Target Of Rapamycin Signaling Pathway Research Articles

PKP2 induced by YAP/TEAD4 promotes malignant progression of gastric cancer.

Gastric cancer (GC) exhibits significant heterogeneity and its prognosis remains dismal. Therefore, it is essential to investigate new approaches for diagnosing and treating GC. Desmosome proteins are crucial for the advancement and growth of cancer. Plakophilin-2 (PKP2), a member of the desmosome protein family, frequently exhibits aberrant expression and is strongly associated with many tumor types' progression. In this study, we found upregulation of PKP2 in GC. Further correlation analysis showed a notable association between increased PKP2 expression and both tumor stage and poor prognosis in individuals diagnosed with gastric adenocarcinoma. In addition, our research revealed that the Yes-associated protein1 (YAP1)/TEAD4 complex could stimulate the transcriptional expression of PKP2 in GC. Elevated PKP2 levels facilitate activation of the AKT/mammalian target of rapamycin signaling pathway, thereby promoting the malignant progression of GC. By constructing a mouse model, we ultimately validated the molecular mechanism and function of PKP2 in GC. Taken together, these discoveries suggest that PKP2, as a direct gene target of YAP/TEAD4 regulation, has the potential to be used as an indication of GC progression and prognosis. PKP2 is expected to be a promising therapeutic target for GC.

New perspectives on the role of vitamin D in the mucosal barrier system of fish gills infected with Flavobacterium columnare

The mucosal barrier of vertebrates comprises a unique array of physical elements and bioactive molecules that act in concert to protect the host against pathogens. Vitamin D (VD), an essential nutrient for animals, along with its receptor (VDR), plays a major role in immunity. However, the correlation between VD/VDR and the mucosal barrier system remains unclear. Here, we employed the fish gill as a model and evaluated the role of VD as a dietary supplement in modifying this typical mucosal barrier system. Varies levels of VD (15.2, 364.3, 782.5, 1167.9, 1573.8, and 1980.1 IU/kg) were formulated and fed to grass carp (Ctenopharyngodon idella) for 70 d. Subsequently, fish were challenged with Flavobacterium columnare, a pathogen in epithelial tissues. Following infection, dietary VD alleviated gill rot and damage caused by F. columnare. Further investigations demonstrated that VD improved physical barrier function by elevating the antioxidant capacity and tight junction barriers, and moderated excessive apoptosis. The promoted physical barrier function was related to nuclear factor E2-related factor 2 and myosin light-chain kinase signaling. Additionally, VD treatment enhanced the immune barrier function by boosting disease resistance, producing antibacterial compounds and immunoglobulins, downregulating pro-inflammatory cytokines, and upregulating the gene expression of anti-inflammatory cytokines, which correlated with nuclear factor kappa B and the target of rapamycin signaling pathways. Thus, VD strengthened pathogen defenses in the gill mucosal barrier system. This finding supports the rationale for VD intervention in infectious diseases and will be critical for the viability of sustainable practices in aquaculture.

Discrete Mechanistic Target of Rapamycin Signaling Pathways, Stem Cells, and Therapeutic Targets.

The mechanistic target of rapamycin (mTOR) is a serine/threonine kinase that functions via its discrete binding partners to form two multiprotein complexes, mTOR complex 1 and 2 (mTORC1 and mTORC2). Rapamycin-sensitive mTORC1, which regulates protein synthesis and cell growth, is tightly controlled by PI3K/Akt and is nutrient-/growth factor-sensitive. In the brain, mTORC1 is also sensitive to neurotransmitter signaling. mTORC2, which is modulated by growth factor signaling, is associated with ribosomes and is insensitive to rapamycin. mTOR regulates stem cell and cancer stem cell characteristics. Aberrant Akt/mTOR activation is involved in multistep tumorigenesis in a variety of cancers, thereby suggesting that the inhibition of mTOR may have therapeutic potential. Rapamycin and its analogues, known as rapalogues, suppress mTOR activity through an allosteric mechanism that only suppresses mTORC1, albeit incompletely. ATP-catalytic binding site inhibitors are designed to inhibit both complexes. This review describes the regulation of mTOR and the targeting of its complexes in the treatment of cancers, such as glioblastoma, and their stem cells.

Sensing and regulation of C and N metabolism - novel features and mechanisms of the TOR and SnRK1 signaling pathways.

