HKDC1 promotes tumor immune evasion in hepatocellular carcinoma by coupling cytoskeleton to STAT1 activation and PD-L1 expression.

Immune checkpoint blockade (ICB) has shown considerable promise for treating various malignancies, but only a subset of cancer patients benefit from immune checkpoint inhibitor therapy because of immune evasion and immune-related adverse events (irAEs). The mechanisms underlying how tumor cells regulate immune cell response remain largely unknown. Here we show that hexokinase domain component 1 (HKDC1) promotes tumor immune evasion in a CD8+ T cell-dependent manner by activating STAT1/PD-L1 in tumor cells. Mechanistically, HKDC1 binds to and presents cytosolic STAT1 to IFNGR1 on the plasma membrane following IFNγ-stimulation by associating with cytoskeleton protein ACTA2, resulting in STAT1 phosphorylation and nuclear translocation. HKDC1 inhibition in combination with anti-PD-1/PD-L1 enhances in vivo T cell antitumor response in liver cancer models in male mice. Clinical sample analysis indicates a correlation among HKDC1 expression, STAT1 phosphorylation, and survival in patients with hepatocellular carcinoma treated with atezolizumab (anti-PD-L1). These findings reveal a role for HKDC1 in regulating immune evasion by coupling cytoskeleton with STAT1 activation, providing a potential combination strategy to enhance antitumor immune responses.

Carnosine regulation of intracellular pH homeostasis promotes lysosome-dependent tumor immunoevasion.

Tumor cells and surrounding immune cells undergo metabolic reprogramming, leading to an acidic tumor microenvironment. However, it is unclear how tumor cells adapt to this acidic stress during tumor progression. Here we show that carnosine, a mobile buffering metabolite that accumulates under hypoxia in tumor cells, regulates intracellular pH homeostasis and drives lysosome-dependent tumor immune evasion. A previously unrecognized isoform of carnosine synthase, CARNS2, promotes carnosine synthesis under hypoxia. Carnosine maintains intracellular pH (pHi) homeostasis by functioning as a mobile proton carrier to accelerate cytosolic H+ mobility and release, which in turn controls lysosomal subcellular distribution, acidification and activity. Furthermore, by maintaining lysosomal activity, carnosine facilitates nuclear transcription factor X-box binding 1 (NFX1) degradation, triggering galectin-9 and T-cell-mediated immune escape and tumorigenesis. These findings indicate an unconventional mechanism for pHi regulation in cancer cells and demonstrate how lysosome contributes to immune evasion, thus providing a basis for development of combined therapeutic strategies against hepatocellular carcinoma that exploit disrupted pHi homeostasis with immune checkpoint blockade.

Mitochondria-localized cGAS suppresses ferroptosis to promote cancer progression.

A well-established role of cyclic GMP-AMP synthase (cGAS) is the recognition of cytosolic DNA, which is linked to the activation of host defense programs against pathogens via stimulator of interferon genes (STING)-dependent innate immune response. Recent advance has also revealed that cGAS may be involved in several noninfectious contexts by localizing to subcellular compartments other than the cytosol. However, the subcellular localization and function of cGAS in different biological conditions is unclear; in particular, its role in cancer progression remains poorly understood. Here we show that cGAS is localized to mitochondria and protects hepatocellular carcinoma cells from ferroptosis in vitro and in vivo. cGAS anchors to the outer mitochondrial membrane where it associates with dynamin-related protein 1 (DRP1) to facilitate its oligomerization. In the absence of cGAS or DRP1 oligomerization, mitochondrial ROS accumulation and ferroptosis increase, inhibiting tumor growth. Collectively, this previously unrecognized role for cGAS in orchestrating mitochondrial function and cancer progression suggests that cGAS interactions in mitochondria can serve as potential targets for new cancer interventions.

Secreted protease PRSS35 suppresses hepatocellular carcinoma by disabling CXCL2-mediated neutrophil extracellular traps.

Hepatocytes function largely through the secretion of proteins that regulate cell proliferation, metabolism, and intercellular communications. During the progression of hepatocellular carcinoma (HCC), the hepatocyte secretome changes dynamically as both a consequence and a causative factor in tumorigenesis, although the full scope of secreted protein function in this process remains unclear. Here, we show that the secreted pseudo serine protease PRSS35 functions as a tumor suppressor in HCC. Mechanistically, we demonstrate that active PRSS35 is processed via cleavage by proprotein convertases. Active PRSS35 then suppresses protein levels of CXCL2 through targeted cleavage of tandem lysine (KK) recognition motif. Consequently, CXCL2 degradation attenuates neutrophil recruitment to tumors and formation of neutrophil extracellular traps, ultimately suppressing HCC progression. These findings expand our understanding of the hepatocyte secretome's role in cancer development while providing a basis for the clinical translation of PRRS35 as a therapeutic target or diagnostic biomarker.

