Exploiting metabolic vulnerabilities after anti-VEGF antibody therapy in ovarian cancer

Despite modest clinical improvement with anti-vascular endothelial growth factor antibody (AVA) therapy in ovarian cancer, adaptive resistance is ubiquitous and additional options are limited. A dependence on glutamine metabolism, via the enzyme glutaminase (GLS), is a known mechanism of adaptive resistance and we aimed to investigate the utility of a GLS inhibitor (GLSi). Our in vitro findings demonstrated increased glutamine abundance and a significant cytotoxic effect in AVA-resistant tumors when GLSi was administered in combination with bevacizumab. In vivo, GLSi led to a reduction in tumor growth as monotherapy and when combined with AVA. Furthermore, GLSi initiated after the emergence of resistance to AVA therapy resulted in a decreased metabolic conversion of pyruvate to lactate as assessed by hyperpolarized magnetic resonance spectroscopy and demonstrated robust antitumor effects with a survival advantage. Given the increasing population of patients receiving AVA therapy, these findings justify further development of GLSi in AVA resistance.

Evaluations of the performances of PET and MRI in a simultaneous PET/MRI instrument for pre-clinical imaging

Background

PET/MRI is an attractive imaging modality due to the complementary nature of MRI and PET. Obtaining high quality small animal PET/MRI results is key for the translation of novel PET/MRI agents and techniques to the radiology clinic. To obtain high quality imaging results, a hybrid PET/MRI system requires additional considerations beyond the standard issues with separate PET and MRI systems. In particular, researchers must understand how their PET system affects the MR acquisitions and vice versa. Depending on the application, some of these effects may substantially influence image quality. Therefore, the goal of this report is to provide guidance, recommendations, and practical experiments for implementing and using a small animal PET/MRI instrument.

Results

Various PET and MR image quality parameters were tested with their respective modality alone and in the presence of both systems to determine how the combination of PET/MRI affects image quality. Corrections and calibrations were developed for many of these effects. While not all image characteristics were affected, some characteristics such as PET quantification, PET SNR, PET spatial resolution, PET partial volume effects, and MRI SNR were altered by the presence of both systems.

Conclusions

A full exploration of a new PET/MRI system before performing small animal PET/MRI studies is beneficial and necessary to ensure that the new instrument can produce highly accurate and precise PET/MR images.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40658-022-00483-x.

Abstract 2484: Hyperpolarized magnetic resonance spectroscopy assessment of the metabolic effects of glutaminase inhibitor therapy in an ovarian cancer model

Introduction: Ovarian cancer accounts for more deaths than any other cancer of the female reproductive system despite advances in targeted drugs such as anti-VEGF antibody (AVA). Additionally, resistance to AVA therapy is nearly ubiquitous given the occurrence of metabolic adaptations such as a dependence on glutamine metabolism via the enzyme glutaminase.

Objectives: To examine the metabolic vulnerability of AVA-resistant cancer with glutaminase inhibitor (GLSi) therapy and to test the utility of hyperpolarized magnetic resonance spectroscopy (HP-MRS) for assessing changes in lactate metabolism associated with GLSi treatment following injection of hyperpolarized [1-13C] pyruvate.

Methods: We used a well-characterized SKOV3ip1 orthotopic mouse model of high-grade serous ovarian cancer with adaptive resistance to AVA (bevacizumab) treatment. Following three weeks of GLSi and bevacizumab treatment, we performed HP-MRS imaging to directly and non-invasively compare metabolic changes between the treatment groups of bevacizumab monotherapy versus a combined treatment of bevacizumab plus GLSi therapy. Upon injection of hyperpolarized [1-13C] pyruvate, we quantitatively assessed a normalized lactate ratio (nLac), defined as the 13C resonance signal of lactate divided by the sum of the pyruvate and lactate signals, sixty seconds after injection. GLSi treatment effect was subsequently compared between GLSi monotherapy, bevacizumab monotherapy and control mice receiving no therapy. This was performed via gross necropsy to assess disease burden and quantification of tumor weight and nodule number.

Results: Significance analysis microarrays (SAM) of bevacizumab treated tumors from the mouse models revealed greater glutamine and glutamate abundance in all tissues suggestive of a glutamine dependence in AVA resistant tumors that could be susceptible to glutaminase inhibition. The in vivo HP-MRS provided a direct and non-invasive investigation of pyruvate metabolism of tumors in situ. Our analysis indicated that the pyruvate-to-lactate conversion was significantly reduced in vivo by GLSi treatment (0.337 vs 0.178, p=0.0002), suggestive of therapeutic efficacy of GLSi in the setting of AVA-resistant tumors. Consistent with this, we observed a statistically significant reduction in tumor weight (0.05g vs 0.62g and 0.64g, p<0.01) and tumor nodule number (n=3.3 vs n=12.8 and n=13.9, p<0.05) in mice treated with a combination of bevacizumab and GLSi compared to the control group, or GLSi monotherapy, respectively.

