Targeting aerobic glycolysis and HIF-1alpha expression enhance imiquimod-induced apoptosis in cancer cells

Design, synthesis, and evaluation of antitumor activity in Pseudolaric acid B Azole derivatives: Novel and potent angiogenesis inhibitor via regulation of the PI3K/AKT and MAPK mediated HIF-1/VEGF signaling pathway

Tumor proliferation and metastasis are intricately linked to blood vessel formation, with vascular endothelial growth factor (VEGF) playing a pivotal role in orchestrating angiogenesis throughout tumor progression. Pseudolaric acid B (PAB) has emerged as a potent inhibitor of tumor cell proliferation, migration, and angiogenesis. In efforts to enhance its efficacy, 37 derivatives of PAB were synthesized and assessed for their capacity to suppress VEGF secretion in SiHa cells under hypoxic conditions. Notably, majority of these derivatives exhibited significant inhibition of VEGF protein secretion without inducing cytotoxicity. Among them, compound M2 displayed the most potent inhibitory activity, with an IC50 value of 0.68 μM, outperforming the lead compound PAB (IC50 = 5.44 μM). Compound M2 not only curbed the migration and angiogenesis of HUVECs under hypoxic conditions but also hindered the invasion of SiHa cells. Mechanistic investigations unveiled that compound M2 may impede the accumulation and nuclear translocation of hypoxia-inducible factor 1α (HIF-1α) in SiHa cells, thereby downregulating VEGF expression. This inhibitory effect on HIF-1α was corroborated by experiments utilizing the protease inhibitor MG-132 and protein synthesis inhibitor CHX, indicating that compound M2 diminishes HIF-1α levels by reducing its synthesis. Furthermore, compound M2 was observed to modulate the PI3K/AKT/mTOR and MAPK signaling pathways in tumor cells, thereby regulating HIF-1α translation and synthesis. In vivo studies demonstrated that compound M2 exhibited low toxicity and effectively curbed tumor growth. Immunohistochemistry analyses validated that compound M2 effectively suppressed the expression of HIF-1α and VEGF in tumor tissues, underscoring its potential as a promising therapeutic agent for targeting tumor angiogenesis.

The Protective Effects of Mcl-1 on Mitochondrial Damage and Oxidative Stress in Imiquimod-Induced Cancer Cell Death

Mitochondria, vital organelles that generate ATP, determine cell fate. Dysfunctional and damaged mitochondria are fragmented and removed through mitophagy, a mitochondrial quality control mechanism. The FDA-approved drug IMQ, a synthetic agonist of Toll-like receptor 7, exhibits antitumor activity against various skin malignancies. We previously reported that IMQ promptly reduced the level of the antiapoptotic Mcl-1 protein and that Mcl-1 overexpression attenuated IMQ-triggered apoptosis in skin cancer cells. Furthermore, IMQ profoundly disrupted mitochondrial function, promoted mitochondrial fragmentation, induced mitophagy, and caused cell death by generating high levels of ROS. However, whether Mcl-1 protects mitochondria from IMQ treatment is still unknown. In this study, we demonstrated that Mcl-1 overexpression induced resistance to IMQ-induced apoptosis and reduced both IMQ-induced ROS generation and oxidative stress in cancer cells. Mcl-1 overexpression maintained mitochondrial function and integrity and prevented mitophagy in IMQ-treated cancer cells. Furthermore, IL-6 protected against IMQ-induced apoptosis by increasing Mcl-1 expression and attenuating IMQ-induced mitochondrial fragmentation. Mcl-1 overexpression ameliorates IMQ-induced ROS generation and mitochondrial fragmentation, thereby increasing mitochondrial stability and ultimately attenuating IMQ-induced cell death. Investigating the roles of Mcl-1 in mitochondria is a potential strategy for cancer therapy development.

Effect of stearyl alcohol on imiquimod-induced psoriasis-like skin inflammation in mice

Psoriasis is a chronic inflammatory skin disease. Topical medicines are the preferred treatment for mild to moderate psoriasis, but the effect of excipients used in semi-solid preparations on psoriasis-like skin inflammation is not fully understood. In the present study, we investigated the effect of stearyl alcohol, a commonly used excipient, on imiquimod (IMQ)-induced psoriasis-like skin inflammation in mice. Psoriasis-like skin inflammation was induced by topical IMQ treatment on the back of mice. Skin lesion severity was evaluated by using psoriasis area and severity index (PASI) scores. The skin sections were stained by haematoxylin-eosin and immunohistochemistry. Stearyl alcohol (20% in vaseline) treatment significantly reduced the IMQ-induced increase of PASI scores and epidermal thickness in mice. IMQ treatment increased the number of Ki67- and proliferating cell nuclear antigen (PCNA)-positive cells in the skin, and the increases were inhibited by stearyl alcohol (20% in vaseline) treatment. Stearyl alcohol treatment (1%, 5%, 10% in vaseline) dose-dependently ameliorated IMQ-induced increase of PASI scores and epidermal thickness in mice. Hexadecanol (20% in vaseline), stearic acid (20% in vaseline) and vaseline treatment had no significant effect on IMQ-induced psoriasis-like skin inflammation in mice. In conclusion, stearyl alcohol has the effect of improving IMQ-induced psoriasis-like skin inflammation in mice.

Inhibiting neddylation with MLN4924 potentiates hypoxia-induced apoptosis of mouse type B spermatogonia GC-2 cells

Hypoxia, an inadequate supply of tissue oxygen tension, has been reported to induce apoptosis of spermatogenic cells and is associated with male infertility. Neddylation, a post-translational modification similar to ubiquitination, has been shown to be involved in the hypoxia stress response. However, the functions of neddylation in hypoxia-induced apoptosis of spermatogenic cells and its association with male infertility remain largely unexplored. In this study, aiming to explore the role of neddylation in male infertility, we used the specific neddylation inhibitor MLN4924 for treatment in mouse type B spermatogonia GC-2 cells. Our results showed that MLN4924 had no apparent effect on GC-2 cell apoptosis under normoxia, but significantly increased apoptotic cells under hypoxia. Transcriptomic analysis and qPCR assay confirmed that MLN4924 could suppress the expression of hypoxia target genes in GC-2 cells under hypoxia. In addition, MLN4924 could enhance the induction of intracellular and mitochondrial reactive oxygen species (ROS) under hypoxia. These results indicate that the neddylation inhibitor MLN4924 potentiates hypoxia-induced apoptosis of mouse type B spermatogonia GC-2 cells, and neddylation may play an important role in promoting spermatogenic cells to adapt to hypoxia stress.

Low-dose imiquimod induces melanogenesis in melanoma cells through an ROS-mediated pathway

BACKGROUND

Melanogenesis is the process of melanin maturation which not only protects skin from UV radiation but also plays an important role in antigenicity of melanomas. Imiquimod (IMQ) is a toll-like receptor 7 (TLR7) agonist that exhibits antiviral and anticancer activity.

OBJECTIVE

To explore whether IMQ could induce melanogenesis in melanoma cells.

