GPC3-targeted CAR-T cells expressing GLUT1 or AGK exhibit enhanced antitumor activity against hepatocellular carcinoma.

Chimeric antigen receptor-expressing T (CAR-T) cells induce robust antitumor responses in patients with hematologic malignancies. However, CAR-T cells exhibit only limited efficacy against solid tumors such as hepatocellular carcinoma (HCC), partially due to their limited expansion and persistence. CD8+ T cells, as key components of the adaptive immune response, play a central role in antitumor immunity. Aerobic glycolysis is the main metabolic feature of activated CD8+ T cells. In the tumor microenvironment, however, the uptake of large amounts of glucose by tumor cells and other immunosuppressive cells can impair the activation of T cells. Only when tumor-infiltrating lymphocytes (TILs) in the tumor microenvironment have a glycolytic advantage might the effector function of T cells be activated. Glucose transporter type 1 (GLUT1) and acylglycerol kinase (AGK) can boost glycolytic metabolism and activate the effector function of CD8+ T cells, respectively. In this study, we generated GPC3-targeted CAR-T cells overexpressing GLUT1 or AGK for the treatment of HCC. GPC3-targeted CAR-T cells overexpressing GLUT1 or AGK specifically and effectively lysed GPC3-positive tumor cells in vitro in an antigen-dependent manner. Furthermore, GLUT1 or AGK overexpression protected CAR-T cells from apoptosis during repeated exposures to tumor cells. Compared with second-generation CAR-T cells, GPC3-targeted CAR-T cells overexpressing GLUT1 or AGK exhibited greater CD8+ T-cell persistence in vivo and better antitumor effects in HCC allograft mouse models. Finally, we revealed that GLUT1 or AGK maintained anti-apoptosis ability in CD8+ T cells via activation of the PI3K/Akt pathway. This finding might identify a therapeutic strategy for advanced HCC.

AGK Potentiates Arterial Thrombosis by Affecting Talin-1 and αIIbß3-Mediated Bidirectional Signaling Pathway.

BACKGROUND: AGK (acylglycerol kinase) was first identified as a mitochondrial transmembrane protein that exhibits a lipid kinase function. Recent studies have established that AGK promotes cancer growth and metastasis, enhances glycolytic metabolism and function fitness of CD8+ T cells, or regulates megakaryocyte differentiation. However, the role of AGK in platelet activation and arterial thrombosis remains to be elaborated. METHODS: We performed hematologic analysis using automated hematology analyzer and investigated platelets morphology by transmission electron microscope. We explored the role of AGK in platelet activation and arterial thrombosis utilizing transgenic mice, platelet functional experiments in vitro, and thrombosis models in vivo. We revealed the regulation effect of AGK on Talin-1 by coimmunoprecipitation, mass spectrometry, immunofluorescence, and Western blot. We tested the role of AGK on lipid synthesis of phosphatidic acid/lysophosphatidic acid and thrombin generation by specific Elisa kits. RESULTS: In this study, we found that AGK depletion or AGK mutation had no effect on the platelet average volumes, the platelet microstructures, or the expression levels of the major platelet membrane receptors. However, AGK deficiency or AGK mutation conspicuously decreased multiple aspects of platelet activation, including agonists-induced platelet aggregation, granules secretion, JON/A binding, spreading on Fg (fibrinogen), and clot retraction. AGK deficiency or AGK mutation also obviously delayed arterial thrombus formation but had no effect on tail bleeding time and platelet procoagulant function. Mechanistic investigation revealed that AGK may promote Talin-1Ser425 phosphorylation and affect the αIIbß3-mediated bidirectional signaling pathway. However, AGK does not affect lipid synthesis of phosphatidic acid/lysophosphatidic acid in platelets. CONCLUSIONS: AGK, through its kinase activity, potentiates platelet activation and arterial thrombosis by promoting Talin-1 Ser425 phosphorylation and affecting the αIIbß3-mediated bidirectional signaling pathway.

The prognostic activity of acylglycerol kinase immunohistochemical expression in colon adenocarcinoma patients.