Conclusions: Using HP-MRS in vivo, we directly monitored metabolic changes occurring after GLSi treatment. These findings are consistent with the notion of glutamine dependence being an important resistance mechanism to AVA therapy and imply potential future use of HP-MRS in monitoring therapeutic efficacy in a clinical realm.

Citation Format: Deanna Glassman, Mark S. Kim, Prasanta Dutta, Charles V. Kingsley, Emine Bayraktar, Yutuan Wu, Elaine Stur, Lingegowda S. Mangala, Katherine Foster, Sanghoon Lee, Timothy A. Yap, Shannon N. Westin, Pratip Bhattacharya, Anil K. Sood. Hyperpolarized magnetic resonance spectroscopy assessment of the metabolic effects of glutaminase inhibitor therapy in an ovarian cancer model [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 2484.

Technical Note: Histological validation of anatomical imaging for breast modeling using a novel cryo-microtome

PURPOSE

Precise correlation between three-dimensional (3D) imaging and histology can aid biomechanical modeling of the breast. We develop a framework to register ex vivo images to histology using a novel cryo-fluorescence tomography (CFT) device.

METHODS

A formalin-fixed cadaveric breast specimen, including chest wall, was subjected to high-resolution magnetic resonance (MR) imaging. The specimen was then frozen and embedded in an optimal cutting temperature (OCT) compound. The OCT block was placed in a CFT device with an overhead camera and 50 μm thick slices were successively shaved off the block. After each shaving, the block-face was photographed. At select locations including connective/adipose tissue, muscle, skin, and fibroglandular tissue, 20 μm sections were transferred onto cryogenic tape for manual hematoxylin and eosin staining, histological assessment, and image capture. A 3D white-light image was automatically reconstructed from the photographs by aligning fiducial markers embedded in the OCT block. The 3D MR image, 3D white-light image, and photomicrographs were rigidly registered. Target registration errors (TREs) were computed based on 10 pairs of points marked at fibroglandular intersections. The overall MR-histology registration was used to compare the MR intensities at tissue extraction sites with a one-way analysis of variance.

RESULTS

The MR image to CFT-captured white-light image registration achieved a mean TRE of 0.73 ± 0.25 mm (less than the 1 mm MR slice resolution). The block-face white-light image and block-face photomicrograph registration showed visually indistinguishable alignment of anatomical structures and tissue boundaries. The MR intensities at the four tissue sites identified from histology differed significantly (p < 0.01). Each tissue pair, except the skin-connective/adipose tissue pair, also had significantly different MR intensities (p < 0.01).

CONCLUSIONS

Fine sectioning in a highly controlled imaging/sectioning environment enables accurate registration between the MR image and histology. Statistically significant differences in MR signal intensities between histological tissues are indicators for the specificity of correlation between MRI and histology.

Combination of PD-1 Inhibitor and OX40 Agonist Induces Tumor Rejection and Immune Memory in Mouse Models of Pancreatic Cancer

BACKGROUND & AIMS

Advanced pancreatic ductal adenocarcinoma (PDAC) is resistant to therapy, including immune checkpoint inhibitors. We evaluated the effects of a neutralizing antibody against programmed cell death 1 (PD-1) and an agonist of OX40 (provides a survival signal to activated T cells) in mice with pancreatic tumors.

METHODS

We performed studies in C57BL/6 mice (controls), Kras^G12D/+;Trp53^R172H/+;Pdx-1-Cre (KPC) mice, and mice with orthotopic tumors grown from Panc02 cells, Kras^G12D;P53^flox/flox;PDX-1-Cre;Luciferase (KPC-Luc) cells, or mT4 cells. After tumors developed, mice were given injections of control antibody or anti-OX40 and/or anti-PD-1 antibody. Some mice were then given injections of antibodies against CD8, CD4, or NK1.1 to deplete immune cells, and IL4 or IL7RA to block cytokine signaling. Bioluminescence imaging was used to monitor tumor growth. Tumor tissues collected and single-cell suspensions were analyzed by time of flight mass spectrometry analysis. Mice that were tumor-free 100 days after implantation of orthotopic tumors were rechallenged with PDAC cells (KPC-Luc or mT4) and survival was measured. Median levels of PD-1 and OX40 mRNAs in PDACs were determined from The Cancer Genome Atlas and compared with patient survival times.

