ZBED6-driven nucleotide metabolic reprogramming improves sensitivity to anti-PD1 therapy in NK/T cell lymphoma

NK/T-cell lymphoma (NKTL) is a highly aggressive non-Hodgkin's lymphoma characterized by extranodal involvement. Programmed cell death protein 1 (PD-1) monoclonal antibody (anti-PD1) treatment is ineffective in some patients, leading to recurrence or metastasis. The resistance to anti-PD1 treatment remains a major challenge in clinics. To identify the core molecules responsible for anti-PD1 treatment resistance and explore the possible molecular mechanisms behind it, simulating the human immune microenvironment during PD-1 treatment is essential. In this study, human peripheral blood mononuclear cells (PBMCs) were transplanted into immunodeficient mice to reconstitute human immunity in mice. The results showed that after immune reconstitution, human immune cells, especially T cells, remain at a high level (≥90%) for at least 4 weeks, indicating that human PBMCs were successfully reconstituted in immunodeficient mice. Two weeks after PBMCs implantation, human NKTL cells (SNK1, KHYG1 and YT) were subcutaneously inoculated into the right lower abdomen of mice. Then, high-dose anti-PD1 treatment was initiated (about 50 mm³, Sintilimab, twice a week, 10 mg/kg each time). The tumor from the mice was removed (≤than 1500 mm³) to prepare a single-cell suspension and re-implanted into the mice. The above process was repeated 5 times (280 days in total). The tumor growth inhibition‌ (TGI) values of NKTL cells before and after induction (71.89% and 1.08% for KHYG1 cells, 54.37% and 3.79% for SNK1 cells, 51.17% and 6.34% for YT cells, respectively) confirmed the successful construction of anti-hPD1-induced resistance NKTL cells (SNK1-Re, KHYG1-Re and YT-Re). Subsequently, we performed transcriptomic, proteomic, and metabolomic analyses on the above resistant and sensitive cell lines. Through multiple functional experiments and clinical sample verification, we confirmed that the transcriptional repressor Zinc finger BED-type containing 6 (ZBED6) was a key biomarker for anti-PD1 treatment resistance in NKTL. Downregulated ZBED6 creates a thymidine-deficient environment by E2F transcription factor 1 (E2F1)-ribonucleoside-diphosphate reductase subunit M2 (RRM2)/dihydropyrimidine dehydrogenase (DPYD), in which drug-resistant tumor cells scavenge thymidine (TdR) from the tumor microenvironment via solute carrier family 29 member 1 (SLC29A1) to increase nucleotide synthesis, thereby establishing an immunosuppressive niche, resulting in the ineffectiveness of anti-PD1 immunotherapy.