10P - Cancer cells induce intracellular gap formation in sinusoidal endothelial cells to produce liver metastasis through pro-inflammatory paracrine mechanisms

Background

Engraftment of cancer cells to liver pre-metastatic niches requires complex interaction with liver sinusoidal endothelial cells (LSECs). Intracellular gap (iGap) formation in LSECs is caused by the destruction of fenestrae and appears under pathological conditions. Here, we aimed to explore the novel role of LSECs-iGap in liver metastasis of cancer cells.

Methods

Mouse models using acetaminophen (APAP) or thioacetamide (TAA) followed by intrasplenic injection of hepatocellular carcinoma (HCC) cell line, Hepa1-6 cells, to assess the LSECs-iGap formation. Functional effects of LSECs-iGap on cancer cells were analyzed using MMPs inducer, monocrotaline and inhibitor, doxycycline and MMP2/9 inhibitor. Morphological and molecular features of LSECs-iGap were examined using in vivo mouse models and in vitro co-culture system with electron microscopy, 3 dimensions tomographic reconstruction image (3D-TRI), RNA-sequencing, cytokine array and endothelial trans-endothelial migration assay. Biopsy specimens from 98 patients with HCC were statistically evaluated.

Results

APAP-induced liver injury and TAA-induced fibrotic liver resulted in LSECs-iGap formation, which positively correlated with increased numbers of metastatic foci after Hepa1-6 cells injection. In addition, Hepa1-6 cells induced IL-23-dependent TNF-α secretion by LSECs and triggered LSECs-iGap formation, toward which their processes protruded to transmigrate into the liver parenchyma. TNF-α caused depolymerization of F-actin and increased MMP9, ICAM1, and CXCLs expression in LSECs. Moreover, high expression of ICAM1 and MMP9 was significantly associated with intrahepatic metastasis and overall survival of patients with HCC. Blocking MMP9 activity by doxycycline or MMP-2/9 inhibitor eliminated LSECs-iGap formation and attenuated liver metastasis of Hepa1-6 cells.

Conclusions

This study revealed that cancer cells induced LSEC-iGap formation via pro-inflammatory paracrine mechanisms and proposed MMP9 as a novel target for blocking cancer cell metastasis to the liver.

Clinical trial identification

Editorial acknowledgement

Legal entity responsible for the study

H.H. Truong.

Funding

Japan Agency for Medical Research and Development.

Disclosure

All authors have declared no conflicts of interest.