CK2 inhibition induced PDK4-AMPK axis regulates metabolic adaptation and survival responses in glioma

Stevioside Ameliorates Palmitic Acid-Induced Abnormal Glucose Uptake via the PDK4/AMPK/TBC1D1 Pathway in C2C12 Myotubes

BACKGROUND

Stevioside (SV) with minimal calories is widely used as a natural sweetener in beverages due to its high sweetness and safety. However, the effects of SV on glucose uptake and the pyruvate dehydrogenase kinase isoenzyme (PDK4) as an important protein in the regulation of glucose metabolism, remain largely unexplored. In this study, we used C2C12 skeletal muscle cells that was induced by palmitic acid (PA) to assess the effects and mechanisms of SV on glucose uptake and PDK4.

METHODS

The glucose uptake of C2C12 cells was determined by 2-NBDG; expression of the Pdk4 gene was measured by quantitative real-time PCR; and expression of the proteins PDK4, p-AMPK, TBC1D1 and GLUT4 was assessed by Western blotting.

RESULTS

In PA-induced C2C12 myotubes, SV could significantly promote cellular glucose uptake by decreasing PDK4 levels and increasing p-AMPK and TBC1D1 levels. SV could promote the translocation of GLUT4 from the cytoplasm to the cell membrane in cells. Moreover, in Pdk4-overexpressing C2C12 myotubes, SV decreased the level of PDK4 and increased the levels of p-AMPK and TBC1D1.

CONCLUSION

SV was found to ameliorate PA-induced abnormal glucose uptake via the PDK4/AMPK/TBC1D1 pathway in C2C12 myotubes. Although these results warranted further investigation for validation, they may provide some evidence of SV as a safe natural sweetener for its use in sugar-free beverages to prevent and control T2DM.

Verification of Key Target Molecules for Intramuscular Fat Deposition and Screening of SNP Sites in Sheep from Small-Tail Han Sheep Breed and Its Cross with Suffolk

Intramuscular fat (IMF) is vital for meat tenderness and juiciness. This study aims to explore the IMF deposition mechanism and the related molecular markers in sheep. Two populations, Small-tail Han Sheep (STH) and STH × Suffolk (SFK) F1 (SFK × STH), were used as the research object. Histological staining techniques compared the differences in the longissimus dorsi muscle among populations. A combination of transcriptome sequencing and biological information analysis screened and identified IMF-related target genes. Further, sequencing technology was employed to detect SNP loci of target genes to evaluate their potential as genetic markers. Histological staining revealed that the muscle fiber gap in the SFK × STH F1 was larger and the IMF content was higher. Transcriptome analysis revealed that PIK3R1 and PPARA were candidate genes. Histological experiments revealed that the expressions of PIK3R1 mRNA and PPARA mRNA were lower in SFK × STH F1 compared with the STH. Meanwhile, PIK3R1 and PPARA proteins were located in intramuscular adipocytes and co-located with the lipid metabolism marker molecule (FASN). SNP locus analysis revealed a mutation site in exon 7 of the PIK3R1 gene, which served as a potential genetic marker for IMF deposition. This study's findings will provide a new direction for meat quality breeding in sheep.

Docosahexaenoic Acid Alters Lipid Metabolism Processes via H3K9ac Epigenetic Modification in Dairy Goat

