Molecular Signature Linked to Acute Phase Injury and Tumor Invasiveness in Small-for-Size Liver Grafts

Objective: We aimed to explore the precise molecular mechanism of early and invasive tumor growth in a small-for-size graft after liver transplantation and to identify the distinct molecular signature linked to acute-phase injury and late-phase tumor invasiveness. Summary Background Data: Acute phase small-for-size liver graft injury plays an important role in tumor recurrence after liver transplantation. For prevention of such recurrence, understanding of its underlying mechanism will be important in developing novel therapeutic strategies. Methods: An orthotopic rat liver transplantation model was applied using whole grafts and small-for-size (50%) grafts. The recipients were injected with hepatoma cell lines via the portal vein to mimic tumor recurrence after liver transplantation. Tumor invasive properties were compared between the tumor developed from small and whole graft. Gene signatures of acute phase graft injury (days 1 and 3) and late phase tumor recurrence (days 14 and 21) were screened using cDNA microarray analysis and further confirmed by quantitative RT-PCR. The potential gene candidate CXCL10 was singled out for further functional studies to investigate its role in tumor progression. Results: A number of genes linked to inflammatory responses and tumor invasiveness were found over-expressed in small-for-size liver grafts and/or tumors developed in small liver grafts by cDNA microarray screening. Real-time RT-PCR also confirmed that the gene CXCL10 was over-expressed not only in small-for-size graft at the early phase, but also in tumor from small-for-size graft at the late phase after liver transplantation. In vitro functional studies further confirmed that CXCL10 promoted tumor-invasion-related properties and tumor-associated macrophage activation. Conclusion: CXCL10 over-expression, the distinct gene signature of acute-phase graft injury and tumor invasiveness in small-for-size liver grafts, may contribute to early tumor recurrence after liver transplantation. CXCL10 and its downstream signals may be potential therapeutic targets in the prevention of tumor recurrence after liver transplantation using small-for-size graft.