PEGPH20, a PEGylated Human Hyaluronidase, Induces Radiosensitization by Reoxygenation In Pancreatic Cancer Xenografts. A Molecular Imaging Study

PEGylated human hyaluronidase (PEGPH20) enzymatically depletes hyaluronan, an important component of the extracellular matrix, in tumors. The resultant improvement in vascular patency and perfusion has been shown to increase the delivery of therapeutic molecules. We show that PEGPH20 also improves the efficacy of radiation therapy in a human pancreatic adenocarcinoma BxPC3 mouse model overexpressing hyaluronan synthase 3 (BxPC3-HAS3) while exerting little effect on the corresponding wild type tumors. Mice overexpressing HAS3 developed fast growing, radiation resistant tumors that became rapidly more hypoxic as time progressed. Treatment with PEGPH20 increased survival times when used in combination with radiation therapy, significantly more than either radiation therapy or PEGPH20 alone. Radiosensitization in BxPC3-HAS3 tumors was attributed to an increase in local pO2 as studied by by EPR imaging. No effect on survival, radiation treatment, or pO2 was seen in wild type tumors after PEGPH20 treatment. Dynamic contrast enhanced (DCE) MRI and MRI based blood volume imaging showed improved perfusion/permeability and local blood volume, respectively, in BxPC3-HAS3 tumors after PEGPH20 treatment, accounting for the increase in tumor oxygenation. Photoacoustic imaging indicated immediate changes in tumor oxygenation after treatment. Metabolic MRI using hyperpolarized [1-13C] pyruvate suggested a metabolic shift towards decreased glycolytic flux after PEGPH20 treatment. In summary, the results showed that PEGPH20 may be useful for radiosensitization of pancreatic cancer but only in the subset of tumors with substantial hyaluronan accumulation and the response of the treatment may potentially be monitored non-invasive imaging of the hemodynamic and metabolic changes in the tumor microenvironment.

Diffuse Optical Spectroscopy Monitoring of Experimental Tumor Oxygenation after Red and Blue Light Photodynamic Therapy

Photodynamic therapy (PDT) is an effective technique for cancer treatment based on photoactivation of photosensitizer accumulated in pathological tissues resulting in singlet oxygen production. Employment of red (660 nm) or blue (405 nm) light differing in typical penetration depth within the tissue for PDT performance provides wide opportunities for improving PDT protocols. Oxygenation dynamics in the treated area can be monitored using diffuse optical spectroscopy (DOS) which allows evaluating tumor response to treatment. In this study, we report on monitoring oxygenation dynamics in experimental tumors after PDT treatment with chlorin-based photosensitizers using red or blue light. The untreated and red light PDT groups demonstrate a gradual decrease in tumor oxygen saturation during the 7-day observation period, however, the reason is different: in the untreated group, the effect is explained by the excessive tumor growth, while in the PDT group, the effect is caused by the blood flow arrest preventing delivery of oxygenated blood to the tumor. The blue light PDT procedure, on the contrary, demonstrates the preservation of the blood oxygen saturation in the tumor during the entire observation period due to superficial action of the blue-light PDT and weaker tumor growth inhibition. Irradiation-only regimes show a primarily insignificant decrease in tumor oxygen saturation owing to partial inhibition of tumor growth. The DOS observations are interpreted based on histology analysis.

ANGI-1 Impact of neoadjuvant bevacizumab on transcriptional factor for stemness, macrophage polarization, and oxygenation of tumor microenvironment in glioblastoma

Background: Previously we reported that bevacizumab (Bev) produces tumor oxygenation with immunosupportive tumor microenvironment (TME) and inhibition of stemness. To confirm whether those effects might contribute prolongation of clinical outcome, in the present study paired samples from same patients with newly diagnosed GBM who received Bev during its effectiveness and refractoriness were investigated by immunohistochemistry. Methods: Eighteen samples from 9 patients with newly diagnosed GBM who received preoperative neoadjuvant Bev (neoBev) followed by surgical operation and chemoradiotherapy in addition to salvage surgery after recurrence were investigated. Expressions of FOXM1, HIF-1, and CD163 were evaluated by immunohistochemistry. Overall survial (OS) were analyzed with the present cohort divided into two groups between good and poor responder (GR and PR, respectively) of Bev defined as tumor regression rate judged by T1 gadolinium enhancement (T1Gd) and fluid attenuated inversion recovery (FLAIR) images. Results: In the group of good responder of T1Gd (T1Gd-GR; defined as >38% of regression rate after neoBev), OS was prolonged compared with T1Gd-PR along with inhibition of FOXM1 expression and HIF-1a. In contrast, in the group of good responder of FLAIR (FLAIR-GR; defined as >54% of regression rate after neoBev), there were no significant differences of OS and FOXM1 expression between GR and PR. HIF-1a expression tended to be elevated in T1Gd-PR of initial tumors, T1Gd-GR of recurrent tumors, and FLAIR-PR of both initial and recurrent tumors.Conclusion: T1Gd-GR after neoBev might attribute to inhibition of FOXM1 and oxygenation. Bev might provide tumor oxygenation, leading to inhibition of stemness and M2 TAM infiltration during its effectiveness. These results suggested that Bev combined with immunotherapy for newly diagnosed GBM might provide clinical benefits including inhibition of stemness and induction of immunosupportive TME, when tumor volume assessed by T1 Gd. was significantly decreased following neoBev.

