Microfluidic and organ-on-a-chip approaches to model the tumor microenvironment

The tumor microenvironment (TME) is a complex ecosystem that involves cancer cells, immune and stromal cells, in addition to extracellular matrix and secreted factors. The interactions within this complex ecosystem regulate tumor cell phenotypes and direct cancer progression, making their understanding essential for advancing our knowledge of cancer biology and developing innovative treatments. Since standard culture conditions cannot account for the complexity of the TME, organ-on-a-chip (OOC) technologies have been developed to fill this need. Here, we describe the recent advances in OOCs designed to improve in vitro models of the TME by controlling the physical, chemical, geometrical, and biological environment of tumor cells. We begin with studies that leverage OOCs to understand cancer biology, followed by a description of works that test drug effects within the TME. Finally, we discuss future avenues for development that will enhance the interest of OOCs for diverse applications, including clinical testing.