Influence of an anti-angiogenic treatment on 9L gliosarcoma: oxygenation and response to cytotoxic therapy

Dual effects of radiotherapy on tumor microenvironment and its contribution towards the development of resistance to immunotherapy in gastrointestinal and thoracic cancers

Successful clinical methods for tumor elimination include a combination of surgical resection, radiotherapy, and chemotherapy. Radiotherapy is one of the crucial components of the cancer treatment regimens which allow to extend patient life expectancy. Current cutting-edge radiotherapy research is focused on the identification of methods that should increase cancer cell sensitivity to radiation and activate anti-cancer immunity mechanisms. Radiation treatment activates various cells of the tumor microenvironment (TME) and impacts tumor growth, angiogenesis, and anti-cancer immunity. Radiotherapy was shown to regulate signaling and anti-cancer functions of various TME immune and vasculature cell components, including tumor-associated macrophages, dendritic cells, endothelial cells, cancer-associated fibroblasts (CAFs), natural killers, and other T cell subsets. Dual effects of radiation, including metastasis-promoting effects and activation of oxidative stress, have been detected, suggesting that radiotherapy triggers heterogeneous targets. In this review, we critically discuss the activation of TME and angiogenesis during radiotherapy which is used to strengthen the effects of novel immunotherapy. Intracellular, genetic, and epigenetic mechanisms of signaling and clinical manipulations of immune responses and oxidative stress by radiotherapy are accented. Current findings indicate that radiotherapy should be considered as a supporting instrument for immunotherapy to limit the cancer-promoting effects of TME. To increase cancer-free survival rates, it is recommended to combine personalized radiation therapy methods with TME-targeting drugs, including immune checkpoint inhibitors.

Target-Based Radiosensitization Strategies: Concepts and Companion Animal Model Outlook

External beam radiotherapy is indicated in approximately 50-60% of human cancer patients. The prescribed dose of ionizing radiation that can be delivered to a tumor is determined by the sensitivity of the normal surrounding tissues. Despite dose intensification provided by highly conformal radiotherapy, durable locoregional tumor control remains a clinical barrier for recalcitrant tumor histologies, and contributes to cancer morbidity and mortality. Development of target-based radiosensitization strategies that selectively sensitizes tumor tissue to ionizing radiation is expected to improve radiotherapy efficacy. While exploration of radiosensitization strategies has vastly expanded with technological advances permitting the precise and conformal delivery of radiation, maximal clinical benefit derived from radiotherapy will require complementary discoveries that exploit molecularly-based vulnerabilities of tumor cells, as well as the assessment of investigational radiotherapy strategies in animal models that faithfully recapitulate radiobiologic responses of human cancers. To address these requirements, the purpose of this review is to underscore current and emerging concepts of molecularly targeted radiosensitizing strategies and highlight the utility of companion animal models for improving the predictive value of radiotherapy investigations.

Interfering with Tumor Hypoxia for Radiotherapy Optimization

Hypoxia in solid tumors is an important predictor of treatment resistance and poor clinical outcome. The significance of hypoxia in the development of resistance to radiotherapy has been recognized for decades and the search for hypoxia-targeting, radiosensitizing agents continues. This review summarizes the main hypoxia-related processes relevant for radiotherapy on the subcellular, cellular and tissue level and discusses the significance of hypoxia in radiation oncology, especially with regard to the current shift towards hypofractionated treatment regimens. Furthermore, we discuss the strategies to interfere with hypoxia for radiotherapy optimization, and we highlight novel insights into the molecular pathways involved in hypoxia that might be utilized to increase the efficacy of radiotherapy.

Axitinib in combination with radiotherapy for advanced hepatocellular carcinoma: a phase I clinical trial

BACKGROUND

To investigate maximum tolerated dose (MTD) of axitinib, a selective vascular endothelial growth factor receptor 1-3 inhibitor, in combination with radiotherapy (RT) for advanced hepatocellular carcinoma (HCC).

METHODS

This phase I study followed the rule of traditional 3 + 3 design. Major eligibility included: (1) patients with advanced HCC unsuitable for surgery, radiofrequency ablation or transarterial chemoembolization, or who failed after prior local-regional treatment; (2) failure on sorafenib or no grant for sorafenib from health insurance system. Eligible patients with advanced HCC received axitinib for total 8 weeks during and after RT. Three cohorts with axitinib dose escalation were planned: 1 mg twice daily (level I), 2 mg twice daily (level II) and 3 mg twice daily (level III). The prescribed doses of RT ranged from 37.5 to 67.5 Gy in 15 fractions to liver tumor(s) and were determined based on an upper limit of mean liver dose of 18 Gy (intended isotoxic RT for normal liver). The primary endpoint was MTD of axitinib in combination with RT. The secondary endpoints included overall response rate (ORR), RT in-field response rate, acute and late toxicities, overall survival (OS) and progression free survival (PFS).

RESULTS

Total nine eligible patients received axitinib dose levels of 1 mg twice daily (n = 3), 2 mg twice daily (n = 3) and 3 mg twice daily (n = 3). Dose-limiting toxicity (DLT) did not occur in the 3 cohorts; the MTD was defined as 3 mg twice daily in this study. ORR was 66.7%, including 3 complete responses and 3 partial responses, at 3 months after treatment initiation. With a median follow-up of 16.6 months, median OS was not reached, 1-year OS was 66.7%, and median PFS was 7.4 months.

CONCLUSIONS

Axitinib in combination with RT for advanced HCC was well tolerated with an axitinib MTD of 3 mg twice daily in this study. The outcome analysis should be interpreted with caution due to the small total cohort. Trial registration ClinicalTrials.gov (Identifier: NCT02814461), Registered June 27, 2016-Retrospectively registered, https://clinicaltrials.gov/ct2/show/NCT02814461.

Evaluation of the anti-angiogenic effect of bevacizumab on rat C6 glioma by spectral computed tomography

BACKGROUND

Anti-angiogenic drugs have become a research hotspot in recent years. However, dynamically observing their therapeutic effect at different time points during treatment is a clinical problem.

PURPOSE

To explore the feasibility of the quantitative parameters of spectral computed tomography (CT) in evaluating the anti-angiogenic effect of bevacizumab on rat C6 glioma.

MATERIAL AND METHODS

Twenty-six male Sprague-Dawley rats were used to establish the C6 glioma model. The rats were randomly divided into the experimental group (n = 13) and control group (n = 13). The experimental group was intraperitoneally injected with 0.2 µL/g bevacizumab every day, whereas the control group was injected with the same dose of normal saline every day for one week. Spectral CT scanning was performed on the 4th and 8th days after treatment; meanwhile, the brain tissues were collected by heart perfusion for H&E staining, and VEGF and HIF-1α immunohistochemical staining.

RESULTS

On the 4th and 8th days, significant differences in the 70-keV single-energy CT value, slope of the energy spectrum curve, and iodine concentration were found between the experimental group and the control group. Correlation analysis between immunohistochemistry and quantitative parameters of spectral CT showed that the single energy CT value of 70 keV, slope of the energy spectrum curve, and concentration of iodine were positively correlated with VEGF and HIF-1α at different time points in the experimental group and the control group.

CONCLUSION

Spectral CT multi-parameter imaging can be employed as a new method to evaluate the anti-angiogenic effect of bevacizumab on rat C6 glioma.

