Metabolic response of lung cancer cells to radiation in a paper-based 3D cell culture system

Karen A Simon,Bobak Mosadegh,Kyaw Thu Minn,Matthew R Lockett,Marym R Mohammady,Diane M Boucher,Amy B Hall,Shawn M Hillier,Taturo Udagawa,Brenda K Eustace,George M Whitesides

doi:10.1016/j.biomaterials.2016.03.002

Abstract

This work demonstrates the application of a 3D culture system—Cells-in-Gels-in-Paper (CiGiP)—in evaluating the metabolic response of lung cancer cells to ionizing radiation. The 3D tissue-like construct—prepared by stacking multiple sheets of paper containing cell-embedded hydrogels—generates a gradient of oxygen and nutrients that decreases monotonically in the stack. Separating the layers of the stack after exposure enabled analysis of the cellular response to radiation as a function of oxygen and nutrient availability; this availability is dictated by the distance between the cells and the source of oxygenated medium. As the distance between the cells and source of oxygenated media increased, cells show increased levels of hypoxia-inducible factor 1-alpha, decreased proliferation, and reduced sensitivity to ionizing radiation. Each of these cellular responses are characteristic of cancer cells observed in solid tumors. With this setup we were able to differentiate three isogenic variants of A549 cells based on their metabolic radiosensitivity; these three variants have known differences in their metastatic behavior in vivo. This system can, therefore, capture some aspects of radiosensitivity of populations of cancer cells related to mass-transport phenomenon, carry out systematic studies of radiation response in vitro that decouple effects from migration and proliferation of cells, and regulate the exposure of oxygen to subpopulations of cells in a tissue-like construct either before or after irradiation.

Highlights

In the United States and many developed countries, the overall 5-year survival rate of a patient with lung cancer is estimated to be between 15 to 20 % [1, 2]
One-third of lung cancer patients are diagnosed at an advanced stage, and radiation therapy remains a preferred strategy for targeting tumor cells because these cells are known to possess compromised DNA repair machinery, and often proliferate at higher rates than normal cells [3,4,5]
While the ultimate goal of radiation therapy is cell death, cells can respond to ionizing radiation in three ways: (i) repairing the damage directly; (ii) undergoing cell cycle-arrest, which can lead to irreversible arrest; or (iii) inducing programmed cell death [9, 16, 17]

Summary

Introduction

In the United States and many developed countries, the overall 5-year survival rate of a patient with lung cancer is estimated to be between 15 to 20 % [1, 2]. One-third of lung cancer patients are diagnosed at an advanced stage, and radiation therapy remains a preferred strategy for targeting tumor cells because these cells are known to possess compromised DNA repair machinery, and often proliferate at higher rates than normal cells [3,4,5]. To support the metabolic needs of cells for oxygen (O2), cells should be no more than 150 – 200 μm away from a capillary [23,24,25]. Beyond this distance, cells receive inadequate concentrations of oxygen and other molecules (e.g., glucose, autocrine factors) [26]. Poorly-oxygenated cells, which are further from the blood vessels, cope with

Methods

Discussion

Conclusion