Phosphoinositide 3-kinase-related overgrowth: cellular phenotype and future therapeutic options

TECRL deficiency results in aberrant mitochondrial function in cardiomyocytes

Sudden cardiac death (SCD) caused by ventricular arrhythmias is the leading cause of mortality of cardiovascular disease. Mutation in TECRL, an endoplasmic reticulum protein, was first reported in catecholaminergic polymorphic ventricular tachycardia during which a patient succumbed to SCD. Using loss- and gain-of-function approaches, we investigated the role of TECRL in murine and human cardiomyocytes. Tecrl (knockout, KO) mouse shows significantly aggravated cardiac dysfunction, evidenced by the decrease of ejection fraction and fractional shortening. Mechanistically, TECRL deficiency impairs mitochondrial respiration, which is characterized by reduced adenosine triphosphate production, increased fatty acid synthase (FAS) and reactive oxygen species production, along with decreased MFN2, p-AKT (Ser473), and NRF2 expressions. Overexpression of TECRL induces mitochondrial respiration, in PI3K/AKT dependent manner. TECRL regulates mitochondrial function mainly through PI3K/AKT signaling and the mitochondrial fusion protein MFN2. Apoptosis inducing factor (AIF) and cytochrome C (Cyc) is released from the mitochondria into the cytoplasm after siTECRL infection, as demonstrated by immunofluorescent staining and western blotting. Herein, we propose a previously unrecognized TECRL mechanism in regulating CPVT and may provide possible support for therapeutic target in CPVT.

The endoplasmic reticulum protein TECRL promotes mitochondrial function in cardiomyocytes and its knockout in mice leads to cardiac dysfunction, decreased mitochondria function, and elevated levels of reactive oxygen species.

ZIP10 is a negative determinant for anti-tumor effect of mannose in thyroid cancer by activating phosphate mannose isomerase

Background

Mannose, a natural hexose existing in daily food, has been demonstrated to preferentially inhibit the progression of tumors with low expression of phosphate mannose isomerase (PMI). However, its function in thyroid cancer still remains elusive.

Methods

MTT, colony formation and flow cytometry assays were performed to determine the response of thyroid cancer cells to mannose. Meanwhile, mouse models of subcutaneous xenograft and primary papillary thyroid cancer were established to determine in vivo anti-tumor activity of mannose. The underlying mechanism of mannose selectively killing thyroid cancer cells was clarified by a series of molecular and biochemical experiments.

Results

Our data demonstrated that mannose selectively suppressed the growth of thyroid cancer cells, and found that enzyme activity of PMI rather than its protein expression was negatively associated with the response of thyroid cancer cells to mannose. Besides, our data showed that zinc ion (Zn²⁺) chelator TPEN clearly increased the response of mannose-insensitive cells to mannose by inhibiting enzyme activity of PMI, while Zn²⁺ supplement could effectively reverse this effect. Further studies found that the expression of zinc transport protein ZIP10, which transport Zn²⁺ from extracellular area into cells, was negatively related to the response of thyroid cancer cells to mannose. Knocking down ZIP10 in mannose-insensitive cells significantly inhibited in vitro and in vivo growth of these cells by decreasing intracellular Zn²⁺ concentration and enzyme activity of PMI. Moreover, ectopic expression of ZIP10 in mannose-sensitive cells decrease their cellular response to mannose. Mechanistically, mannose exerted its anti-tumor effect by inhibiting cellular glycolysis; however, this effect was highly dependent on expression status of ZIP10.

Conclusion

The present study demonstrate that mannose selectively kills thyroid cancer cells dependent on enzyme activity of PMI rather than its expression, and provide a mechanistic rationale for exploring clinical use of mannose in thyroid cancer therapy.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13046-021-02195-z.

Everolimus regulates the activity of gemcitabine-resistant pancreatic cancer cells by targeting the Warburg effect via PI3K/AKT/mTOR signaling

BACKGROUND

Gemcitabine (GEM) resistance remains a significant clinical challenge in pancreatic cancer treatment. Here, we investigated the therapeutic utility of everolimus (Evr), an inhibitor of mammalian target of rapamycin (mTOR), in targeting the Warburg effect to overcome GEM resistance in pancreatic cancer.

