Application of a 3D Hydrogel-based model to replace use of animals for passaging patient-derived xenografts

There is growing use of patient-derived xenograft (PDX) models, whereby patient tumours are implanted subcutaneously in immunodeficient animals. Such models are more refined than standard cancer models due to better representation of the heterogeneity of disease and drug response observed in the clinic. However, such close-to-patient cells cannot be grown in standard culture and are maintained in vivo via regular passage, using large numbers of animals.
At a conservative estimate, 1000 PDX models are being derived and passaged at any one time. We intend to investigate an in vitro 3D peptide hydrogel system to replace use of animals for passaging these cells; if only 2 animals are being used to maintain each model currently being passaged, and passage takes place once every 6 weeks, this equates to 16,000 animals per year which would no longer be used, thus reducing the numbers of animals used for this purpose.
The peptide hydrogel system allows formation of a fully defined, stable, bespoke nanofiber matrix, with dimensionality similar to native ECM and relevant bioactive ECM motifs/glycans. In ongoing NC3Rs-funded research it is being used to develop a human breast tissue model. Our main objectives are to extend this research by investigating this novel culture system's ability to support the growth of PDX-derived primary breast cancer cells outside of animals; determine the influence of modifications to the systems associated with the breast cancer microenvironment e.g. addition of specific extracellular matrix components or stromal cells such as cancer-associated fibroblasts; and verify maintenance of genotype and phenotype of the cancer cells over passage. In addition, to ensure widespread adoption and maximise impact, we will investigate the ability of the system to be scaled-up for generating larger numbers of cells for downstream applications and for cells within the hydrogel to be cryopreserved for shipment to other laboratories.