Carbon (C) and nitrogen (N) metabolisms are tightly integrated to allow proper plant growth and development. Photosynthesis is dependent on N invested in chlorophylls, enzymes, and structural components of the photosynthetic machinery, while N uptake and assimilation rely on ATP, reducing equivalents, and C-skeletons provided by photosynthesis. The direct connection between N availability and photosynthetic efficiency allows the synthesis of precursors for all metabolites and building blocks in plants. Thus, the capacity to sense and respond to sudden changes in C and N availability is crucial for plant survival and is mediated by complex yet efficient signaling pathways such as TARGET OF RAPAMYCIN (TOR) and SUCROSE-NON-FERMENTING-1-RELATED PROTEIN KINASE 1 (SnRK1). In this review, we present recent advances in mechanisms involved in sensing C and N status as well as identifying current gaps in our understanding. We finally attempt to provide new perspectives and hypotheses on the interconnection of diverse signaling pathways that will allow us to understand the integration and orchestration of the major players governing the regulation of the CN balance.

Identification and characterization of TOR in Macrobrachium rosenbergii and its role in muscle protein and lipid production

The recent scarcity of fishmeal and other resources means that studies on the intrinsic mechanisms of nutrients in the growth and development of aquatic animals at the molecular level have received widespread attention. The target of rapamycin (TOR) pathway has been reported to receive signals from nutrients and environmental stresses, and regulates cellular anabolism and catabolism to achieve precise regulation of cell growth and physiological activities. In this study, we cloned and characterized the full-length cDNA sequence of the TOR gene of Macrobrachium rosenbergii (MrTOR). MrTOR was expressed in all tissues, with higher expression in heart and muscle tissues. In situ hybridization also indicated that MrTOR was expressed in muscle, mainly around the nucleus. RNA interference decreased the expression levels of MrTOR and downstream protein synthesis-related genes (S6K, eIF4E, and eIF4B) (P < 0.05) and the expression and enzyme activity of the lipid synthesis-related enzyme, fatty acid synthase (FAS), and increased enzyme activity of the lipolysis-related enzyme, lipase (LPS). In addition, amino acid injection significantly increased the transcript levels of MrTOR and downstream related genes (S6K, eIF4E, eIF4B, and FAS), as well as triglyceride and total cholesterol tissue levels and FAS activity. Starvation significantly increased transcript levels and enzyme activities of adenylate-activated protein kinase and LPS and decreased transcript levels and enzyme activities of FAS, as well as transcript levels of MrTOR and its downstream genes (P < 0.05), whereas amino acid injection alleviated the starvation-induced decreases in transcript levels of these genes. These results suggested that arginine and leucine activated the TOR signaling pathway, promoted protein and lipid syntheses, and alleviated the pathway changes induced by starvation.

Glucosamine increases macrophage lipid accumulation by regulating the mammalian target of rapamycin signaling pathway

Glucosamine increases macrophage lipid accumulation by regulating the mammalian target of rapamycin signaling pathway

Targeting GABARAPL1/HIF-2a axis to induce tumor cell apoptosis in nasopharyngeal carcinoma.

The primary gene mutations associated with nasopharyngeal carcinoma (NPC) are located within the phosphoinositide 3-kinase-mammalian target of rapamycin signaling pathways, which have inhibitory effects on autophagy. Compounds that target autophagy could potentially be used to treat NPC. However, autophagy-related molecular targets in NPC remain to be elucidated. We aimed to examine levels of autophagy-related genes, including autophagy-related 4B cysteine peptidase (ATG4B) and gamma-aminobutyric acid (GABA) type A receptor-associated protein-like 1 (GABARAPL1), in NPC cells and explored their potential role as novel targets for the treatment of NPC. The mRNA and protein expression of autophagy-related genes were detected in several NPC cells. Levels of GABARAPL1 were modified by either overexpression or knockdown, followed by examining downstream targets using RT-qPCR and western blotting. The role of GABARAPL1 in NPC proliferation and apoptosis was examined by flow cytometry. Furthermore, the role of GABARAPL1 was assessed in vivo using a nude mouse xenograft tumor model. The underlying mechanism by which GABARAPL1 regulated nasopharyngeal tumor growth was investigated. Autophagy-related 4B cysteine peptidase (ATG4B), GABARAPL1, and Unc-51-like kinase 1 (ULK1) were significantly down-regulated in multiple NPC cell lines. Overexpression of GABARAPL1 up-regulated the expression of autophagy-related proteins, decreased the level of hypoxia-inducible factor (HIF)-2α, and induced apoptosis in NPC cells. Importantly, overexpression of GABARAPL1 slowed tumor growth. Western blotting showed that autophagy was activated, and HIF-2α was down-regulated in tumor tissues. HIF-2α, as a substrate for autophagic degradation, may play an interesting role during NPC progression.

