivo using zebrafish assays. We studied the impact of AKB-9778 therapy on the tumor vasculature, tumor growth, and metastatic progression using orthotopic models of murine mammary carcinoma as well as spontaneous and experimental metastasis models. Finally, we used endothelial nitric oxide synthase (eNOS)–deficient mice to establish the role of eNOS in mediating the effects of VE-PTP inhibition. All statistical tests were two-sided.
Results
AKB-9778 induced ligand-independent Tie-2 activation in ECs and impaired embryonic zebrafish angiogenesis. AKB-9778 delayed the early phase of mammary tumor growth by maintaining vascular maturity (P < .01, t test); slowed growth of micrometastases (P < .01, χ2 test) by preventing extravasation of tumor cells (P < 0.01, Fisher exact test), resulting in a trend toward prolonged survival (27.0 vs 36.5 days; hazard ratio of death = 0.33, 95% confidence interval = 0.11 to 1.03; P = .05, Mantel–Cox test); and stabilized established primary tumor blood vessels, enhancing tumor perfusion (P = .03 for 4T1 tumor model and 0.05 for E0771 tumor model, by two-sided t tests) and, hence, radiation response (P < .01, analysis of variance; n = 7 mice per group). The effects of AKB-9778 on tumor vessels were mediated in part by endothelial nitric oxide synthase activation.
Conclusions
Our results demonstrate that pharmacological VE-PTP inhibition can normalize the structure and function of tumor vessels through Tie-2 activation, which delays tumor growth, slows metastatic progression, and enhances response to concomitant cytotoxic treatments.
doi:10.1093/jnci/djt164
PMCID: PMC3748004  PMID: 23899555
7.  Increase in tumor-associated macrophages after antiangiogenic therapy is associated with poor survival among patients with recurrent glioblastoma 
Neuro-Oncology  2013;15(8):1079-1087.
Antiangiogenic therapy is associated with increased radiographic responses in glioblastomas, but tumors invariably recur. Because tumor-associated macrophages have been shown to mediate escape from antiangiogenic therapy in preclinical models, we examined the role of macrophages in patients with recurrent glioblastoma. We compared autopsy brain specimens from 20 patients with recurrent glioblastoma who received antiangiogenic treatment and chemoradiation with 8 patients who received chemotherapy and/or radiotherapy without antiangiogenic therapy or no treatment. Tumor-associated macrophages were morphologically and phenotypically analyzed using flow cytometry and immunohistochemistry for CD68, CD14, CD163, and CD11b expression. Flow cytometry showed an increase in macrophages in the antiangiogenic-treated patients. Immunohistochemical analysis demonstrated an increase in CD68+ macrophages in the tumor bulk (P < .01) and infiltrative areas (P = .02) in antiangiogenic-treated patients. We also observed an increase in CD11b+ cells in the tumor bulk (P < .01) and an increase in CD163+ macrophages in infiltrative tumor (P = .02). Of note, an increased number of CD11b+ cells in bulk and infiltrative tumors (P = .05 and P = .05, respectively) correlated with poor overall survival among patients who first received antiangiogenic therapy at recurrence. In summary, recurrent glioblastomas showed an increased infiltration in myeloid populations in the tumor bulk and in the infiltrative regions after antiangiogenic therapy. Higher numbers of CD11b+ cells correlated with poor survival among these patients. These data suggest that tumor-associated macrophages may participate in escape from antiangiogenic therapy and may represent a potential biomarker of resistance and a potential therapeutic target in recurrent glioblastoma.
