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

The ADAM17-directed Inhibitory Antibody MEDI3622 Antagonizes Radiotherapy-induced VEGF Release and Sensitizes Non-Small Cell Lung Cancer for Radiotherapy

The cellular response to ionizing radiation (IR) depends on tumor cell and microenvironmental factors. Here, we investigated the role of IR-induced ADAM17 matrix metalloproteinase activity for the intercellular communication between tumor cells and the tumor vasculature in non-small cell lung cancer (NSCLC) tumor models. Factors shed by ADAM17 from NSCLC tumor cells (A549, H358) and relevant for endothelial cell migration were investigated using transwell migration assays, ELISA, and flow cytometry. Tumor angiogenesis-related endpoints were analyzed with the chorio-allantoic membrane assay and in murine NSCLC tumor models. Efficacy-oriented experiments were performed in a murine orthotopic NSCLC tumor model using irradiation with an image-guided small-animal radiotherapy platform alone and in combination with the novel ADAM17-directed antibody MEDI3622. In vitro, VEGF was identified as the major factor responsible for IR-induced and ADAM17-dependent endothelial cell migration toward attracting tumor cells. IR strongly enhanced tumor cell-associated ADAM17 activity, released VEGF in an ADAM17-dependent manner, and thereby coordinated the communication between tumor and endothelial cells. In vivo, tumor growth and microvessel size and density were strongly decreased in response to the combined treatment modality of IR and MEDI3622 but not by either treatment modality alone and thus suggest that the supra-additive effect of the combined treatment modality is in part due to abrogation of the ADAM17-mediated IR-induced protective effect on the tumor vasculature. Furthermore, we demonstrate that the novel ADAM17-inhibitory antibody MEDI3622 potently improves the radiotherapy response of NSCLC.

Significance

The tumor response to radiotherapy is influenced by several factors of the tumor microenvironment. We demonstrate that inhibition of the sheddase ADAM17 by the novel antibody MEDI3622 reduces IR-induced VEGF release from tumor cells relevant for endothelial cell migration and vasculature protection, thereby enhancing radiotherapy treatment outcome of NSCLC.

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.

Promising potential of [177Lu]Lu-DOTA-folate to enhance tumor response to immunotherapy-a preclinical study using a syngeneic breast cancer model

PURPOSE

It was previously demonstrated that radiation effects can enhance the therapy outcome of immune checkpoint inhibitors. In this study, a syngeneic breast tumor mouse model was used to investigate the effect of [¹⁷⁷Lu]Lu-DOTA-folate as an immune stimulus to enhance anti-CTLA-4 immunotherapy.

METHODS

In vitro and in vivo studies were performed to characterize NF9006 breast tumor cells with regard to folate receptor (FR) expression and the possibility of tumor targeting using [¹⁷⁷Lu]Lu-DOTA-folate. A preclinical therapy study was performed over 70 days with NF9006 tumor-bearing mice that received vehicle only (group A); [¹⁷⁷Lu]Lu-DOTA-folate (5 MBq; 3.5 Gy absorbed tumor dose; group B); anti-CTLA-4 antibody (3 × 200 μg; group C), or both agents (group D). The mice were monitored regarding tumor growth over time and signs indicating adverse events of the treatment.

RESULTS

[¹⁷⁷Lu]Lu-DOTA-folate bound specifically to NF9006 tumor cells and tissue in vitro and accumulated in NF9006 tumors in vivo. The treatment with [¹⁷⁷Lu]Lu-DOTA-folate or an anti-CTLA-4 antibody had only a minor effect on NF9006 tumor growth and did not substantially increase the median survival time of mice (23 day and 19 days, respectively) as compared with untreated controls (12 days). [¹⁷⁷Lu]Lu-DOTA-folate sensitized, however, the tumors to anti-CTLA-4 immunotherapy, which became obvious by reduced tumor growth and, hence, a significantly improved median survival time of mice (> 70 days). No obvious signs of adverse effects were observed in treated mice as compared with untreated controls.

CONCLUSION

Application of [¹⁷⁷Lu]Lu-DOTA-folate had a positive effect on the therapy outcome of anti-CTLA-4 immunotherapy. The results of this study may open new perspectives for future clinical translation of folate radioconjugates.

Improving the Efficacy of Tumor Radiosensitization Through Combined Molecular Targeting

Chemoradiation, either alone or in combination with surgery or induction chemotherapy, is the current standard of care for most locally advanced solid tumors. Though chemoradiation is usually performed at the maximum tolerated doses of both chemotherapy and radiation, current cure rates are not satisfactory for many tumor entities, since tumor heterogeneity and plasticity result in chemo- and radioresistance. Advances in the understanding of tumor biology, a rapidly growing number of molecular targeting agents and novel technologies enabling the in-depth characterization of individual tumors, have fuelled the hope of entering an era of precision oncology, where each tumor will be treated according to its individual characteristics and weaknesses. At present though, molecular targeting approaches in combination with radiotherapy or chemoradiation have not yet proven to be beneficial over standard chemoradiation treatment in the clinical setting. A promising approach to improve efficacy is the combined usage of two targeting agents in order to inhibit backup pathways or achieve a more complete pathway inhibition. Here we review preclinical attempts to utilize such dual targeting strategies for future tumor radiosensitization.

