In vivo Bioluminescence-Based Monitoring of Liver Metastases from Colorectal Cancer: An Experimental Model

Background: In this study we aimed to develop a new in vivo bioluminescence-based tool to monitor and to quantify colon cancer (CC) liver metastasis development. Methods: HCT 116 cells were transducted with pLenti6/V5-DEST-fLuc for constitutive expression of firefly luciferase. Infection was monitored analyzing endogenous bioluminescence using the IVIS Lumina II In vivo Imaging System and a positive clone constitutively expressing luciferase (HCT 116-fLuc) was isolated. HCT 116-fLuc cells were left untreated or treated with 1 μM GDC-0449, a Hedgehog pharmacological inhibitor. Moreover, 1 x 106 HCT 116-fLuc cells were implanted via intra-splenic injection in nude mice. Bioluminescence was analyzed in these mice every 7 days for 5 weeks. After that, mice were sacrificed and bioluminescence was analyzed on explanted livers. Results: We found that in vitro bioluminescence signal was significantly reduced when HCT 116-fLuc cells were treated with GDC-0449. Regarding in vivo data, bioluminescence sources consistent with hepatic anatomical localization were detected after 21 days from HCT 116-fLuc intrasplenic injection and progressively increased until the sacrifice. The presence of liver metastasis was further confirmed by ex-vivo bioluminescence analysis of explanted livers. Conclusions: Our in vitro results suggest that inhibition of Hedgehog pathway may hamper CC cell proliferation and impel for further studies. Regarding in vivo data, we set-up a strategy for liver metastasis visualization, that may allow follow-up and quantification of the entire metastatic process. This cost-effective technique would reduce experimental variability, as well as the number of sacrificed animals.