LAUSR

Abstract The tumor microenvironment is a complex system that plays a vital role in proliferation, invasion and metastasis. In this work, an oxygen concentration gradient microfluidic chip was designed to construct an in vitro model of tumor hypoxic microenvironment. The microfluidic chip was composed of two parts, one was a serpentine-shape channel for hypoxia reagent mix to generate oxygen gradient, the other part contained three parallel channels for the co-culture of cancer cells (Heap1-6 cells) and hepatic stellate cells (JS-1 cells). Using the microfluidic chip, oxygen gradient was created under the culture condition to simulate hypoxic tumor microenvironment in vivo. In the hypoxic gradient environment, the drug resistance of Hepa1-6 cells to paclitaxel and tirapazamine (TPZ) was studied and the potential molecular mechanism was supposed. The results showed that the concentration of oxygen gradient ranged from 2.3% to 16.7%. Under this hypoxic condition, the viability of co-cultured Hepa1-6 cells decreased significantly under TPZ intervention, while the Hepa1-6 cells expressed resistance to paclitaxel. The results of immunofluorescence assay showed that hypoxia and co-culture condition could promote the expression of TIMP-1 and TGF-β, which induced the activation of JS-1 cell and further enhanced the drug resistance of Hepa1-6 cell to paclitaxel.