Optical imaging reveals chemotherapy-induced metabolic reprogramming of residual disease and recurrence.

Fewer than 20% of triple-negative breast cancer patients experience long-term responses to mainstay chemotherapy. Resistant tumor subpopulations use alternative metabolic pathways to escape therapy, survive, and eventually recur. Here, we show in vivo, longitudinal metabolic reprogramming in residual disease and recurrence of triple-negative breast cancer xenografts with varying sensitivities to the chemotherapeutic drug paclitaxel. Optical imaging coupled with metabolomics reported an increase in non-glucose-driven mitochondrial metabolism and an increase in intratumoral metabolic heterogeneity during regression and residual disease in resistant MDA-MB-231 tumors. Conversely, sensitive HCC-1806 tumors were primarily reliant on glucose uptake and minimal changes in metabolism or heterogeneity were observed over the tumors' therapeutic life cycles. Further, day-matched resistant HCC-1806 tumors revealed a higher reliance on mitochondrial metabolism and elevated metabolic heterogeneity compared to sensitive HCC-1806 tumors. Together, metabolic flexibility, increased reliance on mitochondrial metabolism, and increased metabolic heterogeneity are defining characteristics of persistent residual disease, features that will inform the appropriate type and timing of therapies.

Impact of Injection-Based Delivery Parameters on Local Distribution Volume of EthylCellulose Ethanol Gel in Tissue and Tissue Mimicking Phantoms.

: Local drug delivery aims to minimize systemic toxicity by preventing off-target effects; however, injection parameters influencing depot formation of injectable gels have yet to be thoroughly studied. We explored the effects of needle characteristics, injection depth, rate, volume, and polymer concentration on gel ethanol distribution in both tissue and phantoms. METHODS: The polymer ethyl cellulose (EC) was added to ethanol to form an injectable gel to ablate cervical precancer and cancer. Tissue mimicking phantoms composed of 1% agarose dissolved in deionized water were used to establish overall trends between various injection parameters and the resulting gel distribution. Additional experiments were performed in excised swine cervices with a CT-imageable injectate formulation, which enabled visualization of the distribution without tissue sectioning. RESULTS: Needle type and injection rate had minimal impact on gel distribution, while needle depths ≥13 mm yielded significantly larger distributions. Needle gauge and EC concentration impacted injection pressure with maximum gel distribution achieved when the pressure was 70-250 kPa. Injection volumes ≤3 mL of 6% ECethanol minimized fluid leakage away from the injection site. Results guided the development of a speculum-compatible handheld injector to deliver gel ethanol into the cervix. CONCLUSION: Needle depth, gauge, and polymer concentration are critical to consider when delivering injectable gels. SIGNIFICANCE: This study addressed key questions related to the impact of injection-based parameters on gel distribution at a scale relevant to human applications including: 1) how best to deliver EC-ethanol into the cervix and 2) general insights about injection protocols relevant to the delivery of injectable gels in tissue.

In Vivo Evaluation of Safety and Efficacy of Ethyl Cellulose-Ethanol Tissue Ablation in a Swine Cervix Model.

Current therapies for treating cervical dysplasia are often inaccessible in low and middle-income countries (LMICs), highlighting the need for novel low-cost therapies that can be delivered at the point of care. Ethanol ablation is a low-cost therapy designed to treat locoregional cancers, which we augmented into an ethyl cellulose (EC)-ethanol gel formulation to enhance its efficacy. Here, we evaluated whether EC-ethanol ablation is able to safely achieve an ablation zone comparable to thermocoagulation, a commonly used therapy for cervical dysplasia. The study was performed in 20 female Yorkshire pigs treated with either a single 500 µL injection of EC-ethanol into the 12 o'clock position of the cervix or a single application of thermocoagulation at 100 °C for 20 s. The average temperature, heart rate, respiratory rate, and blood oxygen remained within normal ranges throughout the EC-ethanol procedure and were similar to the thermocoagulation group. No major side effects were observed. The reproductive tracts were excised after 24 h to examine ablation zones. Comparable depths of necrosis were seen for EC-ethanol (18.6 ± 1.6 mm) and thermocoagulation (19.7 ± 4.1 mm). The volumes of necrosis induced by a single injection of EC-ethanol (626.2 ± 122.8 µL) were comparable to the necrotic volumes induced by thermocoagulation in the top half of the cervices (664.6 ± 168.5 µL). This suggests that two EC-ethanol injections could be performed (e.g., at the 12 and 6 o'clock positions) to achieve comparable total necrotic volumes to thermocoagulation and safely and effectively treat women with cervical dysplasia in LMICs. This is the first study to systematically evaluate EC-ethanol ablation in a large animal model and compare its safety and efficacy to thermocoagulation, a commonly used ablative therapy for cervical dysplasia.

