Calcium signalling links MYC to NUAK1

NUAK: never underestimate a kinase

NUAK1 and NUAK2 belong to a family of kinases related to the catalytic α-subunits of the AMP-activated protein kinase (AMPK) complexes. Despite canonical activation by the tumour suppressor kinase LKB1, both NUAKs exhibit a spectrum of activities that favour tumour development and progression. Here, we review similarities in structure and function of the NUAKs, their regulation at gene, transcript and protein level, and discuss their phosphorylation of specific downstream targets in the context of the signal transduction pathways and biological activities regulated by each or both NUAKs.

LKB1 biology: assessing the therapeutic relevancy of LKB1 inhibitors

Liver Kinase B1 (LKB1), encoded by Serine-Threonine Kinase 11 (STK11), is a master kinase that regulates cell migration, polarity, proliferation, and metabolism through downstream adenosine monophosphate-activated protein kinase (AMPK) and AMPK-related kinase signalling. Since genetic screens identified STK11 mutations in Peutz-Jeghers Syndrome, STK11 mutants have been implicated in tumourigenesis labelling it as a tumour suppressor. In support of this, several compounds reduce tumour burden through upregulating LKB1 signalling, and LKB1-AMPK agonists are cytotoxic to tumour cells. However, in certain contexts, its role in cancer is paradoxical as LKB1 promotes tumour cell survival by mediating resistance against metabolic and oxidative stressors. LKB1 deficiency has also enhanced the selectivity and cytotoxicity of several cancer therapies. Taken together, there is a need to develop LKB1-specific pharmacological compounds, but prior to developing LKB1 inhibitors, further work is needed to understand LKB1 activity and regulation. However, investigating LKB1 activity is strenuous as cell/tissue type, mutations to the LKB1 signalling pathway, STE-20-related kinase adaptor protein (STRAD) binding, Mouse protein 25-STRAD binding, splicing variants, nucleocytoplasmic shuttling, post-translational modifications, and kinase conformation impact the functional status of LKB1. For these reasons, guidelines to standardize experimental strategies to study LKB1 activity, associate proteins, spliced isoforms, post-translational modifications, and regulation are of upmost importance to the development of LKB1-specific therapies. Therefore, to assess the therapeutic relevancy of LKB1 inhibitors, this review summarizes the importance of LKB1 in cell physiology, highlights contributors to LKB1 activation, and outlines the benefits and risks associated with targeting LKB1.

Novel kinase 1 regulates CD8+T cells as a potential therapeutic mechanism for idiopathic pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is a rare, chronic and progressively worsening lung disease that poses a significant threat to patient prognosis, with a mortality rate exceeding that of some common malignancies. Effective methods for early diagnosis and treatment remain for this condition are elusive. In our study, we used the GEO database to access second-generation sequencing data and associated clinical information from IPF patients. By utilizing bioinformatics techniques, we identified crucial disease-related genes and their biological functions, and characterized their expression patterns. Furthermore, we mapped out the immune landscape of IPF, which revealed potential roles for novel kinase 1 and CD8+T cells in disease progression and outcome. These findings can aid the development of new strategies for the clinical diagnosis and treatment of IPF.

LncRNA HOTAIR Enhances Epithelial-to-mesenchymal Transition to Promote the Migration and Invasion of Liver Cancer by Regulating NUAK1 via Epigenetic Inhibition miR-145-5p Expression

LncRNA HOTAIR play important roles in the epigenetic regulation of carcinogenesis and progression in liver cancer. Previous studies suggest that the overexpression of HOTAIR predicts poor prognosis. In this study, through transcriptome sequencing data and in vitro experiments, we found that HOTAIR were more highly expressed and there is significantly positive relationship between HOTAIR and NUAK1 in liver cancer tissues and cell lines. miR-145-5p was downregulated and showed negative correlation with HOTAIR and NUAK1. Transfect Sh-HOTAIR, LZRS-HOTAIR, miR-145 mimic, miR-145 inhibitor to change the expression of HOTAIR and miR-145-5p. The addition of HTH-01-015 inhibits the expression of NUAK1. HOTAIR knockdown, miR-145-5p upregulation and NUAK1 inhibition all repressed migration, invasion and metastasis and reversed the epithelial-to-mesenchymal transition in SNU-387 and HepG2 cells. We also showed that HOTAIR recruiting and binding PRC2 (EZH2) epigenetically represses miR-145-5p, which controls the target NUAK1, thus contributing to liver cancer cell-EMT process and accelerating tumor metastasis. Moreover, it is demonstrated that HOTAIR crosstalk with miR-145-5p/NUAK1 during epigenetic regulation. Our findings indicate that HOTAIR/miR-145-5p/NUAK1 axis acts as an EMT regulator and may be candidate prognostic biomarker and targets for new therapies in liver cancer.