METHODS

The effect of Evr and/or mTOR overexpression or GEM on cell viability, migration, apoptosis, and glucose metabolism (Warburg effect) was evaluated in GEM-sensitive (GEMsen) and GEM-resistant (GEMres) pancreatic cancer cells.

RESULTS

We demonstrated that the upregulation of mTOR enhanced cell viability and favored the Warburg effect in pancreatic cancer cells via the regulation of PI3K/AKT/mTOR signaling. However, this effect was counteracted by Evr, which inhibited aerobic glycolysis by reducing the levels of glucose, lactic acid, and adenosine triphosphate and suppressing the expression of glucose transporter 1, lactate dehydrogenase-B, hexokinase 2, and pyruvate kinase M2 in GEMsen and GEMres cells. Evr also promoted apoptosis by upregulating the pro-apoptotic proteins Bax and cytochrome-c and downregulating the anti-apoptotic protein Bcl-2. GEM was minimally effective in suppressing GEMres cell activity, but the therapeutic effectiveness of Evr against pancreatic cancer growth was greater in GEMres cells than that in GEMsen cells. In vivo studies confirmed that while GEM failed to inhibit the progression of GEMres tumors, Evr significantly decreased the volume of GEMres tumors while suppressing tumor cell proliferation and enhancing tumor apoptosis in the presence of GEM.

CONCLUSIONS

Evr treatment may be a promising strategy to target the growth and activity of GEM-resistant pancreatic cancer cells by regulating glucose metabolism via inactivation of PI3K/AKT/mTOR signaling.

Clinical and neuroimaging findings in 33 patients with MCAP syndrome: A survey to evaluate relevant endpoints for future clinical trials

Megalencephaly-CApillary malformation-Polymicrogyria (MCAP) syndrome results from somatic mosaic gain-of-function variants in PIK3CA. Main features are macrocephaly, somatic overgrowth, cutaneous vascular malformations, connective tissue dysplasia, neurodevelopmental delay, and brain anomalies. The objectives of this study were to describe the clinical and radiological features of MCAP, to suggest relevant clinical endpoints applicable in future trials of targeted drug therapy. Based on a French collaboration, we collected clinical features of 33 patients (21 females, 12 males, median age of 9.9 years) with MCAP carrying mosaic PIK3CA pathogenic variants. MRI images were reviewed for 21 patients. The main clinical features reported were macrocephaly at birth (20/31), postnatal macrocephaly (31/32), body/facial asymmetry (21/33), cutaneous capillary malformations (naevus flammeus 28/33, cutis marmorata 17/33). Intellectual disability was present in 15 patients. Among the MRI images reviewed, the neuroimaging findings were megalencephaly (20/21), thickening of corpus callosum (16/21), Chiari malformation (12/21), ventriculomegaly/hydrocephaly (10/21), cerebral asymmetry (6/21) and polymicrogyria (2/21). This study confirms the main known clinical features that defines MCAP syndrome. Taking into account the phenotypic heterogeneity in MCAP patients, in the context of emerging clinical trials, we suggest that patients should be evaluated based on the main neurocognitive expression on each patient.

Neutralization of HSF1 in cells from PIK3CA-related overgrowth spectrum patients blocks abnormal proliferation

PIK3CA-related overgrowth spectrum is caused by mosaicism mutations in the PIK3CA gene. These mutations, which are also observed in various types of cancer, lead to a constitutive activation of the PI3K/AKT/mTOR pathway, increasing cell proliferation. Heat shock transcription factor 1 (HSF1) is the major stress-responsive transcription factor. Recent findings indicate that AKT phosphorylates and activates HSF1 independently of heat-shock in breast cancer cells. Here, we aimed to investigate the role of HSF1 in PIK3CA-related overgrowth spectrum. We observed a higher rate of proliferation and increased phosphorylation of AKT and p70S6K in mutant fibroblasts than in control cells. We also found elevated phosphorylation and activation of HSF1, which is directly correlated to AKT activation. Specific AKT inhibitors inhibit HSF1 phosphorylation as well as HSF1-dependent gene transcription. Finally, we demonstrated that targeting HSF1 with specific inhibitors reduced the proliferation of mutant cells. As there is currently no curative treatment for PIK3CA-related overgrowth spectrum, our results identify HSF1 as a new potential therapeutic target.