METHODS

The mouse melanoma cell line B16F10, the mouse immortalized melanocyte Melan-A, and human melanoma cell lines MNT-1, C32 and A375 were utilized in this study. The pigmented level was observed by the centrifuged cell pellet. The intracellular and extracellular melanin levels were examined in the absorbance in NaOH-extracted cell lysate and cell-cultured medium, respectively. The expression of melanogenesis related proteins was examined by immunoblotting. The intracellular cyclic AMP amount was evaluated by the cAMP Glo assay kit. The activity of phosphodiesterase 4B (PDE4B) was investigated by CREB reporter assay with overexpressed PDE4B or not.

RESULTS

We demonstrated that a low dose of IMQ could trigger melanogenesis in B16F10 cells. IMQ induced microphthalmia-associated transcription factor (MITF) nuclear translocation, upregulated the expression of melanogenesis-related proteins, increased tyrosinase (TYR) activity, and led to pigmentation in B16F10 cells. Next, we found that IMQ-induced melanogenesis was activated by excessive intracellular cAMP accumulation, which was regulated through IMQ-mediated PDE4B inhibition. Finally, IMQ-induced ROS production was found to be involved in melanogenesis by its control of PDE4B activity.

CONCLUSIONS

Low dose of IMQ could activate melanogenesis through the ROS/PDE4B/PKA pathway in melanoma cells.

Role of bone marrow adipocytes in bone metastasis development and progression: a systematic review

Purpose

Bone marrow adipocytes (BMAs) are the most plentiful cells in the bone marrow and function as an endocrine organ by producing fatty acids, cytokines, and adipokines. Consequently, BMAs can interact with tumor cells, influencing both tumor growth and the onset and progression of bone metastasis. This review aims to systematically evaluate the role of BMAs in the development and progression of bone metastasis.

Methods

A comprehensive search was conducted on PubMed, Web of Science, and Scopus electronic databases, following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement standards, to identify studies published from March 2013 to June 2023. Two independent reviewers assessed and screened the literature, extracted the data, and evaluated the quality of the studies. The body of evidence was evaluated and graded using the ROBINS-I tool for non-randomized studies of interventions and the Systematic Review Centre for Laboratory Animal Experimentation (SYRCLE) tool for in vivo studies. The results were synthesized using descriptive methods.

Results

The search yielded a total of 463 studies, of which 17 studies were included in the final analysis, including 15 preclinical studies and two non-randomized clinical studies. Analysis of preclinical studies revealed that BMAs play a significant role in bone metastasis, particularly in prostate cancer followed by breast and malignant melanoma cancers. BMAs primarily influence cancer cells by inducing a glycolytic phenotype and releasing or upregulating soluble factors, chemokines, cytokines, adipokines, tumor-derived fatty acid-binding protein (FABP), and members of the nuclear receptor superfamily, such as chemokine (C-C motif) ligand 7 (CCL7), C-X-C Motif Chemokine Ligand (CXCL)1, CXCL2, interleukin (IL)-1β, IL-6, FABP4, and peroxisome proliferator-activated receptor γ (PPARγ). These factors also contribute to adipocyte lipolysis and regulate a pro-inflammatory phenotype in BMAs. However, the number of clinical studies is limited, and definitive conclusions cannot be drawn.

Conclusion

The preclinical studies reviewed indicate that BMAs may play a crucial role in bone metastasis in prostate, breast, and malignant melanoma cancers. Nevertheless, further preclinical and clinical studies are needed to better understand the complex role and relationship between BMAs and cancer cells in the bone microenvironment. Targeting BMAs in combination with standard treatments holds promise as a potential therapeutic strategy for bone metastasis.

Riluzole regulates pancreatic cancer cell metabolism by suppressing the Wnt-β-catenin pathway

Most cancer cells rely on aerobic glycolysis to support uncontrolled proliferation and evade apoptosis. However, pancreatic cancer cells switch to glutamine metabolism to survive under hypoxic conditions. Activation of the Wnt/β-catenin pathway induces aerobic glycolysis by activating enzymes required for glucose metabolism and regulating the expression of glutamate transporter and glutamine synthetase. The results demonstrate that riluzole inhibits pancreatic cancer cell growth and has no effect on human pancreatic normal ductal epithelial cells. RNA-seq experiments identified the involvement of Wnt and metabolic pathways by riluzole. Inhibition of Wnt-β-catenin/TCF-LEF pathway by riluzole suppresses the expression of PDK, MCT1, cMyc, AXIN, and CyclinD1. Riluzole inhibits glucose transporter 2 expression, glucose uptake, lactate dehydrogenase A expression, and NAD + level. Furthermore, riluzole inhibits glutamate release and glutathione levels, and elevates reactive oxygen species. Riluzole disrupts mitochondrial homeostasis by inhibiting Bcl-2 and upregulating Bax expression, resulting in a drop of mitochondrial membrane potential. Finally, riluzole inhibits pancreatic cancer growth in KPC (Pdx1-Cre, LSL-Trp53R172H, and LSL-KrasG12D) mice. In conclusion, riluzole can inhibit pancreatic cancer growth by regulating glucose and glutamine metabolisms and can be used to treat pancreatic cancer.

Recent advances in cancer immunotherapy: Modulation of tumor microenvironment by Toll-like receptor ligands

Immunotherapy is considered a promising approach for cancer treatment. An important strategy for cancer immunotherapy is the use of cancer vaccines, which have been widely used for cancer treatment. Despite the great potential of cancer vaccines for cancer treatment, their therapeutic effects in clinical settings have been limited. The main reason behind the lack of significant therapeutic outcomes for cancer vaccines is believed to be the immunosuppressive tumor microenvironment (TME). The TME counteracts the therapeutic effects of immunotherapy and provides a favorable environment for tumor growth and progression. Therefore, overcoming the immunosuppressive TME can potentially augment the therapeutic effects of cancer immunotherapy in general and therapeutic cancer vaccines in particular. Among the strategies developed for overcoming immunosuppression in TME, the use of toll-like receptor (TLR) agonists has been suggested as a promising approach to reverse immunosuppression. In this paper, we will review the application of the four most widely studied TLR agonists including agonists of TLR3, 4, 7, and 9 in cancer immunotherapy.

Early redox homeostasis disruption contributes to the differential cytotoxicity of imiquimod on transformed and normal endothelial cells

The off-label use of imiquimod (IQ) for hemangioma treatment has shown clinical benefits. We have previously reported a selective direct IQ-cytotoxic effect on transformed (H5V) vs. normal (1G11) endothelial cells (EC). In the present study, we investigated the mechanism underlying this selective cytotoxicity in terms of TLR7/8 receptor expression, NF-κB signalling and time-dependent modifications of oxidative stress parameters (ROS: reactive oxygen species, catalase and superoxide dismutase activities, GSH/GSSG and lipid peroxidation). TLR7/8 level was extremely low in both cell lines, and IQ did not upregulate TLR7/8 expression or activate NF-κB signalling. IQ significantly induced ROS in H5V after 2 h and strongly affected antioxidant defenses. After 12 h, enzyme activities were restored to baseline levels but a robust drop in GSH/GSSG persisted together with increased lipid peroxidation levels and a marked mitochondrial dysfunction. Although in normal IQ-treated EC some oxidative stress parameters were affected after 4 h, mitochondrial health and GSH/GSSG ratio remained notably unaffected after 12 h. Therefore, the early alterations (0-2 h) in transformed EC breached redox homeostasis as strongly as to enhance their susceptibility to IQ. This interesting facet of IQ as redox disruptor could broaden its therapeutic potential for other skin malignancies, alone or in adjuvant schemes.