Introduction: Adenocarcinoma of the colon and rectum (COAD) is one of the most commonly diagnosed cancers of the gastrointestinal system. Acylglycerol kinase (AGK) is a known lipid kinase producing lysophosphatidic acid (LPA) from monoacylglycerol. It is widely expressed in the heart, brain, kidney, and muscle. Moreover, AGK is a significant cancer-related gene and is upregulated in many human malignancies, e.g. prostate cancer, breast cancer, oral squamous cell carcinoma, hepatocellular carcinoma, and renal carcinoma. However, the expression pattern and clinical significance of AGK in colon adenocarcinoma patients, especially in individuals living in Europe, remain unclear. Aim: The current study investigated the expression of AGK protein in colon adenocarcinoma samples to assess its prognostic significance by correlating its immunohistochemical expression with the clinicopathological variables and survival of individuals living in Poland. Material and methods: Tissue specimens were received from 110 colon adenocarcinoma patients who underwent surgical resection at the Municipal Hospital in Jaworzno in 2013-2015. The paraffin-embedded specimens were cut into 4-µm-thick sections and incubated with rabbit polyclonal antibody to AGK (final dilution 1 : 500) (Invitrogen; cat. number PA5-28566). Results and conclusions: AGK was strongly expressed in colon adenocarcinoma tissues in comparison to non-pathological colon specimens. The high level of AGK immunoexpression was demonstrated to be clearly correlated with the malignancy-related clinicopathological factors and 5-year overall survival rate of patients.

Acylglycerol kinase promotes ovarian cancer progression and regulates mitochondria function by interacting with ribosomal protein L39.

BACKGROUND: Epithelial ovarian cancer (EOC) is the leading cause of deaths among patients with gynecologic malignancies. In recent years, cancer stem cells (CSCs) have attracted great attention, which have been regarded as new biomarkers and targets in cancer diagnoses as well as therapies. However, therapeutic failure caused by chemotherapy resistance in late-stage EOC occurs frequently. The 5-year survival rate of patients with EOC remains at about 30%. METHODS: In this study, the expression of acylglycerol kinase (AGK) was analyzed among patients with EOC. The effect of AGK on EOC cell proliferation and tumorigenicity was studied using Western blotting, flow cytometry, EdU assay and in vivo xenotransplantation assays. Furthermore, AGK induced CSC-like properties and was resistant to cisplatin chemotherapy in the EOC cells, which were investigated through sphere formation assays and the in vivo model of chemoresistance. Finally, the relationship between AGK and RPL39 (Ribosomal protein L39) in mitochondria as well as their effect on the mitochondrial function was analyzed through methods including transmission electron microscopy, microarray, biotin identification and immunoprecipitation. RESULTS: AGK showed a markedly upregulated expression in EOC, which was significantly associated with the poor survival of patients with EOC, the expression of AGK-promoted EOC cell proliferation and tumorigenicity. AGK also induced CSC-like properties in the EOC cells and was resistant to cisplatin chemotherapy. Furthermore, the results indicated that AGK not only maintained mitochondrial cristae morphogenesis, but also increased the production of reactive oxygen species and Δψm of EOC cells in a kinase-independent manner. Finally, our results revealed that AGK played its biological function by directly interacting with RPL39. CONCLUSIONS: We demonstrated that AGK was a novel CSC biomarker for EOC, which the stemness of EOC was promoted and chemotherapy resistance was developed through physical as well as functional interaction with RPL39.

Downregulation of acylglycerol kinase suppresses high-glucose-induced endothelial-mesenchymal transition in human retinal microvascular endothelial cells through regulating the LPAR1/TGF-ß/Notch signaling pathway.