Tumor vascular status controls oxygen delivery facilitated by infused polymerized hemoglobins with varying oxygen affinity

Oxygen (O2) delivery facilitated by hemoglobin (Hb)-based O2 carriers (HBOCs) is a promising strategy to increase the effectiveness of chemotherapeutics for treatment of solid tumors. However, the heterogeneous vascular structures present within tumors complicates evaluating the oxygenation potential of HBOCs within the tumor microenvironment. To account for spatial variations in the vasculature and tumor tissue that occur during tumor growth, we used a computational model to develop artificial tumor constructs. With these simulated tumors, we performed a polymerized human hemoglobin (hHb) (PolyhHb) enhanced oxygenation simulation accounting for differences in the physiologic characteristics of human and mouse blood. The results from this model were used to determine the potential effectiveness of different treatment options including a top load (low volume) and exchange (large volume) infusion of a tense quaternary state (T-State) PolyhHb, relaxed quaternary state (R-State) PolyhHb, and a non O2 carrying control. Principal component analysis (PCA) revealed correlations between the different regimes of effectiveness within the different simulated dosage options. In general, we found that infusion of T-State PolyhHb is more likely to decrease tissue hypoxia and modulate the metabolic rate of O2 consumption. Though the developed models are not a definitive descriptor of O2 carrier interaction in tumor capillary networks, we accounted for factors such as non-uniform vascular density and permeability that limit the applicability of O2 carriers during infusion. Finally, we have used these validated computational models to establish potential benchmarks to guide tumor treatment during translation of PolyhHb mediated therapies into clinical applications.

Polymerized human hemoglobin facilitated modulation of tumor oxygenation is dependent on tumor oxygenation status and oxygen affinity of the hemoglobin-based oxygen carrier

Administration of hemoglobin-based oxygen carriers (HBOCs) into the systemic circulation is a potential strategy to relieve solid tumor hypoxia in order to increase the effectiveness of chemotherapeutics. Previous computational analysis indicated that the oxygen (O₂) status of the tumor and HBOC O₂ affinity may play a role in increased O₂ delivery to the tumor. However, no study has experimentally investigated how low- and high-affinity HBOCs would perform in normoxic and hypoxic tumors. In this study, we examined how the HBOC, polymerized human hemoglobin (PolyhHb), in the relaxed (R) or tense (T) quaternary state modulates O₂ delivery to hypoxic (FME) and normoxic (LOX) human melanoma xenografts in a murine window chamber model. We examined microcirculatory fluid flow via video shearing optical microscopy, and O₂ distributions via phosphorescence quenching microscopy. Additionally, we examined how weekly infusion of a 20% top-load dose of PolyhHb influences growth rate, vascularization, and regional blood flow in the FME and LOX tumor xenografts. Infusion of low-affinity T-state PolyhHb led to increased tissue oxygenation, decreased blood flow, decreased tumor growth, and decreased vascularization in hypoxic tumors. However, infusion of both T-state and R-state PolyhHbs led to worse outcomes in normoxic tumors. Of particular concern was the high-affinity R-state PolyhHb, which led to no improvement in hypoxic tumors and significantly worsened outcomes in normoxic tumors. Taken together, the results of this study indicate that the tumor O₂ status is a primary determinant of the potency and outcomes of infused PolyhHb.

Apatinib Combined With Radiotherapy Enhances Antitumor Effects in an In Vivo Nasopharyngeal Carcinoma Model

Vascular endothelial growth factor (VEGF) and its receptor (VEGFR) are highly expressed in nasopharyngeal carcinoma; therefore, blocking the binding of VEGF and VEGFR may be a potential way to treat nasopharyngeal carcinoma. Apatinib inhibits tumor angiogenesis. Previous studies have suggested that treatment with apatinib has an antitumor effect on nasopharyngeal carcinoma. This study will investigate the effect of apatinib combined with radiotherapy. In this study, nude mice injected with CNE-2 nasopharyngeal carcinoma cells were randomly divided into 6 groups. Therapeutic effects were assessed by evaluating tumor inhibition rate, phosphorylation of VEGFR-2, CD31, partial oxygen pressure, and tumor metabolism. We found that the tumor inhibition of mice in the treated groups was better compared to that of the control group. In mice treated with apatinib alone, angiogenesis was prevented, and the tumor tissue partial oxygen pressure was reduced, thereby achieving an antitumor effect. Moreover, the tumor inhibitory effect of combined treatment was stronger than treatment with either apatinib or radiotherapy alone. Compared with monotherapy treatment, combined treatment better resisted angiogenesis. Apatinib combined with radiotherapy to treat nasopharyngeal carcinoma has synergistic effects, which may be related to enhanced antiangiogenesis.

Hyperthermia can alter tumor physiology and improve chemo- and radio-therapy efficacy

Hyperthermia has demonstrated clinical success in improving the efficacy of both chemo- and radio-therapy in solid tumors. Pre-clinical and clinical research studies have demonstrated that targeted hyperthermia can increase tumor blood flow and increase the perfused fraction of the tumor in a temperature and time dependent manner. Changes in tumor blood circulation can produce significant physiological changes including enhanced vascular permeability, increased oxygenation, decreased interstitial fluid pressure, and reestablishment of normal physiological pH conditions. These alterations in tumor physiology can positively impact both small molecule and nanomedicine chemotherapy accumulation and distribution within the tumor, as well as the fraction of the tumor susceptible to radiation therapy. Hyperthermia can trigger drug release from thermosensitive formulations and further improve the accumulation, distribution, and efficacy of chemotherapy.

Interleukin-22 promotes tumor angiogenesis

TH17 cells play important yet complex roles in cancer development and progression. We previously reported that TH17 cells and IL-17 mediate resistance to anti-VEGF therapy by inducing recruitment of immunosuppressive and proangiogenic myeloid cells to the tumor microenvironment. Here, we demonstrate that IL-22, a key effector cytokine expressed by TH17 cells, directly acts on endothelial cells to promote tumor angiogenesis. IL-22 induces endothelial cell proliferation, survival, and chemotaxis in vitro and neovascularization in an ex vivo mouse choroid explant model. Blockade of IL-22, with a neutralizing antibody, significantly inhibits tumor growth associated with reduced microvascular density. No synergistic effect of IL-22 with VEGF was observed. These results identify IL-22 as a potential therapeutic target for blocking tumor angiogenesis.

The quaternary state of polymerized human hemoglobin regulates oxygenation of breast cancer solid tumors: A theoretical and experimental study

A major constraint in the treatment of cancer is inadequate oxygenation of the tumor mass, which can reduce chemotherapeutic efficacy. We hypothesize that polymerized human hemoglobin (PolyhHb) can be transfused into the systemic circulation to increase solid tumor oxygenation, and improve chemotherapeutic outcomes. By locking PolyhHb in the relaxed (R) quaternary state, oxygen (O2) offloading at low O2 tensions (<20 mm Hg) may be increased, while O2 offloading at high O2 tensions (>20 mm Hg) is facilitated with tense (T) state PolyhHb. Therefore, R-state PolyhHb may deliver significantly more O2 to hypoxic tissues. Biophysical parameters of T and R-state PolyhHb were used to populate a modified Krogh tissue cylinder model to assess O2 transport in a tumor. In general, we found that increasing the volume of transfused PolyhHb decreased the apparent viscosity of blood in the arteriole. In addition, we found that PolyhHb transfusion decreased the wall shear stress at large arteriole diameters (>20 μm), but increased wall shear stress for small arteriole diameters (<10 μm). Therefore, transfusion of PolyhHb may lead to elevated O2 delivery at low pO2. In addition, transfusion of R-state PolyhHb may be more effective than T-state PolyhHb for O2 delivery at similar transfusion volumes. Reduction in the apparent viscosity resulting from PolyhHb transfusion may result in significant changes in flow distributions throughout the tumor microcirculatory network. The difference in wall shear stress implies that PolyhHb may have a more significant effect in capillary beds through mechano-transduction. Periodic top-load transfusions of PolyhHb into mice bearing breast tumors confirmed the oxygenation potential of both PolyhHbs via reduced hypoxic volume, vascular density, tumor growth, and increased expression of hypoxia inducible genes. Tissue section analysis demonstrated primary PolyhHb clearance occurred in the liver and spleen indicating a minimal risk for renal damage.

