A Rapid 3D Melanoma-Skin Organoid for High-Throughput Assessment of Tumor Dynamics and Drug Response.

Melanoma is the most aggressive type of skin cancer, driven by early invasion, phenotypic plasticity, and frequent resistance to targeted therapies. Although genomic profiling informs treatment selection, genotype alone often fails to predict therapeutic response, underscoring the need for rapid and physiologically relevant functional testing platforms. Here, we present a three-dimensional melanoma-skin organoid (mSO) model that integrates primary skin cells with melanoma cell lines in a self-assembling, high-throughput format. The spherical mSOs recapitulate native human skin architecture, including a stratified epidermis and a dermal-hypodermal core, while supporting melanoma growth within an appropriate tissue microenvironment. In this niche, melanoma cells display epidermal spreading in radial growth-like patterns, outward invasion, and transcriptional shifts toward a pro-invasive phenotype. Using live confocal imaging coupled with a custom automated image analysis pipeline, we quantitatively measured tumor growth, migration beyond the organoid boundary, and interactions between melanoma cells and normal melanocytes. The mSOs also captured genotype-specific drug responses: BRAF-mutant melanoma cells were sensitive to BRAF and MEK inhibition, whereas NRAS-mutant, BRAF-wild-type cells were resistant to BRAF inhibition but remained responsive to MEK inhibition. Altogether, our mSO platform combines architectural and functional complexity with experimental scalability, providing a robust framework for modeling melanoma progression and evaluating targeted therapeutic responses within a relevant skin microenvironment. In the future, adaptation of this system to include patient-derived tumor cells could support personalized therapeutic decision-making in melanoma.