Goat milk is increasingly recognized by consumers due to its high nutritional value, richness in short- and medium-chain fatty acids, and richness in polyunsaturated fatty acids (PUFA). Exogenous supplementation of docosahexaenoic acid (DHA) is an important approach to increasing the content of PUFA in goat milk. Several studies have reported benefits of dietary DHA in terms of human health, including potential against chronic diseases and tumors. However, the mechanisms whereby an increased supply of DHA regulates mammary cell function is unknown. In this study, we investigated the effect of DHA on lipid metabolism processes in goat mammary epithelial cells (GMEC) and the function of H3K9ac epigenetic modifications in this process. Supplementation of DHA promoted lipid droplet accumulation increased the DHA content and altered fatty acid composition in GMEC. Lipid metabolism processes were altered by DHA supplementation through transcriptional programs in GMEC. ChIP-seq analysis revealed that DHA induced genome-wide H3K9ac epigenetic changes in GMEC. Multiomics analyses (H3K9ac genome-wide screening and RNA-seq) revealed that DHA-induced expression of lipid metabolism genes (FASN, SCD1, FADS1, FADS2, LPIN1, DGAT1, MBOAT2), which were closely related with changes in lipid metabolism processes and fatty acid profiles, were regulated by modification of H3K9ac. In particular, DHA increased the enrichment of H3K9ac in the promoter region of PDK4 and promoted its transcription, while PDK4 inhibited lipid synthesis and activated AMPK signaling in GMEC. The activation of the expression of fatty acid metabolism-related genes FASN, FADS2, and SCD1 and their upstream transcription factor SREBP1 by the AMPK inhibitor was attenuated in PDK4-overexpressing GMEC. In conclusion, DHA alters lipid metabolism processes via H3K9ac modifications and the PDK4-AMPK-SREBP1 signaling axis in goat mammary epithelial cells, providing new insights into the mechanism through which DHA affects mammary cell function and regulates milk fat metabolism.

CK2 and the Hallmarks of Cancer

Cancer is a leading cause of death worldwide. Casein kinase 2 (CK2) is commonly dysregulated in cancer, impacting diverse molecular pathways. CK2 is a highly conserved serine/threonine kinase, constitutively active and ubiquitously expressed in eukaryotes. With over 500 known substrates and being estimated to be responsible for up to 10% of the human phosphoproteome, it is of significant importance. A broad spectrum of diverse types of cancer cells has been already shown to rely on disturbed CK2 levels for their survival. The hallmarks of cancer provide a rationale for understanding cancer’s common traits. They constitute the maintenance of proliferative signaling, evasion of growth suppressors, resisting cell death, enabling of replicative immortality, induction of angiogenesis, the activation of invasion and metastasis, as well as avoidance of immune destruction and dysregulation of cellular energetics. In this work, we have compiled evidence from the literature suggesting that CK2 modulates all hallmarks of cancer, thereby promoting oncogenesis and operating as a cancer driver by creating a cellular environment favorable to neoplasia.

Identification of Immune-Related Risk Characteristics and Prognostic Value of Immunophenotyping in TNBC

Background: Triple-negative breast cancer (TNBC) is not sensitive to targeted therapy with HER-2 monoclonal antibody and endocrine therapy due to lack of ER, PR, and HER-2 receptors. TNBC is a breast cancer subtype with the worst prognosis and the highest mortality rate compared with other subtypes. Materials and Methods: Breast cancer-related data were retrieved from The Cancer Genome Atlas (TCGA) database, and 116 cases of triple-negative breast cancer were identified from the data. GSE31519 dataset was retrieved from Gene Expression Omnibus (GEO) database, comprising a total of 68 cases with TNBC. Survival analysis was performed based on immune score, infiltration score and mutation score to explore differences in prognosis of different immune types. Analysis of differentially expressed genes was conducted and GSEA analysis based on these genes was conducted to explore the potential mechanism. Results: The findings showed that comprehensive immune typing is highly effective and accurate in assessing prognosis of TNBC patients. Analysis showed that MMP9, CXCL9, CXCL10, CXCL11 and CD7 are key genes that may affect immune typing of TNBC patients and play an important role in prediction of prognosis in TNBC patients. Conclusion: The current study presents an evaluation system based on immunophenotyping, which provides a more accurate prognostic evaluation tool for TNBC patients. Differentially expressed genes can be targeted to improve treatment of TNBC.

