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Tumor Mutation Burden-Associated LINC00638/miR-4732-3p/ULBP1 Axis Promotes Immune Escape via PD-L1 in Hepatocellular Carcinoma.

ABSTRACT: Tumor mutation burden (TMB) is associated with immune infiltration, while its underlying mechanism in hepatocellular carcinoma (HCC) remains unclear. A long noncoding RNA (lncRNA)-related competitive endogenous RNA (ceRNA) network can regulate various tumor behaviors, and research about its correlation with TMB and immune infiltration is warranted. Data were downloaded from TCGA and ArrayExpress databases. Cox analysis and machine learning algorithms were employed to establish a lncRNA-based prognostic model for HCC. We then developed a nomogram model to predict overall survival and odds of death for HCC patients. The association of this prognostic model with TMB and immune infiltration was also analyzed. In addition, a ceRNA network was constructed by using DIANA-LncBasev2 and the starBase database and verified by luciferase reporter and colocalization analysis. Multiplex immunofluorescence was applied to determine the correlation between ULBP1 and PD-L1. An eight-lncRNA (SLC25A30-AS1, HPN-AS1, LINC00607, USP2-AS1, HCG20, LINC00638, MKLN1-AS and LINC00652) prognostic score model was constructed for HCC, which was highly associated with TMB and immune infiltration. Next, we constructed a ceRNA network, LINC00638/miR-4732-3p/ULBP1, that may be responsible for NK cell infiltration in HCC with high TMB. However, patients with high ULBP1 possessed a poorer prognosis. Using multiplex immunofluorescence, we found a significant correlation between ULBP1 and PD-L1 in HCC, and patients with high ULBP1 and PD-L1 had the worst prognosis. In brief, the eight-lncRNA model is a reliable tool to predict the prognosis of HCC patients. The LINC00638/miR-4732-3p/ULBP1 axis may regulate immune escape via PD-L1 in HCC with high TMB.

SUBMITTER: Qi F

PROVIDER: S-EPMC8456090 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:BackgroundTargeted drugs are not quite effective for prolonging the survival of patients with gastric cancer due to off-target effects as well as tumor immune escape mechanisms. Circular RNAs widely exist in tumor regions as biomarkers and can be developed as effective drug targets.MethodsWestern blot, QRT-PCR, fluorescence in situ hybridization, and flow cytometry were used to investigate the function of hsa_circ_0136666 in promoting the proliferation of gastric cancer cells. Tissue immunofluorescence, enzyme-linked immunosorbent assay (ELISA), as well as flow cytometric analysis, was conducted to explore the process of tumor immune evasion in tumor-bearing mice. The differences of circRNA expression in clinical samples were analyzed through tissue microarray FISH. The effect of siRNA on improving the efficacy of anti-PDL1 drugs and suppressing the immune microenvironment was evaluated by the coadministration model.ResultsWe demonstrated that hsa_circ_0136666 was widely and highly expressed in gastric cancer tissues and cells. Functionally, hsa_circ_0136666 promoted gastric cancer tumor proliferation and tumor microenvironment formation, leading to tumorigenesis immune escape, and this effect was dependent on CD8 + T cells. Mechanistically, we confirmed that hsa_circ_0136666 competitively upregulated PRKDC expression by sponging miR-375-3p, regulating immune checkpoint proteins, prompting phosphorylation of PD-L1 to preventing its degradation, driving PD-L1 aggregation and suppressing immune function, thereby impairing cancer immune responses. In terms of application, we found that LNP-siRNA effectively improved anti-PDL1 drug efficacy and inhibited immune escape.ConclusionOur results reveal an oncogenic role played by hsa_circ_0136666 in gastric cancer, driving PD-L1 phosphorylation via the miR-375/PRKDC signaling axis, prompting immune escape. This work proposes a completely new pathogenic mechanism of gastric cancer, uncovers a novel role for hsa_circ_0136666 as an immune target, and provides a rationale for enhancing the efficacy of anti-PD-L1 therapy for gastric cancer.