doi:10.1093/neuonc/not082
PMCID: PMC3714160  PMID: 23828240
antiangiogenic therapy; glioblastoma; myeloid cells; relapse
8.  The role of mechanical forces in tumor growth and therapy 
Tumors generate physical forces during growth and progression. These physical forces are able to compress blood and lymphatic vessels, reducing perfusion rates and creating hypoxia. When exerted directly on cancer cells, they can increase their invasive and metastatic potential. Tumor vessels - while nourishing the tumor - are usually leaky and tortuous, which further decreases perfusion. Hypo-perfusion and hypoxia contribute to immune-evasion, promote malignant progression and metastasis, and reduce the efficacy of a number of therapies, including radiation. In parallel, vessel leakiness together with vessel compression cause a uniformly elevated interstitial fluid pressure that hinders delivery of blood-borne therapeutic agents, lowering the efficacy of chemo- and nano-therapies. In addition, shear stresses exerted by flowing blood and interstitial fluid modulate the behavior of cancer and a variety of host cells. Taming these physical forces can improve therapeutic outcomes in many cancers.
doi:10.1146/annurev-bioeng-071813-105259
PMCID: PMC4109025  PMID: 25014786
tumor microenvironment; vessel compression; tumor perfusion; vascular hyper-permeability; vascular normalization; residual stress; stress alleviation
9.  Co-evolution of solid stress and interstitial fluid pressure in tumors during progression: Implications for vascular collapse 
Cancer research  2013;73(13):3833-3841.
The stress harbored by the solid phase of tumors is known as solid stress. Solid stress can be either applied externally by the surrounding normal tissue or induced by the tumor itself due to its growth. Fluid pressure is the isotropic stress exerted by the fluid phase. We recently demonstrated that growth-induced solid stress is on the order of 1.3–13.0 kPa (10–100 mmHg) - high enough to cause compression of fragile blood vessels resulting in poor perfusion and hypoxia. However, the evolution of growth-induced stress with tumor progression and its effect on cancer cell proliferation in vivo is not understood. To this end, we developed a mathematical model for tumor growth that takes into account all three types of stresses: growth-induced stress, externally applied stress and fluid pressure. First, we performed in vivo experiments and found that growth-induced stress is related to tumor volume through a bi-exponential relationship. Then, we incorporated this information into our mathematical model and showed that due to the evolution of growth-induced stress, total solid stress levels are higher in the tumor interior and lower in the periphery. Elevated compressive solid stress in the interior of the tumor is sufficient to cause the collapse of blood vessels and results in a lower growth rate of cancer cells compared to the periphery, independently from that caused by the lack of nutrients due to vessel collapse. Furthermore, solid stress in the periphery of the tumor causes blood vessels in the surrounding normal tissue to deform to elliptical shapes. We present histological sections of human cancers that demonstrate such vessel deformations. Finally, we found that fluid pressure increases with tumor growth due to increased vascular permeability and lymphatic impairment, and is governed by the microvascular pressure. Crucially, fluid pressure does not cause vessel compression of tumor vessels.
Major Findings. Growth-induced solid stress is accumulated in tumors during growth. Growth-induced and externally applied solid stresses are additive and might affect cancer cell growth in two ways: directly by compressing cancer cells and indirectly by deforming blood vessels and thus, reducing delivery of nutrients.
doi:10.1158/0008-5472.CAN-12-4521
PMCID: PMC3702668  PMID: 23633490
tumor microenvironment; mathematical modeling; vessel compression; cancer pathophysiology
10.  Normalizing Tumor Microenvironment to Treat Cancer: Bench to Bedside to Biomarkers 
Journal of Clinical Oncology  2013;31(17):2205-2218.