GAR-transferase contributes to purine synthesis and mitochondrion function to maintain fungal development and full virulence of Penicillium digitatum.

Penicillium digitatum is one of the most critical phytopathogens during the citrus postharvest period. However, the molecular mechanism of pathogenesis remains to be further explored. Purine is a multiple functional substance in organisms. To verify the role of the de novo purine biosynthesis (DNPB) pathway in P. digitatum, we investigated the third gene Pdgart, glycinamide ribonucleotide (GAR)-transferase, of this pathway in this study. The deletion mutant ΔPdgart was generated in the principle of homologous recombination via Agrobacterium tumefaciens-mediated transformation (ATMT). The phenotypic assay indicated that the ΔPdgart mutant displayed severe defects in hyphae growth, conidiation and germination, which can be rescued by the addition of exogenous ATP and AMP. Compared with wild-type strain N1, the ATP level of strain ΔPdgart was detected to be sharply declined during conidial germination, and this was resulted from the damage to purine synthesis and aerobic respiration. The pathogenicity assay suggested that mutant ΔPdgart infected citrus fruit but attenuated disease, which was owing to its reduced production of organic acids and activities of cell wall degradation enzymes. Additionally, the ΔPdgart mutant showed altered sensitivity to stress agents and fungicides. Taken together, the present study provides insights into the essential functions of Pdgart, and paves the way for further study and novel fungicide development.

Branched-chain amino acid catabolism breaks glutamine addiction to sustain hepatocellular carcinoma progression.

Branched-chain amino acid (BCAA) catabolism is related to tumorigenesis. However, the underlying mechanism and specific contexts in which BCAAs affect tumor progression remain unclear. Here, we demonstrate that BCAA catabolism is activated in liver cancer cells without glutamine. Enhanced BCAA catabolism leads to BCAA-derived carbon and nitrogen flow toward nucleotide synthesis, stimulating cell-cycle progression and promoting cell survival. Mechanistically, O-GlcNAcylation increases under glutamine-deprivation conditions and stabilizes the PPM1K protein, leading to dephosphorylation of BCKDHA and enhanced decomposition of BCAAs. Dephosphorylation of BCKDHA and high expression of PPM1K promote tumorigenesis in vitro and in vivo and are closely related to the poor prognosis of clinical patients with hepatocellular carcinoma (HCC). Inhibition of BCAA and glutamine metabolism can further retard HCC growth in vivo. These results not only elucidate a mechanism by which BCAA catabolism affects tumorigenesis but also identify pBCKDHA and PPM1K as potential therapeutic targets and predictive biomarkers.

Metformin sensitises hepatocarcinoma cells to methotrexate by targeting dihydrofolate reductase.

Metformin, the first-line drug for type II diabetes, has recently been considered an anticancer agent. However, the molecular target and underlying mechanism of metformin's anti-cancer effects remain largely unclear. Herein, we report that metformin treatment increases the sensitivity of hepatocarcinoma cells to methotrexate (MTX) by suppressing the expression of the one-carbon metabolism enzyme DHFR. We show that the combination of metformin and MTX blocks nucleotide metabolism and thus effectively inhibits cell cycle progression and tumorigenesis. Mechanistically, metformin not only transcriptionally represses DHFR via E2F4 but also promotes lysosomal degradation of the DHFR protein. Notably, metformin dramatically increases the response of patient-derived hepatocarcinoma organoids to MTX without obvious toxicity to organoids derived from normal liver tissue. Taken together, our findings identify an important role for DHFR in the suppressive effects of metformin on therapeutic resistance, thus revealing a therapeutically targetable potential vulnerability in hepatocarcinoma.

KDELR2 promotes breast cancer proliferation via HDAC3-mediated cell cycle progression.