Adaptive Design of Fluorescence Imaging Systems for Custom Resolution, Fields of View, and Geometries.

Objective and Impact Statement: We developed a generalized computational approach to design uniform, high-intensity excitation light for low-cost, quantitative fluorescence imaging of in vitro, ex vivo, and in vivo samples with a single device. Introduction: Fluorescence imaging is a ubiquitous tool for biomedical applications. Researchers extensively modify existing systems for tissue imaging, increasing the time and effort needed for translational research and thick tissue imaging. These modifications are application-specific, requiring new designs to scale across sample types. Methods: We implemented a computational model to simulate light propagation from multiple sources. Using a global optimization algorithm and a custom cost function, we determined the spatial positioning of optical fibers to generate 2 illumination profiles. These results were implemented to image core needle biopsies, preclinical mammary tumors, or tumor-derived organoids. Samples were stained with molecular probes and imaged with uniform and nonuniform illumination. Results: Simulation results were faithfully translated to benchtop systems. We demonstrated that uniform illumination increased the reliability of intraimage analysis compared to nonuniform illumination and was concordant with traditional histological findings. The computational approach was used to optimize the illumination geometry for the purposes of imaging 3 different fluorophores through a mammary window chamber model. Illumination specifically designed for intravital tumor imaging generated higher image contrast compared to the case in which illumination originally optimized for biopsy images was used. Conclusion: We demonstrate the significance of using a computationally designed illumination for in vitro, ex vivo, and in vivo fluorescence imaging. Application-specific illumination increased the reliability of intraimage analysis and enhanced the local contrast of biological features. This approach is generalizable across light sources, biological applications, and detectors.

Evaluating Tumor Hypoxia Radiosensitization Via Electron Paramagnetic Resonance Oxygen Imaging (EPROI).

PURPOSE: Tumor hypoxia contributes to aggressive phenotypes and diminished therapeutic responses to radiation therapy (RT) with hypoxic tissue being 3-fold less radiosensitive than normoxic tissue. A major challenge in implementing hypoxic radiosensitizers is the lack of a high-resolution imaging modality that directly quantifies tissue-oxygen. The electron paramagnetic resonance oxygen-imager (EPROI) was used to quantify tumor oxygenation in two murine tumor models: E0771 syngeneic transplant breast cancers and primary p53/MCA soft tissue sarcomas, with the latter autochthonous model better recapitulating the tumor microenvironment in human malignancies. We hypothesized that tumor hypoxia differs between these models. We also aimed to quantify the absolute change in tumor hypoxia induced by the mitochondrial inhibitor papaverine (PPV) and its effect on RT response. PROCEDURES: Tumor oxygenation was characterized in E0771 and primary p53/MCA sarcomas via EPROI, with the former model also being quantified indirectly via diffuse reflectance spectroscopy (DRS). After confirming PPV's effect on hypoxic fraction (via EPROI), we compared the effect of 0 versus 2 mg/kg PPV prior to 20 Gy on tumor growth delay and survival. RESULTS: Hypoxic sarcomas were more radioresistant than normoxic sarcomas (p=0.0057, 2-way ANOVA), and high baseline hypoxic fraction was a significant (p=0.0063, Cox Regression Model) hazard in survivability regardless of treatment. Pre-treatment with PPV before RT did not radiosensitize tumors in the sarcoma or E0771 model. In the sarcoma model, EPROI successfully identified baseline hypoxic tumors. DRS quantification of total hemoglobin, saturated hemoglobin, changes in mitochondrial potential and glucose uptake showed no significant difference in E0771 tumors pre- and post-PPV. CONCLUSION: EPROI provides 3D high-resolution pO2 quantification; EPR is better suited than DRS to characterize tumor hypoxia. PPV did not radiosensitize E0771 tumors nor p53/MCA sarcomas, which may be related to the complex pattern of vasculature in each tumor. Additionally, understanding model-dependent tumor hypoxia will provide a much-needed foundation for future therapeutic studies with hypoxic radiosensitizers.

