Phenotypic heterogeneity of 2D organoid reflects clinical tumor characteristics.

Unlike cancer cell lines, tumors and primary cultured cells exhibit phenotypic heterogeneity. Although methods for establishing organoids within three-dimensional (3D) gels are well-known, the growth is slower than that of two-dimensional (2D) cultured cells and many niche factors need to be added. In this study, we established primary cultured organoid in 2D culture (2D organoid; 2DO) in a reproducible manner and with clinical phenotypic heterogeneity. The 2DO contained cancer stem cells (CSCs) expressing CD44 and CD133. The addition of basic fibroblast growth factor and transforming growth factor-β as niche factors was necessary to establish the 2DO and maintain the CSC population. The established 2DO showed sufficient proliferation, and the culture could be transferred to the 3D culture. Morphological analysis of the xenograft induced by 2DO reflected parental tumor differentiation, and gene expression in the 2DO was similar to that in the parental tumor. In vitro drug sensitivity analysis using the 2DO reflected individual clinical courses. The 2DO is an in vitro personal cancer model, and the results of the drug sensitivity assessment may be useful for introducing clinical chemotherapy agents in personalized medicine.