NUAK1 governs centrosome replication in pancreatic cancer via MYPT1/PP1β and GSK3β-dependent regulation of PLK4

The AMP-activated protein kinase (AMPK)-related kinase NUAK1 (NUAK family SNF1-like kinase 1) has emerged as a potential vulnerability in MYC-dependent cancer but the biological roles of NUAK1 in different settings are poorly characterised, and the spectrum of cancer types that exhibit a requirement for NUAK1 is unknown. Unlike canonical oncogenes, NUAK1 is rarely mutated in cancer and appears to function as an obligate facilitator rather than a cancer driver per se. Although numerous groups have developed small-molecule NUAK inhibitors, the circumstances that would trigger their use and the unwanted toxicities that may arise as a consequence of on-target activity are thus undetermined. Reasoning that MYC is a key effector of RAS pathway signalling and the GTPase KRAS is almost uniformly mutated in pancreatic ductal adenocarcinoma (PDAC), we investigated whether this cancer type exhibits a functional requirement for NUAK1. Here, we show that high NUAK1 expression is associated with reduced overall survival in PDAC and that inhibition or depletion of NUAK1 suppresses growth of PDAC cells in culture. We identify a previously unknown role for NUAK1 in regulating accurate centrosome duplication and show that loss of NUAK1 triggers genomic instability. The latter activity is conserved in primary fibroblasts, raising the possibility of undesirable genotoxic effects of NUAK1 inhibition.

Gene signature of m6A-related targets to predict prognosis and immunotherapy response in ovarian cancer

PURPOSE

The aim of the study was to construct a risk score model based on m6A-related targets to predict overall survival and immunotherapy response in ovarian cancer.

METHODS

The gene expression profiles of 24 m6A regulators were extracted. Survival analysis screened 9 prognostic m6A regulators. Next, consensus clustering analysis was applied to identify clusters of ovarian cancer patients. Furthermore, 47 phenotype-related differentially expressed genes, strongly correlated with 9 prognostic m6A regulators, were screened and subjected to univariate and the least absolute shrinkage and selection operator (LASSO) Cox regression. Ultimately, a nomogram was constructed which presented a strong ability to predict overall survival in ovarian cancer.

RESULTS

CBLL1, FTO, HNRNPC, METTL3, METTL14, WTAP, ZC3H13, RBM15B and YTHDC2 were associated with worse overall survival (OS) in ovarian cancer. Three m6A clusters were identified, which were highly consistent with the three immune phenotypes. What is more, a risk model based on seven m6A-related targets was constructed with distinct prognosis. In addition, the low-risk group is the best candidate population for immunotherapy.

CONCLUSION

We comprehensively analyzed the m6A modification landscape of ovarian cancer and detected seven m6A-related targets as an independent prognostic biomarker for predicting survival. Furthermore, we divided patients into high- and low-risk groups with distinct prognosis and select the optimum population which may benefit from immunotherapy and constructed a nomogram to precisely predict ovarian cancer patients' survival time and visualize the prediction results.

