Metformin Promotes Antitumor Immunity via Endoplasmic-Reticulum-Associated Degradation of PD-L1.

Metformin has been reported to possess antitumor activity and maintain high cytotoxic T lymphocyte (CTL) immune surveillance. However, the functions and detailed mechanisms of metformin's role in cancer immunity are not fully understood. Here, we show that metformin increases CTL activity by reducing the stability and membrane localization of programmed death ligand-1 (PD-L1). Furthermore, we discover that AMP-activated protein kinase (AMPK) activated by metformin directly phosphorylates S195 of PD-L1. S195 phosphorylation induces abnormal PD-L1 glycosylation, resulting in its ER accumulation and ER-associated protein degradation (ERAD). Consistently, tumor tissues from metformin-treated breast cancer patients exhibit reduced PD-L1 levels with AMPK activation. Blocking the inhibitory signal of PD-L1 by metformin enhances CTL activity against cancer cells. Our findings identify a new regulatory mechanism of PD-L1 expression through the ERAD pathway and suggest that the metformin-CTLA4 blockade combination has the potential to increase the efficacy of immunotherapy.

Ephrin receptor A10 monoclonal antibodies and the derived chimeric antigen receptor T cells exert an antitumor response in mouse models of triple-negative breast cancer.

Expression of the receptor tyrosine kinase ephrin receptor A10 (EphA10), which is undetectable in most normal tissues except for the male testis, has been shown to correlate with tumor progression and poor prognosis in several malignancies, including triple-negative breast cancer (TNBC). Therefore, EphA10 could be a potential therapeutic target, likely with minimal adverse effects. However, no effective clinical drugs against EphA10 are currently available. Here, we report high expression levels of EphA10 in tumor regions of breast, lung, and ovarian cancers as well as in immunosuppressive myeloid cells in the tumor microenvironment. Furthermore, we developed anti-EphA10 monoclonal antibodies (mAbs) that specifically recognize cell surface EphA10, but not other EphA family isoforms, and target tumor regions precisely in vivo with no apparent accumulation in other organs. In syngeneic TNBC mouse models, we found that anti-EphA10 mAb clone #4 enhanced tumor regression, therapeutic response rate, and T cell-mediated antitumor immunity. Notably, the chimeric antigen receptor T cells derived from clone #4 significantly inhibited TNBC cell viability in vitro and tumor growth in vivo. Together, our findings suggest that targeting EphA10 via EphA10 mAbs and EphA10-specific chimeric antigen receptor-T cell therapy may represent a promising strategy for patients with EphA10-positive tumors.

Tafenoquine and its derivatives as inhibitors for the severe acute respiratory syndrome coronavirus 2.

The pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has severely affected human lives around the world as well as the global economy. Therefore, effective treatments against COVID-19 are urgently needed. Here, we screened a library containing Food and Drug Administration (FDA)-approved compounds to identify drugs that could target the SARS-CoV-2 main protease (Mpro), which is indispensable for viral protein maturation and regard as an important therapeutic target. We identified antimalarial drug tafenoquine (TFQ), which is approved for radical cure of Plasmodium vivax and malaria prophylaxis, as a top candidate to inhibit Mpro protease activity. The crystal structure of SARS-CoV-2 Mpro in complex with TFQ revealed that TFQ noncovalently bound to and reshaped the substrate-binding pocket of Mpro by altering the loop region (residues 139-144) near the catalytic Cys145, which could block the catalysis of its peptide substrates. We also found that TFQ inhibited human transmembrane protease serine 2 (TMPRSS2). Furthermore, one TFQ derivative, compound 7, showed a better therapeutic index than TFQ on TMPRSS2 and may therefore inhibit the infectibility of SARS-CoV-2, including that of several mutant variants. These results suggest new potential strategies to block infection of SARS-CoV-2 and rising variants.

Interplay between lncRNA RP11-367G18.1 variant 2 and YY1 plays a vital role in hypoxia-mediated gene expression and tumorigenesis.

