Microdroplet-based 3D gastric cancer model for evaluation of drug resistance

摘要

Gastric cancer is aggressive malignant tumor with high incidence and mortality in worldwide despite the recent advances in anti-cancer drugs.1 According to the morphological features, Lauren's classification distinguishes two types of gastric cancer, intestinal and diffuse types. Since diffuse- and intestinal-type gastric cancers show distinctly different clinicopathological features, new strategy for the cancer therapy depending on the two pathological variants of gastric cancer is necessary in in vitro preclinical models. 1 For advanced in vitro preclinical model, we performed droplet-based microfluidics to construct and characterize in vitro 3D gastric cancer model depending on two different types. To evaluate proposed 3D gastric cancer models, we confirmed cell morphology in ECM bead, and changes in expression of drug resistance-related protein, as well as drug resistance against anticancer drug, 5-fluorouracil (5-FU). The generation of 3D microbeads, consisting of cells embedded in an extracellular matrix (ECM), was carried out in flow-focusing device. To prevent ECM gelation during droplet formation, the flow-focusing device was maintained below 10°C. The oil and the ECM solution with gastric cancer cells were injected as a continuous phase and the disperse phase, respectively. AGS (intestinal type) and HS746T (diffuse type) were utilized in this system for realization of two different types of gastric cancer. The cell morphology observed through F-actin and nucleus staining and viability was examined by LIVE/DEAD cell staining. For further investigations, we performed the chemoresistance against 5-FU using WST-1 cell proliferation assay, and mRNA and protein expression of K-catenin was examined by RT-qPCR and western blot. To construct 3D gastric cancer model, we fabricated ECM microbead by flow-focusing technique to make size-controllable microbeads. We identified high cell viability after 7 days through LIVE/DEAD cell staining. The two different gastric cancer cell lines displayed different phenotypes in collagen bead. AGS represents spheroid formation with expansive growth. On the other hand, HS746T shows a single cell migration with infiltrative growth pattern, and consists of scattered cells.2 Expression of SS-catenin is differently expressed in 2D and 3D culture. Interestingly, tower SS-catenin protein expression was associated with lack of histological response to chemotherapy, and with resistance to 5-FU in gastric cancer. Conclusively, we developed in vitro 3D gastric cancer model system for analysis and confirmation of morphology, and drug resistance in ECM beads. Our results suggest that in vitro 3D models of gastric cancer represent a biologically relevant platform for studying gastric cancer cell biology, tumorigenesis, and for accelerating the development of novel therapeutic targets. We believe that the microdroplet-cancer model is highly suitable to prove useful in high-throughput drug testing and screening for preclinical 3D cell culture platform.