RESULTS

In mice with orthotopic tumors, all those given control antibody or anti-PD-1 died within 50 days, whereas 43% of mice given anti-OX40 survived for 225 days; almost 100% of mice given the combination of anti-PD-1 and anti-OX40 survived for 225 days, and tumors were no longer detected. KPC mice given control antibody, anti-PD-1, or anti-OX40 had median survival times of 50 days or less, whereas mice given the combination of anti-PD-1 and anti-OX40 survived for a median 88 days. Mice with orthotopic tumors that were given the combination of anti-PD-1 and anti-OX40 and survived 100 days were rechallenged with a second tumor; those rechallenged with mT4 cells survived an additional median 70 days and those rechallenged with KPC-Luc cells survived long term, tumor free. The combination of anti-PD-1 and anti-OX40 did not slow tumor growth in mice with antibody-mediated depletion of CD4+ T cells. Mice with orthotopic tumors given the combination of anti-PD-1 and anti-OX40 that survived after complete tumor rejection were rechallenged with KPC-Luc cells; those with depletion of CD4+ T cells before the rechallenge had uncontrolled tumor growth. Furthermore, KPC orthotopic tumors from mice given the combination contained an increased number of CD4+ T cells that expressed CD127 compared with mice given control antibody. The combination of agents reduced the proportion of T-regulatory and exhausted T cells and decreased T-cell expression of GATA3; tumor size was negatively associated with numbers of infiltrating CD4+ T cells, CD4+CD127+ T cells, and CD8+CD127+ T cells, and positively associated with numbers of CD4+PD-1+ T cells, CD4+CD25+ T cells, and CD8+PD-1+ T cells. PDACs with high levels of OX40 and low levels of PD-1 were associated with longer survival times of patients.

CONCLUSIONS

Pancreatic tumors appear to evade the immune response by inducing development of immune-suppressive T cells. In mice, the combination of anti-PD-1 inhibitory and anti-OX40 agonist antibodies reduces the proportion of T-regulatory and exhausted T cells in pancreatic tumors and increases numbers of memory CD4+ and CD8+ T cells, eradicating all detectable tumor. This information can be used in development of immune-based combination therapies for PDAC.

Selective EGLN Inhibition Enables Ablative Radiotherapy and Improves Survival in Unresectable Pancreatic Cancer

When pancreatic cancer cannot be removed surgically, patients frequently experience morbidity and death from progression of their primary tumor. Radiation therapy (RT) cannot yet substitute for an operation because radiation causes fatal bleeding and ulceration of the nearby stomach and intestines before achieving tumor control. There are no FDA-approved medications that prevent or reduce radiation-induced gastrointestinal injury. Here, we overcome this fundamental problem of anatomy and biology with the use of the oral EGLN inhibitor FG-4592, which selectively protects the intestinal tract from radiation toxicity without protecting tumors. A total of 70 KPC mice with autochthonous pancreatic tumors received oral FG-4592 or vehicle control ± ablative RT to a cumulative 75 Gy administered in 15 daily fractions to a limited tumor field. Although ablative RT reduced complications from local tumor progression, fatal gastrointestinal bleeding was observed in 56% of mice that received high-dose RT with vehicle control. However, radiation-induced bleeding was completely ameliorated in mice that received high-dose RT with FG-4592 (0% bleeding, P < 0.0001 compared with vehicle). Furthermore, FG-4592 reduced epithelial apoptosis by half (P = 0.002) and increased intestinal microvessel density by 80% compared with vehicle controls. EGLN inhibition did not stimulate cancer growth, as treatment with FG-4592 alone, or overexpression of HIF2 within KPC tumors independently improved survival. Thus, we provide a proof of concept for the selective protection of the intestinal tract by the EGLN inhibition to enable ablative doses of cytotoxic therapy in unresectable pancreatic cancer by reducing untoward morbidity and death from radiation-induced gastrointestinal bleeding. SIGNIFICANCE: Selective protection of the intestinal tract by EGLN inhibition enables potentially definitive doses of radiation therapy. This might allow radiation to be a surgical surrogate for unresectable pancreatic cancer.Graphical Abstract: http://cancerres.aacrjournals.org/content/canres/79/9/2327/F1.large.jpg.