Ethanol Ablation Therapy Drives Immune-Mediated Antitumor Effects in Murine Breast Cancer Models.

Ethanol ablation is a minimally invasive, cost-effective method of destroying tumor tissue through an intratumoral injection of high concentrations of cytotoxic alcohol. Ethyl-cellulose ethanol (ECE) ablation, a modified version of ethanol ablation, contains the phase-changing polysaccharide ethyl-cellulose to reduce ethanol leakage away from the tumor. Ablation produces tissue necrosis and initiates a wound healing process; however, the characteristic of the immunologic events after ECE ablation of tumors has yet to be explored. Models of triple-negative breast cancer (TNBC), which are classically immunosuppressive and difficult to treat clinically, were used to characterize the immunophenotypic changes after ECE ablation. In poorly invasive TNBC rodent models, the injury to the tumor induced by ECE increased tumor infiltrating lymphocytes (TILs) and reduced tumor growth. In a metastatic TNBC model (4T1), TILs did not increase after ECE ablation, though lung metastases were reduced. 4T1 tumors secrete high levels of granulocytic colony stimulating factor (G-CSF), which induces a suppressive milieu of granulocytic myeloid-derived suppressor cells (gMDSCs) aiding in the formation of metastases and suppression of antitumor immunity. We found that a single intratumoral injection of ECE normalized tumor-induced myeloid changes: reducing serum G-CSF and gMDSC populations. ECE also dampened the suppressive strength of gMDSC on CD4 and CD8 cell proliferation, which are crucial for anti-tumor immunity. To demonstrate the utility of these findings, ECE ablation was administered before checkpoint inhibitor (CPI) therapy in the 4T1 model and was found to significantly increase survival compared to a control of saline and CPI. Sixty days after tumor implant no primary tumors or metastatic lung lesions were found in 6/10 mice treated with CPI plus ECE, compared to 1/10 with ECE alone and 0/10 with CPI and saline.

In vivo metabolic imaging identifies lipid vulnerability in a preclinical model of Her2+/Neu breast cancer residual disease and recurrence.

Recurrent cancer cells that evade therapy is a leading cause of death in breast cancer patients. This risk is high for women showing an overexpression of human epidermal growth factor receptor 2 (Her2). Cells that persist can rely on different substrates for energy production relative to their primary tumor counterpart. Here, we characterize metabolic reprogramming related to tumor dormancy and recurrence in a doxycycline-induced Her2+/Neu model of breast cancer with varying times to recurrence using longitudinal fluorescence microscopy. Glucose uptake (2-NBDG) and mitochondrial membrane potential (TMRE) imaging metabolically phenotype mammary tumors as they transition to regression, dormancy, and recurrence. "Fast-recurrence" tumors (time to recurrence ~55 days), transition from glycolysis to mitochondrial metabolism during regression and this persists upon recurrence. "Slow-recurrence" tumors (time to recurrence ~100 days) rely on both glycolysis and mitochondrial metabolism during recurrence. The increase in mitochondrial activity in fast-recurrence tumors is attributed to a switch from glucose to fatty acids as the primary energy source for mitochondrial metabolism. Consequently, when fast-recurrence tumors receive treatment with a fatty acid inhibitor, Etomoxir, tumors report an increase in glucose uptake and lipid synthesis during regression. Treatment with Etomoxir ultimately prolongs survival. We show that metabolic reprogramming reports on tumor recurrence characteristics, particularly at time points that are essential for actionable targets. The temporal characteristics of metabolic reprogramming will be critical in determining the use of an appropriate timing for potential therapies; namely, the notion that metabolic-targeted inhibition during regression reports long-term therapeutic benefit.

