PHLPP regulates hexokinase 2-dependent glucose metabolism in colon cancer cells

The Role of HK2 in Tumorigenesis and Development: Potential for Targeted Therapy with Natural Products

Hexokinase 2 (HK2) is widely distributed in various tissues, particularly showing significantly elevated expression levels in tumor tissues. As the initial rate-limiting enzyme in the glycolysis process, HK2 is believed to directly participate in the metabolic reprogramming of tumor cells. This phenomenon, known as the "Warburg effect," provides the energy and substances necessary for the rapid proliferation, growth, and division of tumor cells. Furthermore, by enhancing glycolysis, HK2 exerts its influence on various metabolic pathways in tumor cells, such as pentose phosphate metabolism, glutamine metabolism, serine metabolism, and glycine metabolism, thereby playing a role in the occurrence and development of cancer. Therefore, HK2 represents a promising target for cancer therapy. Simultaneously, natural products with effects on inhibiting the expression or activity of HK2, have already been discovered to exhibit significant anticancer potential. Flavonoids, pentacyclic triterpenoids, phenolic compounds, and lignans constitute the majority of these natural products, directly inhibiting HK2 or indirectly downregulating it through protein kinase B (AKT), hypoxia-inducible factor 1 alpha (HIF-1α), and c-Myc signaling pathways. However, several challenges remain, such as further screening for natural products that directly target and inhibit HK2, optimizing the selection of natural product inhibitors for HK2, and elucidating the molecular mechanisms by which natural products indirectly inhibit HK2. In conclusion, the potential of targeting HK2 for cancer therapy is promising, and with these challenges addressed, natural products inhibiting HK2 will play an even greater role in the fight against cancer.

The PI3K/Akt Pathway and Glucose Metabolism: A Dangerous Liaison in Cancer

Aberrant activation of the PI3K/Akt pathway commonly occurs in cancers and correlates with multiple aspects of malignant progression. In particular, recent evidence suggests that the PI3K/Akt signaling plays a fundamental role in promoting the so-called aerobic glycolysis or Warburg effect, by phosphorylating different nutrient transporters and metabolic enzymes, such as GLUT1, HK2, PFKB3/4 and PKM2, and by regulating various molecular networks and proteins, including mTORC1, GSK3, FOXO transcription factors, MYC and HIF-1α. This leads to a profound reprogramming of cancer metabolism, also impacting on pentose phosphate pathway, mitochondrial oxidative phosphorylation, de novo lipid synthesis and redox homeostasis and thereby allowing the fulfillment of both the catabolic and anabolic demands of tumor cells. The present review discusses the interactions between the PI3K/Akt cascade and its metabolic targets, focusing on their possible therapeutic implications.

PHLPP1 inhibits the growth and aerobic glycolysis activity of human ovarian granular cells through inactivating AKT pathway

BACKGROUND

Polycystic ovary syndrome (PCOS) is a disorder characterized by hyperandrogenism, ovulatory dysfunction, and polycystic ovarian morphologic features, and PCOS is associated with infertility. PH domain Leucine-rich repeat Protein Phosphatase 1 (PHLPP1) has been shown to regulate AKT. The aim of present study is to investigate the role of PHLPP1 in PCOS.

METHODS

The expression levels of PHLPP1 in dihydrotestosterone (DHT)-treated human ovarian granular KGN cells were determined by qRT-PCR and Western blot. PHLPP1 was silenced or overexpressed using lentivirus. Cell proliferation was detected by CCK-8. Apoptosis and ROS generation were analyzed by flow cytometry. Glycolysis was analyzed by measuring extracellular acidification rate (ECAR).

RESULTS

DHT treatment suppressed proliferation, promoted apoptosis, enhanced ROS, and inhibited glycolysis in KGN cells. PHLPP1 silencing alleviated the DHT-induced suppression of proliferation and glycolysis, and promotion of apoptosis and ROS in KGN cells. PHLPP1 regulated cell proliferation and glycolysis in human KGN cells via the AKT signaling pathway.

CONCLUSIONS

Our results showed that PHLPP1 mediates the proliferation and aerobic glycolysis activity of human ovarian granular cells through regulating AKT signaling.

