LFA-1 regulated by IL-2/STAT5 pathway boosts antitumor function of intratumoral CD8⁺ T cells for improving anti-PD-1 antibody therapy

Anti-PD-1 antibody therapy has achieved success in tumor treatment; however, the duration of its clinical benefits are typically short. The functional state of intratumoral CD8⁺ T cells substantially affects the efficacy of anti-PD-1 antibody therapy. Understanding how intratumoral CD8⁺ T cells change will contribute to the improvement in anti-PD-1 antibody therapy. In this study, we found that tumor growth was not arrested after the late administration of anti-PD-1 antibody and that the antitumor function of CD8⁺ T cells decreased with tumor progression. The results of the RNA sequencing of CD8⁺ T cells infiltrating the tumor site on days 7 and 14 showed that the cell adhesion molecule Lymphocyte Function-associated Antigen-1 (LFA-1) participates in regulating the antitumor function of CD8⁺ T cells and that decreased LFA-1 expression in intratumoral CD8⁺ T cells is associated with tumor progression. By analyzing the Gene Expression Omnibus (GEO) database and our results, we found that the antitumor function of intratumoral CD8⁺ T cells with high LFA-1 expression was stronger. The formation of immune synapses is impaired in Itgal-si CD8⁺ T cells, resulting in decreased anti-tumor function. LFA-1 expression in intratumoral CD8⁺ T cells is regulated by the IL-2/STAT5 pathway. The combination of IL-2 and anti-PD-1 antibody effectively enhanced LFA-1 expression and the antitumor function of intratumoral CD8⁺ T cells. The adoptive transfer of OT-1 T cells overexpressing LFA-1, STAT5A, or STAT5B resulted in higher antitumor function, deferred tumor growth, and prolonged survival. These findings indicate that LFA-1-mediated immune synapse acts as a regulator of the antitumor function of intratumoral CD8⁺ T cells, which can be applied to improve anti-PD-1 antibody therapy.