Membrane localization of phosphatidylinositol 3-kinase is sufficient to activate multiple signal-transducing kinase pathways

Hemifacial myohyperplasia is due to somatic muscular PIK3CA gain-of-function mutations and responds to pharmacological inhibition

Hemifacial myohyperplasia (HFMH) is a rare cause of facial asymmetry exclusively involving facial muscles. The underlying cause and the mechanism of disease progression are unknown. Here, we identified a somatic gain-of-function mutation of PIK3CA in five pediatric patients with HFMH. To understand the physiopathology of muscle hypertrophy in this context, we created a mouse model carrying specifically a PIK3CA mutation in skeletal muscles. PIK3CA gain-of-function mutation led to striated muscle cell hypertrophy, mitochondria dysfunction, and hypoglycemia with low circulating insulin levels. Alpelisib treatment, an approved PIK3CA inhibitor, was able to prevent and reduce muscle hypertrophy in the mouse model with correction of endocrine anomalies. Based on these findings, we treated the five HFMH patients. All patients demonstrated clinical, esthetical, and radiological improvement with proof of target engagement. In conclusion, we show that HFMH is due to somatic alteration of PIK3CA and is accessible to pharmacological intervention.

An essential signaling function of cytoplasmic NELFB is independent of RNA polymerase II pausing

The four-subunit negative elongation factor (NELF) complex mediates RNA polymerase II (Pol II) pausing at promoter-proximal regions. Ablation of individual NELF subunits destabilizes the NELF complex and causes cell lethality, leading to the prevailing concept that NELF-mediated Pol II pausing is essential for cell proliferation. Using separation-of-function mutations, we show here that NELFB function in cell proliferation can be uncoupled from that in Pol II pausing. NELFB mutants sequestered in the cytoplasm and deprived of NELF nuclear function still support cell proliferation and part of the NELFB-dependent transcriptome. Mechanistically, cytoplasmic NELFB physically and functionally interacts with prosurvival signaling kinases, most notably phosphatidylinositol-3-kinase/AKT. Ectopic expression of membrane-tethered phosphatidylinositol-3-kinase/AKT partially bypasses the role of NELFB in cell proliferation, but not Pol II occupancy. Together, these data expand the current understanding of the physiological impact of Pol II pausing and underscore the multiplicity of the biological functions of individual NELF subunits.

Familial CCM Genes Might Not Be Main Drivers for Pathogenesis of Sporadic CCMs-Genetic Similarity between Cancers and Vascular Malformations

Cerebral cavernous malformations (CCMs) are abnormally dilated intracranial capillaries that form cerebrovascular lesions with a high risk of hemorrhagic stroke. Recently, several somatic "activating" gain-of-function (GOF) point mutations in PIK3CA (phosphatidylinositol-4, 5-bisphosphate 3-kinase catalytic subunit p110α) were discovered as a dominant mutation in the lesions of sporadic forms of cerebral cavernous malformation (sCCM), raising the possibility that CCMs, like other types of vascular malformations, fall in the PIK3CA-related overgrowth spectrum (PROS). However, this possibility has been challenged with different interpretations. In this review, we will continue our efforts to expound the phenomenon of the coexistence of gain-of-function (GOF) point mutations in the PIK3CA gene and loss-of-function (LOF) mutations in CCM genes in the CCM lesions of sCCM and try to delineate the relationship between mutagenic events with CCM lesions in a temporospatial manner. Since GOF PIK3CA point mutations have been well studied in reproductive cancers, especially breast cancer as a driver oncogene, we will perform a comparative meta-analysis for GOF PIK3CA point mutations in an attempt to demonstrate the genetic similarities shared by both cancers and vascular anomalies.

PIK3CA gain-of-function mutation in adipose tissue induces metabolic reprogramming with Warburg-like effect and severe endocrine disruption

PIK3CA-related overgrowth syndrome (PROS) is a genetic disorder caused by somatic mosaic gain-of-function mutations of PIK3CA. Clinical presentation of patients is diverse and associated with endocrine disruption. Adipose tissue is frequently involved, but its role in disease development and progression has not been elucidated. Here, we created a mouse model of PIK3CA-related adipose tissue overgrowth that recapitulates patient phenotype. We demonstrate that PIK3CA mutation leads to GLUT4 membrane accumulation with a negative feedback loop on insulin secretion, a burst of liver IGFBP1 synthesis with IGF-1 sequestration, and low circulating levels. Mouse phenotype was mainly driven through AKT2. We also observed that PIK3CA mutation induces metabolic reprogramming with Warburg-like effect and protein and lipid synthesis, hallmarks of cancer cells, in vitro, in vivo, and in patients. We lastly show that alpelisib is efficient at preventing and improving PIK3CA-adipose tissue overgrowth and reversing metabolomic anomalies in both animal models and patients.

