Membrane-derived particles shed by PSMA-positive cells function as pro-angiogenic stimuli in tumors

Cell membrane-derived particles (Mp) are rounded membrane-enclosed particles that are shed from tumor cells. Mp are formed from tumor membranes and are capable of tumor targeting and immunotherapeutic agents because they share membrane homology with parental cells; thus, they are under consideration as a drug delivery vehicle. Prostate-specific membrane antigen (PSMA), a transmembrane glycoprotein with enzymatic functionality, is highly expressed in Mp and extracellular vesicles (EV) from prostate cancer (PCa) with poor clinical prognosis. Although PSMA expression was previously shown in EV and Mp isolated from cell lines and from the blood of patients with high-grade PCa, no pathophysiological effects have been linked to PCa-derived Mp. Here, we compared Mp from PSMA-expressing (PSMA-Mp) and PSMA-non-expressing (WT-Mp) cells side by side in vitro and in vivo. PSMA-Mp can transfer PSMA and new phenotypic characteristics to the tumor microenvironment. The consequence of PSMA transfer to cells and increased secretion of vascular endothelial growth factor-A (VEGF-A), pro-angiogenic and pro-lymphangiogenic mediators, with increased 4E binding protein 1 (4EBP-1) phosphorylation.

Three-dimensional optoacoustic imaging of nailfold capillaries in systemic sclerosis and its potential for disease differentiation using deep learning

The autoimmune disease systemic sclerosis (SSc) causes microvascular changes that can be easily observed cutaneously at the finger nailfold. Optoacoustic imaging (OAI), a combination of optical and ultrasound imaging, specifically raster-scanning optoacoustic mesoscopy (RSOM), offers a non-invasive high-resolution 3D visualization of capillaries allowing for a better view of microvascular changes and an extraction of volumetric measures. In this study, nailfold capillaries of patients with SSc and healthy controls are imaged and compared with each other for the first time using OAI. The nailfolds of 23 patients with SSc and 19 controls were imaged using RSOM. The acquired images were qualitatively compared to images from state-of-the-art imaging tools for SSc, dermoscopy and high magnification capillaroscopy. The vascular volume in the nailfold capillaries were computed from the RSOM images. The vascular volumes differ significantly between both cohorts (0.216 ± 0.085 mm³ and 0.337 ± 0.110 mm³; p < 0.0005). In addition, an artificial neural network was trained to automatically differentiate nailfold images from both cohorts to further assess whether OAI is sensitive enough to visualize anatomical differences in the capillaries between the two cohorts. Using transfer learning, the model classifies images with an area under the ROC curve of 0.897, and a sensitivity of 0.783 and specificity of 0.895. In conclusion, this study demonstrates the capabilities of RSOM as an imaging tool for SSc and establishes it as a modality that facilitates more in-depth studies into the disease mechanisms and progression.

P166 How well does deep learning differentiate between optoacoustic and optical nailfold capillaroscopy images from patients with systemic sclerosis versus those from healthy controls?

Background

Nailfold capillaroscopy offers a non-invasive route to observation of systemic sclerosis (SSc)-related microvascular changes and is used routinely for inspection of the capillaries at the finger nailfold. The characteristic changes in capillary structure (increased capillary width, decreased capillary density and abnormal angiogenesis) are included in the 2013 classification criteria for SSc. Optoacoustic mesoscopy is a combination of optical and ultrasound imaging enabling a 3D perspective of capillaries at a similar resolution to commercial nailfold capillaroscopy systems. We have previously reported that quantitative measures of vascular volume and density extracted from optoacoustic images differ significantly between patients with SSc and healthy controls. The aim of this study was to determine whether an artificial neural network (deep machine learning) could correctly differentiate between images from patients with SSc and healthy controls.

Methods

Optoacoustic (3D, iThera, Germany) and ‘standard’ capillaroscopy images (2D, Optillia, Sweden) of the right and left ring finger nailfolds were acquired. Images were taken at the centre of the nailfold. Acquisition of the same capillaries was difficult in some cases. 2D, greyscale, maximum intensity projections were created from the 3D optoacoustic images. Capillaroscopy images were downsized to match the optoacoustic image resolution. For data augmentation purposes each image, from both the optoacoustic and capillaroscopy data sets, was sliced into multiple overlapping image sections of fixed size. Transfer learning was used to train the model on 'disease' classification (SSc vs control). The pre-trained neural networks learn general image features and subsequently, are fine-tuned on the image data to classify based on the previously learned features.

