Background
Long non-coding RNAs (lncRNAs) can be incorporated into exosomes to mediate the intercellular communication, regulating the occurrence, development, and immunosuppression of cancers. T cell dysfunction has been a hallmark of many cancers, including melanoma, which enables cancer cells escape from host immune surveillance. However, the molecular mechanism of exosome-transmitted lncRNAs in CD8+ T cell dysfunction in melanoma remains largely unclear. Method: The expression of circulating LINC01214 (cirLINC01214) was detected by quantitative real-time polymerase chain reaction (RT-qPCR). Exosomes were isolation from the culture medium and plasma of melanoma patients via ultracentrifugation and characterized by transmission electronic microscopy. The regulation of exosomal LINC01214 on CD8+ T cell function was determined by ELISA. The molecular mechanism of exosomal LINC01214 in CD8+ T cells were assessed by the RNA immunoprecipitation and pull-down assay. A mouse model with reconstituted human immune system was used to explore the role of exosomal LINC01214 in the resistance to anti-PD1 therapy.
Conclusions
Our results demonstrated that exosomal LINC01214 released by melanoma cells promoted immunotherapy resistance by inducing CD8+ T cell dysfunction via the miR-4492/PPP1R11 regulatory loop. Targeting cirLINC01214 might be a potential therapeutic strategy to enhance the outcome of immunotherapy in melanoma.
Results
LINC01214 was highly expressed in melanoma tissues compared with matched adjacent normal tissues. Increased levels of circulating LINC01214 (cirLINC01214) was observed in melanoma patient plasma and correlated with poor PD-1 immunotherapy response. The cirLINC01214 was predominantly released by melanoma cells in an exosome manner. Melanoma cell-derived exosomal LINC01214 inhibits the production of IFN-γ, TNF-α, Granzyme-B and Perforin by CD8+ T cells. Further mechanism study found that cirLINC01214 delivered by exosomes suppressed CD8+ T cell function by up-regulating the expression of Protein Phosphatase 1 Regulatory Inhibitor Subunit 11 (PPP1R11) through sponging miR-4492. CirLINC01214 conferred resistance to PD-1 immunotherapy in melanoma xenograft mouse model. Melanoma patients with poor prognosis after PD-1 treatment carried high levels of exosomal LINC01214. Additionally, the secretion of exosomal cirLINC01214 was enhanced by the Warburg effect, which was consistent with the reprogrammed glucose metabolism of melanoma. Conclusions: Our results demonstrated that exosomal LINC01214 released by melanoma cells promoted immunotherapy resistance by inducing CD8+ T cell dysfunction via the miR-4492/PPP1R11 regulatory loop. Targeting cirLINC01214 might be a potential therapeutic strategy to enhance the outcome of immunotherapy in melanoma.