Differential expression patterns of genes associated with metabolisms, muscle growth and repair in Pectoralis major muscles of fast- and medium-growing chickens

The aim of this study was to investigate the expression of genes related to muscle growth, hypoxia and oxidative stress responses, a multi-substrate serine/threonine-protein kinase (AMPK) and AMPK-related kinases, carbohydrate metabolism, satellite cells activities and fibro- adipogenic progenitors (FAPs) in fast-growing (FG) (n = 30) and medium-growing (MG) chickens (n = 30). Pectoralis major muscles were collected at 7d, 14d, 21d, 28d, 35d and 42d of age. According to their macroscopic features, the samples from FG up to 21d of age were classified as unaffected, while all samples collected at an older age exhibited macroscopic features ascribable to white striping and/or wooden breast abnormalities. In contrast, MG samples did not show any feature associated to muscle disorders. The absolute transcript abundance of 33 target genes was examined by droplet digital polymerase chain reaction. The results showed differential gene expression profiles between FG and MG chickens at different ages. While most genes remained unchanged in MG chickens, the expression patterns of several genes in FG were significantly affected by age. Genes encoding alpha 1, alpha 2, beta 2 and gamma 3 isoforms of AMPK, as well as AMPK-related kinases, were identified as differentially expressed between the two strains. The results support the hypothesis of oxidative stress-induced muscle damage with metabolic alterations in FG chickens. An increased expression of ANXA2, DES, LITAF, MMP14, MYF5 and TGFB1 was observed in FG strain. The results suggest the occurrence of dysregulation of FAP proliferation and differentiation occurring during muscle repair. FAPs could play an important role in defining the proliferation of connective tissue (fibrosis) and deposition of intermuscular adipose tissue which represents distinctive traits of muscle abnormalities. Overall, these findings demonstrate that dysregulated molecular processes associated with myopathic lesions in chickens are strongly influenced by growth rate, and, to some extent, by age.

Discovery of a novel NUAK1 inhibitor against pancreatic cancer

The novel (nua) kinase family 1 (NUAK1) is an AMPK-related kinase and its expression is associated with tumor malignancy and poor prognosis in several types of cancer, suggesting its potential as a target for cancer therapy. Therefore, the development of NUAK1-targeting inhibitors could improve therapeutic outcomes in cancer. We synthesized KI-301670, a novel NUAK1 inhibitor, and assessed its anticancer effects and mechanism of action in pancreatic cancer. It effectively inhibited pancreatic cancer growth and proliferation, and induced cell cycle arrest, markedly G0/G1 arrest, by increasing the expression of p27 and decreasing expression of p-Rb and E2F1. Additionally, the apoptotic effect of KI-301670 was observed by an increase in cleaved PARP, TUNEL-positive cells, and annexin V cell population, as well as the release of cytochrome c via the loss of mitochondrial membrane potential. KI-301670 inhibited the migration and invasion of pancreatic cancer cells. Mechanistically, KI-301670 effectively inhibited the PI3K/AKT pathway in pancreatic cancer cells. Furthermore, it significantly attenuated tumor growth in a mouse xenograft tumor model. Our results demonstrate that a novel NUAK1 inhibitor, KI-301670, exerts anti-tumor effects by directly suppressing cancer cell growth by affecting the PI3K/AKT pathway, suggesting that it could be a novel therapeutic candidate for pancreatic cancer treatment.

Transcriptional changes in dendritic cells underlying allergen specific induced tolerance in a mouse model

To investigate food allergy-tolerance mechanisms induced through allergen-specific immunotherapy we used RNA-Sequencing to measure gene expression in lymph-node-derived dendritic cells from Pru p 3-anaphylactic mice after immunotherapy with glycodendropeptides at 2 nM and 5 nM, leading to permanent tolerance and short-term desensitization, respectively. Gene expression was also measured in mice receiving no immunotherapy (anaphylaxis); and in which anaphylaxis could never occur (antigen-only). Compared to anaphylaxis, the antigen-only group showed the greatest number of expression-changes (411), followed by tolerant (186) and desensitized (119). Only 29 genes changed in all groups, including Il12b, Cebpb and Ifngr1. The desensitized group showed enrichment for genes related to chronic inflammatory response, secretory granule, and regulation of interleukin-12 production; the tolerant group showed genes related to cytokine receptor activity and glucocorticoid receptor binding, suggesting distinct pathways for similar outcomes. We identified genes and processes potentially involved in the restoration of long-term tolerance via allergen-specific immunotherapy, representing potential prognostic biomarkers.