BACKGROUND: Histone deacetylases (HDACs) engage in the regulation of various cellular processes by controlling global gene expression. The dysregulation of HDACs leads to carcinogenesis, making HDACs ideal targets for cancer therapy. However, the use of HDAC inhibitors (HDACi) as single agents has been shown to have limited success in treating solid tumors in clinical studies. This study aimed to identify a novel downstream effector of HDACs to provide a potential target for combination therapy. METHODS: Transcriptome sequencing and bioinformatics analysis were performed to screen for genes responsive to HDACi in breast cancer cells. The effects of HDACi on cell viability were detected using the MTT assay. The mRNA and protein levels of genes were determined by quantitative reverse transcription-PCR (qRT-PCR) and Western blotting. Cell cycle distribution and apoptosis were analyzed by flow cytometry. The binding of CREB1 (cAMP-response element binding protein 1) to the promoter of the KDELR (The KDEL (Lys-Asp-Glu-Leu) receptor) gene was validated by the ChIP (chromatin immunoprecipitation assay). The association between KDELR2 and protein of centriole 5 (POC5) was detected by immunoprecipitation. A breast cancer-bearing mouse model was employed to analyze the effect of the HDAC3-KDELR2 axis on tumor growth. RESULTS: KDELR2 was identified as a novel target of HDAC3, and its aberrant expression indicated the poor prognosis of breast cancer patients. We found a strong correlation between the protein expression patterns of HADC3 and KDELR2 in tumor tissues from breast cancer patients. The results of the ChIP assay and qRT-PCR analysis validated that HDAC3 transactivated KDELR2 via CREB1. The HDAC3-KDELR2 axis accelerated the cell cycle progression of cancer cells by protecting the centrosomal protein POC5 from proteasomal degradation. Moreover, the HDAC3-KDELR2 axis promoted breast cancer cell proliferation and tumorigenesis in vitro and in vivo. CONCLUSION: Our results uncovered a previously unappreciated function of KDELR2 in tumorigenesis, linking a critical Golgi-the endoplasmic reticulum traffic transport protein to HDAC-controlled cell cycle progression on the path of cancer development and thus revealing a potential therapeutical target for breast cancer.

Comparison of translabyrinthine and retrosigmoid approach for treating vestibular schwannoma: A meta-analysis.

BACKGROUND: To date, the literature directly comparing the translabyrinthine approach and retrosigmoid approach in the operation of patients with vestibular schwannoma was limited. We aimed to evaluate postoperative complications between translabyrinthine approach and retrosigmoid approach for treating vestibular schwannoma patients. MATERIAL AND METHOD: Potential publications were selected from PubMed, Web of Science and Cochrane Library. Gray relevant studies were manually searched. We set the searching time spanning from the creation date of electronic engines to February 2020. STATA version 12.0 was exerted to process the pooled data. RESULTS: A total of 9 literature included in the study, involving 2429 patients, hails from the Germany, USA, Canada, Italy, and France. Of these 2429 patients with vestibular schwannoma, there were 1628 cases from the translabyrinthine approach group versus 801 cases from the retrosigmoid approach group. The results demonstrated that the translabyrinthine approach group was associated with a lower rate of tinnitus (OR = 2.687; 95 %CI, 1.167-6.191; P = 0.02) and cranial nerve deficit (OR = 2.946; 95 %CI, 1.562-5.557; P = 0.001). And the translabyrinthine approach group was associated with a higher total resection rate (OR = 0.246; 95 %CI (0.071-0.848); P = 0.026). However, no statistic differences were found in the incidence of the near total (OR = 0.751; P = 0.351), subtotal resection (OR = 3.664; P = 0.109), postoperative facial nerve dysfunctions (OR, 0.763; P = 0.626), postoperative meningitis (OR = 2.7; P = 0.279), cerebrospinal fluid leak (OR = 1.225; P = 0.777), postoperative headache (OR = 1.412; P = 0.339), ophthalmic complications (OR = 0.87; P = 0.59), and vascular complications (OR = 2.501; P = 0.139). CONCLUSION: Based on current evidence, the translabyrinthine approach was associated with a higher rate of total resection and a lower rate of the tinnitus and cranial nerve deficit. But the risk of cranial nerve deficit was clearly affected by the preoperative status. And a translabyrintine approach could imply a complete sensorineural hearing loss, which contribute to the lower rate of postoperative tinnitus. Consequently, more evidence-based researches are needed to supplement this opinion.

Lin28 enhances de novo fatty acid synthesis to promote cancer progression via SREBP-1.

Lin28 plays an important role in promoting tumor development, whereas its exact functions and underlying mechanisms are largely unknown. Here, we show that both human homologs of Lin28 accelerate de novo fatty acid synthesis and promote the conversion from saturated to unsaturated fatty acids via the regulation of SREBP-1. By directly binding to the mRNAs of both SREBP-1 and SCAP, Lin28A/B enhance the translation and maturation of SREBP-1, and protect cancer cells from lipotoxicity. Lin28A/B-stimulated tumor growth is abrogated by SREBP-1 inhibition and by the impairment of the RNA binding properties of Lin28A/B, respectively. Collectively, our findings uncover that post-transcriptional regulation by Lin28A/B enhances de novo fatty acid synthesis and metabolic conversion of saturated and unsaturated fatty acids via SREBP-1, which is critical for cancer progression.