MiRNA profiling of granulosa cell-derived exosomes reveals their role in promoting follicle development.

To explore whether granulosa cell (GC)-derived exosomes (GC-Exos) and follicular fluid-derived exosomes (FF-Exos) have functional similarities in follicle development and to establish relevant experiments to validate whether GC-Exoscould serve as a potential substitute for follicular fluid-derived exosomes to improve folliculogenesis.GC-Exoswere characterized. MicroRNA (miRNA) profiles of exosomes from human GCs and follicular fluid were analyzed in depth. The signature was associated with folliculogenesis, such as phosphatidylinositol 3 kinases-protein kinase B signal pathway, mammalian target of rapamycin signal pathway, mitogen-activated protein kinase signal pathway, Wnt signal pathway, and cyclic adenosine monophosphate signal pathway. A total of five prominent miRNAs were found to regulate the above five signaling pathways. These miRNAs include miRNA-486-5p, miRNA-10b-5p, miRNA-100-5p, miRNA-99a-5p, and miRNA-21-5p. The exosomes from GCs and follicular fluid were investigated to explore the effect on folliculogenesis by injecting exosomes into older mice. The proportion of follicles at each stage is counted to help us understand folliculogenesis. Exosomes derived from GCs were isolated successfully. miRNA profiles demonstrated a remarkable overlap between the miRNA profiles of FF-Exos and GC-Exos. The shared miRNA signature exhibited a positive influence on follicle development and activation. Furthermore, exosomes derived from GCs and follicular fluid promoted folliculogenesis in older female mice. Exosomes derived from GCs had similar miRNA profiles and follicle-promoting functions as follicular fluid exosomes. Consequently, GC-Exos are promising for replacing FF-Exos and developing new commercial reagents to improve female fertility.

The SLC38A9–mTOR axis is involved in autophagy in the juvenile yellow catfish (Pelteobagrus fulvidraco) under ammonia stress

The primary objective of this study was to examine the effect of acute ammonia stress on hepatic physiological alterations in yellow catfish by performing a comprehensive analysis of the metabolome and transcriptome. The present study showed that ammonia stress led to liver metabolic disruption, functional incapacitation, and oxidative damage. Transcriptomic and metabolomic analyses revealed transcriptional and metabolic differences in the liver of yellow catfish under control and high ammonia stress conditions. After 96 h of acute exposure to ammonia, the mRNA levels of 596 liver genes were upregulated, whereas those of 603 genes were downregulated. Enrichment analysis of the differentially expressed genes identified multiple signalling pathways associated with autophagy, including the endocytosis, autophagy-animal, and mammalian target of rapamycin signalling pathways. A total of 186 upregulated and 117 downregulated metabolites, primarily associated with amino acid biosynthesis pathways, were identified. Multi-omics integration revealed the solute carrier family 38 member 9 (SLC38A9)-mammalian target of rapamycin axis as a signalling nexus for amino acid-mediated modulation of autophagy flux, and q-PCR was used to assess the expression of autophagy-related genes (LC3a and sqstm1), revealing an initial inhibition followed by the restoration of autophagic flux during ammonia stress. Subsequent utilisation of arginine as a specific SLC38A9 activator during ammonia stress demonstrated that augmented SLC38A9 expression hindered autophagy, exacerbated ammonia toxicity, and caused a physiological decline (total cholesterol, total triglyceride, acid phosphatase, alkaline phosphatase, aspartate aminotransferase, and alanine aminotransferase levels were significantly increased), oxidative stress, and apoptosis. Autophagy activation may be an adaptive mechanism to resist ammonia stress.

Hepatocellular Ballooning is Due to Highly Pronounced Glycogenosis Potentially Associated with Steatosis and Metabolic Reprogramming.

