Abstract 644: Angiogenic Blood Vessels Reconfigure/ Attenuate Hypoxic Tumor Microenvironments In A Quantitative In Vitro Model

Abstract

Introduction: Angiogenesis is crucial in the spread of cancer cells, and hypoxic tumor microenvironment (TME) plays a vital role in its initiation. Hypoxia stimulates the release of pro-angiogenic factors, promoting the growth of new blood vessels towards the tumor, which further alters the TME. The variation of in vivo hypoxic TME have been studied recently. However, due to technical limitations such as highly invasive procedure, high cost, tedious process, and poor signal-to-noise ratio, it is challenging to perform quantitative oxygen sensing. Here we develop an advanced in vitro model directly investigating the interaction between a solid tumor and blood vessels for an extended period. Hypothesis: The angiogenic blood vessels can reconfigure and attenuate the hypoxic TME, which can be directly measured Methods: The model is built using a microfluidic device with a sealed microwell for 3D tumor spheroid culture (human colon cancer cell line, HCT116), and a microfluidic channel beneath the microwell for endothelium formation (human umbilical vein endothelial cell, HUVEC), connected by a small hole for interaction between the cell types. Oxygen sensitive fluorescence particles are distributed in the hydrogel matrix, and the widefield frequency domain fluorescence lifetime imaging microscopy (FD-FLIM) is exploited to reliably characterize the oxygen tension around the tumor spheroid with minimal sensitivity to ambient optical noise. Results: The oxygen tension of TME around the tumor spheroid within the distance of 0 to 0.7 mm rapidly decreases during tumor growth, from 15% at day 1 to less than 6% at day 14. The presence of endothelial cells slows down this decreasing rate and maintains it in a stable range, from 16% to 14%. The average oxygen tension difference between the two experiments, with and without co-culture of endothelial cells, is statistically significant after 5 days of observation (p<0.01). Conclusions: We develop a quantitative in vitro method to study the hypoxic TME for its dynamic pattern and as a target for cancer treatment. By observing the effect of angiogenesis on it, this method can aid in exploring optimal cancer management strategies, such as chemotherapy, immunotherapy, tailored anti-angiogenic agents and other targeted therapies.