Hydrodynamic and Biochemical Impacts on the Development of Hypoxia in the Louisiana–Texas Shelf Part I: Numerical Modeling and Hypoxia Mechanisms

A three-dimensional coupled hydrodynamic–biogeochemical model with N, P, Si cycles and multiple phytoplankton and zooplankton functional groups was developed and applied to the Gulf of Mexico to study bottom dissolved oxygen dynamics. A 15-year hindcast was achieved covering the period of 2006–2020. Extensive model validation against in situ data demonstrates that the model is capable of reproducing vertical distributions of dissolved oxygen (DO), frequency distributions of hypoxia thickness, spatial distributions of bottom DO concentration and interannual variations of hypoxic area. The impacts of river plume and along-shore currents on bottom DO dynamics were examined based on multiyear bottom DO climatology, the corresponding long-term trends, and interannual variability. Model results suggest that mechanisms of bottom hypoxia developments are different between the west and east Louisiana–Texas Shelf waters. The mid-Atchafalaya nearshore (10–20 m) region firstly suffers from hypoxia in May, followed by the west-Mississippi nearshore region in June. Hypoxic waters expand in the following months and eventually merge in August. Sediment oxygen consumption (SOC) and water stratification (measured by potential energy anomaly, PEA) are two main factors modulating the variability of bottom DO concentration. Generalized Boosted Regression Models provide analysis of the relative importance of PEA and SOC. The analysis indicates that SOC is the main regulator in nearshore regions, and water stratification outcompetes the sedimentary biochemical processes in the offshore (20–50 m) regions. A strong quadratic relationship was found between hypoxic volume and hypoxic area, which suggests that the volume mostly results from the low DO in bottom water and can be potentially estimated based on the hypoxic area.

Paired 18F-Fluorodeoxyglucose (18F-FDG), and 64Cu-Copper(II)-diacetyl-bis(N(4)-methylthiosemicarbazone) (64Cu-ATSM) PET Scans in Dogs with Spontaneous Tumors and Evaluation for Hypoxia-Directed Therapy

Hypoxia is associated with neoplastic tissue, protecting cancer cells from death by irradiation and chemotherapy. Identification of hypoxic volume of tumors could optimize patient selection for hypoxia-directed medical, immunological, and radiation therapies. Clostridium novyi-NT (CNV-NT) is an oncolytic bacterium derived from attenuated wild-type Clostridium novyi spores, which germinates exclusively in the anaerobic core of tumors with low-oxygen content. The hypothesis was that 64Cu-ATSM would localize to regions of hypoxia, and that greater hypoxic volume would result in greater germination of Clostridium novyi-NT (CNV-NT). Tumor-bearing companion dogs were recruited to a veterinary clinical trial. Dogs received a CT scan, 18F-FDG PET scan (74 MBq) and 64Cu-ATSM PET scan (74 MBq). Scan regions of interest were defined as the highest 20% of counts/voxel for each PET scan, and regions with voxels overlapping between the two scans. Maximum standardized uptake value (MaxSUV) and threshold volume were calculated. Direct oximetry was performed in select tumors. Tumor types evaluated included nerve sheath tumor (10), apocrine carcinoma (1), melanoma (3) and oral sarcoma (6). MaxSUVATSM ranged from 0.3–6.6. Measured oxygen tension ranged from 0.05–89.9 mmHg. Inverse of MaxSUVATSM had a linear relationship with oxygen tension (R2 = 0.53, P = 0.0048). Hypoxia <8 mmHg was associated with an SUVATSM > 1.0. Hypoxic volume ranged from 0 to 100% of gross tumor volume (GTV) and MaxSUVATSM was positively correlated with hypoxic volume (R = 0.674; P = 0.0001), but not GTV (P = 0.182). Tumor hypoxic volume was heterogeneous in location and distribution. 64Cu-ATSM-avid regions were associated with differential CT attenuation. Hypoxic volume did not predict CNV-NT germination. 64Cu-ATSM PET scanning predicts hypoxia patterns within spontaneously occurring tumors of dogs as measured by direct oxymetry. Total tumor volume does not accurately predict degree or proportion of tumor hypoxia.