Exploring the recent trends in perturbing the cellular signaling pathways in cancer by natural products

Cancer is commonly thought to be the product of irregular cell division. According to the World Health Organization (WHO), cancer is the major cause of death globally. Nature offers an abundant supply of bioactive compounds with high therapeutic efficacy. Anticancer effects have been studied in a variety of phytochemicals found in nature. When Food and Drug Administration (FDA)-approved anticancer drugs are combined with natural compounds, the effectiveness improves. Several agents have already progressed to clinical trials based on these promising results of natural compounds against various cancer forms. Natural compounds prevent cancer cell proliferation, development, and metastasis by inducing cell cycle arrest, activating intrinsic and extrinsic apoptosis pathways, generating reactive oxygen species (ROS), and down-regulating activated signaling pathways. These natural chemicals are known to affect numerous important cellular signaling pathways, such as NF-B, MAPK, Wnt, Notch, Akt, p53, AR, ER, and many others, to cause cell death signals and induce apoptosis in pre-cancerous or cancer cells without harming normal cells. As a result, non-toxic “natural drugs” taken from nature’s bounty could be effective for the prevention of tumor progression and/or therapy of human malignancies, either alone or in combination with conventional treatments. Natural compounds have also been shown in preclinical studies to improve the sensitivity of resistant cancers to currently available chemotherapy agents. To summarize, preclinical and clinical findings against cancer indicate that natural-sourced compounds have promising anticancer efficacy. The vital purpose of these studies is to target cellular signaling pathways in cancer by natural compounds.

Activation of PI3K/p110α in the Lung Mesenchyme Affects Branching Morphogenesis and Club Cell Differentiation

Epithelial–mesenchymal interaction is required for normal growth, morphogenetic patterning, and cellular differentiation in developing lungs. Various signaling pathways have been defined in establishing the patterning of this branched organ. The phosphoinositide-3-kinase (PI3K) signaling plays an important role in disease pathogenesis but remains largely uncharacterized in embryonic development. In this study, we activated a specific catalytic subunit of PI3K catalytic enzymes, Class IA p110α (p110α), in the embryonic lung mesenchyme using the Dermo1-Cre mouse. Activation of p110α promoted branching morphogenesis and blocked club cell differentiation in both proximal and distal airways. Mechanistically, the LIM homeodomain gene Islet-1 (Isl1), fibroblast growth factor 10 (Fgf10), and SRY (sex-determining region Y)-box9 (Sox9) were found to be downstream targets of p110α. The significantly increased expressions of Isl1, Fgf10, and Sox9 resulted in the stimulation of branching in mutant lungs. Activation of p110α-mediated signaling also increased the expression of phosphatase and tensin homolog deleted on chromosome 10 (Pten) and hairy/enhancer of split 1 (Hes1), which in turn blocked club cell differentiation. Thus, the signaling pathway by which PI3K/p110α-regulated epithelial–mesenchymal interactions may entail Isl1–Fgf10–Sox9 and Pten–Hes1 networks, which consequently regulate branching morphogenesis and club cell differentiation, respectively.

SHMT2 inhibition disrupts the TCF3 transcriptional survival program in Burkitt lymphoma

Burkitt lymphoma (BL) is an aggressive lymphoma type that is currently treated by intensive chemoimmunotherapy. Despite the favorable clinical outcome for most patients with BL, chemotherapy-related toxicity and disease relapse remain major clinical challenges, emphasizing the need for innovative therapies. Using genome-scale CRISPR-Cas9 screens, we identified B-cell receptor (BCR) signaling, specific transcriptional regulators, and one-carbon metabolism as vulnerabilities in BL. We focused on serine hydroxymethyltransferase 2 (SHMT2), a key enzyme in one-carbon metabolism. Inhibition of SHMT2 by either knockdown or pharmacological compounds induced anti-BL effects in vitro and in vivo. Mechanistically, SHMT2 inhibition led to a significant reduction of intracellular glycine and formate levels, which inhibited the mTOR pathway and thereby triggered autophagic degradation of the oncogenic transcription factor TCF3. Consequently, this led to a collapse of tonic BCR signaling, which is controlled by TCF3 and is essential for BL cell survival. In terms of clinical translation, we also identified drugs such as methotrexate that synergized with SHMT inhibitors. Overall, our study has uncovered the dependency landscape in BL, identified and validated SHMT2 as a drug target, and revealed a mechanistic link between SHMT2 and the transcriptional master regulator TCF3, opening up new perspectives for innovative therapies.

B-cell intrinsic and extrinsic signals that regulate central tolerance of mouse and human B cells

The random recombination of immunoglobulin V(D)J gene segments produces unique IgM antibodies that serve as the antigen receptor for each developing B cell. Hence, the newly formed B cell repertoire is comprised of a variety of specificities that display a range of reactivity with self-antigens. Newly generated IgM⁺ immature B cells that are non-autoreactive or that bind self-antigen with low avidity are licensed to leave the bone marrow with their intact antigen receptor and to travel via the blood to the peripheral lymphoid tissue for further selection and maturation. In contrast, clones with medium to high avidity for self-antigen remain within the marrow and undergo central tolerance, a process that revises their antigen receptor or eliminates the autoreactive B cell altogether. Thus, central B cell tolerance is critical for reducing the autoreactive capacity and avidity for self-antigen of our circulating B cell repertoire. Bone marrow cultures and mouse models have been instrumental for understanding the mechanisms that regulate the selection of bone marrow B cells. Here, we review recent studies that have shed new light on the contribution of the ERK, PI3K, and CXCR4 signaling pathways in the selection of mouse and human immature B cells that either bind or do not bind self-antigen.