Radiation-induced lung toxicity in mice irradiated in a strong magnetic field

Strong magnetic fields affect radiation dose deposition in MRI-guided radiation therapy systems, particularly at interfaces between tissues of differing densities such as those in the thorax. In this study, we evaluated the impact of a 1.5 T magnetic field on radiation-induced lung damage in C57L/J mice. We irradiated 140 mice to the whole thorax with parallel-opposed Co-60 beams to doses of 0, 9.0, 10.0, 10.5, 11.0, 12.0, or 13.0 Gy (20 mice per dose group). Ten mice per dose group were irradiated while a 1.5 T magnetic field was applied transverse to the radiation beam and ten mice were irradiated with the magnetic field set to 0 T. We compared survival and noninvasive assays of radiation-induced lung damage, namely respiratory rate and metrics derived from thoracic cone-beam CTs, between the two sets of mice. We report two main results. First, the presence of a transverse 1.5 T field during irradiation had no impact on survival of C57L/J mice. Second, there was a small but statistically significant effect on noninvasive assays of radiation-induced lung damage. These results provide critical safety data for the clinical introduction of MRI-guided radiation therapy systems.

Efficacy of ONC201 in Desmoplastic Small Round Cell Tumor

Desmoplastic Small Round Cell Tumor (DSRCT) is a rare sarcoma tumor of adolescence and young adulthood, which harbors a recurrent chromosomal translocation between the Ewing’s sarcoma gene (EWSR1) and the Wilms’ tumor suppressor gene (WT1). Patients usually develop multiple abdominal tumors with liver and lymph node metastasis developing later. Survival is poor using a multimodal therapy that includes chemotherapy, radiation and surgical resection, new therapies are needed for better management of DSRCT. Triggering cell apoptosis is the scientific rationale of many cancer therapies. Here, we characterized for the first time the expression of pro-apoptotic receptors, tumor necrosis-related apoptosis-inducing ligand receptors (TRAILR1-4) within an established human DSRCT cell line and clinical samples. The molecular induction of TRAIL-mediated apoptosis using agonistic small molecule, ONC201 in vitro cell-based proliferation assay and in vivo novel orthotopic xenograft animal models of DSRCT, was able to inhibit cell proliferation that was associated with caspase activation, and tumor growth, indicating that a cell-based delivery of an apoptosis-inducing factor could be relevant therapeutic agent to control DSRCT.

Differential Effects of EGFL6 on Tumor versus Wound Angiogenesis

Angiogenesis inhibitors are important for cancer therapy, but clinically approved anti-angiogenic agents have shown only modest efficacy and can compromise wound healing. This necessitates the development of novel anti-angiogenesis therapies. Here, we show significantly increased EGFL6 expression in tumor versus wound or normal endothelial cells. Using a series of in vitro and in vivo studies with orthotopic and genetically engineered mouse models, we demonstrate the mechanisms by which EGFL6 stimulates tumor angiogenesis. In contrast to its antagonistic effects on tumor angiogenesis, EGFL6 blockage did not affect normal wound healing. These findings have significant implications for development of anti-angiogenesis therapies.

Expression pattern of FGFR2, Grb2 and Plcγ1 acts as a novel prognostic marker of recurrence recurrence-free survival in lung adenocarcinoma

Lung adenocarcinoma is characterized by complex biology involving alterations at the genomic and protein expression levels. FGFR2 mutation and/or amplification are key drivers of disease progression and drug resistance in lung adenocarcinoma patients. These genetic alterations drive oncogenic downstream signalling due to the deregulated activity of the receptor. We have previously reported that wild type FGFR2 provides a binding site for which two proteins, Grb2 and Plcγ1, compete in a concentration-dependent manner. Metastasis and invasion ensue when Plcγ1 prevails on the receptor giving rise to oncogenic outcome in the absence of gene mutation/deletion. The effect of this signalling mechanism on FGFR2-driven lung adenocarcinoma has not previously been considered. In this study we show that fluctuation in the combinatorial expression levels of FGFR2, Grb2 and Plcγ1 modulates cell invasive properties, tumor formation and is linked to recurrence-free survival in 150 lung adenocarcinoma patients. High levels of expression of FGFR2 and Plcγ1 in a low background of Grb2 significantly correlates with poor prognosis. On the other hand, low levels of expression of FGFR2 and Plcγ1 in a high background of Grb2 correlates with favourable prognosis. This study defines the expression pattern of FGFR2, Plcγ1 and Grb2 as a novel prognostic marker in human lung adenocarcinoma. Thus, consideration of the Grb2 and Plcγ1-mediated mechanism of FGFR2 regulation will enhance the therapeutic targeting of aberrant FGFR2 activity to provide the much-needed improvement to the treatment regimen of this high mortality disease.

