A vascularized in vivo melanoma model suitable for metastasis research of different tumor stages using fundamentally...

Although 2D cancer models have been the standard for drug development, they don't resemble in vivo properties adequately. 3D models can potentially overcome this. Bioprinting is a promising technique for more refined models to investigate central processes in tumor development such as proliferation, dormancy or metastasis. We aimed to analyze bioinks, which could mimic these different tumor stages in a cast vascularized arteriovenous loop melanoma model in vivo. It has the advantage to be a closed system with a defined microenvironment, supplied only with one vessel-ideal for metastasis research. Tested bioinks showed significant differences in composition, printability, stiffness and microscopic pore structure, which led to different tumor stages (Matrigel and Alg/HA/Gel for progression, Cellink Bioink for dormancy) and resulted in different primary tumor growth (Matrigel significantly higher than Cellink Bioink). Light-sheet fluorescence microscopy revealed differences in vascularization and hemorrhages with no additional vessels found in Cellink Bioink. Histologically, typical human melanoma with different stages was demonstrated. HMB-45-positive tumors in progression inks were infiltrated by macrophages (CD163), highly proliferative (Ki67) and metastatic (MITF/BRN2, ATX, MMP3). Stainings of lymph nodes revealed metastases even without significant primary tumor growth in Cellink Bioink. This model can be used to study tumor pathology and metastasis of different tumor stages and therapies.