For almost four decades, my work has focused on one challenge: improving the delivery and efficacy of anticancer therapeutics. Working on the hypothesis that the abnormal tumor microenvironment—characterized by hypoxia and high interstitial fluid pressure—fuels tumor progression and treatment resistance, we developed an array of sophisticated imaging technologies and animal models as well as mathematic models to unravel the complex biology of tumors. Using these tools, we demonstrated that the blood and lymphatic vasculature, fibroblasts, immune cells, and extracellular matrix associated with tumors are abnormal, which together create a hostile tumor microenvironment. We next hypothesized that agents that induce normalization of the microenvironment can improve treatment outcome. Indeed, we demonstrated that judicious use of antiangiogenic agents—originally designed to starve tumors—could transiently normalize tumor vasculature, alleviate hypoxia, increase delivery of drugs and antitumor immune cells, and improve the outcome of various therapies. Our trials of antiangiogenics in patients with newly diagnosed and recurrent glioblastoma supported this concept. They revealed that patients whose tumor blood perfusion increased in response to cediranib survived 6 to 9 months longer than those whose blood perfusion did not increase. The normalization hypothesis also opened doors to treating various nonmalignant diseases characterized by abnormal vasculature, such as neurofibromatosis type 2. More recently, we discovered that antifibrosis drugs capable of normalizing the tumor microenvironment can improve the delivery and efficacy of nano- and molecular medicines. Our current efforts are directed at identifying predictive biomarkers and more-effective strategies to normalize the tumor microenvironment for enhancing anticancer therapies.
doi:10.1200/JCO.2012.46.3653
PMCID: PMC3731977  PMID: 23669226
12.  Vascular normalization as an emerging strategy to enhance cancer immunotherapy 
Cancer research  2013;73(10):2943-2948.
The recent approval of Provenge has brought new hope for anti-cancer vaccine therapies. However, the immunosuppressive tumor microenvironment seems to impair the efficacy of vaccine therapies. The abnormal tumor vasculature creates a hypoxic microenvironment that polarizes inflammatory cells toward immune suppression. Moreover, tumors systemically alter immune cells’ proliferation, differentiation and function via secretion of growth factors and cytokines. For example, vascular endothelial growth factor (VEGF), a major pro-angiogenic cytokine induced by hypoxia, plays a critical role in immunosuppression via these mechanisms. Hence, anti-angiogenic treatment may be an effective modality to potentiate immunotherapy. Here we discuss the local and systemic effects of VEGF on tumor immunity, and propose a potentially translatable strategy to re-engineer the tumor immune microenvironment and improve cancer immunotherapy by using lower “vascular normalizing” doses of anti-angiogenic agents.
doi:10.1158/0008-5472.CAN-12-4354
PMCID: PMC3655127  PMID: 23440426
13.  Targeting placental growth factor/neuropilin 1 pathway inhibits growth and spread of medulloblastoma 
Cell  2013;152(5):1065-1076.
SUMMARY
Medulloblastoma is the most common pediatric malignant brain tumor. Although current therapies improve survival, these regimens are highly toxic and associated with significant morbidity. Here, we report that placental growth factor (PlGF) is expressed in the majority of medulloblastomas independent of their subtype. Moreover, high expression of PlGF receptor neuropilin 1 (Nrp1) correlates with poor overall survival in patients. We demonstrate that PlGF and Nrp1 are required for the growth and spread of medulloblastoma: PlGF/Nrp1 blockade results in direct antitumor effects in vivo, resulting in medulloblastoma regression, decreased metastases, and increased mouse survival. We reveal that PlGF is produced in the cerebellar stroma via tumor-derived Sonic hedgehog (Shh) and show that PlGF acts through Nrp1—and not vascular endothelial growth factor receptor 1 (VEGFR1)—to promote tumor cell survival. This critical tumor-stroma interaction—mediated by Shh, PlGF, and Nrp1 across medulloblastoma subtypes—supports the development of therapies targeting PlGF/Nrp1 pathway.
doi:10.1016/j.cell.2013.01.036
PMCID: PMC3587980  PMID: 23452854
14.  Cationic Nanoparticles Have Superior Transvascular Flux into Solid Tumors: Insights from a Mathematical Model 
Annals of biomedical engineering  2012;41(1):10.1007/s10439-012-0630-4.
