Growth and in vivo stresses traced through tumor mechanics enriched with predator-prey cells dynamics.

Mechanical stress accumulating during growth in solid tumors plays a crucial role in the tumor mechanobiology. Stresses arise as a consequence of the spatially inhomogeneous tissue growth due to the different activity of healthy and cancer cells inhabiting the various districts of the tissue, an additional piling up effect, induced by stress transferring across the scales, contributing to determine the total stress occurring at the macroscopic level. The spatially inhomogeneous growth rates accompany nonuniform and time-propagating stress profiles, which constitute mechanical barriers to nutrient transport and influence the intratumoral interstitial flow, in this way deciding the starved/feeded regions, with direct aftereffects on necrosis, angiogenesis, cancer aggressiveness and overall tumor mass size. Despite their ascertained role in tumor mechanobiology, stresses cannot be directly appraised neither from overall tumor size nor through standard non-invasive measurements. To date, the sole way for qualitatively revealing their presence within solid tumors is ex vivo, by engraving the excised masses and then observing opening between the cut edges. Therefore, to contribute to unveil stresses and their implications in tumors, it is first proposed a multiscale model where Volterra-Lotka (predator/prey-like) equations describing the interspecific (environment-mediated) competitions among healthy and cancer cells are coupled with equations of nonlinear poroelasticity. Then, an experimental study on mice injected subcutaneously with a suspension of two different cancer cell lines (MiaPaCa-2 and MDA.MB231) was conducted to provide experimental evidences that gave qualitative and some new quantitative confirmations of the theoretical model predictions.