JAK3 A573V and JAK3 M511I mutations in peripheral T-cell lymphoma mediating resistance to anti-PD-1 therapy through the STAT3/PD-L1 pathway.

Background: Clinical evidence has established anti-PD-1 antibody as a transformative treatment modality for relapsed/refractory peripheral T-cell lymphoma (r/r PTCL), yet reveals a therapeutic plateau with drug resistance observed in 60% of r/r PTCL. The biological determinants underlying this resistance-particularly the complex interplay between tumor-intrinsic characteristics (including tumor mutation burden and oncogenic mutations) and immune microenvironment features (notably PD-L1 expression)-remain insufficiently illustrated. Therefore, we systematically depicted the comprehensive mutation profile of r/r PTCL patients and correlated them with the efficacy and prognosis of anti-PD-1 therapy.

Methods: Here, we enrolled a cohort of 109 patients with r/r PTCL and performed targeted next-generation sequencing of 440 cancer-associated genes. Clinical information was collected and correlated with genetic mutations. We constructed JAK3 mutant models using Jurkat and BA/F3 cell lines. We performed single-cell transcriptomics, western blotting, and flow cytometry to elucidate the molecular mechanism. Additionally, we built a JAK3-mutant syngeneic mouse model to demonstrate in vivo antitumor efficacy of Tofacitinib and anti-PD-1 therapy.

Results: We identified and validated that PD-L1 was a predictor for the efficacy of anti-PD-1 therapy in PTCL patients. The subset of PTCL patients (13.5%) characterized by enrichment of the APOBEC-related mutation signature had worse overall survival (p=0.031) compared with non-APOBEC-enriched samples. JAK3 and EZH2 mutations were associated with lower PD-L1 expression (p<0.05), and JAK3 mutations were independently correlated with shorter progression-free survival (HR=6.07, p=0.0144). Among all types of JAK3 mutations, single-cell transcriptomics, western blotting, and flow cytometry revealed that JAK3 p.A573V and p.M511I mutations led to decreased PD-L1 expression in Jurkat and BA/F3 cell lines through inactivation of STAT3. Compared with JAK3 wild-type syngeneic mouse models, JAK3 p.A573V and p.M511I mutant mice were more sensitive to Tofacitinib but not anti-PD-1 antibody.

Conclusions: In conclusion, we found that JAK3 mutations, especially JAK3 p.A573V and JAK3 p.M511I mutations, lead to poor prognosis of anti-PD-1 therapy through the STAT3/PD-L1 pathway. Tofacitinib is more suitable than anti-PD-1 antibody for JAK3 mutant PTCL patients.

Trial registration number: NCT03502629.