Despite their great promise, only a few nanoparticle formulations have been approved for clinical use in oncology. The failure of nano-scale drugs to enhance cancer therapy is in large part due to inefficient delivery. To overcome this outstanding problem, a better understanding of how the physical properties (i.e., size, surface chemistry, and shape) of nanoparticles affect their transvascular transport in tumors is required. In this study, we developed a mathematical model for nanoparticle delivery to solid tumors taking into account electrostatic interactions between the particles and the negatively-charged pores of the vessel wall. The model predictions suggest that electrostatic repulsion has a minor effect on the transvascular transport of nanoparticles. On the contrary, electrostatic attraction, caused even by small cationic charges (surface charge density less than 3 × 10−3 C/m2) can lead to a twofold or more increase in the transvascular flux of nanoparticles into the tumor interstitial space. Importantly, for every nanoparticle size, there is a value of charge density above which a steep increase in transvascular transport is predicted. Our model provides important guidelines for the optimal design of nanoparticle formulation for delivery to solid tumors.
doi:10.1007/s10439-012-0630-4
PMCID: PMC3886728  PMID: 22855118
Vascular permeability; Electrostatic and hydrodynamic interactions; Surface charge density; Nanomedicine; Cancer therapy
15.  Video-rate resonant scanning multiphoton microscopy 
Intravital (Print)  2012;1(1):10.4161/intv.21557.
The abnormal tumor microenvironment fuels tumor progression, metastasis, immune suppression, and treatment resistance. Over last several decades, developments in and applications of intravital microscopy have provided unprecedented insights into the dynamics of the tumor microenvironment. In particular, intravital multiphoton microscopy has revealed the abnormal structure and function of tumor-associated blood and lymphatic vessels, the role of aberrant tumor matrix in drug delivery, invasion and metastasis of tumor cells, the dynamics of immune cell trafficking to and within tumors, and gene expression in tumors. However, traditional multiphoton microscopy suffers from inherently slow imaging rates—only a few frames per second, thus unable to capture more rapid events such as blood flow, lymphatic flow, and cell movement within vessels. Here, we report the development and implementation of a video-rate multiphoton microscope (VR-MPLSM) based on resonant galvanometer mirror scanning that is capable of recording at 30 frames per second and acquiring intravital multispectral images. We show that the design of the system can be readily implemented and is adaptable to various experimental models. As examples, we demonstrate the utility of the system to directly measure flow within tumors, capture metastatic cancer cells moving within the brain vasculature and cells in lymphatic vessels, and image acute responses to changes in a vascular network. VR-MPLSM thus has the potential to further advance intravital imaging and provide new insight into the biology of the tumor microenvironment.
doi:10.4161/intv.21557
PMCID: PMC3864876  PMID: 24353926
video-rate; multiphoton; tumor microenvironment; vessels; metastasis; lymphatics
16.  Neovascularization After Irradiation: What is the Source of Newly Formed Vessels in Recurring Tumors? 
Local relapse of tumors after radiation therapy remains a challenge in oncology. To devise rational approaches for preventing this relapse, we have to improve our understanding of how new vessels form in previously irradiated tumors. We propose that tumor regrowth after local irradiation is dependent on blood vessel formation by local endothelial cells without the need for recruitment of endothelial precursor cells from distant nonirradiated tissues or bone marrow. We also suggest that infiltrating myeloid bone marrow–derived cells promote survival of local endothelial cells during the early period after irradiation and angiogenesis during the later stage of tumor regrowth, both via paracrine mechanisms.
doi:10.1093/jnci/djs239
PMCID: PMC3379722  PMID: 22572994
17.  Metabolic Tumor Profiling with pH, Oxygen, and Glucose Chemosensors on a Quantum Dot Scaffold 
Inorganic chemistry  2013;53(4):1900-1915.