Targeting Tumor Acidosis and Regulatory T Cells Unmasks Anti-Metastatic Potential of Local Tumor Ablation in Triple-Negative Breast Cancer.

Triple-negative breast cancer (TNBC) is an immunologically heterogenous disease that lacks clinically actionable targets and is more likely to progress to metastatic disease than other types of breast cancer. Tumor ablation has been used to increase response rates to checkpoint inhibitors, which remain low for TNBC patients. We hypothesized that tumor ablation could produce an anti-tumor response without using checkpoint inhibitors if immunosuppression (i.e., Tregs, tumor acidosis) was subdued. Tumors were primed with sodium bicarbonate (200 mM p.o.) to reduce tumor acidosis and low-dose cyclophosphamide (100-200 mg/kg i.p.) to deplete regulatory T cells, as has been shown independently in previous studies. A novel injectable ablative was then used to necrose the tumor, release tumor antigens, and initiate an immune event that could create an abscopal effect. This combination of bicarbonate, cyclophosphamide, and ablation, called "BiCyclA", was tested in three syngeneic models of TNBC: E0771 (C57BL/6), 67NR (BALB/c), and 4T1-Luc (BALB/c). In E0771 and 67NR, BiCyclA therapy significantly reduced tumor growth and cured 5/7 and 6/10 mice 50 days after treatment respectively. In the metastatic 4T1-Luc tumors, for which surgery and checkpoint inhibitors fail, BiCyclA cured 5/10 mice of primary tumors and lung metastases. Notably, CD4+ and CD8+ T cells were found to be crucial for the anti-metastatic response, and cured mice were able to resist tumor rechallenge, suggesting production of immune memory. Reduction of tumor acidity and regulatory T cells with ablation is a simple yet effective therapy for local and systemic tumor control with broad applicability as it is not limited by expensive supplies.

A Spectroscopic Technique to Simultaneously Characterize Fatty Acid Uptake, Mitochondrial Activity, Vascularity, and Oxygen Saturation for Longitudinal Studies In Vivo.

Aggressive breast cancer has been shown to shift its metabolism towards increased lipid catabolism as the primary carbon source for oxidative phosphorylation. In this study, we present a technique to longitudinally monitor lipid metabolism and oxidative phosphorylation in pre-clinical tumor models to investigate the metabolic changes with mammary tissue development and characterize metabolic differences between primary murine breast cancer and normal mammary tissue. We used optical spectroscopy to measure the signal of two simultaneously injected exogenous fluorescent metabolic reporters: TMRE (oxidative phosphorylation surrogate) and Bodipy FL C16 (lipid catabolism surrogate). We leverage an inverse Monte Carlo algorithm to correct for aberrations resulting from tissue optical properties and to extract vascular endpoints relevant to oxidative metabolism, specifically oxygen saturation (SO2) and hemoglobin concentration ([Hb]). We extensively validated our optical method to demonstrate that our two fluorescent metabolic endpoints can be measured without chemical or optical crosstalk and that dual measurements of both fluorophores in vivo faithfully recapitulate the measurements of each fluorophore independently. We then applied our method to track the metabolism of growing 4T1 and 67NR breast tumors and aging mammary tissue, all highly metabolic tissue types. Our results show the changes in metabolism as a function of mammary age and tumor growth, and these changes can be best distinguished through the combination of endpoints measured with our system. Clustering analysis incorporating both Bodipy FL C16 and TMRE endpoints combined with either SO2 or [Hb] proved to be the most effective in minimizing intra-group variance and maximizing inter-group differences. Our platform can be extended to applications in which long-term metabolic flexibility is important to study, for example in tumor regression, recurrence following dormancy, and responses to cancer treatment.

Multicontrast Pocket Colposcopy Cervical Cancer Diagnostic Algorithm for Referral Populations.