Hepatocellular ballooning is a common finding in chronic liver disease, mainly characterized by rarefied cytoplasm that often contains Mallory-Denk bodies (MDB). Ballooning has mostly been attributed to degeneration but its striking resemblance to glycogenotic/steatotic changes characterizing preneoplastic hepatocellular lesions in animal models and chronic human liver diseases prompts the question whether ballooned hepatocytes (BH) are damaged cells on the path to death or rather viable cells, possibly involved in neoplastic development. Using specimens from 96 cirrhotic human livers, BH characteristics were assessed for their glycogen/lipid stores, enzyme activities, and proto-oncogenic signaling cascades by enzyme- and immunohistochemical approaches with serial paraffin and cryostat sections. BH were present in 43.8% of cirrhotic livers. Particularly pronounced excess glycogen storage of (glycogenosis) and/or lipids (steatosis) were characteristic, ground glass features and MDB were often observed. Decreased glucose-6-phosphatase, increased glucose-6-phosphate dehydrogenase activity and altered immunoreactivity of enzymes involved in glycolysis, lipid metabolism, and cholesterol biosynthesis were discovered. Furthermore, components of the insulin signaling cascade were upregulated along with insulin dependent glucose transporter glucose transporter 4 and the v-akt murine thymoma viral oncogene homolog/mammalian target of rapamycin signaling pathway associated with de novo lipogenesis. BH are hallmarked by particularly pronounced glycogenosis with facultative steatosis, many of their features being reminiscent of metabolic aberrations documented in preneoplastic hepatocellular lesions in experimental animals and chronic human liver diseases. Hence, BH are not damaged entities facing death but rather viable cells featuring metabolic reprogramming, indicative of a preneoplastic nature.

Intrathecal delivery of AAV-NDNF ameliorates disease progression of ALS mice

Amyotrophic lateral sclerosis (ALS) is a uniformly lethal neurodegenerative disease characterized by progressive deterioration of motor neurons and neuromuscular denervation. Adeno-associated virus (AAV)-mediated delivery of trophic factors is being considered as a potential disease-modifying therapeutic avenue. Here we show a marked effect of AAV-mediated over-expression of neuron-derived neurotrophic factor (NDNF) on SOD1G93A ALS model mice. First, we adopt AAV-PHP.eB capsid to enable widespread expression of target proteins in the brain and spinal cord when delivered intrathecally. Then we tested the effects of AAV-NDNF on SOD1G93A mice at different stages of disease. Interestingly, AAV-NDNF markedly improved motor performance and alleviated weight loss when delivered at early post-symptomatic stage. Injection in the middle post-symptomatic stages still improved the locomotion ability, although it did not alleviate the loss of body weight. Injection in the late stage also extended the life span of SOD1G93A mice. Furthermore, NDNF expression promoted the survival of spinal motoneurons, reduced abnormal protein aggregation, and preserved the innervated neuromuscular functions. We further analyzed the signaling pathways of NDNF expression and found that it activates cell survival and growth-associated mammalian target of rapamycin signaling pathway and downregulates apoptosis-related pathways. Thus, intrathecally AAV-NDNF delivery has provided a potential strategy for the treatment of ALS.

Osteopontin promotes gastric cancer progression via phosphatidylinositol-3-kinase/protein kinase B/mammalian target of rapamycin signaling pathway.

Gastric cancer (GC) is one of the most common malignant tumors. Osteopontin (OPN) is thought to be closely related to the occurrence, metastasis and prognosis of many types of tumors. To investigate the effects of OPN on the proliferation, invasion and migration of GC cells and its possible mechanism. The mRNA and protein expression of OPN in the GC cells were analyzed by real-time quantitative-reverse transcription polymerase chain reaction and western blotting, and observe the effect of varying degree expression OPN on the proliferation and other behaviors of GC. Next, the effects of OPN knockdown on GC cells migration and invasion were examined. The short hairpin RNA (shRNA) and negative control shRNA targeting OPN-shRNA were transfected into the cells according to the manufacturer's instructions. Non transfected cells were classified as control in the identical transfecting process. 24 h after RNA transfection cell proliferation activity was detected by 3-(4,5)-dimethylthiahiazo (-z-y1)-3,5-di-phenytetrazoliumromide assay, and cell invasiveness and migration were detected by Trans well assay. Meanwhile, the expression of protein kinase B (AKT), matrix metalloproteinase 2 (MMP-2) and vascular endothelial growth factor (VEGF) in the human GC cell lines was detected by reverse transcription polymerase chain reaction and western blotting. The results of this study revealed that OPN mRNA and protein expression levels were highly expressed in SGC-7901 cells. OPN knockdown by specific shRNA noticeably reduced the capabilities of proliferation, invasion and migration of SGC-7901 cells. Moreover, in the experiments of investigating the underlying mechanism, results showed that OPN knockdown could down-regulated the expression of MMP-2 and VEGF, it also decreased the phosphorylation of AKT. Meanwhile, the protein expression levels of MMP-2, VEGF and phosphorylated AKT was noticeable lower than that in control group in the GC cells after they were added to phosphatidylinositol-3-kinase (PI3K) inhibitor (LY294002). These results suggested that OPN though PI3K/AKT/mammalian target of rapamycin signal pathway to up-regulate MMP-2 and VEGF expression, which contribute SGC-7901 cells to proliferation, invasion and migration. Thus, our results demonstrate that OPN may serve as a novel prognostic biomarkers as well as a potential therapeutic targets for GC.

