Lymphotoxin-driven cancer cell eradication by tumoricidal CD8⁺ TIL

Area of Science:

• Immunology
• Oncology
• Molecular Biology

Background:

• Tumor-infiltrating lymphocyte (TIL) therapy is an FDA-approved treatment for advanced melanoma.
• The specific TIL subpopulations responsible for tumor eradication are not fully understood.
• Identifying these critical TIL subsets can improve therapeutic strategies.

Purpose of the Study:

• To identify and characterize novel TIL subsets involved in cancer cell lysis.
• To elucidate the molecular mechanisms underlying TIL-mediated tumor eradication.
• To correlate TIL subset enrichment with clinical response to TIL therapy.

Main Methods:

• Utilized patient-derived TIL-melanoma co-cultures.
• Performed whole-genome, loss-of-function CRISPR screening.
• Conducted validation studies using molecular assays.
• Analyzed paired single-cell RNA sequencing (scRNA-seq) and T cell receptor sequencing (scTCR-seq) data.

Main Results:

• Identified a novel CD8+ TIL subset capable of class I HLA-independent cancer cell lysis.
• The lymphotoxin β receptor (LTβR) and interferon (IFN) sensing pathways are critical for TIL-mediated cancer cell killing.
• Expanded CD8+ TIL express high lymphotoxin β (LTB) and upregulate lymphotoxin α (LTA) upon co-culture.
• Enrichment of LTB+ CD8+ T cells correlates with clinical response to TIL therapy.
• LTB+ CD8+ TIL are expanded from LTBlo CD8+ T cells reactive to neoantigens.

Conclusions:

• A novel CD8+ TIL subset, dependent on LTβR and IFN sensing, plays a key role in melanoma tumor eradication.
• This subset is expanded from neoantigen-reactive T cells and its presence is associated with positive clinical outcomes.
• Findings provide insights into TIL therapy mechanisms and potential targets for enhancing anti-tumor immunity.