BACKGROUND: The hypoxia-responsive long non-coding RNA, RP11-367G18.1, has recently been reported to induce histone 4 lysine 16 acetylation (H4K16Ac) through its variant 2; however, the underlying molecular mechanism remains poorly understood. METHODS: RNA pull-down assay and liquid chromatography-tandem mass spectrometry were performed to identify RP11-367G18.1 variant 2-binding partner. The molecular events were examined utilizing western blot analysis, real-time PCR, luciferase reporter assay, chromatin immunoprecipitation, and chromatin isolation by RNA purification assays. The migration, invasion, soft agar colony formation, and in vivo xenograft experiments were conducted to evaluate the impact of RP11-367G18.1 variant 2-YY1 complex on tumor progression. RESULTS: In this study, RNA sequencing data revealed that hypoxia and RP11-367G18.1 variant 2 co-regulated genes were enriched in tumor-related pathways. YY1 was identified as an RP11-367G18.1 variant 2-binding partner that activates the H4K16Ac mark. YY1 was upregulated under hypoxic conditions and served as a target gene for hypoxia-inducible factor-1α. RP11-367G18.1 variant 2 colocalized with YY1 and H4K16Ac in the nucleus under hypoxic conditions. Head and neck cancer tissues had higher levels of RP11-367G18.1 and YY1 which were associated with poor patient outcomes. RP11-367G18.1 variant 2-YY1 complex contributes to hypoxia-induced epithelial-mesenchymal transition, cell migration, invasion, and tumorigenicity. YY1 regulated hypoxia-induced genes dependent on RP11-367G18.1 variant 2. CONCLUSIONS: RP11-367G18.1 variant 2-YY1 complex mediates the tumor-promoting effects of hypoxia, suggesting that this complex can be targeted as a novel therapeutic strategy for cancer treatment.

Nomogram to predict 3-month unfavorable outcome after thrombectomy for stroke.

BACKGROUND: Mechanical thrombectomy (MT) is an effective treatment for large-vessel occlusion in acute ischemic stroke, however, only some revascularized patients have a good prognosis. For stroke patients undergoing MT, predicting the risk of unfavorable outcomes and adjusting the treatment strategies accordingly can greatly improve prognosis. Therefore, we aimed to develop and validate a nomogram that can predict 3-month unfavorable outcomes for individual stroke patient treated with MT. METHODS: We analyzed 258 patients with acute ischemic stroke who underwent MT from January 2018 to February 2021. The primary outcome was a 3-month unfavorable outcome, assessed using the modified Rankin Scale (mRS), 3-6. A nomogram was generated based on a multivariable logistic model. We used the area under the receiver-operating characteristic curve to evaluate the discriminative performance and used the calibration curve and Spiegelhalter's Z-test to assess the calibration performance of the risk prediction model. RESULTS: In our visual nomogram, gender (odds ratio [OR], 3.40; 95%CI, 1.54-7.54), collateral circulation (OR, 0.46; 95%CI, 0.28-0.76), postoperative mTICI (OR, 0.06; 95%CI, 0.01-0.50), stroke-associated pneumonia (OR, 5.76; 95%CI, 2.79-11.87), preoperative Na (OR, 0.82; 95%CI, 0.72-0.92) and creatinine (OR, 1.02; 95%CI, 1.01-1.03) remained independent predictors of 3-month unfavorable outcomes in stroke patients treated with MT. The area under the nomogram curve was 0.8791 with good calibration performance (P = 0.873 for the Spiegelhalter's Z-test). CONCLUSIONS: A novel nomogram consisting of gender, collateral circulation, postoperative mTICI, stroke-associated pneumonia, preoperative Na and creatinine can predict the 3-month unfavorable outcomes in stroke patients treated with MT.

ATXN7L3B promotes hepatocellular carcinoma stemness and is downregulated by metformin.

