Deficiency of Stabilin-1 in the Context of Hepatic Melanoma Metastasis.

BACKGROUND: This study analyzed the role of Stabilin-1 on hepatic melanoma metastasis in preclinical mouse models. METHODS: In Stabilin-1-/- mice (Stab1 KO), liver colonization of B16F10 luc2 and Wt31 melanoma was investigated. The numbers, morphology, and vascularization of hepatic metastases and the hepatic microenvironment were analyzed by immunofluorescence. RESULTS: While hepatic metastasis of B16F10 luc2 or Wt31 melanoma was unaltered between Stab1 KO and wildtype (Ctrl) mice, metastases of B16F10 luc2 tended to be smaller in Stab1 KO. The endothelial differentiation of both types of liver metastases was similar in Stab1 KO and Ctrl. No differences in initial tumor cell adhesion and retention to the liver vasculature were detected in the B16F10 luc2 model. Analysis of the immune microenvironment revealed a trend towards higher levels of CD45+Gr-1+ cells in Stab1 KO as compared to Ctrl in the B16F10 luc2 model. Interestingly, significantly higher levels of POSTN were found in the matrix of hepatic metastases of Wt31, while liver metastases of B16F10 luc2 showed a trend towards increased deposition of RELN. CONCLUSIONS: Hepatic melanoma metastases show resistance to Stabilin-1 targeting approaches. This suggests that anti-Stab1 therapies should be considered with respect to the tumor entity or target organs.

Angiogenic and molecular diversity determine hepatic melanoma metastasis and response to anti-angiogenic treatment.

BACKGROUND: Cutaneous melanoma exhibits heterogeneous metastatic patterns and prognosis. In this regard, liver metastasis, which is detected in ~ 10-20% of stage 4 patients, came to the fore of melanoma research, as it recently evolved as decisive indicator of treatment resistance to immune checkpoint inhibition. METHODS: Hepatic metastases were induced by intrasplenic injection of five different murine melanoma cell lines. The efficiencies of hepatic colonization, morphologic patterns, gene expression profiles and degree of vascularization were analyzed and Sorafenib was applied as anti-angiogenic treatment. RESULTS: WT31 melanoma showed the highest efficiency of hepatic colonization, while intermediate efficiencies were observed for B16F10 and RET, and low efficiencies for D4M and HCmel12. RNAseq-based gene expression profiles of high and intermediate metastatic melanomas in comparison to low metastatic melanomas indicated that this efficiency predominantly associates with gene clusters involved in cell migration and angiogenesis. Indeed, heterogeneous vascularization patterns were found in the five models. Although the degree of vascularization of WT31 and B16F10 metastases differed, both showed a strong response to Sorafenib with a successful abrogation of the vascularization. CONCLUSION: Our data indicate that molecular heterogeneity of melanomas can be associated with phenotypic and prognostic features of hepatic metastasis paving the way for organ-specific anti-angiogenic therapeutic approaches.

Exploring the transcriptomic network of multi-ligand scavenger receptor Stabilin-1- and Stabilin-2-deficient liver sinusoidal endothelial cells.

The Class H scavenger receptors Stabilin-1 (Stab1) and Stabilin-2 (Stab2) are two of the most highly expressed genes in liver sinusoidal endothelial cells (LSECs). While Stab1-deficient (Stab1KO) and Stab2-deficient (Stab2KO) mice are phenotypically unremarkable, Stab1/2-double-deficient (StabDKO) mice exhibit perisinusoidal liver fibrosis, glomerulofibrotic nephropathy and a reduced life expectancy. These conditions are caused by insufficiently scavenged circulating noxious blood factors. The effects of either Stab-single- or double-deficiency on LSEC differentiation and function, however, have not yet been thoroughly investigated. Therefore, we performed comprehensive transcriptomic analyses of primary LSECs from Stab1KO, Stab2KO and StabDKO mice. Microarray analysis revealed dysregulation of pathways and genes involved in established LSEC functions while sinusoidal endothelial marker gene expression was grossly unchanged. 82 genes were significantly altered in Stab1KO, 96 genes in Stab2KO and 238 genes in StabDKO compared with controls; 42 genes were found to be commonly dysregulated in all three groups and all of these genes were downregulated. These commonly downregulated genes (CDGs) were categorized as "potential scavengers," "cell adhesion molecules," "TGF-ß/BMP-signaling" or "collagen and extracellular matrix (ECM) components". Among CDGs, Colec10, Lumican and Decorin, were the most strongly down-regulated genes and the corresponding proteins impact on the interaction of LSECs with chemokines, ECM components and carbohydrate structures. Similarly, "chemokine signaling," "cytokine-cytokine receptor interaction" and "ECM-receptor interaction," were the GSEA categories which represented most of the downregulated genes in Stab1KO and Stab2KO LSECs. In summary, our data show that loss of a single Stabilin scavenger receptor - and to a greater extent of both receptors - profoundly alters the transcriptomic repertoire of LSECs. These alterations may affect LSEC-specific functions, especially interactions of LSECs with the ECM and during inflammation as well as clearance of the peripheral blood.