Synopsis
Acidity, hypoxia and glucose levels characterize the tumor microenvironment rendering pH, pO2 and pGlucose, respectively, important indicators of tumor health. To this end, understanding how these parameters change can be a powerful tool for the development of novel and effective therapeutics. We have designed optical chemosensors that feature a quantum dot and an analyte-responsive dye. These non-invasive chemosensors permit pH, oxygen, and glucose to be monitored dynamically within the tumor microenvironment by using multiphoton imaging.
doi:10.1021/ic401587r
PMCID: PMC3944830  PMID: 24143874
18.  CXCL12 (SDF1α) – CXCR4/CXCR7 Pathway Inhibition: An Emerging Sensitizer for Anti-Cancer Therapies? 
Addition of multiple molecularly targeted agents to the existing armamentarium of chemotherapeutics and radiotherapies represents a significant advance in the management of several advanced cancers. In certain tumor types with no efficacious therapy options, these agents have become the first line of therapy, e.g., sorafenib in advanced hepatocellular carcinoma or bevacizumab in recurrent glioblastoma. Unfortunately, in many cases, the survival benefits are modest, lasting only weeks to a few months. Moreover, they may not show benefit in patients with localized disease (i.e., in adjuvant setting). Recent studies have provided increasing evidence that activation of the chemokine CXCL12 (SDF1α) pathway is a potential mechanism of tumor resistance to both conventional therapies and biological agents via multiple complementary actions: (i) by directly promoting cancer cell survival, invasion and the cancer stem/tumor-initiating cell phenotype; (ii) by recruiting “distal stroma” (i.e., myeloid bone marrow-derived cells) to indirectly facilitate tumor recurrence and metastasis; and (iii) by promoting angiogenesis directly or in a paracrine manner. Here, we discuss recent preclinical and clinical data that support the potential use of anti-CXCL12 agents (e.g., AMD3100, NOX-A12 or CCX2066) as sensitizers to currently available therapies by targeting the CXCL12/CXCR4 and CXCL12/CXCR7 pathways.
doi:10.1158/1078-0432.CCR-10-2636
PMCID: PMC3079023  PMID: 21349998
19.  Merlin/NF2 Regulates Angiogenesis in Schwannomas through a Rac1/Semaphorin 3F-Dependent Mechanism1 
Neoplasia (New York, N.Y.)  2012;14(2):84-94.
Neurofibromatosis type 2 (NF2) is an autosomal-dominant multiple neoplasia syndrome that results from mutations in the NF2 tumor suppressor gene. Patients with NF2 develop hallmark schwannomas that require surgery or radiation, both of which have significant adverse effects. Recent studies have indicated that the tumor microenvironment—in particular, tumor blood vessels—of schwannomas may be an important therapeutic target. Furthermore, although much has been done to understand how merlin, the NF2 gene product, functions as a tumor suppressor gene in schwannoma cells, the functional role of merlin in the tumor microenvironment and the mechanism(s) by which merlin regulates angiogenesis to support schwannoma growth is largely unexplored. Here we report that the expression of semaphorin 3F (SEMA3F) was specifically downregulated in schwannoma cells lacking merlin/NF2. When we reintroduced SEMA3F in schwannoma cells, we observed normalized tumor blood vessels, reduced tumor burden, and extended survival in nude mice bearing merlin-deficient brain tumors. Next, using chemical inhibitors and gene knockdown with RNA interference, we found that merlin regulated expression of SEMA3F through Rho GTPase family member Rac1. This study shows that, in addition to the tumor-suppressing activity of merlin, it also functions to maintain physiological angiogenesis in the nervous system by regulating antiangiogenic factors such as SEMA3F. Restoring the relative balance of proangiogenic and antiangiogenic factors, such as increases in SEMA3F, in schwannoma microenvironment may represent a novel strategy to alleviate the clinical symptoms of NF2-related schwannomas.
PMCID: PMC3306254  PMID: 22431917
20.  Glioblastoma Recurrence after Cediranib Therapy in Patients: Lack of “Rebound” Revascularization as Mode of Escape 
Cancer research  2011;71(1):19-28.
