Magnetic molding of tumor spheroids: emerging model for cancer screening

Jose E Perez,Claire Wilhelm,Irène Nagle

doi:10.1088/1758-5090/abc670

Abstract

Three-dimensional tissue culture, and particularly spheroid models, have recently been recognized as highly relevant in drug screening, toxicity assessment and tissue engineering due to their superior complexity and heterogeneity akin to the in vivo microenvironment. However, limitations in size control, shape reproducibility and long maturation times hinder their full applicability. Here, we report a spheroid formation technique based on the magnetic aggregation of cells with internalized magnetic nanoparticles. The method yields magnetic spheroids with high sphericity and allows fine-tuning the final spheroid diameter. Moreover, cohesive spheroids can be obtained in less than 24 h. We show the proof of concept of the method using the CT26 murine colon carcinoma cell line and how different cell proliferation and invasion potentials can be attained by varying the spheroid size. Additionally, we show how the spheroid maturation impacts cell invasion and doxorubicin penetrability, highlighting the importance of this parameter in drug screening and therapeutic applications. Finally, we demonstrate the capability of the method to allow the measurement of the surface tension of spheroids, a relevant output parameter in the context of cancer cell invasion and metastasis. The method can accommodate other cell lines able to be magnetically labeled, as we demonstrate using the U-87 MG human glioblastoma cell line, and shows promise in the therapeutic screening at early time points of tissue formation, as well as in studies of drug and nanoparticle tumor penetration.

Highlights

The path to drug implementation involves a vigorous screening process in order to determine drug efficacy on a specific target, and it is typically first carried out in vitro before moving onto in vivo animal testing
It is thought that the lack of these relevant physiological conditions in 2D cultures lead to a different protein expression, biodistribution of biomolecules and drug kinetics [4], and it is believed to be an important contributor to the low success rate in clinical drug screening [5]
Magnetic molding of tumor spheroids Magnetic cell labeling of CT26 cells translated to an iron loading dose of 8.1 ± 2.6 pg per cell after endocytosis (figure 1(a)), as determined by single-cell magnetophoresis

Summary

Introduction

The path to drug implementation involves a vigorous screening process in order to determine drug efficacy on a specific target, and it is typically first carried out in vitro before moving onto in vivo animal testing. The cell monolayer (2D) culture has been the model of choice in drug development due to its relatively easy implementation, low cost and reproducibility. Such a model lacks the intrinsic and relevant properties inherent to a three-dimensional (3D) tissue construct, such as cell heterogeneity, cell-cell signaling, cell-extracellular matrix interactions, tumor growth kinetics and hypoxia [2], as well as the highly relevant factor of therapeutic drug resistance [3], that altogether resemble in vivo tissue more closely. 3D models such as spheroids have emerged as superior representative and predictive models of in vivo events with the potential to facilitate drug advances by bridging the gap between 2D cultures and animal in vivo testing [4, 6,7,8]

Methods

Results

Discussion

Conclusion