The anti-tumor efficacy of radiotherapy (RT) is limited by the hypoxic and immunosuppressive tumor microenvironment (TME), which leads to RT resistance and failure in eradicating distant metastatic lesions. Herein, we developed a fluorinated nanosensitizer that could deliver both oxygen (O 2 ) and ADAR1 siRNA into tumor cells to reinforce RT by alleviating hypoxia and immunosuppression. Fluorinated poly(β-amino ester) (fPBAE) was designed to complex ADAR1 siRNA (siADAR1) via electrostatic attraction and load O 2 due to the O 2 -dissolving capacity of fluoroalkyls. The formed nanocomplexes (NCs) facilitated robust cytosolic delivery into cancer cells after intratumoral injection, enabling efficient ADAR1 silencing to promote IFN-β release and enhance DC maturation and T cell infiltration. At the meantime, O 2 was released to alleviate tumoral hypoxia. As thus, NCs significantly enhanced the anti-tumor efficacy of RT and when further coupled with programmed death ligand-1 antibody, they effectively restrained the growth of both treated primary tumors and untreated distant tumors by eliciting robust systemic immune response. This study therefore reports an enlightened strategy for remodeling the immunosuppressive TME and sensitizing radio-immunotherapy. Statement of significance The hypoxic and immunosuppressive tumor microenvironment (TME) greatly limits the anti-tumor efficacy of radiotherapy (RT). To address this critical issue, a nano-sensitizer based on fluorinated poly(β-amino ester) (fPBAE) is herein developed to mediate efficient co-delivery of oxygen (O₂) and ADAR1 siRNA into tumor cells. ADAR1 silencing promotes DC maturation and T cell infiltration to reverse immunosuppression while the released O₂ sensitizes RT. Thus, the nano-sensitizer remarkably enhances the anti-tumor efficacy of RT and elicits robust systemic immune response to eradicate primary and distant tumors when further coupled with PD-L1 antibody.
Adenosine deaminases acting on RNA 1 (ADAR1) has been identified to play key roles in non-small cell lung cancer (NSCLC) progression, and can modulate the sensitivity of cancer cells to anticancer drugs. The current study aimed to investigate the effect of ADAR1 on the sensitivity of NSCLC cells to anlotinib. We established anlotinib-resistant NSCLC (NSCLC/AR) cells, including NCI-H1975/AR and A549/AR cells. Results showed that ADAR1 was significantly upregulated in NSCLC/AR cells. Genetic-knockdown of ADAR1 increased the sensitivity of NSCLC/AR cells to anlotinib by inducing cell proliferation suppression, cell cycle arrest, and apoptosis. Furthermore, knockdown of ADAR1 decreased the level of C-X3-C motif chemokine ligand 1 (CX3CL1) in NCI-H1975/AR and A549/AR cells after anlotinib treatment. Introduction of exogenous CX3CL1 significantly reversed the positive effect of ADAR1 deficiency on NSCLC/AR cell sensitivity, exhibited by the increase of cell viability and decrease of apoptosis. Further in-vivo study demonstrated that knockdown of ADAR1 inhibited NCI-H1975/AR cell tumorigenesis by reducing CX3CL1 expression. Collectively, ADAR1 deficiency increased the sensitivity of NSCLC/AR cells to anlotinib by downregulating CX3CL1, which might provide a potential strategy for NSCLC/AR therapy.
Song J,Liu Y,Yin Y,Wang H,Zhang X,Li Y,Zhao X,Zhang G,Meng X,Jin Y,Lu D
Cancer evades host immune surveillance by virtue of poor immunogenicity. Here, we report an immune suppressor, designated as PTIR1, that acts as a promotor of tumor immune resistance. PTIR1 is selectively induced in human cancers via alternative splicing of DDX58 (RIG-I), and its induction is closely related to poor outcome in patients with cancer. Through blocking the recruitment of leukocytes, PTIR1 facilitates cancer immune escape and tumor-intrinsic resistance to immunotherapeutic treatments. Unlike RIG-I, PTIR1 is capable of binding to the C terminus of UCHL5 and activates its ubiquitinating function, which in turn inhibits immunoproteasome activity and limits neoantigen processing and presentation, consequently blocking T cell recognition and attack against cancer. Moreover, we find that the adenosine deaminase ADAR1 induces A-to-I RNA editing on DDX58 transcript, thus triggering PTIR1 production. Collectively, our data uncover the immunosuppressive role of PTIR1 in tumorigenesis and propose that ADAR1-PTIR1-UCHL5 signaling is a potential cancer immunotherapeutic target.
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