Reversing tozasertib resistance in glioma through inhibition of pyruvate dehydrogenase kinases

Acquired resistance to conventional chemotherapeutic agents limits their effectiveness and can cause cancer treatment to fail. Because enzymes in the aurora kinase family are vital regulators of several mitotic events, we reasoned that targeting these kinases with tozasertib, a pan‐aurora kinase inhibitor, would not only cause cytokinesis defects, but also induce cell death in high‐grade pediatric and adult glioma cell lines. We found that tozasertib induced cell cycle arrest, increased mitochondrial permeability and reactive oxygen species generation, inhibited cell growth and migration, and promoted cellular senescence and pro‐apoptotic activity. However, sustained exposure to tozasertib at clinically relevant concentrations conferred resistance, which led us to examine the mechanistic basis for the emergence of drug resistance. RNA‐sequence analysis revealed a significant upregulation of the gene encoding pyruvate dehydrogenase kinase isoenzyme 4 (PDK4), a pyruvate dehydrogenase (PDH) inhibitory kinase that plays a crucial role in the control of metabolic flexibility under various physiological conditions. Upregulation of PDK1, PDK2, PDK3, or PDK4 protein levels was positively correlated with tozasertib‐induced resistance through inhibition of PDH activity. Tozasertib‐resistant cells exhibited increased mitochondrial mass as measured by 10‐N‐nonyl‐Acridine Orange. Inhibition of PDK with dichloroacetate resulted in increased mitochondrial permeability and cell death in tozasertib‐resistant glioma cell lines. Based on these results, we believe that PDK is a selective target for the tozasertib resistance phenotype and should be considered for further preclinical evaluations.

Targeting pyruvate dehydrogenase kinase signaling in the development of effective cancer therapy

Pyruvate is irreversibly decarboxylated to acetyl coenzyme A by mitochondrial pyruvate dehydrogenase complex (PDC). Decarboxylation of pyruvate is considered a crucial step in cell metabolism and energetics. The cancer cells prefer aerobic glycolysis rather than mitochondrial oxidation of pyruvate. This attribute of cancer cells allows them to sustain under indefinite proliferation and growth. Pyruvate dehydrogenase kinases (PDKs) play critical roles in many diseases because they regulate PDC activity. Recent findings suggest an altered metabolism of cancer cells is associated with impaired mitochondrial function due to PDC inhibition. PDKs inhibit the PDC activity via phosphorylation of the E1a subunit and subsequently cause a glycolytic shift. Thus, inhibition of PDK is an attractive strategy in anticancer therapy. This review highlights that PDC/PDK axis could be implicated in cancer's therapeutic management by developing potential small-molecule PDK inhibitors. In recent years, a dramatic increase in the targeting of the PDC/PDK axis for cancer treatment gained an attention from the scientific community. We further discuss breakthrough findings in the PDC-PDK axis. In addition, structural features, functional significance, mechanism of activation, involvement in various human pathologies, and expression of different forms of PDKs (PDK1-4) in different types of cancers are discussed in detail. We further emphasized the gene expression profiling of PDKs in cancer patients to prognosis and therapeutic manifestations. Additionally, inhibition of the PDK/PDC axis by small molecule inhibitors and natural compounds at different clinical evaluation stages has also been discussed comprehensively.

Protein kinase CK2: a potential therapeutic target for diverse human diseases

CK2 is a constitutively active Ser/Thr protein kinase, which phosphorylates hundreds of substrates, controls several signaling pathways, and is implicated in a plethora of human diseases. Its best documented role is in cancer, where it regulates practically all malignant hallmarks. Other well-known functions of CK2 are in human infections; in particular, several viruses exploit host cell CK2 for their life cycle. Very recently, also SARS-CoV-2, the virus responsible for the COVID-19 pandemic, has been found to enhance CK2 activity and to induce the phosphorylation of several CK2 substrates (either viral and host proteins). CK2 is also considered an emerging target for neurological diseases, inflammation and autoimmune disorders, diverse ophthalmic pathologies, diabetes, and obesity. In addition, CK2 activity has been associated with cardiovascular diseases, as cardiac ischemia-reperfusion injury, atherosclerosis, and cardiac hypertrophy. The hypothesis of considering CK2 inhibition for cystic fibrosis therapies has been also entertained for many years. Moreover, psychiatric disorders and syndromes due to CK2 mutations have been recently identified. On these bases, CK2 is emerging as an increasingly attractive target in various fields of human medicine, with the advantage that several very specific and effective inhibitors are already available. Here, we review the literature on CK2 implication in different human pathologies and evaluate its potential as a pharmacological target in the light of the most recent findings.