Inhibition of mitochondrial fission activates glycogen synthesis to support cell survival in colon cancer

Metabolic reprogramming has been recognized as one of the major mechanisms that fuel tumor initiation and progression. Our previous studies demonstrate that activation of Drp1 promotes fatty acid oxidation and downstream Wnt signaling. Here we investigate the role of Drp1 in regulating glycogen metabolism in colon cancer. Knockdown of Drp1 decreases mitochondrial respiration without increasing glycolysis. Analysis of cellular metabolites reveals that the levels of glucose-6-phosphate, a precursor for glycogenesis, are significantly elevated whereas pyruvate and other TCA cycle metabolites remain unchanged in Drp1 knockdown cells. Additionally, silencing Drp1 activates AMPK to stimulate the expression glycogen synthase 1 (GYS1) mRNA and promote glycogen storage. Using 3D organoids from Apcf/f/Villin-CreERT2 models, we show that glycogen levels are elevated in tumor organoids upon genetic deletion of Drp1. Similarly, increased GYS1 expression and glycogen accumulation are detected in xenograft tumors derived from Drp1 knockdown colon cancer cells. Functionally, increased glycogen storage provides survival advantage to Drp1 knockdown cells. Co-targeting glycogen phosphorylase-mediated glycogenolysis sensitizes Drp1 knockdown cells to chemotherapy drug treatment. Taken together, our results suggest that Drp1-loss activates glucose uptake and glycogenesis as compensative metabolic pathways to promote cell survival. Combined inhibition of glycogen metabolism may enhance the efficacy of chemotherapeutic agents for colon cancer treatment.

SETD8 promotes glycolysis in colorectal cancer via regulating HIF1α/HK2 axis

Glycolysis is one of the factors influencing cancer cell growth and metastasis. Here, we aimed to investigate the role of SETD8 gene, which is a pro-oncogene. Using bioinformatics tools including Ualcan, Timer, GEPIA, and PrognoScan to study the expression of SETD8 in colorectal cancer, we found that SETD8 expression was higher in colon cancer tissues than that in normal tissues. Higher levels of SETD8 predicted poorer survival of patients. This piqued our interest, so we transfected SETD8 knockdown and overexpression plasmids into colorectal cancer cells and found that SETD8 overexpression enhanced proliferation and glycolysis in colon cancer cells, while SETD8 knockdown decreased cell proliferation and glycolysis. Mechanistically, we examined the expression of HIF1α and HK2 protein by western-blot assay and found that SETD8 activated the HIF1α/HK2 pathway. Then, we treated SETD8-overexpressed cells with HIF1α inhibitor and found that the pro-tumor growth and glycolytic effects of SETD8 were reversed, indicating that SETD8 promoted the growths of colorectal cancer cells by upregulating the HIF1α /HK2 pathway.

Circular RNA circRASSF5 Functions as an Anti-Oncogenic Factor in Hepatocellular Carcinoma by Acting as a Competitive Endogenous RNA Through Sponging miR-331-3p

Objective

Recently, emerging studies have validated that circular RNAs participate in multiple biological progresses in various human malignant tumors, including hepatocellular carcinoma (HCC). However, until now, the elucidated mechanism of circular RNAs is only the tip of the iceberg. In this study, we firstly identify a novel circular RNA circRASSF5 (the only circular RNA derived from the RASSF5 gene), and attempt to investigate its biological function and underlying mechanism in HCC.

Methods

qRT-PCR, Western blotting and IHC were applied to detect the expression of related genes. CCK-8 assay, EdU staining, wound healing and transwell assays were used to investigate HCC proliferation, migration and invasion abilities. Animal model studies were included to investigate the function of circRASSF5 in HCC tumorigenesis and metastasis. RNA pull-down assay, luciferase reporter assay and FISH (fluorescence in situ hybridization) assay were performed to explore the potential biological mechanism underlying circRASSF5 function in HCC.

Results

CircRASSF5 is obviously downregulated in both HCC tissues and cell lines. Low level of circRASSF5 is negatively associated with larger tumor size, severe vascular invasion, more portal vein tumor embolus and unfavorable prognosis. Loss-of-function assay reveals that circRASSF5 remarkably impedes the growth and metastasis of HCC cells in vitro and in vivo. Mechanistically, circRASSF5 directly interacts with miR-331-3p as a sponge, and then enhances the expression of PH domain and leucine-rich repeat protein phosphatase (PHLPP), thus restraining the progression of HCC cells.

Conclusion

Altogether, we validate that circRASSF5 is a tumor suppressor in HCC, which competitively sponges with miR-331-3p and then enhances the tumor inhibitory effect of PHLPP, indicating the potential application value of circRASSF5 for HCC diagnosis and clinical treatment.