Hepatocellular carcinoma (HCC) is the major cause of liver cancer-associated morality. Metformin, used for treating type 2 diabetes, has antitumor activity and reduces the risk of some diabetes-related tumors, such as liver and breast cancer. However, the mechanisms underlying metformin's effects in HCC remain unclear. To identify genes associated with metformin treatment in HCC, we conducted transcriptomic and proteomic analyses in HCC cells treated with or without metformin. We identified 41 differentially expressed genes upon metformin treatment. Among them, Ataxin 7 Like 3B (ATXN7L3B), which is a negative regulator of the Spt-Ada-Gcn5 acetyltransferase (SAGA) deubiquitinase (DUB) module and has relatively unknown functions in cancer, attracted our attention. We observed that metformin reduced ATXN7L3B level in HCC cells. ATXN7L3B expression was significantly negatively correlated with survival in liver cancer patients. We also demonstrated that ATXN7L3B promoted HCC stemness. Metformin treatment decreased ATXN7L3B-induced tumor-initiating ability in a HCC mouse model, implying that metformin may inhibit cancer stemness by downregulating ATXN7L3B. Our study supports the antitumor activity of metformin and its potential as an anticancer drug for HCC treatment.

Ideal physical activity in association with incident ankylosing spondylitis: a community-based, prospective cohort study.

OBJECTIVES: Only limited risk factors for ankylosing spondylitis (AS) have been identified to date. Therefore, we aimed to explore whether cardiovascular health (CVH) behaviours and factors are associated with the risk of developing AS. METHODS: Patients with incident AS were identified in cohorts from two ongoing prospective studies. Assessments were made of the association of AS with individual baseline cardiovascular health lifestyle behaviours (including smoking status, body mass index, physical activity and diet) and cardiovascular health factors (including total cholesterol levels, blood pressure levels and fasting plasma glucose levels), and with a cardiovascular health metric determined by the number of ideal behaviours and factors. Cox regression analysis was used for the estimation of hazard ratios (HRs) for AS. RESULTS: Among 124,303 participants, incident AS was identified in 53 individuals within the 8 years of follow-up. For participants with ideal physical activity (>80 min/week) the HR was 0.21 (95% CI 0.05-0.89) compared with participants without ideal physical activity after adjusting for potential confounders. No signi cant risk of developing AS was associated with baseline smoking, diet, body mass index, blood pressure, fasting blood glucose or total cholesterol status, nor did cardiovascular health metrics. CONCLUSIONS: Adherence to ideal physical activity may reduce the risk of developing AS.

Using esophagus organoid to explore the role of c-Myc in esophageal cancer initiation.

C-Myc gene is aberrantly highly expressed and participates in cancer initiation and development in various malignant tumors including esophageal cancer, while the underlying mechanism(s) still remains unclear. In order to explore the role of c-Myc in the occurrence of esophageal cancer, we successfully established the esophageal organoids (EOs) as the research model. By constructing a lentivirus overexpressing c-Myc and developing more effective infection method, EOs with stable overexpression of c-Myc were efficiently obtained. The morphologies of EOs with or without overexpressing c-Myc were first analyzed with ImageJ, which showed no difference between two groups during continuous subculture. Subsequently, we applied immunofluorescence and CCK8 assays to evaluate the cell proliferation, and the results showed no change in the c-Myc-overexpressed group as compared to control EOs. Furthermore, qPCR was used to detect the expression of genes that are related to cell cycle, cell metabolism as well as esophageal cancer. The results indicated the expression of these genes was not significantly increased in the c-Myc overexpressing EOs. In conclude, we discovered that overexpression of c-Myc gene alone in the esophagus organoid is not sufficient to induce carcinogenesis in esophageal carcinoma. In this study, we successfully established an esophagus organoid culture system and together with efficient lentivirus-infection method for investigation on the effects of overexpressing c-Myc in esophageal cancer. Our work demonstrated a promising research model for the study of esophagus development and esophageal cancer.

MT4-MMP promotes invadopodia formation and cell motility in FaDu head and neck cancer cells.