PDK4 promotes tumorigenesis and cisplatin resistance in lung adenocarcinoma via transcriptional regulation of EPAS1

The use of cisplatin for the treatment of non-small cell lung cancer has long been constrained by the rapid acquisition of tumor cell chemoresistance. In the present study, we sought to better elucidate the molecular mechanisms underlying this resistance phenotype. To that end, we assessed gene expression patterns in cisplatin-resistant lung adenocarcinoma cells, revealing pyruvate dehydrogenase lipoamide kinase isozyme 4 (PDK4) to be the most up-regulated kinase in resistant cells. We further found PDK4 upregulation to be directly linked with the acquisition of chemoresistance, driving enhanced tumor cell growth in vitro and in vivo. In clinical samples, we also found that PDK4 upregulation was detectable in patients with lung adenocarcinoma and that it was correlated with a poorer prognosis for these patients. From a mechanistic perspective, we further determined that PDK4 was able to promote lung adenocarcinoma cell growth and cisplatin resistance at least in part via regulating endothelial PAS domain-containing protein 1 (EPAS1) expression, thus highlighting PDK4 as a potentially viable therapeutic target in efforts to treat lung adenocarcinoma patients that have become resistant to cisplatin.

Role of Protein Kinase CK2 in Aberrant Lipid Metabolism in Cancer

Uncontrolled proliferation is a feature defining cancer and it is linked to the ability of cancer cells to effectively adapt their metabolic needs in response to a harsh tumor environment. Metabolic reprogramming is considered a hallmark of cancer and includes increased glucose uptake and processing, and increased glutamine utilization, but also the deregulation of lipid and cholesterol-associated signal transduction, as highlighted in recent years. In the first part of the review, we will (i) provide an overview of the major types of lipids found in eukaryotic cells and their importance as mediators of intracellular signaling pathways (ii) analyze the main metabolic changes occurring in cancer development and the role of oncogenic signaling in supporting aberrant lipid metabolism and (iii) discuss combination strategies as powerful new approaches to cancer treatment. The second part of the review will address the emerging role of CK2, a conserved serine/threonine protein kinase, in lipid homeostasis with an emphasis regarding its function in lipogenesis and adipogenesis. Evidence will be provided that CK2 regulates these processes at multiple levels. This suggests that its pharmacological inhibition combined with dietary restrictions and/or inhibitors of metabolic targets could represent an effective way to undermine the dependency of cancer cells on lipids to interfere with tumor progression.

Deciphering the metabolic role of AMPK in cancer multi-drug resistance

Multi-drug resistance (MDR) is a curious bottleneck in cancer research and chemotherapy, whereby some cells rapidly adapt to the tumor microenvironment via a myriad of heterogeneous metabolic activities. Despite being a major impediment to treatment, there is a silver lining: control over metabolic regulation could be an effective approach to overcome or correct resistance pathways. In this critical review, we comprehensively and carefully curated and analyzed large networks of previously identified proteins associated with metabolic adaptation in MDR. We employed data and text mining to study and categorize more than 600 studies in PubMed, with particular focus on AMPK, a central and fundamental modulator in the energy metabolism network that has been specifically implicated in cancer MDR pathways. We have identified one protein set of metabolic adaptations with 137 members closely related to cancer MDR processes, and a second protein set with 165 members derived from AMPK-based networks, with 28 proteins found at the intersection between the two sets. Furthermore, according to genomics analysis of the cancer genome atlas (TCGA) provisional data, the highest alteration frequency (80.0%) of the genes encoding the intersected proteins (28 proteins), ranked three cancer types with quite remarkable significance across 166 studies. The hierarchical relationships of the entire identified gene and protein networks indicate broad correlations in AMPK-mediated metabolic regulation pathways, which we use decipher and depict the metabolic roles of AMPK and demonstrate the potential of metabolic control for therapeutic intervention in MDR.

