ESRP1-mediated biogenesis of circPTPN12 inhibits hepatocellular carcinoma progression by PDLIM2/ NF-κB pathway.

BACKGROUND: Emerging evidence indicates the pivotal involvement of circular RNAs (circRNAs) in cancer initiation and progression. Understanding the functions and underlying mechanisms of circRNAs in tumor development holds promise for uncovering novel diagnostic indicators and therapeutic targets. In this study, our focus was to elucidate the function and regulatory mechanism of hsa-circ-0003764 in hepatocellular carcinoma (HCC). METHODS: A newly discovered hsa-circ-0003764 (circPTPN12) was identified from the circbase database. QRT-PCR analysis was utilized to assess the expression levels of hsa-circ-0003764 in both HCC tissues and cells. We conducted in vitro and in vivo experiments to examine the impact of circPTPN12 on the proliferation and apoptosis of HCC cells. Additionally, RNA-sequencing, RNA immunoprecipitation, biotin-coupled probe pull-down assays, and FISH were employed to confirm and establish the relationship between hsa-circ-0003764, PDLIM2, OTUD6B, P65, and ESRP1. RESULTS: In HCC, the downregulation of circPTPN12 was associated with an unfavorable prognosis. CircPTPN12 exhibited suppressive effects on the proliferation of HCC cells both in vitro and in vivo. Mechanistically, RNA sequencing assays unveiled the NF-κB signaling pathway as a targeted pathway of circPTPN12. Functionally, circPTPN12 was found to interact with the PDZ domain of PDLIM2, facilitating the ubiquitination of P65. Furthermore, circPTPN12 bolstered the assembly of the PDLIM2/OTUD6B complex by promoting the deubiquitination of PDLIM2. ESRP1 was identified to bind to pre-PTPN12, thereby fostering the generation of circPTPN12. CONCLUSIONS: Collectively, our findings indicate the involvement of circPTPN12 in modulating PDLIM2 function, influencing HCC progression. The identified ESRP1/circPTPN12/PDLIM2/NF-κB axis shows promise as a novel therapeutic target in the context of HCC.

MAL2 reprograms lipid metabolism in intrahepatic cholangiocarcinoma via EGFR/SREBP-1 pathway based on single-cell RNA sequencing.

Intrahepatic cholangiocarcinoma (ICC) is a highly aggressive cancer characterized by a poor prognosis and resistance to chemotherapy. In this study, utilizing scRNA-seq, we discovered that the tetra-transmembrane protein mal, T cell differentiation protein 2 (MAL2), exhibited specific enrichment in ICC cancer cells and was strongly associated with a poor prognosis. The inhibition of MAL2 effectively suppressed cell proliferation, invasion, and migration. Transcriptomics and metabolomics analyses suggested that MAL2 promoted lipid accumulation in ICC by stabilizing EGFR membrane localization and activated the PI3K/AKT/SREBP-1 axis. Molecular docking and Co-IP proved that MAL2 interacted directly with EGFR. Based on constructed ICC organoids, the downregulation of MAL2 enhanced apoptosis and sensitized ICC cells to cisplatin. Lastly, we conducted a virtual screen to identify sarizotan, a small molecule inhibitor of MAL2, and successfully validated its ability to inhibit MAL2 function. Our findings highlight the tumorigenic role of MAL2 and its involvement in cisplatin sensitivity, suggesting the potential for novel combination therapeutic strategies in ICC.

Phosphorylated FOXQ1, a novel substrate of JNK1, inhibits sorafenib-induced ferroptosis by activating ETHE1 in hepatocellular carcinoma.

