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

耐药是高级别转移癌患者有效治疗的主要障碍。目前，还没有令人满意的方法来识别将响应的患者和那些将失败的标准治疗。正电子发射断层扫描（PET）成像提供了一个潜在的解决方案，通过非侵入性评估的分子过程，支持耐药性的临床问题。使用多学科方法，我们正在开发开拓性的新PET成像剂，以识别耐药肿瘤（图1）[1-3]。早期检测耐药性将使选择替代疗法，从而改善这种疾病的结果。鸡CAMA目前癌症耐药性的临床前模型的相当大的局限性是无法概括肿瘤微环境的复杂性，进化的遗传景观和肿瘤-免疫细胞相互作用。癌症的小鼠模型已经显示出广泛的实用性，并用于药物和成像剂的开发。然而，小鼠模型是昂贵的，具有高维护和饲养成本，并且受到围绕动物福利的伦理问题的影响。在这里，我们将开发鸡胚绒毛尿囊膜（CAM）作为一种替代，高通量的方法，用于开发新的癌症显像剂。CAM是鸡胚的高度血管化的胚外膜。CAM可以很容易地接近，对胚胎的侵袭最小，使培养的癌细胞和患者来源的异种移植物生长，并具有一个共同选择的血管系统[4]。鸡CAM是一个成熟的模型，用于评估抗癌药物的疗效。它也适用于用PET量化胶质母细胞瘤异种移植物中的肿瘤代谢[5]。因此，这种实验模型将使高通量筛选新的放射性示踪剂的方式类似于标准的小鼠异种移植工作，但在时间和成本的分数。灌注肿瘤使用鸡CAM作为车辆在体内肿瘤生长和血管化，我们将开发一个全新的模型，用于评估癌症治疗和新的放射性示踪剂：“孤立的灌注肿瘤”。灌注的肿瘤将具有体内小鼠癌症模型的生物学复杂性，具有体外培养实验的多功能性、控制性和再现性。基于Langendorff离体灌注大鼠心脏，我们有丰富的经验[6-8]，鸡CAM肿瘤将被切除并通过大的供血血管灌注，以首次精确控制氧气、能量底物和药物在完整肿瘤中的输送。为了利用我们开发的离体灌注组织装置的能力，我们在我们的灌注装置周围构建了三重检测器系统，其允许我们评估放射性示踪剂在分离的灌注肿瘤中的选择性、灵敏度和药代动力学。我们有一个平行的灌注设置，它在9.4T NMR磁体内工作，使我们能够进行平行的光谱实验，以评估组织活力和代谢[7]。鸡CAM、分离的灌注肿瘤和我们的各种生物物理技术将一起使用开发用于成像肿瘤反应和对治疗的抵抗的新型放射性示踪剂，以前所未有的精度评估复杂的肿瘤微环境。

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 CAMA 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 tumourUsing 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.