Activation of Drp1 promotes fatty acids-induced metabolic reprograming to potentiate Wnt signaling in colon cancer

Cancer cells are known for their ability to adapt variable metabolic programs depending on the availability of specific nutrients. Our previous studies have shown that uptake of fatty acids alters cellular metabolic pathways in colon cancer cells to favor fatty acid oxidation. Here, we show that fatty acids activate Drp1 to promote metabolic plasticity in cancer cells. Uptake of fatty acids (FAs) induces mitochondrial fragmentation by promoting ERK-dependent phosphorylation of Drp1 at the S616 site. This increased phosphorylation of Drp1 enhances its dimerization and interaction with Mitochondrial Fission Factor (MFF) at the mitochondria. Consequently, knockdown of Drp1 or MFF attenuates fatty acid-induced mitochondrial fission. In addition, uptake of fatty acids triggers mitophagy via a Drp1- and p62-dependent mechanism to protect mitochondrial integrity. Moreover, results from metabolic profiling analysis reveal that silencing Drp1 disrupts cellular metabolism and blocks fatty acid-induced metabolic reprograming by inhibiting fatty acid utilization. Functionally, knockdown of Drp1 decreases Wnt/β-catenin signaling by preventing fatty acid oxidation-dependent acetylation of β-catenin. As a result, Drp1 depletion inhibits the formation of tumor organoids in vitro and xenograft tumor growth in vivo. Taken together, our study identifies Drp1 as a key mediator that connects mitochondrial dynamics with fatty acid metabolism and cancer cell signaling.

Mitochondria dysfunction in circulating tumor cells

Circulating tumor cells (CTCs) represent a subset of heterogeneous cells, which, once released from a tumor site, have the potential to give rise to metastasis in secondary sites. Recent research focused on the attempt to detect and characterize these rare cells in the circulation, and advancements in defining their molecular profile have been reported in diverse tumor species, with potential implications for clinical applications. Of note, metabolic alterations, involving mitochondria, have been implicated in the metastatic process, as key determinants in the transition of tumor cells to a mesenchymal or stemness-like phenotype, in drug resistance, and in induction of apoptosis. This review aimed to briefly analyse the most recent knowledge relative to mitochondria dysfunction in CTCs, and to envision implications of altered mitochondria in CTCs for a potential utility in clinics.

The metabolic enzyme hexokinase 2 localizes to the nucleus in AML and normal haematopoietic stem and progenitor cells to maintain stemness

Mitochondrial metabolites regulate leukaemic and normal stem cells by affecting epigenetic marks. How mitochondrial enzymes localize to the nucleus to control stem cell function is less understood. We discovered that the mitochondrial metabolic enzyme hexokinase 2 (HK2) localizes to the nucleus in leukaemic and normal haematopoietic stem cells. Overexpression of nuclear HK2 increases leukaemic stem cell properties and decreases differentiation, whereas selective nuclear HK2 knockdown promotes differentiation and decreases stem cell function. Nuclear HK2 localization is phosphorylation-dependent, requires active import and export, and regulates differentiation independently of its enzymatic activity. HK2 interacts with nuclear proteins regulating chromatin openness, increasing chromatin accessibilities at leukaemic stem cell-positive signature and DNA-repair sites. Nuclear HK2 overexpression decreases double-strand breaks and confers chemoresistance, which may contribute to the mechanism by which leukaemic stem cells resist DNA-damaging agents. Thus, we describe a non-canonical mechanism by which mitochondrial enzymes influence stem cell function independently of their metabolic function.

Thomas, Egan et al. report that hexokinase 2 localizes to the nucleus of leukaemic and normal haematopoietic cells to maintain stemness by interacting with nuclear proteins and modulating chromatin accessibility independently of its kinase activity.

Downregulation of PHLPP induced by endoplasmic reticulum stress promotes eIF2α phosphorylation and chemoresistance in colon cancer

Aberrant activation of endoplasmic reticulum (ER) stress by extrinsic and intrinsic factors contributes to tumorigenesis and resistance to chemotherapies in various cancer types. Our previous studies have shown that the downregulation of PHLPP, a novel family of Ser/Thr protein phosphatases, promotes tumor initiation, and progression. Here we investigated the functional interaction between the ER stress and PHLPP expression in colon cancer. We found that induction of ER stress significantly decreased the expression of PHLPP proteins through a proteasome-dependent mechanism. Knockdown of PHLPP increased the phosphorylation of eIF2α as well as the expression of autophagy-associated genes downstream of the eIF2α/ATF4 signaling pathway. In addition, results from immunoprecipitation experiments showed that PHLPP interacted with eIF2α and this interaction was enhanced by ER stress. Functionally, knockdown of PHLPP improved cell survival under ER stress conditions, whereas overexpression of a degradation-resistant mutant PHLPP1 had the opposite effect. Taken together, our studies identified ER stress as a novel mechanism that triggers PHLPP downregulation; and PHLPP-loss promotes chemoresistance by upregulating the eIF2α/ATF4 signaling axis in colon cancer cells.

