Patient-derived xenograft (PDX) models of cancer, developed through injection of patient tumour cells into immunocompromised mice, have been widely adopted in preclinical studies, as well as in precision oncology approaches. However, the extent to which PDX models represent the underlying genetic diversity of a patient's tumour and the extent of on-going genomic evolution in PDX models are incompletely understood, particularly in the context of heterogeneous cancers such as non-small cell lung cancer (NSCLC). To investigate the depiction of intratumour heterogeneity by PDX models, we derived 47 new subcutaneous multi-region PDX models from 22 patients with primary NSCLC enrolled in the clinical longitudinal cohort study TRACERx. By analysing whole exome sequencing data from primary tumours and PDX models, we find that PDX establishment creates a genomic bottleneck, with 76% of PDX models being derived from a single primary tumour subclone. Despite this, multiple primary tumour subclones were capable of PDX establishment in regional PDX models, indicating that PDX libraries derived from multiple tumour regions can capture intratumour heterogeneity. Acquisition of somatic mutations continued during PDX model expansion, and was associated with APOBEC- or mismatch repair deficiency-induced mutational signatures in a subset of models. Overall, while NSCLC PDX models retain truncal genomic alterations, the absence of subclonal heterogeneity representative of the primary tumour is a major limitation. Our results emphasise the importance of characterising and monitoring intratumour heterogeneity in the context of pre-clinical cancer studies.

Purpose: To enable a preliminary assessment of the suitability of edge illumination (EI) x-ray phase contrast (XPC) micro x-ray computed tomography (micro-CT) to preclinical imaging. Specifically, to understand how different acquisition schemes and their combination with dedicated data processing affect contrast-to-noise ratio (CNR) and spatial resolution, while providing control over scan time and radiation dose delivery. Procedures: Deceased mice (n = 3) were scanned with an EI XPC micro-CT setup operated under different settings, leading to scan times between 18 h and 13 min. For the shortest scan, the entrance dose was measured with a calibrated PTW 23344 ion chamber. Different data processing methods were applied, retrieving either separate attenuation and phase images, or hybrid (combined attenuation and phase) images. A quantitative comparison was performed based on CNR and spatial resolution measurements for a soft tissue interface. Results: All phase-based images have led to a higher CNR for the considered soft tissue interface than the attenuation image, independent of scan time. The best relative CNR (a sixfold increase) was observed in one of the hybrid images. Spatial resolution was found to be connected to scan time, with a resolution of approximately 20 μm and 60 μm achieved for the longest and shortest scans, respectively. An entrance dose of approximately 300 mGy was estimated for the scan performed within 13 min. Conclusions: Despite their preliminary nature, our results suggest that EI XPC bears potential for enhancing the utility of preclinical micro-CT, and, pending further research and development, could ultimately become a valuable technique in this field.

Purpose In this work the performance of a compact multiresolution and multicontrast x‐ray phase system based on edge illumination is investigated. It has been designed for small animal imaging and with a limited footprint for ease of deployment in laboratories. Methods The presented edge illumination system is based on a compact microfocus tungsten x‐ray source combined with a flat panel detector. The source has a maximum output of 10 W when the minimum spot size of about 15 μm is used. The system has an overall length of 70 cm. A new double sample mask design, obtained by arranging both skipped and nonskipped configurations on the same structure, provides dual resolution capability. To test the system, we carried out computed tomography (CT) scans of a plastic phantom with different source settings using both single‐image and multi‐image acquisition schemes at different spatial resolutions. In addition, CT scans of an ex‐vivo mouse specimen were acquired at the best identified working conditions to demonstrate the application of the presented system to small animal imaging. Results We found this system delivers good image quality, allowing for an efficient material separation and improving detail visibility in small animals thanks to the higher signal‐to‐noise ratio (SNR) of phase contrast with respect to conventional attenuation contrast. The system offers high versatility in terms of spatial resolution thanks to the double sample mask design integrated into a single scanner. The availability of both multi‐ and single‐image acquisition schemes coupled with their dedicated retrieval algorithms, allows different working modes which can be selected based on user preference. Multi‐image acquisition provides quantitative separation of the real and imaginary part of the refractive index, however, it requires a long scanning time. On the other hand, the single image approach delivers the best material separation and image quality at all the investigated source settings with a shorter scanning time but at the cost of quantitativeness. Finally, we also observed that the single image approach combined with a high‐power x‐ray source may result in a fast acquisition protocol compatible with in‐vivo imaging.

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Patient-derived xenograft (PDX) models have become important models in cancer biology. They are thought to mimic tumor biology more closely than traditional cell lines as a consequence of their in vivo heterocellularity and cell-matrix interactions, their 3D architecture and their relatively recent derivation. The genomic fidelity of PDXs is integral to their applications in both basic research and in translational medicine. We derived multi-region PDX models from patients enrolled in TRACERx - a study of the evolutionary dynamics of non-small cell lung cancer (NSCLC) that uses a multi-region deep whole-exome sequencing (WES) approach - using more extensive spatial sampling to better understand the histological and genomic fidelity of the PDX approach. We transplanted regional NSCLC tumor tissue subcutaneously into immunocompromised NSG mice. 134 regions were attempted, resulting in 60 passagable xenografts (44.8%). Of these, 44 regional xenografts (32.8% of all regions) were NSCLC-derived, while 16 (11.9% of all regions) were B-cell lymphoproliferative disease. Multi-region sampling revealed heterogeneous success of PDX derivation between regions within individual patient tumors. There was correlation between PDX derivation and tumor purity by WES. Overall, NSCLC PDX models were established for 22 patients (50%; range 1-5 regional models per patient; Table 1). Histologically, broad similarity was observed between PDX models and corresponding patient tumor regions, although in a small number of models, variability was noted between the patient tumor and the corresponding PDX model, or during PDX passaging. PDXs were subjected to WES for comparison with matched patient tumor regions. Overall, our study demonstrates the feasibility of systematic multi-region PDX derivation and suggests that multiple spatial sampling of tumors could improve PDX take rates and generate PDXs that represent the intratumor diversity of heterogenous NSCLCs. Table 1. Engraftment rates of multiple spatial regions from non-small cell lung cancer tumors. Attempted NSCLC PDX B-Lymphoproliferations No Xenograft: Regions No Xenograft: Any Region LUAD 48 (21) 12 (7) 9 (7) 27 (10) LUSC 61 (17) 20 (11) 6 (5) 35 (4) Other 25 (6) 12 (4) 1 (1) 12 (1) TOTAL 134 (44) 44 (22) 16 (13) 74 (15) Citation Format: Robert E. Hynds, David R. Pearce, Ayse U. Akarca, Sophia Ward, Ariana Huebner, Oriol Pich, Gareth A. Wilson, Kate H. Gowers, Rebecca Towns, Assma Ben Aissa, Selvaraju Veeriah, Sergio A. Quezada, Mariam Jamal-Hanjani, Sam M. Janes, Nicholas McGranahan, David A. Moore, Teresa Marafioti, Charles Swanton. Multi-region patient-derived xenograft models from non-small cell lung cancer patients enrolled in lung TRACERx [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 3096.