Hypoxia-inducible factor-1α (HIF-1α) induces cancer metastasis. We previously demonstrated that HIF-1α-induced membrane-type 4 matrix metalloproteinase (MT4-MMP) is involved in hypoxia-mediated metastasis in head and neck squamous cell carcinoma (HNSCC). However, the functions and detailed mechanisms of MT4-MMP in cancer metastasis are not well understood. In this study, we investigated whether MT4-MMP regulates invadopodia formation or individual cell movement-both critical to cancer migration and invasion-in three-dimensional (3D) environments. By expressing MT4-MMP in the HNSCC cell line FaDu, we demonstrated that MT4-MMP increases invadopodia formation and gelatin degradation. Furthermore, the amoeboid-like cell movement on collagen gel was increased by MT4-MMP expression in FaDu cells. Mechanistically, MT4-MMP may induce invadopodia formation by binding with Tks5 and PDGFRα to result in Src activation and promote amoeboid-like movement by stimulating the small GTPases Rho and Cdc42. Altogether, our data indicate that MT4-MMP induces two crucial mechanisms of cancer dissemination, invadopodia formation and amoeboid movement, and elucidate the prometastatic role of MT4-MMP in hypoxia-mediated cancer metastasis.

Left Atrial Enlargement is Associated with Stroke Severity with Cardioembolic and Cryptogenic Subtypes in a Chinese Population.

BACKGROUND: Left atrial enlargement is associated with increased risk for stroke. However, few studies that evaluated the correlation between left atrial size and ischemic stroke severity. In this study, we aim to evaluate the association between left atrial size and stroke severity, especially with cardioembolic and cryptogenic stroke in the Chinese population. METHODS: A total of 1271 patients with acute ischemic stroke were included in this study. Echocardiographic left atrial diameter was measured and indexed to height. Stroke severity was assessed at admission with the National Institutes of Health Stroke Scale (NIHSS). Moderate-to-severe neurologic deficit was defined as NIHSS greater than or equal to 5. Patients were divided into mild, moderate, or severe abnormal left atrial size by tertile distribution. Binary logistic regression analysis was used to identify independent predictors of severe stroke after adjustment. RESULTS: Among all enrolled patients, 328 (25.8%) were classified into moderate-to severe stroke severity (NIHSS ≥ 5). In the multivariable model, compared with the lowest tertile of left atrial size, the odds ratio for moderate-to-severe neurologic deficit was 0.902 (95% CI, 0.644-1.264, P = .550) when left atrial size was the highest tertile. Of all patients, 190 patients were further categorized as cardioembolic and cryptogenic subtypes, and 70 (36.8%) were classified into moderate-to-severe stroke severity. After adjusting for confounders, compared with the lowest tertile, the top tertile of left atrial size was significantly associated with moderate-to-severe stroke (3.156, 95% CI, 1.143-8.711, P = .027). CONCLUSION: Left atrial enlargement was associated with more severe initial neurologic deficits of embolic subtypes (cardioembolic and cryptogenic stroke) in patients with acute ischemic stroke.

An immunosuppressive peptide from the horsefly inhibits inflammation by repressing macrophage maturation and phagocytosis.

Ectoparasites repress host immune responses while they obtain nutrition from their hosts. Understanding the immunosuppressive mechanisms between ectoparasites and their hosts will provide new strategies to develop potential immunosuppressive drugs against immune disorder diseases. Previously, we have discovered that a small peptide, immunoregulin HA, from the horsefly (Hybomitra atriperoides) may play an immunosuppressive role in rat splenocytes. However, the targeting cells and detailed mechanisms of immunoregulin HA in immunosuppressive reactions are not well defined. Here, we show that immunoregulin HA reduces the secretion of proinflammatory cytokines upon lipopolysaccharide (LPS) stimulation. Interestingly, we discover that the major cytokines repressed by immunoregulin HA are secreted by macrophages, rather than by T cells. Furthermore, immunoregulin HA inhibits macrophage maturation and phagocytosis. Mechanically, the activations of c-JUN N-terminal kinase and extracellular signal-regulated kinase upon LPS stimulation are decreased by immunoregulin HA. Consistently, immunoregulin HA treatment exhibits an anti-inflammatory activity in a mouse model of adjuvant-induced paw inflammation. Taken together, our data reveal that immunoregulin HA conducts the anti-inflammatory activity by blocking macrophage functions.

