# King's College London: chemotherapy with HO-1 blockade helps stem-like T cells enter tumours

- Published: 2026-11-06 04:31 UTC
- Section: Life & Health › Medicine
- Tags: stem-like T cells, heme oxygenase-1, HO-1 inhibition, chemotherapy, tumour macrophages, CXCL12 CXCR4, immunotherapy, Cell Stem Cell, Aethox Therapeutics, KCL-HO-1i
- URL: https://realtech.media/news/rt-1be053d6bf39b04df4a9a629_king_s_college/

**Macrophages around tumour blood vessels limit the entry of stem-like T cells. Blocking the enzyme HO-1 reduced this barrier, the authors report in Cell Stem Cell.**

![King's College London: chemotherapy with HO-1 blockade helps stem-like T cells enter tumours](https://sgzwpqqelzmajkcubgkl.supabase.co/storage/v1/object/public/rt-media/2026/11/fcee3f526e0cfc03.jpg)
*NASA Johnson Space Center, Wikimedia Commons, Public domain*

A team led by King's College London reports that chemotherapy helps attract stem-like T cells towards tumours, while macrophages around tumour blood vessels limit their entry. The study was published in Cell Stem Cell, according to miragenews.com [1]. Blocking the enzyme heme oxygenase-1 (HO-1) in these macrophages reduced the barrier. More stem-like T cells then entered the tumour and contributed to an anti-tumour immune response, the authors said [1].

## Macrophages as gatekeepers

Stem-like T cells can renew themselves and develop into other T cells that attack cancer cells. They can help sustain an immune response against a tumour over time and have been shown to matter in responses to immunotherapy [1]. Less is understood about how these cells enter tumours and what hinders them.

The researchers found that a specific population of macrophages, a type of white blood cell, located around the tumour's blood vessels acts as a "gatekeeper". These cells control whether stem-like T cells can move from the bloodstream into the tumour [1]. The macrophages produce HO-1.

## Chemotherapy and HO-1 inhibition

Chemotherapy changes the tumour environment and increases signals that attract stem-like T cells. The cells still struggled to enter the tumour because of the macrophage barrier [1]. HO-1 inhibition alone was not sufficient to control tumour growth. Combined with chemotherapy, the two approaches worked together: chemotherapy attracted the cells, and HO-1 inhibition helped them enter [1].

The T cells were recruited through a signalling pathway involving the chemokine CXCL12 and its receptor CXCR4. CXCL12 acts as the attracting signal, and CXCR4 allows the T cells to respond to it [1].

Senior author Professor James Arnold said that the finding provides a therapeutic target to improve the entry of these cells into tumours. In his view, this may improve responses to other immunotherapies, such as immune checkpoint inhibitors, which rely on these cells [1]. The authors note that the findings could help explain differences in responses to chemotherapy.

Further research is needed to establish whether the mechanism operates in different types of cancer and whether the findings could be translated into treatments for patients [1]. Researchers at King's are developing drugs that target HO-1. The lead candidate is being advanced by Aethox Therapeutics, a King's spinout, which is raising funding to take the drug KCL-HO-1i towards clinical trials [1].

## Sources

1. [miragenews.com](https://www.miragenews.com/gatekeeper-cells-may-hinder-immune-response-to-1772609/)
2. [Medical Xpress](https://medicalxpress.com/news/2026-11-gatekeeper-cells-restrict-immune-response.html)

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Source: RealTech, realtech.media — https://realtech.media/news/rt-1be053d6bf39b04df4a9a629_king_s_college/