[Recombinant methioninase regulates PI3K/Akt/Glut-1 pathway and inhibits aerobic glycolysis to promote apoptosis of gastric cancer cells]

OBJECTIVE

To investigate the molecular mechanism of recombinant methioninase (rMETase) in promoting apoptosis of gastric cancer cells.

METHODS

Gastric cancer SGC-7901 cells were treated with rMETase (final concentration of 1.25 and 2.50 mmmol/L) for 72 h, and the changes in the cell viability were detected using CCK-8 method and the cell morphology changes were observed under an inverted microscope. Plate colony formation assay was used to evaluate colony formation ability of the cells, and flow cytometry was performed to analyze the changes in cell apoptosis and cell cycles. Glucose and lactate levels in the culture medium were determined using a colorimetric method and ATP concentration was detected using a fluorescence microplate reader; Western blotting was used to assess the effect of rMETase on PI3K/Akt pathway, glucose transporter-1 (GLUT-1), glycolysis- related proteins and apoptotic proteins in SGC-7901 cells.

RESULTS

rMETase significantly inhibited the proliferation and clonal formation, promoted cell apoptosis, and induced cell cycle arrest in S phase in SGC-7901 cells (P < 0.05). With the increase of rMETase concentration, the cells showed obviously decreased glucose intake accompanied by decreased glycolysis and ATP concentration (P < 0.001). The results of Western blotting showed that the expressions of PI3K, p-Akt/t-Akt, GLUT-1, and the key glycolytic enzymes HK2, PFKM, LDHA, antiapoptosis protein Bcl-2 were all downregulated and the pro-apoptotic proteins Bax and caspase-3 were up-regulated in response to rMETase treatment in SGC-7901 cells (P < 0.01).

CONCLUSIONS

rMETase can inhibit aerobic glycolysis, induce apoptosis and inhibit the proliferation of SGC-7901 cells by inhibiting the activity of PI3K/Akt/GLUT-1 pathway, suggesting its potential as a therapeutic agent for gastric cancer.

Impact of the Activation Status of the Akt/mTOR Signalling Pathway on the Clinical Behaviour of Synovial Sarcoma: Retrospective Analysis of 174 Patients at a Single Institution

PURPOSE

Phosphoinositide 3-kinase (PI3K) and the downstream Akt/mammalian target of rapamycin (mTOR) pathway are central to the control of cell proliferation and survival. Although abnormal activation of this pathway has been well established in a variety of tumours, limited studies are available on synovial sarcoma. The aim of this study was to investigate the expression of several key proteins of those pathways in synovial sarcomas and to correlate the expression of these proteins with clinicopathologic features and prognosis.

PATIENTS AND METHODS

A total of 174 patients with synovial sarcomas were recruited for this study. The phosphorylation status of Akt, mTOR, and eukaryotic translation initiation factor 4E binding protein (4E-BP1) was measured by immunohistochemistry assays in formalin-fixed, paraffin-embedded samples. Correlations between the expression levels of these proteins and clinicopathologic features and prognosis were analysed.

RESULTS

The positive rates of phosphorylated (p)Akt, pmTOR, p4E-BP1, and CyclinD1 were 62.7%, 55.6%, 47.1%, and 52.6%, respectively. The positive results of pmTOR, pAkt, and downstream p4E-BP1 were correlated with each other. The positive pAkt, pmTOR, p4E-BP1, and CyclinD1 results were more highly expressed in head and neck and visceral tumours, and positive p4E-BP1 results were correlated with larger size and larger areas of necrosis. In multivariate analysis of clinicopathologic factors, head and neck and visceral location, large tumour size, larger areas of necrosis and frequent mitosis were confirmed as risk factors for shorter overall survival. Positive pAkt, pmTOR and p4E-BP1 results were correlated significantly with shorter overall survival, and CyclinD1 was not in the univariate analysis. The positive pmTOR, pAkt, p4E-BP1, and CyclinD1 results were significantly poor prognostic factors for overall survival, and only positive p4E-BP1 results were significantly associated with shorter event-free survival in multivariate analysis.