Recent advances in heat shock proteins in cancer diagnosis, prognosis, metabolism and treatment

Heat shock proteins (HSPs) are a group of proteins, also known as molecular chaperones, which participate in protein folding and maturation in response to stresses or high temperature. According to their molecular weights, mammalian HSPs are classified into HSP27, HSP40, HSP60, HSP70, HSP90, and large HSPs. Previous studies have revealed that HSPs play important roles in oncogenesis and malignant progression because they can modulate all six hallmark traits of cancer. Because of this, HSPs have been propelled into the spotlight as biomarkers for cancer diagnosis and prognosis, as well as an exciting anticancer drug target. However, the relationship between the expression level of HSPs and their activity and cancer diagnosis, prognosis, metabolism and treatment is not clear and has not been completely established. Herein, this review summarizes and discusses recent advances and perspectives in major HSPs as biomarkers for cancer diagnosis, as regulators for cancer metabolism or as therapeutic targets for cancer therapy, which may provide new directions to improve the accuracy of cancer diagnosis and develop more effective and safer anticancer therapeutics.

Imiquimod Accelerated Antitumor Response by Targeting Lysosome Adaptation in Skin Cancer Cells

Lysosomal adaptation is a cellular physiological process in which the number and function of lysosomes are regulated at the transcriptional and post-transcriptional levels in response to extracellular and/or intracellular cues or lysosomal damage. Imiquimod (IMQ), a synthetic toll-like receptor 7 ligand with hydrophobic and weak basic properties, exhibits both antitumor and antiviral activity against various skin malignancies as a clinical treatment. Interestingly, IMQ has been suggested to be highly concentrated in the lysosomes of plasmacytoid dendritic cells, indicating that IMQ could modulate lysosome function after sequestration in the lysosome. In this study, we found that IMQ not only induced lysosomal membrane permeabilization and dysfunction but also increased lysosome biogenesis to achieve lysosomal adaptation in cancer cells. IMQ-induced ROS production but not lysosomal sequestration of IMQ was the major cause of lysosomal adaptation. Moreover, IMQ-induced lysosomal adaptation occurred through lysosomal calcium ion release and activation of the calcineurin/TFEB axis to promote lysosome biogenesis. Finally, depletion of TFEB sensitized skin cancer cells to IMQ-induced apoptosis in vitro and in vivo. In summary, a disruption of lysosomal adaptation might represent a therapeutic strategy for synergistically enhancing the cytotoxicity of IMQ in skin cancer cells.

Inhibitors of HSP90 in melanoma

HSP90 (heat shock protein 90) is an ATP-dependent molecular chaperone involved in a proper folding and maturation of hundreds of proteins. HSP90 is abundantly expressed in cancer, including melanoma. HSP90 client proteins are the key oncoproteins of several signaling pathways controlling melanoma development, progression and response to therapy. A number of natural and synthetic compounds of different chemical structures and binding sites within HSP90 have been identified as selective HSP90 inhibitors. The majority of HSP90-targeting agents affect N-terminal ATPase activity of HSP90. In contrast to N-terminal inhibitors, agents interacting with the middle and C-terminal domains of HSP90 do not induce HSP70-dependent cytoprotective response. Several inhibitors of HSP90 were tested against melanoma in pre-clinical studies and clinical trials, providing evidence that these agents can be considered either as single or complementary therapeutic strategy. This review summarizes current knowledge on the role of HSP90 protein in cancer with focus on melanoma, and provides an overview of structurally different HSP90 inhibitors that are considered as potential therapeutics for melanoma treatment.

Molecular Chaperones: Molecular Assembly Line Brings Metabolism and Immunity in Shape

Molecular chaperones are a set of conserved proteins that have evolved to assist the folding of many newly synthesized proteins by preventing their misfolding under conditions such as elevated temperatures, hypoxia, acidosis and nutrient deprivation. Molecular chaperones belong to the heat shock protein (HSP) family. They have been identified as important participants in immune functions including antigen presentation, immunostimulation and immunomodulation, and play crucial roles in metabolic rewiring and epigenetic circuits. Growing evidence has accumulated to indicate that metabolic pathways and their metabolites influence the function of immune cells and can alter transcriptional activity through epigenetic modification of (de)methylation and (de)acetylation. However, whether molecular chaperones can regulate metabolic programs to influence immune activity is still largely unclear. In this review, we discuss the available data on the biological function of molecular chaperones to immune responses during inflammation, with a specific focus on the interplay between molecular chaperones and metabolic pathways that drive immune cell fate and function.

Circle RNA circABCB10 Modulates PFN2 to Promote Breast Cancer Progression, as Well as Aggravate Radioresistance Through Facilitating Glycolytic Metabolism Via miR-223-3p

Background: Breast cancer (BC) is a common tumor in women worldwide, and irradiation (IR) resistance is a major obstacle for BC therapy. Circle RNAs (circRNAs) were identified as implicated in the progression of cancer and IR resistance. However, the role of circABCB10 in BC progression and IR resistance is not well defined. Materials and Methods: The levels of circABCB10, miR-223-3p, and profilin-2 (PFN2) were detected by quantitative real-time polymerase chain reaction. The cell viability and survival rate were monitored by MTT assay. The glucose consumption, lactic acid production, LDH-A activity, and ATP production were evaluated to measure glycolysis. The protein levels of hypoxia inducible factor-1α (HIF-1α), hexokinase 2 (HK2), lactate dehydrogenase A chain (LDH-A), and PFN2 were estimated by Western blot assay. The colony formation rate was tested by colony formation assay. Dual-luciferase reporter assay was constructed to validate the interaction between miR-223-3p and circABCB10 or PFN2. The mice xenograft assay was performed to further verify the effects of circABCB10 on BC progression in vivo. Results: CircABCB10 and PFN2 were elevated, while miR-223-3p was reduced in BC tissues and cells. CircABCB10 sponged miR-223-3p, and PFN2 was a target of miR-223-3p in BC cells. CircABCB10 silencing inhibited cell proliferation, glycolysis, colony formation, and decreased IR resistance in BC cells by modulating miR-223-3p. Meanwhile, circABCB10 depletion restrained xenograft tumor growth in vivo. Also, miR-223-3p overexpression refrained cell proliferation, glycolysis, and colony formation while improving IR sensitivity in BC cells by regulating PFN2. Besides, circABCB10 knockdown declined PFN2 in BC cells via miR-223-3p. The glycolysis inhibitor 2-deoxy-D-glucose enhanced IR sensitivity in BC cells via circABCB10. Conclusion: CircABCB10 knockdown contributed to irradiation sensitivity by negatively regulating glycolysis via the miR-223-3p/PFN axis in breast cancer.