Artificial Neural Network-Derived Cerebral Metabolic Rate of Oxygen for Differentiating Glioblastoma and Brain Metastasis in MRI: A Feasibility Study

Glioblastoma may appear similar to cerebral metastasis on conventional MRI in some cases, but their therapies differ significantly. This prospective feasibility study was aimed at differentiating them by applying the quantitative susceptibility mapping and quantitative blood-oxygen-level-dependent (QSM + qBOLD) model to these entities for the first time. We prospectively included 15 untreated patients with glioblastoma (n = 7, median age: 68 years, range: 54–84 years) or brain metastasis (n = 8, median age 66 years, range: 50–78 years) who underwent preoperative MRI including multi-gradient echo and arterial spin labeling sequences. Oxygen extraction fraction (OEF), cerebral blood flow (CBF) and cerebral metabolic rate of oxygen (CMRO2) were calculated in the contrast-enhancing tumor (CET) and peritumoral non-enhancing T2 hyperintense region (NET2), using an artificial neural network. We demonstrated that OEF in CET was significantly lower (p = 0.03) for glioblastomas than metastases, all features were significantly higher (p = 0.01) in CET than in NET2 for metastasis patients only, and the ratios of CET/NET2 for CBF (p = 0.04) and CMRO2 (p = 0.01) were significantly higher in metastasis patients than in glioblastoma patients. Discriminative power of a support-vector machine classifier was highest with a combination of two features, yielding an area under the receiver operating characteristic curve of 0.94 with 93% diagnostic accuracy. QSM + qBOLD allows for robust differentiation of glioblastoma and cerebral metastasis while yielding insights into tumor oxygenation.

First-In-Human Study in Cancer Patients Establishing the Feasibility of Oxygen Measurements in Tumors Using Electron Paramagnetic Resonance With the OxyChip

ObjectiveThe overall objective of this clinical study was to validate an implantable oxygen sensor, called the ‘OxyChip’, as a clinically feasible technology that would allow individualized tumor-oxygen assessments in cancer patients prior to and during hypoxia-modification interventions such as hyperoxygen breathing.MethodsPatients with any solid tumor at ≤3-cm depth from the skin-surface scheduled to undergo surgical resection (with or without neoadjuvant therapy) were considered eligible for the study. The OxyChip was implanted in the tumor and subsequently removed during standard-of-care surgery. Partial pressure of oxygen (pO2) at the implant location was assessed using electron paramagnetic resonance (EPR) oximetry.ResultsTwenty-three cancer patients underwent OxyChip implantation in their tumors. Six patients received neoadjuvant therapy while the OxyChip was implanted. Median implant duration was 30 days (range 4–128 days). Forty-five successful oxygen measurements were made in 15 patients. Baseline pO2 values were variable with overall median 15.7 mmHg (range 0.6–73.1 mmHg); 33% of the values were below 10 mmHg. After hyperoxygenation, the overall median pO2 was 31.8 mmHg (range 1.5–144.6 mmHg). In 83% of the measurements, there was a statistically significant (p ≤ 0.05) response to hyperoxygenation.ConclusionsMeasurement of baseline pO2 and response to hyperoxygenation using EPR oximetry with the OxyChip is clinically feasible in a variety of tumor types. Tumor oxygen at baseline differed significantly among patients. Although most tumors responded to a hyperoxygenation intervention, some were non-responders. These data demonstrated the need for individualized assessment of tumor oxygenation in the context of planned hyperoxygenation interventions to optimize clinical outcomes.