CONCLUSION

This study demonstrated the high expression of pAkt, pmTOR, and p4E-BP1 associated with aggressive clinical behaviour in synovial sarcomas and provided evidence for prognostic evaluation and targeted therapy.

MFN2 silencing promotes neural differentiation of embryonic stem cells via the Akt signaling pathway

Mitofusin 2 (MFN2) is a regulatory protein participating in mitochondria dynamics, cell proliferation, death, differentiation, and so on. This study aims at revealing the functional role of MFN2 in the pluripotency maintenance and primitive differetiation of embryonic stem cell (ESCs). A dox inducible silencing and routine overexpressing approach was used to downregulate and upregulate MFN2 expression, respectively. We have compared the morphology, cell proliferation, and expression level of pluripotent genes in various groups. We also used directed differentiation methods to test the differentiation capacity of various groups. The Akt signaling pathway was explored by the western blot assay. MFN2 upregulation in ESCs exhibited a typical cell morphology and similar cell proliferation, but decreased pluripotent gene markers. In addition, MFN2 overexpression inhibited ESCs differentiation into the mesendoderm, while MFN2 silencing ESCs exhibited a normal cell morphology, slower cell proliferation and elevated pluripotency markers. For differentiation, MFN2 silencing ESCs exhibited enhanced three germs' differentiation ability. Moreover, the protein levels of phosphorylated Akt308 and Akt473 decreased in MFN2 silenced ESCs, and recovered in the neural differentiation process. When treated with the Akt inhibitor, the neural differentiation capacity of the MFN2 silenced ESCs can reverse to a normal level. Taken together, the data indicated that the appropriate level of MFN2 expression is essential for pluripotency and differentiation capacity in ESCs. The increased neural differentiation ability by MFN2 silencing is strongly related to the Akt signaling pathway.

Acrylamide induces HepG2 cell proliferation through upregulation of miR-21 expression

Acrylamide, a potential carcinogen, exists in carbohydrate-rich foods cooked at a high temperature. It has been reported that acrylamide can cause DNA damage and cytotoxicity. The present study aimed to investigate the potential mechanism of human hepatocarcinoma HepG2 cell proliferation induced by acrylamide and to explore the antagonistic effects of a natural polyphenol curcumin against acrylamide via miR-21. The results indicated that acrylamide (≤100 μmol/L) significantly increased HepG2 cell proliferation and miR-21 expression. In addition, acrylamide reduced the PTEN expression in protein level, while induced the expressions of p-AKT, EGFR and cyclin D1. The PI3K/AKT inhibitor decreased p-AKT protein expression and inhibited the proliferation of HepG2 cells. In addition, curcumin effectively reduced acrylamide-induced HepG2 cell proliferation and induced apoptosis through the expression of miR-21. In conclusion, the results showed that acrylamide increased HepG2 cell proliferation via upregulating miR-21 expression, which may be a new target for the treatment and prevention of cancer.

Electrical Stimulation Activates Fibroblasts through the Elevation of Intracellular Free Ca2+: Potential Mechanism of Pelvic Electrical Stimulation Therapy

Ca²⁺ is an important ion in response to electrical stimulation (ES) and acts as second messenger in the regulation of various physiological processes. Pelvic floor electrical stimulation (PES) is a low-voltage clinical application, available for urinary incontinence (UI) treatment. Fibroblasts, as the main cellular component of vaginal wall and pelvic ligament, play an important role in the maintenance of pelvic health. We studied the effect of ES on fibroblasts in this study. ES was conducted with electrotaxis chambers on L929 fibroblast and the ES parameter was 100 mV/mm×2h. The results showed that ES increased intracellular Ca²⁺ concentration, promoted the expression of PCNA, CyclinB1, and CyclinD1, and increased the proportion of cells in S and G2 phages. After ES, fibroblasts get activated and proliferated. Besides, BAPTA-AM, a membrane permeated chelator for intracellular free Ca²⁺, partially inhibited the effect of ES on fibroblasts activation and proliferation promotion. Furthermore, we elucidated that Ca²⁺, as a second messenger and upstream signal for Smads and Akt signaling, regulated ES-induced nuclear translocation of smad2/3, phosphorylation of smad2/3, Akt, and GSK3β. Finally, we validated the effect of ES on PES mouse model. The results indicated that PES promoted the activation and proliferation of fibroblasts in vivo. In conclusion, we verify that ES can elevate the concentration of intracellular Ca²⁺ and activate its downstream signaling and then promote the activation of fibroblasts, which may be one of the mechanisms of PES therapy.

