# PD-L1 expression in microvascular endothelial cells predicts the efficacy and side effects of anlotinib

## TL;DR

This study explores how PD-L1 expression in blood and lymphatic vessel cells affects cancer treatment with anlotinib and immune response.

## Contribution

The study reveals that PD-L1 in tumor blood vessels predicts anlotinib's effectiveness and side effects by influencing immune cell infiltration.

## Key findings

- PD-L1 expression is higher in tumor blood vessels and is reduced by anlotinib treatment.
- Anlotinib increases CD8+ T cell infiltration in tissues when PD-L1 is downregulated.
- Anlotinib's antitumor effect is strongest when given during the mid-stage of tumor growth.

## Abstract

Immunotherapy plays a crucial role in the treatment of tumors. However, few studies have investigated the relationship between the expression of Programmed Cell Death Ligand 1 (PD-L1, CD274) in microvascular endothelial cells (MECs), including blood endothelial cells (BECs) and lymphatic endothelial cells (LECs), and immune cell infiltration within tissues.

In our study, we utilized data from The Cancer Genome Atlas, a mouse subcutaneous xenograft model, and immunofluorescence and immunohistochemical staining to investigate the relationship between PD-L1 expression in melanoma MECs at different tumor stages and the infiltration of CD8+ T cells in tumor and normal organs, under conditions with and without anlotinib treatment.

We found that PD-L1 expression was upregulated in tumor MECs, while anlotinib downregulated PD-L1 expression in both tumor and normal tissue MECs, corresponding with increased infiltration of CD8+ T cells in the tissues. Additionally, the antitumor effect of anlotinib was most pronounced when administered during the mid-stage of tumor development.

This study evaluated the most effective timing for anlotinib to downregulate PD-L1 expression in tumor and normal tissues to promote immune infiltration. Our findings may offer valuable insights for the clinical use of anlotinib and its potential side effects.