Salmonella inhibits tumor angiogenesis by downregulation of vascular endothelial growth factor

Salmonella is a Gram-negative, facultative anaerobe that is a common cause of host intestinal infections. Salmonella grows under aerobic and anaerobic conditions, and it has been proven capable of inhibiting tumor growth. However, the molecular mechanism by which Salmonella inhibits tumor growth is still unclear. Angiogenesis plays an important role in the development and progression of tumors. We investigated the antitumor effect of Salmonella in a syngeneic murine tumor model. Hypoxia-inducible factor-1 (HIF-1)α plays a significant role in tumor angiogenesis. We examined the molecular mechanism by which Salmonella regulated vascular endothelial growth factor (VEGF), which is an important angiogenic factor. The expression of VEGF in tumor cells was decreased by treatment with Salmonella. The conditioned medium from Salmonella-treated cells inhibited the proliferation of endothelial cells. Salmonella inhibited the expression of HIF-1α as well as downregulated its upstream signal mediator protein kinase B (AKT). Salmonella significantly inhibited tumor growth in vivo, and immunohistochemical studies of the tumors revealed decreased intratumoral microvessel density. These results suggest that Salmonella therapy, which exerts anti-angiogenic activities, represents a promising strategy for the treatment of tumors.

Overcoming key biological barriers to cancer drug delivery and efficacy

Poor delivery efficiency continues to hamper the effectiveness of cancer therapeutics engineered to destroy solid tumors using different strategies such as nanocarriers, targeting agents, and matching treatments to specific genetic mutations. All contemporary systemic anti-cancer agents are dependent upon passive transvascular mechanisms for their delivery into solid tumors. The therapeutic efficacies of our current drug arsenal could be significantly improved with an active delivery strategy. Here, we discuss how drug delivery and therapeutic efficacy are greatly hindered by barriers presented by the vascular endothelial cell layer and by the aberrant nature of tumor blood vessels in general. We describe mechanisms by which molecules cross endothelial cell (EC) barriers in normal tissues and in solid tumors, including paracellular and transcellular pathways that enable passive or active transport. We also discuss specific obstacles to drug delivery that make solid tumors difficult to treat, as well strategies to overcome them and enhance drug penetration. Finally, we describe the caveolae pumping system, a promising active transport alternative to passive drug delivery across the endothelial cell barrier. Each strategy requires further testing to define its therapeutic applicability and clinical utilities.

The clinical application of angiostatic therapy in combination with radiotherapy: past, present, future

Although monotherapy with angiostatic drugs is still far from effective, there is abundant evidence that angiostatic therapy can improve the efficacy of conventional treatments like radiotherapy. This has instigated numerous efforts to optimize and clinically implement the combination of angiostatic drugs with radiation treatment. The results from past and present clinical trials that explored this combination therapy indeed show encouraging results. However, current findings also show that the combination has variable efficacy and is associated with increased toxicity. This indicates that combining radiotherapy with angiostatic drugs not only holds opportunities but also provides several challenges. In the current review, we provide an update of the most recent insights from clinical trials that evaluated the combination of angiostatic drugs with radiation treatment. In addition, we discuss the outstanding questions for future studies in order to improve the clinical benefit of combining angiostatic therapy with radiation therapy.

Combination of stereotactic ablative body radiation with targeted therapies

Recent advances allow safe and effective delivery of ablative doses of radiation with stereotactic precision to tumours, resulting in very high levels of tumour control. Parallel advances in the understanding of tumour biology enable delivery of systemic drugs that selectively antagonise biological pathways in the tumour and surrounding microenvironment. Data is emerging that these treatments have synergistic effects that might further increase therapeutic efficacy, and they are therefore being increasingly used in combination, primarily in metastatic or recurrent disease. In this Review we summarise the biological rationale and clinical data for both sterotactic ablative radiotherapy (SABR) and targeted therapies, and the emerging experience with combination of these treatments. We describe potential pathways of cooperation in both tumour and normal tissue between SABR and targeted drugs, and, because fatal toxicities have been reported, we outline clinical precautions.

Monitoring of tumor response to Cisplatin using optical spectroscopy

INTRODUCTION

Anatomic imaging alone is often inadequate for tuning systemic treatment for individual tumor response. Optically based techniques could potentially contribute to fast and objective response monitoring in personalized cancer therapy. In the present study, we evaluated the feasibility of dual-modality diffuse reflectance spectroscopy-autofluorescence spectroscopy (DRS-AFS) to monitor the effects of systemic treatment in a mouse model for hereditary breast cancer.

METHODS

Brca1(-/-); p53(-/-) mammary tumors were grown in 36 mice, half of which were treated with a single dose of cisplatin. Changes in the tumor physiology and morphology were measured for a period of 1 week using dual-modality DRS-AFS. Liver and muscle tissues were also measured to distinguish tumor-specific alterations from systemic changes. Model-based analyses were used to derive different optical parameters like the scattering and absorption coefficients, as well as sources of intrinsic fluorescence. Histopathologic analysis was performed for cross-validation with trends in optically based parameters.

RESULTS

Treated tumors showed a significant decrease in Mie-scattering slope and Mie-to-total scattering fraction and an increase in both fat volume fraction and tissue oxygenation after 2 days of follow-up. Additionally, significant tumor-specific changes in the fluorescence spectra were seen. These longitudinal trends were consistent with changes observed in the histopathologic analysis, such as vital tumor content and formation of fibrosis.

CONCLUSIONS

This study demonstrates that dual-modality DRS-AFS provides quantitative functional information that corresponds well with the degree of pathologic response. DRS-AFS, in conjunction with other imaging modalities, could be used to optimize systemic cancer treatment on the basis of early individual tumor response.

Assessment of the changes in 9L and C6 glioma pO2 by EPR oximetry as a prognostic indicator of differential response to radiotherapy

Tumor hypoxia impedes the outcome of radiotherapy. As the extent of hypoxia in solid tumors varies during the course of radiotherapy, methods that can provide repeated assessment of tumor pO2 such as EPR oximetry may enhance the efficacy of radiotherapy by scheduling irradiations when the tumors are oxygenated. The repeated measurements of tumor pO2 may also identify responders, and thereby facilitate the design of better treatment plans for nonresponding tumors. We have investigated the temporal changes in the ectopic 9L and C6 glioma pO2 irradiated with single radiation doses less than 10 Gy by EPR oximetry. The 9L and C6 tumors were hypoxic with pO2 of approximately 5-9 mmHg. The pO2 of C6 tumors increased significantly with irradiation of 4.8-9.3 Gy. However, no change in the 9L tumor pO2 was observed. The irradiation of the oxygenated C6 tumors with a second dose of 4.8 Gy resulted in a significant delay in growth compared to hypoxic and 2 Gy × 5 treatment groups. The C6 tumors with an increase in pO2 of greater than 50% from the baseline of irradiation with 4.8 Gy (responders) had a significant tumor growth delay compared to nonresponders. These results indicate that the ectopic 9L and C6 tumors responded differently to radiotherapy. We propose that the repeated measurement of the oxygen levels in the tumors during radiotherapy can be used to identify responders and to design tumor oxygen guided treatment plans to improve the outcome.