Objective and Impact Statement. We use deep learning models to classify cervix images-collected with a low-cost, portable Pocket colposcope-with biopsy-confirmed high-grade precancer and cancer. We boost classification performance on a screened-positive population by using a class-balanced loss and incorporating green-light colposcopy image pairs, which come at no additional cost to the provider. Introduction. Because the majority of the 300,000 annual deaths due to cervical cancer occur in countries with low- or middle-Human Development Indices, an automated classification algorithm could overcome limitations caused by the low prevalence of trained professionals and diagnostic variability in provider visual interpretations. Methods. Our dataset consists of cervical images (n=1,760) from 880 patient visits. After optimizing the network architecture and incorporating a weighted loss function, we explore two methods of incorporating green light image pairs into the network to boost the classification performance and sensitivity of our model on a test set. Results. We achieve an area under the receiver-operator characteristic curve, sensitivity, and specificity of 0.87, 75%, and 88%, respectively. The addition of the class-balanced loss and green light cervical contrast to a Resnet-18 backbone results in a 2.5 times improvement in sensitivity. Conclusion. Our methodology, which has already been tested on a prescreened population, can boost classification performance and, in the future, be coupled with Pap smear or HPV triaging, thereby broadening access to early detection of precursor lesions before they advance to cancer.

Radiologic-pathologic analysis of increased ethanol localization and ablative extent achieved by ethyl cellulose.

Ethanol provides a rapid, low-cost ablative solution for liver tumors with a small technological footprint but suffers from uncontrolled diffusion in target tissue, limiting treatment precision and accuracy. Incorporating the gel-forming polymer ethyl cellulose to ethanol localizes the distribution. The purpose of this study was to establish a non-invasive methodology based on CT imaging to quantitatively determine the relationship between the delivery parameters of the EC-ethanol formulation, its distribution, and the corresponding necrotic volume. The relationship of radiodensity to ethanol concentration was characterized with water-ethanol surrogates. Ex vivo EC-ethanol ablations were performed to optimize the formulation (n = 6). In vivo ablations were performed to compare the optimal EC-ethanol formulation to pure ethanol (n = 6). Ablations were monitored with CT and ethanol distribution volume was quantified. Livers were removed, sectioned and stained with NADH-diaphorase to determine the ablative extent, and a detailed time-course histological study was performed to assess the wound healing process. CT imaging of ethanol-water surrogates demonstrated the ethanol concentration-radiodensity relationship is approximately linear. A concentration of 12% EC in ethanol created the largest distribution volume, more than eight-fold that of pure ethanol, ex vivo. In vivo, 12% EC-ethanol was superior to pure ethanol, yielding a distribution volume three-fold greater and an ablation zone six-fold greater than pure ethanol. Finally, a time course histological evaluation of the liver post-ablation with 12% EC-ethanol and pure ethanol revealed that while both induce coagulative necrosis and similar tissue responses at 1-4 weeks post-ablation, 12% EC-ethanol yielded a larger ablation zone. The current study demonstrates the suitability of CT imaging to determine distribution volume and concentration of ethanol in tissue. The distribution volume of EC-ethanol is nearly equivalent to the resultant necrotic volume and increases distribution and necrosis compared to pure ethanol.

Optimizing ethyl cellulose-ethanol delivery towards enabling ablation of cervical dysplasia.

In low-income countries, up to 80% of women diagnosed with cervical dysplasia do not return for follow-up care, primarily due to treatment being inaccessible. Here, we describe development of a low-cost, portable treatment suitable for such settings. It is based on injection of ethyl cellulose (EC)-ethanol to ablate the transformation zone around the os, the site most impacted by dysplasia. EC is a polymer that sequesters the ethanol within a prescribed volume when injected into tissue, and this is modulated by the injected volume and delivery parameters (needle gauge, bevel orientation, insertion rate, depth, and infusion rate). Salient injection-based delivery parameters were varied in excised swine cervices. The resulting injection distribution volume was imaged with a wide-field fluorescence imaging device or computed tomography. A 27G needle and insertion rate of 10 mm/s achieved the desired insertion depth in tissue. Orienting the needle bevel towards the outer edge of the cervix and keeping infusion volumes ≤ 500 µL minimized leakage into off-target tissue. These results guided development of a custom hand-held injector, which was used to locate and ablate the upper quadrant of a swine cervix in vivo with no adverse events or changes in host temperature or heart rate. After 24 h, a distinct region of necrosis was detected that covered a majority (> 75%) of the upper quadrant of the cervix, indicating four injections could effectively cover the full cervix. The work here informs follow up large animal in vivo studies, e.g. in swine, to further assess safety and efficacy of EC-ethanol ablation in the cervix.