Ribosomal biogenesis regulator DIMT1 controls β-cell protein synthesis, mitochondrial function, and insulin secretion

We previously reported that loss of mitochondrial transcription factor B1 (TFB1M) leads to mitochondrial dysfunction and is involved in the pathogenesis of type 2 diabetes (T2D). Whether defects in ribosomal processing impact mitochondrial function and could play a pathogenetic role in β-cells and T2D is not known. To this end, we explored expression and the functional role of dimethyladenosine transferase 1 homolog (DIMT1), a homolog of TFB1M and a ribosomal RNA (rRNA) methyltransferase implicated in the control of rRNA. Expression of DIMT1 was increased in human islets from T2D donors and correlated positively with expression of insulin mRNA, but negatively with insulin secretion. We show that silencing of DIMT1 in insulin-secreting cells impacted mitochondrial function, leading to lower expression of mitochondrial OXPHOS proteins, reduced oxygen consumption rate, dissipated mitochondrial membrane potential, and a slower rate of ATP production. In addition, the rate of protein synthesis was retarded upon DIMT1 deficiency. Consequently, we found that DIMT1 deficiency led to perturbed insulin secretion in rodent cell lines and islets, as well as in a human β-cell line. We observed defects in rRNA processing and reduced interactions between NIN1 (RPN12) binding protein 1 homolog (NOB-1) and pescadillo ribosomal biogenesis factor 1 (PES-1), critical ribosomal subunit RNA proteins, the dysfunction of which may play a part in disturbing protein synthesis in β-cells. In conclusion, DIMT1 deficiency perturbs protein synthesis, resulting in mitochondrial dysfunction and disrupted insulin secretion, both potential pathogenetic processes in T2D.

In vivo genome-wide CRISPR screens identify SOCS1 as intrinsic checkpoint of CD4+ TH1 cell response

[Figure: see text].

NUAK1 and NUAK2 Fine-Tune TGF-β Signaling

Simple Summary

TGF-β is a growth factor implicated in a plethora of processes and malignancies, which include cancer and fibrosis. Via binding to its receptor, TGF-β activates a complex intracellular signal transduction pathway, which is controlled by many forms of positive as well as negative feedback. The integrated sum of this feedback determines the outcome and cellular response to TGF-β. In this review, we discuss the role of NUAK1 and NUAK2, a subgroup of the 5′AMP-activated protein kinase family, in providing feedback on intracellular TGF-β signaling. In addition, we discuss how NUAKs mechanistically augment or attenuate the TGF-β response to steer the cell towards a specific output. Understanding the role of NUAKs may aid in developing specific therapeutic agents to combat TGF-β-dependent disease.

Abstract

Transforming growth factor-β (TGF-β) signaling plays a key role in governing various cellular processes, extending from cell proliferation and apoptosis to differentiation and migration. Due to this extensive involvement in the regulation of cellular function, aberrant TGF-β signaling is frequently implicated in the formation and progression of tumors. Therefore, a full understanding of the mechanisms of TGF-β signaling and its key components will provide valuable insights into how this intricate signaling cascade can shift towards a detrimental course. In this review, we discuss the interplay between TGF-β signaling and the AMP-activated protein kinase (AMPK)-related NUAK kinase family. We highlight the function and regulation of these kinases with focus on the pivotal role NUAK1 and NUAK2 play in regulating TGF-β signaling. Specifically, TGF-β induces the expression of NUAK1 and NUAK2 that regulates TGF-β signaling output in an opposite manner. Besides the focus on the TGF-β pathway, we also present a broader perspective on the expression and signaling interactions of the NUAK kinases to outline the broader functions of these protein kinases.