Recurrent glioblastomas (rGBM) invariably relapse after initial response to anti-VEGF therapy. There are two prevailing hypotheses on how these tumors escape antiangiogenic therapy: switch to VEGF-independent angiogenic pathways and vessel co-option. However, direct evidence in rGBM patients is lacking. Thus, we compared molecular, cellular and vascular parameters in autopsy tissues from five rGBM patients who had been treated with the pan-VEGF receptor tyrosine kinase inhibitor cediranib versus seven patients who received no therapy or chemoradiation but no antiangiogenic agents. After cediranib treatment, endothelial proliferation and glomeruloid vessels were decreased, and vessel diameters and perimeters were reduced to levels comparable to the unaffected contralateral brain hemisphere. In addition, tumor endothelial cells expressed molecular markers specific to the blood-brain barrier, indicative of a lack of revascularization despite the discontinuation of therapy. Surprisingly, in cediranib-treated GBM cellular density in the central area of the tumor was lower than in control cases and gradually decreased towards the infiltrating edge, indicative of a change in growth pattern of rGBMs after cediranib treatment, unlike that after chemo-radiation. Finally, cediranib treated GBMs showed high levels of PDGF-C and c-Met expression and infiltration by myeloid cells, which may potentially contribute to resistance to anti-VEGF therapy. In summary, we show that rGBMs switch their growth pattern after anti-VEGF therapy – characterized by lower tumor cellularity in the central area, decreased pseudopalisading necrosis and blood vessels with normal molecular expression and morphology without a second wave of angiogenesis.
doi:10.1158/0008-5472.CAN-10-2602
PMCID: PMC3074948  PMID: 21199795
21.  Recruitment of myeloid but not endothelial precursor cells facilitates tumor re-growth after local irradiation 
Cancer research  2010;70(14):5679-5685.
Tumor neovascularization and growth may be promoted by recruitment of bone marrow-derived cells (BMDCs), which include endothelial precursor cells (EPCs) and “vascular modulatory” myelomonocytic (CD11b+) cells. BMDCs may also drive tumor re-growth after certain chemotherapeutic and vascular disruption treatments. In this study, we evaluated the role of BMDC recruitment in breast and lung carcinoma xenograft models after local irradiation (LI). We depleted the bone marrow by including whole body irradiation (WBI) of 6Gy as part of a total tumor dose of 21Gy, and compared the growth delay with the one achieved after LI of 21Gy. In both models, including WBI induced longer tumor growth delays. Moreover, including WBI increased lung tumor control probability by LI. Exogenous delivery of BMDCs from radiation-naïve donors partially abrogated the WBI effect. Myeloid BMDCs, primarily macrophages, rapidly accumulated in tumors after LI. Intratumoral expression of SDF-1α, a chemokine that promotes tissue retention of BMDCs, was noted 2 days after LI. Conversely, treatment with an inhibitor of SDF-1α receptor CXCR4 (AMD3100) with LI significantly delayed tumor re-growth. However, when administered starting from 5 days post-LI, AMD3100 treatment was ineffective. Lastly, with restorative bone marrow transplantation of Tie2-GFP-labeled BMDC population we observed an increased number of monocytes but not EPCs in tumors that recurred following LI. Our results suggest that an increase in intratumoral SDF-1α triggered by local irradiation recruits myelomonocyte/macrophage which promote tumor re-growth.
doi:10.1158/0008-5472.CAN-09-4446
PMCID: PMC2918387  PMID: 20631066
SDF1alpha; irradiation; tumor; relapse; CXCR4; BMDCs
22.  Pre-metastatic lung “niche”: Is VEGFR1 activation required? 
Cancer research  2010;70(14):5670-5673.
Inflammatory pathways may mediate preparation of the “metastatic soil” in the lungs. Some of these pathways—activation and/or the recruitment of certain inflammatory cells—might depend on vascular endothelial growth factor receptor 1 (VEGFR1) activity. Thus, blocking the activity of VEGFR1 (or the interaction with its ligands) has emerged as a potential anti-metastasis strategy to target not only angiogenesis and cancer cell survival and migration, but also the recruitment of tumor growth-promoting bone marrow-derived cells (BMDCs). However, inhibition of VEGFR1 activity by blocking antibodies or by genetic deletion of the tyrosine kinase domain neither prevented nor changed the rate of spontaneous metastasis formation after surgical removal of primary tumors. Thus, development of VEGFR1-targeted agents should be pursued in selected tumors (e.g., by identifying cancers that depend on VEGFR1 signaling for survival) or in specific combination therapies. Preventing metastasis will likely require identification and blockade of additional or alternative pro-inflammatory pathways that mediate the priming of the metastatic soil and the growth of micro-metastases.
