Postdoc UFCSPA Porto Alegre , Rio Grande do Sul, Brazil
Disclosure(s):
Rodrigo Benedetti Gassen, PhD: No financial relationships to disclose
Introduction/Rationale: Immune checkpoint blockade therapies, particularly those targeting the PD-1/PD-L1 and CTLA-4 pathways, have fundamentally transformed cancer treatment, achieving clinical responses in approximately 25% of patients. Although combinatorial strategies have improved these outcomes, a substantial proportion of patients remain refractory to treatment or develop resistance. Emerging evidence implicates tonic PD-1 signaling—a ligand-independent, constitutive pathway distinct from canonical checkpoint inhibition—as a potential contributor to therapeutic resistance. To elucidate the impact of tonic PD-1 signaling on dendritic cell (DC) function and to explore innovative therapeutic approaches aimed at restoring their immunogenic capacity.
Methods: We utilized lentiviral transduction to generate DC2.4 dendritic cell lines stably overexpressing PD-1. Under conditions of tonic PD-1 signaling, we evaluated cell viability and the expression of key costimulatory molecules (MHC II, CD80, CD86). Additionally, we investigated the effects of RIPR-PD-1, a bispecific molecule that disrupts tonic PD-1 signaling via CD45 tethering, and SHP009, a pharmacological inhibitor targeting SHP2 recruitment.
Results: PD-1 overexpression in DCs led to a significant reduction in both cell viability and the expression of costimulatory markers. Treatment with RIPR-PD-1 or SHP009 effectively reversed these inhibitory effects, restoring DC viability and promoting the upregulation of MHC II, CD80, and CD86 expression.
Conclusion: These findings demonstrate that tonic PD-1 signaling compromises dendritic cell functionality by attenuating their viability and costimulatory potential. Pharmacological blockade of tonic PD-1 signaling—either through RIPR-PD-1 or SHP2 inhibition—reinstates a pro-immunogenic DC phenotype. Targeting this non-canonical PD-1 pathway represents a promising strategy to potentiate antitumor immune responses and overcome resistance to existing immunotherapies.
