PRF1 and neoplasm: The results showed that CD8+ T cells incubated with A549 cell-derived exosomes secreted significantly lower amounts of TNF-α, IFN-γ, Granzyme-B, and perforin than CD8+ T cells incubated with HBE cell- and NCI-H460 cell-derived exosomes (Fig. 3e and Additional File 2: Supplementary Fig. 4); these results indicated that exosomal circUSP7 inhibits CD8+ T cell secretion of cytokines, including TNF-α, IFN-γ, Granzyme-B and perforin, which inhibit tumour cell growth and ultimately lead to immune escape of NSCLC.