Emerging roles of PHLPP phosphatases in metabolism

Over the last decades, research has focused on the role of pleckstrin homology (PH) domain leucine-rich repeat protein phosphatases (PHLPPs) in regulating cellular signaling via PI3K/Akt inhibition. The PKB/Akt signaling imbalances are associated with a variety of illnesses, including various types of cancer, inflammatory response, insulin resistance, and diabetes, demonstrating the relevance of PHLPPs in the prevention of diseases. Furthermore, identification of novel substrates of PHLPPs unveils their role as a critical mediator in various cellular processes. Recently, researchers have explored the increasing complexity of signaling networks involving PHLPPs whereby relevant information of PHLPPs in metabolic diseases was obtained. In this review, we discuss the current knowledge of PHLPPs on the well-known substrates and metabolic regulation, especially in liver, pancreatic beta cell, adipose tissue, and skeletal muscle in relation with the stated diseases. Understanding the context-dependent functions of PHLPPs can lead to a promising treatment strategy for several kinds of metabolic diseases.

Pleckstrin homology (PH) domain and Leucine Rich Repeat Phosphatase 1 (Phlpp1) Suppresses Parathyroid Hormone Receptor 1 (Pth1r) Expression and Signaling During Bone Growth

Endochondral ossification is tightly controlled by a coordinated network of signaling cascades including parathyroid hormone (PTH). Pleckstrin homology (PH) domain and leucine rich repeat phosphatase 1 (Phlpp1) affects endochondral ossification by suppressing chondrocyte proliferation in the growth plate, longitudinal bone growth, and bone mineralization. As such, Phlpp1-/- mice have shorter long bones, thicker growth plates, and proportionally larger growth plate proliferative zones. The goal of this study was to determine how Phlpp1 deficiency affects PTH signaling during bone growth. Transcriptomic analysis revealed greater PTH receptor 1 (Pth1r) expression and enrichment of histone 3 lysine 27 acetylation (H3K27ac) at the Pth1r promoter in Phlpp1-deficient chondrocytes. PTH (1-34) enhanced and PTH (7-34) attenuated cell proliferation, cAMP signaling, cAMP response element-binding protein (CREB) phosphorylation, and cell metabolic activity in Phlpp1-inhibited chondrocytes. To understand the role of Pth1r action in the endochondral phenotypes of Phlpp1-deficient mice, Phlpp1-/- mice were injected with Pth1r ligand PTH (7-34) daily for the first 4 weeks of life. PTH (7-34) reversed the abnormal growth plate and long-bone growth phenotypes of Phlpp1-/- mice but did not rescue deficits in bone mineral density or trabecular number. These results show that elevated Pth1r expression and signaling contributes to increased proliferation in Phlpp1-/- chondrocytes and shorter bones in Phlpp1-deficient mice. Our data reveal a novel molecular relationship between Phlpp1 and Pth1r in chondrocytes during growth plate development and longitudinal bone growth. © 2021 American Society for Bone and Mineral Research (ASBMR).

Hexokinase 2 in Cancer: A Prima Donna Playing Multiple Characters

Hexokinases are a family of ubiquitous exose-phosphorylating enzymes that prime glucose for intracellular utilization. Hexokinase 2 (HK2) is the most active isozyme of the family, mainly expressed in insulin-sensitive tissues. HK2 induction in most neoplastic cells contributes to their metabolic rewiring towards aerobic glycolysis, and its genetic ablation inhibits malignant growth in mouse models. HK2 can dock to mitochondria, where it performs additional functions in autophagy regulation and cell death inhibition that are independent of its enzymatic activity. The recent definition of HK2 localization to contact points between mitochondria and endoplasmic reticulum called Mitochondria Associated Membranes (MAMs) has unveiled a novel HK2 role in regulating intracellular Ca²⁺ fluxes. Here, we propose that HK2 localization in MAMs of tumor cells is key in sustaining neoplastic progression, as it acts as an intersection node between metabolic and survival pathways. Disrupting these functions by targeting HK2 subcellular localization can constitute a promising anti-tumor strategy.

