# VSIG4 Is Dispensable for Tumor Growth and Metastasis in Murine Colorectal and Breast Cancer Models

## TL;DR

VSIG4, a protein found on human tumor-associated macrophages, does not seem to play a key role in tumor growth or metastasis in mouse models of colorectal and breast cancer.

## Contribution

This study reveals that VSIG4 is not expressed in murine tumor-associated macrophages and does not significantly affect tumor progression or metastasis in mice.

## Key findings

- VSIG4 is expressed on human tumor-associated macrophages but not on murine tumor-associated macrophages.
- VSIG4 deficiency in mice does not alter primary tumor growth or metastasis to the liver and peritoneal cavity.
- Murine models are not suitable for studying the role of VSIG4 in tumor progression.

## Abstract

The role of some immune cell types in promoting tumor growth has become indisputable. A prime example of this is tumor-associated macrophages (TAMs). One protein that has been associated with tumor-promoting TAMs is VSIG4. In this study, we aim to further dissect the role of VSIG4 in tumor progression and metastasis. Analysis of publicly available datasets of human cancers confirmed the expression of VSIG4 mainly on TAMs. However, VSIG4 expression was absent in murine TAMs. Consequently, we observed no differences in primary tumor growth in mice that lack the VSIG4 receptor, compared to their normal counterparts. In tumor-bearing mice, VSIG4 could be detected on macrophages in healthy organs, but its absence did not affect metastasis to those organs. Therefore, murine models are not suitable to study the role of VSIG4 in TAMs and tissue macrophage-expressed VSIG4 does not seem to play an important role in metastasis in mice.

Background: Tumor-associated macrophages (TAMs) are important contributors to tumor progression and metastasis. Therefore, the identification of molecules that mediate these cells’ tumor-promoting functions is highly warranted. VSIG4 has been proposed as a macrophage immune checkpoint. Hence, we aim to investigate this marker in preclinical models. Methods: Publicly available scRNAseq datasets of human colorectal (CRC) and triple-negative breast (TNBC) carcinomas and their murine counterparts were reanalyzed to investigate the expression of VSIG4 in the different TAM populations. Moreover, tumors were grown in Vsig4-deficient mice to evaluate the effect on primary tumor characteristics. Finally, since liver Kupffer cells and large peritoneal macrophages are at least partly VSIG4-high, and are implicated in metastasis to those organs, the dissemination of CRC cancer cells to those sites was assessed in the Vsig4-deficient mice. Results: We demonstrate that VSIG4 expression in human CRC and TNBC is mostly restricted to TAMs, and that its expression correlates with a worse prognosis. However, a striking finding was that no Vsig4 mRNA nor protein could be detected in the microenvironment of primary CRC and TNBC murine tumors, resulting in a similar tumor growth in wild type versus Vsig4-deficient mice. Moreover, no major differences were observed in metastatic tumor load in the liver and peritoneal cavity, apart from a reduced metastasis to the omentum in Vsig4-deficient animals. Conclusions: Murine cancer models are not suitable to investigate the role of VSIG4 in primary tumors and VSIG4 deficiency did not alter liver nor peritoneal cavity metastasis in murine models, with the exception of the omentum.