Hepatocellular carcinoma (HCC) is a highly heterogeneous and malignant cancer with poor overall survival. The application of sorafenib is a major breakthrough in the treatment of HCC. In our study, FOXQ1 was significantly overexpressed in sorafenib-resistant HCC cells and suppressed sorafenib-induced ferroptosis. We found that phosphorylation of FOXQ1 at serine 248 is critical for the suppression of sorafenib-induced ferroptosis. Furthermore, as the upstream phosphorylation kinase of FOXQ1, JNK1, which is activated by sorafenib, can directly phosphorylate the serine 248 site of FOXQ1. Then, the phosphorylated FOXQ1 got a high affinity for the promoter of ETHE1 and activates its transcription. Further flow cytometry results showed that ETHE1 reduced intracellular lipid peroxidation and iron levels. Collectively, our study implicated the JNK1-FOXQ1-ETHE1 axis in HCC ferroptosis induced by sorafenib, providing mechanistic insight into sensitivity to sorafenib therapy of HCC.

CRISPR/Cas9 screen reveals that targeting TRIM34 enhances ferroptosis sensitivity and augments immunotherapy efficacy in hepatocellular carcinoma.

Hepatocellular carcinoma (HCC) is a prevalent malignancy characterized by complex heterogeneity and drug resistance. Resistance to ferroptosis is closely related to the progression of HCC. While HCC tumors vary in their sensitivity to ferroptosis, the precise factors underlying this heterogeneity remain unclear. In this study, we sought to elucidate the mechanisms that contribute to ferroptosis resistance in HCC. Whole-genome CRISPR/Cas9 screen using a subtoxic concentration (IC20) of ferroptosis inducer erastin in the HCC cell line Huh7 revealed TRIM34 as a critical driver of ferroptosis resistance in HCC. Further investigation revealed that TRIM34 suppresses ferroptosis in HCC cells, promoting their proliferation, migration, and invasion both in vitro and in vivo. Furthermore, TRIM34 expression is elevated in HCC tumor tissues, correlating with a poor prognosis. Mechanistically, TRIM34 directly interacts with Up-frameshift 1 (UPF1), a core component of the nonsense-mediated mRNA decay (NMD) pathway, to promote its ubiquitination and degradation. This interaction suppresses GPX4 transcript degradation, thus promoting the protein levels of this critical ferroptosis suppressor in HCC. In light of the close crosstalk between ferroptosis and the adaptive immune response in cancer, HCC cells with targeting knockdown of TRIM34 exhibited an improved response to anti-PD-1 treatment. Taken together, the TRIM34/UPF1/GPX4 axis mediates ferroptosis resistance in HCC, thereby promoting malignant phenotypes. Targeting TRIM34 may thus represent a promising new strategy for HCC treatment.

RAC1high NK cell-based immunotherapy in hepatocellular carcinoma via STAT3-NKG2D axis.

Natural killer (NK) cells exert an indispensable role in innate immune responses against cancer progression, however NK cell dysfunction has been rarely reported in hepatocellular carcinoma (HCC). This study sought to uncover the immunoregulatory mechanisms of tumor-infiltrating NK cells in HCC. A consensus NK cell-based signature (NKS) was constructed using integrative machine learning algorithms based on multi-omics data of HCC patients. HCC tumors had lower numbers of infiltrating NK cells than para-tumor normal liver tissues. Based on the NK cell-associated genes, the NKS was built for HCC prognostic prediction and clinical utilities. Drug targets and novel compounds were then identified for high-NKS groups. RAC1 was confirmed as the hub gene in the NKS genes. RAC1 was upregulated in HCC tumors and positively correlated with shorter survival time. RAC1 overexpression in NK-92 cells facilitated the cancer-killing capacity by the anticancer cytotoxic effectors and the upregulated NKG2D. The survival time of PDX-bearing mice was also prolonged upon NK-92RAC1 cells. Mechanistically, RAC1 interacted with STAT3 and facilitated its activation, thereby enabling its binding to the promoter region of NKG2D and functioning as a transcriptional regulator in NK-92 via molecular docking, Co-IP assay, CHIP and luciferase experiments. Collectively, our study describes a novel function of RAC1 in potentiating NK cell-mediated cytotoxicity against HCC, highlighting the clinical utilities of NKS score and RAC1high NK cell subset in HCC immunotherapy.

Cuproptosis-associated genes (CAGs) contribute to the prognosis prediction and potential therapeutic targets in hepatocellular carcinoma.