Emerging therapies: angiogenesis inhibitors for ovarian cancer

INTRODUCTION

Patients with epithelial ovarian cancer (EOC) have a high rate of recurrence, and overall survival remains at ∼ 25%. There is a need for new treatments that can increase progression free survival and quality of life. Recent clinical trials focus on angiogenesis, VEGFs, and tyrosine kinase inhibitors that play a role in recurrence, metastasis, and ascites in EOC.

AREAS COVERED

This review summarizes clinical rationale, mechanisms of action, and clinical data for angiogenesis inhibitors under evaluation in Phase II and III trials for EOC. Anti-angiogenesis agents reviewed in this paper include aflibercept, bevacizumab, cediranib, fosbretabulin, imatinib, nintedanib, pazopanib, saracatinib, sorafenib, sunitinib, and trebananib.

EXPERT OPINION

These agents have particular rationale for potential use in EOC due to the molecular changes associated with EOC tumorigenesis, namely a significant increase in angiogenic activity. Due to the costs and toxicities associated with anti-angiogenics, biomarker or molecular signature selection strategy for patients who will most benefit would be ideal but no such strategy has been validated to date.

Dynamics of tumor hypoxia in response to patupilone and ionizing radiation

Tumor hypoxia is one of the most important parameters that determines treatment sensitivity and is mainly due to insufficient tumor angiogenesis. However, the local oxygen concentration in a tumor can also be shifted in response to different treatment modalities such as cytotoxic agents or ionizing radiation. Thus, combined treatment modalities including microtubule stabilizing agents could create an additional challenge for an effective treatment response due to treatment-induced shifts in tumor oxygenation. Tumor hypoxia was probed over a prolonged observation period in response to treatment with different cytotoxic agents, using a non-invasive bioluminescent ODD-Luc reporter system, in which part of the oxygen-dependent degradation (ODD) domain of HIF-1α is fused to luciferase. As demonstrated in vitro, this system not only detects hypoxia at an ambient oxygen concentration of 1% O₂, but also discriminates low oxygen concentrations in the range from 0.2 to 1% O₂. Treatment of A549 lung adenocarcinoma-derived tumor xenografts with the microtubule stabilizing agent patupilone resulted in a prolonged increase in tumor hypoxia, which could be used as marker for its antitumoral treatment response, while irradiation did not induce detectable changes in tumor hypoxia. Furthermore, despite patupilone-induced hypoxia, the potency of ionizing radiation (IR) was not reduced as part of a concomitant or adjuvant combined treatment modality.

Metabolism of tumors under treatment: mapping of metabolites with quantitative bioluminescence

BACKGROUND AND PURPOSE

The metabolic switch to aerobic glycolysis (Warburg effect) and enhanced lactate production is characteristic for aggressive tumor cells and is a co-determining factor for tumor response and treatment outcome. Thus analysis of the metabolic status under treatment is important to understand and improve treatment modalities.

MATERIALS AND METHODS

Metabolite concentrations were determined by the immersion of tumor sections in an ATP, lactate or glucose-depending luciferase-containing buffer system. Integrated light output is detected in a bioluminescent detection system.

RESULTS

Mice carrying tumor xenografts derived from A549 lung cancer cells were treated with the microtubule stabilizing agent patupilone, ionizing radiation or in combination. Lactate levels were significantly reduced and glucose levels drastically increased in comparison to untreated tumors. Interestingly, these changes were only minimal in tumors derived from patupilone-resistant but otherwise isogenic A549EpoB40 cells. ATP levels of all tumors tested did not change under any treatment. When compared with histological endpoints, basal and treatment-dependent changes of lactate levels in the different tumors mainly correlated with the proliferative activity and the tumor growth response to treatment.

CONCLUSIONS

This study shows that the tumor metabolism is responsive to different treatment modalities and could eventually be used as an early surrogate marker for treatment response.

Ionizing radiation and inhibition of angiogenesis in a spontaneous mammary carcinoma and in a syngenic heterotopic allograft tumor model: a comparative study

Background

The combined treatment modality of ionizing radiation (IR) with inhibitors of angiogenesis (IoA) is a promising treatment modality based on preclinical in vivo studies using heterotopic xeno- and allograft tumor models. Nevertheless reservations still exist to translate this combined treatment modality into clinical trials, and more advanced, spontaneous orthotopic tumor models are required for validation to study the efficacy and safety of this treatment modality.