Salmonella enterica serovar Typhimurium sseK3 induces apoptosis and enhances glycolysis in macrophages

Background

Salmonella enterica serovar Typhimurium (S. Typhimurium) is an important infectious disease pathogen that can survive and replicate in macrophages. Glycolysis is essential for immune responses against S. Typhimurium infection in macrophages, and is also associated with apoptosis. S. Typhimurium secreted effector K3 (SseK3) was recently identified as a novel translated and secreted protein. However, there is no study about the role of sseK3 in the relationship between apoptosis and glycolysis in cells infected with S. Typhimurium. It is unclear whether this protein exerts a significant role in the progress of apoptosis and glycolysis in S. Typhimurium-infected macrophages.

Results

Macrophages were infected with S. Typhimurium SL1344 wild-type (WT), ΔsseK3 mutant or sseK3-complemented strain, and the effects of sseK3 on apoptosis and glycolysis were determined. The adherence and invasion in the ΔsseK3 mutant group were similar to that in the WT and sseK3-complemented groups, indicating that SseK3 was not essential for the adherence and invasion of S. Typhimurium in macrophages. However, the percentage of apoptosis in the ΔsseK3 mutant group was much lower than that in the WT and sseK3-complemented groups. Caspase-3, caspase-8, and caspase-9 enzyme activity in the ΔsseK3 mutant group were significantly lower than in the WT group and sseK3-complemented groups, indicating that sseK3 could improve the caspase-3, caspase-8, and caspase-9 enzyme activity. We also found that there were no significant differences in pyruvic acid levels between the three groups, but the lactic acid level in the ΔsseK3 mutant group was much lower than that in the WT and sseK3-complemented groups. The ATP levels in the ΔsseK3 mutant group were remarkably higher than those in the WT and sseK3-complemented groups. These indicated that the sseK3 enhanced the level of glycolysis in macrophages infected by S. Typhimurium.

Conclusions

S. Typhimurium sseK3 is likely involved in promoting macrophage apoptosis and modulating glycolysis in macrophages. Our results could improve our understanding of the relationship between apoptosis and glycolysis in macrophages induced by S. Typhimurium sseK3.

Imiquimod-induced ROS production disrupts the balance of mitochondrial dynamics and increases mitophagy in skin cancer cells

BACKGROUND

Mitochondrial homeostasis is a highly dynamic process involving continuous fission and fusion cycles and mitophagy to maintain mitochondrial functionality. Imiquimod (IMQ), a Toll-like receptor (TLR) 7 ligand, is used to treat various skin malignancies. IMQ also induces apoptotic and autophagic cell death in various cancers through a TLR7-independent pathway.

OBJECTIVE

To investigate whether IMQ-induced ROS production is involved in mitochondrial dysfunction, mitochondrial fragmentation and mitophagy in skin cancer cells.

METHODS

BCC/KMC-1, B16F10 and A375 skin cancer cells, AGS gastric cancer cells and primary human keratinocytes were treated with 50 μg/mL IMQ. After 4 h, ROS were detected by CM-H₂DCFDA, DHE, and MitoSOX Red staining. After 24 h, cell viability and the mitochondrial membrane potential were evaluated by a CCK-8 assay and JC-1 staining, respectively. Oxygen consumption was assessed with an Oroboros instrument. Mitochondrial morphology and mitophagy were evaluated by MitoTracker and LysoTracker staining. Mitochondrial dynamics markers, including MFN-1, DRP-1 and OPA1, and mitophagy markers, including LC3, S65-phosphorylated ubiquitin, PINK1 and TOM20, were detected by immunoblotting.

RESULTS

IMQ not only induced severe ROS production but also resulted in increased mitochondrial membrane potential loss, mitochondrial fission and mitophagy and decreased oxygen consumption in skin cancer cells compared with normal keratinocytes. Pretreatment with the antioxidant NAC reduced IMQ-induced ROS production and attenuated IMQ-induced mitochondrial fission and mitophagy in skin cancer cells.

CONCLUSIONS

IMQ-induced ROS might be associated with mitochondrial dysfunction, mitochondrial fission and mitophagy in cancer cells. Alleviating IMQ-induced ROS production would reduce mitochondrial fission-to-fusion skewing and further reduce IMQ-induced mitophagy.

The role of microglia in neuroprogressive disorders: mechanisms and possible neurotherapeutic effects of induced ketosis

A comprehensive review of molecular mechanisms involved in the promotion and maintenance of distinct microglia phenotypes is provided. The acquisition and perpetuation of predominantly pro-inflammatory microglial phenotypes have been implicated in the pathophysiology of several neuroprogressive diseases and is associated with reduced ATP production via oxidative phosphorylation, increased ATP generation by glycolysis, elevated oxidative and nitrosative stress and other metabolic, inflammatory and hormonal insults. Microglia can also adopt a predominantly anti-inflammatory phenotypes with neuroprotective properties. Strategies that promote and maintain a predominantly anti-inflammatory phenotype may hold promise as novel therapeutic opportunities for neuroprogressive illness. Induced ketosis may promote a transition towards predominantly anti-inflammatory microglial states/phenotypes by several mechanisms, including inhibition of glycolysis and increased NAD⁺ production; engagement of microglial GPR109A receptors; histone deacetylase inhibition; and elevated n-3 polyunsaturated fatty acids levels. Since microglia activation can now be assessed in vivo, these data provide a clear rationale for the design of transdiagnostic randomized controlled trials of the ketogenic diet and other ketosis-inducing strategies for neuroprogressive diseases, which may also provide mechanistic insights through the assessment of "target engagement".

Imiquimod Exerts Antitumor Effects by Inducing Immunogenic Cell Death and Is Enhanced by the Glycolytic Inhibitor 2-Deoxyglucose

The induction of immunogenic cell death (ICD) in cancer cells triggers specific immune responses against the same cancer cells. Imiquimod (IMQ) is a synthetic ligand of toll-like receptor 7 that exerts antitumor activity by stimulating cell-mediated immunity or by directly inducing apoptosis. Whether IMQ causes tumors to undergo ICD and elicits a specific antitumor immune response is unknown. We demonstrated that IMQ-induced ICD-associated features, including the surface exposure of calreticulin and the secretion of adenosine triphosphate and HMGB1, were mediated by ROS and endoplasmic reticulum stress. In a B16F10 melanoma mouse model, vaccinating mice with IMQ-induced ICD cell lysate or directly injecting IMQ in situ reduced tumor growth that was mediated by inducing tumor-specific T-cell proliferation, promoting tumor-specific cytotoxic killing by CD8⁺ T cells, and increasing the infiltration of various immune cells into tumor lesions. The ICD-associated features were crucial in the induction of specific antitumor immunity in vivo. The glycolytic inhibitor 2-deoxyglucose enhanced IMQ-induced ICD-associated features and strengthened the antitumor immunity mediated by IMQ-induced ICD cell lysate in p53-mutant cancer cells, which were IMQ-resistant in vitro. We conclude that IMQ is an authentic ICD inducer and provide a concept connecting IMQ-induced cancer cell death and antitumor immune responses.

