ObjectivesTo develop an orthotopic xenografts model that can dynamically observe the growth of rectal cancer and lymphatic metastasis, and to preliminarily explore the feasibility of monitoring the growth and metastasis of rectal cancer by in vivo imaging system.MethodsAn orthotopic xenografts model was developed in nude mouse by rectal submucosal injection of red fluorescent protein-labeled human colorectal adenocarcinoma cell line HCT 116. Then, the fluorescence signal from cancer cells was collected at different time points by means of in vivo imaging system, and the growth and metastasis of cancer cells in the rectum of nude mice was observed in real time. Finally, the model was evaluated by pathology.ResultsFifty visualized nude mouse models of orthotopic implantation and lymphatic metastasis were successfully constructed. At 2-7 weeks after implantation, the fluorescent protein of tumor were observed in all nude mouse with in vivo imaging system. After the orthotopic implantation, the volume of the transplanted tumor grew with the extension of time, and the integrated density expanded gradually. The number of caudal mesenteric lymph node metastases, para-aortic lymph node metastases, liver metastases and lung metastases increased time-dependent. The results of histological study was consistent with depending on lymph nodes to express fluorescent proteins to determine metastasis.ConclusionsIt is reliable and feasible to visualize the orthotopic implantation and lymphatic metastasis model of nude mice. The in vivo imaging system is simple and effective for real-time, non-invasive and dynamic observation of the growth of orthotopic xenografts and lymphatic metastasis in nude mice.