Upregulation of CPT1A is essential for the tumor-promoting effect of adipocytes in colon cancer

Colon tumors grow in an adipose tissue-enriched microenvironment. Locally advanced colon cancers often invade into surrounding adipose tissue with a direct contact with adipocytes. We have previously shown that adipocytes promote tumor growth by modulating cellular metabolism. Here we demonstrate that carnitine palmitoyltransferase I (CPT1A), a key enzyme controlling fatty acid oxidation (FAO), was upregulated in colon cancer cells upon exposure to adipocytes or fatty acids. In addition, CPT1A expression was increased in invasive tumor cells within the adipose tissue compared to tumors without direct contact with adipocytes. Silencing CPT1A abolished the protective effect provided by fatty acids against nutrient deprivation and reduced tumor organoid formation in 3D culture and the expression of genes associated with cancer stem cells downstream of Wnt/β-catenin. Mechanistically, CPT1A-dependent FAO promoted the acetylation and nuclear translocation of β-catenin. Furthermore, knockdown of CPT1A blocked the tumor-promoting effect of adipocytes in vivo and inhibited xenograft tumor initiation. Taken together, our findings identify CPT1A-depedent FAO as an essential metabolic pathway that enables the interaction between adipocytes and colon cancer cells.

Regulatory Role of Hexokinase 2 in Modulating Head and Neck Tumorigenesis

To support great demand of cell growth, cancer cells preferentially obtain energy and biomacromolecules by glycolysis over mitochondrial oxidative phosphorylation (OxPhos). Among all glycolytic enzymes, hexokinase (HK), a rate-limiting enzyme at the first step of glycolysis to catalyze cellular glucose into glucose-6-phosphate, is herein emphasized. Four HK isoforms, HK1-HK4, were discovered in nature. It was shown that HK2 expression is enriched in many tumor cells and correlated with poorer survival rates in most neoplastic cells. HK2-mediated regulations for cell malignancy and mechanistic cues in regulating head and neck tumorigenesis, however, are not fully elucidated. Cellular malignancy index, such as cell growth, cellular motility, and treatment sensitivity, and molecular alterations were determined in HK2-deficient head and neck squamous cell carcinoma (HNSCC) cells. By using various cancer databases, HK2, but not HK1, positively correlates with HNSCC progression in a stage-dependent manner. A high HK2 expression was detected in head and neck cancerous tissues compared with their normal counterparts, both in mouse and human subjects. Loss of HK2 in HNSCC cells resulted in reduced cell (in vitro) and tumor (in vivo) growth, as well as decreased epithelial-mesenchymal transition–mediated cell movement; in contrast, HK2-deficient HNSCC cells exhibited greater sensitivity to chemotherapeutic drugs cisplatin and 5-fluorouracil but are more resistant to photodynamic therapy, indicating that HK2 expression could selectively define treatment sensitivity in HNSCC cells. At the molecular level, it was found that HK2 alteration drove metabolic reprogramming toward OxPhos and modulated oncogenic Akt and mutant TP53-mediated signals in HNSCC cells. In summary, the present study showed that HK2 suppression could lessen HNSCC oncogenicity and modulate therapeutic sensitivity, thereby being an ideal therapeutic target for HNSCCs.

Hepatic exosome-derived miR-130a-3p attenuates glucose intolerance via suppressing PHLPP2 gene in adipocyte

OBJECTIVE

Glucose and lipid metabolism disorders are a major risk factor for type II diabetes and cardiovascular diseases. Evidence has indicated that the interplay between the liver and adipose tissue is crucial in maintaining energy homeostasis. Recently, the interaction between two distant endocrine organs mainly focuses on the regulation of hormones and receptors. However, as a novel carrier in the inter-tissue communication, exosomes plays a role in liver-fat crosstalk, but its effects on glucose and lipid metabolisms are still unclear. In this study, we sought to investigate the effects of hepatic exosome-derived miR-130a-3p in the regulation of glucose/lipid metabolism in adipose tissues.