Metabolic profiling of cancer cells reveals genome-wide crosstalk between transcriptional regulators and metabolism

Transcriptional reprogramming of cellular metabolism is a hallmark of cancer. However, systematic approaches to study the role of transcriptional regulators (TRs) in mediating cancer metabolic rewiring are missing. Here, we chart a genome-scale map of TR-metabolite associations in human cells using a combined computational-experimental framework for large-scale metabolic profiling of adherent cell lines. By integrating intracellular metabolic profiles of 54 cancer cell lines with transcriptomic and proteomic data, we unraveled a large space of associations between TRs and metabolic pathways. We found a global regulatory signature coordinating glucose- and one-carbon metabolism, suggesting that regulation of carbon metabolism in cancer may be more diverse and flexible than previously appreciated. Here, we demonstrate how this TR-metabolite map can serve as a resource to predict TRs potentially responsible for metabolic transformation in patient-derived tumor samples, opening new opportunities in understanding disease etiology, selecting therapeutic treatments and in designing modulators of cancer-related TRs.

Aberrant gene expression in cancer coincides with drastic changes in metabolism. Here, the authors combined metabolome, transcriptome and proteome data in 54 cancer cell lines to uncover a genome-scale network of associations between transcriptional regulators and metabolites.

LncRNA UCA1/miR-143 miR-216b/HK2/MAPK signaling pathway is involved in the regulation of endothelial cell proliferation via the modulation of glycolysis in melanoma

Long noncoding RNAs (lncRNAs) and microRNAs (miRNAs/miRs) are noncoding RNAs that function as regulators of tumor suppressors and oncogenes. The aim of the present study was to investigate the potential mechanism associated with the involvement of urothelial cancer associated 1 (UCA1) in melanoma. Reverse transcription-quantitative polymerase chain reaction and western blot analysis were performed in order to determine the expression levels of UCA1, miR-143, miR-216b, and hexokinase 2 (HK2) in the melanoma and control groups, as well as the influence of UCA1, miR-143, and miR-216b on the expression of HK2, and the effect of lactate and UCA1 on the phosphorylation of p38 mitogen-activated protein kinase (p38 MAPK). Bioinformatics algorithm analysis and a luciferase assay were performed in order to predict miRNA targets. In addition, an MTT assay was performed in order to determine the effect of lactate and UCA1 expression on cell proliferation. A total of 39 participants, consisting of 18 patients with melanoma and 21 healthy control subjects, were included in the present study. The present study demonstrated that the expression levels of UCA1 mRNA, and HK2 mRNA and protein were enhanced in patients with melanoma compared with healthy controls; whereas the expression levels of miR-143 and miR-216b mRNA were suppressed in patients with melanoma compared with healthy controls. Furthermore, it was revealed that UCA1 negatively modulated the expression of miR-143 and miR-216b, and that miR-143 and miR-216b directly targeted the HK2 protein by binding to the HK2 3′ untranslated region (UTR). In addition, it was demonstrated that miR-143 and miR-216 suppressed the luciferase activity exhibited by wild-type HK2 3′-UTR. Furthermore, it was revealed that transfection with UCA1 small interfering RNA, and miR-143 and miR-216b mimics markedly suppressed HK2 mRNA and protein expression levels as well as lactate levels in human umbilical vein endothelial cells; however, O2 consumption was revealed to be enhanced post transfection. By contrast, transfection with UCA1 enhanced HK2 mRNA and protein expression levels as well as lactate production; however, O2 consumption was revealed to be suppressed post transfection. Lactate-induced phosphorylation of p38 MAPK was revealed to occur in a concentration-dependent manner, and UCA1 enhanced the phosphorylation level of p38 MAPK via the inhibition of miR-143 and miR-216b expression. Lactate and UCA1 were demonstrated to enhance cell proliferation. In conclusion, the present study demonstrated that the lncRNA UCA1/miR-143 miR-216b/HK2/lactic acid/MAPK axis may be involved in the pathogenesis of melanoma via the modulation of endothelial cells, and thus, lncRNA UCA1 may serve as a potential therapeutic target for melanoma treatment.

cAMP Receptor Protein of Salmonella enterica Serovar Typhimurium Modulate Glycolysis in Macrophages to Induce Cell Apoptosis

We studied the role of glycolysis in the mechanism of cAMP receptor protein-induced macrophage cell death of Salmonella enterica serovar Typhimurium (S. Typhimurium). Cell apoptosis, caspase-3, -8, -9 enzyme activity, and pyruvic acid, lactic acid, ATP, and hexokinase (HK) contents were determined after infection of macrophages with S. Typhimurium SL1344 wild-type and a cAMP receptor protein mutant strain. While cell apoptosis, caspase-3, -8, -9 enzyme activity, lactic acid, hexokinase, and ATP levels significantly changed by infection with crp mutants compared to the wild-type strain (P < 0.05). Our data suggest that the cAMP receptor protein of S. Typhimurium can modulate macrophage death by effecting glycolysis levels. This finding may help to elucidate the mechanisms of S. Typhimurium pathogenesis.

Toll-like receptors in immunity and inflammatory diseases: Past, present, and future

The immune system is a very diverse system of the host that evolved during evolution to cope with various pathogens present in the vicinity of environmental surroundings inhabited by multicellular organisms ranging from achordates to chordates (including humans). For example, cells of immune system express various pattern recognition receptors (PRRs) that detect danger via recognizing specific pathogen-associated molecular patterns (PAMPs) and mount a specific immune response. Toll-like receptors (TLRs) are one of these PRRs expressed by various immune cells. However, they were first discovered in the Drosophila melanogaster (common fruit fly) as genes/proteins important in embryonic development and dorso-ventral body patterning/polarity. Till date, 13 different types of TLRs (TLR1-TLR13) have been discovered and described in mammals since the first discovery of TLR4 in humans in late 1997. This discovery of TLR4 in humans revolutionized the field of innate immunity and thus the immunology and host-pathogen interaction. Since then TLRs are found to be expressed on various immune cells and have been targeted for therapeutic drug development for various infectious and inflammatory diseases including cancer. Even, Single nucleotide polymorphisms (SNPs) among various TLR genes have been identified among the different human population and their association with susceptibility/resistance to certain infections and other inflammatory diseases. Thus, in the present review the current and future importance of TLRs in immunity, their pattern of expression among various immune cells along with TLR based therapeutic approach is reviewed.