Gastrointestinal radiation injury: Symptoms, risk factors and mechanisms

Ionising radiation therapy is a common treatment modality for different types of cancer and its use is expected to increase with advances in screening and early detection of cancer. Radiation injury to the gastrointestinal tract is important factor working against better utility of this important therapeutic modality. Cancer survivors can suffer a wide variety of acute and chronic symptoms following radiotherapy, which significantly reduces their quality of life as well as adding an extra burden to the cost of health care. The accurate diagnosis and treatment of intestinal radiation injury often represents a clinical challenge to practicing physicians in both gastroenterology and oncology. Despite the growing recognition of the problem and some advances in understanding the cellular and molecular mechanisms of radiation injury, relatively little is known about the pathophysiology of gastrointestinal radiation injury or any possible susceptibility factors that could aggravate its severity. The aims of this review are to examine the various clinical manifestations of post-radiation gastrointestinal symptoms, to discuss possible patient and treatment factors implicated in normal gastrointestinal tissue radiosensitivity and to outline different mechanisms of intestinal tissue injury.

Microenvironment and radiation therapy

Dependency on tumor oxygenation is one of the major features of radiation therapy and this has led many radiation biologists and oncologists to focus on tumor hypoxia. The first approach to overcome tumor hypoxia was to improve tumor oxygenation by increasing oxygen delivery and a subsequent approach was the use of radiosensitizers in combination with radiation therapy. Clinical use of some of these approaches was promising, but they are not widely used due to several limitations. Hypoxia-inducible factor 1 (HIF-1) is a transcription factor that is activated by hypoxia and induces the expression of various genes related to the adaptation of cellular metabolism to hypoxia, invasion and metastasis of cancer cells and angiogenesis, and so forth. HIF-1 is a potent target to enhance the therapeutic effects of radiation therapy. Another approach is antiangiogenic therapy. The combination with radiation therapy is promising, but several factors including surrogate markers, timing and duration, and so forth have to be optimized before introducing it into clinics. In this review, we examined how the tumor microenvironment influences the effects of radiation and how we can enhance the antitumor effects of radiation therapy by modifying the tumor microenvironment.

Tumor reoxygenation following administration of Mitogen-Activated Protein Kinase inhibitors: a rationale for combination with radiation therapy

BACKGROUND AND PURPOSE

The relevance of Mitogen Activated Protein Kinase (MAPK) inhibitors as co-treatments for radiation therapy is investigated, with special focus on a potential link between the MAPK pathway and tumor hypoxia, which is a critical determinant for response to therapy.

MATERIALS AND METHODS

The effects of two MAPK inhibitors, Sorafenib and PD0325901, were monitored daily using in vivo EPR (Electron Paramagnetic Resonance) oximetry in FSaII and TLT tumor models in order to identify a window of reoxygenation, during which tumor blood flow, oxygen consumption and radiation sensitivity were assessed.

RESULTS

Reoxygenation was shown after two days of treatments with Sorafenib or PD0325901 in two tumor models, which was further successfully exploited with Sorafenib for improving the radiation response of FSaII tumors by a factor of 1.5. The increase in tumor oxygenation was shown to be the result of two major factors: (i) an increase in blood flow for Sorafenib, that might be linked to its anti-angiogenic effect (vascular normalization), and (ii) a decrease in oxygen consumption for Sorafenib and PD0325901, due to an alteration of the mitochondrial activity.

CONCLUSION

We evidenced tumor reoxygenation in vivo following MAPK inhibition and suggest a rationale for the combination of radiation therapy with Sorafenib.

Effect of an angiogenesis inhibitor on hepatic tumor perfusion and the implications for adjuvant cytotoxic therapy

PURPOSE

To determine whether dynamic contrast material-enhanced (DCE) computed tomography (CT) can help identify hepatic tumor perfusion response to vascular remodeling induced by antiangiogenesis treatment in a rabbit model.

MATERIALS AND METHODS

The study was approved by the Animal Use Subcommittee of the University Council on Animal Care. DCE CT hepatic perfusion measurements were performed in the livers of 20 rabbits implanted with VX2 carcinoma. Vascular remodeling was induced with thalidomide dissolved in dimethyl sulfoxide and sterile water, starting at a tumor diameter of 0.7 cm±0.1 and continuing until metastatic lung nodules were observed. The control group (n=8) was given an equivalent volume of the vehicle. The therapy group was subdivided into animals that survived for more than 24 days without lung metastasis (responder group, n=5) or those that survived for less than 24 days (nonresponder group, n=7). Data were analyzed with the Kruskal-Wallis or Friedman rank test and reported as medians and interquartile ranges.

RESULTS

DCE CT depicted differential perfusion change within the therapy group after treatment. By day 4, hepatic blood volume (HBV) in the responder group decreased by 29.2% (-32.5% to -11.8%) relative to that before treatment and was significantly different from that in the nonresponder (P=.048) and control (P=.011) groups, where HBV remained stable. By day 8, hepatic artery blood flow decreased by 50.0% (-59.08% to -21.05%) relative to that before treatment in the responder group and was significantly different from that in the nonresponder and control groups (P=.030 for both), which remained stable at -3.5% (-8.5% to 28.7%, P=.50) and -10.0% (-33.8% to 10.4%, P=.48), respectively.

CONCLUSION

DCE CT can help differentiate responders from nonresponders by their early differential perfusion response to antiangiogenesis therapy.

A phase 2 study of bevacizumab with cisplatin plus intensity-modulated radiation therapy for stage III/IVB head and neck squamous cell cancer

BACKGROUND

For patients with stage III through IVB head and neck squamous cell carcinoma (HNSCC), concurrent high-dose cisplatin plus radiation therapy is a widely accepted standard of care. HNSCC tumors that express high levels of vascular endothelial growth factor have been associated with a worse prognosis, and bevacizumab may sensitize tumors to cisplatin and radiation.

METHODS

Planned treatment consisted of definitive intensity-modulated radiation therapy (IMRT) (total, 70 grays) with concurrent cisplatin (50 mg/m(2) on days 1, 2, 22, 23, 43, and 44) and bevacizumab (15 mg/kg on days 1, 22, and 43). The primary endpoint was 2-year progression-free survival (PFS), and overall survival (OS) was a secondary endpoint.

RESULTS

Forty-two previously untreated patients (34 men and 8 women; median age, 55 years; range, 27-75 years) with stage III through IV HNSCC without distant metastasis (oropharyngeal carcinoma, 39 patients; laryngeal carcinoma, 3 patients) were treated. Human papillomavirus (HPV) status by was determined by in situ hybridization (HPV positive, 16 patients; HPV negative, 14 patients, unknown HPV status, 12 patients). The toxicities (determined according to version 3.0 of Common Terminology Criteria for Adverse Events Common) that were experienced by all patients (any grade) were mucositis, lymphopenia, leukopenia, throat pain, fatigue, and anemia. There were 2 treatment-related deaths, including 1 sudden death and 1 death from aspiration pneumonia. The median follow-up was approximately 31.8 months (range, <3 to 51 months). The 2-year PFS rate was 75.9% (95% confidence interval, 63.9%-90.1%), and the 2-year OS rate was 88% (95% confidence interval, 78.6%-98.4%). Among 32 patients for whom post-treatment Head and Neck Performance Status Scores were obtained (median, 5.6 months after completing radiation therapy), scores of 100 for eating, speech, and diet, respectively, were recorded among 75%, 84%, and 50% of patients.

BACKGROUND

The addition of bevacizumab to high-dose cisplatin plus IMRT did not appear to increase toxicity to unacceptable levels among patients with HNSCC, and the efficacy results were encouraging.

