IDDF2022-ABS-0176 Tumor-derived iron loaded-exosomes impair CD8+ T anti-tumor ability via ferroptosis in hepatocellular carcinoma

Abstract

<h3>Background</h3> Ferroptosis is a form of regulated cell death caused by an iron-dependent accumulation of lipid peroxides. Tumor-infiltrating CD8⁺T cells are associated with progressive loss of effector function due to a suppressive tumor microenvironment (TME). In the TME, tumors cells may cause CD8⁺T cells dysfunction by secreting various bioactive substances, including exosomes. Yet, the role of tumor-derived exosomes (TDEs) in regulating ferroptosis of CD8⁺T cells is still unexplored and remains enigmatic. <h3>Methods</h3> The gene and protein expressions of ferritin heavy chain 1(FTH1) in hepatocellular carcinoma (HCC) tissues were investigated in our clinical cohort as well as in HCC cell lines. Flow cytometry and multiplex immunostaining were used to characterize ferroptosis of CD8⁺T cells. T cells were isolated and cultured with TDEs <i>in vitro</i> for functional experiments. Mouse liver tumor models were applied to assess the role of ferroptosis inhibition in the improvement of anti-tumor immunity <i>in vivo</i>. <h3>Results</h3> Clinically, we demonstrated that FTH1 expression was upregulated in HCC tissues and negatively correlated with the overall survival and clinicopathological scores (IDDF2022-ABS-0176 Figure 1A-C. TfR+CD8+T cells within FTH1 expression tumor tissues indicate poor prognosis of HCC). Specifically, high expression of FTH1 is positively associated with the cluster of ferroptosis CD8⁺T cells abundant within HCC tissues (IDDF2022-ABS-0176 Figure 1D-E. TfR+CD8+T cells within FTH1 expression tumor tissues indicate poor prognosis of HCC). In <i>in vitro</i> experiments, FTH1 was found highly expressed in exosomes of HCC cell lines. TDEs mediated uptake of FTH1 by CD8⁺T cells induced lipid peroxidation and ferroptosis (IDDF2022-ABS-0176 Figure 2A-B. Tumor derived exosomes can be taking up by CD8+T cells), subsequently impaired the cytotoxic functions of CD8⁺T cells and aggravated CD8⁺T cell exhaustion status (IDDF2022-ABS-0176 Figure 2C-D. Tumor derived exosomes can be taking up by CD8+T cells). Mechanistically, NCOA4-mediated ferritin selective autophagy (ferritinophagy) was initiated during ferritin degradation, promoting labile iron accumulation on CD8⁺T cells (IDDF2022-ABS-0176 Figure 3. HCC-derived exosomes mediate ferroptosis and exhaustion in human CD8+T cells). In animal models, using deferoxamine and FTH1 knockdown inhibited ferroptosis on CD8⁺T cells and effectively restored their anti-tumor activity in the mice model (IDDF2022-ABS-0176 Figure 4. Ferritinophagy is involved in HCC derived exosomes induced cell death) ( IDDF2022-ABS-0176 Figure 5. FTHI promotes tumor growth and CD8+T cells ferroptosis in HCC mouse model). <h3>Conclusions</h3> Tumor-derived exosomal FTH1 promoted CD8⁺ T cell ferroptosis in HCC through NCOA4-mediated ferritinophagy, highlighting a promising strategy for cancer immunotherapy.