Role of ARK5 in cancer and other diseases (Review)

Malignant tumors are often exposed to hypoxic and glucose-starved microenvironments. AMP-activated protein kinase (AMPK) is an energy sensor that is stimulated during energy-deficient conditions and protects cells from hypoxic injury by regulating metabolism. AMPK-related protein kinase 5 (ARK5) is a member of the catalytic sub-unit of the AMPK family and has an important role in energy regulation and hypoxia. ARK5 is regulated by Akt and liver kinase B1 and is associated with numerous tumor-related molecules to exert the negative effects of tumors. Studies have revealed ARK5 overexpression in cases of tumor invasion and metastasis and a positive association with the degree of cancer cell malignancy, which is regarded as a key element in determining cancer prognosis. Furthermore, ARK5 downregulation improves drug sensitivity through the epithelial-mesenchymal transition pathway, indicating that it may be a potential therapeutic target. In other non-cancer conditions, ARK5 has various roles in neurodegenerative diseases (Alzheimer's and Huntington's disease), renal disorders (diabetic nephropathy and renal fibrosis) and physiological processes (striated muscle generation). In the present review, the upstream and downstream molecular pathways of ARK5 in cancer and other diseases are described and potential therapeutic strategies are discussed.

AMPKα-like proteins as LKB1 downstream targets in cell physiology and cancer

One of the key events in cancer development is the ability of tumor cells to overcome nutrient deprivation and hypoxia. Among proteins performing metabolic adaptation to the various cellular nutrient conditions, liver kinase B 1 (LKB1) and its main downstream target adenosine monophosphate (AMP)-activated protein kinase α (AMPKα) are important sensors of energy requirements within the cell. Although LKB1 was originally described as a tumor suppressor, given its role in metabolism, it potentially acts as a double-edged sword. AMPKα, a master regulator of cell energy demands, is activated when ATP level drops under a certain threshold, responding accordingly through its downstream targets. Twelve downstream kinase targets of LKB1 have been described as AMPKα-like proteins. This group is comprised of novel (nua) kinase family (NUAK) kinases (NUAK1 and 2) linked to cell cycle progression and ultraviolet (UV)-damage; microtubule affinity regulating kinases (MARKs) (MARK1, MARK2, MARK3, and MARK4) that are involved in cell polarity; salt inducible kinases (SIK) (SIK1, SIK2, also known as Qin-induced kinase or QIK and SIK3) that are implicated in cell metabolism and adipose tissue development and mitotic regulation; maternal embryonic leuzine zipper kinase (MELK) that regulate oocyte maturation; and finally brain selective kinases (BRSKs) (BRSK1 and 2), which have been mainly characterized in the brain due to their role in neuronal polarization. Thus, many efforts have been made in order to harness LKB1 kinase and its downstream targets as a possible therapeutic hub in tumor development and propagation. In this review, we describe LKB1 and its downstream target AMPK summarize major functions of various AMPK-like proteins, while focusing on biological functions of BRSK1 and 2 in different models.

Development and Therapeutic Potential of NUAKs Inhibitors

NUAK isoforms, NUAK1 (ARK5) and NUAK2 (SNARK), are important members of the AMPK family of protein kinases. They are involved in a broad spectrum of physiological and cellular events, and sometimes their biological roles overlap. NUAK isoform dysregulation is associated with numerous pathological disorders, including neurodegeneration, metastatic cancer, and diabetes. Therefore, they are promising therapeutic targets in metabolic diseases and cancers; consequently, various NUAK-targeted inhibitors have been disclosed. The first part of this review comprises a brief discussion of the homology, expression, structure, and characteristics of NUAK isoforms. The second part focuses on NUAK isoforms' involvement in crucial biological operations, including mechanistic findings, highlighting how their abnormal functioning contributes to disease progression and quality of life. The third part summarizes the key findings and applications of targeting NUAK isoforms for treating multiple cancers and neurodegenerative disorders. The final part systematically presents a critical review and analysis of the literature on NUAK isoform inhibitions through small molecules.

Association of PRKCA expression and polymorphisms with layer duck eggshell quality