Project description:BackgroundBreast cancer stem cells have self-renewal capability and are resistant to conventional chemotherapy. PD-L1 could promote the expression of stemness markers (OCT4 and Nanog) in breast cancer stem cells. However, the mechanisms by which PD-L1 regulates the stemness of breast cancer cells and PD-L1 is regulated in breast cancer cells are still unclear.MethodsLentivirus infection was used to construct stable cell lines. The correlation between PD-L1 and stemness markers expression was evaluated in clinical samples. Additionally, luciferase reporter assay combined with RNA-Fluorescence in situ hybridization (RNA-FISH) and RNA-binding protein immunoprecipitation (RIP) assays were used to verify the direct binding of miR-873 on PD-L1. Furthermore, flow cytometry, mammosphere formation combined with nude mouse tumor xenograft model were carried out to examine the effects of miR-873/PD-L1 axis on the stemness of breast cancer cells. Finally, MTT assay was performed to determine the effects of miR-873/PD-L1 axis on drug resistance.FindingsPD-L1 expression was positively correlated with the expression of stemness markers, and overexpression of PD-L1 contributed to chemoresistance and stemness-like properties in breast cancer cells via activating PI3K/Akt and ERK1/2 pathways. Mechanistically, miR-873 inhibited PD-L1 expression through directly binding to its 3'-untranslated region (UTR), and miR-873 attenuated the stemness and chemoresistance of breast cancer cells which was dependent on PD-L1 and the downstream PI3K/Akt and ERK1/2 signaling. Notably, the promotion of PD-L1 on the stemness and chemoresistance was enhanced by recombinant PD-1 (rPD-1), this effect was attenuated by PD-1/PD-L1 inhibitor.InterpretationmiR-873/PD-L1 regulatory axis might serve as a therapeutic target to enhance the chemo-sensitivity and eliminate the stemness of breast cancer cells. FUND: This work was supported by the National Nature Science Foundation of China, No. 81702957, China Postdoctoral Science Foundation, No. 2017M620230, the Postdoctoral Research Funding Scheme of Jiangsu Province (2017), No. 1701197B, and the Priority Academic Program Development (PAPD) of Jiangsu Higher Education Institutions.

Project description:A TLR9 agonist in combination with a PD-1 inhibitor produced powerful antitumor responses in a clinical trial despite TLR9 agonists as monotherapies failing to generate systemic antitumor immune responses due to immunosuppressive effects. However, the mechanism involved in the improved response induced by their combination remains unknown. Methods: Subcutaneous and orthotopic Hepa1-6 tumor model was used for single-drug and combined-drug treatment. We used TLR9 agonist stimulation or lentiviral vectors to overexpress TLR9 and activate TLR9 signaling. We next investigated the crosstalk between PARP1 autoPARylation and ubiquitination and between STAT3 PARylation and phosphorylation mediated by TLR9. Tissue chips were used to analyze the relationships among TLR9, PARP1, p-STAT3 and PD-L1 expression. Results: In this study, we found that the TLR9 agonist in combination with anti-PD-1 therapy or anti-PD-L1 therapy yielded an additive effect that inhibited HCC growth in mice. Mechanistically, we found that TLR9 promoted PD-L1 transcription by enhancing STAT3 Tyr705 phosphorylation. Then, we observed that TLR9 negatively regulated PARP1 expression, which mediated a decrease in STAT3 PARylation and an increase in STAT3 Tyr705 phosphorylation. Moreover, we found that TLR9 enhanced PARP1 autoPARylation by inhibiting PARG expression, which then promoted the RNF146-mediated ubiquitination and subsequent degradation of PARP1. Finally, we observed positive associations between TLR9 and p-STAT3 (Tyr705) or PD-L1 expression and negative associations between TLR9 and PARP1 in HCC patient samples. Conclusions: We showed that hepatoma cell-intrinsic TLR9 activation regulated the crosstalk between PARP1 autoPARylation and ubiquitination and between STAT3 PARylation and phosphorylation, which together upregulated PD-L1 expression and finally induces immune escape. Therefore, combination therapy with a TLR9 agonist and an anti-PD-1 antibody or anti-PD-L1 had much better antitumor efficacy than either monotherapy in HCC.

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Tumor Mutation Burden-Associated LINC00638/miR-4732-3p/ULBP1 Axis Promotes Immune Escape via PD-L1 in Hepatocellular Carcinoma.

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