The endothelial-mesenchymal transition (EndMT) participates in the progression of diabetic retinopathy (DR), but cell-intrinsic factors modulating this process remain elusive. In this study, we explored the role of lysophosphatidic acid (LPA) - producing enzyme, acylglycerol kinase (AGK), in the EndMT of human retinal microvascular endothelial cells (HRECs) under high-glucose (HG) conditions. We found that AGK was significantly elevated in HG-treated cells. In addition, AGK knockdown reversed the HG-induced EndMT in HRECs, which was evidenced by the increased endothelial markers (CD31 and VE-cadherin) and decreased mesenchymal markers (FSP1 and α-SMA). Furthermore, downregulation of AGK inhibited the HG-induced activation of transforming growth factor ß (TGF-ß)/Notch pathways, whereas exogenous TGF-ß1 (10 ng/mL) impeded the inhibitory effects of AGK knockdown on HG-induced EndMT in HRECs. Additionally, the silencing of AGK abolished the HG-induced upregulation of LPA and its receptor, LPA receptor 1 (LPAR1), and overexpression of LPAR1 further rescued the AGK knockdown-mediated inhibition of the EndMT process. In conclusion, we demonstrate that downregulation of AGK suppresses HG-induced EndMT in HRECs through regulating the LPAR1/TGF-ß/Notch signaling pathway, indicating that AGK might be a potential therapeutic target for the treatment of DR.

Characterization of a Novel Splicing Variant in Acylglycerol Kinase (AGK) Associated with Fatal Sengers Syndrome.

Mitochondrial functional integrity depends on protein and lipid homeostasis in the mitochondrial membranes and disturbances in their accumulation can cause disease. AGK, a mitochondrial acylglycerol kinase, is not only involved in lipid signaling but is also a component of the TIM22 complex in the inner mitochondrial membrane, which mediates the import of a subset of membrane proteins. AGK mutations can alter both phospholipid metabolism and mitochondrial protein biogenesis, contributing to the pathogenesis of Sengers syndrome. We describe the case of an infant carrying a novel homozygous AGK variant, c.518+1G>A, who was born with congenital cataracts, pielic ectasia, critical congenital dilated myocardiopathy, and hyperlactacidemia and died 20 h after birth. Using the patient's DNA, we performed targeted sequencing of 314 nuclear genes encoding respiratory chain complex subunits and proteins implicated in mitochondrial oxidative phosphorylation (OXPHOS). A decrease of 96-bp in the length of the AGK cDNA sequence was detected. Decreases in the oxygen consumption rate (OCR) and the OCR:ECAR (extracellular acidification rate) ratio in the patient's fibroblasts indicated reduced electron flow through the respiratory chain, and spectrophotometry revealed decreased activity of OXPHOS complexes I and V. We demonstrate a clear defect in mitochondrial function in the patient's fibroblasts and describe the possible molecular mechanism underlying the pathogenicity of this novel AGK variant. Experimental validation using in vitro analysis allowed an accurate characterization of the disease-causing variant.

Acylglycerol Kinase-Targeted Therapies in Oncology.

Acylglycerol kinase (AGK) is a recently discovered mitochondrial lipid kinase, and mutation of its gene is the fundamental cause of Sengers syndrome. AGK is not only involved in the stability of lipid metabolism but also closely related to mitochondrial protein transport, glycolysis, and thrombocytopoiesis. Evidence indicates that AGK is an important factor in the occurrence and development of tumors. Specifically, AGK has been identified as an oncogene that partakes in the regulation of tumor cell growth, invasion, metastasis, and drug resistance. The versatility of AGK and its unique role in different types of cancerous and normal cells greatly piqued our interest. We believe that AGK is a promising target for cancer therapy. Therefore, this review summarizes the main research advances concerning AGK, including the discovery of its physiological/pathogenic mechanisms, and provides a reference for the feasible evaluation of AGK as a therapeutic target for human diseases, particularly tumors.

Case Report: Two Chinese Infants of Sengers Syndrome Caused by Mutations in AGK Gene.

Sengers syndrome (OMIM #212350) is a rare autosomal recessive disorder due to mutations in acylglycerol kinase (AGK) gene. We report two cases that were diagnosed clinically and confirmed genetically. Both infants had typical clinical features characterized by hypertrophic cardiomyopathy, bilateral cataracts, myopathy, and lactic acidosis, and heart failure was the most severe manifestation. Genetic testing of a boy revealed a homozygous pathogenic variant for Sengers syndrome in AGK (c.1131+2T>C) which was classified as likely pathogenic according to the ACMG guideline; besides, his skeletal muscle biopsy and transmission electron microscope presented obvious abnormity. One girl had compound heterozygous (c.409C>T and c.390G>A) variants of AGK gene that was identified in the proband and further Sanger sequencing indicated that the parents carried a single heterozygous mutation each. After the administration of "cocktail" therapy including coenzyme Q10, carnitine, and vitamin B complex, as well as ACEI, heart failure and myopathy of the boy were significantly improved and the condition was stable after 1-year follow-up, while the cardiomyopathy of the girl is not progressive but the plasma lactate acid increased significantly. We present the first report of two infants with Sengers syndrome diagnosed via exome sequencing in China.

