A physiologically relevantin vitro3D melanoma skin model for targeted therapy assessment

Melanoma progression, regression, dormancy, and drug resistance involve a dynamic interplay between the tumor mass, dermal and epidermal cells, extracellular matrix (ECM), and the administered therapeutic agent. Understanding the mechanisms behind drug and melanoma interactions as well as the possible collateral effect on the surrounding healthy tissue could improve patient outcomes. To mechanistically unravel these complex interactions in melanoma, there is a need to develop realistic preclinicalin vitromodels; however, current melanoma models fail to replicate not only drug-cell, but also cell-cell, and cell-ECM interactions. Here, a physiologically relevant scaffold-free 3D melanoma model that mimics the morphological and functional features of the melanoma lesion was developed and assessed using an approved therapeutic agent. For this, ECM-coated fibroblasts were assembled with BRAF+ melanoma spheroids to generate the dermis followed by keratinocytes addition and differentiation to form the epidermis. Vemurafenib (Vem), a BRAF inhibitor (BRAFi), was evaluated for its efficacy on 2D melanoma cells, spheroids, and 3D scaffold-free melanoma models. Reduced cellular viability across all models demonstrated the potency of Vem in inhibiting BRAF+ melanoma. In spheroid-only and 3D melanoma skin models, Vem significantly reduced tumor size; however, spheroid-only models exhibited a slightly enhanced tumor shrinkage compared to spheroids embedded within skin models. Analysis of ECM-related genes showed a tendency to be downregulated in melanoma skin compared to healthy skin models, which was partially recovered post-Vem application, indicating significant influence of both the tumor and BRAFi in remodelling of the tumor microenvironment. Collectively, the developed skin model bridges the gap between 2D cultures, conventional spheroids, and complex patient-derived tumors. In future, the developed models can be utilized for personalized drug screenings to enhance translational potential of targeted therapies in multiple skin cancer subtypes.