Main Session
Sep
27
PQA 01 - Gastrointestinal Cancer and Central Nervous System
2274 - Longitudinal Single-Cell RNA Sequencing Highlights Distinct Tumor Microenvironment Dynamics between Very Early-Onset and Late-Onset Locally Advanced Rectal Cancer Receiving Immunotherapy-Based Total Neoadjuvant Therapy
Presenter(s)
Luoxi He, BS - Fudan University Shanghai Cancer Center, Shanghai, Shanghai
M. Yan1, Y. Wang1, R. Wu1, L. He1, L. Shen1, J. Wan1, H. Zhang1, Y. Wang1, Y. Chen1, M. Zhou1, Z. Zhang1, J. Wang1, S. Cai2, Y. Xu2, F. Xia1, and Z. Zhang3; 1Department of Radiation Oncology, Fudan University Shanghai Cancer Center, Shanghai, China, 2Department of Colorectal Surgery, Fudan University Shanghai Cancer Center, Shanghai, China, 3Department of Radiation Oncology, Fudan University Shanghai Cancer Center; Department of Oncology, Shanghai Medical College, Fudan University; Shanghai Clinical Research Center for Radiation Oncology; Shanghai Key Laboratory of Radiation Oncology, Shanghai, China
Purpose/Objective(s):
The incidence of colorectal cancer in younger generations has been alarmingly increased worldwide. Accumulating evidences proved that immunotherapy-based total neoadjuvant therapy (iTNT) had further improved complete response in locally advanced rectal cancer (LARC). However, little is known about the exact tumor microenvironment (TME) dynamics during iTNT. Furthermore, the heterogeneity of TME between younger and older LARC patients undergoing iTNT remained elusive. Utilizing single-cell RNA sequencing pre-, on- and post-iTNT treatment, this study aimed to comprehensively decipher the age-associated TME dynamics of LARC patients.Materials/Methods:
A total of 23 LARC patients underwent iTNT were classified as either very early-onset LARC (VEO-LARC, =40 years, n=10) or late-onset LARC (LO-LARC, >40 years, n=13) groups based on their age at diagnosis. The iTNT regimen contained short-course radiotherapy (SCRT) followed by six cycles of immunochemotherapy (capecitabine, oxaliplatin and toripalimab). Single-cell RNA seq analysis was conducted with 45 biopsy tumor tissues collected pre- (n=22), on- (n=11), and post- (n=12) iTNT. Haematoxylin and eosin staining (H&E) slices were available for 20 patients at baseline.Results:
Following quality control, we attained 189186 single cells of high quality and identified 7 major cell types (T/NK, B, myeloid, mast, stromal, epithelial, and glial). At baseline level, VEO-LARC showed a significantly higher proportion of B cells while epithelial cells were more abundant in LO-LARC samples. After analyzing paired samples, we found that the proportions of almost all types of cells except myeloid cells declined after iTNT in VEO-LARC while this trend was not observed in LO-LARC group. Furthermore, we identified 49 subclusters of cells according to classical maker gene expression. Of note, VEO-LARC group exhibited a higher proportion of both CD4+ follicular helper T cell/ peripheral helper T cell (CD4+TfhTph) and germinal center B cell (GCB). Co-occurrence analysis indicated a significantly positive correlation between CD4+TfhTph and GCB (R=0.79, P<0.0001). Considering both cell subclusters were component of tertiary lymphoid structures (TLSs), we reasonably assumed that TLSs were more enriched in VEO-LARC group, which was further validated by quantification of TLSs per mm2 based on H&E staining.Conclusion:
Longitudinal single-cell RNA sequencing dynamically revealed the distinct TME between VEO-LARC and LO-LARC patients receiving iTNT. Our analysis indicated that TLSs were potentially abundant in VEO-LARC group.