CK2 inhibition protects white matter from ischemic injury

Strokes occur predominantly in the elderly and white matter (WM) is injured in most strokes, contributing to the disability associated with clinical deficits. Casein kinase 2 (CK2) is expressed in neuronal cells and was reported to be neuroprotective during cerebral ischemia. Recently, we reported that CK2 is abundantly expressed by glial cells and myelin. However, in contrast to its role in cerebral (gray matter) ischemia, CK2 activation during ischemia mediated WM injury via the CDK5 and AKT/GSK3β signaling pathways (Bastian et al., 2018). Subsequently, CK2 inhibition using the small molecule inhibitor CX-4945 correlated with preservation of oligodendrocytes as well as conservation of axon structure and axonal mitochondria, leading to improved functional recovery. Notably, CK2 inhibition promoted WM function when applied before or after ischemic injury by differentially regulating the CDK5 and AKT/GSK3β pathways. Specifically, blockade of the active conformation of AKT conferred post-ischemic protection to young, aging, and old WM, suggesting a common therapeutic target across age groups. CK2 inhibitors are currently being used in clinical trials for cancer patients; therefore, it is important to consider the potential benefits of CK2 inhibitors during an ischemic attack.

CK2 modulates adipocyte insulin-signaling and is up-regulated in human obesity

Insulin plays a major role in glucose metabolism and insulin-signaling defects are present in obesity and diabetes. CK2 is a pleiotropic protein kinase implicated in fundamental cellular pathways and abnormally elevated in tumors. Here we report that in human and murine adipocytes CK2-inhibition decreases the insulin-induced glucose-uptake by counteracting Akt-signaling and GLUT4-translocation to the plasma membrane. In mice CK2 acts on insulin-signaling in adipose tissue, liver and skeletal muscle and its acute inhibition impairs glucose tolerance. Notably, CK2 protein-level and activity are greatly up-regulated in white adipose tissue from ob/ob and db/db mice as well as from obese patients, regardless the severity of their insulin-resistance and the presence of pre-diabetes or overt type 2 diabetes. Weight loss obtained by both bariatric surgery or hypocaloric diet reverts CK2 hyper-activation to normal level. Our data suggest a central role of CK2 in insulin-sensitivity, glucose homeostasis and adipose tissue remodeling. CK2 up-regulation is identified as a hallmark of adipose tissue pathological expansion, suggesting a new potential therapeutic target for human obesity.

Reciprocal role of SIRT6 and Hexokinase 2 in the regulation of autophagy driven monocyte differentiation

Emerging evidences suggest the impact of autophagy on differentiation but the underlying molecular links between metabolic restructuring and autophagy during monocyte differentiation remain elusive. An increase in PPARγ, HK2 and SIRT6 expression was observed upon PMA induced monocyte differentiation. While PPARγ positively regulated HK2 and SIRT6 expression, the latter served as a negative regulator of HK2. Changes in expression of these metabolic modelers were accompanied by decreased glucose uptake and increase in Chibby, a potent antagonist of β-catenin/Wnt pathway. Knockdown of Chibby abrogated PMA induced differentiation. While inhibition of HK2 either by Lonidamine or siRNA further elevated PMA induced Chibby, mitochondrial ROS, TIGAR and LC3II levels; siRNA mediated knock-down of SIRT6 exhibited contradictory effects as compared to HK2. Notably, inhibition of autophagy increased HK2, diminished Chibby level and CD33 expression. In addition, PMA induced expression of cytoskeletal architectural proteins, CXCR4, phagocytosis, acquisition of macrophage phenotypes and release of pro-inflammatory mediators was found to be HK2 dependent. Collectively, our findings highlight the previously unknown reciprocal influence of SIRT6 and HK2 in regulating autophagy driven monocyte differentiation.