MEASURE

In vivo, we constructed generalized miR-130a-3p knockout (130KO) and overexpressed (130OE) mice. Wild type (WT), 130KO and 130OE mice (n = 10) were assigned to a randomized controlled trial and were fed diets with either 10% (standard diet, SD) or 60% (high-fat diet, HFD) of total calories from fat (lard). Next, hepatic exosomes were extracted from WT-SD, 130KO-SD and 130OE-SD mice (WT-EXO, KO-EXO, OE-EXO), and 130KO mice were injected with 100 mg hepatic exosomes of different sources via tail-vein (once every 48 h) for 28 days, fed with HFD. In vitro, 3T3-L1 cells were treated with miR-130a-3p mimics, inhibitor and hepatic exosomes. Growth performance and glucose and lipid metabolic profiles were examined.

RESULTS

After feeding with HFD, the weights of 130KO mice were markedly higher than WT mice. Over-expression of miR-130a-3p in 130OE mice and intravenous injection of 130OE-EXO in 130KO mice contributed to a positive correlation with the recovery of insulin resistance. In addition, miR-130a-3p mimics and 130OE-EXO treatment of 3T3-L1 cells exhibited decreasing generations of lipid droplets and increasing glucose uptake. Conversely, inhibition of miR-130a-3p in vitro and in vivo resulted in opposite phenotype changes. Furthermore, PHLPP2 was identified as a direct target of miR-130a-3p, and the hepatic exosome-derived miR-130a-3p could improve glucose intolerance via suppressing PHLPP2 to activate AKT-AS160-GLUT4 signaling pathway in adipocytes.

CONCLUSIONS

We demonstrated that hepatic exosome-derived miR-130a regulated energy metabolism in adipose tissues, and elucidated a new molecular mechanism that hepatic exosome-derived miR-130a-3p is a crucial participant in organismic energy homeostasis through mediating crosstalk between the liver and adipose tissues.

Shear stress activates ATOH8 via autocrine VEGF promoting glycolysis dependent-survival of colorectal cancer cells in the circulation

Background

Metastasis and recurrence, wherein circulating tumour cells (CTCs) play an important role, are the leading causes of death in colorectal cancer (CRC). Metastasis-initiating CTCs manage to maintain intravascular survival under anoikis, immune attack, and importantly shear stress; however, the underlying mechanisms remain poorly understood.

Methods

In view of the scarcity of CTCs in the bloodstream, suspended colorectal cancer cells were flowed into the cyclic laminar shear stress (LSS) according to previous studies. Then, we detected these suspended cells with a CK8+/CD45−/DAPI+ phenotype and named them mimic circulating tumour cells (m-CTCs) for subsequent CTCs related researches. Quantitative polymerase chain reaction, western blotting, and immunofluorescence were utilised to analyse gene expression change of m-CTCs sensitive to LSS stimulation. Additionally, we examined atonal bHLH transcription factor 8 (ATOH8) expressions in CTCs among 156 CRC patients and mice by fluorescence in situ hybridisation and flow cytometry. The pro-metabolic and pro-survival functions of ATOH8 were determined by glycolysis assay, live/dead cell vitality assay, anoikis assay, and immunohistochemistry. Further, the concrete up-and-down mechanisms of m-CTC survival promotion by ATOH8 were explored.

Results

The m-CTCs actively responded to LSS by triggering the expression of ATOH8, a fluid mechanosensor, with executive roles in intravascular survival and metabolism plasticity. Specifically, ATOH8 was upregulated via activation of VEGFR2/AKT signalling pathway mediated by LSS induced VEGF release. ATOH8 then transcriptionally activated HK2-mediated glycolysis, thus promoting the intravascular survival of colorectal cancer cells in the circulation.

Conclusions

This study elucidates a novel mechanism that an LSS triggered VEGF-VEGFR2-AKT-ATOH8 signal axis mediates m-CTCs survival, thus providing a potential target for the prevention and treatment of hematogenous metastasis in CRC.

Identification of Potential Biomarkers with Diagnostic Value in Pituitary Adenomas Using Prediction Analysis for Microarrays Method