Results

Twenty four patients with SSc (19% female; median age 65 IQR [57-69]; duration of Raynaud’s phenomenon 18 [12-28] years; time since onset of first non-Raynaud’s feature 11 (5-18) years) and 19 controls (17% female; age 15 [39-55] years) took part in the study. Fifty random data splits were used to validate the model and showed an average classification accuracy of 0.81 ± 0.15, with an area under the ROC curve of 0.88 ± 0.13 for optoacoustic data. The classification specificity and sensitivity were 0.84 ± 0.22 and 0.77 ± 0.21 respectively for optoacoustic mesoscopy. Performing the same task on capillaroscopy images, achieved an average accuracy of 0.86 ± 0.12 (AUC: 0.92 ± 0.09).

Conclusion

Deep learning is able to achieve excellent differentiation between images from patients with SSc and controls for both optoacoustic and standard capillaroscopy. Limitations of the study include the relatively small participant numbers and direct comparison of the same capillaries not always being possible. Optoacoustic mesoscopy offers huge potential to increase our understanding of the microvasculature in SSc.

Disclosures

S. Nitkunanantharajah None. K. Haedicke Corporate appointments; KH is an employee of iThera. T.L. Moore None. J.B. Manning None. G. Dinsdale None. M. Berks None. D. Jüstel None. V. Ntziachristos None. C. Taylor None. M. Dickinson None. A. Herrick None. A.K. Murray None.

Cerenkov-Activated Sticky Tag for In Vivo Fluorescence Imaging

A big challenge in the clinical use of Cerenkov luminescence (CL) imaging is its low signal intensity, which is several orders of magnitude below ambient light. Consequently, highly sensitive cameras, sufficient shielding from background light, and long acquisition times are required. To alleviate this problem, we hypothesized a strategy to convert the weak CL signal into a stronger fluorescence signal by using CL-activated formation of nitrenes from azides to locally fix a fluorescent probe in tissue by the formation of a covalent bond. CL-activated drug delivery was also evaluated using the same azide chemistry. The specific delivery of the CL-activated drug to cancer cells could reduce systemic toxicity, which is a limitation in chemotherapy. Methods: A cyanine-class near-infrared fluorescent dye, Cy7, and doxorubicin were synthetically attached to polyfluorinated aryl azide to form Cy7 azide and DOX azide, respectively. Fibrosarcoma cells were incubated with ¹⁸F-FDG and exposed to Cy7 azide with subsequent fluorescence imaging. For CL-activated tagging in vivo, tumor-bearing mice were injected first with ⁹⁰Y-DOTA-RGD, targeting α_vβ₃ integrins, and then with the Cy7 azide. Fluorescence signal was imaged over time. Breast cancer cells were incubated with DOX azide and ⁶⁸Ga, after which cell viability was quantified using an assay. Results: CL photoactivation of Cy7 azide in vitro showed significantly higher fluorescence signal from ¹⁸F-FDG-treated than untreated cells. In vivo, CL photoactivation could be shown by using the tumor-specific, integrin-targeting ⁹⁰Y-DOTA-RGD and the localized activation of Cy7 azide. Here, localized CL-induced fluorescence was detected in the tumors and remained significantly higher over several days than in tumors without CL. We also established as a next step CL-activated drug delivery of DOX azide by showing significantly decreasing cell viability of breast cancer cells in a CL dose-dependent manner in vitro using CL photoactivation of DOX azide. Conclusion: We were able to develop a CL-activated "sticky tag" that converts the low CL signal into a stable and long-lasting, highly intense fluorescence signal. This fluorescent footprint of the radioactive signal might be clinically used for intraoperative surgery. The CL-targeted drug delivery strategy may potentially be used for dual-step targeted therapy.

Sonophore labeled RGD: a targeted contrast agent for optoacoustic imaging

Optoacoustic imaging is a rapidly expanding field for the diagnosis, characterization, and treatment evaluation of cancer. However, the availability of tumor specific exogenous contrast agents is still limited. Here, we report on a small targeted contrast agent for optoacoustic imaging using a black hole quencher^® (BHQ) dye. The sonophore BHQ-1 exhibited strong, concentration-dependent, optoacoustic signals in phantoms, demonstrating its ideal suitability for optoacoustic imaging. After labeling BHQ-1 with cyclic RGD-peptide, BHQ-1-cRGD specifically bound to α_vβ₃-integrin expressing glioblastoma cell spheroids in vitro. The excellent optoacoustic properties of BHQ-1-cRGD could furthermore be proven in vivo. Together with this emerging imaging modality, our sonophore labeled small peptide probe offers new possibilities for non-invasive detection of molecular structures with high resolution in vivo and furthers the specificity of optoacoustic imaging. Ultimately, the discovery of tailor-made sonophores might offer new avenues for various molecular optoacoustic imaging applications, similar to what we see with fluorescence imaging.