Targeting Protein Kinase CK2: Evaluating CX-4945 Potential for GL261 Glioblastoma Therapy in Immunocompetent Mice

Glioblastoma (GBM) causes poor survival in patients even with aggressive treatment. Temozolomide (TMZ) is the standard chemotherapeutic choice for GBM treatment but resistance always ensues. Protein kinase CK2 (CK2) contributes to tumour development and proliferation in cancer, and it is overexpressed in human GBM. Accordingly, targeting CK2 in GBM may benefit patients. Our goal has been to evaluate whether CK2 inhibitors (iCK2s) could increase survival in an immunocompetent preclinical GBM model. Cultured GL261 cells were treated with different iCK2s including CX-4945, and target effects evaluated in vitro. CX-4945 was found to decrease CK2 activity and Akt(S129) phosphorylation in GL261 cells. Longitudinal in vivo studies with CX-4945 alone or in combination with TMZ were performed in tumour-bearing mice. Increase in survival (p < 0.05) was found with combined CX-4945 and TMZ metronomic treatment (54.7 ± 11.9 days, n = 6) when compared to individual metronomic treatments (CX-4945: 24.5 ± 2.0 and TMZ: 38.7 ± 2.7, n = 6) and controls (22.5 ± 1.2, n = 6). Despite this, CX-4945 did not improve mice outcome when administered on every/alternate days, either alone or in combination with 3-cycle TMZ. The highest survival rate was obtained with the metronomic combined TMZ+CX-4945 every 6 days, pointing to the participation of the immune system or other ancillary mechanism in therapy response.

CK2-An Emerging Target for Neurological and Psychiatric Disorders

Protein kinase CK2 has received a surge of attention in recent years due to the evidence of its overexpression in a variety of solid tumors and multiple myelomas as well as its participation in cell survival pathways. CK2 is also upregulated in the most prevalent and aggressive cancer of brain tissue, glioblastoma multiforme, and in preclinical models, pharmacological inhibition of the kinase has proven successful in reducing tumor size and animal mortality. CK2 is highly expressed in the mammalian brain and has many bona fide substrates that are crucial in neuronal or glial homeostasis and signaling processes across synapses. Full and conditional CK2 knockout mice have further elucidated the importance of CK2 in brain development, neuronal activity, and behavior. This review will discuss recent advances in the field that point to CK2 as a regulator of neuronal functions and as a potential novel target to treat neurological and psychiatric disorders.

Metformin activation of AMPK-dependent pathways is neuroprotective in human neural stem cells against Amyloid-beta-induced mitochondrial dysfunction

Alzheimer's disease (AD) is the general consequence of dementia and is diagnostic neuropathology by the cumulation of amyloid-beta (Aβ) protein aggregates, which are thought to promote mitochondrial dysfunction processes leading to neurodegeneration. AMP-activated protein kinase (AMPK), a critical regulator of energy homeostasis and a major player in lipid and glucose metabolism, is potentially implied in the mitochondrial deficiency of AD. Metformin, one of the widespread used anti- metabolic disease drugs, use its actions in part by stimulation of AMPK. While the mechanisms of AD are well established, the neuronal roles for AMPK in AD are still not well understood. In the present study, human neural stem cells (hNSCs) exposed to Aβ had significantly reduced cell viability, which correlated with decreased AMPK, neuroprotective genes (Bcl-2 and CREB) and mitochondria associated genes (PGC1α, NRF-1 and Tfam) expressions, as well as increased activation of caspase 3/9 activity and cytosolic cytochrome c. Co-treatment with metformin distinct abolished the Aβ-caused actions in hNSCs. Metformin also significantly rescued hNSCs from Aβ-mediated mitochondrial deficiency (lower D-loop level, mitochondrial mass, maximal respiratory function, COX activity, and mitochondrial membrane potential). Importantly, co-treatment with metformin significantly restored fragmented mitochondria to almost normal morphology in the hNSCs with Aβ. These findings extend our understanding of the central role of AMPK in Aβ-related neuronal impairment. Thus, a better understanding of AMPK might assist in both the recognition of its critical effects and the implementation of new therapeutic strategies in the treatment of AD.