Identification and regulation of circulating tumor-TCR-matched cytotoxic CD4+ lymphocytes by KLRG1 in bladder cancer
Serena S Kwek1, Hai Yang2, Tony Li1
1Division of Hematology/Oncology, Department of Medicine.
Abstract:
While cytotoxic CD4+ tumor-infiltrating lymphocytes have anticancer activity in patients, whether these can be noninvasively monitored and how these are regulated remains obscure. By matching single cells with T cell receptors (TCRs) in tumor and blood of patients with bladder cancer, we identified distinct pools of tumor-matching cytotoxic CD4+ T cells in the periphery directly reflecting the predominant antigenic specificities of intratumoral CD4+ tumor-infiltrating lymphocytes. On one hand, the granzyme B-expressing (GZMB-expressing) cytotoxic CD4+ subset proliferated in blood in response to PD-1 blockade but was separately regulated by the killer cell lectin-like receptor G1 (KLRG1), which inhibited their killing by interacting with E-cadherin. Conversely, a clonally related, GZMK-expressing circulating CD4+ population demonstrated basal proliferation and a memory phenotype that may result from activation of GZMB+ cells, but was not directly mobilized by PD-1 blockade. As KLRG1 marked the majority of circulating tumor-TCR-matched cytotoxic CD4+ T cells, this work nominates KLRG1 as a means to isolate them from blood and provide a window into intratumoral CD4+ recognition, as well as a putative regulatory receptor to mobilize the cytolytic GZMB+ subset for therapeutic benefit. Our findings also underscore ontogenic relationships of GZMB- and GZMK-expressing populations and the distinct cues that regulate their activity.
Insights
Researchers identified cytotoxic CD4+ T cells in bladder cancer patients’ blood that mirror tumor-specific cells. The killer cell lectin-like receptor G1 (KLRG1) can isolate these cells and potentially enhance cancer immunotherapy.
Area of Science:
- Immunology
- Oncology
- Cell Biology
Background:
- Cytotoxic CD4+ tumor-infiltrating lymphocytes (TILs) possess anticancer activity, but their noninvasive monitoring and regulation are unclear.
- Understanding these cells is crucial for developing effective cancer immunotherapies.
Purpose of the Study:
- To identify and characterize cytotoxic CD4+ T cells in the periphery that match T cell receptors (TCRs) found in bladder tumors.
- To investigate the regulation of these circulating T cells and their potential as biomarkers or therapeutic targets.
Main Methods:
- Single-cell TCR sequencing was used to match T cells from tumor tissue and peripheral blood of bladder cancer patients.
- Flow cytometry and functional assays were employed to analyze T cell subsets, including granzyme B (GZMB) and granzyme K (GZMK) expression, and killer cell lectin-like receptor G1 (KLRG1) expression.
- The response of T cells to PD-1 blockade was assessed.
Main Results:
- Distinct pools of tumor-matching cytotoxic CD4+ T cells were identified in the blood, reflecting intratumoral specificities.
- A GZMB-expressing subset proliferated upon PD-1 blockade, while a GZMK-expressing subset showed a memory phenotype.
- KLRG1 was found to inhibit the killing activity of GZMB+ CD4+ T cells by interacting with E-cadherin and marked the majority of circulating tumor-TCR-matched cytotoxic CD4+ T cells.
Conclusions:
- KLRG1 serves as a marker to isolate circulating tumor-TCR-matched cytotoxic CD4+ T cells from blood, offering insight into intratumoral CD4+ recognition.
- KLRG1 is a potential regulatory receptor for mobilizing the cytolytic GZMB+ subset for therapeutic benefit in cancer.
- The study highlights distinct regulatory cues for GZMB- and GZMK-expressing CD4+ T cell populations and their ontogenic relationships.