Epithelial-mesenchymal transition softens head and neck cancer cells to facilitate migration in 3D environments.

The biological impact and signalling of epithelial-mesenchymal transition (EMT) during cancer metastasis has been established. However, the changes in biophysical properties of cancer cells undergoing EMT remain elusive. Here, we measured, via video particle tracking microrheology, the intracellular stiffness of head and neck cancer cell lines with distinct EMT phenotypes. We also examined cells migration and invasiveness in different extracellular matrix architectures and EMT-related signalling in these cell lines. Our results show that when cells were cultivated in three-dimensional (3D) environments, the differences in cell morphology, migration speed, invasion capability and intracellular stiffness were more pronounced among different head and neck cancer cell lines with distinct EMT phenotypes than those cultivated in traditional plastic dishes and/or seated on top of a thick layer of collagen. An inverse correlation between intracellular stiffness and invasiveness in 3D culture was revealed. Knock-down of the EMT regulator Twist1 or Snail or inhibition of Rac1 which is a downstream GTPase of Twist1 increased intracellular stiffness. These results indicate that the EMT regulators, Twist1 and Snail and the mediated signals play a critical role in reducing intracellular stiffness and enhancing cell migration in EMT to promote cancer cells invasion.

[Effects of Salidroside on Tic Behavior of Tourette Syndrome Model Rats].

OBJECTIVE: To observe the effect of salidroside on tic behavior and in vivo dopamine DA) and serotonin (5-HT) levels in Tourette syndrome (TS) model rats. METHODS: Forty rats were randomly divided into the blank control group, the TS model group, the haloperidol-treated group (0.5 mg/kg x d(-1)), and the salidroside-treated group (50 mg/kg x d(-1)), 10 in each group. TS rat model was induced by imino-dipropio-nitrile (IDPN). Peritoneal injection of haloperidol and salidroside was started from the 4th day of modeling in the haloperidol-treated group and the salidroside-treated group respectively. Normal saline was peritoneally injected to rats in the blank control group and the TS model group respectively. Stereotyped behavior was scored, and changes of DA and 5-HT levels in blood and striatum were measured before modeling, after modeling, and after intervention. RESULTS: Compared with the blank control group, the score of the tic behavior was elevated (P < 0.01) , levels of DA and 5-HT in plasma and striatum were reduced in the model group (P < 0.01, P < 0.05). Compared with the same group after modeling, the tic behavior score decreased and plasma DA levels increased in the two treated groups after intervention (P < 0.01). 5-HT content increased in the salidroside-treated group (P < 0.01). Compared with the model group after intervention, the tic behavior score was significantly reduced (P < 0.01), and DA levels in plasma and striatum were elevated (P < 0.01, P < 0.05) in the salidroside-treated group and the haloperidol-treated group. Compared with the haloperidol-treated group, the tic behavior score increased (P < 0.01), DA levels in plasma and striatum were lowered (P < 0.01, P < 0.05), the 5-HT level increased in plasma and striatum (P < 0.01, P < 0.05) in the salidroside-treated group. CONCLUSIONS: In the salidroside-treated group, the tic behavior was significantly reduced, and DA levels in plasma and striatum were elevated. Its mechanism might be related to regulating activities of dopamine neurons in striatum.

Repression of bone morphogenetic protein 4 by let-7i attenuates mesenchymal migration of head and neck cancer cells.