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TLRs are first described PRRs that revolutionized the biology of host-pathogen interaction and immune response

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The discovery of different TLRs in humans proved milestone in the field of innate immunity and inflammation

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The pattern of expression of all the TLRs expressed by human immune cells

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An association of various TLR SNPs with different inflammatory diseases

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Currently available drugs or vaccines based on TLRs and their future in drug targeting along with the role in reproduction, and regeneration

Transcriptome and proteome profiling reveals stress-induced expression signatures of imiquimod-treated Tasmanian devil facial tumor disease (DFTD) cells

As a topical cancer immunotherapy, the toll-like receptor 7 ligand imiquimod activates tumor regression via stimulation of immune cell infiltration and cytotoxic responses. Imiquimod also exerts direct pro-apoptotic effects on tumor cells in vitro, but a role for these effects in imiquimod-induced tumor regression remains undefined. We previously demonstrated that cell lines derived from devil facial tumor disease (DFTD), a transmissible cancer threatening the survival of the Tasmanian devil (Sarcophilus harrisii), are sensitive to imiquimod-induced apoptosis. In this study, the pro-apoptotic effects of imiquimod in DFTD have been investigated using RNA-sequencing and label-free quantitative proteomics. This analysis revealed that changes to gene and protein expression in imiquimod treated DFTD cells are consistent with the onset of oxidative and endoplasmic reticulum stress responses, and subsequent activation of the unfolded protein response, autophagy, cell cycle arrest and apoptosis. Imiquimod also regulates the expression of oncogenic pathways, providing a direct mechanism by which this drug may increase tumor susceptibility to immune cytotoxicity in vivo. Our study has provided the first global analysis of imiquimod-induced effects in any tumor cell line. These findings have highlighted the potential of cell stress pathways as therapeutic targets in DFTD, and will allow for improved mechanistic use of imiquimod as a therapy in both the Tasmanian devil and human cancers.

Bone marrow adipocytes promote the Warburg phenotype in metastatic prostate tumors via HIF-1α activation

Metabolic adaptation is increasingly recognized as a key factor in tumor progression, yet its involvement in metastatic bone disease is not understood. Bone is as an adipocyte-rich organ, and a major site of metastasis from prostate cancer. Bone marrow adipocytes are metabolically active cells capable of shaping tumor metabolism via lipolysis and lipid transfer. In this study, using in vitro and in vivo models of marrow adiposity, we demonstrate that marrow fat cells promote Warburg phenotype in metastatic prostate cancer cells. We show increased expression of glycolytic enzymes, increased lactate production, and decreased mitochondrial oxidative phosphorylation in tumor cells exposed to adipocytes that require paracrine signaling between the two cell types. We also reveal that prostate cancer cells are capable of inducing adipocyte lipolysis as a postulated mechanism of sustenance. We provide evidence that adipocytes drive metabolic reprogramming of tumor cells via oxygen-independent mechanism of HIF-1α activation that can be reversed by HIF-1α downregulation. Importantly, we also demonstrate that the observed metabolic signature in tumor cells exposed to adipocytes mimics the expression patterns seen in patients with metastatic disease. Together, our data provide evidence for a functional relationship between marrow adipocytes and tumor cells in bone that has likely implications for tumor growth and survival within the metastatic niche.

MiR-448 promotes glycolytic metabolism of gastric cancer by downregulating KDM2B

MicroRNAs are critical in various human cancers, including gastric cancer (GC). However, the mechanism underlying the GC development remains elusive. In this study, we demonstrate that miR-448 is increased in GC samples and cell lines. Overexpression of miR-448 facilitated the proliferation of GC cells by stimulating glycolysis. Mechanistically, we identified KDM2B, a reader for methylated CpGs, as the target of miR-448 that represses glycolysis and promotes oxidative phosphorylation. Overexpression of miR-448 reduced both the mRNA and protein levels of KDM2B, whereas KDM2B re-expression abrogated the miR-448-mediated glycolytic activities. Furthermore, we discovered Myc as a key target of KDM2B that controls metabolic switch in GC. Importantly, a cohort of 81 GC tissues revealed that miR-448 level closely associated with a battery of glycolytic genes, in which KDM2B showed the strongest anti-correlation coefficient. In addition, enhanced miR-448 level was significantly associated with poor clinical outcomes of GC patients. Hence, we identified a previously unappreciated mechanism by which miR-448 orchestrate epigenetic, transcriptional and metabolic networks to promote GC progression, suggesting the possibility of therapeutic intervention against cancer metabolic pathways.

microRNA-33a-5p increases radiosensitivity by inhibiting glycolysis in melanoma

Glycolysis was reported to have a positive correlation with radioresistance. Our previous study found that the miR-33a functioned as a tumor suppressor in malignant melanoma by targeting hypoxia-inducible factor1-alpha (HIF-1α), a gene known to promote glycolysis. However, the role of miR-33a-5p in radiosensitivity remains to be elucidated. We found that miR-33a-5p was downregulated in melanoma tissues and cells. Cell proliferation was downregulated after overexpression of miR-33a-5p in WM451 cells, accompanied by a decreased level of glycolysis. In contrast, cell proliferation was upregulated after inhibition of miR-33a-5p in WM35 cells, accompanied by increased glycolysis. Overexpression of miR-33a-5p enhanced the sensitivity of melanoma cells to X-radiation by MTT assay, while downregulation of miR-33a-5p had the opposite effects. Finally, in vivo experiments with xenografts in nude mice confirmed that high expression of miR-33a-5p in tumor cells increased radiosensitivity via inhibiting glycolysis. In conclusions, miR-33a-5p promotes radiosensitivity by negatively regulating glycolysis in melanoma.

Energy metabolism in skin cancers: A therapeutic perspective

Skin cancers are the most common cancers worldwide. The incidence of common skin cancers, including basal cell carcinomas (BCCs), squamous cell carcinomas (SCCs) and melanomas, continues to rise by 5 to 7% per year, mainly due to ultraviolet (UV) exposure and partly because of aging. This suggests an urgent necessity to improve the level of prevention and protection for skin cancers as well as developing new prognostic and diagnostic markers of skin cancers. Moreover, despite innovative therapies especially in the fields of melanoma and carcinomas, new therapeutic options are needed to bypass resistance to targeted therapies or treatment's side effects. Since reprogramming of cellular metabolism is now considered as a hallmark of cancer, some of the recent findings on the role of energy metabolism in skin cancer initiation and progression as well as its effect on the response to targeted therapies are discussed in this review. This article is part of a Special Issue entitled Mitochondria in cancer, edited by Giuseppe Gasparre, Rodrigue Rossignol and Pierre Sonveaux.

