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.
Highlights
The multicellular tumor spheroid is an excellent in vitro model utilized in cancer biology and toxicology [1,2,3]
Spheroids generated on hanging drop array plates and nutator plates were significantly more chemoresistant to cisplatin (Figure 3A, 3B) compared to spheroids generated on ultra-low attachment plates
Following 72 hours of cisplatin treatment, both MCF7 and OVCAR8 spheroids generated on either nutator plates or hanging drop arrays, were more chemoresistant to cisplatin compared to spheroids generated on ultra-low attachment plates
Summary
The multicellular tumor spheroid is an excellent in vitro model utilized in cancer biology and toxicology [1,2,3]. The cell-cell interactions and cell-extracellular matrix interactions in spheroids are noted to significantly mimic in vivo cyto-architectural conditions in a manner which is more physiologically relevant when compared to two-dimensional monolayer cultures of cells. Gene expression profiles of cells grown in the three-dimensional microenvironment better mimic clinical conditions, when compared to monolayer cultures [1, 2, 4]. Improving the predictive potency of in vitro drug screens and enabling a stronger clinical efficacy prediction is of prime importance in several cancers, including breast and ovarian cancers [5]. The spheroid model has been an important therapeutic tool for positive selection of novel drug and biologic candidates for several cancers [3]
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