Salmonella inhibits tumor metastasis by downregulating epithelial cell adhesion molecules through the protein kinase-B/mammalian target of rapamycin signaling pathway

Epithelial cell adhesion molecules (EpCAM) are highly expressed in many carcinomas and regulate the epithelial–mesenchymal transition, which is required for tumor metastasis. Furthermore, EpCAM overexpression induces tumor cells to develop a stem cell–like phenotype and promotes tumor progression. Targeting EpCAM may be a promising approach for inhibiting tumor metastasis and progression. Salmonella treatment suppresses tumor growth and reduces metastatic nodules in tumor-bearing mice. Based on these results, we hypothesized that Salmonella-based treatments could inhibit the expression of metastasis-associated proteins. The dose-dependent Salmonella treatment significantly downregulated the levels of EpCAM and decreased the phosphorylation of protein kinase-B (AKT)/mTOR (mammalian target of rapamycin) pathway, as shown by immunoblotting. In addition, Salmonella treatment increased the levels of epithelial markers and decreased the levels of mesenchymal markers in a dose-dependent manner. Wound-healing and Transwell assays showed that Salmonella treatment significantly reduced tumor cell migration. The mice were intravenously injected with B16F10 and CT26 cells pre-incubated with or without Salmonella, and the survival of tumor-bearing mice in the Salmonella group increased, indicating an antimetastatic effect. Our findings demonstrate that Salmonella plays a role in inhibiting tumor metastasis by downregulating EpCAM via the AKT/mTOR signaling pathway and has great potential for cancer therapy.

Sodium Butyrate Induces Mitophagy and Apoptosis of Bovine Skeletal Muscle Satellite Cells through the Mammalian Target of Rapamycin Signaling Pathway.

Sodium butyrate (NaB) is one of the short-chain fatty acids and is notably produced in large amounts from dietary fiber in the gut. Recent evidence suggests that NaB induces cell proliferation and apoptosis. Skeletal muscle is rich in plenty of mitochondrial. However, it is unclear how NaB acts on host muscle cells and whether it is involved in mitochondria-related functions in myocytes. The present study aimed to investigate the role of NaB treatment on the proliferation, apoptosis, and mitophagy of bovine skeletal muscle satellite cells (BSCs). The results showed that NaB inhibited proliferation, promoted apoptosis of BSCs, and promoted mitophagy in a time- and dose-dependent manner in BSCs. In addition, 1 mM NaB increased the mitochondrial ROS level, decreased the mitochondrial membrane potential (MMP), increased the number of autophagic vesicles in mitochondria, and increased the mitochondrial DNA (mtDNA) and ATP level. The effects of the mTOR pathway on BSCs were investigated. The results showed that 1 mM NaB inhibited the mRNA and protein expression of mTOR and genes AKT1, FOXO1, and EIF4EBP1 in the mTOR signaling pathway. In contrast, the addition of PP242, an inhibitor of the mTOR signaling pathway also inhibited mRNA and protein expression levels of mTOR, AKT1, FOXO1, and EIF4EBP1 and promoted mitophagy and apoptosis, which were consistent with the effect of NaB treatment. NaB might promote mitophagy and apoptosis in BSCs by inhibiting the mTOR signaling pathway. Our results would expand the knowledge of sodium butyrate on bovine skeletal muscle cell state and mitochondrial function.