Oxygenation Status of Malignant Tumors vs. Normal Tissues: Critical Evaluation and Updated Data Source Based on Direct Measurements with pO2 Microsensors

Immature and chaotic vascular networks with critically increased intervascular distances are characteristic features of malignant tumors. Spatial and temporal heterogeneities of blood flow and associated availabilities of O2, together with limited diffusive O2 transport, and -in some patients- anemia, obligatorily lead to tumor hypoxia (= critically reduced O2 levels) on macro- and microscopic scales. This detrimental condition, recently classified as a key hallmark of malignant growth, acts (a) as a barrier in most antitumor treatments, and (b) leads to malignant progression based on hypoxia-induced changes of the genome, transcriptome, and proteome, and finally to poor patient survival. This knowledge is, to a great extent, based on the systematic detection of tumor hypoxia in the clinical setting since the late 1980s. Precise assessment of the tumor oxygenation status was made possible using minimally invasive polarographic pO2 microsensors in a series of research projects. To assess tumor hypoxia in the clinical setting, it is highly desirable to use technologies with (a) high spatial and temporal resolutions, (b) the capability to judge the severity of tumor hypoxia, (c) to allow mapping of pO2 of the whole tumor mass, and (d) to enable serial investigations in order to verify treatment-related changes in tumor hypoxia. Selection and treatment of cancer patients according to their individual tumor oxygenation/hypoxia status for intensified and/or personalized hypoxia-targeted treatment strategies should be the ultimate goal.

Compressed vessels bias red blood cell partitioning at bifurcations in a hematocrit-dependent manner: Implications in tumor blood flow

The tumor microenvironment is abnormal and associated with tumor tissue hypoxia, immunosuppression, and poor response to treatment. One important abnormality present in tumors is vessel compression. Vessel decompression has been shown to increase survival rates in animal models via enhanced and more homogeneous oxygenation. However, our knowledge of the biophysical mechanisms linking tumor decompression to improved tumor oxygenation is limited. In this study, we propose a computational model to investigate the impact of vessel compression on red blood cell (RBC) dynamics in tumor vascular networks. Our results demonstrate that vessel compression can alter RBC partitioning at bifurcations in a hematocrit-dependent and flow rate–independent manner. We identify RBC focusing due to cross-streamline migration as the mechanism responsible and characterize the spatiotemporal recovery dynamics controlling downstream partitioning. Based on this knowledge, we formulate a reduced-order model that will help future research to elucidate how these effects propagate at a whole vascular network level. These findings contribute to the mechanistic understanding of hemodilution in tumor vascular networks and oxygen homogenization following pharmacological solid tumor decompression.

Advanced imaging to assess longitudinal vascular changes in brain metastases treated with checkpoint inhibition.

3059 Background: Immune checkpoint inhibitors (ICI) have recently been shown to be effective for brain metastases (BM) in melanoma and lung cancer. Several studies demonstrate that 20-50% of BM patients respond to ICI. The reasons behind this wide variability in treatment response is not clear. Therefore, using physiologic imaging, we seek to identify the longitudinal biological changes exerted on BM as a result of ICI administration. Methods: Given the importance of aberrant tumor vasculature in cancer proliferation, we have focused on assessing changes in vascular physiology. We analyzed standard post-contrast and dynamic susceptibility contrast (DSC) MRI to identify characteristic vascular signatures as part of an ongoing Phase 2 study of pembrolizumab for patients with untreated or progressive, previously treated BM from any histology. Tumor volume measurements were calculated by summating all enhancing voxels. As per modified RECIST and RANO criteria for immunotherapy, volumetric increase of > 40% was defined as progressive disease (PD), a decrease of > 60% as partial response (PR), and stable disease (SD) as between -60% and +40%. Results: 35 patients, out of the total cohort of 60, have undergone DSC-MRI analysis. Histologies include 15 with breast cancer, 6 with non-small cell lung cancer, 4 with melanoma, and 10 with other cancers. At baseline, the total number of BM was 1-50+ per patient. Based on summing the entire enhancing intracranial disease burden, best volumetric responses for the 35 evaluable patients include 4 PR, 12 SD, and 19 PD. Thus far, we found that ICI-resistant BM had a 50% increase in cerebral blood flow (CBF), 105% increase in cerebral blood volume (CBV), a 15% increase in mean transit time (MTT), and an 80% increase in vessel caliber at 6 weeks post-treatment. On the other hand, ICI-responsive BM had no change in CBF, a 33% increase in CBV, a 10% decrease in MTT, and no change in vessel caliber. Ongoing analysis to uncover additional vascular changes (e.g. tumor oxygenation, vessel size index) within BM to ICI are pending. Conclusions: Our data provides evidence that effective ICI for BM is associated with unique intra-tumoral vascular physiology. With final analysis, we will uncover other facets of vascular physiology that correlate with ICI response, and may reveal mechanisms of response/resistance within tumors to ICI.