3D-Printed Small-Animal Immobilizer for Use in Preclinical Radiotherapy

We have designed a method for immobilizing the subjects of small-animal studies using a study group-specific 3D-printed immobilizer that significantly reduces interfraction rotational variation. A cone-beam CT scan acquired from a single specimen in a study group was used to create a 3D-printed immobilizer that can be used for all specimens in the same study group. 3D printing allows for the incorporation of study-specific features into the immobilizer design, including geometries suitable for use in MR and CT scanners, holders for fiducial markers, and anesthesia nose cones of various sizes. Using metrics of rotational setup variations, we compared the current setup in our small-animal irradiation system, a half-pipe bed, with the 3D-printed device. We also assessed translational displacement within the immobilizer. The printed design significantly reduced setup variation, with average reductions in rotational displacement of 76% ± 3% (1.57 to 0.37°) in pitch, 78% ± 3% (1.85 to 0.41°) in yaw, and 87% ± 3% (5.39 to 0.70°) in roll. Translational displacement within the printed immobilizer was less than 1.5 ± 0.3 mm. This method of immobilization allows for repeatable setup when using MR or CT scans for the purpose of radiotherapy, streamlines the workflow, and places little burden on the study subjects.

IAPP-driven metabolic reprogramming induces regression of p53-deficient tumours in vivo

TP53 is commonly altered in human cancer, and Tp53 reactivation suppresses tumours in vivo in mice (TP53 and Tp53 are also known as p53). This strategy has proven difficult to implement therapeutically, and here we examine an alternative strategy by manipulating the p53 family members, Tp63 and Tp73 (also known as p63 and p73, respectively). The acidic transactivation-domain-bearing (TA) isoforms of p63 and p73 structurally and functionally resemble p53, whereas the ΔN isoforms (lacking the acidic transactivation domain) of p63 and p73 are frequently overexpressed in cancer and act primarily in a dominant-negative fashion against p53, TAp63 and TAp73 to inhibit their tumour-suppressive functions. The p53 family interacts extensively in cellular processes that promote tumour suppression, such as apoptosis and autophagy, thus a clear understanding of this interplay in cancer is needed to treat tumours with alterations in the p53 pathway. Here we show that deletion of the ΔN isoforms of p63 or p73 leads to metabolic reprogramming and regression of p53-deficient tumours through upregulation of IAPP, the gene that encodes amylin, a 37-amino-acid peptide co-secreted with insulin by the β cells of the pancreas. We found that IAPP is causally involved in this tumour regression and that amylin functions through the calcitonin receptor (CalcR) and receptor activity modifying protein 3 (RAMP3) to inhibit glycolysis and induce reactive oxygen species and apoptosis. Pramlintide, a synthetic analogue of amylin that is currently used to treat type 1 and type 2 diabetes, caused rapid tumour regression in p53-deficient thymic lymphomas, representing a novel strategy to target p53-deficient cancers.

Feasibility of multianimal hyperpolarized (13) C MRS

PURPOSE

There is great potential for real-time investigation of metabolism with MRS and hyperpolarized (HP) (13) C agents. Unfortunately, HP technology has high associated costs and efficiency limitations that may constrain in vivo studies involving many animals. To improve the throughput of preclinical investigations, we evaluate the feasibility of performing HP MRS on multiple animals simultaneously.

METHODS

Simulations helped assess the viability of a dual-coil strategy for spatially localized multivolume MRS. A dual-mouse system was assembled and characterized with bench- and scanner-based experiments. Enzyme phantoms mixed with HP [1-(13) C] pyruvate emulated real-time metabolism and offered a controlled mechanism for evaluating system performance. Finally, a normal mouse and a mouse bearing a subcutaneous xenograft of colon cancer were simultaneously scanned in vivo using an agent containing HP [1-(13) C] pyruvate.

RESULTS

Geometric separation/rotation, active decoupling, and use of low input impedance preamplifiers permitted an encode-by-channel approach for spatially localized MRS. A precalibrated shim allowed straightforward metabolite differentiation in enzyme phantom and in vivo experiments at 7 Tesla, with performance similar to conventional acquisitions.

CONCLUSION

The initial feasibility of multi-animal HP (13) C MRS was established. Throughput scales with the number of simultaneously scanned animals, demonstrating the potential for significant improvements in study efficiency.