Journal Article

Physical Characterization of Colorectal Cancer Spheroids and Evaluation of NK Cell Infiltration Through a Flow-Based Analysis

Bacchi, Francesco, Delprete, Cecilia, Cannas, Federica, Musmeci, Francesco, Gazzola, Daniele, Villa, Federico, Costa, Delfina, Sargenti, Azzurra, Pasqua, Simone, Bonetti, Simone, Cristaldi, Domenico Andrea, Poggi, Alessandro, Zocchi, Maria Raffaella

2020

Overview

To improve pathogenetic studies in cancer development and reliable preclinical testing of anti-cancer treatments, three-dimensional (3D) cultures, including spheroids, have been widely recognized as more physiologically relevant in vitro models of in vivo tumor behavior. Currently, the generation of uniformly sized spheroids is still challenging: different 3D cell culture methods produce heterogeneous populations in dimensions and morphology, that may strongly influence readouts reliability correlated to tumor growth rate or antitumor natural killer (NK) cell-mediated cytotoxicity. In this context, an increasing consensus claims the integration of microfluidic technologies within 3D cell culture, as the physical characterization of tumor spheroids is unavoidably demanded to standardize protocols and assays for in vitro testing. In this paper, we employed a flow-based method specifically conceived to measure weight, size and focused onto mass density values of tumor spheroids. These measurements are combined with confocal and digital imaging of such samples. We tested the spheroids of four colorectal cancer (CRC) cell lines that exhibit statistically relevant differences in their physical characteristics, even though starting from the same cell seeding density. These variations are seemingly cell line-dependent and associated with the number of growing cells and the degree of spheroid compaction as well, supported by different adenosine-triphosphate contents. We also showed that this technology can estimate the NK cell killing efficacy by measuring the weight loss and diameter shrinkage of tumor spheroids, alongside with the commonly used cell viability in vitro test. As the activity of NK cells relies on their infiltration rate, the in vitro sensitivity of CRC spheroids proved to be exposure time- and cell line-dependent with direct correlation to the cell viability reduction. All these functional aspects can be measured by the system and are documented by digital image analysis. In conclusion, this flow-based method potentially paves the way towards standardization of 3D cell cultures and its early adoption in cancer research to test antitumor immune response and set up new immunotherapy strategies.

• Publisher: Frontiers Media SA,Frontiers Media S.A
• Subject: Antigens / Antitumor activity / Cancer therapies / Cell culture / Cell Culture Techniques - methods / Cell cycle / Cell growth / Cell Proliferation / Cell Survival / Cell viability / Colorectal cancer / Colorectal carcinoma / Colorectal Neoplasms - immunology / Colorectal Neoplasms - pathology / Cytotoxicity / Flow Cytometry - methods / Fluorescent Antibody Technique, Indirect - methods / HT29 Cells / Humans / Image processing / Immune response / Immunity (Disease) / Immunology / Immunotherapy / Infiltration / Killer Cells, Natural - immunology / Lymphocytes, Tumor-Infiltrating - immunology / mass density / Metastases / Microfluidics / Microfluidics - methods / Natural killer cells / Physical characteristics / spheroid / Spheroids / Spheroids, Cellular - pathology / T cell receptors / Tumor cell lines / Tumors / weight