Abstract 3126: The secretome of colorectal cancer cell lines cultured in vitro is predictive for their growth and metastatic behavior in an orthotopic in vivo mouse model
Authors: Bersano Jacqueline , Lenhard Dorothee , Lashuk Kanstantsin , Oswald Eva , Schüler Julia 
Published: June 2022

Abstract
Metastatic disease in solid cancer in general and specifically in colorectal cancer (CRC) is still the main reason for a poor prognosis underlining the need for new therapeutic strategies. Furthermore, a dysregulated secretion is one major driver of cancer progression and invasion and therefore holds promise as a general therapeutic target for the treatment of metastases. The overall aim of this study is to gain a quantitative understanding of the CRC secretome to elucidate the influence of the microenvironment on selected players and vice versa the influence of the secretome in vitro and in vivo. In a first attempt to elucidate the role of secreted factors in colon cancer progression, we cultured 20 CRC cell lines (five PDX derived and 15 commercial lines) in 3D spheroid cultures and compared the secreted cytokine profile with the 2D culture conditions of the same CRC cell line panel. We analyzed 45 cytokines in duplicates by using a human specific magnetic bead-based assay. Based on the cluster analysis of those cytokine profiles we categorized the CRC lines into low metastatic, intermediate and highly metastatic lines. To validate this clustering in vivo we implanted one representative cell line of each cluster orthotopically in immune-compromised NSG mice (n=10 per line in two independent experiments) and followed tumor growth by optical imaging twice a week over the course of up to 50 days. Tumor growth and metastases were confirmed by histological examination and terminal ex vivo imaging of the organs. The murine and human cytokine profile of different organs and the serum of tumor bearing mice was determined as well. The predicted highly metastatic cell line HCT116 displayed a latency of 24 days post implantation: after that time tumor cells were detected via optical imaging not only at the implantation site, but as well in kidney, spleen, liver and lungs in 100% of the examined animals. The intermediate cell line HT29 had a latency of 38 days and showed tumor growth in colon and liver of all animals and lung metastases on 80% of the implanted mice. Mice bearing the PDX derived cell line 269, representing the low metastatic phenotype, had to be sacrificed 50 days post implant. Tumor cells were detected at the implantation site. Micro-metastases in liver and lung were detected in only 75% of the animals. The secretome pattern specific for an individual cell line was predictive for the metastatic potential in vivo in an orthotopic mouse model. Of note, none of the mentioned cell lines metastasized when implanted subcutaneously. The detailed analysis of the mouse and human cytokine profiles will help to elucidate the complex crosstalk between tumor cells and the tumor microenvironment. The modulation of individual signaling cascades in vitro and in vivo will help to gain a deeper understanding of the metastatic process thereby enabling the development of possible new therapies.
Citation Format: Jacqueline Bersano, Dorothee Lenhard, Kanstantsin Lashuk, Eva Oswald, Julia Schüler. The secretome of colorectal cancer cell lines cultured in vitro is predictive for their growth and metastatic behavior in an orthotopic in vivo mouse model [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 3126.