Chitosan-Based Thermoreversible Hydrogel as an in Vitro Tumor Microenvironment for Testing Breast Cancer Therapies

[Image: see text] Breast cancer is a major health problem for women worldwide. Although in vitro culture of established breast cancer cell lines is the most widely used model for preclinical assessment, it poorly represents the behavior of breast cancers in vivo. Acceleration of the development of effective therapeutic strategies requires a cost-efficient in vitro model that can more accurately resemble the in vivo tumor microenvironment. Here, we report the use of a thermoreversible poly(ethylene glycol)-g-chitosan hydrogel (PCgel) as an in vitro breast cancer model. We hypothesized that PCgel could provide a tumor microenvironment that promotes cultured cancer cells to a more malignant phenotype with drug and immune resistance. Traditional tissue culture plates and Matrigel were applied as controls in our studies. In vitro cellular proliferation and morphology, the secretion of angiogenesis-related growth factors and cytokines, and drug and immune resistance were assessed. Our results show that PCgel cultures promoted tumor aggregate formation, increased secretion of various angiogenesis- and metastasis-related growth factors and cytokines, and increased tumor cell resistance to chemotherapeutic drugs and immunotherapeutic T cells. This PCgel platform may offer a valuable strategy to bridge the gap between standard in vitro and costly animal studies for a wide variety of experimental designs.