# An Examination of Sirolimus's Role in Endothelial Cells of Kaposiform Haemangioendothelioma

## TL;DR

This study develops Kaposiform haemangioendothelioma cell lines and models to better understand the disease and test sirolimus as a potential treatment.

## Contribution

The study introduces CD31+ KHE cell lines and murine models for KHE research and explores sirolimus's mechanism of action.

## Key findings

- CD31+ KHE cells were successfully isolated and showed key marker expression similar to human KHE tumors.
- Subcutaneous tumors in mice mirrored the marker profile of KHE tumors, validating the model.
- Sirolimus treatment downregulated ATG9B in CD31+ KHE cells, suggesting a potential therapeutic mechanism.

## Abstract

Kaposiform haemangioendothelioma (KHE) research faces challenges due to the lack of established cell lines and suitable animal models. Our study aimed to establish KHE cell lines, spheroids and refine murine models to mimic disease characteristics, advancing our understanding of KHE pathogenesis and exploring novel therapies. Primary KHE cells were sorted using CD31 antibodies and cultured into spheroids. These cells were then injected into mice, and the resulting tumours were analysed using immunohistochemistry. Preliminary exploration of the potential mechanisms of sirolimus action on KHE was conducted through transcriptome sequencing. CD31+ KHE cells were isolated and characterised from three out of six patients. The CD31+ KHE cells demonstrated positive expression of essential markers such as CD31, Ki67 and LYVE1, consistent with the profiles observed in KHE tumours. Additionally, subcutaneous tumours displayed similar positive expression of key markers, reminiscent of KHE tumours. Transcriptome sequencing revealed downregulation of ATG9B after sirolimus treatment in CD31+ KHE cells. CD31+ KHE cells can replicate human KHE in murine models, offering a valuable tool for studying pathogenesis. Our findings also suggest a potential mechanism of sirolimus action in treating KHE, warranting further investigation into novel therapeutic strategies.