BACKGROUND: Cuproptosis is a novel form of cell death that exhibits close association with mitochondrial respiration and occurs through distinct mechanisms compared to previously characterized forms of cell death. However, the precise impact of cuproptosis-associated genes (CAGs) on prognosis, immune profiles, and treatment efficacy in hepatocellular carcinomas (HCC) remains poorly understood. METHODS: A comprehensive analysis of CAGs in hepatocellular carcinoma (HCC) prognosis was conducted using genomic data from HCC patients. Consensus clustering analysis was performed to determine molecular subtypes related to cuproptosis in HCC. The single-sample gene set enrichment analysis (ssGSEA) algorithm was applied to quantify the infiltration levels of immune cells, while the "ESTIMATE" package was employed to calculate tumor purity, stromal scores, and immune scores in the tumor microenvironment (TME). Principal component analysis (PCA) algorithm was utilized to construct a risk score related to CAGs. Finally, CCK8, wound healing, Transwell migration/invasion, EDU and xenograft model were employed to explore the potential oncogenic role of MTF1. RESULTS: Three distinct patterns of cuproptosis modification were identified, each associated with unique functional enrichments, clinical characteristics, immune cell infiltration, immune checkpoints, tumor microenvironment (TME), and prognosis. A CAGs-related risk score (Cuscore) was developed to predict prognosis in TCGA and validated in GSE76427 and ICGC datasets. Notably, patients with a low Cuscore had better prognoses and were more likely to benefit from immunotherapy.Additionally, the high Cuscore group in HCC also revealed three potential therapeutic targets (TUBA1B, CDC25B, and CSNK2A1) as well as several therapeutic compounds. Moreover, the experiment measured the expression levels of six prognosis-related CAGs, wherein knockdown of MTF1 exhibited suppression of proliferation, invasion, and migration formation in HCC cell lines. CONCLUSION: The findings have enhanced our comprehension of the cuproptosis characteristics in HCC, and stratification based on CuScore may potentially enhance the prediction of patients' prognosis and facilitate the development of effective and innovative treatment strategies.

HuR-positive stress granules: Potential targets for age-related osteoporosis.

Aging impairs osteoblast function and bone turnover, resulting in age-related bone degeneration. Stress granules (SGs) are membrane-less organelles that assemble in response to stress via the recruitment of RNA-binding proteins (RBPs), and have emerged as a novel mechanism in age-related diseases. Here, we identified HuR as a bone-related RBP that aggregated into SGs and facilitated osteogenesis during aging. HuR-positive SG formation increased during osteoblast differentiation, and HuR overexpression mitigated the reduction in SG formation observed in senescent osteoblasts. Moreover, HuR positively regulated the mRNA stability and expression of its target ß-catenin by binding and recruiting ß-catenin into SGs. As a potential therapeutic target, HuR activator apigenin (API) enhanced its expression and thus aided osteoblasts differentiation. API treatment increased HuR nuclear export, enhanced the recruitment of ß-catenin into HuR-positive SGs, facilitated ß-catenin nuclear translocation, and contributed osteogenesis. Our findings highlight the roles of HuR and its SGs in promoting osteogenesis during skeletal aging and lay the groundwork for novel therapeutic strategies against age-related skeletal disorders.

Endothelial DGKG promotes tumor angiogenesis and immune evasion in hepatocellular carcinoma.

