One extraction tool for in vitro-in vivo extrapolation? SPME-based metabolomics of in vitro 2 2D, 3D, in vivo mouse melanoma models

Abstract Solid phase microextraction (SPME) in combination with high-resolution mass spectrometry (HRMS) was employed for the determination of metabolomic profile of mouse melanoma growth within in vitro 2D, in vitro 3D, and in vivo models. Such multi-model approach has never been investigated before. Due to the low-invasiveness of SPME, it was possible to perform time-course analysis, which allowed building time profile of biochemical reactions in the studied material. Such approach does not require the multiplication of samples as subsequent analyses are performed from the very same cell culture or from the same individual. SPME already reduces the number of animals required for experiment, therefore it is with good concordance with the 3Rs rule (replacement, reduction, refinement). Among tested models, higher number of compounds was found within the 2D cell culture model, while in vivo and 3D model had the lowest number of detected compounds. These results may be connected with a higher metabolic rate, as well as lower integrity of the 2D model comparing to the 3D in vitro model resulting in a lower number of compounds released into medium in the latter model. In terms of in vitro-in vivo extrapolation, the 2D model performed more similar to in vivo comparing to 3D, however it might have been due to the fact that only secreted to medium compounds were investigated. Thus, in further experiments to obtain full metabolome information, the intraspheroidal assessment or spheroid dissociation would be necessary.