Multicellular tumor spheroids- an effective in vitro model for understanding drug resistance in head and neck cancer

A hallmark of cancer is the ability to develop resistance against therapeutic agents. Therefore, developing effective in vitro strategies to identify drug resistance remains of paramount importance for treatment success. A way cancer cells achieve drug resistance is through the expression of efflux pumps that actively pump drugs out of the cells. To date, several studies have investigated the potential of using 3D multicellular tumor spheroids (MCSs) to assess drug resistance; however, a unified system that uses MCSs to differentiate between multi drug resistant (MDR) and non-MDR cells does not exist. In the present report, we have used MCSs obtained from post-diagnosed, pre-treated (PDPT) patient derived head and neck squamous cancer cells that often become treatment resistant, to develop an integrated approach combining clinical drug response and cytotoxicity screening, real-time drug uptake monitoring, and drug transporter activity assessment using flow cytometry in the presence and absence of their respective specific inhibitors. The present report shows a comparative response to MDR, drug efflux capability, and reactive oxygen species (ROS) activity to assess the resistance profile of PDPT patient-derived MCSs and two-dimensional cultures of the same set of cells. We show that MCSs serve as robust and reliable models for the clinical evaluation of drug resistance. Our proposed strategy can thus have potential clinical applicability for profiling drug resistance in cancers with unknown resistance profiles, which consequentially can indicate benefit from downstream therapy.