Hypoxic Jumbo Spheroids On-A-Chip (HOnAChip): Insights into Treatment Efficacy

SIMPLE SUMMARY: Hypoxia is found in half of the solid cancers and is a major contributor to treatment resistance and promotion of metastasis, leading to shortened patient survival. No user-friendly in vitro preclinical tool exists to study natural chronic hypoxia. The aim of this study was to design a microfluidic device allowing easy culture, maintenance, treatment, and analysis of naturally hypoxic sarcoma spheroids. We confirmed that our jumbo spheroids (>750 µm) contained hypoxic cores, as they expressed the hypoxic marker protein Carbonic Anhydrase IX (CAIX). Quantification of DNA strand breaks from radiotherapy and a hypoxia pro-drug demonstrated hypoxia-dependent treatment responses. Our novel microfluidic device is versatile and convenient for both fundamental and preclinical research, to better understand and treat hypoxic tumors. ABSTRACT: Hypoxia is a key characteristic of the tumor microenvironment, too rarely considered during drug development due to the lack of a user-friendly method to culture naturally hypoxic 3D tumor models. In this study, we used soft lithography to engineer a microfluidic platform allowing the culture of up to 240 naturally hypoxic tumor spheroids within an 80 mm by 82.5 mm chip. These jumbo spheroids on a chip are the largest to date (>750 µm), and express gold-standard hypoxic protein CAIX at their core only, a feature absent from smaller spheroids of the same cell lines. Using histopathology, we investigated response to combined radiotherapy (RT) and hypoxic prodrug Tirapazamine (TPZ) on our jumbo spheroids produced using two sarcoma cell lines (STS117 and SK-LMS-1). Our results demonstrate that TPZ preferentially targets the hypoxic core (STS117: p = 0.0009; SK-LMS-1: p = 0.0038), but the spheroids’ hypoxic core harbored as much DNA damage 24 h after irradiation as normoxic spheroid cells. These results validate our microfluidic device and jumbo spheroids as potent fundamental and pre-clinical tools for the study of hypoxia and its effects on treatment response.