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

The liver is the most common site of metastatic disease1. Although this metastatic tropism may reflect the mechanical trapping of circulating tumour cells, liver metastasis is also dependent, at least in part, on the formation of a 'pro-metastatic' niche that supports the spread of tumour cells to the liver2,3. The mechanisms that direct the formation of this niche are poorly understood. Here we show that hepatocytes coordinate myeloid cell accumulation and fibrosis within the liver and, in doing so, increase the susceptibility of the liver to metastatic seeding and outgrowth. During early pancreatic tumorigenesis in mice, hepatocytes show activation of signal transducer and activator of transcription 3 (STAT3) signalling and increased production of serum amyloid A1 and A2 (referred to collectively as SAA). Overexpression of SAA by hepatocytes also occurs in patients with pancreatic and colorectal cancers that have metastasized to the liver, and many patients with locally advanced and metastatic disease show increases in circulating SAA. Activation of STAT3 in hepatocytes and the subsequent production of SAA depend on the release of interleukin 6 (IL-6) into the circulation by non-malignant cells. Genetic ablation or blockade of components of IL-6-STAT3-SAA signalling prevents the establishment of a pro-metastatic niche and inhibits liver metastasis. Our data identify an intercellular network underpinned by hepatocytes that forms the basis of a pro-metastatic niche in the liver, and identify new therapeutic targets.

Efficient engineering of human and mouse primary cells using peptide-assisted genome editing.

Simple, efficient and well-tolerated delivery of CRISPR genome editing systems into primary cells remains a major challenge. Here we describe an engineered Peptide-Assisted Genome Editing (PAGE) CRISPR-Cas system for rapid and robust editing of primary cells with minimal toxicity. The PAGE system requires only a 30-min incubation with a cell-penetrating Cas9 or Cas12a and a cell-penetrating endosomal escape peptide to achieve robust single and multiplex genome editing. Unlike electroporation-based methods, PAGE gene editing has low cellular toxicity and shows no significant transcriptional perturbation. We demonstrate rapid and efficient editing of primary cells, including human and mouse T cells, as well as human hematopoietic progenitor cells, with editing efficiencies upwards of 98%. PAGE provides a broadly generalizable platform for next-generation genome engineering in primary cells.

Tumor-Derived CCL2 Mediates Resistance to Radiotherapy in Pancreatic Ductal Adenocarcinoma.

PURPOSE: Local tumor growth is a major cause of morbidity and mortality in nearly 30% of patients with pancreatic ductal adenocarcinoma (PDAC). Radiotherapy is commonly used for local disease control in PDAC, but its efficacy is limited. We studied the impact of selectively intervening on radiotherapy-induced inflammation as an approach to overcome resistance to radiotherapy in PDAC. EXPERIMENTAL DESIGN: PDAC cell lines derived from primary pancreatic tumors arising spontaneously in KrasLSL-G12D/+;Trp53LSL-R172H/+;Pdx-1 Cre mice were implanted into syngeneic mice and tumors were focally irradiated using the Small Animal Radiation Research Platform (SARRP). We determined the impact of depleting T cells and Ly6C+ monocytes as well as inhibiting the chemokine CCL2 on radiotherapy efficacy. Tumors were analyzed by flow cytometry and IHC to detect changes in leukocyte infiltration, tumor viability, and vascularity. Assays were performed on tumor tissues to detect cytokines and gene expression. RESULTS: Ablative radiotherapy alone had minimal impact on PDAC growth but led to a significant increase in CCL2 production by tumor cells and recruitment of Ly6C+CCR2+ monocytes. A neutralizing anti-CCL2 antibody selectively inhibited radiotherapy-dependent recruitment of monocytes/macrophages and delayed tumor growth but only in combination with radiotherapy (P < 0.001). This antitumor effect was associated with decreased tumor proliferation and vascularity. Genetic deletion of CCL2 in PDAC cells also improved radiotherapy efficacy. CONCLUSIONS: PDAC responds to radiotherapy by producing CCL2, which recruits Ly6C+CCR2+ monocytes to support tumor proliferation and neovascularization after radiotherapy. Disrupting the CCL2-CCR2 axis in combination with radiotherapy holds promise for improving radiotherapy efficacy in PDAC. Clin Cancer Res; 23(1); 137-48. ©2016 AACR.

Genetically Engineered Mouse Models of Pancreatic Cancer: The KPC Model (LSL-Kras(G12D/+) ;LSL-Trp53(R172H/+) ;Pdx-1-Cre), Its Variants, and Their Application in Immuno-oncology Drug Discovery.

Pancreatic ductal adenocarcinoma (PDAC) ranks fourth among cancer-related deaths in the United States. For patients with unresectable disease, treatment options are limited and lack curative potential. Preclinical mouse models of PDAC that recapitulate the biology of human pancreatic cancer offer an opportunity for the rational development of novel treatment approaches that may improve patient outcomes. With the recent success of immunotherapy for subsets of patients with solid malignancies, interest is mounting in the possible use of immunotherapy for the treatment of PDAC. Considered in this unit is the value of genetic mouse models for characterizing the immunobiology of PDAC and for investigating novel immunotherapeutics. Several variants of these models are described, all of which may be used in drug development and for providing information on unique aspects of disease biology and therapeutic responsiveness. © 2016 by John Wiley & Sons, Inc.