The movement modes of epithelial cancer cells in three-dimensional (3D) environments include the mesenchymal mode, which is associated with local invasion, and the amoeboid mode, which facilitates distant metastasis. The migratory behavior of individual cancer cells is critical for tumor dissemination; however, the mechanism underlying regulation of the switch between movement modes is not clearly understood. For head and neck squamous cell carcinoma (HNSCC), local invasion is the major route of dissemination. We previously demonstrated that, in HNSCC cells, Twist1 represses let-7i expression to elicit mesenchymal-mode movement through activation of Ras-related C3 botulinum toxin substrate 1 (RAC1). In this study, we discover another important target gene of let-7i for regulating HNSCC migration. Using bioinformatic tools, we identified bone morphogenetic protein 4 (BMP4) as a candidate target of let-7i. Further experiments, including 3'-untranslated region (UTR) reporter assays, quantitative RT-PCR and western blotting, confirmed that BMP4 is a bona fide target repressed by let-7i. In the HNSCC cell line OECM-1, knockdown of BMP4 reduced mesenchymal-mode migration and invasion in 3D culture. In clinical HNSCC samples, let-7i expression was inversely correlated with BMP4 expression. Our results revealed that let-7i attenuates mesenchymal-mode migration of HNSCC cells through repression of a novel target, BMP4.

An undefined cystatin CsCPI1 from tea plant Camellia sinensis harbors antithrombotic activity.

Tea consumption has been linked to a decreased risk of cardiovascular disease (CVD) mortality, which imposes a heavy burden on the healthcare system; however, which components in tea cause this beneficial effect is not fully understood. Here we uncovered a cystatin (namely CsCPI1), which is a cysteine proteinase inhibitor (CPI) of the tea plant (Camellia sinensis) that promotes antithrombotic activity. Since thrombosis is a common pathogenesis of fatal CVDs, we investigated the effects of CsCPI1, which showed good therapeutic effects in mouse models of thrombotic disease and ischemic stroke. CsCPI1 significantly increases endothelial cell production of nitric oxide (NO) and inhibits platelet aggregation. Notably, CsCPI1 exhibited no cytotoxicity or resistance to pH and temperature changes, which indicates that CsCPI1 might be a potent antithrombotic agent that contributes to the therapeutic effects of tea consumption against CVD. Specifically, the antithrombotic effects of CsCPI1 are distinct from the classical function of plant cystatins against herbivorous insects. Therefore, our study proposes a new potential role of cystatins in CVD prevention and treatment, which requires further study.

T-cell exhaustion and stemness in antitumor immunity: Characteristics, mechanisms, and implications.

T cells play a crucial role in the regulation of immune response and are integral to the efficacy of cancer immunotherapy. Because immunotherapy has emerged as a promising treatment for cancer, increasing attention has been focused on the differentiation and function of T cells in immune response. In this review, we describe the research progress on T-cell exhaustion and stemness in the field of cancer immunotherapy and summarize advances in potential strategies to intervene and treat chronic infection and cancer by reversing T-cell exhaustion and maintaining and increasing T-cell stemness. Moreover, we discuss therapeutic strategies to overcome T-cell immunodeficiency in the tumor microenvironment and promote continuous breakthroughs in the anticancer activity of T cells.

Immunogenic cell death in cancer immunotherapy.

Cancer immunotherapy has been acknowledged as a new paradigm for cancer treatment, with notable therapeutic effects on certain cancer types. Despite their significant potential, clinical studies over the past decade have revealed that cancer immunotherapy has low response rates in the majority of solid tumors. One of the key causes for poor responses is known to be the relatively low immunogenicity of solid tumors. Because most solid tumors are immune desert 'cold tumors' with antitumor immunity blocked from the onset of innate immunity, combination therapies that combine validated T-based therapies with approaches that can increase tumor-immunogenicity are being considered as relevant therapeutic options. This review paper focuses on immunogenic cell death (ICD) as a way of enhancing immunogenicity in tumor tissues. We will thoroughly review how ICDs such as necroptosis, pyroptosis, and ferroptosis can improve anti-tumor immunity and outline clinical trials targeting ICD. Finally, we will discuss the potential of ICD inducers. as an adjuvant for cancer immunotherapy.[BMB Reports 2023; 56(5): 275-286].