Pituitary adenomas are the most common intrasellar tumors. Patients should be identified at an early stage so that effective treatment can be implemented. The study aims at detecting the potential biomarkers with diagnostic value of pituitary adenomas. Using a total of seven gene expression profiles (GEPs) of the datasets from the Gene Expression Omnibus (GEO) database, we first screened 1980 significant differentially expressed genes (DEGs). Then, we employed the prediction analysis for microarray (PAM) algorithm to identify 340 significant DEGs able to differ pituitary tumor from normal samples, which include 208 upregulated DEGs and 132 downregulated DEGs. DAVID database was used to carry out the enrichment analysis on Kyoto Encyclopedia of Genes and Genomes (KEGG) and Gene Ontology (GO) pathways. We found that upregulated candidates were enriched in protein folding and metabolic pathways. Downregulated DEGs saw a significant enrichment in insulin receptor signaling pathway and hedgehog signaling pathway. Based on the protein-protein interaction (PPI) network as well as module analysis, we determined ten hub genes including PHLPP, ENO2, ACTR1A, EHHADH, EHMT2, FOXO1, DLD, CCT2, CSNK1D, and CETN2 that could be potential biomarkers with diagnostic value in pituitary adenomas. In conclusion, the study contributes to reliable and potential molecular biomarkers with diagnostic value. Moreover, these potential biomarkers may be used for prognosis and new therapeutic targets for the pituitary adenomas.

S100A4 alters metabolism and promotes invasion of lung cancer cells by up-regulating mitochondrial complex I protein NDUFS2

It is generally accepted that alterations in metabolism are critical for the metastatic process; however, the mechanisms by which these metabolic changes are controlled by the major drivers of the metastatic process remain elusive. Here, we found that S100 calcium-binding protein A4 (S100A4), a major metastasis-promoting protein, confers metabolic plasticity to drive tumor invasion and metastasis of non-small cell lung cancer cells. Investigating how S100A4 regulates metabolism, we found that S100A4 depletion decreases oxygen consumption rates, mitochondrial activity, and ATP production and also shifts cell metabolism to higher glycolytic activity. We further identified that the 49-kDa mitochondrial complex I subunit NADH dehydrogenase (ubiquinone) Fe-S protein 2 (NDUFS2) is regulated in an S100A4-dependent manner and that S100A4 and NDUFS2 exhibit co-occurrence at significant levels in various cancer types as determined by database-driven analysis of genomes in clinical samples using cBioPortal for Cancer Genomics. Importantly, we noted that S100A4 or NDUFS2 silencing inhibits mitochondrial complex I activity, reduces cellular ATP level, decreases invasive capacity in three-dimensional growth, and dramatically decreases metastasis rates as well as tumor growth in vivo Finally, we provide evidence that cells depleted in S100A4 or NDUFS2 shift their metabolism toward glycolysis by up-regulating hexokinase expression and that suppressing S100A4 signaling sensitizes lung cancer cells to glycolysis inhibition. Our findings uncover a novel S100A4 function and highlight its importance in controlling NDUFS2 expression to regulate the plasticity of mitochondrial metabolism and thereby promote the invasive and metastatic capacity in lung cancer.

The mitochondrial retrograde signaling regulates Wnt signaling to promote tumorigenesis in colon cancer

Cancer cells are known to upregulate aerobic glycolysis to promote growth, proliferation, and survival. However, the role of mitochondrial respiration in tumorigenesis remains elusive. Here we report that inhibition of mitochondrial function by silencing TFAM, a key transcription factor essential for mitochondrial DNA (mtDNA) replication and the transcription of mtDNA-encoded genes, markedly reduced tumor-initiating potential of colon cancer cells. Knockdown of TFAM significantly decreased mitochondrial respiration in colon cancer cells; however, the cellular levels of ATP remained largely unchanged as a result of increased glycolysis. This metabolic alteration rendered cancer cells highly susceptible to glucose deprivation. Interestingly, upregulation of glycolysis was independent of hypoxia-inducible factor-1 (HIF1) as TFAM knockdown cells fail to stabilize HIF1α under hypoxic conditions. Moreover, knockdown of TFAM results in decreased expression of genes-associated cancer stem cells downstream of Wnt/β-catenin signaling. Metabolic analysis reveals that the level of α-ketoglutarate (α-KG) was significantly upregulated in TFAM knockout cells. Silencing of prolyl hydroxylase domain-containing protein 2 (PHD2), a α-KG-dependent dioxyenase, rescued the expression of target genes of both HIF1α and Wnt/β-catenin. Furthermore, intestinal-specific knockout of TFAM prevents tumor formation in Apc-mutant mouse models of colon cancer. Taken together, our findings identify a novel role of mitochondria-mediated retrograde signaling in regulating Wnt signaling and tumor initiation in colon cancer.