Investigation of atovaquone-induced spatial changes in tumour hypoxia assessed by hypoxia PET/CT in non-small cell lung cancer patients

Background Tumour hypoxia promotes an aggressive tumour phenotype and enhances resistance to anticancer treatments. Following the recent observation that the mitochondrial inhibitor atovaquone increases tumour oxygenation in NSCLC, we sought to assess whether atovaquone affects tumour subregions differently depending on their level of hypoxia. Methods Patients with resectable NSCLC participated in the ATOM trial (NCT02628080). Cohort 1 (n = 15) received atovaquone treatment, whilst cohort 2 (n = 15) did not. Hypoxia-related metrics, including change in mean tumour-to-blood ratio, tumour hypoxic volume, and fraction of hypoxic voxels, were assessed using hypoxia PET imaging. Tumours were divided into four subregions or distance categories: edge, outer, inner, and centre, using MATLAB. Results Atovaquone-induced reduction in tumour hypoxia mostly occurred in the inner and outer tumour subregions, and to a lesser extent in the centre subregion. Atovaquone did not seem to act in the edge subregion, which was the only tumour subregion that was non-hypoxic at baseline. Notably, the most intensely hypoxic tumour voxels, and therefore the most radiobiologically resistant areas, were subject to the most pronounced decrease in hypoxia in the different subregions. Conclusions This study provides insights into the action of atovaquone in tumour subregions that help to better understand its role as a novel tumour radiosensitiser. Trial registration: ClinicalTrials.gov, NCT0262808. Registered 11th December 2015, https://clinicaltrials.gov/ct2/show/NCT02628080

Assessment of tumor hypoxia and perfusion in recurrent glioblastoma following bevacizumab failure using MRI and 18F-FMISO PET

Tumoral hypoxia correlates with worse outcomes in glioblastoma (GBM). While bevacizumab is routinely used to treat recurrent GBM, it may exacerbate hypoxia. Evofosfamide is a hypoxia-targeting prodrug being tested for recurrent GBM. To characterize resistance to bevacizumab and identify those with recurrent GBM who may benefit from evofosfamide, we ascertained MRI features and hypoxia in patients with GBM progression receiving both agents. Thirty-three patients with recurrent GBM refractory to bevacizumab were enrolled. Patients underwent MR and 18F-FMISO PET imaging at baseline and 28 days. Tumor volumes were determined, MRI and 18F-FMISO PET-derived parameters calculated, and Spearman correlations between parameters assessed. Progression-free survival decreased significantly with hypoxic volume [hazard ratio (HR) = 1.67, 95% confidence interval (CI) 1.14 to 2.46, P = 0.009] and increased significantly with time to the maximum value of the residue (Tmax) (HR = 0.54, 95% CI 0.34 to 0.88, P = 0.01). Overall survival decreased significantly with hypoxic volume (HR = 1.71, 95% CI 1.12 to 12.61, p = 0.01), standardized relative cerebral blood volume (srCBV) (HR = 1.61, 95% CI 1.09 to 2.38, p = 0.02), and increased significantly with Tmax (HR = 0.31, 95% CI 0.15 to 0.62, p < 0.001). Decreases in hypoxic volume correlated with longer overall and progression-free survival, and increases correlated with shorter overall and progression-free survival. Hypoxic volume and volume ratio were positively correlated (rs = 0.77, P < 0.0001), as were hypoxia volume and T1 enhancing tumor volume (rs = 0.75, P < 0.0001). Hypoxia is a key biomarker in patients with bevacizumab-refractory GBM. Hypoxia and srCBV were inversely correlated with patient outcomes. These radiographic features may be useful in evaluating treatment and guiding treatment considerations.

Ranking ecosystem impacts on Chesapeake Bay blue crab (Callinectes sapidus) using empirical Gaussian Graphical Models

Moving toward ecosystem-based fisheries management requires integration of biotic and abiotic factors into our understanding of population dynamics. Using blue crab (Callinectes sapidus) in the Chesapeake Bay as a model system, we applied Gaussian Graphical Models (GGMs) to understand the influence of climatic, water quality and biotic variables on estimates of key indices of blue crab recruitment for 1990‐2017. Variables included the North Atlantic Oscillation (NAO), Susquehanna River discharge, wind forcing, hypoxic volume, submerged aquatic vegetation and the catch-per-unit-effort of striped bass (Morone saxatilis). Direct effects of age‐1+ crabs and summer salinity on recruitment were significant. Phase of the NAO in summer and spring, summer and winter discharge, and hypoxic volume indirectly affected the recruitment. A simulation study shows that GGM model selection achieved nominal coverage and outperformed structural equation models (SEM) and Multivariate Adaptive Regression Splines (MARS). GGMs have the potential to improve ecosystem-based management of blue crabs in Chesapeake Bay. Specifically, the approach can be used to examine ecosystem impacts on blue crab productivity and to improve forecasts of blue crab recruitment.