Alpelisib administration reduced lymphatic malformations in a mouse model and in patients

Lymphatic cystic malformations are rare genetic disorders mainly due to somatic gain-of-function mutations in the PIK3CA gene. These anomalies are frequently associated with pain, inflammatory flares, esthetic deformities, and, in severe forms, life-threatening conditions. There is no approved medical therapy for patients with lymphatic malformations. In this proof-of-concept study, we developed a genetic mouse model of PIK3CA-related lymphatic malformations that recapitulates human disease. Using this model, we demonstrated the efficacy of alpelisib, an approved pharmacological inhibitor of PIK3CA in oncology, in preventing lymphatic malformation occurrence, improving lymphatic anomalies, and extending survival. On the basis of these results, we treated six patients with alpelisib, including three children, displaying severe PIK3CA-related lymphatic malformations. Patients were already unsuccessfully treated with rapamycin, percutaneous sclerotherapies, and debulking surgical procedures. We assessed the volume of lymphatic malformations using magnetic resonance imaging (MRI) for each patient. Alpelisib administration was associated with improvements in the six patients. Previously intractable vascular malformations shrank, and pain and inflammatory flares were attenuated. MRI showed a decrease of 48% in the median volume of lymphatic malformations over 6 months on alpelisib. During the study, two patients developed adverse events potentially related to alpelisib, including grade 1 mucositis and diarrhea. In conclusion, this study supports PIK3CA inhibition as a promising therapeutic strategy in patients with PIK3CA-related lymphatic anomalies.

The metastasis suppressor protein NM23-H1 modulates the PI3K-AKT axis through interaction with the p110α catalytic subunit

The PI3K pathway is one of the most deregulated pathways in cancer, which is predominantly due to gain of function mutations or altered expression of the PI3KCA gene. This is codified by what is seen for the class I PI3K catalytic subunit p110α, a common feature of many cancers. The metastasis suppressor protein NM23-H1 (NME1), whose ability to suppress the metastasis activities of different tumors has been widely described and was previously reported to alter phosphatidylinositol signaling. Here, we show interaction of NM23-H1 with the p110α subunit and the functional consequence of this interaction. This interaction is predominantly localized at the plasma membrane with some signals seen in the cytoplasmic compartment. Analysis of NM23-H1 levels showed a negative correlation between NM23-H1 expression and Akt phosphorylation, the key marker of PI3K pathway activation. Investigating the functional consequence of this interaction using cell motility and clonogenicity assays showed that expression of NM23-H1 reversed the enhanced migration, invasion, adhesion, and filopodia structure formation in cells expressing the p110α catalytic subunit. A similar trend was seen in anchorage-independent assays. Notably, differential analyses using NM23-H1 mutants which lacked the enzymatic and metastasis suppressor activity, showed no detectable interaction between p110α and the NM23-H1 mutant proteins P96S, H118F, and S120G, as well as no dysregulation of the PI3K-AKT axis.

MAPS: machine-assisted phenotype scoring enables rapid functional assessment of genetic variants by high-content microscopy

BACKGROUND

Genetic testing is widely used in evaluating a patient's predisposition to hereditary diseases. In the case of cancer, when a functionally impactful mutation (i.e. genetic variant) is identified in a disease-relevant gene, the patient is at elevated risk of developing a lesion in their lifetime. Unfortunately, as the rate and coverage of genetic testing has accelerated, our ability to assess the functional status of new variants has fallen behind. Therefore, there is an urgent need for more practical, streamlined and cost-effective methods for classifying variants.

RESULTS

To directly address this issue, we designed a new approach that uses alterations in protein subcellular localization as a key indicator of loss of function. Thus, new variants can be rapidly functionalized using high-content microscopy (HCM). To facilitate the analysis of the large amounts of imaging data, we developed a new software toolkit, named MAPS for machine-assisted phenotype scoring, that utilizes deep learning to extract and classify cell-level features. MAPS helps users leverage cloud-based deep learning services that are easy to train and deploy to fit their specific experimental conditions. Model training is code-free and can be done with limited training images. Thus, MAPS allows cell biologists to easily incorporate deep learning into their image analysis pipeline. We demonstrated an effective variant functionalization workflow that integrates HCM and MAPS to assess missense variants of PTEN, a tumor suppressor that is frequently mutated in hereditary and somatic cancers.

CONCLUSIONS

This paper presents a new way to rapidly assess variant function using cloud deep learning. Since most tumor suppressors have well-defined subcellular localizations, our approach could be widely applied to functionalize variants of uncertain significance and help improve the utility of genetic testing.

Gene Expression Profiling of Type 2 Diabetes Mellitus by Bioinformatics Analysis

Objective

The aim of this study was to identify the candidate genes in type 2 diabetes mellitus (T2DM) and explore their potential mechanisms.

Methods

The gene expression profile GSE26168 was downloaded from the Gene Expression Omnibus (GEO) database. The online tool GEO2R was used to obtain differentially expressed genes (DEGs). Gene Ontology (GO) term enrichment analysis and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis were performed by using Metascape for annotation, visualization, and comprehensive discovery. The protein-protein interaction (PPI) network of DEGs was constructed by using Cytoscape software to find the candidate genes and key pathways.

