LAUSR

The recrudescence of breast cancer can partly be attributed to poor understanding of the early steps and the mechanisms involved in breast cancer metastasis, especially how tumor inflammatory cells including tumor‐associated macrophages (TAM) affect invasion process. However, invasion‐related biological studies in traditional in vitro assays or in vivo models are challenging due to the arduousness in establishing models that precisely reproduce the tumor invasion environment. To this end, we proposed a juxtaposed dual‐layer cell‐loaded hydrogels biomimetic microfluidic system and formed monolayer size‐selective permeable vascular endothelial barriers besides the dual layer to mimic mammalian blood vessels. We clarified that in this system, TAM promoted the invasion of breast cancer cells, whereas breast cancer cells maintained the phenotype of TAM cells and promoted the differentiation of U937 cells into TAM. It formed a tumor–macrophage bidirectional crosstalk system. This system could be used for drug screening. So finally, through the calculation of the survival rate of breast cancer cells when cocultured with different macrophages under paclitaxel treatment, we analyzed the antagonism of tumor–macrophage bidirectional crosstalk on anticancer drugs.