Acylglycerol kinase promotes the stemness of nasopharyngeal carcinoma cells by promoting ß-catenin translocation to the nucleus through activating PI3K/Akt pathway.

Recent evidences show that acylglycerol kinase (AGK) expression is related to the occurrence and development of various human cancers. However, its roles in nasopharyngeal carcinoma (NPC) progression are still unclear. This work aims to explore the roles of AGK in NPC cell stemness. It was shown that AGK expression was higher in NPC tissues compared to the adjacent tissues. Online dataset analysis revealed that AGK expression was negatively correlated with the overall survival of NPC patients. Gain and loss of functional experiments demonstrated that AGK positively regulated the stemness of NPC cells, as evident by the change of the tumor sphere-formation ability, ALDH1 activity and expression of stemness critical regulators. KEGG analysis were performed to determine the potential pathways of AGK involved in NPC cell stemness and showed that the PI3K/Akt pathway exhibited the most correlation with AGK expression. Further mechanistic studies confirmed that AGK promoted the stemness of NPC cells through activating the PI3K/Akt pathway, and thus enhancing ß-catenin accumulation in nucleus. This study demonstrates a novel AGK/PI3K/Akt/ß-catenin axis involving in NPC cell stemness.

Novel Loss of Function in the AGK Gene: Rare Cause of End-Stage Heart Failure.

The authors present a case of mitochondrial cardiomyopathy due to a novel mutation of AGK gene that led to progressive heart failure. The cardiac magnetic resonance image findings of diffusely elevated relaxation time and increase in extracellular volume in the myocardium without early or late gadolinium enhancement may suggest mitochondrial cardiomyopathy. The authors emphasized the multidisciplinary team approach in the care of patients with mitochondrial cardiomyopathies. (Level of Difficulty: Advanced.).

Extending the phenotypic spectrum of Sengers syndrome: Congenital lactic acidosis with synthetic liver dysfunction.

Sengers syndrome is a rare autosomal recessive mitochondrial disease characterized by lactic acidosis, hypertrophic cardiomyopathy and bilateral cataracts. We present here a case of neonatal demise, within the first day of life, who initially presented with severe lactic acidosis, with evidence of both chorioamnionitis and cardiogenic shock. Initial metabolic labs demonstrated a severe lactic acidosis prompting genetic testing which revealed a homozygous pathogenic variant for Sengers syndrome in AGK, c.979A >  T; p.K327*. In addition to the canonical features of Sengers syndrome, our patient is the first reported case with liver dysfunction extending the phenotypic spectrum both in terms of severity and complications. This case also highlights the importance of maintaining a broad differential for congenital lactic acidosis.

Acylglycerol Kinase Mutated in Sengers Syndrome Is a Subunit of the TIM22 Protein Translocase in Mitochondria.

Mutations in mitochondrial acylglycerol kinase (AGK) cause Sengers syndrome, which is characterized by cataracts, hypertrophic cardiomyopathy, and skeletal myopathy. AGK generates phosphatidic acid and lysophosphatidic acid, bioactive phospholipids involved in lipid signaling and the regulation of tumor progression. However, the molecular mechanisms of the mitochondrial pathology remain enigmatic. Determining its mitochondrial interactome, we have identified AGK as a constituent of the TIM22 complex in the mitochondrial inner membrane. AGK assembles with TIMM22 and TIMM29 and supports the import of a subset of multi-spanning membrane proteins. The function of AGK as a subunit of the TIM22 complex does not depend on its kinase activity. However, enzymatically active AGK is required to maintain mitochondrial cristae morphogenesis and the apoptotic resistance of cells. The dual function of AGK as lipid kinase and constituent of the TIM22 complex reveals that disturbances in both phospholipid metabolism and mitochondrial protein biogenesis contribute to the pathogenesis of Sengers syndrome.