Mechanisms regulating PD-L1 expression in cancers and associated opportunities for novel small-molecule therapeutics.

Antagonistic antibodies targeting the inhibitory immune-checkpoint receptor PD-1 or its ligand PD-L1 are used to treat a wide range of cancer types and can substantially improve patient survival. Nevertheless, strategies to overcome intrinsic and acquired resistance are required to respectively increase response rates and durations. PD-L1 is often upregulated in various malignancies, and emerging evidence suggests numerous underlying mechanisms involving distinct oncogenic signalling pathways. Thus, specific small-molecule inhibitors have the potential to simultaneously suppress not only a key oncogenic signalling pathway but also PD-L1 expression and/or activity in particular cancers, thereby presenting attractive candidate drugs for combination with existing immune-checkpoint inhibitors and/or other targeted agents. Herein, we summarize advances in understanding the mechanisms regulating PD-L1 expression at the transcriptional, post-transcriptional, translational and post-translational levels in cancers. We describe the roles of the diverse post-translational modifications of PD-L1, including phosphorylation, palmitoylation, glycosylation, acetylation and ubiquitination. Moreover, we discuss the potential use of small-molecule agents to modulate these mechanisms as well as of predictive biomarkers to stratify patients for optimal treatment, and provide our perspective on potential therapeutic strategies to circumvent resistance to conventional anti-PD-1/PD-L1 antibodies.

Macrophages Are a Double-Edged Sword: Molecular Crosstalk between Tumor-Associated Macrophages and Cancer Stem Cells.

Cancer stem cells (CSCs) are a subset of highly tumorigenic cells in tumors. They have enhanced self-renewal properties, are usually chemo-radioresistant, and can promote tumor recurrence and metastasis. They can recruit macrophages into the tumor microenvironment and differentiate them into tumor-associated macrophages (TAMs). TAMs maintain CSC stemness and construct niches that are favorable for CSC survival. However, how CSCs and TAMs interact is not completely understood. An understanding on these mechanisms can provide additional targeting strategies for eliminating CSCs. In this review, we comprehensively summarize the reported mechanisms of crosstalk between CSCs and TAMs and update the related signaling pathways involved in tumor progression. In addition, we discuss potential therapies targeting CSC-TAM interaction, including targeting macrophage recruitment and polarization by CSCs and inhibiting the TAM-induced promotion of CSC stemness. This review also provides the perspective on the major challenge for developing potential therapeutic strategies to overcome CSC-TAM crosstalk.

Alanine-Glyoxylate Aminotransferase Sustains Cancer Stemness Properties through the Upregulation of SOX2 and OCT4 in Hepatocellular Carcinoma Cells.

Liver cancer stem cells (LCSCs) are a small subset of oncogenic cells with a self-renewal ability and drug resistance, and they promote the recurrence and metastasis of hepatocellular carcinoma (HCC). However, the mechanisms regulating LCSCs have not been fully explored. By enriching LCSCs from spheroid cultures and performing transcriptomic analysis, we determined that alanine-glyoxylate aminotransferase (AGXT), which participates in the metabolism of serine and glycine, was significantly upregulated in spheroid cultures, and its function in LCSCs remains unknown. Through the exogenous overexpression or short hairpin RNA knockdown of AGXT in HCC cells, we observed that changes in the AGXT level did not affect the spheroid ability and population of LCSCs. The knockdown of AGXT in LCSCs reduced the number of spheroids and the population of LCSCs; this implies that AGXT is required for the maintenance of cancer stemness rather than as a driver of LCSCs. Mechanistically, AGXT may sustain the self-renewal potential of LCSCs by upregulating the expression of SRY-box transcription factor 2 (SOX2) and octamer-binding transcription factor 4 (OCT4), two well-known master regulators of cancer stemness. Taken together, our study demonstrates the role of AGXT in supporting LCSCs; thus, AGXT merits further exploration.