Spiritual well-being and its association with health-related quality of life in primary brain tumor patients.

BACKGROUND: Spirituality can impact patients' attitudes and decisions about treatment and end-of-life care when coping with cancer. Previous studies documented health-related quality of life (HRQoL) and spiritual well-being (SWB) as positively correlated within a general cancer patient population, but little is known about their association in the primary brain tumor population. We sought to measure SWB in primary brain tumor patients and evaluate whether it was associated with HRQoL. METHODS: Six-hundred and six patients treated at The Preston Robert Tisch Brain Tumor Center at Duke between December 16, 2013 and February 28, 2014 with data in the PRoGREss registry are included in this retrospective analysis. Each patient completed the Functional Assessment of Chronic Illness Therapy-Spiritual Well-Being 12 (FACIT-Sp-12) and -Fatigue (FACIT-F), and the Functional Assessment of Cancer Therapy-General and -Brain (FACT-G and FACT-Br). RESULTS: Mean age was 49.1 years (SD = 13.5 years), male (N = 328, 54.1%), married (N = 404, 66.7%), at least college-educated (N = 381, 62.9%), and diagnosed with a high-grade glioma (N = 412, 68.0%). Multiple regression analyses were performed on both the FACT-G and the FACT-Br using the FACIT-Sp-12 sub-scales of Meaning/Peace and Faith, FACIT-F, belief in God or a higher power, prayer, gender, tumor grade, and Karnofsky Performance Status (KPS) as predictors. We found that greater SWB (measured by FACIT-Sp-12) was associated with better HRQoL (measured by FACT-G and FACT-Br; p < .0001). CONCLUSION: The association between reported SWB and reported improved HRQoL emphasizes the importance of spirituality in primary brain tumor patients, suggesting SWB must be considered in strategies to improve HRQoL.

Understanding the sources of errors in ex vivo Hsp90 molecular imaging for rapid-on-site breast cancer diagnosis.

Overexpression of heat shock protein 90 (Hsp90) on the surface of breast cancer cells makes it an attractive molecular biomarker for breast cancer diagnosis. Before a ubiquitous diagnostic method can be established, an understanding of the systematic errors in Hsp90-based imaging is essential. In this study, we investigated three factors that may influence the sensitivity of ex vivo Hsp90 molecular imaging: time-dependent tissue viability, nonspecific diffusion of an Hsp90 specific probe (HS-27), and contact-based imaging. These three factors will be important considerations when designing any diagnostic imaging strategy based on fluorescence imaging of a molecular target on tissue samples.

In Vivo Optical Metabolic Imaging of Long-Chain Fatty Acid Uptake in Orthotopic Models of Triple-Negative Breast Cancer.

Targeting a tumor's metabolic dependencies is a clinically actionable therapeutic approach; however, identifying subtypes of tumors likely to respond remains difficult. The use of lipids as a nutrient source is of particular importance, especially in breast cancer. Imaging techniques offer the opportunity to quantify nutrient use in preclinical tumor models to guide development of new drugs that restrict uptake or utilization of these nutrients. We describe a fast and dynamic approach to image fatty acid uptake in vivo and demonstrate its relevance to study both tumor metabolic reprogramming directly, as well as the effectiveness of drugs targeting lipid metabolism. Specifically, we developed a quantitative optical approach to spatially and longitudinally map the kinetics of long-chain fatty acid uptake in in vivo murine models of breast cancer using a fluorescently labeled palmitate molecule, Bodipy FL c16. We chose intra-vital microscopy of mammary tumor windows to validate our approach in two orthotopic breast cancer models: a MYC-overexpressing, transgenic, triple-negative breast cancer (TNBC) model and a murine model of the 4T1 family. Following injection, Bodipy FL c16 fluorescence increased and reached its maximum after approximately 30 min, with the signal remaining stable during the 30-80 min post-injection period. We used the fluorescence at 60 min (Bodipy60), the mid-point in the plateau region, as a summary parameter to quantify Bodipy FL c16 fluorescence in subsequent experiments. Using our imaging platform, we observed a two- to four-fold decrease in fatty acid uptake in response to the downregulation of the MYC oncogene, consistent with findings from in vitro metabolic assays. In contrast, our imaging studies report an increase in fatty acid uptake with tumor aggressiveness (6NR, 4T07, and 4T1), and uptake was significantly decreased after treatment with a fatty acid transport inhibitor, perphenazine, in both normal mammary pads and in the most aggressive 4T1 tumor model. Our approach fills an important gap between in vitro assays providing rich metabolic information at static time points and imaging approaches visualizing metabolism in whole organs at a reduced resolution.

