New Liver Cancer Models Could Enable Precision Medicine

A team from Europe has created mouse models of liver cancer that could help overcome one of the biggest obstacles in doing drug research on this disease—being able to test against subtypes.

The team generated a suite of genetically-driven immunocompetent in vivo and matched in vitro hepatocellular carcinoma (HCC) models they say represent multiple features of human HCC, including clonal origin, histopathological appearance, and metastasis. They also integrated transcriptomic data from the mouse models with human HCC data and identified four common human–mouse subtype clusters. 

The report appeared in Nature and the lead author is Miryam Müller, PhD, of the Cancer Research UK Scotland Institute, Glasgow.

HCC is the most common form of primary liver cancer and a leading cause of cancer-related mortality worldwide. This is not because HCC has no discernible subtypes, but it has been tough to target them. Tyrosine kinase inhibitors (TKIs; such as sorafenib and lenvatinib) were the only first-line treatments for unresectable HCC until 2020. Thereafter, the IMbrave150 study (atezolizumab with bevacizumab) highlighted the potential of combination approaches with immune checkpoint inhibition (ICI) therapy.

The team first set out to generate a broad range of mouse models guided by the most commonly found genetic drivers of human HCC. Human HCC is thought to evolve from a hepatocytic clonal origin under specific conditions promoting carcinogenesis, in contrast to recently described non-malignant clonal expansion. This was achieved by introducing genetic alterations into adult mouse hepatocytes using conditional recombination technology and allowing the premalignant clones to evolve to HCC over time.

They then injected adult mice with a viral vector encoding Cre recombinase with a hepatocyte tropism due to its thyroxine-binding globulin (TBG) promoter, AAV8.TBG.cre. They report that this drove the recombination of endogenous floxed alleles in individual hepatocytes in an immunocompetent environment. AAV8 was titrated to a dose (6.4 × 10⁸ genomic copies (GC) per mouse) that resulted in solitary hepatocyte targeting at low frequency (approximately 1%) and was highly hepatocyte specific. 

Recombination occurred primarily in the first five days after injection, and was observed across all three hepatocyte zones, but was significantly different between male and female mice. This led to a lower tumor count and consequently extended survival in female mice after induction of HCC-related oncogenes. Furthermore, varying the induction dose or mutational burden affected the tumor occurrence and the speed of progression to the endpoint.

The majority of their models (83%) developed end-stage tumors within the study timeframe and most (69%) showed a tumor penetrance of higher than 50%. Notably, some combinations, such as MYC overexpression + Trp53 alteration, which induced HCC in some but not all previously described models, had very low to no tumor penetrance using this clonal evolution approach.

As is seen in actual patients, they observed intratumoral hemorrhaging in mice and/or rupture (bleeding) as well as metastatic spread to the lungs, which is one of the main metastatic sites in human HCC, together with bone and lymph nodes.