CBMT-39. TARGETING METABOLIC PATHWAYS IN HYPOXIA FOR GLIOBLASTOMA

BACKGROUND Metabolic adaptation to hypoxia is a crucial consideration in combating anti-angiogenic resistance. We previously explored the potential of targeting the peroxisomal fatty acid oxidation (FAO) pathway and observed higher potency to peroxisomal FAO inhibitor thioridazine in hypoxia in vitro. In this study we further examine the effects of peroxisomal FAO enzyme ACOX1, looking at differences in mitochondrial and peroxisomal FAO in hypoxia between subtypes, and explore additional metabolic pathways that can be potentially further studied. METHODS We utilized a CRISPR doxycycline-inducible U251 knockout cell line for the peroxisomal FAO gene ACOX1 and examined growth and viability in 2 weeks hypoxia (2% O2). We analyzed the gene expression of 13 peroxisomal and mitochondrial FAO enzymes in six different patient-derived cell lines. Finally, we characterized serum metabolites that are associated with tumor hypoxic volume, progression-free survival, and overall survival in patients undergoing clinical trial for TH302 and bevacizumab with bevacizumab refractory tumors. RESULTS We observed decreased cell growth and viability (p < .03) specifically in hypoxia but not normoxia with ACOX1 knock out. We saw some changes in gene expression (|ΔΔCt| >1) in hypoxia for all genes, which differed between cell lines. ACOX1 and CPT1A expression were strongly decreased (|ΔΔCt| >2) while ACADSB expression was strongly increased for the proneural cell line. ACOX1 expression was strongly decreased in our most thioridazine-sensitive cell line. ACOX2, ACADVL, CPT1A, CPT1C, and DECR2 expression were strongly increased in one of the proneural cell lines. Twelve polar metabolites were positively or negatively correlated (|r| >.4) with both hypoxic volume and either overall survival or progression-free survival. CONCLUSION Peroxisomal FAO and other metabolic pathways may be essential to target in order combat metabolic resistance during anti-angiogenic therapy. Better understanding differences in metabolism in different tumor environments will help determine which targets will be most therapeutically useful.

Assessment of tumor hypoxia in BEV resistant GBM using FMISO 18F-PET and MRI.

2045 Background: Glioblastoma (GBM) is the most common malignant brain tumor in adults, and is characterized by poor survival and marked resistance to treatment. Hypoxic volume is directly correlated with poor outcome in GBM, with structural and functional tumor vasculature changes regarded as a primary driver of tumor hypoxia. As part of an ongoing clinical trial with a hypoxia activated prodrug, we sought to explore the correlation between abnormal tumor vasculature and hypoxia in bevacizumab (BEV) resistant GBM. Methods: MRI and 18F-FMISO PET scans were acquired at study entry. The MRI protocols include standard anatomical sequences as well as Dynamic Susceptibility Contrast (DSC/perfusion) imaging. Enhancing tumor ROIs were determined from Delta T1 maps, non-enhancing tumor ROIs were obtained from FLAIR images, ratio between enhancing and non-enhancing volumes were calculated, values from standardized rCBV maps were extracted from corresponding enhancing ROIs. Decay correction was applied to18F-FMISO images and converted to SUV units. After registration to MR images, cerebellar regions were used as surrogates for blood activity. The FMISO images were then normalized to generate tissue to blood ratio (TB). A threshold of TB > 1.2 was used in discriminating the hypoxia volume (HV). Correlation between parameters was assessed using Pearson correlation. Results: 7 patients from University of Texas Health Science center and 7 patients from Dana-Farber Cancer Institute had evaluable MR and PET imaging. We compared MRI parameters (enhancing and non-enhancing tumor volumes, srCBV) with hypoxia (HV and maxSUV). There was a positive correlation between HV and enhancing volume (R = 0.732, p = 0.0029) as well as between HV and ratio (R = 0.644, p = 0.013. The correlation between other pairs were not statistically significant (HV vs srCBV: p = 0.862, T1 vs maxSUV p = 0.492, srCBV vs maxSUV: p = 0.393, ratio vs maxSUV = 0.178). Conclusions: The hypoxic volume following bevacizumab failure correlates with both the volume of enhancement and the fraction of enhancement within the mass. The clinical implications of this is being assessed in an ongoing phase 2 study. Clinical trial information: NCT02342379.