Polymer-assisted intratumoral delivery of ethanol: Preclinical investigation of safety and efficacy in a murine breast cancer model.

Focal tumor ablation with ethanol could provide benefits in low-resource settings because of its low overall cost, minimal imaging technology requirements, and acceptable clinical outcomes. Unfortunately, ethanol ablation is not commonly utilized because of a lack of predictability of the ablation zone, caused by inefficient retention of ethanol at the injection site. To create a predictable zone of ablation, we have developed a polymer-assisted ablation method using ethyl cellulose (EC) mixed with ethanol. EC is ethanol-soluble and water-insoluble, allowing for EC-ethanol to be injected as a liquid and precipitate into a solid, occluding the leakage of ethanol upon contact with tissue. The aims of this study were to compare the 1) safety, 2) release kinetics, 3) spatial distribution, 4) necrotic volume, and 5) overall survival of EC-ethanol to conventional ethanol ablation in a murine breast tumor model. Non-target tissue damage was monitored through localized adverse events recording, ethanol release kinetics with Raman spectroscopy, injectate distribution with in vivo imaging, target-tissue necrosis with NADH-diaphorase staining, and overall survival by proxy of tumor growth. EC-ethanol exhibited decreased localized adverse events, a slowing of the release rate of ethanol, more compact injection zones, 5-fold increase in target-tissue necrosis, and longer overall survival rates compared to the same volume of pure ethanol. A single 150 µL dose of 6% EC-ethanol achieved a similar survival probability rates to six daily 50 µL doses of pure ethanol used to simulate a slow-release of ethanol over 6 days. Taken together, these results demonstrate that EC-ethanol is safer and more effective than ethanol alone for ablating tumors.

Exploiting heat shock protein expression to develop a non-invasive diagnostic tool for breast cancer.

Leveraging the unique surface expression of heat shock protein 90 (Hsp90) in breast cancer provides an exciting opportunity to develop rapid diagnostic tests at the point-of-care setting. Hsp90 has previously been shown to have elevated expression levels across all breast cancer receptor subtypes. We have developed a non-destructive strategy using HS-27, a fluorescently-tethered Hsp90 inhibitor, to assay surface Hsp90 expression on intact tissue specimens and validated our approach in clinical samples from breast cancer patients across estrogen receptor positive, Her2-overexpressing, and triple negative receptor subtypes. Utilizing a pre-clinical biopsy model, we optimized three imaging parameters that may affect the specificity of HS-27 based diagnostics - time between tissue excision and staining, agent incubation time, and agent dose, and translated our strategy to clinical breast cancer samples. Findings indicated that HS-27 florescence was highest in tumor tissue, followed by benign tissue, and finally followed by mammoplasty negative control samples. Interestingly, fluorescence in tumor samples was highest in Her2+ and triple negative subtypes, and inversely correlated with the presence of tumor infiltrating lymphocytes indicating that HS-27 fluorescence increases in aggressive breast cancer phenotypes. Development of a Gaussian support vector machine classifier based on HS-27 fluorescence features resulted in a sensitivity and specificity of 82% and 100% respectively when classifying tumor and benign conditions, setting the stage for rapid and automated tissue diagnosis at the point-of-care.