Results

A total of 981 DEGs were found in T2DM, including 301 upregulated genes and 680 downregulated genes. GO analyses from Metascape revealed that DEGs were significantly enriched in cell differentiation, cell adhesion, intracellular signal transduction, and regulation of protein kinase activity. KEGG pathway analysis revealed that DEGs were mainly enriched in the cAMP signaling pathway, Rap1 signaling pathway, regulation of lipolysis in adipocytes, PI3K-Akt signaling pathway, MAPK signaling pathway, and so on. On the basis of the PPI network of the DEGs, the following 6 candidate genes were identified: PIK3R1, RAC1, GNG3, GNAI1, CDC42, and ITGB1.

Conclusion

Our data provide a comprehensive bioinformatics analysis of genes, functions, and pathways, which may be related to the pathogenesis of T2DM.

Constitutively active PIK3CA mutations are expressed by lymphatic and vascular endothelial cells in capillary lymphatic venous malformation

Capillary lymphatic venous malformations (CLVM) are complex vascular anomalies characterized by aberrant and enlarged lymphatic and blood vessels. CLVM appear during fetal development and enlarge after birth, causing life-long complications such as coagulopathy, pulmonary embolism, chronic pain, and disfigurement. Treatment includes surgical debulking, amputation, and recurrent sclerotherapy. Somatic, mosaic mutations in the 110-kD catalytic α-subunit of phosphoinositide-3-kinase (PIK3CA) gene have been previously identified in affected tissues from CLVM patients; however, the cell population harboring the mutation is still unknown. In this study, we hypothesized that endothelial cells (EC) carry the PIK3CA mutations and play a major role in the cellular origin of CLVM. We isolated EC from the lesions of seven patients with CLVM and identified PIK3CA hotspot mutations. The CLVM EC exhibited constitutive phosphorylation of the PI3K effector AKT as well as hyperproliferation and increased resistance to cell death compared to normal EC. Inhibitors of PIK3CA (BYL719) and AKT (ARQ092) attenuated the proliferation of CLVM EC in a dose-dependent manner. A xenograft model of CLVM was developed by injecting patient-derived EC into the flanks of immunocompromised mice. CLVM EC formed lesions with enlarged lymphatic and vascular channels, recapitulating the patient histology. EC subpopulations were further obtained by both immunomagnetic separation into lymphatic EC (LEC) and vascular EC (VEC) and generation of clonal populations. By sequencing these subpopulations, we determined that both LEC and VEC from the same patient express the PIK3CA mutation, exhibit increased AKT activation and can form lymphatic or vascular lesions in mouse.

Growth Factor-Dependent and -Independent Activation of mTORC2

The target of rapamycin complex 2 (TORC2) was discovered in 2002 in budding yeast. Its mammalian counterpart, mTORC2, was first described in 2004. Soon thereafter it was demonstrated that mTORC2 directly phosphorylates Akt on Ser473, ending a long search for the elusive 'second' insulin-responsive Akt kinase. In this review we discuss key evidence pertaining to the subcellular localization of mTORC2, highlighting a spatial heterogeneity that relates to mTORC2 activation. We summarize current models for how growth factors (GFs), such as insulin, trigger mTORC2 activation, and we provide a comprehensive discussion focusing on a new exciting frontier, the molecular mechanisms underpinning GF-independent activation of mTORC2.

p110γ deficiency protects against pancreatic carcinogenesis yet predisposes to diet-induced hepatotoxicity

Pancreatic ductal adenocarcinoma (PDAC) is notorious for its poor survival and resistance to conventional therapies. PI3K signaling is implicated in both disease initiation and progression, and specific inhibitors of selected PI3K p110 isoforms for managing solid tumors are emerging. We demonstrate that increased activation of PI3K signals cooperates with oncogenic Kras to promote aggressive PDAC in vivo. The p110γ isoform is overexpressed in tumor tissue and promotes carcinogenesis via canonical AKT signaling. Its selective blockade sensitizes tumor cells to gemcitabine in vitro, and genetic ablation of p110γ protects against Kras-induced tumorigenesis. Diet/obesity was identified as a crucial means of p110 subunit up-regulation, and in the setting of a high-fat diet, p110γ ablation failed to protect against tumor development, showing increased activation of pAKT and hepatic damage. These observations suggest that a careful and judicious approach should be considered when targeting p110γ for therapy, particularly in obese patients.

Cellular and molecular mechanisms of PIK3CA-related vascular anomalies

The phosphoinositide 3-kinase (PI3K) pathway is a major mediator of growth factor signaling, cell proliferation and metabolism. Somatic gain-of-function mutations in PIK3CA, the catalytic subunit of PI3K, have recently been discovered in a number of vascular anomalies. The timing and origin of these mutations remain unclear although they are believed to occur during embryogenesis. The cellular origin of these lesions likely involves endothelial cells or an early endothelial cell lineage. This review will cover the diseases and syndromes associated with PIK3CA mutations and discuss the cellular origin, pathways and mechanisms. Activating PIK3CA 'hot spot' mutations have long been associated with a multitude of cancers allowing the development of targeted pharmacological inhibitors that are FDA-approved or in clinical trials. Current and future therapeutic approaches for PIK3CA-related vascular anomalies are discussed.

