Collagen matrix deposition by hepatic stellate cells protects hepatocellular carcinoma from NK-mediated cytotoxicity (P2013)

Abstract

Abstract Liver fibrosis (LF), a leading risk factor for hepatocellular carcinoma (HCC), is caused by collagen-producing hepatic stellate cells (HSC) activated during chronic inflammation secondary to hepatitis-C infection, or alcohol liver disease (ALD). NK cells promote disease resolution via RAE1-dependant HSC clearance. A defect in NK function by an ill-defined mechanism contributes to a pro-fibrotic response. Using an engineered bioartifical collagen matrix, the expression of inhibitory leukocyte associated IgG-like receptor-1 (LAIR-1) was increased on dividing NK cells and IL-2-induced NK proliferation was inhibited. Thus, we hypothesized that the accumulation of HSC-derived collagen directly inhibits NK activity and protects both HSC and HCC from innate clearance. We found that deposition of native collagen matrix for 72h protected HSCs from NK lysis in Cr51 cytotoxicity assays. A HCC cell line (HEPG2), which produced no collagen when cultured in the absence of HSCs, was susceptible to activated NK killing and was unaffected by collagenase. To test if HSC-derived collagen protects HEPG2 cells, the populations were differentially labeled with ipophilic dyes and co-cultured for 72h for use in flow-based assays. Collagen matrix protected both targets, while collagenase pretreatment restored NK sensitivity. These results suggest that HSC-derived collagen may contribute to NK dysfunction in LF and HCC, and identifies LAIR-1 as a potential mediator of tumor-induced immune suppression.