DIS3L2 Promotes Progression of Hepatocellular Carcinoma via hnRNP U-Mediated Alternative Splicing.

DIS3-like 3'-5' exoribonuclease 2 (DIS3L2) degrades aberrant RNAs, however, its function in tumorigenesis remains largely unexplored. Here, aberrant DIS3L2 expression promoted human hepatocellular carcinoma (HCC) progression via heterogeneous nuclear ribonucleoproteins (hnRNP) U-mediated alternative splicing. DIS3L2 directly interacted with hnRNP U through its cold-shock domains and promoted inclusion of exon 3b during splicing of pre-Rac1 independent of its exonuclease activity, yielding an oncogenic splicing variant, Rac1b, which is known to stimulate cellular transformation and tumorigenesis. DIS3L2 regulated alternative splicing by recruiting hnRNP U to pre-Rac1. Rac1b was critical for DIS3L2 promotion of liver cancer development both in vitro and in vivo. Importantly, DIS3L2 and Rac1b expression highly correlated with HCC progression and patient survival. Taken together, our findings uncover an oncogenic role of DIS3L2, in which it promotes liver cancer progression through a previously unappreciated mechanism of regulating hnRNP U-mediated alterative splicing. SIGNIFICANCE: These findings establish the role and mechanism of the 3'-5' exoribonuclease DIS3L2 in hepatocellular carcinoma carcinogenesis.

Chronic nicotine exposure impairs uncertainty modulation on reinforcement learning in anterior cingulate cortex and serotonin system.

Deficits in the computational processes of reinforcement learning have been suggested to underlie addiction. Additionally, environmental uncertainty, which is encoded in the anterior cingulate cortex (ACC), modulates reward prediction errors (RPEs) during reinforcement learning and exacerbates addiction. The present study tested whether and how the ACC would have an essential role in drug addiction by failing to use uncertainty to modulate the RPEs during reinforcement learning. In Experiment I, we found that the ACC/medial prefrontal cortex (MPFC) did not modulate RPE learning according to uncertainty in smokers. The effect of uncertainty × RPE in the ACC/MPFC was correlated with the learning rate of RPEs and the duration of nicotine use. Experiment II demonstrated that serotonin, but not dopamine, receptor mRNA expression significantly decreased in the ACC of the nicotine exposed compared to the control rats. Furthermore, there was a positive correlation between learning rate and serotonin receptor mRNA expression in the ACC. Therefore, all present results suggest that impairments in uncertainty modulation in the ACC disrupt reinforcement learning processes in chronic nicotine users and contribute to maladaptive decision-making. These findings support interventions for pathological decision-making in drug addiction that strongly focus on the serotonin system in ACC.

CUE domain-containing protein 2 promotes the Warburg effect and tumorigenesis.

Cancer progression depends on cellular metabolic reprogramming as both direct and indirect consequence of oncogenic lesions; however, the underlying mechanisms are still poorly understood. Here, we report that CUEDC2 (CUE domain-containing protein 2) plays a vital role in facilitating aerobic glycolysis, or Warburg effect, in cancer cells. Mechanistically, we show that CUEDC2 upregulates the two key glycolytic proteins GLUT3 and LDHA via interacting with the glucocorticoid receptor (GR) or 14-3-3ζ, respectively. We further demonstrate that enhanced aerobic glycolysis is essential for the role of CUEDC2 to drive cancer progression. Moreover, using tissue microarray analysis, we show a correlation between the aberrant expression of CUEDC2, and GLUT3 and LDHA in clinical HCC samples, further demonstrating a link between CUEDC2 and the Warburg effect during cancer development. Taken together, our findings reveal a previously unappreciated function of CUEDC2 in cancer cell metabolism and tumorigenesis, illustrating how close oncogenic lesions are intertwined with metabolic alterations promoting cancer progression.

cMyc-mediated activation of serine biosynthesis pathway is critical for cancer progression under nutrient deprivation conditions.