Honokiol crosses BBB and BCSFB, and inhibits brain tumor growth in rat 9L intracerebral gliosarcoma model and human U251 xenograft glioma model

Background

Gliosarcoma is one of the most common malignant brain tumors, and anti-angiogenesis is a promising approach for the treatment of gliosarcoma. However, chemotherapy is obstructed by the physical obstacle formed by the blood-brain barrier (BBB) and blood-cerebrospinal fluid barrier (BCSFB). Honokiol has been known to possess potent activities in the central nervous system diseases, and anti-angiogenic and anti-tumor properties. Here, we hypothesized that honokiol could cross the BBB and BCSFB for the treatment of gliosarcoma.

Methodologies

We first evaluated the abilities of honokiol to cross the BBB and BCSFB by measuring the penetration of honokiol into brain and blood-cerebrospinal fluid, and compared the honokiol amount taken up by brain with that by other tissues. Then we investigated the effect of honokiol on the growth inhibition of rat 9L gliosarcoma cells and human U251 glioma cells in vitro. Finally we established rat 9L intracerebral gliosarcoma model in Fisher 344 rats and human U251 xenograft glioma model in nude mice to investigate the anti-tumor activity.

Principal Findings

We showed for the first time that honokiol could effectively cross BBB and BCSFB. The ratios of brain/plasma concentration were respectively 1.29, 2.54, 2.56 and 2.72 at 5, 30, 60 and 120 min. And about 10% of honokiol in plasma crossed BCSFB into cerebrospinal fluid (CSF). In vitro, honokiol produced dose-dependent inhibition of the growth of rat 9L gliosarcoma cells and human U251 glioma cells with IC₅₀ of 15.61 µg/mL and 16.38 µg/mL, respectively. In vivo, treatment with 20 mg/kg body weight of honokiol (honokiol was given twice per week for 3 weeks by intravenous injection) resulted in significant reduction of tumor volume (112.70±10.16 mm³) compared with vehicle group (238.63±19.69 mm³, P = 0.000), with 52.77% inhibiting rate in rat 9L intracerebral gliosarcoma model, and (1450.83±348.36 mm³) compared with vehicle group (2914.17±780.52 mm³, P = 0.002), with 50.21% inhibiting rate in human U251 xenograft glioma model. Honokiol also significantly improved the survival over vehicle group in the two models (P<0.05).

Conclusions/Significance

This study provided the first evidence that honokiol could effectively cross BBB and BCSFB and inhibit brain tumor growth in rat 9L intracerebral gliosarcoma model and human U251 xenograft glioma model. It suggested a significant strategy for offering a potential new therapy for the treatment of gliosarcoma.

Differential effect of intraperitoneal albendazole and paclitaxel on ascites formation and expression of vascular endothelial growth factor in ovarian cancer cell-bearing athymic nude mice

OBJECTIVES

The purposes of our study were to evaluate the effect of intraperitoneal albendazole on tumor growth, ascites formation, and vascular endothelial growth factor (VEGF) mRNA expression, and to assess the synergistic effect of paclitaxel in OVCAR-3-bearing nude mice.

METHODS

In all, 4 groups of mice were injected intraperitoneally with weekly albendazole (450 mg/kg per week), paclitaxel (30 mg/kg per week), albendazole plus paclitaxel, or normal saline for 4 weeks.

RESULTS

Ascitic fluid accumulation (2.47, 2.65, 2.88, and 5.90 mL, respectively) and in ascitic VEGF levels were significantly reduced in the 3 treatment groups compared to the control group (170.83, 229.16, 267, and 1625 pg/mL, respectively). However, complete tumor suppression was more prominent in the paclitaxel group, and VEGF mRNA expression was more strongly inhibited in the albendazole group (P < .05). No synergistic effect of albendazole and paclitaxel was observed.

CONCLUSION

We demonstrated a differential effect of albendazole and paclitaxel in a xenograft model of ovarian carcinoma; albendazole suppressed ascites formation by inhibiting VEGF secretion, and paclitaxel exerted its effects by direct cytotoxicity.

Combination of vascular endothelial growth factor antisense oligonucleotide therapy and radiotherapy increases the curative effects against maxillofacial VX2 tumors in rabbits

PURPOSE

To study the effects of combination of vascular endothelial growth factor (VEGF) antisense oligonucleotide therapy and radiotherapy on maxillofacial VX2 tumors in rabbits.

METHODS

We used 24 New Zealand white rabbits as a model to induce maxillofacial VX2 tumor. The rabbits were randomly divided into the following 4 groups: radiotherapy group (group A), treated with 16 Gy of radiotherapy; VEGF antisense oligonucleotide treatment group (group B), treated with an injection of 150 μg of VEGF antisense oligonucleotide into the local tumor; VEGF antisense oligonucleotide combined with radiotherapy group (group C), treated with an injection of 150 μg of VEGF antisense oligonucleotide into the local tumor immediately after 16 Gy of radiotherapy; and control group (group D), treated with an injection of 300 μl 5% aqueous glucose solution into the local tumor. On days 3 and 14 after treatment, dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) was performed to calculate maximal enhancement ratio (MER), slope of enhancement (SLE), and tumor volume change. Rabbits were killed on day 14 to obtain samples for pathological examination and immunohistochemical staining for VEGF.

RESULTS

In group C, tumor volume was significantly reduced on day 14 after treatment, and the difference was statistically different as compared to that before treatment, on day 3 after treatment and other groups (P < 0.01). Values of both MER and SLE after treatment were significantly lower than the values before treatment (P < 0.05). Pathological specimen revealed tumor cell edema, bleeding, necrosis, vascular wall thickening and occlusion, and decreased VEGF expression. The immunohistochemical score (IHS) of group C was significantly different from groups A and D respectively (P < 0.05).

CONCLUSION

Injecting the tumor with VEGF antisense oligonucleotide immediately after radiotherapy can enhance the curative effect on rabbit maxillofacial VX2 tumor, and DCE-MRI can serve as a reliable technique for in vivo monitoring.

Targeting angiogenesis in childhood sarcomas

Angiogenesis and vasculogenesis constitute two processes in the formation of new blood vessels and are essential for progression of solid tumors. Consequently, targeting angiogenesis, and to a lesser extent vasculogenesis, has become a major focus in cancer drug development. Angiogenesis inhibitors are now being tested in pediatric populations whereas inhibitors of vasculogenesis are in an earlier stage of development. Despite the initial enthusiasm for targeting angiogenesis for treatment of cancer, clinical trials have shown only incremental increases in survival, and agents have been largely cytostatic rather than inducing tumor regressions. Consequently, the role of such therapeutic approaches in the context of curative intent for childhood sarcomas is less clear. Here we review the literature on blood vessel formation in sarcomas with a focus on pediatric sarcomas and developments in targeting angiogenesis for treatment of these rare cancers.

Radiation, chemotherapy and biological therapy in the curative treatment of locally advanced rectal cancer

OBJECTIVE

To review the published evidence relating to the use of radiotherapy (RT), chemotherapy and biological therapy as adjuncts to surgery in the curative treatment of rectal cancer.

METHODS

Searches were carried out of the MEDLINE and CANCERLIT databases together with conference abstracts from key meetings including the American Society of Clinical Oncology Annual Meeting and Gastrointestinal Cancers Symposium and the ECCO/ESMO Multidisciplinary Congress.

