Biofabricated tumor microenvironments for studying colorectal cancer in vitro and in vivo.

e14689 Background: Microenvironmental mechanics have a tremendous effect on the progression, phenotype, and therapeutic response of cancer cells positioning it as a high-potential target for novel therapeutic development. Laboratory modeling of the microenvironment and its multitude of effects is imperative for developing new avenues of anti-cancer therapy that can target non-traditional vectors such as the extracellular matrix (ECM) and stromal cells. Researchers have developed in vitro models of the tumor microenvironment (TME) to meet this need. While in vitro modeling is an important step in therapeutic development, there are few studies that validate in vitro generated results to gold-standard in vivo models, and further, to patient-derived data. Previously, we have developed a model of the colorectal tumor microenvironment and found a connection between collagen ultrastructure and cancer cell phenotype. Using this characterized organoid model, we implant bioengineered TMEs into mice to track long-term growth and progression of cancer and compare our results to clinical biopsies. Methods: Tumor organoids are produced by combining stromal cells and type I collagen. Cancer cell spheroids are embedded into the organoid for long term observation. Organoids are either observed in vitro or implanted subcutaneously into mice for in vivo tracking. Results: Organoids retain structure and viability during long term culture in vitro and in vivo, and embedded cancer cells respond significantly differently depending on the architecture of the surrounding TME. Cancer cells assume a mesenchymal, invasive, and proliferative phenotype in unorganized TMEs, and revert to an epithelial phenotype in an ordered TME. In addition, analysis of biopsied tissue, across tumor grade, demonstrates a correlation between cancer cell phenotype and microenvironmental architecture. Conclusions: In all this is the first study to establish a connection between TME micro-structure and cancer cell phenotype consistently across three distinct research modalities. These results have the potential to pave the way for utilizing bioengineered microenvironmental models as therapeutic development platforms and for targeting TME micro-structure to control colorectal cancer cell progression.