S229: CHARACTERISATION OF TUMOR MICROENVIROMENT REMODELLING IN THE PROGRESSION OF AITL WITH SINGLE-CELL RNA SEQUENCING AND IMAGING MASS CYTOMETRY

Abstract

Background: Angioimmunoblastic T-cell lymphoma (AITL) is a common subtype of peripheral T-cell lymphoma (PTCL). AITL is an aggressive malignancy with a poor prognosis, and its clinical manifestations vary greatly among individuals. The current chemotherapy regimens based on anthracycline show limited efficacy, and there is no best rescue treatment for patients with relapsed and refractory (RR) AITL. In addition, the lack of optimal AITL models in vitro greatly limits the basic research on the mechanism of disease occurrence and progression, and also hinders the development of new drugs and preclinical trials. Aims: Our study aims to deeply analyze the tumor heterogeneity and microenviroment remodelling in the progression of AITL at single cell resolution, discovering key molecules of drug resistance and potential theraputic targets. Methods: We detected fresh lymph node samples from initail diagnosed (ID) and relapsed and refractory (RR) AITL patients using single-cell RNA sequencing (scRNA-seq), combined with imaging mass cytometry (IMC) and whole exome sequencing. scRNA-seq was performed to compare the differential transcriptome expression patterns in ID- and RR-AITL samples. IMC was performed to analyze the spatial position relationship and protein expression characteristics of different subgroups in the tumor microenvironment of AITL. Immunofluorescence staining was conducted to detect the expression of relative markers on tissue microarrays in patients with AITL. In addition, AITL patient-derived organoid model was established to study the regulatory role of YY1 and its inhibitors in relapsed and refractory AITL. Results: We found that RR-AITL samples exhibited significant differences in the tumor microenvironment compared with ID patients. ScRNA-seq analysis revealed that transcription factor YY1 was significantly highly expressed in follicular helper T cells (Tfh) of RR-AITL patients, which promoted the proliferation and drug resistance of AITL cells (Fig A-D), consistent with the results of IMC (Fig E,F). The proportion of CD8+ T cells in the RR-AITL sample was reduced, while the proportion of Treg was increased, as well as the depletion of T cells (Fig G). Furthermore, the stemness of B cells in RR-AITL was enhanced and exhibits significant malignant characteristics (Fig H). We also found decreased interaction in RR-AITL samples. B cells and myeloid subgroups may play important roles in the progression of AITL (Fig I,J). As shown in Fig K, EBV+ B cells exhibited a wider and more distribution in RR-AITL (Fig L). Interestingly, EBV+ endothelial cells were presented in both ID- and RR- samples, while the spatial analysis showed that the distance of EBV+ endothelial cells to B cells in RR-AITL was obviously greater than in ID group, and the distance of Tfh to B cells also showed similar result (Fig M,N). Moreover, for the first time, we established AITL patient-derived organoid models that can be stablely cultured in vitro. On this basis, we could further clarify the important roles of transcription factor YY1 in the drug resistance of AITL, evaluate the cytotoxic effect of YY1 inhibitor NP-001 on AITL tumor cells. Image:Summary/Conclusion: In conclusion, our study revealed the differences between initial diagnosed and relapsed /refractory AITL in terms of tumor microenvironment, single-cell transcriptomes, the spatial distributions of different clusters and their interactions features. YY1 may serve as an novel target for drug resistance for RR-AITL patients. These findings may provide a theoretical foundation for improving the clinical treatment of AITL.