BACKGROUND & AIMS: Hepatocellular carcinoma (HCC) is among the most prevalent and lethal cancers worldwide. The tumor microenvironment (TME) contributes to the poor response of patients with HCC to current therapies, while tumor vascular endothelial cells (ECs) are fundamental TME components that significantly contribute to tumor progression. However, the specific functions and mechanisms of tumor vascular ECs in HCC remain unclear. METHODS: We screened and validated diacylglycerol kinase gamma (DGKG) hyper-expression specifically in HCC tumor vascular ECs. Single-cell RNA-sequencing, cytometry by time-of-flight, and in vitro and in vivo studies were performed to investigate the functions of endothelial DGKG. Multiplexed immunohistochemistry staining and flow cytometry were used to evaluate changes in the TME. RESULTS: Functionally, endothelial DGKG promotes tumor angiogenesis and immunosuppressive regulatory T-cell differentiation in HCC. Of significance, we found that HIF-1α activates DGKG transcription by directly binding to its promoter region under hypoxia. Upregulated DGKG promotes HCC progression by recruiting ubiquitin specific peptidase 16 to facilitate ZEB2 deubiquitination, which increases TGF-ß1 secretion, thus inducing tumor angiogenesis and regulatory T-cell differentiation. Importantly, targeting endothelial DGKG potentiated the efficiency of dual blockade of PD-1 and VEGFR-2. CONCLUSION: Hypoxia-induced EC-specific DGKG hyper-expression promotes tumor angiogenesis and immune evasion via the ZEB2/TGF-ß1 axis, suggesting EC-specific DGKG as a potential therapeutic target for HCC. IMPACT AND IMPLICATIONS: Here, we reported that hypoxia-induced endothelial cell-specific DGKG hyper-expression promotes angiogenesis and immune evasion in HCC by recruiting USP16 for K48-linked deubiquitination and inducing the subsequent stabilization of ZEB2, leading to increased TGF-ß1 secretion. Most importantly, endothelial DGKG inhibition greatly improved the efficacy of the dual combination of anti-VEGFR2 and anti-PD-1 treatment in a mouse HCC model, significantly inhibiting the malignant progression of HCC and improving survival. This preclinical study supports the targeting of endothelial DGKG as a potential strategy for precision HCC treatment.

Single-cell RNA-sequencing atlas reveals an FABP1-dependent immunosuppressive environment in hepatocellular carcinoma.

BACKGROUND: Single-cell RNA sequencing, also known as scRNA-seq, is a method profiling cell populations on an individual cell basis. It is particularly useful for more deeply understanding cell behavior in a complicated tumor microenvironment. Although several previous studies have examined scRNA-seq for hepatocellular carcinoma (HCC) tissues, no one has tested and analyzed HCC with different stages. METHODS: In this investigation, immune cells isolated from surrounding normal tissues and cancer tissues from 3 II-stage and 4 III-stage HCC cases were subjected to deep scRNA-seq. The analysis included 15 samples. We distinguished developmentally relevant trajectories, unique immune cell subtypes, and enriched pathways regarding differential genes. Western blot and co-immunoprecipitation were performed to demonstrate the interaction between fatty acid binding protein 1 (FABP1) and peroxisome proliferator-activated receptor gamma(PPARG). In vivo experiments were performed in a C57BL/6 mouse model of HCC established via subcutaneous injection. RESULTS: FABP1 was discovered to be overexpressed in tumor-associated macrophages (TAMs) with III-stage HCC tissues compared with II-stage HCC tissues. This finding was fully supported by immunofluorescence detection in significant amounts of HCC human samples. FABP1 deficiency in TAMs inhibited HCC progression in vitro. Mechanistically, FABP1 interacted with PPARG/CD36 in TAMs to increase fatty acid oxidation in HCC. When compared with C57BL/6 mice of the wild type, tumors in FABP1-/- mice consistently showed attenuation. The FABP1-/- group's relative proportion of regulatory T cells and natural killer cells showed a downward trend, while dendritic cells, M1 macrophages, and B cells showed an upward trend, according to the results of mass cytometry. In further clinical translation, we found that orlistat significantly inhibited FABP1 activity, while the combination of anti-programmed cell death 1(PD-1) could synergistically treat HCC progression. Liposomes loaded with orlistat and connected with IR780 probe could further enhance the therapeutic effect of orlistat and visualize drug metabolism in vivo. CONCLUSIONS: ScRNA-seq atlas revealed an FABP1-dependent immunosuppressive environment in HCC. Orlistat significantly inhibited FABP1 activity, while the combination of anti-PD-1 could synergistically treat HCC progression. This study identified new treatment targets and strategies for HCC progression, contributing to patients with advanced HCC from new perspectives.

M2 macrophage-secreted exosomes promote metastasis and increase vascular permeability in hepatocellular carcinoma.