doi:10.1158/0008-5472.CAN-10-0119
PMCID: PMC2919170  PMID: 20587530
23.  Plasma Soluble VEGFR-1 Is a Potential Dual Biomarker of Response and Toxicity for Bevacizumab with Chemoradiation in Locally Advanced Rectal Cancer 
The oncologist  2010;15(6):577-583.
We explored plasma and urinary concentrations of two members of the vascular endothelial growth factor (VEGF) family and their receptors as potential response and toxicity biomarkers of bevacizumab with neoadjuvant chemoradiation in patients with localized rectal cancer. The concentrations of VEGF, placental growth factor (PlGF), soluble VEGF receptor 1 (sVEGFR-1), and sVEGFR-2 were measured in plasma and urine at baseline and during treatment. Pretreatment values and changes over time were analyzed as potential biomarkers of pathological response to treatment as well as for acute toxicity in patients with locally advanced rectal cancer treated prospectively in 2002–2008 with neoadjuvant bevacizumab, 5-fluorouracil, radiation therapy, and surgery in a phase I/II trial. Of all biomarkers, pretreatment plasma sVEGFR-1—an endogenous blocker of VEGF and PlGF, and a factor linked with “vascular normalization”—was associated with both primary tumor regression and the development of adverse events after neoadjuvant bevacizumab and chemoradiation. Based on the findings in this exploratory study, we propose that plasma sVEGFR-1 should be further studied as a potential biomarker to stratify patients in future studies of bevacizumab and/or cytotoxics in the neoadjuvant setting.
doi:10.1634/theoncologist.2010-0029
PMCID: PMC3061828  PMID: 20484123
Bevacizumab; sVEGFR-1; Biomarker; Rectal cancer; Chemoradiation; Toxicity
24.  Benefits of vascular normalization are dose- and time-dependent 
Cancer research  2013;73(23):10.1158/0008-5472.CAN-13-1989.
doi:10.1158/0008-5472.CAN-13-1989
PMCID: PMC3876035  PMID: 24265277
25.  Tumor Microvasculature and Microenvironment: Novel Insights Through Intravital Imaging in Pre-Clinical Models 
Intravital imaging techniques have provided unprecedented insight into tumor microcirculation and microenvironment. For example, these techniques allowed quantitative evaluations of tumor blood vasculature to uncover its abnormal organization, structure and function (e.g., hyper-permeability, heterogeneous and compromised blood flow). Similarly, imaging of functional lymphatics has documented their absence inside tumors. These abnormalities result in elevated interstitial fluid pressure and hinder the delivery of therapeutic agents to tumors. In addition, they induce a hostile microenvironment characterized by hypoxia and acidosis, as documented by intravital imaging. The abnormal microenvironment further lowers the effectiveness of anti-tumor treatments such as radiation therapy and chemotherapy. In addition to these mechanistic insights, intravital imaging may also offer new opportunities to improve therapy. For example, tumor angiogenesis results in immature, dysfunctional vessels—primarily caused by an imbalance in production of pro- and anti-angiogenic factors by the tumors. Restoring the balance of pro- and anti-angiogenic signaling in tumors can “normalize” tumor vasculature and thus, improve its function, as demonstrated by intravital imaging studies in preclinical models and in cancer patients. Administration of cytotoxic therapy during periods of vascular normalization has the potential to enhance treatment efficacy.
doi:10.1111/j.1549-8719.2010.00029.x
PMCID: PMC2859831  PMID: 20374484
intravital microscopy; angiogenesis; lymphangiogenesis; tumor; stromal cells; micro-environment; vascular normalization

Results 1-25 (148)