1. Eggshell quality is important for the poultry industry. Calcium is deposited during eggshell formation, and protein kinase C alpha (PRKCA) is involved in transmembrane transport of calcium ions in cells. However, the biological function of PRKCA in poultry is still not understood. Therefore, the aim of this study was to explore the association of mRNA expression and single nucleotide polymorphisms (SNPs) of the PRKCA gene with eggshell quality in laying ducks. 2. The mRNA expression and SNPs of the PRKCA gene were detected by real-time fluorescence quantitative PCR (qRT-PCR) and sequencing of PCR products in 45-week-old female Sansui ducks, which is a high production layer duck breed in China. The association of mRNA expression and SNPs in the PRKCA gene with layer duck eggshell traits was analysed using SPSS (v18.0) software. 3. The results demonstrated that PRKCA mRNA was widely expressed in all examined tissues, and expression was highest in kidney and lowest in the gizzard. Furthermore, the PRKCA mRNA level in uterus was significantly positively correlated with eggshell strength and eggshell weight (P < 0.05). Three novel SNPs, the synonymous mutations of g.9571770 T > C in exon 5, g.9583222 C > T and g.9583227 G > A in exon 7, were found in the PRKCA gene, giving four haplotypes and 10 diplotypes, which affected the mRNA secondary structure and free energy. The g.9583222 C > T and g.9583227 G > A mutations were significantly associated with eggshell strength (P < 0.05). Diplotype H1H1 was advantageous for increasing the strength and thickness of an eggshell. 4. In conclusion, the study showed that the mRNA transcription and genetic variation in the PRKCA gene could significantly affect the strength of duck eggshell and that the PRKCA gene is an important candidate gene for improving eggshell quality in poultry.

Dual targeting of NUAK1 and ULK1 using the multitargeted inhibitor MRT68921 exerts potent antitumor activities

Utilizing oxidative stress has recently been regarded as a potential strategy for tumor therapy. The NUAK family SNF1-like kinase 1 (NUAK1) is a critical component of the antioxidant defense system and is necessary for the survival of tumors. Therefore, NUAK1 is considered an attractive therapeutic target in cancer. However, antioxidant therapy induced elevated ROS levels to activate the Unc-51-like kinase 1 (ULK1) pathway to promote protective autophagy and ULK1-dependent mitophagy. Thus, the combined inhibition of NUAK1 and ULK1 showed a strong synergistic effect in different tumor types. Herein, the potential antitumor activities of a dual NUAK1/ULK1 inhibitor MRT68921 were evaluated in both tumor cell lines and animal models. MRT68921 significantly kills tumor cells by breaking the balance of oxidative stress signals. These results highlight the potential of MRT68921 as an effective agent for tumor therapy.

Cytosolic NUAK1 Enhances ATP Production by Maintaining Proper Glycolysis and Mitochondrial Function in Cancer Cells

NUAK1 is an AMPK-related kinase located in the cytosol and the nucleus, whose expression associates with tumor malignancy and poor patient prognosis in several cancers. Accordingly, NUAK1 was associated with metastasis because it promotes cell migration and invasion in different cancer cells. Besides, NUAK1 supports cancer cell survival under metabolic stress and maintains ATP levels in hepatocarcinoma cells, suggesting a role in energy metabolism in cancer. However, the underlying mechanism for this metabolic function, as well as its link to NUAK1 subcellular localization, is unclear. We demonstrated that cytosolic NUAK1 increases ATP levels, which associates with increased mitochondrial respiration, supporting that cytosolic NUAK1 is involved in mitochondrial function regulation in cancer cells. NUAK1 inhibition led to the formation of “donut-like” structures, providing evidence of NUAK1-dependent mitochondrial morphology regulation. Additionally, our results indicated that cytosolic NUAK1 increases the glycolytic capacity of cancer cells under mitochondrial inhibition. Nuclear NUAK1 seems to be involved in the metabolic switch to glycolysis. Altogether, our results suggest that cytosolic NUAK1 participates in mitochondrial ATP production and the maintenance of proper glycolysis in cancer cells. Our current studies support the role of NUAK1 in bioenergetics, mitochondrial homeostasis, glycolysis and metabolic capacities. They suggest different metabolic outcomes depending on its subcellular localization. The identified roles of NUAK1 in cancer metabolism provide a potential mechanism relevant for tumor progression and its association with poor patient prognosis in several cancers. Further studies could shed light on the molecular mechanisms involved in the identified metabolic NUAK1 functions.

miR-622 is a novel potential biomarker of breast carcinoma and impairs motility of breast cancer cells through targeting NUAK1 kinase

BACKGROUND

Aberrant expression of microRNAs (miR) has been proposed as non-invasive biomarkers for breast cancers. The aim of this study was to analyse the miR-622 level in the plasma and in tissues of breast cancer patients and to explore the role of miR-622 and its target, the NUAK1 kinase, in this context.