BACKGROUND: Metastasis is a key feature of malignant tumors and significantly contributes to their high mortality, particularly in hepatocellular carcinoma (HCC). Therefore, it is imperative to explore the mechanism of tumor metastasis. Recently, tumor-associated macrophages (TAMs) have been demonstrated to promote tumor progression, while TAM-derived molecules involved in HCC metastasis warrant further investigation. METHODS: THP-1 was treated with IL-4 (Interleukin-4) and IL-13 (Interleukin-13) for M2 polarized macrophages. Exosomes derived from M2 macrophages were characterized. Then, HCC cells or human umbilical vein endothelial cells (HUVECs) were co-cultured with M2 macrophages or treated with M2 macrophage-secreted exosomes. Next, Transwell®, Scratch assay, tube formation, and endothelial permeability assays were performed. Moreover, RT-PCR, western blotting, immunofluorescence, and ELISA were used to assess mRNA and protein expression levels. Finally, the miRNA expression profiles of exosomes derived from M2 and M0 macrophages were analyzed. RESULTS: M2 macrophage infiltration was correlated with metastasis and a poor prognosis in HCC patients. M2-derived exosomes were absorbed by HCC and HUVEC cells and promoted the epithelial-mesenchymal transition (EMT), vascular permeability, and angiogenesis. Notably, MiR-23a-3p levels were significantly higher in M2-derived exosomes and hnRNPA1 mediated miR-23a-3p packaging into exosomes. Phosphatase and tensin homolog (PTEN) and tight junction protein 1 (TJP1) were the targets of miR-23a-3p, as confirmed by luciferase reporter assays. Lastly, HCC cells co-cultured with M2-derived exosomes secreted more GM-CSF, VEGF, G-CSF, MCP-1, and IL-4, which in turn further recruited M2 macrophages. CONCLUSIONS: Our findings suggest that M2 macrophage-derived miR-23a-3p enhances HCC metastasis by promoting EMT and angiogenesis, as well as increasing vascular permeability. Video Abstract.

Translating imaging traits of mass-forming intrahepatic cholangiocarcinoma into the clinic: From prognostic to therapeutic insights.

Background & Aims: The progress toward clinical translation of imaging biomarkers for mass-forming intrahepatic cholangiocarcinoma (MICC) is slower than anticipated. Questions remain on the biologic behaviour underlying imaging traits. We developed and validated imaging-based prognostic systems for resected MICCs with an appraisal of the tumour immune microenvironment (TIME) underpinning patient-specific imaging traits. Methods: Between January 2009 and December 2019, a total of 322 patients who underwent dynamic computed tomography/magnetic resonance imaging and curative-intent resection for MICC at three hepatobiliary institutions were retrospectively recruited, divided into training (n = 193) and validation (n = 129) datasets. Two radiological and clinical scoring (RACS) systems, one integrating preoperative variables and one integrating preoperative and postoperative variables, were developed using Cox regression analysis. We then prospectively analysed the TIME of tissue samples from 20 patients who met study criteria from January 2021 to December 2021 using multiplexed immunofluorescence. Results: Preoperative and postoperative MICC-RACS systems built on carbohydrate antigen 19-9, albumin, tumour number, radiological/pathological nodal status, pathological necrosis, and three radiological traits (arterial enhancement pattern, tumour boundary, and capsular retraction) demonstrated good performance in predicting disease-specific (C-statistic >0.80) and disease-free (C-statistic >0.75) survival that outperformed rival models and staging systems across study cohorts (P <0.05 for all). Patients with MICC-RACS score of 0-2 (low risk), 3-5 (medium risk), and ≥6 (high risk) had incrementally worse prognosis after surgery. Significant differences in spatial distribution and infiltration level of immune cells were identified between arterial enhancement patterns. Enhanced infiltration of immunosuppressive regulatory T cells and M2-like macrophages at the invasive margin were noted in tumours with distinct boundary and capsular retraction, respectively. Conclusions: Our MICC-RACS systems are simple but powerful prognostic tools that may facilitate the understanding of spatially distinct TIMEs and patient-tailored immunotherapy approach. Impact and Implications: The progress toward clinical translation of imaging biomarkers for mass-forming intrahepatic cholangiocarcinoma (MICC) is slower than anticipated. Questions remain on the biologic behaviour of MICC underlying imaging traits. In this study, we proposed novel and easy-to-use tools, built on radiological and clinical features, that demonstrated good performance in predicting the prognosis either before or after surgery and outperformed rival models/systems across major imaging modalities. The characteristic radiological traits integrated into prognostic systems (arterial enhancement pattern, tumour boundary, and capsular retraction) were highly correlated with heterogeneous tumour-immune microenvironments, thereby renovating treatment paradigms for this difficult-to-treat disease.