Accumulation of Innate Amyloid Beta Peptide in Glioblastoma Tumors

Immunostaining with specific antibodies has shown that innate amyloid beta (Aβ) is accumulated naturally in glioma tumors and nearby blood vessels in a mouse model of glioma. In immunofluorescence images, Aβ peptide coincides with glioma cells, and enzyme-linked immunosorbent assay (ELISA) have shown that Aβ peptide is enriched in the membrane protein fraction of tumor cells. ELISAs have also confirmed that the Aβ(1–40) peptide is enriched in glioma tumor areas relative to healthy brain areas. Thioflavin staining revealed that at least some amyloid is present in glioma tumors in aggregated forms. We may suggest that the presence of aggregated amyloid in glioma tumors together with the presence of Aβ immunofluorescence coinciding with glioma cells and the nearby vasculature imply that the source of Aβ peptides in glioma can be systemic Aβ from blood vessels, but this question remains unresolved and needs additional studies.

Active PI3K abrogates central tolerance in high-avidity autoreactive B cells

High-avidity autoreactive B cells are typically removed by central tolerance mechanisms in the bone marrow. Greaves et al. demonstrate that B cell–intrinsic expression of active PI3Kα prevents central tolerance and effectively promotes differentiation and activation of high-avidity autoreactive B cells in the periphery.

Autoreactive B cells that bind self-antigen with high avidity in the bone marrow undergo mechanisms of central tolerance that prevent their entry into the peripheral B cell population. These mechanisms are breached in many autoimmune patients, increasing their risk of B cell–mediated autoimmune diseases. Resolving the molecular pathways that can break central B cell tolerance could therefore provide avenues to diminish autoimmunity. Here, we show that B cell–intrinsic expression of a constitutively active form of PI3K-P110α by high-avidity autoreactive B cells of mice completely abrogates central B cell tolerance and further promotes these cells to escape from the bone marrow, differentiate in peripheral tissue, and undergo activation in response to self-antigen. Upon stimulation with T cell help factors, these B cells secrete antibodies in vitro but remain unable to secrete autoantibodies in vivo. Overall, our data demonstrate that activation of the PI3K pathway leads high-avidity autoreactive B cells to breach central, but not late, stages of peripheral tolerance.

The Ras Recruitment System (RRS) for the Identification and Characterization of Protein-Protein Interactions

Protein-protein interactions are the basis for all biochemical cellular activities. The Ras Recruitment System, RRS, is a method for studying interactions between known proteins as well as identification of novel interactions following a cDNA library screen. The method is based on the recruitment of the Ras protein to the plasma membrane via protein-protein interactions. The interaction between proteins is studied in a temperature-sensitive yeast Saccharomyces cerevisiae mutant strain. This mutant is able to grow under restrictive temperature conditions when the Ras viability pathway becomes activated as a result of a positive protein-protein interaction. The RRS complements the limitations and problems that arise from the yeast two-hybrid system.

Nuclear FOXO1 promotes lymphomagenesis in germinal center B cells

Forkhead box class O1 (FOXO1) acts as a tumor suppressor in solid tumors. The oncogenic phosphoinositide-3-kinase (PI3K) pathway suppresses FOXO1 transcriptional activity by enforcing its nuclear exclusion upon AKT-mediated phosphorylation. We show here abundant nuclear expression of FOXO1 in Burkitt lymphoma (BL), a germinal center (GC) B-cell–derived lymphoma whose pathogenesis is linked to PI3K activation. Recurrent FOXO1 mutations, which prevent AKT targeting and lock the transcription factor in the nucleus, are used by BL to circumvent mutual exclusivity between PI3K and FOXO1 activation. Using genome editing in human and mouse lymphomas in which MYC and PI3K cooperate synergistically in tumor development, we demonstrate proproliferative and antiapoptotic activity of FOXO1 in BL and identify its nuclear localization as an oncogenic event in GC B-cell–derived lymphomagenesis.

Activated kinase screening identifies the IKBKE oncogene as a positive regulator of autophagy