RESULTS

RT reduces local pelvic recurrence when used as an adjunct to surgery, even when this is performed optimally by total mesorectal excision (TME). RT is usually given as short-course preoperative radiotherapy (SCPRT) followed by immediate surgery which produces no or very little downstaging or long-course concurrent chemoradiation (CRT) followed by a 6-8 week gap prior to surgery which produces significant downstaging. The prognostic importance of achieving a clear histological circumferential resection margin is now well recognised and pathological assessment of the quality of surgery can predict long-term outcomes. Internationally there is considerable heterogeneity in the staging modalities and criteria used in deciding which approach might be used, in the reporting of histological results and in RT parameters (time/dose/fractionation/volume). Attempts to increase the potency of CRT have included the addition of concurrent chemotherapeutic and biological agents to the standard fluoropyrimidine although there is little randomised data and none with regard to long-term survival outcomes. Neither SCPRT nor downstaging CRT have been shown to reduce the rate of subsequent distant metastatic relapse which remains a significant clinical problem. The potential additional benefit of neoadjuvant or adjuvant chemotherapy in addition to SCPRT or long-course CRT remains ill-defined. Late morbidity can include bowel and sexual dysfunction, pelvic fractures and second malignancies with considerably more being known in relation to SCPRT than long-course CRT.

CONCLUSIONS

Improvements in imaging, pathology and surgical technique combined with multimodality treatment using RT and chemotherapy are leading to continuing improvements in the long term outcome for patients with rectal cancer although much remains to be learnt regarding the optimum strategy for use of these in different clinical contexts and their relationship to long-term morbidity.

Inhibition of experimental lung metastasis by systemic lentiviral delivery of kallistatin

Background

Angiogenesis plays an important role in the development and progression of tumors. Kallistatin exerts anti-angiogenic and anti-inflammatory activities that may be effective in inhibiting tumor metastasis. We investigated the antitumor effect of lentivirus-mediated kallistatin gene transfer in a syngeneic murine tumor model.

Methods

Lentiviral vector encoding kallistatin (LV-Kallistatin) was constructed. The expression of kallistatin was verified by enzyme-linked immunosorbent assay (ELISA), and the bioactivity of kallistatin was determined by using cell proliferation, migration, and invasion assays. In addition, antitumor effects of LV-Kallistatin were evaluated by the intravenous injection of virus into tumor-bearing mice.

Results

The conditioned medium from LV-Kallistatin-treated cells inhibited the migration and proliferation of endothelial cells. Meanwhile, it also reduced the migration and invasion of tumor cells. In the experimental lung metastatic model, tumor-bearing mice receiving LV-Kallistatin had lower tumor nodules and longer survival than those receiving control virus or saline. Moreover, the microvessel densities, the levels of vascular endothelial growth factor (VEGF), tumor necrosis factor (TNF)-α, and nuclear factor κB (NF-κB) transcriptional activity were reduced in the LV-Kallistatin-treated mice.

Conclusion

Results of this study showed that systemic administration of lentiviral vectors encoding kallistatin inhibited the growth of metastatic tumor and prolonged the survival of tumor-bearing mice. These results suggest that gene therapy using lentiviruses carrying the kallistatin gene, which exerts anti-angiogenic and anti-inflammatory activities, represents a promising strategy for the treatment of lung cancer.

Antiangiogenics and radiotherapy

Antiangiogenic therapies are one of the fore-runners of the new generation of anticancer drugs aimed at tumour-specific molecular targets. Up until the beginning of this century, the general opinion was that targeted agents should show antitumour activity when used as single agents. However, it has now become clear that much greater improvements in therapeutic activity may be achieved by combining the novel agents with conventional cytotoxic therapies already in use in the clinic. Radiotherapy is currently used to treat half of all cancer patients at some stage in their therapy, although the development of radioresistance is an ongoing problem. It is therefore reasonable to expect that any novel molecularly-targeted agent which reaches the clinic will be used in combination with radiotherapy. The rationale for combining antiangiogenics in particular with radiotherapy exists, as radiotherapy has been shown to kill proliferating endothelial cells, suggesting that inhibiting angiogenesis may sensitise endothelial cells to the effects of radiation. Furthermore, targeting the vasculature may paradoxically increase oxygenation within tumours, thereby enhancing radiotherapy efficacy. In this review we present an update on the use of antiangiogenic methods in combination with radiotherapy.

Using optical spectroscopy to longitudinally monitor physiological changes within solid tumors

The feasibility of using quantitative diffuse reflectance spectroscopy to longitudinally monitor physiological response to cancer therapy was evaluated in a preclinical model. This study included two groups of nude mice bearing 4T1 flank tumors (N = 50), half of which were treated with a maximum tolerated dose of doxorubicin (DOX). Diffuse reflectance spectra were collected from tumors during a period of 2 weeks using a fiber-optic probe coupled to a spectrometer. These spectra were quantified using an inverse scalable Monte Carlo model of light transport in tissue to extract the concentrations of oxygenated, deoxygenated hemoglobin (dHb), and a wavelength mean reduced scattering coefficient (<micro(s)'>). The tumor growth rates of the treated and control groups were nearly identical, as were changes in the scattering parameter <micro(s)'> during this time frame. However, tumors treated with DOX showed a transient but significant increase in blood oxygen saturation. A comparison between the optically derived and immunohistochemical end points in a subset of the 50 animals showed that the temporal kinetics of dHb concentration and <micro(s)'> were highly concordant with those of hypoxic and necrotic fractions, respectively. In conclusion, optical methods could function as a "screening" technology in longitudinal studies of small animal tumor models to accelerate development and testing of new anticancer drugs. This technique could isolate specific landmark time points at which more expensive and sophisticated imaging methods or immunohistochemistry could be performed.

Tissue pO2 of orthotopic 9L and C6 gliomas and tumor-specific response to radiotherapy and hyperoxygenation

PURPOSE

Tumor hypoxia is a well-known therapeutic problem; however, a lack of methods for repeated measurements of glioma partial pressure of oxygen (pO(2)) limits the ability to optimize the therapeutic approaches. We report the effects of 9.3 Gy of radiation and carbogen inhalation on orthotopic 9L and C6 gliomas and on the contralateral brain pO(2) in rats using a new and potentially widely useful method, multisite in vivo electron paramagnetic resonance oximetry.

METHODS AND MATERIALS

Intracerebral 9L and C6 tumors were established in the left hemisphere of syngeneic rats, and electron paramagnetic resonance oximetry was successfully used for repeated tissue pO(2) measurements after 9.3 Gy of radiation and during carbogen breathing for 5 consecutive days.

RESULTS

Intracerebral 9L gliomas had a pO(2) of 30-32 mm Hg and C6 gliomas were relatively hypoxic, with a pO(2) of 12-14 mm Hg (p < 0.05). The tissue pO(2) of the contralateral brain was 40-45 mm Hg in rats with either 9L or C6 gliomas. Irradiation resulted in a significant increase in pO(2) of the 9L gliomas only. A significant increase in the pO(2) of the 9L and C6 gliomas was observed in rats breathing carbogen, but this effect decreased during 5 days of repeated experiments in the 9L gliomas.

CONCLUSION

These results highlight the tumor-specific effect of radiation (9.3.Gy) on tissue pO(2) and the different responses to carbogen inhalation. The ability of electron paramagnetic resonance oximetry to provide direct repeated measurements of tissue pO(2) could have a vital role in understanding the dynamics of hypoxia during therapy that could then be optimized by scheduling doses at times of improved tumor oxygenation.

Process in the mechanisms of endostatin combined with radiotherapy

Endostatin has been demonstrated to represent a promising novel medicine to treat malignant tumors, and it may be more effective when combined with conventional treatment. Meanwhile, a promising area of research in radiation oncology is the integration of molecular targeting agents to improve the effectiveness of radiotherapy (RT) in the control of primary tumor. Antiangiogenic agents are one such class of targeted therapies and have shown promise in both laboratory and clinical experiments. Endostatin in combination with RT has feasibility; but it also has lots of problems. Further understanding of the mechanisms is needed.

