Research on tumour cell-derived small extracellular vesicles (sEVs) that regulate tumour microenvironment (TME) has provided strategies for targeted therapy of head and neck squamous cell carcinoma (HNSCC). Herein, we demonstrated that sEVs derived from HNSCC cancer cells carried CD73 (sEVs CD73 ), which promoted malignant progression and mediated immune evasion. The sEVs CD73 phagocytosed by tumour-associated macrophages (TAMs) in the TME induced immunosuppression. Higher CD73 high TAMs infiltration levels in the HNSCC microenvironment were correlated with poorer prognosis, while sEVs CD73 activated the NF-κB pathway in TAMs, thereby inhibiting immune function by increasing cytokines secretion such as IL-6, IL-10, TNF-α, and TGF-β1. The absence of sEVs CD73 enhanced the sensitivity of anti-PD-1 therapy through reversed immunosuppression. Moreover, circulating sEVs CD73 increased the risk of lymph node metastasis and worse prognosis. Taken together, our study suggests that sEVs CD73 derived from tumour cells contributes to immunosuppression and is a potential predictor of anti-PD-1 responses for immune checkpoint therapy in HNSCC. K E Y WO R D Santi-PD-1 therapy, CD73, head and heck squamous cell carcinoma, macrophage, small extracellular vesicle

Background: Head and neck squamous cell carcinoma (HNSCC) is an aggressive disease worldwide. Much progress has been made in exploring mechanisms and improving the therapy of HNSCC, but only a few studies have focused on the role of ferroptosis on HNSCC progression. The current study aimed to reveal the underlining mechanisms that caveolin-1 (CAV1)-ROS (reactive oxygen species)-ferroptosis axis affect the process of HNSCC and discover novo therapeutic targets or strategies. Methods:The role of CAV1 in ferroptosis was analyzed by FerrDb, and its clinical significance was examined by TCGA dataset of HNSCC. The expressions of caveolin-1 (CAV1) in HNSCC tissues were measured by immunohistochemistry, western blot, and real-time PCR assay. Three siRNA sequences were designed to silence CAV1 mRNA in HNSCC cells. Cell proliferation, colony formation, wound-healing, and transwell assays were used to examine the proliferation, migration, and invasion of cancer cells.ROS evaluation and intracellular Fe 2+ content assays were performed to examine the levels of ferroptosis.Results: Through the analysis with published data, CAV1 was found to overexpress in HNSCC than normal tissues, and was one of the vital suppressors of ferroptosis pathway. Our study showed that CAV1 was over expressed in HNSCC tissues and the high level of CAV1 predicted poorer prognosis. Further experiments indicated that CAV1 could inhibit the ferroptosis of cancer cells and promote the proliferation, migration and invasion.Conclusions: Overexpression of CAV1 in HNSCC inhibited the process of ferroptosis, leading to aggressive phenotypes, as well as worse prognosis. The regulatory pathway of CAV1 and ferroptosis are potential targets for designing diagnostic and combined therapeutic strategies for HNSCC patients.

To elucidate the role of host immune status in the evolution and complexity of hepatitis C virus (HCV) quasispecies, three chronic HCV-infected patients who underwent bone marrow transplantation (BMT) were studied. The three transplanted patients' sera were sampled at pre-BMT, 3 months after BMT, and 12 months after BMT and the nucleotide diversity and substitution of the hypervariable region (HVR) of HCV quasispecies were analyzed. The nucleotide diversity was high at the pre-BMT period (28.2-43.4 x 10(-2) nucleotide difference/site). HVR of HCV quasispecies then became homogeneous in the first 3 months after BMT (0.11-6.40 x 10(-2) nucleotide difference/site). The nucleotide diversity of HVR at 12 months after BMT of all three patients was higher than that of 3 months after BMT but still lower than that of pre-BMT (2.09-6.40 x 10(-2) nucleotide difference/site). The analysis on nucleotide substitution rate showed a higher value between pre-BMT and 3 months after BMT (0.624-0.708 nucleotide difference/site per year) than that between 3 months and 12 months after BMT (0.072-0.127 nucleotide difference/site per year). HCV RNA titer decreased when the host had a low white cell count and increased accordingly. It was concluded that the evolution of HVR of HCV quasispecies related to the immune status of the host during BMT: after immunosuppression, an initial increase of viral populations was followed by the emergence of a dominant strain while the quasispecies gradually recovered as the immunity of the host gained its competence.