Derivation and validation of machine learning models for preoperative estimation of microvascular invasion risk in hepatocellular carcinoma.

Background: Hepatocellular carcinoma (HCC) represents a considerable burden to patients and health systems. Microvascular invasion (MVI) is a significant risk factor for HCC recurrence and survival after hepatectomy. We aimed to establish a preoperative MVI prediction model based on readily available clinical and radiographic characteristics using machine learning algorithms. Methods: Two independent cohorts of patients with HCC who underwent hepatectomy were included in the analysis and divided into a derivation set (466 patients), an internal validation set (182 patients), and an external validation set (140 patients). Least absolute shrinkage and selection operator (LASSO) analysis was used to optimize variable selection. We constructed the MVI prediction model using several machine learning algorithms, including logistic regression, k-nearest neighbors, support vector machine, decision tree, random forest, extreme gradient boosting, and neural network. Performance of the model was assessed in terms of discrimination, calibration, and clinical usefulness. Results: The three most significant variables associated with MVI-α-fetoprotein, protein induced by vitamin K absence or antagonist-II, and tumor size-were identified by the LASSO analysis. Among the machine learning algorithms, the logistic regression model achieved the largest area under the receiver operating characteristic curve and was presented in the form of a user-friendly, online calculator. The concordance (C)-statistic of the model was 0.745 [95% confidence interval (CI): 0.701-0.790] for the derivation set, 0.771 (95% CI: 0.703-0.839) for the internal validation set, and 0.812 (95% CI: 0.734-0.891) for the external validation set. The Hosmer-Lemeshow calibration test and calibration plot indicated a good fit for all 3 data sets. Decision curve analysis showed the model was clinically useful. Conclusions: This study provided a convenient and explainable approach for MVI prediction before surgical intervention. Our model may assist clinicians in determining the optimal therapeutic modality and facilitate precision medicine for HCC.

Thymidine kinase 1 drives hepatocellular carcinoma in enzyme-dependent and -independent manners.

Metabolic reprogramming plays a crucial role in the development of hepatocellular carcinoma (HCC). However, the key drivers of metabolic reprogramming underlying HCC progression remain unclear. Using a large-scale transcriptomic database and survival correlation screening, we identify thymidine kinase 1 (TK1) as a key driver. The progression of HCC is robustly mitigated by TK1 knockdown and significantly aggravated by its overexpression. Furthermore, TK1 promotes the oncogenic phenotypes of HCC not only through its enzymatic activity and production of deoxythymidine monophosphate (dTMP) but also by promoting glycolysis via binding with protein arginine methyltransferase 1 (PRMT1). Mechanistically, TK1 directly binds PRMT1 and stabilizes it by interrupting its interactions with tripartite-motif-containing 48 (TRIM48), which inhibits its ubiquitination-mediated degradation. Subsequently, we validate the therapeutic capacity of hepatic TK1 knockdown in a chemically induced HCC mouse model. Therefore, targeting both the enzyme-dependent and -independent activity of TK1 may be therapeutically promising for HCC treatment.

Hypoxia-associated circPRDM4 promotes immune escape via HIF-1α regulation of PD-L1 in hepatocellular carcinoma.

