Highly suppressive functional CCR7 ^low Treg subset cells may correlate with poor prognosis of B-ALL

Regulatory T cells (Tregs) may influence prognosis in leukemia. This study aimed to explore the effects and mechanisms of Treg subclusters on the prognosis in B-cell acute lymphoblastic leukemia (B-ALL) using single-cell RNA sequencing (scRNA-Seq).

scRNA-seq was performed on sorted T cells from adults with newly diagnosed (Dix) B-ALL and healthy donors (HD) to establish the training cohort. Treg phenotypes, functions, and prognostic relevance were evaluated. A scRNA-seq dataset from the GEO database, including Dix and relapsed B-ALL, served as the validation cohort. Key findings were confirmed by flow cytometry. Transcription factor and cell-cell interaction analyses were conducted to clarify the mechanisms linking Treg subsets to prognosis.

Tregs were divided into CCR7^high and CCR7^low subclusters. The proportion of CCR7^low Tregs was higher in B-ALL than in HD and in Rel than in Dix. Patients with higher CCR7^low Treg signature scores had a poorer prognosis. Compared with CCR7^high Tregs, CCR7^low Tregs exhibited enhanced activation, proliferation, and immunosuppression. Trajectory analysis suggested differentiation from CCR7^high to CCR7^low Tregs. IKZF2 and JUNB showed consistently increased activity and expression in CCR7^low Tregs across cohorts. CCR7^low Tregs showed increased interactions with terminal effector and exhausted CD8⁺ T cells through the LGALS9-P4HB/HAVCR2/CD44 pathway.

An increased proportion of CCR7^low Tregs correlated with poor prognosis in B-ALL, potentially due to enhanced activation, proliferation, and immunosuppression. IKZF2 and JUNB upregulation may promote CCR7^low Treg differentiation and function. Moreover, CCR7^low Tregs may impair CD8⁺ T cell immunity through the LGALS9-P4HB/HAVCR2/CD44 signaling.