Lowering photosensitizer doses and increasing fluences induce apoptosis in tumor bearing mice

The objective of this study was to determine an optimal dose of photodynamic therapy (PDT) for inducing apoptotic tumor cells in vivo. In this context, mice bearing human tongue-squamous epithelium carcinomas were treated with various photosensitizer concentrations and fluences. Tumor apoptosis was imaged after 2 days via a self-designed DY-734-annexin V probe using near-infrared fluorescence (NIRF) optical imaging. Apoptosis was verified ex vivo via TUNEL staining. Apoptotic tumor cells were detected in vivo at a dose of 40 µg photosensitizer and a fluency of 100 J/cm(2). This is the lowest photosensitizer dose reported so far.

Multifunctional calcium phosphate nanoparticles for combining near-infrared fluorescence imaging and photodynamic therapy

Photodynamic therapy (PDT) of tumors causes skin photosensitivity as a result of unspecific accumulation behavior of the photosensitizers. PDT of tumors was improved by calcium phosphate nanoparticles conjugated with (i) Temoporfin as a photosensitizer, (ii) the RGDfK peptide for favored tumor targeting and (iii) the fluorescent dye molecule DY682-NHS for enabling near-infrared fluorescence (NIRF) optical imaging in vivo. The nanoparticles were characterized with regard to size, spectroscopic properties and uptake into CAL-27 cells. The nanoparticles had a hydrodynamic diameter of approximately 200 nm and a zeta potential of around +22mV. Their biodistribution at 24h after injection was investigated via NIRF optical imaging. After treating tumor-bearing CAL-27 mice with nanoparticle-PDT, the therapeutic efficacy was assessed by a fluorescent DY-734-annexin V probe at 2 days and 2 weeks after treatment to detect apoptosis. Additionally, the contrast agent IRDye® 800CW RGD was used to assess tumor vascularization (up to 4 weeks after PDT). After nanoparticle-PDT in mice, apoptosis in the tumor was detected after 2 days. Decreases in tumor vascularization and tumor volume were detected in the next few days. Calcium phosphate nanoparticles can be used as multifunctional tools for NIRF optical imaging, PDT and tumor targeting as they exhibited a high therapeutic efficacy, being capable of inducing apoptosis and destroying tumor vascularization.

Multiplexed in vivo fluorescence optical imaging of the therapeutic efficacy of photodynamic therapy

In our study we wanted to elucidate a time frame for in vivo optical imaging of the therapeutic efficacy of photodynamic therapy (PDT) by using a multiplexed imaging approach for detecting apoptosis and vascularization. The internalization of the photosensitizer Foslip(®) into tongue-squamous epithelium carcinoma cells (CAL-27) was examined in vitro and in vivo. For detecting apoptosis, annexin V was covalently coupled to the near-infrared dye DY-734 and the spectroscopic properties and binding affinity to apoptotic CAL-27 cells were elucidated. CAL-27 tumor bearing mice were treated with PDT and injected 2 days and 2 weeks thereafter with DY-734-annexin V. PDT-induced changes in tumor vascularization were detected with the contrast agent IRDye(®) 800CW RGD up to 3 weeks after PDT. A perinuclear enrichment of Foslip(®) could be seen in vitro which was reflected in an accumulation in CAL-27 tumors in vivo. The DY-734-annexin V (coupling efficiency 30-50%) revealed a high binding affinity to apoptotic compared to non-apoptotic cells (17.2% vs. 1.2%) with a KD-value of 20 nm. After PDT-treatment, the probe showed a significantly higher (p <0.05) contrast in tumors at 2 days compared to 2 weeks after therapy (2-8 h post injection). A reduction of the vascularization could be detected after PDT especially in the central tumor areas. To detect the therapeutic efficacy of PDT, a multiplexed imaging approach is necessary. A detection of apoptotic cells is possible just shortly after therapy, whereas at later time points the efficacy can be verified by investigating the vascularization.

Differential oncogene amplification in tumor cells from a patient treated with cisplatin and 5-fluorouracil

Peritoneal cells were derived from a patient (PK) with adenocarcinoma of the colon during the course of cisplatin/5-fluorouracil (5-FUra) treatment. Resistance to cisplatin and 5-FUra, characterized by a lack of response to chemotherapy and continued growth of the tumor, was concomitantly associated with a 2-4-fold increase in DNA copy number for dTMP synthase and dihydrofolate reductase. There was a corresponding amplification in DNA copy number of the c-myc (2X), H-ras (4X), and c-fos (15X) oncogenes. Cytogenetic studies revealed an iso (13q) chromosome, but failed to show any double minutes or homogeneously staining regions. In addition, drug-resistant tumor cells from PK and another patient (HG) displayed enhanced expression of dTMP synthase, c-fos and DNA polymerase beta when compared to normal colon tissue and the HCT8 human colon carcinoma cell line. These results suggest that elevated oncogene DNA and gene expression may be involved in the development of cisplatin resistance.