The Role of the Mammalian Target of Rapamycin (mTOR) in Pulmonary Fibrosis

The phosphoinositide 3-kinase (PI3K)/protein kinase B (AKT)/mammalian target of rapamycin (mTOR)-dependent pathway is one of the most integral pathways linked to cell metabolism, proliferation, differentiation, and survival. This pathway is dysregulated in a variety of diseases, including neoplasia, immune-mediated diseases, and fibroproliferative diseases such as pulmonary fibrosis. The mTOR kinase is frequently referred to as the master regulator of this pathway. Alterations in mTOR signaling are closely associated with dysregulation of autophagy, inflammation, and cell growth and survival, leading to the development of lung fibrosis. Inhibitors of mTOR have been widely studied in cancer therapy, as they may sensitize cancer cells to radiation therapy. Studies also suggest that mTOR inhibitors are promising modulators of fibroproliferative diseases such as idiopathic pulmonary fibrosis (IPF) and radiation-induced pulmonary fibrosis (RIPF). Therefore, mTOR represents an attractive and unique therapeutic target in pulmonary fibrosis. In this review, we discuss the pathological role of mTOR kinase in pulmonary fibrosis and examine how mTOR inhibitors may mitigate fibrotic progression.

PI3K/AKT/mTOR Signaling Mediates Valproic Acid-Induced Neuronal Differentiation of Neural Stem Cells through Epigenetic Modifications

Although valproic acid (VPA), has been shown to induce neuronal differentiation of neural stem cells (NSCs), the underlying mechanisms remain poorly understood. Here we investigated if and how mammalian target of rapamycin (mTOR) signaling is involved in the neuronal differentiation of VPA-induced NSCs. Our data demonstrated that mTOR activation not only promoted but also was necessary for the neuronal differentiation of NSCs induced by VPA. We further found that inhibition of mTOR signaling blocked demethylation of neuron-specific gene neurogenin 1 (Ngn1) regulatory element in induced cells. These are correlated with the significant alterations of passive DNA demethylation and the active DNA demethylation pathway in the Ngn1 promoter, but not the suppression of lysine-specific histone methylation and acetylation in the promoter region of Ngn1. These findings highlight a potentially important role for mTOR signaling, by working together with DNA demethylation, to influence the fate of NSCs via regulating the expression of Ngn1 in VPA-induced neuronal differentiation of NSCs.

The Fto Gene Regulates the Proliferation and Differentiation of Pre-Adipocytes in Vitro

The highly regulated differentiation and proliferation of pre-adipocytes play a key role in the initiation of obesity. Fat mass and obesity associated (FTO) is a novel gene strongly associated with the risk of obesity. A deficiency of FTO may cause growth retardation in addition to fat mass and adipocyte size reduction in vivo. To investigate the potential role of Fto gene on the proliferation and differentiation of pre-adipocytes, we generated Fto-knockdown and overexpressed 3T3-L1 cells. Using numerous proliferation assays our results suggest that Fto knockdown leads to suppression of proliferation, lower mitochondrial membrane potential, less cellular ATP, and decreased and smaller intracellular lipid droplets compared with controls (p < 0.05). Western blot analysis demonstrated that Fto knockdown can significantly suppress peroxisome proliferator-activated receptor gamma (PPARγ) and glucose transporter type 4 (GLUT4) expression and inhibit Akt phosphorylation. By contrast, overexpression of Fto had the opposing effect on proliferation, mitochondrial membrane potential, ATP generation, in vitro differentiation, Akt phosphorylation, and PPARγ and GLUT4 expression. Moreover, we demonstrated that Wortmannin, a phosphoinositide 3-kinase (PI3K) inhibitor, could inhibit phospho-Akt in Fto overexpressed 3T3-L1 cells. Taken together, the results suggest that Fto regulates the proliferation and differentiation of 3T3-L1 cells via multiple mechanisms, including PPARγ and PI3K/Akt signaling.