Abstract 3707: 2D organoid (2DO) as human tumor model for predicting therapeutic effect of anti-cancer drugs

Primary cultured cells derived from an individual patient’s tumor have phenotypic heterogeneity unlike established cancer cell lines. We established organoid in two-dimensional (2D) culture with the reproducibility of clinical phenotypic heterogeneity as a human tumor model, named isolated tumor-derived cancer cells (iCCs). The success rate of iCC growth in vitro was 100%, passage was 90%, and establishment of a xenograft model from iCC was 80%. Established 2DO can proliferate well, and are easier to use in several assays compared with reported organoid in 3D culture. However, established 2DO also can be easily cultured in a 3D culture system. iCC populations were analyzed by flow cytometry. Most iCCs expressed epithelial cell adhesion molecule (EpCAM), and the high- and low-expressing CD44 groups were identified. Seral markers were examined, and we reviled that TRA1-81-positive cells in the high-expressing CD44 group were necessary for replicating clinical tumor heterogeneity. Moreover, basic fibroblast growth factor (bFGF) was necessary to keep TRA1-81-positive cells. Next, we did anticancer drug assay using iCCs from 10 patients and predicted the clinical efficacy of drugs. Six patients received chemotherapy after their surgery, and four patients of them had distant metastases. The in vitro sensitivity was compared to clinical outcomes (RECIST criteria) in four patients that all had distant metastases. The concentration of anti-cancer drugs was set as estimated concentration in human tissue. In the examination using 5-FU and oxaliplatin, the survival rates of iCCs were more than 85% in one progressive disease (PD) patient. The survival rates of iCCs were less than 83% in three stable disease (SD) patients (median, 70%). The survival rates were also less than 83% in two patients who underwent adjuvant chemotherapy with no recurrence (median 70%). After 3 months chemotherapy, PD patient’s cell survival rates were more than 85%, and SD patient’s cell survival rates were less than 83%. After 6 months chemotherapy, PD patient’s cell survival rates were more than 81%, and SD patient’s cell survival rates were less than 75%. Therefore, the cut-off value was considered to be 83-85% for 3 months to keep SD, and 75-80% for 6 months. However, more examination is need to develop a prediction model we can use as a clinical application. In conclusion, our primary culture model may be a novel tool as a human tumor model with tumor heterogeneity, and it will be used to predict therapeutic effect of anti-cancer drugs in the clinical field. Citation Format: Shiki Fujino, Norikatsu Miyoshi, Kazuhiro Saso, Masaru Sasaki, Masayoshi Yasui, Masayuki Ohue, HIdekazu Takahashi, Naotsugu Haraguchi, Chu Matsuda, Taishi Hata, Tsunekazu Mizushima, Masaki Mori, Yuichiro Doki. 2D organoid (2DO) as human tumor model for predicting therapeutic effect of anti-cancer drugs [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 3707.