The Immunomodulatory Small Molecule Imiquimod Induces Apoptosis in Devil Facial Tumour Cell Lines

The survival of the Tasmanian devil (Sarcophilus harrisii) is threatened by devil facial tumour disease (DFTD). This transmissible cancer is usually fatal, and no successful treatments have been developed. In human studies, the small immunomodulatory molecule imiquimod is a successful immunotherapy, activating anti-tumour immunity via stimulation of toll-like receptor-7 (TLR7) signaling pathways. In addition, imiquimod is a potent inducer of apoptosis in human tumour cell lines via TLR7 independent mechanisms. Here we investigate the potential of imiquimod as a DFTD therapy through analysis of treated DFTD cell lines and Tasmanian devil fibroblasts. WST-8 proliferation assays and annexin V apoptosis assays were performed to monitor apoptosis, and changes to the expression of pro- and anti-apoptotic genes were analysed using qRT-PCR. Our results show that DFTD cell lines, but not Tasmanian devil fibroblasts, are sensitive to imiquimod-induced apoptosis in a time and concentration dependent manner. Induction of apoptosis was accompanied by down-regulation of the anti-apoptotic BCL2 and BCLX_L genes, and up-regulation of the pro-apoptotic BIM gene. Continuous imiquimod treatment was required for these effects to occur. These results demonstrate that imiquimod can deregulate DFTD cell growth and survival in direct and targeted manner. In vivo, this may increase DFTD vulnerability to imiquimod-induced TLR7-mediated immune responses. Our findings have improved the current knowledge of imiquimod action in tumour cells for application to both DFTD and human cancer therapy.

Advances in the targeting of HIF-1α and future therapeutic strategies for glioblastoma multiforme (Review)

Cell metabolism can be reprogrammed by tissue hypoxia leading to cell transformation and glioblastoma multiforme (GBM) progression. In response to hypoxia, GBM cells are able to express a transcription factor called hypoxia inducible factor-1 (HIF-1). HIF-1 belongs to a family of heterodimeric proteins that includes HIF-1α and HIF-1β subunits. HIF-1α has been reported to play a pivotal role in GBM development and progression. In the present review, we discuss the role of HIF-1α in glucose uptake, cancer proliferation, cell mobility and chemoresistance in GBM. Evidence from previous studies indicates that HIF-1α regulates angiogenesis, metabolic and transcriptional signaling pathways. Examples of such are the EGFR, PI3K/Akt and MAPK/ERK pathways. It affects cell migration and invasion by regulating glucose metabolism and growth in GBM cells. The present review focuses on the strategies through which to target HIF-1α and the related downstream genes highlighting their regulatory roles in angiogenesis, apoptosis, migration and glucose metabolism for the development of future GBM therapeutics. Combined treatment with inhibitors of HIF-1α and glycolysis may enhance antitumor effects in clinical settings.

A PPARδ-selective antagonist ameliorates IMQ-induced psoriasis-like inflammation in mice

PPARδ is highly expressed in skin, especially keratinocytes, and its expression is increased in psoriatic lesions. However, the potential role of PPARδ in the pathogenesis of psoriasis remains undefined. Mice treated with Imiquimod (IMQ) to induce psoriasis can be used to evaluate the pathogenesis of psoriasis, and this model has become one of the most important in vivo research tools for research on the disease. In the current study, we showed that PPARδ was highly expressed in the skin of IMQ-induced psoriasis mice. To further understand the impact of PPARδ in psoriasis, we used these mice in a series of experiments to evaluate the pathogenesis of psoriasis. We found that PPARδ was highly expressed in both psoriatic lesions and normal skin in IMQ-induced psoriasis mice. Furthermore, the expression of PPARδ-relevant lipases was also significantly increased. The PPARδ-selective antagonist GSK3787 ameliorated the observed inflammation in the skin of the experimental mice. Based on these results, PPARδ may be a potential target for the effective treatment of psoriasis.

The oncoprotein HBXIP promotes glucose metabolism reprogramming via downregulating SCO2 and PDHA1 in breast cancer

The glucose metabolism reprogramming is a hallmark of cancer. The oncoprotein hepatitis B X-interacting protein (HBXIP) functions in the development of breast cancer. In this study, we supposed that HBXIP might be involved in the glucose metabolism reprogramming in breast cancer. We showed that HBXIP led to increases in generation of intracellular glucose and lactate, as well as decreases in generation of reactive oxygen species. Expression of synthesis of cytochrome c oxidase 2 (SCO2) and pyruvate dehydrogenase alpha 1 (PDHA1), two factors of metabolic switch from oxidative phosphorylation to aerobic glycolysis, was suppressed by HBXIP. In addition, miR-183/182 and miR-96 directly inhibited the expression of SCO2 and PDHA1 through targeting their mRNA coding sequences (CDSs), respectively. Interestingly, HBXIP elevated the miR-183/96/182 cluster expression through hypoxia-inducible factor 1α (HIF1α). The stability of HIF1α was enhanced by HBXIP through disassociating interaction of von Hippel-Lindau protein (pVHL) with HIF1α. Moreover, miR-183 increased the levels of HIF1α protein through directly targeting CDS of VHL mRNA, forming a feedback loop of HIF1α/miR-183/pVHL/HIF1α. In function, HBXIP-elevated miR-183/96/182 cluster enhanced the glucose metabolism reprogramming in vitro. HBXIP-triggered glucose metabolism reprogramming promoted the growth of breast cancer in vivo. Thus, we conclude that the oncoprotein HBXIP enhances glucose metabolism reprogramming through suppressing SCO2 and PDHA1 in breast cancer.

Metabonomics applied in exploring the antitumour mechanism of physapubenolide on hepatocellular carcinoma cells by targeting glycolysis through the Akt-p53 pathway

Metabolomics can be used to identify potential markers and discover new targets for future therapeutic interventions. Here, we developed a novel application of the metabonomics method based on gas chromatography-mass spectrometry (GC/MS) analysis and principal component analysis (PCA) for rapidly exploring the anticancer mechanism of physapubenolide (PB), a cytotoxic withanolide isolated from Physalis species. PB inhibited the proliferation of hepatocellular carcinoma cells in vitro and in vivo, accompanied by apoptosis-related biochemical events, including the cleavage of caspase-3/7/9 and PARP. Metabolic profiling analysis revealed that PB disturbed the metabolic pattern and significantly decreased lactate production. This suggests that the suppression of glycolysis plays an important role in the anti-tumour effects induced by PB, which is further supported by the decreased expression of glycolysis-related genes and proteins. Furthermore, the increased level of p53 and decreased expression of p-Akt were observed, and the attenuated glycolysis and enhanced apoptosis were reversed in the presence of Akt cDNA or p53 siRNA. These results confirm that PB exhibits anti-cancer activities through the Akt-p53 pathway. Our study not only reports for the first time the anti-tumour mechanism of PB, but also suggests that PB is a promising therapeutic agent for use in cancer treatments and that metabolomic approaches provide a new strategy to effectively explore the molecular mechanisms of promising anticancer compounds.

