Main Session
Sep 29
SS 15 - Radiation Biology 2: Novel Immunotherapeutics & Biomarker Discovery

190 - Single-Cell Profiling Reveals Dynamics TIME Remodeling after Neoadjuvant Radiotherapy Followed by Chemotherapy and Immune Checkpoint Blockade in pMMR/MSS LARC

08:20am - 08:30am PT
Room 22/23

Presenter(s)

Yinan Chen, PhD Headshot
Yinan Chen, PhD - Cancer Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, Beijing

Y. Chen1, J. Shi2, T. Xu1, H. Li3, J. Shuai1, H. Ma3, N. Wang3, R. Wang4, X. Shi4, M. Liu4, Y. Tang5, D. Li6,7, and J. Jin8; 1State Key Laboratory of Molecular Oncology and Department of Radiation Oncology, National Cancer Center/National Clinical Research Center for Cancer/Cancer Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College (PUMC), Beijing, China, 2Department of Radiation Oncology, Tianjin Medical University Cancer Institute & Hospital, Key Laboratory of Cancer Prevention and Therapy, National Clinical Research Center for Cancer, Tianjin’s Clinical Research Center for Cancer, Tianjin, 300060, China, Tianjin, China, 3State Key Laboratory of Molecular Oncology and Department of Radiation Oncology, National Cancer Center/National Clinical Research Center for Cancer/Cancer Hospital, Chinese Academy of Medical Sciences (CAMS) and Peking Union Medical College (PUMC), Beijing, China, 4State Key Laboratory of Molecular Oncology, National Cancer Center/National Clinical Research Center for Cancer/Cancer Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100021, Beijing, China, 5State Key Laboratory of Molecular Oncology and Department of Radiation Oncology, National Cancer Center/ National Clinical Research Center for Cancer/ Cancer Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China, 6Laboratory Animal Center, National Cancer Center/National Clinical Research Center for Cancer/Cancer Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100021, Beijing, China, 7State Key Laboratory of Molecular Oncology, National Cancer Center/National Clinical Research Center for Cancer/Cancer Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100021, Beijing, China, 8State Key Laboratory of Molecular Oncology and Department of Radiation Oncology, National Cancer Center/National Clinical Research Center for Cancer/Cancer Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China

Purpose/Objective(s):

For pMMR/MSS locally advanced rectal cancer (LARC), neoadjuvant chemoradiotherapy (nCRT) plus immune checkpoint blockade (ICB) significantly improves tumor regression, yet the underlying mechanisms are incompletely elucidated. Thus, we applied single-cell RNA sequencing (scRNA-seq) to investigate the tumor immune microenvironment (TIME) remodeling during nCRT treatment with or without ICB (i-nCRT) in LARC patients.

Materials/Methods:

Longitudinal tissue samples for scRNA-seq were collected from pMMR/MSS locally advanced rectal cancer patients (9 nCRT, 19 i-nCRT) at three treatment phases: baseline (pre-treatment), after radiotherapy (25Gy/5f), and after chemotherapy or chemotherapy combined ICB (by biopsy or surgery). Patients were classified as complete responders (CRs) or non-complete responders (NCRs) based on tumor residence.. High-resolution clustering was performed to find subcelltypes, then compositional analysis was applied to identify temporal- and response-related key subtypes, of which functional analysis was performed using differentially expressed gene identification, pathway enrichment, pseudotime trajectory analysis, and motif enrichment.

Results:

A total of 52 tumor tissue samples (17 pre, 19 on and 16 post) from 28 pMMR LARC patients (9 nCRT,18 i-nCRT) were subjected to scRNA-seq and 464,621 cells were obtained after stringent filtering. TIME dynamic analysis revealed that B cells (P = 0.045) and plasma cells (P = 0.042) decreased after radiotherapy (RT), while myeloid cells (P = 0.016) and neutrophils (P = 0.035) increased. T cells and ILCs showed an increase after chemotherapy(±ICB) (P = 0.061, P = 0.034), while neutrophils decreased (P = 0.029). We further identified 7 neutrophil subsets, 20 T/I/NK subsets, and 11 myeloid subsets. Therapeutic response analysis identified, specifically, ISG15high neutrophils (P = 0.024) and SPP1high macrophages enriched in i-nCRT CRs while CXCR4high neutrophils (P = 0.058) showed a trend in i-nCRT iCRs, RHOHhigh neutrophils (P < 0.001) and CD8+ Tem enriched in nCRT CRs while NDEL1high neutrophils (P = 0.048) and Th17 increased in nCRT iCRs. Given neutrophils’ divergent roles in clinical responses, we conducted focused analysis. Further analysis indicated that ISG15high neutrophils exert effects through interferon signaling, while CXCR4high neutrophils were associated with interleukin-1 and TNF signals

Conclusion:

Our single-cell atlas delineates the dynamic reorganization of TIME during multimodal therapy in pMMR/MSS LARC. The identification of ISG15high neutrophils as i-nCRT-specific responders highlights neutrophil heterogeneity as a critical determinant of therapeutic outcome, which provide mechanistic insights for developing predictive biomarkers of i-nCRT in pMMR/MSS LARC.