BACKGROUND: Hypoxia is a hallmark of cancer, and is closely intertwined with tumor immune evasion. Circular RNAs (circRNAs) have been implicated in tumor response to immune checkpoint blockades. However, hypoxia-associated circRNAs that orchestrate the association between hypoxia and response to immunotherapy remain poorly understood. Here, we aimed to determine the roles of hypoxia-associated circRNAs in immune escape of hepatocellular carcinoma (HCC) cells. METHODS: Differentially expressed hypoxia-associated circRNAs were determined using high-throughput sequencing technology. HCC patients treated with PD-1 blockade were enrolled to assess the clinical significance of circPRDM4. RT-qPCR, western blotting, flow cytometry, T cell-mediated tumor cell killing assay, and enzyme linked immunosorbent assay were used to investigate the roles of circPRDM4 in immune escape of HCC cells in vitro. Patient-derived xenograft mouse models and adoptive human tumor infiltrating lymphocyte-CD8+ T cell transfer were adopted to evaluate the effects of circPRDM4 in vivo. RNA pull-down, mass spectrometry, RNA immunoprecipitation, chromatin immunoprecipitation, chromatin isolation by RNA purification, dual-luciferase reporter assays, dot blotting, DNA in situ hybridization, and immunoprecipitation were utilized to examine the interaction between circPRDM4, HIF-1α, and CD274 promoter. RESULTS: We identified circPRDM4 as a hypoxia-associated circRNA in HCC. circPRDM4 was upregulated in responders to PD-1 blockade and associated with therapeutic efficacy. In vitro and in vivo experiments showed that circPRDM4 induced PD-L1 expression and promoted CD8+ T cell-mediated immune escape under hypoxic conditions. Mechanistically, circPRDM4 acted as a scaffold to recruit HIF-1α onto CD274 promoter, and cemented their interaction, ultimately promoting the HIF-1α-mediated transactivation of PD-L1. CONCLUSIONS: These findings illustrated that circPRDM4 promoted immune escape of HCC cells by facilitating the recruitment of HIF-1α onto the promoter of CD274 under hypoxia, thereby inhibiting CD8+ T cell infiltration in the tumor microenvironment. This work may provide a novel prognostic biomarker and therapeutic candidate for HCC immunotherapy.

GLIS1 intervention enhances anti-PD1 therapy for hepatocellular carcinoma by targeting SGK1-STAT3-PD1 pathway.

BACKGROUND: GLI-similar 1 (GLIS1) is one of of Krüppel-like zinc finger proteins, which are either stimulators or inhibitors of genetic transcription. Nevertheless, its effects on T cell were elusive. METHODS: In this study, we intend to explore the effects of GLIS1 on modulating the anticancer potency of CD8+ T cells in hepatocellular carcinoma (HCC). The expression of GLIS1 in CD8 peripheral blood mononuclear cell and CD8 tumor-infiltrating lymphocytes of HCC tissues was validated by quantificational real-time-PCR and flow cytometry. The anticancer potency of CD8+ T cells with GLIS1 knock down was confirmed in C57BL/6 mouse model and HCC patient-derived xenograft mice model. GLIS1-/- C57BL/6 mice was applied to explore the effects GLIS1 on tumor immune microenvironment. Chromatin immunoprecipitation and RNA transcriptome sequencing analysis were both performed in GLIS1-knock down of CD8+ T cells. RESULTS: GLIS1 was upregulated in exhausted CD8+ T cells in HCC. GLIS1 downregulation in CD8+ T cells repressed cancer development, elevated the infiltrate ability of CD8+ T cells, mitigated CD8+ T cell exhaustion and ameliorated the anti-PD1 reaction of CD8+ T cells in HCC. The causal link beneath this included transcriptional regulation of SGK1-STAT3-PD1 pathway by GLIS1, thereby maintaining the abundant PD1 expression on the surface of CD8+ T cells. CONCLUSION: Our study revealed that GLIS1 promoted CD8+ T cell exhaustion in HCC through transcriptional regulating SGK1-STAT3-PD1 pathway. Downregulating the expression of GLIS1 in CD8+ T cells exerted an effect with anti-PD1 treatment synergistically, revealing a prospective method for HCC immune therapy.