Abstract 5278: Intravital dual-colored visualization of colorectal liver metastasis formation in the living mice using two photon laser scanning microscopy

Abstract

Abstract Background and aim: Metastatic spread is the major cause of mortality in patients with colorectal cancer (CRC). Liver metastasis is the most frequent and thus the main therapeutic target in metastatic CRC patients. The mechanism of colorectal liver metastasis (CLM) is still poorly understood. In this study, we presented high-resolution images of dynamics of tumor-host interaction in liver metastasis model of the living mice using two photon laser scanning microscopy (TPLSM). We also visualized the formation of CLM from single cancer cells to micrometastatic colonies in the same mice by intravital TPLSM at several times. Materials and methods: Red fluorescent protein (RFP) expressing SL4 murine colorectal cancer cell line (RFP-SL4) and green fluorescent protein (GFP)-transgenic mice (GFP mouse) were used as syngeneic tumor model. RFP expressing HT29 human colorectal cancer cell line (RFP-HT29) and GFP nude mice (C57BL/6-BALB/c-nu/nu-EGFP) were used as xenogeneic tumor model. 1×106 RFP expressing cancer cells were injected into the spleen of GFP (nude) mice for an experimental liver metastasis model. Intravital TPLSM was performed by exteriorizing the liver lobe of living mice and fixing it with a solder lug terminal and an adhesive agent (organ stabilizing system, patent number: 2007-129723). Interval TPLSM was also performed for intravital TPLSM at several times in the same mice. Results: Viable cancer cells in the vital liver of living mice were successfully imaged at high-resolution in vivo real-time by TPLSM. Single cancer cells were arrested within hepatic sinusoids 2 hours after injection at a magnification of X600∼X1200. Platelet aggregation surrounding a single cancer cell was observed 2h after injection, indicating a phenomenon of tumor-cell induced platelet aggregation (TCIPA). Cancer cells were extravasated from hepatic sinusoid to Disse space 24h after injection. Protrusions of a Kupffer cell surrounding a cancer cell were observed, indicating that a Kupffer cell appears to be phagocytosing a cancer cell. RFP-SL4 were formed micrometastatic colonies with extensive stromal reaction. Liver metastasis of RFP-HT29 was observed as a clustering of micrometastatic nodules. Conclusions: Our advanced technique using both intravital and interval TLPSM enables a dynamic high-resolution imaging of not only tumor-host interaction in cancer metastasis, but also metastatic process from a single cancer cell to micrometastasis formation in the living animals. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 5278. doi:10.1158/1538-7445.AM2011-5278