Cancer cells are known to undergo metabolic reprogramming to sustain survival and rapid proliferation, however, it remains to be fully elucidated how oncogenic lesions coordinate the metabolic switch under various stressed conditions. Here we show that deprivation of glucose or glutamine, two major nutrition sources for cancer cells, dramatically activated serine biosynthesis pathway (SSP) that was accompanied by elevated cMyc expression. We further identified that cMyc stimulated SSP activation by transcriptionally upregulating expression of multiple SSP enzymes. Moreover, we demonstrated that SSP activation facilitated by cMyc led to elevated glutathione (GSH) production, cell cycle progression and nucleic acid synthesis, which are essential for cell survival and proliferation especially under nutrient-deprived conditions. We further uncovered that phosphoserine phosphatase (PSPH), the final rate-limiting enzyme of the SSP pathway, is critical for cMyc-driven cancer progression both in vitro and in vivo, and importantly, aberrant expression of PSPH is highly correlated with mortality in hepatocellular carcinoma (HCC) patients, suggesting a potential causal relation between this cMyc-regulated enzyme, or SSP activation in general, and cancer development. Taken together, our results reveal that aberrant expression of cMyc leads to the enhanced SSP activation, an essential part of metabolic switch, to facilitate cancer progression under nutrient-deprived conditions.

Lin28/let-7 axis regulates aerobic glycolysis and cancer progression via PDK1.

Aberrant expression of Lin28 and let-7 has been observed in many human malignancies. However, its functions and underlying mechanisms remain largely elusive. Here we show that aberrant expression of Lin28 and let-7 facilitates aerobic glycolysis, or Warburg effect, in cancer cells. Mechanistically, we discover that Lin28A and Lin28B enhance, whereas let-7 suppresses, aerobic glycolysis via targeting pyruvate dehydrogenase kinase 1, or PDK1, in a hypoxia- or hypoxia-inducible factor-1 (HIF-1)-independent manner, illustrating a novel pathway to mediate aerobic glycolysis of cancer cells even in ambient oxygen levels. Importantly, we further demonstrate that PDK1 is critical for Lin28A- and Lin28B-mediated cancer proliferation both in vitro and in vivo, establishing a previously unappreciated mechanism by which Lin28/let-7 axis facilitates Warburg effect to promote cancer progression. Our findings suggest a potential rationale to target PDK1 for cancer therapy in malignancies with aberrant expression of Lin28 and let-7.

HIF-1-mediated suppression of acyl-CoA dehydrogenases and fatty acid oxidation is critical for cancer progression.

Hypoxia-inducible factor 1 (HIF-1) mediates a metabolic switch that blocks the conversion of pyruvate to acetyl-CoA in cancer cells. Here, we report that HIF-1α also inhibits fatty acid ß-oxidation (FAO), another major source of acetyl-CoA. We identified a PGC-1ß-mediated pathway by which HIF-1 inhibits the medium- and long-chain acyl-CoA dehydrogenases (MCAD and LCAD), resulting in decreased reactive oxygen species levels and enhanced proliferation. Surprisingly, we further uncovered that blocking LCAD, but not MCAD, blunts PTEN expression and dramatically affects tumor growth in vivo. Analysis of 158 liver cancer samples showed that decreased LCAD expression predicts patient mortality. Altogether, we have identified a previously unappreciated mechanism by which HIF-1 suppresses FAO to facilitate cancer progression.

Human fibroblast reprogramming to pluripotent stem cells regulated by the miR19a/b-PTEN axis.

Induction of pluripotent stem cells (iPSC) by defined transcription factors is the recognized canonical means for somatic reprogramming, however, it remains incompletely understood how individual transcription factors affect cell fate decisions during the reprogramming process. Here, we report induction of fibroblast reprogramming by various transcriptional factors is mediated by a miR19a/b-PTEN axis. cMyc, one of the four Yamanaka factors known to stimulate both somatic cell reprogramming and tumorigenesis, induced the expression of multiple mircoRNAs, miR-17 ∼ 92 cluster in particular, in the early stage of reprogramming of human fibroblasts. Importantly, miR-17 ∼ 92 cluster could greatly enhance human fibroblast reprogramming induced by either the four Yamanaka factors (Oct4, Sox2, Klf4, and cMyc, or 4F) or the first three transcriptional factors (Oct4, Sox2, and Klf4, or 3F). Among members of this microRNA cluster, miR-19a/b exhibited the most potent effect on stimulating fibroblst reprogramming to iPSCs. Additional studies revealed that miR-19a/b enhanced iPSC induction efficiency by targeted inhibition of phosphatase and tensin homolog (PTEN), a renowned tumor suppressor whose loss-of-function mutations were found in multiple human malignancies. Our results thus demonstrate an important role of miR-19a/b-PTEN axis in the reprogramming of human fibroblasts, illustrating that the somatic reprogramming process and its underlying regulation pathways are intertwined with oncogenic signaling in human malignancies.