Three-Dimensional Imaging for Multiplex Phenotypic Analysis of Pancreatic Microtumors Grown on a Minipillar Array Chip

SIMPLE SUMMARY: Three-dimensional (3D) culture of tumor spheroids (TSs) within the extracellular matrix (ECM) recapitulates solid tumors in vivo. This microtumor model is particularly useful for multiplex phenotypic analysis, but requires tissue optical clearing (TOC) for 3D visualization. We developed a transfer-free 3D microtumor culture-to-3D visualization system using a minipillar array chip combined with the TOC method. Our method succeeded in improving immunostaining and optical transmission in each TS as well as the entire microtumor specimen. The utility of this method was demonstrated by showing phenotypic changes, such as increased levels of membrane protrusion, single-cell dissemination, and ECM remodeling, and changes in the expression of epithelial–mesenchymal transition–related proteins and drug-induced apoptosis in TSs of human pancreatic cancer cells co-cultured with cancer-associated fibroblasts and M2-type tumor-associated macrophages. ABSTRACT: Three-dimensional (3D) culture of tumor spheroids (TSs) within the extracellular matrix (ECM) represents a microtumor model that recapitulates human solid tumors in vivo, and is useful for 3D multiplex phenotypic analysis. However, the low efficiency of 3D culture and limited 3D visualization of microtumor specimens impose technical hurdles for the evaluation of TS-based phenotypic analysis. Here, we report a 3D microtumor culture-to-3D visualization system using a minipillar array chip combined with a tissue optical clearing (TOC) method for high-content phenotypic analysis of microtumors. To prove the utility of this method, phenotypic changes in TSs of human pancreatic cancer cells were determined by co-culture with cancer-associated fibroblasts and M2-type tumor-associated macrophages. Significant improvement was achieved in immunostaining and optical transmission in each TS as well as the entire microtumor specimen, enabling optimization in image-based analysis of the morphology, structural organization, and protein expression in cancer cells and the ECM. Changes in the invasive phenotype, including cellular morphology and expression of epithelial–mesenchymal transition-related proteins and drug-induced apoptosis under stromal cell co-culture were also successfully analyzed. Overall, our study demonstrates that a minipillar array chip combined with TOC offers a novel system for 3D culture-to-3D visualization of microtumors to facilitate high-content phenotypic analysis.