A bone marrow ECM mimicking, animal-component free hydrogel identifies TNTs as key mediators of druggable cell-cell and cell-ECM crosstalk in an animal replacement organoid model

Improved and low toxicity treatments are urgently required to treat cancers, however cancer drug development is hindered by high drug attrition rates. Lack of tractable, reproducible, and transferrable platforms are key impediments hindering cancer drug development. Here we develop a prototype ECM, Vitronectin-Alginate-Laminin (VAL), comprised of animal free components, in defined formulations. We perform an in-depth analysis of the physical, chemical, and biological parameters of VAL and using acute lymphoblastic leukaemia (ALL) as a paradigm, optimise development of VAL-mesenchymal stroma cells (MSC)-ALL organoids. We show engraftment of patient derived leukaemia samples within our MSC-VAL organoids and find that ALL-interactions with both ECM and MSC mediate leukaemia biology. Ultimately, we show tractability of our model to study cell-cell crosstalk – we apply our model to reveal formation of TNTs between both MSC and patient-derived ALL in cells that have escaped anti-leukaemia treatment. ### Competing Interest Statement The authors have declared no competing interest.