Macroautophagy/autophagy is one of the major responses to stress in eukaryotic cells and is implicated in several pathological conditions such as infections, neurodegenerative diseases and cancer. Interestingly, cancer cells take full advantage of autophagy both to support tumor growth in adverse microenvironments and to oppose damages induced by anti-neoplastic therapies. Importantly, different human oncogenes are able to modulate this survival mechanism to support the transformation process, ultimately leading to 'autophagy addiction'. Still, oncogenic signaling events, impinging on the control of autophagy, are poorly characterized, limiting our possibilities to take advantage of these mechanisms for therapeutic purposes. Here, we screened a library of activated kinases for their ability to stimulate autophagy. By this approach, we identified novel potential regulators of the autophagic process and, among them, the IKBKE oncogene. Specifically, we demonstrate that this oncoprotein is able to stimulate autophagy when overexpressed, an event frequently found in breast tumors, and that its activity is strictly required for breast cancer cells to support the autophagic process. Interestingly, different oncogenic pathways typically involved in breast cancer, namely ERBB2 and PI3K-AKT-MTOR, also rely on IKBKE to control this process. Ultimately, we show that IKBKE-dependent autophagy is necessary for breast cancer cell proliferation, suggesting an important supporting role for this oncogene and autophagy in these tumors. Abbreviations: AAK1: AP2 associated kinase 1; AMPK: 5'-prime-AMP-activated protein kinase; AKT1: AKT serine/threonine kinase 1; BAF: bafilomycin A₁; CA: constitutively activated; CDK17: cyclin dependent kinase 17; CDK18: cyclin dependent kinase 18; CHUK: conserved helix-loop-helix ubiquitous kinase; EGF: epidermal growth factor; ERBB2: erb-b2 receptor tyrosine kinase 2; FGF: fibroblast growth factor; FM: full medium; GALK2: galactokinase 2; IKBKB: inhibitor of nuclear factor kappa B kinase subunit beta; IKBKE: inhibitor of nuclear factor kappa B kinase subunit epsilon; IKK: IκB kinase complex; KD: kinase dead; MAP1LC3B/LC3B: microtubule associated protein 1 light chain 3 beta; MAPK1: mitogen-activated protein kinase 1; MAPK15: mitogen-activated protein kinase 15; MTORC1: mammalian target of rapamycin kinase complex 1; myr: myristoylation/myristoylated; NFKBIA: NFKB inhibitor alpha; PDGF: platelet derived growth factor; PFKL: phosphofructokinase, liver type; PRKAA1: protein kinase AMP-activated catalytic subunit alpha 1; PRKCD: protein kinase C delta; SQSTM1: sequestosome 1; TBK1: TANK binding kinase 1; TNBC: triple-negative breast cancer; TSC2: TSC complex subunit 2; WB: western blot; WT: wild-type.

c-Jun N-terminal kinase (JNK)-mediated induction of mSin1 expression and mTORC2 activation in mesenchymal cells during fibrosis

Mammalian target of rapamycin complex 2 (mTORC2) has been shown to regulate mTORC1/4E-BP1/eIF4E signaling and collagen I expression in mesenchymal cells (MCs) during fibrotic activation. Here we investigated the regulation of the mTORC2 binding partner mammalian stress-activated protein kinase-interacting protein 1 (mSin1) in MCs derived from human lung allografts and identified a novel role for mSin1 during fibrosis. mSin1 was identified as a common downstream target of key fibrotic pathways, and its expression was increased in MCs in response to pro-fibrotic mediators: lysophosphatidic acid (LPA), transforming growth factor β, and interleukin 13. Fibrotic MCs had higher mSin1 protein levels than nonfibrotic MCs, and siRNA-mediated silencing of mSIN1 inhibited collagen I expression and mTORC1/2 activity in these cells. Autocrine LPA signaling contributed to constitutive up-regulation of mSin1 in fibrotic MCs, and mSin1 was decreased because of LPA receptor 1 siRNA treatment. We identified c-Jun N-terminal kinase (JNK) as a key intermediary in mSin1 up-regulation by the pro-fibrotic mediators, as pharmacological and siRNA-mediated inhibition of JNK prevented the LPA-induced mSin1 increase. Proteasomal inhibition rescued mSin1 levels after JNK inhibition in LPA-treated MCs, and the decrease in mSin1 ubiquitination in response to LPA was counteracted by JNK inhibitors. Constitutive JNK1 overexpression induced mSin1 expression and could drive mTORC2 and mTORC1 activation and collagen I expression in nonfibrotic MCs, effects that were reversed by siRNA-mediated mSIN1 silencing. These results indicate that LPA stabilizes mSin1 protein expression via JNK signaling by blocking its proteasomal degradation and identify the LPA/JNK/mSin1/mTORC/collagen I pathway as critical for fibrotic activation of MCs.

Pretangle pathology within cholinergic nucleus basalis neurons coincides with neurotrophic and neurotransmitter receptor gene dysregulation during the progression of Alzheimer's disease

Cholinergic basal forebrain neurons of the nucleus basalis of Meynert (nbM) regulate attentional and memory function and are exquisitely prone to tau pathology and neurofibrillary tangle (NFT) formation during the progression of Alzheimer's disease (AD). nbM neurons require the neurotrophin nerve growth factor (NGF), its cognate receptor TrkA, and the pan-neurotrophin receptor p75NTR for their maintenance and survival. Additionally, nbM neuronal activity and cholinergic tone are regulated by the expression of nicotinic (nAChR) and muscarinic (mAChR) acetylcholine receptors as well as receptors modulating glutamatergic and catecholaminergic afferent signaling. To date, the molecular and cellular relationships between the evolution of tau pathology and nbM neuronal survival remain unknown. To address this knowledge gap, we profiled cholinotrophic pathway genes within nbM neurons immunostained for pS422, a pretangle phosphorylation event preceding tau C-terminal truncation at D421, or dual-labeled for pS422 and TauC3, a later stage tau neo-epitope revealed by this same C-terminal truncation event, via single-population custom microarray analysis. nbM neurons were obtained from postmortem tissues from subjects who died with an antemortem clinical diagnosis of no cognitive impairment (NCI), mild cognitive impairment (MCI), or mild/moderate AD. Quantitative analysis revealed significant downregulation of mRNAs encoding TrkA as well as TrkB, TrkC, and the Trk-mediated downstream pro-survival kinase Akt in pS422+ compared to unlabeled, pS422-negative nbM neurons. In addition, pS422+ neurons displayed a downregulation of transcripts encoding NMDA receptor subunit 2B, metabotropic glutamate receptor 2, D2 dopamine receptor, and β1 adrenoceptor. By contrast, transcripts encoding p75NTR were downregulated in dual-labeled pS422+/TauC3+ neurons. Appearance of the TauC3 epitope was also associated with an upregulation of the α7 nAChR subunit and differential downregulation of the β2 nAChR subunit. Notably, we found that gene expression patterns for each cell phenotype did not differ with clinical diagnosis. However, linear regression revealed that global cognition and Braak stage were predictors of select transcript changes within both unlabeled and pS422+/TauC3- neurons. Taken together, these cell phenotype-specific gene expression profiling data suggest that dysregulation of neurotrophic and neurotransmitter signaling is an early pathogenic mechanism associated with NFT formation in vulnerable nbM neurons and cognitive decline in AD, which may be amenable to therapeutic intervention early in the disease process.