METHODS

miR-622 expression was analysed in plasma and in tissues samples of breast cancer patients by q-RT-PCR. Bioinformatics programs, luciferase assay, public dataset analysis and functional experiments were used to uncover the role of miR-622 and its target in breast cancer cells.

RESULTS

miR-622 is downregulated in plasma and in tissues of breast cancer patients respect to healthy controls and its downregulation is significantly associated with advanced grade and high Ki67 level. Modulation of miR-622 affects the motility phenotype of breast cancer cells. NUAK1 kinase is a functional target of miR-622, it is associated with poor clinical outcomes of breast cancer patients and is inversely correlated with miR-622 level.

CONCLUSIONS

miR-622/NUAK1 axis is deregulated in breast cancer patients and affects the motility phenotype of breast cancer cells. Importantly, miR-622 and NUAK1 hold promises as biomarkers and as targets for breast cancers.

Type 3 Inositol 1,4,5-Trisphosphate Receptor Is Increased and Enhances Malignant Properties in Cholangiocarcinoma

Cholangiocarcinoma (CCA) is the second most common malignancy arising in the liver. It carries a poor prognosis, in part because its pathogenesis is not well understood. The type 3 inositol 1,4,5-trisphosphate receptor (ITPR3) is the principal intracellular calcium ion (Ca2+ ) release channel in cholangiocytes, and its increased expression has been related to the pathogenesis of malignancies in other types of tissues, so we investigated its role in CCA. ITPR3 expression was increased in both hilar and intrahepatic CCA samples as well as in CCA cell lines. Deletion of ITPR3 from CCA cells impaired proliferation and cell migration. A bioinformatic analysis suggested that overexpression of ITPR3 in CCA would have a mitochondrial phenotype, so this was also examined. ITPR3 normally is concentrated in a subapical region of endoplasmic reticulum (ER) in cholangiocytes, but both immunogold electron microscopy and super-resolution microscopy showed that ITPR3 in CCA cells was also in regions of ER in close association with mitochondria. Deletion of ITPR3 from these cells impaired mitochondrial Ca2+ signaling and led to cell death. Conclusion: ITPR3 expression in cholangiocytes becomes enhanced in CCA. This contributes to malignant features, including cell proliferation and migration and enhanced mitochondrial Ca2+ signaling.

Localized Inhibition of Protein Phosphatase 1 by NUAK1 Promotes Spliceosome Activity and Reveals a MYC-Sensitive Feedback Control of Transcription

Deregulated expression of MYC induces a dependence on the NUAK1 kinase, but the molecular mechanisms underlying this dependence have not been fully clarified. Here, we show that NUAK1 is a predominantly nuclear protein that associates with a network of nuclear protein phosphatase 1 (PP1) interactors and that PNUTS, a nuclear regulatory subunit of PP1, is phosphorylated by NUAK1. Both NUAK1 and PNUTS associate with the splicing machinery. Inhibition of NUAK1 abolishes chromatin association of PNUTS, reduces spliceosome activity, and suppresses nascent RNA synthesis. Activation of MYC does not bypass the requirement for NUAK1 for spliceosome activity but significantly attenuates transcription inhibition. Consequently, NUAK1 inhibition in MYC-transformed cells induces global accumulation of RNAPII both at the pause site and at the first exon-intron boundary but does not increase mRNA synthesis. We suggest that NUAK1 inhibition in the presence of deregulated MYC traps non-productive RNAPII because of the absence of correctly assembled spliceosomes.

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Nuclear NUAK1 associates with PP1 and phosphorylates its targeting subunit PNUTS

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NUAK1, PP1, and PNUTS form a trimer that associates with the splicing machinery

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Inhibition of NUAK1 reduces spliceosome activity and nascent RNA synthesis

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When MYC is deregulated, NUAK1 inhibition traps RNAPII at the intron-exon boundary

MYC regulates fatty acid metabolism through a multigenic program in claudin-low triple negative breast cancer

Background

Recent studies have suggested that fatty acid oxidation (FAO) is a key metabolic pathway for the growth of triple negative breast cancers (TNBCs), particularly those that have high expression of MYC. However, the underlying mechanism by which MYC promotes FAO remains poorly understood.

