Imaging cancer response and resistance to therapy using the chick CAM and isolated perfused tumour

Drug-resistance is a major obstacle for the effective treatment of patients with high grade metastatic cancer. Currently, there is no satisfactory way to identify patients that will respond and those that will fail standard-of-care therapy. Positron emission tomography (PET) imaging offers a potential solution to this clinical problem through the non-invasive assessment of molecular processes that underpin drug-resistance. Using a multidisciplinary approach, we are developing pioneering new PET imaging agents to identify drug-resistant tumours (Fig. 1) [1-3]. Early detection of drug resistance will enable the selection of alternative therapies, thereby improving outcomes in this disease.

The chick CAM
A considerable limitation of current preclinical models of cancer drug resistance is the inability to recapitulate the complexity of the tumour microenvironment, evolving genetic landscape and tumour-immune cell interactions. Mouse models of cancer have shown wide-spread utility and adoption for both drug and imaging agent development. However, mouse models are expensive, have high maintenance and husbandry costs, and are subject to ethical issues surrounding animal welfare. Here, we will develop the chick chorioallantoic membrane (CAM) as an alternative, high-throughput method for the development of novel cancer imaging agents. The CAM is a highly vascularised extra-embryonic membrane of the chick embryo. The CAM can be accessed easily with minimal invasion to the embryo, enabling the growth of cultured cancer cell and patient-derived xenografts, complete with a co-opted vascular system [4].
The chick CAM is a well-established model for the assessment of anti-cancer drug efficacy. It has also been adapted to quantify tumour metabolism in a glioblastoma xenograft with PET [5]. This experimental model will therefore enable high throughput screening of novel radiotracers in a way analogous to standard mouse xenograft work but at the fraction of the time and cost.
The perfused tumour
Using the chick CAM as a vehicle for in vivo tumour growth and vascularisation, we will develop an entirely new model for the assessment of cancer therapies and novel radiotracers: the 'isolated perfused tumour'. The perfused tumour will have the biological complexity of in vivo mouse models of cancer, with the versatility, control and reproducibility of in vitro culture experiments. Based on the Langendorff isolated perfused rat heart, with which we have extensive experience [6-8], the chick CAM tumour will be excised and perfused through the large feeding vessels to allow precise control over the delivery of oxygen, energy substrates and drugs in an intact tumour for the very first time.
To exploit the power of the isolated perfused tissue apparatus that we have developed, we have constructed a triple-detector system around our perfusion rig which allows us to evaluate radiotracer selectivity, sensitivity and pharmacokinetics in the isolated perfused tumour. We have a parallel perfusion setup which works within a 9.4T NMR magnet which allows us to perform parallel spectroscopy experiments to assess tissue viability and metabolism [7]. Together, the chick CAM, the isolated perfused tumour and our assorted biophysical technologies will allow the evaluation of the complex tumour microenvironment with unprecedented precision using novel radiotracers developed to image tumour response and resistance to therapy.

Strains on the healthcare system in the UK create an acute need for finding more effective, efficient, safe, and accurate non-invasive imaging solutions for clinical decision-making, both in terms of diagnosis and prognosis, and to reduce unnecessary treatment procedures and associated costs. Medical imaging is currently undergoing a step-change facilitated through the advent of artificial intelligence (AI) techniques, in particular deep learning and statistical machine learning, the development of targeted molecular imaging probes and novel "push-button" imaging techniques. There is also the availability of low-cost imaging solutions, creating unique opportunities to improve sensitivity and specificity of treatment options leading to better patient outcome, improved clinical workflow and healthcare economics. However, a skills gap exists between these disciplines which this CDT is aiming to fill.

Consistent with our vision for the CDT in Smart Medical Imaging to train the next generation of medical imaging scientists, we will engage with the key beneficiaries of the CDT: (1) PhD students & their supervisors; (2) patient groups & their carers; (3) clinicians & healthcare providers; (4) healthcare industries; and (5) the general public. We have identified the following areas of impact resulting from the operation of the CDT.

- Academic Impact: The proposed multidisciplinary training and skills development are designed to lead to an appreciation of clinical translation of technology and generating pathways to impact in the healthcare system. Impact will be measured in terms of our students' generation of knowledge, such as their research outputs, conference presentations, awards, software, patents, as well as successful career destinations to a wide range of sectors; as well as newly stimulated academic collaborations, and the positive effect these will have on their supervisors, their career progression and added value to their research group, and the universities as a whole in attracting new academic talent at all career levels.

- Economic Impact: Our students will have high employability in a wide range of sectors thanks to their broad interdisciplinary training, transferable skills sets and exposure to industry, international labs, and the hospital environment. Healthcare providers (e.g. the NHS) will gain access to new technologies that are more precise and cost-efficient, reducing patient treatment and monitoring costs. Relevant healthcare industries (from major companies to SMEs) will benefit and ultimately profit from collaborative research with high emphasis on clinical translation and validation, and from a unique cohort of newly skilled and multidisciplinary researchers who value and understand the role of industry in developing and applying novel imaging technologies to the entire patient pathway.

- Societal Impact: Patients and their professional carers will be the ultimate beneficiaries of the new imaging technologies created by our students, and by the emerging cohort of graduated medical imaging scientists and engineers who will have a strong emphasis on patient healthcare. This will have significant societal impact in terms of health and quality of life. Clinicians will benefit from new technologies aimed at enabling more robust, accurate, and precise diagnoses, treatment and follow-up monitoring. The general public will benefit from learning about new, cutting-edge medical imaging technology, and new talent will be drawn into STEM(M) professions as a consequence, further filling the current skills gap between healthcare provision and engineering.

We have developed detailed pathways to impact activities, coordinated by a dedicated Impact & Engagement Manager, that include impact training provision, translational activities with clinicians and patient groups, industry cooperation and entrepreneurship training, international collaboration and networks, and engagement with the General Public.