Targeted therapy in patients with PIK3CA-related overgrowth syndrome

CLOVES syndrome (congenital lipomatous overgrowth, vascular malformations, epidermal naevi, scoliosis/skeletal and spinal syndrome) is a genetic disorder that results from somatic, mosaic gain-of-function mutations of the PIK3CA gene, and belongs to the spectrum of PIK3CA-related overgrowth syndromes (PROS). This rare condition has no specific treatment and a poor survival rate. Here, we describe a postnatal mouse model of PROS/CLOVES that partially recapitulates the human disease, and demonstrate the efficacy of BYL719, an inhibitor of PIK3CA, in preventing and improving organ dysfunction. On the basis of these results, we used BYL719 to treat nineteen patients with PROS. The drug improved the disease symptoms in all patients. Previously intractable vascular tumours became smaller, congestive heart failure was improved, hemihypertrophy was reduced, and scoliosis was attenuated. The treatment was not associated with any substantial side effects. In conclusion, this study provides the first direct evidence supporting PIK3CA inhibition as a promising therapeutic strategy in patients with PROS.

APPL1 gates long-term potentiation through its plekstrin homology domain

Hippocampal synaptic plasticity involves both membrane trafficking events and intracellular signaling, but how these are coordinated is far from clear. The endosomal transport of glutamate receptors in and out of the postsynaptic membrane responds to multiple signaling cascades triggered by synaptic activity. In this work, we have identified adaptor protein containing a plekstrin homology domain, phosphotyrosine-binding domain and leucine zipper motif 1 (APPL1) as a crucial element linking trafficking and signaling during synaptic plasticity. We show that APPL1 knockdown specifically impairs PI3K-dependent forms of synaptic plasticity, such as long-term potentiation (LTP) and metabotropic-glutamate-receptor-dependent long-term depression (mGluR-LTD). Indeed, we demonstrate that APPL1 is required for the activation of the phosphatidylinositol triphosphate (PIP3) pathway in response to LTP induction. This requirement can be bypassed by membrane localization of PI3K and is related to phosphoinositide binding. Interestingly, inhibitors of PDK1 (also known as PDPK1) and Akt have no effect on LTP expression. Therefore, we conclude that APPL1 gates PI3K activation at the plasma membrane upon LTP induction, which is then relayed by downstream PIP3 effectors that are different from PDK1 and Akt.

Anti-wrinkle effects of a tuna heart H2O fraction on Hs27 human fibroblasts

With the increase in life expectancy, there is also growing interest in anti-aging treatments and technologies. The development of anti-aging functional drugs for the skin, and foods from natural sources, may offer solutions to this global matter. Aging involves structural, functional and biochemical changes that occur throughout cells and bodily tissues; the amount of hormones secreted from of all human organs, including the skin, decreases over time. Matrix metalloproteinase (MMP) genes (MMP-1 and -8) play an important role in the aging of skin fibroblasts. For example, an increased MMP expression causes accelerated aging and the degradation of skin elasticity-related genes. In the present study, we examined the anti-wrinkle effects of tuna heart extract which are mediated through the inhibition of MMPs in skin cells. Generally, tuna contains high concentrations of selenium and antioxidants, which serve to remove free radicals, and is known to delay skin and body aging. In addition, unsaturated fatty acids in tuna help to maintain the natural glossy look of skin, and increase skin elasticity, providing moisture for dry skin. A recent study confirmed the various bio-effects of boiled tuna extract and muscle. However, bioactivity studies using tuna heart are limited. Thus, in the present study, we obtained extracts and fractions of tuna heart, and examined their effects on Hs27 human fibroblast proliferation using an MTS assay. In addition, we measured procollagen type 1 levels and elastase activity, and performed β-galactosidase staining. We then measured the expression levels of phosphatidylinositol 3-kinase/Akt and MMP-related genes by western blot analysis and RT-PCR. Our results revealed that tuna heart extract decreased MMP expression by upregulating tissue inhibitors of metallopro-teinase-1 (TIMP-1) and decreasing elastase activity, thus exerting anti-aging and anti-wrinkle effects by increasing collagen synthesis and promoting skin fibroblast proliferation. Thus, our data suggest that tuna heart (TH)-H₂O fractions exert anti-wrinkle effects on Hs27 cells.