Trial Watch-Immunostimulation with cytokines in cancer therapy

During the past decade, great efforts have been dedicated to the development of clinically relevant interventions that would trigger potent (and hence potentially curative) anticancer immune responses. Indeed, developing neoplasms normally establish local and systemic immunosuppressive networks that inhibit tumor-targeting immune effector cells, be them natural or elicited by (immuno)therapy. One possible approach to boost anticancer immunity consists in the (generally systemic) administration of recombinant immunostimulatory cytokines. In a limited number of oncological indications, immunostimulatory cytokines mediate clinical activity as standalone immunotherapeutic interventions. Most often, however, immunostimulatory cytokines are employed as immunological adjuvants, i.e., to unleash the immunogenic potential of other immunotherapeutic agents, like tumor-targeting vaccines and checkpoint blockers. Here, we discuss recent preclinical and clinical advances in the use of some cytokines as immunostimulatory agents in oncological indications.

Trial Watch: Immunostimulation with Toll-like receptor agonists in cancer therapy

Accumulating preclinical evidence indicates that Toll-like receptor (TLR) agonists efficiently boost tumor-targeting immune responses (re)initiated by most, if not all, paradigms of anticancer immunotherapy. Moreover, TLR agonists have been successfully employed to ameliorate the efficacy of various chemotherapeutics and targeted anticancer agents, at least in rodent tumor models. So far, only three TLR agonists have been approved by regulatory agencies for use in cancer patients. Moreover, over the past decade, the interest of scientists and clinicians in these immunostimulatory agents has been fluctuating. Here, we summarize recent advances in the preclinical and clinical development of TLR agonists for cancer therapy.

GATA4 is a key regulator of steroidogenesis and glycolysis in mouse Leydig cells

Transcription factor GATA4 is expressed in somatic cells of the mammalian testis. Gene targeting studies in mice have shown that GATA4 is essential for proper differentiation and function of Sertoli cells. The role of GATA4 in Leydig cell development, however, remains controversial, because targeted mutagenesis experiments in mice have not shown a consistent phenotype, possibly due to context-dependent effects or compensatory responses. We therefore undertook a reductionist approach to study the function of GATA4 in Leydig cells. Using microarray analysis and quantitative RT-PCR, we identified a set of genes that are down-regulated or up-regulated after small interfering RNA (siRNA)-mediated silencing of Gata4 in the murine Leydig tumor cell line mLTC-1. These same genes were dysregulated when primary cultures of Gata4(flox/flox) adult Leydig cells were subjected to adenovirus-mediated cre-lox recombination in vitro. Among the down-regulated genes were enzymes of the androgen biosynthetic pathway (Cyp11a1, Hsd3b1, Cyp17a1, and Srd5a). Silencing of Gata4 expression in mLTC-1 cells was accompanied by reduced production of sex steroid precursors, as documented by mass spectrometric analysis. Comprehensive metabolomic analysis of GATA4-deficient mLTC-1 cells showed alteration of other metabolic pathways, notably glycolysis. GATA4-depleted mLTC-1 cells had reduced expression of glycolytic genes (Hk1, Gpi1, Pfkp, and Pgam1), lower intracellular levels of ATP, and increased extracellular levels of glucose. Our findings suggest that GATA4 plays a pivotal role in Leydig cell function and provide novel insights into metabolic regulation in this cell type.

Caloric restriction mimetic 2-deoxyglucose alleviated lethal liver injury induced by lipopolysaccharide/D-galactosamine in mice

The glycolytic inhibitor 2-deoxyglucose (2-DG) is a calorie restriction (CR) mimetic produces CR-like beneficial effects in both acute and chronic pathological processes, but whether 2-DG is also helpful in critical and life-threatening situation is not known. In the present study, the potential benefits of 2-DG in lipopolysaccharide/D-galactosamine (LPS/D-Gal)-induced lethal liver injury were investigated. The results indicated that treatment with 2-DG suppressed the elevation of plasma aminotransferases, alleviated the histopathological abnormalities and improved the survival rate of LPS/D-Gal-exposed mice. Treatment with 2-DG also suppressed the production of pro-apoptotic cytokine TNF-α, the phosphorylation of JNK, the activation of caspase cascade and the count of TUNEL-positive apoptotic hepatocytes. These data suggested that the CR mimetic 2-DG could also provide beneficial effects in lethal pathological process such as LPS/D-Gal-induced fulminant liver injury.

Imiquimod-induced AMPK activation causes translation attenuation and apoptosis but not autophagy

BACKGROUND

AMP-activated protein kinase (AMPK), a principal intracellular energy sensor, plays a crucial role in cell growth, proliferation, apoptosis and autophagy. Imiquimod (IMQ) directly exhibits anti-tumor activity through the induction of apoptosis and autophagic cell death.

OBJECTIVE

To evaluate the role of AMPK in IMQ-induced apoptosis and autophagy.

METHODS

The phosphorylation of AMPK and its substrates was detected by immunoblotting. ATP contents were analyzed by an ATP bioluminescence assay. The upstream signaling for AMPK activation was dissected by examination of TLR7/8 expression, over-expression of TLR7/8, the addition of AMPK kinase inhibitors, and the genetic silencing of Myd88 and LKB1. The role of AMPK activation in IMQ-induced autophagy and apoptosis was assessed by inhibiting AMPK, genetically silencing AMPK and over-expressing AMPK dominant-negative mutants. Autophagy and apoptosis were evaluated by a DNA content assay, immunoblotting, EGFP-LC3 puncta detection and acridine orange staining.

RESULTS

IMQ could activate AMPK and autophagy in cancer cells not expressing TLR7/8. IMQ caused ATP depletion and induced LKB1-mediated AMPK activation. The down-regulation of AMPK activity via pharmacological inhibition and genetic silencing resulted in reduced IMQ-induced apoptosis but did not influence autophagy, and this rescue effect was associated with the retention of translation factor activity and anti-apoptotic Bcl-2 family member Mcl-1 protein expression levels.

CONCLUSION

IMQ induces AMPK activation independent of TLR7/8 expression, resulting in translation inhibition and subsequent apoptosis through ATP depletion and LKB1 signaling, in skin tumor cells.

Trial Watch: Toll-like receptor agonists in oncological indications

Toll-like receptors (TLRs) are an evolutionarily conserved group of enzymatically inactive, single membrane-spanning proteins that recognize a wide panel of exogenous and endogenous danger signals. Besides constituting a crucial component of the innate immune response to bacterial and viral pathogens, TLRs appear to play a major role in anticancer immunosurveillance. In line with this notion, several natural and synthetic TLR ligands have been intensively investigated for their ability to boost tumor-targeting immune responses elicited by a variety of immunotherapeutic and chemotherapeutic interventions. Three of these agents are currently approved by the US Food and Drug Administration (FDA) or equivalent regulatory agencies for use in cancer patients: the so-called bacillus Calmette-Guérin, monophosphoryl lipid A, and imiquimod. However, the number of clinical trials testing the therapeutic potential of both FDA-approved and experimental TLR agonists in cancer patients is stably decreasing, suggesting that drug developers and oncologists are refocusing their interest on alternative immunostimulatory agents. Here, we summarize recent findings on the use of TLR agonists in cancer patients and discuss how the clinical evaluation of FDA-approved and experimental TLR ligands has evolved since the publication of our first Trial Watch dealing with this topic.