In vivo/ex vivo and in situ assays used in cancer research: a brief review

Predicting whether a potential new anticancer agent will have a positive therapeutic index in patients remains a challenge. This brief review provides examples of preclinical in vivo/ex vivo and in situ assays used to assess the therapeutic potential of experimental anticancer therapeutics. Excision assays involving removal of tumor, bone marrow, and other tissues from the host after treatment to determine the effects of therapy in ex vivo assays are important preclinical tools. The survival of malignant cells from tumors treated in vivo and then excised is often determined by colony formation (CFU) in culture. When mice bearing in vivo alkylating agent-resistant tumors were treated with anticancer drugs such as cyclophosphamide, the survival pattern of bone marrow granulocyte-macrophage-colony forming units (CFU-GM) paralleled tumor cell survival. When TNP-470 and minocycline, an antiangiogenic combination, were added to treatment with cytotoxic anticancer therapies, tumor response markedly increased. TNP-470/minocycline-treated mice had higher tissue drug levels than did mice treated with the drug alone. Enzastaurin, an antiangiogenic protein kinase Cbeta inhibitor, treatment decreased intratumoral vessels to one half to one quarter of controls. Simultaneous and sequential treatment regimens with enzastaurin and BCNU delayed tumor growth and increased lifespan in mice bearing subcutaneous or intracranial human T98G glioblastoma multiforme. Both TNP-470 and enzastaurin have undergone clinical trials. Enzastaurin is currently in Phase III clinical trials.

In vivo efficacy of marimastat and chemoradiation in head and neck cancer xenografts

OBJECTIVE

To assess the effect of combining a synthetic matrix metalloprotease inhibitor and chemoradiation therapy on tumor growth in a murine model of head and neck squamous-cell carcinoma (SCC).

METHODS

Athymic, nude mice bearing SCC-1 xenografts were used to comprise 4 treatment groups: (1) control receiving vehicle alone, (2) marimastat alone, (3) cisplatin + radiation in combination and (4) marimastat + cisplatin + radiation in combination. The marimastat was administered at a dose of 8.7 mg/kg/day over a 14-day period via a subcutaneous osmotic pump. The control group received vehicle only via a subcutaneous osmotic pump. Radiotherapy was given in 4 fractions of 8 Gy divided over days 8, 12, 16 and 20 with 4 intraperitoneal doses of cisplatin (3 mg/kg) 1 h before each fraction of radiation.

RESULTS

Animals receiving triple treatment had delayed growth, measured as lengthened tumor doubling time, compared to the cisplatin + radiation combination (p = 0.03). Also, compared to control, the triple-treatment group (p = 0.005) had delayed growth in terms of doubling time. Factor VIII immunohistochemistry to assess microvessel density did not demonstrate a reduction in neovascularization between the triple-treatment and cisplatin + radiation combination groups. Statistical analysis failed to demonstrate any significant difference among groups.

CONCLUSIONS

Chemoradiation + marimastat therapy had delayed tumor growth, compared to the chemoradiation alone. Based on these results, marimastat may work in combination with chemotherapy and radiation to inhibit tumor growth.

Effect of dalteparin and radiation on survival and thromboembolic events in glioblastoma multiforme: a phase II ECOG trial

Laboratory and clinical studies support the concept that heparins, particularly the low molecular component, may serve as an inhibitor of angiogenesis, providing anti-neoplastic effects. Further, treatment with low molecular weight heparin (LMWH) may provide prophylaxis for thromboembolic events (TEE), in glioblastoma (GBM) patients. Dalteparin (5,000 U sub-Q daily) was given with and after conventional radiotherapy to newly diagnosed GBM patients. Forty-five patients were accrued between 5/02 and 9/04; 3 were ineligible. At time of progression, patients could continue dalteparin in addition to standard regimens. Pretreatment characteristics included: median age 61 (range 26-78); ECOG Performance status: 0 = 38%, 1 = 57%, 2 = 5%; gross total resection 45%. There were no grade 3/4 bleeding or thrombocytopenic events, and no TEE occurred while on dalteparin. Median time on dalteparin was 6.3 months, median time to progression was 3.9 months; median survival was 11.9 months. There was no significant improvement in survival when compared to the RTOG GBM database (with various radiation/drug doublets including BCNU) using recursive partitioning analysis. Historically the incidence of TEE in GBM patients is approximately 30%. As this study suggests dalteparin reduces the incidence of TEE, and does not have significant overlapping toxicities with most other drugs; its testing in a combined modality approach with other medications may be warranted in future trials.

Combined anti-proliferative and anti-angiogenic strategies for cancer

BACKGROUND

In recent years, anti-angiogenic treatments have been shown to synergize with traditional chemotherapeutic and radiotherapeutic regimens. Combining anti-angiogenesis with targeted anti-proliferative agents might also be synergistic. Several lines of evidence point to the validity of this approach, and preliminary results of ongoing and recent studies support it.

OBJECTIVE

The background and current status of anti-angiogenic and anti-proliferative treatments will be summarized, as well as the evidence supporting and antagonizing their combined use in the clinic.

METHODS

Relevant literature was reviewed using PubMed search, and recent major conference proceedings and other relevant data were searched through internet publications.

RESULTS/CONCLUSION

Combining anti-angiogenic and anti-proliferative treatments seems a promising approach, although not in all clinical circumstances.

Ionizing radiation antagonizes tumor hypoxia induced by antiangiogenic treatment

PURPOSE

The combined treatment modality of ionizing radiation with inhibitors of angiogenesis is effective despite the supposition that inhibition of angiogenesis might increase tumor hypoxia and thereby negatively affect radiation sensitivity. To directly assess this still controversial issue, we analyzed treatment-dependent alterations of tumor oxygenation in response to inhibition of angiogenesis alone, ionizing radiation, and combined treatment.

EXPERIMENTAL DESIGN

Serial measurements with high-resolution [18F]fluoromisonidazole positron emission tomography and immunohistochemical detection of the endogenous hypoxia marker glucose transporter-1 were done to determine tumor hypoxia in a murine mammary carcinoma allograft model.

RESULTS

Inhibition of angiogenesis with the clinically relevant vascular endothelial growth factor receptor tyrosine kinase inhibitor PTK787/ZK222584 reduced microvessel density but had only minimal effects on tumor growth, tumor cell apoptosis, and proliferation. However, PTK787/ZK222584 treatment increased overall and local tumor hypoxia as revealed by extended expression of the hypoxia marker glucose transporter-1 and increased uptake of [18F]fluoromisonidazole. Fractionated irradiation induced a strong growth delay, which was associated with enhanced apoptosis and reduced proliferation of tumor cells but only minor effects on microvessel density and allograft oxygenation. Combined treatment with fractionated irradiation resulted in extended tumor growth delay and tumor cell apoptosis but no increase in tumor hypoxia.

CONCLUSIONS

These results show that irradiation antagonizes the increase of hypoxia by vascular endothelial growth factor receptor tyrosine kinase inhibition and abrogates the potential negative effect on tumor hypoxia. Thus, the risk of treatment-induced hypoxia by inhibitors of angiogenesis exists but is kept minimal when combined with a cytotoxic treatment modality.