Sengers Syndrome-Associated Mitochondrial Acylglycerol Kinase Is a Subunit of the Human TIM22 Protein Import Complex.

Acylglycerol kinase (AGK) is a mitochondrial lipid kinase that catalyzes the phosphorylation of monoacylglycerol and diacylglycerol to lysophosphatidic acid and phosphatidic acid, respectively. Mutations in AGK cause Sengers syndrome, which is characterized by congenital cataracts, hypertrophic cardiomyopathy, skeletal myopathy, exercise intolerance, and lactic acidosis. Here we identified AGK as a subunit of the mitochondrial TIM22 protein import complex. We show that AGK functions in a kinase-independent manner to maintain the integrity of the TIM22 complex, where it facilitates the import and assembly of mitochondrial carrier proteins. Mitochondria isolated from Sengers syndrome patient cells and tissues show a destabilized TIM22 complex and defects in the biogenesis of carrier substrates. Consistent with this phenotype, we observe perturbations in the tricarboxylic acid (TCA) cycle in cells lacking AGK. Our identification of AGK as a bona fide subunit of TIM22 provides an exciting and unexpected link between mitochondrial protein import and Sengers syndrome.

Acylglycerol kinase functions as an oncogene and an unfavorable prognostic marker of human gliomas.

Acylglycerol kinase (AGK) regulates various cellular processes involved into tumorigenesis and tumor progression. To investigate involvement of AGK in human gliomas, here, quantitative real-time polymerase chain reaction, Western blot, and immunohistochemistry analyses were performed to respectively detect the expression of AGK mRNA and protein in glioma and nonneoplastic brain tissue specimens. Then, the associations of AGK expression with various clinicopathological characteristics and patients' prognosis were statistically evaluated. Moreover, the effects of siRNA-mediated AGK knockdown on glioma cell proliferation, migration, and invasion were respectively assessed via Cell Counting Kit-8 and Transwell assays in vitro. As a result, AGK expression, at both mRNA and protein levels, were markedly up-regulated in glioma tissues compared with nonneoplastic brain tissues (both P < .001). In addition, high AGK expression was significantly associated with the grade of malignancy and poor prognosis in glioma patients (all P < .05). Importantly, Cox regression model of multivariate analysis identified AGK expression as an independent prognostic factor for glioma patients (P = .03). Furthermore, silencing the expression of AGK dramatically suppressed cell proliferation, migration, and invasion of glioma cells in vitro (all P < .05). In conclusion, AGK up-regulation may be involved into glioma development and progression, highlighting its prognostic value for the treatment of patients with this malignancy. Further loss-of-function experiments suggest that AGK might play an important role in the viability and motility of glioma cells, implying its potentials as an attractive therapeutic target for this tumor.

Overexpression of acylglycerol kinase is associated with poorer prognosis and lymph node metastasis in nasopharyngeal carcinoma.

Acylglycerol kinase (AGK) has been reported to promote a malignant phenotype and enhance the development of cancer stem cells. However, the clinical value of AGK in cancer remains unclear. This study aimed to investigate the expression and clinicopathological significance of AGK in nasopharyngeal carcinoma (NPC). AGK was significantly upregulated in NPC cell lines and clinical specimens as indicated by real-time PCR and Western blotting. Among the AGK-positive cases, 52/114 (45.6 %) of the archived human NPC specimens expressed high levels of AGK. High expression of AGK was associated with significantly shorter overall and disease-free survival (P < 0.001 and P = 0.002; log-rank test) and was an independent prognostic factor for overall survival (P = 0.041; multivariate Cox analysis). High AGK expression was associated with lymph node metastasis (P < 0.001; chi-squared test) and was an independent predicted factor for lymph node metastasis in NPC (P = 0.032; multivariate logistic analysis). AGK is overexpressed and associated with disease progression and lymph node metastasis in NPC. AGK has potential as a novel prognostic factor for overall survival in NPC.