Optical Imaging of Glucose Uptake and Mitochondrial Membrane Potential to Characterize Her2 Breast Tumor Metabolic Phenotypes.

With the large number of women diagnosed and treated for breast cancer each year, the importance of studying recurrence has become evident due to most deaths from breast cancer resulting from tumor recurrence following therapy. To mitigate this, cellular and molecular pathways used by residual disease prior to recurrence must be studied. An altered metabolism has long been considered a hallmark of cancer, and several recent studies have gone further to report metabolic dysfunction and alterations as key to understanding the underlying behavior of dormant and recurrent cancer cells. Our group has used two probes, 2-[N-(7-nitrobenz-2-oxa-1, 3-diaxol-4-yl) amino]-2-deoxyglucose (2-NBDG) and tetramethyl rhodamine ethyl ester (TMRE), to image glucose uptake and mitochondrial membrane potential, respectively, to report changes in metabolism between primary tumors, regression, residual disease, and after regrowth in genetically engineered mouse (GEM)-derived mammospheres. Imaging revealed unique metabolic phenotypes across the stages of tumor development. Although primary mammospheres overexpressing Her2 maintained increased glucose uptake ("Warburg effect"), after Her2 downregulation, during regression and residual disease, mammospheres appeared to switch to oxidative phosphorylation. Interestingly, in mammospheres where Her2 overexpression was turned back on to model recurrence, glucose uptake was lowest, indicating a potential change in substrate preference following the reactivation of Her2, reeliciting growth. Our findings highlight the importance of imaging metabolic adaptions to gain insight into the fundamental behaviors of residual and recurrent disease. IMPLICATIONS: This study demonstrates these functional fluorescent probes' ability to report metabolic adaptations during primary tumor growth, regression, residual disease, and regrowth in Her2 breast tumors.

Simultaneous in vivo optical quantification of key metabolic and vascular endpoints reveals tumor metabolic diversity in murine breast tumor models.

Therapeutically exploiting vascular and metabolic endpoints becomes critical to translational cancer studies because altered vascularity and deregulated metabolism are two important cancer hallmarks. The metabolic and vascular phenotypes of three sibling breast tumor lines with different metastatic potential are investigated in vivo with a newly developed quantitative spectroscopy system. All tumor lines have different metabolic and vascular characteristics compared to normal tissues, and there are strong positive correlations between metabolic (glucose uptake and mitochondrial membrane potential) and vascular (oxygen saturations and hemoglobin concentrations) parameters for metastatic (4T1) tumors but not for micrometastatic (4T07) and nonmetastatic (67NR) tumors. A longitudinal study shows that both vascular and metabolic endpoints of 4T1 tumors increased up to a specific tumor size threshold beyond which these parameters decreased. The synchronous changes between metabolic and vascular parameters, along with the strong positive correlations between these endpoints suggest that 4T1 tumors rely on strong oxidative phosphorylation in addition to glycolysis. This study illustrates the great potential of our optical technique to provide valuable dynamic information about the interplay between the metabolic and vascular status of tumors, with important implications for translational cancer investigations.

Near-simultaneous quantification of glucose uptake, mitochondrial membrane potential, and vascular parameters in murine flank tumors using quantitative diffuse reflectance and fluorescence spectroscopy.

The shifting metabolic landscape of aggressive tumors, with fluctuating oxygenation conditions and temporal changes in glycolysis and mitochondrial metabolism, is a critical phenomenon to study in order to understand negative treatment outcomes. Recently, we have demonstrated near-simultaneous optical imaging of mitochondrial membrane potential (MMP) and glucose uptake in non-tumor window chambers, using the fluorescent probes tetramethylrhodamine ethyl ester (TMRE) and 2-N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl)amino)-2-deoxyglucose (2-NBDG). Here, we demonstrate a complementary technique to perform near-simultaneous in vivo optical spectroscopy of tissue vascular parameters, glucose uptake, and MMP in a solid tumor model that is most often used for therapeutic studies. Our study demonstrates the potential of optical spectroscopy as an effective tool to quantify the vascular and metabolic characteristics of a tumor, which is an important step towards understanding the mechanisms underlying cancer progression, metastasis, and resistance to therapies.