Methods

We used a combination of metabolomics, transcriptomics, bioinformatics, and microscopy to elucidate a potential mechanism by which MYC regulates FAO in TNBC.

Results

We propose that MYC induces a multigenic program that involves changes in intracellular calcium signalling and fatty acid metabolism. We determined key roles for fatty acid transporters (CD36), lipases (LPL), and kinases (PDGFRB, CAMKK2, and AMPK) that each contribute to promoting FAO in human mammary epithelial cells that express oncogenic levels of MYC. Bioinformatic analysis further showed that this multigenic program is highly expressed and predicts poor survival in the claudin-low molecular subtype of TNBC, but not other subtypes of TNBCs, suggesting that efforts to target FAO in the clinic may best serve claudin-low TNBC patients.

Conclusion

We identified critical pieces of the FAO machinery that have the potential to be targeted for improved treatment of patients with TNBC, especially the claudin-low molecular subtype.

CX-4945 Induces Methuosis in Cholangiocarcinoma Cell Lines by a CK2-Independent Mechanism

Cholangiocarcinoma is a disease with a poor prognosis and increasing incidence and hence there is a pressing unmet clinical need for new adjuvant treatments. Protein kinase CK2 (previously casein kinase II) is a ubiquitously expressed protein kinase that is up-regulated in multiple cancer cell types. The inhibition of CK2 activity using CX-4945 (Silmitasertib) has been proposed as a novel treatment in multiple disease settings including cholangiocarcinoma. Here, we show that CX-4945 inhibited the proliferation of cholangiocarcinoma cell lines in vitro. Moreover, CX-4945 treatment induced the formation of cytosolic vacuoles in cholangiocarcinoma cell lines and other cancer cell lines. The vacuoles contained extracellular fluid and had neutral pH, features characteristic of methuosis. In contrast, simultaneous knockdown of both the α and α' catalytic subunits of protein kinase CK2 using small interfering RNA (siRNA) had little or no effect on the proliferation of cholangiocarcinoma cell lines and failed to induce the vacuole formation. Surprisingly, low doses of CX-4945 increased the invasive properties of cholangiocarcinoma cells due to an upregulation of matrix metallopeptidase 7 (MMP-7), while the knockdown of CK2 inhibited cell invasion. Our data suggest that CX-4945 inhibits cell proliferation and induces cell death via CK2-independent pathways. Moreover, the increase in cell invasion brought about by CX-4945 treatment suggests that this drug might increase tumor invasion in clinical settings.

Colorectal Tumors Require NUAK1 for Protection from Oxidative Stress

Exploiting oxidative stress has recently emerged as a plausible strategy for treatment of human cancer, and antioxidant defenses are implicated in resistance to chemotherapy and radiotherapy. Targeted suppression of antioxidant defenses could thus broadly improve therapeutic outcomes. Here, we identify the AMPK-related kinase NUAK1 as a key component of the antioxidant stress response pathway and reveal a specific requirement for this role of NUAK1 in colorectal cancer. We show that NUAK1 is activated by oxidative stress and that this activation is required to facilitate nuclear import of the antioxidant master regulator NRF2: Activation of NUAK1 coordinates PP1β inhibition with AKT activation in order to suppress GSK3β-dependent inhibition of NRF2 nuclear import. Deletion of NUAK1 suppresses formation of colorectal tumors, whereas acute depletion of NUAK1 induces regression of preexisting autochthonous tumors. Importantly, elevated expression of NUAK1 in human colorectal cancer is associated with more aggressive disease and reduced overall survival.Significance: This work identifies NUAK1 as a key facilitator of the adaptive antioxidant response that is associated with aggressive disease and worse outcome in human colorectal cancer. Our data suggest that transient NUAK1 inhibition may provide a safe and effective means for treatment of human colorectal cancer via disruption of intrinsic antioxidant defenses. Cancer Discov; 8(5); 632-47. ©2018 AACR.This article is highlighted in the In This Issue feature, p. 517.