Abstract
Glioblastoma (GBM) therapeutic resistance is driven in part by tumor-initiating, cancer stem cells (CSCs) which rely on complex interactions with the tumor microenvironment. Standard cell culture conditions fail to recapitulate the original tumor architecture or microenvironmental gradients, and are not designed to retain tumor cellular heterogeneity. We demonstrate a 3D culture system that supports long-term growth and expansion of tumor organoids derived directly from GBM specimens.(1) Tumor organoids grow for months and display regional heterogeneity with a rapidly dividing outer region of SOX2+, OLIG2+, and TLX+ cells surrounding a hypoxic core of primarily non-stem senescent cells and diffuse, heterogeneous, and rare quiescent CSCs. Unlike patient-matched sphere cultures, orthotopic transplantation of patient-derived organoids resulted in tumors strikingly similar to the parental tumor. Non-stem cells within organoids are sensitive to radiation therapy whereas directly adjacent CSCs are radioresistant, an example of granular therapeutic response previously only demonstrable in whole tumors. We have further developed and leveraged a method of 3D region-specific labeling of live CSCs within organoids to perform high-throughput functional screens for genes essential to glioblastoma survival within distinct niches. These niche-essential genes better reflect glioblastoma-lethal gene targets in vivo.(2) Our novel ex-vivo systems preserve phenotypically diverse stem and non-stem cell populations side-by-side amidst varying microenvironmental gradients similar to patient tumors, allowing exploration of new CSC biology. These methods and screening techniques are further applicable to a wide range of disease models that require a complex microenvironment to maintain physiologic relevance. (1)Hubert et. al. Cancer Research 2016, (2)Miller et. al. Nature 2017