Hepatocytes direct the formation of a pro-metastatic niche in the liver.

The liver is the most common site of metastatic disease in gastrointestinal malignancies, including pancreatic ductal adenocarcinoma (PDAC). While this metastatic tropism may reflect mechanical trapping of tumor cells that enter the circulation, liver metastasis is also dependent, at least in part, on the formation of a “pro-metastatic” niche that supports tumor cell seeding and colonization in the liver. However, mechanisms that orchestrate the establishment of this niche are poorly understood. Here, we show that hepatocytes coordinate accumulation of myeloid cells and fibrosis within the liver, the two defining features of a pro-metastatic niche. Early during pancreatic tumorigenesis in mice, hepatocytes demonstrate activation of Signal Transducer and Activator of Transcription 3 (STAT3) signaling and increased production of serum amyloid A1 and A2 (SAA). Overexpression of SAA by hepatocytes also occurs in PDAC patients with liver metastases, and many patients with locally advanced and metastatic disease display elevated levels of circulating SAA. STAT3 activation in hepatocytes and the subsequent production of SAA are dependent on interleukin 6 (IL-6) that is released into the circulation by non-malignant cells that reside adjacent to malignant cells in the pancreas. Genetic ablation or blockade of components of IL-6/STAT3/SAA signaling in hepatocytes effectively prevents the establishment of a pro-metastatic niche and inhibits metastatic seeding in the liver. Collectively, our data reveal an intercellular network underpinned by hepatocytes that forms the basis for a pro-metastatic niche in the liver and identify new therapeutic targets for pancreatic cancer. RNA profiles of the liver of LSL-KrasG12D/+;LSL-Trp53R127H/+;Pdx-1-Cre (KPC) mice and control mice (LSL-Trp53R127H/+;Pdx-1-Cre (PC)) were generated using QuantSeq 3’ mRNA sequencing.