Introduction/Aim
In Australia, colorectal cancer (CRC) is the third most commonly diagnosed cancer and the second commonest cause of cancer death. Advances in primary cancer treatment have led to the emergence of metastases as the major cause of cancer deaths. We sought to establish a novel method of murine CRLM induction to facilitate the study of different regions of the liver and tumour as well as the role of post hepatectomy liver regeneration and epithelial to mesenchymal transition (EMT) in tumour recurrence.
Methodology
25 CBA mice underwent general anaesthetic and laparotomy, 10,000 MoCR cells were injected into the hepatic parenchyma. Mice were culled over a period of about three weeks to assess tumour growth. Furthermore, 3 CBA mice underwent tumour direct injection (TDI) alone and 3 mice underwent TDI alongside 70% PH. 3 regions of liver tissue from a mouse that underwent TDI alone were collected for global and phosphoproteomic analysis; tumour (T), adjacent tumour (AT) and distant liver (DL) tissue.
Results
TDI successfully induced discrete tumours which increased in size over time. Tumour burden was significantly higher in the PH group compared to the TDI alone group (p=0.04). Ki67 staining was significantly greater in both the hepatocytes and the tumours cells in the PH group compared to the TDI alone group (p=0.008 and p=0.0376 respectively). Markers of EMT including Zeb-1 and Vimentin were expressed differentially between the liver, stroma and tumour. Post hepatectomy vimentin staining was significantly upregulated in the liver, compared to TDI alone (p=0.0197). Furthermore, proteomic analysis of T, AT and DL revealed that protein expression differs between these regions and several proteins associated with key signalling pathways such as the Wnt-ß-catenin were identified.
Conclusion
TDI induces discrete CRLM and PH is associated with significantly greater tumour growth. This preliminary data also indicates that PH upregulates EMT, a key process in metastatic progression.