Design, synthesis and bioevaluation of PI3Kα-selective inhibitors as potential colorectal cancer drugs

The dysregulation of the phosphoinositide 3-kinase (PI3K)/mammalian target of rapamycin signaling pathway has been implicated in various human cancers, and isoform-selective inhibitors targeting PI3Kα have received significant interest in recent years. In this study, we have designed and synthesized three series of substituted benzoxazole derivatives based on the clinical candidate TAK-117 (8a). A detailed structure-activity relationship (SAR) study has identified the optimal compound 18a bearing a quinoxaline scaffold. Compared to the control 8a, 18a exhibited 4.4-fold more potent inhibitory activity against PI3Kα (IC50: 2.5 vs 11 nM) and better isoform-selective profiles over other PI3Ks. In addition, 18a showed a 1.5-fold more potent antiproliferative effect against HCT-116 cell lines (IC50: 3.79 vs 5.80 μM) and a better selectivity over the normal tissue cells. The potential antitumor mechanism and in vitro metabolic stability of 18a were also investigated. Notably, pharmacokinetic assays indicated that 18a had a higher plasma exposure, a higher maximum concentration and shorter elimination time compared to 8a.

Activation of endoplasmic reticulum stress by harmine suppresses the growth of esophageal squamous cell carcinoma.

The worldwide overall 5-year survival rate of esophageal squamous cell carcinoma (ESCC) patients is less than 20%, and novel therapeutic strategies for these patients are urgently needed. Harmine is a natural β-carboline alkaloid, which received great interest in cancer research because of its biological and anti-tumor activities. The aim of this study is to examine the effects of harmine on ESCC and its mechanism. We investigated the effects of harmine on proliferation, cell cycle, apoptosis, and tumor growth in vivo. RNA sequencing (RNA-seq), real-time PCR, and western blotting were used to detect the mechanism. Harmine inhibited ESCC cell growth in vitro and tumor growth in vivo. Differentially expressed genes in harmine-treated ESCC cells were mainly involved in protein processing in the endoplasmic reticulum (ER). Real-time PCR and western blotting confirmed harmine-induced cellular ER stress. CRISPR-Cas9 knockout of C/EBP homologous protein (CHOP) abolished harmine-induced expression of death receptor 5 and apoptosis. Harmine also induced the expression of CHOP-mediated sestrin-2, which in turn contributes to autophagosome formation via suppressing the AMP-activated protein kinase-protein kinase B-mammalian target of rapamycin signaling pathway. In conclusion, our results demonstrate that harmine inhibits the growth of ESCC through its regulation of ER stress, suggesting that it is a promising candidate for ESCC treatment.

LKB1/STK11 Tumor Suppressor Reduces Angiogenesis by Directly Interacting with VEGFR2 in Tumorigenesis.

Cervical tumors represent a prevalent form of cancer affecting women worldwide; current treatment options involve surgery, radiotherapy, and chemotherapy. Angiogenesis, the process of new blood vessel formation, is a crucial factor in cervical tumor growth. The molecular mechanisms underlying the effects of the liver kinase B1 (LKB1/STK11) tumor suppressor protein on tumor angiogenesis have not been elucidated. Therefore, we investigated the role of LKB1 in cervical tumor angiogenesis both in vitro and in vivo in this study. Our results demonstrated that LKB1 inhibited cervical tumor angiogenesis by suppressing the expression of angiogenesis-related factors such as vascular endothelial growth factor (VEGF) and hypoxia inducible factor-1α. LKB1 directly affected both carcinoma and vascular endothelial cells, resulting in a significant reduction in tumor growth and angiogenesis. Furthermore, LKB1 was found to bind to VEGF receptor 2 (VEGFR-2) and target the VEGFR-2-mediated protein kinase B/mechanistic target of rapamycin signaling pathway in endothelial cells, thereby reducing cervical tumor growth and angiogenesis. Our study provides new insights into the molecular mechanisms underlying the anti-tumor and anti-angiogenic effects of LKB1 in cervical cancer. These findings will help develop new therapeutic strategies for cervical cancer.

The regulation of PTEN: Novel insights into functions as cancer biomarkers and therapeutic targets.

