O2169: Upregulated Pathways in Hepatoblastoma Vascular Invasion

Background: Hepatoblastoma (HB) is the most common liver cancer in children with survival rates of less than 50% in patients with high-risk disease, especially those with vascular invasion (VI). Given therapies are ineffective, better understanding of the biomarkers and biology of VI in HB is warranted.

Methods: Using imaging mass cytometry (IMC) we analyzed 18 pre-validated protein targets on formalin-fixed paraffin embedded (FFPE) samples. We performed immunohistochemistry (IHC) on primary and metastatic lesions from additional patients. RNA sequencing of our primary liver tumors and vascular sub-clones of the tumor were performed. Migration and scratch assays were performed after shRNA knockdown of Yap-1 and c-MYC.

Results: Protein expression of c-Myc and YAP-1 are increased as the tumor invades the neighboring blood vessel on IMC. IHC of additional patients demonstrated nuclear positivity of YAP-1 and c-Myc in metastatic lung lesions, compared to the negative nature of the primary liver tumor. RNA sequencing data showed that average gene expression of c-Myc and YAP-1 of the tumor in hepatic vein was 1.61 and 12.9 times, respectively, higher than the primary tumor. c-MYC and Yap-1 knocked down in HepT1 cells had 25% and 30% migrated cells compared to parental, respectively, after 48 hours (p=0.02). In scratch assays, 50% of c-Myc knocked down HepT1 cells migrated compared to parental at 24 hours (p=0.03).

Conclusion: YAP-1 and c-Myc had higher expression in HB as the tumor cells migrate into vasculature and metastasize. YAP-1 and c-Myc expression appear to play a role in vascular invasion that is maintained at metastatic lesions.