PIM2-mediated phosphorylation of hexokinase 2 is critical for tumor growth and paclitaxel resistance in breast cancer

Hexokinase-II (HK2) is a key enzyme involved in glycolysis, which is required for breast cancer progression. However, the underlying post-translational mechanisms of HK2 activity are poorly understood. Here, we showed that Proviral Insertion in Murine Lymphomas 2 (PIM2) directly bound to HK2 and phosphorylated HK2 on Thr473. Biochemical analyses demonstrated that phosphorylated HK2 Thr473 promoted its protein stability through the chaperone-mediated autophagy (CMA) pathway, and the levels of PIM2 and pThr473-HK2 proteins were positively correlated with each other in human breast cancer. Furthermore, phosphorylation of HK2 on Thr473 increased HK2 enzyme activity and glycolysis, and enhanced glucose starvation-induced autophagy. As a result, phosphorylated HK2 Thr473 promoted breast cancer cell growth in vitro and in vivo. Interestingly, PIM2 kinase inhibitor SMI-4a could abrogate the effects of phosphorylated HK2 Thr473 on paclitaxel resistance in vitro and in vivo. Taken together, our findings indicated that PIM2 was a novel regulator of HK2, and suggested a new strategy to treat breast cancer.

B cell lymphoma with different metabolic characteristics show distinct sensitivities to metabolic inhibitors

Purpose: Cancer cells exhibit profound alterations in their metabolism (abnormal glucose and glutamine metabolism). Targeting cancer metabolism is a promising therapeutic strategy. Lymphoma can be classified into many different types and it is very complicated. Therefore, in this paper, we want to know whether the B cell lymphoma cells with different metabolic characteristics have distinct sensitivities to metabolic inhibitors. Methods: We classified 9 B cell lymphoma cell lines into different metabolic subtypes according to the dependency on glutamine and glucose. Then we detected the OCR, ECAR, glucose consumption and lactate production, mitochondrial content and growth rate. And we also determined the IC50 of these 9 cell lines to metabolic inhibitors. Results: According to the dependency on glutamine and glucose, we successfully classified three distinct metabolic subtypes in B cell lymphoma cell lines, one subtype was defined glutamine and glucose equally utilized subtype (GLN=Glu), whereas the other two subtypes were GLN-addicted and Glu-dependent. And these three subtypes showed striking differences in glucose and glutamine utilization, glycolysis and mitochondrial function, and proliferation rate. GLN-addicted and Glu-dependence subtypes also showed differences in cell sensitivity to inhibitors of glutamine and glycolysis metabolism, respectively. However, GLN=Glu subtype seems minimal sensitive to glycolytic and glutaminolytic inhibitors, and with high proliferation rate. Conclusions: The cells rely more on glucose/gltamine have a stronger sensitivity to glucose/glutamine depletion or glycolysis/ glutaminolysis inhibition and a lessened sensitivity to glutaminolysis/glycolysis inhibitors. To target tumor metabolism based on metabolic characteristics may provide a new therapeutic strategy for the treatment of B cell lymphoma.

Tumor suppressive protein phosphatases in human cancer: Emerging targets for therapeutic intervention and tumor stratification

Aberrant protein phosphorylation is one of the hallmarks of cancer cells, and in many cases a prerequisite to sustain tumor development and progression. Like protein kinases, protein phosphatases are key regulators of cell signaling. However, their contribution to aberrant signaling in cancer cells is overall less well appreciated, and therefore, their clinical potential remains largely unexploited. In this review, we provide an overview of tumor suppressive protein phosphatases in human cancer. Along their mechanisms of inactivation in defined cancer contexts, we give an overview of their functional roles in diverse signaling pathways that contribute to their tumor suppressive abilities. Finally, we discuss their emerging roles as predictive or prognostic markers, their potential as synthetic lethality targets, and the current feasibility of their reactivation with pharmacologic compounds as promising new cancer therapies. We conclude that their inclusion in clinical practice has obvious potential to significantly improve therapeutic outcome in various ways, and should now definitely be pushed forward.

PHLPP: a putative cellular target during insulin resistance and type 2 diabetes

Progressive research in the past decade converges to the impact of PHLPP in regulating the cellular metabolism through PI3K/AKT inhibition. Aberrations in PKB/AKT signaling coordinates with impaired insulin secretion and insulin resistance, identified during T2D, obesity and cardiovascular disorders which brings in the relevance of PHLPPs in the metabolic paradigm. In this review, we discuss the impact of PHLPP isoforms in insulin signaling and its associated cellular events including mitochondrial dysfunction, DNA damage, autophagy and cell death. The article highlights the plausible molecular targets that share the role during insulin-resistant states, whose understanding can be extended into treatment responses to facilitate targeted drug discovery for T2D and allied metabolic syndromes.