Cancer cachexia-related monocytic myeloid-derived suppressor cells impair T-cell negative selection and predict immune-related adverse events.

BACKGROUND AND AIMS: Cancer cachexia is prevalent in various cancers and is associated with chemotherapy toxicity. However, limited data exist on the relationship between cachexia and immune-related adverse events (irAEs). The aim of this study is to explore the correlation between cancer cachexia and irAEs and its possible mechanism. METHODS: A murine model of orthotopic hepatocellular carcinoma (HCC) with cachexia was developed to evaluate the impact of T-cell infiltration into multiple tumor-free organs on the occurrence of irAEs. Single-cell RNA sequencing of thymic stromal cells was performed. Additionally, patients with advanced cancers receiving anti-programmed cell death protein 1/ligand 1 (PD-1/L1) antibody treatment were followed to investigate the relationship between cachexia and irAEs. RESULTS: Inflammatory cell infiltration was observed in multiple tumor-free organs of cachexic HCC mice but not in non-cachexic controls. Immunofluorescence confirmed that the infiltrating cells included CD4(+) and CD8(+) T cells. Morphological assessment and hematoxylin-eosin staining revealed thymic atrophy in cachexic HCC mice. Single-cell RNA sequencing of thymic stromal cells showed a reduction in medullary thymic epithelial cells (mTECs) II and III in cachexic mice. Autoimmune regulator (Aire) downregulation was accompanied by decreased expression of tissue-restricted antigens in mTECs. T cells from cachexic HCC mice induced organ-specific inflammation and T-cell infiltration in multiple organs of tumor-free mice. Following anti-mouse PD-1 antibody treatment, the incidence of inflammation in multiple organs markedly increased in cachexic HCC mice and in tumor-free mice that had received T cells from the cachexic HCC mice. Flow cytometry and immunofluorescence analyses revealed enrichment of thymic monocytic myeloid-derived suppressor cells (M-MDSCs) in cachexic HCC mice. M-MDSCs infiltrated the thymus in cachexic mice with cancer, and they induced apoptosis of mTECs from tumor-free mice in vitro via nitric oxide production. Transfer of M-MDSCs led to inflammatory cell infiltration in multiple organs and thymic involution in tumor-free mice without affecting body weight. Sixty-four patients with advanced cancer receiving anti-PD-1/L1 therapy were enrolled. Patients who developed irAEs had higher levels of circulating M-MDSCs than those who did not. Moreover, patients with cachexia (body mass index (BMI) < 20 kg/m(2) or ≥5% weight loss over the past 6 months) had elevated M-MDSC levels. Patients with both high M-MDSC levels and low BMI or weight loss ≥5% experienced more irAEs (hazard ratio: 2.333; 95% confidence interval: 1.231-4.423). CONCLUSIONS: M-MDSCs in cachexic mice induced mTEC apoptosis through nitric oxide production, impairing T-cell negative selection and promoting autoimmune T-cell infiltration into tumor-free organs. Cancer cachexia-related M-MDSCs may serve as predictive biomarkers for irAEs in patients with advanced cancer.