This review summarizes the implications of the primary tumor suppressor protein phosphatase and tensin homolog (PTEN) in aggressive cancer development. PTEN interacts with other cellular proteins or factors suggesting the existence of an intricate molecular network that regulates their oncogenic function. Accumulating evidence has shown that PTEN exists and plays a role in the cytoplasmic organelles and in the nucleus. PTEN blocks phosphoinositide 3-kinases (PI3K)-protein kinase B-mammalian target of rapamycin signaling pathway by dephosphorylating phosphatidylinositol (PI)-3,4,5-triphosphate to PI-4,5-bisphosphate thus counteracting PI3K function. Studies have shown that PTEN expression is tightly regulated at transcriptional, posttranscriptional, and posttranslational levels (including protein-protein interactions and posttranslational modifications). Despite recent advances in PTEN research, the regulation and function of the PTEN gene remain largely unknown. How mutation or loss of specific exons in the PTEN gene occurs and involves in cancer development is not clear. This review illustrates the regulatory mechanisms of PTEN expression and discusses how PTEN participates in tumor development and/or suppression. Future prospects for the clinical applications are also highlighted.

Inhibition of Erb-B2 Receptor Tyrosine Kinase 3 and Associated Regulatory Pathways Potently Impairs Malignant Peripheral Nerve Sheath Tumor Proliferation and Survival

Malignant peripheral nerve sheath tumors (MPNSTs) are aggressive, currently untreatable Schwann cell-derived neoplasms with hyperactive mitogen-activated protein kinase and mammalian target of rapamycin signaling pathways. To identify potential therapeutic targets, previous studies used genome-scale shRNA screens that implicated the neuregulin-1 receptor erb-B2 receptor tyrosine kinase 3 (erbB3) in MPNST proliferation and/or survival. The current study shows that erbB3 is commonly expressed in MPNSTs and MPNST cell lines and that erbB3 knockdown inhibits MPNST proliferation and survival. Kinomic and microarray analyses of Schwann and MPNST cells implicate Src- and erbB3-mediated calmodulin-regulated signaling as key pathways. Consistent with this, inhibition of upstream (canertinib, sapitinib, saracatinib, and calmodulin) and parallel (AZD1208) signaling pathways involving mitogen-activated protein kinase and mammalian target of rapamycin reduced MPNST proliferation and survival. ErbB inhibitors (canertinib and sapitinib) or erbB3 knockdown in combination with Src (saracatinib), calmodulin [trifluoperazine (TFP)], or proviral integration site of Moloney murine leukemia kinase (AZD1208) inhibition even more effectively reduces proliferation and survival. Drug inhibition enhances an unstudied calmodulin-dependent protein kinase IIα phosphorylation site in an Src-dependent manner. The Src family kinase inhibitor saracatinib reduces both basal and TFP-induced erbB3 and calmodulin-dependent protein kinase IIα phosphorylation. Src inhibition (saracatinib), like erbB3 knockdown, prevents these phosphorylation events; and when combined with TFP, it even more effectively reduces proliferation and survival compared with monotherapy. These findings implicate erbB3, calmodulin, proviral integration site of Moloney murine leukemia kinases, and Src family members as important therapeutic targets in MPNSTs and demonstrate that combinatorial therapies targeting critical MPNST signaling pathways are more effective.

Detection of brain somatic mutations in focal cortical dysplasia during epilepsy presurgical workup.

Brain-restricted somatic variants in genes of the mechanistic target of rapamycin signalling pathway cause focal epilepsies associated with focal cortical dysplasia type II. We hypothesized that somatic variants could be identified from trace tissue adherent to explanted stereoelectroencephalography electrodes used in the presurgical epilepsy workup to localize the epileptogenic zone. We investigated three paediatric patients with drug-resistant focal epilepsy subjected to neurosurgery. In the resected brain tissue, we identified low-level mosaic somatic mutations in AKT3 and DEPDC5 genes. We collected stereoelectroencephalography depth electrodes in the context of a second presurgical evaluation and identified 4/33 mutation-positive electrodes that were either located in the epileptogenic zone or at the border of the dysplasia. We provide the proof-of-concept that somatic mutations with low levels of mosaicism can be detected from individual stereoelectroencephalography electrodes and support a link between the mutation load and the epileptic activity. Our findings emphasize future opportunities for integrating genetic testing from stereoelectroencephalography electrodes into the presurgical evaluation of refractory epilepsy patients with focal cortical dysplasia type II to improve the patients' diagnostic journey and guide towards precision medicine.