Comparative analysis of tumor spheroid generation techniques for differentialin vitrodrug toxicity

// Shreya Raghavan 1 , Pooja Mehta 1, * , Eric N. Horst 2, * , Maria R. Ward 1, * , Katelyn R. Rowley 2 , Geeta Mehta 1, 2, 3 1 Department of Materials Science and Engineering, University of Michigan, Ann Arbor, MI, USA 2 Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI, USA 3 Macromolecular Science and Engineering, University of Michigan, Ann Arbor, MI, USA * These authors have contributed equally to this work Correspondence to: Geeta Mehta, e-mail: mehtagee@umich.edu Keywords: ovarian cancer, breast cancer, high throughput, multicellular tumor spheroids, preclinical drug testing Received: December 01, 2015     Accepted: February 11, 2016     Published: February 24, 2016 ABSTRACT Multicellular tumor spheroids are powerful in vitro models to perform preclinical chemosensitivity assays. We compare different methodologies to generate tumor spheroids in terms of resultant spheroid morphology, cellular arrangement and chemosensitivity. We used two cancer cell lines (MCF7 and OVCAR8) to generate spheroids using i) hanging drop array plates; ii) liquid overlay on ultra-low attachment plates; iii) liquid overlay on ultra-low attachment plates with rotating mixing (nutator plates). Analysis of spheroid morphometry indicated that cellular compaction was increased in spheroids generated on nutator and hanging drop array plates. Collagen staining also indicated higher compaction and remodeling in tumor spheroids on nutator and hanging drop arrays compared to conventional liquid overlay. Consequently, spheroids generated on nutator or hanging drop plates had increased chemoresistance to cisplatin treatment (20-60% viability) compared to spheroids on ultra low attachment plates (10-20% viability). Lastly, we used a mathematical model to demonstrate minimal changes in oxygen and cisplatin diffusion within experimentally generated spheroids. Our results demonstrate that in vitro methods of tumor spheroid generation result in varied cellular arrangement and chemosensitivity.