There’s a mighty force coursing through our veins, capable of defeating even the most formidable opponents such as cancer. In recent years, scientists have discovered the key to unleashing this force. T cell therapies involve rewiring patient immune cells to recognise and target tumours, activating the body’s in-built cancer-killing mechanisms.
One branch of T cell therapy involves introducing transiently expressing tumour-targeting receptors, a safer approach than permanently modifying T cells because it eliminates the risk of introducing genetic mutations which may cause long-term side effects.
However, this type of therapy requires multiple rounds of treatment to achieve optimal results due to the harsh, immunosuppressive tumour microenvironment. Multi-dose T cell infusions are uncomfortable for patients, can trigger unintended side effects and increase the overall cost of treatment.
Andrea Pavesi, a Young Investigator at A*STAR’s Institute of Molecular and Cell Biology (IMCB) teamed up with colleagues from IMCB, as well as A*STAR’s Bioinformatics Institute (BII) and Singapore Immunology Network (SIgN); and collaborators from Duke-NUS Medical School, Singapore and Tisch Cancer Institute at Mount Sinai, the United States; to look for ways to enhance the effectiveness and improve the safety profiles of adoptive cell immunotherapy.
They identified epigenetic inhibitors (substances that modify the chemical tags on DNA to tweak gene expression without altering the underlying genetic code itself) as a means of creating next-generation T cell therapies.
“We focused on epigenetic inhibitors to induce a durable effect on the engineered T cells even after the therapy is removed,” Pavesi explained. “To screen for potential inhibitors, we used 3D cell culture systems that mimic the complex cellular interactions and tumour microenvironment found in the human body.”
The researchers found that inhibiting molecules called G9a and GLP enhances the production of granzyme proteins which enhance cytotoxic cells’ tumour-killing capabilities. Pavesi and colleagues also discovered the sweet spot for engineering: introducing the inhibitor when the T cells are grown and activated in the lab (before they are reintroduced into the patient).
“By adding the epigenetic inhibitor solely during this ex vivo expansion stage, we sought to maximally enhance the T cells’ efficacy against cancer cells, while minimising the potential off-target impacts,” he said, adding that a wash step in the workflow removes excess inhibitor from the T cell preparation, thereby further reducing the risk of toxic side effects.
A look at live (green) and dead (red) tumour cells in culture when exposed to different T cell types. Using 3D cytotoxicity assays, the team analysed the degrees of tumour cell death in cultures with (from top left): no T cells; naïve T cells; T cells with activated tumour targeting receptors (TCR+); and TCR+ T cells treated with UNC0642, a G9a/GLP inhibitor.
©️ A*STAR Research
Tests in both 3D human tumour cell cultures and experimental mice models of liver cancer demonstrated the effectiveness of the G9a/GLP inhibition strategy. The team was excited to find that the approach was successful not only when T cells from healthy donors were used, but also when T cells from patients who had undergone intensive chemotherapy that may be functionally compromised were used.
Spurred by the success of their study, the team is currently investigating the molecular mechanisms underpinning G9a/GLP inhibition with the hopes of translating their work to a clinical setting in the future.
The A*STAR-affiliated researchers contributing to this research are from the Bioinformatics Institute (BII), the Institute of Molecular and Cell Biology (IMCB) and the Singapore Immunology Network (SIgN).