Findings

We therefore investigated the combined treatment modality of IR in combination with the clinically relevant VEGF receptor (VEGFR) tyrosine kinase inhibitor PTK787 in the MMTV/c-neu induced mammary carcinoma model and a syngenic allograft tumor model using athymic nude mice. Mice were treated with fractionated IR, the VEGFR-inhibitor PTK787/ZK222584 (PTK787), or in combination, and efficacy and mechanistic-related endpoints were probed in both tumor models. Overall the treatment response to the IoA was comparable in both tumor models, demonstrating minimal tumor growth delay in response to PTK787 and PTK787-induced tumor hypoxia. Interestingly spontaneously growing tumors were more radiosensitive than the allograft tumors. More important combined treatment of irradiation with PTK787 resulted in a supraadditive tumor response in both tumor models with a comparable enhancement factor, namely 1.5 and 1.4 in the allograft and in the spontaneous tumor model, respectively.

Conclusions

These results demonstrate that IR in combination with VEGF-receptor tyrosine kinase inhibitors is a valid, promising treatment modality, and that the treatment responses in spontaneous mammary carcinomas and syngenic allografts tumor models are comparable.

Endostar down-regulates HIF-1 and VEGF expression and enhances the radioresponse to human lung adenocarcinoma cancer cells

To study the effect of endostar on the expression of hypoxia-inducible factor 1 (HIF-1) and vascular endothelial growth factor (VEGF) and radiosensitization, the changes of A549 cells treated by endostar, radiotherapy and radiotherapy plus endostar were checked by flow cytometry (FCM), methyl thiazolyl tetrazolium (MTT), hoechst staining, and enzyme linked immunosorbent assay (ELISA). The results showed that endostar could block cell periods of A549 and stopped the cell cycle at G2/M and S periods. Cell growth inhibiting and apoptotic rate in the combination group were higher than those in other groups. Meanwhile, the levels of HIF-1 and VEGF expression in the combination group were lower than those of other groups. It suggested that endostar significantly sensitizes the function of radiation in A549 cells by arresting the cell cycle at stage of G2/M and S, increasing the cell growth inhibiting and the apoptotic rate, down-regulating the expression of HIF-1 and VEGF.

Molecular radiobiology meets clinical radiation oncology

BACKGROUND

The 2nd Langendorff Congress in Freiburg in Breisgau (Germany) gathered basic and translational scientists as well as clinicians interested in recent developments in molecular and clinical radiobiology. The topics ranged from the most recent insight into the organisation of the DNA damage response and radiotherapeutically relevant cell death mechanisms to biological imaging for treatment planning and advances in the understanding of the molecular biological effects of particle beams. Clinical aspects of stem cell and tumour stem cell biology as well as of angiogenesis and hypoxia, the search for novel molecular radiosensitisers and potential strategies for exploitation of the immune system to further improve tumour radiotherapy were also discussed.

RESULTS AND CONCLUSION

This report surveys the presentations at the meeting, considering their significance in light of the literature, and documents the increasing importance of molecular radiobiology for clinical radiooncology.

Radiosensitising agents for the radiotherapy of cancer: novel molecularly targeted approaches

BACKGROUND

The efficacy of radiotherapy (RT) for cancer treatment is limited by normal tissue toxicity and by the intrinsic or acquired radioresistance of many tumours. Therefore, continuing efforts are conducted to identify radiosensitising agents that preferentially sensitise tumour cells to the cytotoxic action of RT. Recent progresses in molecular oncology have uncovered an array of novel targets, which may be exploited for RT enhancement.

OBJECTIVE

To survey the patent literature of the past 4 years pertaining to the development of molecularly targeted agents as potential tumour radiosensitisers.

METHODS

Patents were searched with a set of relevant keywords using several search engines. A Medline search on the same topics was performed in parallel.

RESULTS/CONCLUSION

A total of 48 patents/applications were selected. These concerned agents target molecular components of pathways involved in DNA damage repair, cell growth and survival signalling, apoptosis modulation and tumour angiogenesis. Current trials of some of these agents may reveal their value as clinical radiosensitisers.

The role of apoptosis in radiation oncology

PURPOSE

Apoptosis, as a mode of cell death in irradiated cell populations, has been the subject of literarily hundreds if not thousands of published reports over the past few years. However, in spite of the large body of knowledge related to this subject, the role of apoptosis in determining tumor response to radiotherapy has been and remains poorly understood and controversial. Indeed, some previous reviews have suggested that apoptosis may not be important in this context. The purpose of the present review is to provide some examples of recently reported laboratory investigations that indicate that there is a reasonable expectation that the radiation-induced apoptosis observed has contributed to the tumor response.

CONCLUSIONS

We review reports in four areas of research: Molecularly targeted agents, in vivo imaging, Bcl-2 and cancer stem cells. Examples are provided in each of these areas that we believe justify a reassessment of the role that apoptosis plays in radiation oncology.