High Engraftment and Metastatic Rates in Orthotopic Xenograft Models of Gastric Cancer via Direct Implantation of Tumor Cell Suspensions

Simple Summary Despite remarkable progress in treating early-stage gastric cancer (GC), the clinical outcomes for patients with advanced disease remain very poor. Tissue invasion and metastasis constitute the major causes of cancer-related deaths, including GC. This highlights the urgent need to develop animal models that can recapitulate these processes to develop novel therapeutic strategies. We developed a highly reproducible and cost-effective procedure to establish orthotopic GC xenografts showing high engraftment and metastatic rates via the direct implantation of tumor cell suspensions. Compared with the routine method to establish orthotopic xenograft models by engrafting intact tumor fragments, our approach significantly shortens the experimental timeline and allows for the flexible adjustment of the number of tumor cells implanted to control the rate of tumor progression. Both dose- and time-dependent progressions of tumor invasion and metastasis were nicely recapitulated in our model. Our work provides valuable tools for studying GC progression and metastasis and developing effective therapies.Abstract Although the implantation of intact tumor fragments is a common practice to generate orthotopic xenografts to study tumor invasion and metastasis, the direct implantation of tumor cell suspensions is necessary when prior manipulations of tumor cells are required. However, the establishment of orthotopic xenografts using tumor cell suspensions is not mature, and a comparative study directly comparing their engraftment and metastatic capabilities is lacking. It is unclear whether tumor fragments are superior to cell suspensions for successful engraftment and metastasis. In this study, we employed three GC cell lines with varying metastatic capacities to stably express firefly luciferase for monitoring tumor progression in real time. We successfully minimized the risk of cell leakage during the orthotopic injection of tumor cell suspensions without Corning Matrigel by systematically optimizing the surgical procedure, injection volume, and needle size options. Comparable high engraftment and metastatic rates between these two methods were demonstrated using MKN-45 cells with a strong metastatic ability. Importantly, our approach can adjust the rate of tumor progression flexibly and cuts the experimental timeline from 10-12 weeks (for tumor fragments) to 4-5 weeks. Collectively, we provided a highly reproducible procedure with a shortened experimental timeline and low cost for establishing orthotopic GC xenografts via the direct implantation of tumor cell suspensions.