Pericyte dysfunction due to Shb gene deficiency increases B16F10 melanoma lung metastasis

Abstract

Intravasation, vascular dissemination and metastasis of malignant tumor cells require their passage through the vascular wall which is commonly composed of pericytes and endothelial cells. We currently decided to investigate the relative contribution of these cell types to B16F10 melanoma metastasis in mice using an experimental model of host Shb gene (Src homology 2 domain‐containing protein B) inactivation. Conditional inactivation of Shb in endothelial cells using Cdh5‐CreERt2 resulted in decreased tumor growth, reduced vascular leakage, increased hypoxia and no effect on pericyte coverage and lung metastasis. RNAseq of tumor endothelial cells from these mice revealed changes in cellular components such as adherens junctions and focal adhesions by gene ontology analysis that were in line with the observed effects on leakage and junction morphology. Conditional inactivation of Shb in pericytes using Pdgfrb‐CreERt2 resulted in decreased pericyte coverage of small tumor vessels with lumen, increased leakage, aberrant platelet‐derived growth factor receptor B (PDGFRB) signaling and a higher frequency of lung metastasis without concomitant effects on tumor growth or oxygenation. Flow cytometry failed to reveal immune cell alterations that could explain the metastatic phenotype in this genetic model of Shb deficiency. It is concluded that proper pericyte function plays a significant role in suppressing B16F10 lung metastasis.

Mouse Breast Carcinoma Monocytic/Macrophagic Myeloid-Derived Suppressor Cell Infiltration as a Consequence of Endothelial Dysfunction in Shb-Deficient Endothelial Cells Increases Tumor Lung Metastasis

“…FAK is important for the activity of EC adherens junctions [ 33 ] and thus the properties of junctions and their ability to support HC transmigration will have consequences for tumor immunity in a Shb- and FAK-dependent manner. In addition, tumors grown in mice with Shb -deficient EC exhibit increased hypoxia due to a decreased vascular density [ 18 ]. Anti-angiogenic treatment commonly results in tumor hypoxia and recruitment of immunosuppressive leukocytes [ 34 , 35 ].…”

“…The Src homology-2 domain protein B (SHB) is an adapter protein operating downstream of several tyrosine kinase receptor that exerts pleiotropic effects [ 14 ]. The Shb gene is required for VEGFA-induced angiogenesis and vascular leakage [ 15 , 16 , 17 , 18 ], pericyte coverage [ 18 , 19 ] and immune responses [ 19 , 20 , 21 , 22 ]. In tumor biology, Shb exerts multiple effects, depending on tumor type.…”

“…RIP-Tag insulinomas, T241 fibrosarcomas and Lewis lung carcinomas exhibit reduced growth and vascular density when grown in mice lacking Shb [ 15 , 16 ]. B16F10 melanomas show increased metastasis in the absence of Shb [ 18 , 19 ]. Conditional deletion of Shb in EC or pericytes exerted different effects on tumor growth, metastasis and the vasculature [ 18 ].…”

“…B16F10 melanomas show increased metastasis in the absence of Shb [ 18 , 19 ]. Conditional deletion of Shb in EC or pericytes exerted different effects on tumor growth, metastasis and the vasculature [ 18 ]. Decreased pericyte coverage, increased leakage and metastasis were observed in mice with Shb -deficient pericytes [ 18 ] whereas reduced tumor growth and vascular leakage were detected in EC Shb deficient mice [ 18 ], indicating different roles of SHB in these vascular cell types.…”

“…Conditional deletion of Shb in EC or pericytes exerted different effects on tumor growth, metastasis and the vasculature [ 18 ]. Decreased pericyte coverage, increased leakage and metastasis were observed in mice with Shb -deficient pericytes [ 18 ] whereas reduced tumor growth and vascular leakage were detected in EC Shb deficient mice [ 18 ], indicating different roles of SHB in these vascular cell types. Finally, in 4T1 breast carcinomas, Shb deficiency appears to primarily exert its effects via immune cell responses [ 21 ].…”