ALDH7A1 and neoplasm: 2024; Lorenzi et al. 2017; Carrillo 2018a). It would also be interesting to study free boundary problems for these PDE systems, along the lines of those considered in Byrne and Chaplain (1997); Lorenzi et al. (2020); Bertsch et al. (2010) to model tissue development and tumour growth, and consider related transmission problems modelling cell invasion through thin membranes, in the vein of Chaplain (2019); Ciavolella et al. (2024); Ciavolella and Perthame (2021); Giverso et al. (2022).