Hypoxia modulation and radiosensitization by the novel dual EGFR and VEGFR inhibitor AEE788 in spontaneous and related allograft tumor models

Concomitant inhibition of ErbB1/2- and VEGF receptor-signaling synergizes when used in combination with DNA-damaging agents. Here, we investigated for the first time the combined treatment modality of the novel dual specific receptor tyrosine kinase inhibitor AEE788 with ionizing radiation and analyzed treatment-induced end points in situ as indicators for a potential sensitizing mechanism. Furthermore, we assessed tumor hypoxia in response to different antiangiogenic and antiproliferative treatment modalities. The combined treatment effect was investigated in a spontaneously growing mammary carcinoma model and against Her-2/neu-overexpressing mammary carcinoma allografts. In tumor allografts derived from murine mammary carcinoma cells of mouse mammary tumor virus/c-neu transgenic mice, a minimal treatment regimen with AEE788 and fractionated irradiation resulted in an at least additive tumor response. Treatment response in the corresponding spontaneous tumor model strongly exceeded the response induced in the isogenic allografts. Treatment-induced changes of tumor proliferation, apoptosis, and microvessel density were similar in the two tumor models. Treatment with AEE788 alone or in combination with IR strongly improved tumor oxygenation in both tumor models as determined by the detection of endogenous and exogenous markers of tumor hypoxia. Specific inhibition of the VEGF-receptor tyrosine kinase versus Erb1/2-receptor tyrosine kinase indicated that it is the antiproliferative and not the antiangiogenic potency of AEE788 that mediates the hypoxia-reducing effect of this dual kinase-specific inhibitor. Overall, we show that concomitant inhibition of ErbB- and VEGF-receptor signaling by AEE788, in combination with ionizing radiation, is a promising treatment approach, especially in hypoxic, oncogenic ErbB-driven tumors.

Simultaneous application of the vascular endothelial growth factor (VEGF) receptor inhibitor PTK787/ZK 222584 and ionizing radiation does not further reduce the growth of canine oral melanoma xenografts in nude mice

PTK787/ZK 222584 is an inhibitor of the vascular endothelial growth factor (VEGF) receptor tyrosine kinases. In this study, the effectiveness of PTK787/ZK 222584 and radiation on canine oral melanoma xenografts was assessed. Xenografts were treated with radiotherapy (4x6Gy), or with PTK787/ZK 222584, or with a combination of both. Treatment efficacy was assessed using a tumour growth delay assay, serial power Doppler and pO(2) measurements during and after therapy. There was a significant growth delay for the group treated with radiation alone and for the combined treatment group. However, tumour growth delay was similar in both groups. Tumours were hypoxic before irradiation and no significant re-oxygenation occurred during therapy. In all tumours, vascularity and perfusion were significantly lower at the end of the study but no significant differences in perfusion, vascularity and oxygenation status were observed between and within treatment groups. The combination of PTK787/ZK 222584 and radiotherapy did not perform better than radiotherapy alone in this model.

Vascular damaging agents

To provide a comprehensive overview on vascular targeting agents and the application of radiobiological principles in pre-clinical and clinical studies, we completed a comprehensive review of published medical studies on vascular targeting agents using Pub Med. Vascular targeting agents are now divided into vascular disrupting agents (VDAs), which target the pre-existing tumour vasculature, and angiogenesis inhibitors (AIs), which prevent the formation of new blood vessels. Modest success has been seen when VDAs and AIs are used as single agents and therefore combination therapies that can work in a complimentary and synergistic manner, targeting both the tumour cells and endothelial cells, are needed. Radiobiological principles have been used to increase our understanding of these agents, and can explain the increased efficacy of combination treatments. In particular, the alteration of the tumour microenvironment by AIs and VDAs can lead to enhanced efficacy when combined with chemotherapy or radiotherapy, with phase II/III trials showing encouraging results. The optimal use and scheduling of AIs and VDAs remains to be determined. Further understanding of the mechanisms of action of these potentially very exciting anti-neoplastic agents is urgently required.

Pathophysiologic Effects of Vascular-Targeting Agents and the Implications for Combination with Conventional Therapies

A functional vascular supply is critical for the continued growth and development of solid tumors. It also plays a major role in metastatic spread of tumor cells. This importance has led to the concept of targeting the vasculature of the tumor as a form of cancer therapy. Two major types of vascular-targeting agent (VTA) have now emerged: those that prevent the angiogenic development of the neovasculature of the tumor and those that specifically damage the already established tumor vascular supply. When used alone neither approach readily leads to tumor control, and so, for VTAs to be most successful in the clinic they will need to be combined with more conventional therapies. However, by affecting the tumor vascular supply, these VTAs should induce pathophysiologic changes in variables, such as blood flow, pH, and oxygenation. Such changes could have negative or positive influences on the tumor response to more conventional therapies. This review aims to discuss the pathophysiologic changes induced by VTAs and the implications of these effects on the potential use of VTAs in combined modality therapy.

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.

Vascular endothelial growth factor immunoneutralization in combination with cisplatin reduces EAC tumor growth

In the present study, we evaluated the effects of a neutralizing anti-Vascular Endothelial Growth Factor (VEGF) polyclonal antibody on murine EAC tumor growth both in vitro and in vivo. Furthermore, we investigated if in the presence of effective VEGF blockade, a conventional chemotherapeutic drug Cisplatin could be effective, and if so would there be an additive effect of the combination regimen. An in vitro cell proliferation assay using MTT kit showed that VEGF antibody alone inhibited proliferation of EAC cells significantly in all the three time intervals (p<0.05). But cisplatin treatment in combination with VEGF antibody resulted in highly significant inhibition (p<0.001) of cell proliferation. Apoptosis assay by FACS analysis showed that VEGF antibody-cisplatin combination treatment induced apoptosis in cultured EAC cells. Intraperitoneal administration of VEGF antibody (100 mug/dose) and cisplatin (0.5 mg/kg/dose) combination was observed to be more effective in reducing tumor burden and increasing life span when compared to VEGF antibody or cisplatin treatment alone in EAC solid tumor bearing mice. In EAC ascites tumor model, all the three types of treatment inhibited tumor burden and increased life span, but the inhibition was less compared to EAC solid tumor bearing mice. VEGF antibody singly and in combination with cisplatin reduced neoangiogenesis and vascular hyperpermeability. However, it is clear from the results that the combination treatment had no additive effect in reducing vascular hyperpermeability. Serum VEGF was not reduced significantly after treatment in EAC ascites tumor bearing mice, whereas in EAC solid tumor bearing mice it was reduced significantly after treatment. The results clearly show that though alone cisplatin showed antitumor efficacy but it had no significant inhibitory effect on neoangiogenesis and vascular hyperpermeability. Thus the present study suggests that anti-VEGF agent can be combined with traditional treatment modalities to ensure more effectiveness.

ZD6474, an inhibitor of VEGFR and EGFR tyrosine kinase activity in combination with radiotherapy

Radiation enhances both epithelial growth factor receptor (EGFR) and vascular endothelial growth factor (VEGF) expression, which are a part of key pathways for tumor progression. Some tumors may not respond well to EGFR inhibitors alone or may develop resistance to EGFR inhibitors. Therefore, drug therapy targeted to VEGF receptors and EGFRs, when combined with radiotherapy (RT), may improve tumor control and provide wider applicability. This article focuses on ZD6474, an inhibitor of EGFR and VEGF receptor signaling in combination with RT. We discuss preclinical and clinical studies with RT and inhibitors of VEGF or EGFR signaling first. We then address issues associated with ZD6474 pharmacokinetic dosing, and scheduling when combined with RT. We also discuss ZD6474 in the context of anti-EGFR therapy resistance. Dual inhibition of EGFR and VEGF receptor signaling pathways shows promise in enhancing RT efficacy.