Imbalanced PTEN and PI3K Signaling Impairs Class Switch Recombination

Class switch recombination (CSR) generates isotype-switched Abs with distinct effector functions. B cells express phosphatase and tensin homolog (PTEN) and multiple isoforms of class IA PI3K catalytic subunits, including p110α and p110δ, whose roles in CSR remain unknown or controversial. In this article, we demonstrate a direct effect of PTEN on CSR signaling by acute deletion of Pten specifically in mature B cells, thereby excluding the developmental impact of Pten deletion. We show that mature B cell-specific PTEN overexpression enhances CSR. More importantly, we establish a critical role for p110α in CSR. Furthermore, we identify a cooperative role for p110α and p110δ in suppressing CSR. Mechanistically, dysregulation of p110α or PTEN inversely affects activation-induced deaminase expression via modulating AKT activity. Thus, our study reveals that a signaling balance between PTEN and PI3K isoforms is essential to maintain normal CSR.

Myristoylated p110α Causes Embryonic Death Due to Developmental and Vascular Defects

The phosphatidylinositol 3-kinase (PI3K) signaling pathway regulates many important cellular functions. The functional impact of deregulating the PIK3CA gene, encoding the p110α catalytic subunit of PI3K, is validated by frequent gain of function mutations in a range of human cancers. We generated a mouse model with an inducible constitutively active form of PI3K. In this model Cre recombinase activates expression of a myristoylated form of p110α (myr-p110α). The myristoylated version of p110α brings the protein to the cytoplasmic side of the cell membrane, which mimics the normal activation mechanism for the p110α catalytic subunit and activates the PI3K enzyme. Constitutively activated PI3K signaling induced by myr-p110α in all cells of the developing mouse caused lethality during embryonic development. Transgenic Cre;myr-p110α heterozygous embryos displayed morphological malformation and poor vascular development with extremely dilated blood vessels and hemorrhage in the embryo and the extraembryonic yolk sac. Previous studies demonstrated that loss of p110α during embryonic development causes angiogenic disruption and here we show that constitutive activation of p110α by gain of function mutation during development also disrupts vasculogenesis/angiogenesis in what appears to be a similar manner. These finding demonstrate the importance of tight regulation of PI3K signaling during embryonic vasculogenesis/angiogenesis..

Krüppel-like factor 14 increases insulin sensitivity through activation of PI3K/Akt signal pathway

Genome-wide association studies (GWAS) have shown that Krüppel-like factor 14 (KLF14) is associated with type 2 diabetes mellitus (T2DM). However, no report has demonstrated a relationship between KLF14 and glucose metabolism. The aim of this study was to determine whether KLF14 is associated with glucose metabolism and insulin signaling in vitro. The mRNA and protein expressions of KLF14 were determined by Real-time PCR and Western blotting. Glucose uptake was assessed by 2-[(3)H]-deoxyglucose (2-DG) uptake. Western blotting was used to identify the activation of insulin signaling proteins. KLF14 mRNA and protein in fat and muscle were significantly decreased in HFD-fed mice, db/db mice and T2DM patients. Overexpression of KLF14 enhanced insulin-stimulated glucose uptake and the activation of Akt kinase in Hepa1-6 cells. The phosphorylation of insulin receptor (InsR), insulin receptor substrate-1(IRS-1), glycogen synthase kinase-3β (GSK-3β) and Akt also elevated significantly by up-regulation of KLF14. KLF14 overexpression in Hepa1-6 cells prevented the inhibition of glucose uptake and Akt phosphorylation induced by high glucose and/or high insulin, or T2DM serum. However, KLF14's ability to increase glucose uptake and Akt activation was significantly attenuated by LY294002, a PI3-kinase inhibitor. These data suggested that KLF14 could increase insulin sensitivity probably through the PI3K/Akt pathway.

The TORC2 component, Sin1, controls migration of anterior mesendoderm during zebrafish gastrulation

TORC2 is a serine-threonine kinase complex conserved through evolution that recently emerged as a new regulator of actin dynamics and cell migration. However, knockout in mice of its core components Sin1 and Rictor is embryonic lethal, which has limited in vivo analyses. Here, we analysed TORC2 function during early zebrafish development, using a morpholino-mediated loss of function of sin1. Sin1 appears required during gastrulation for migration of the prechordal plate, the anterior most mesoderm. In absence of Sin1, cells migrate both slower and less persistently, which can be correlated to a reduction in actin-rich protrusions and a randomisation of the remaining protrusions. These results demonstrate that, as established in vitro, the TORC2 component Sin1 controls actin dynamics and cell migration in vivo. We furthermore establish that Sin1 is required for protrusion formation downstream of PI3K, and is acting upstream of the GTPase Rac1, since expression of an activated form of Rac1 is sufficient to rescue sin1 loss of function.

Loss of anchorage primarily induces non-apoptotic cell death in a human mammary epithelial cell line under atypical focal adhesion kinase signaling

Anchorage dependence of cellular growth and survival prevents inappropriate cell growth or survival in ectopic environments, and serves as a potential barrier to metastasis of cancer cells. Therefore, obtaining a better understanding of anchorage-dependent responses in normal cells is the first step to understand and impede anchorage independence of growth and survival in cancer cells and finally to eradicate cancer cells during metastasis. Anoikis, a type of apoptosis specifically induced by lack of appropriate cell-extracellular matrix adhesion, has been established as the dominant response of normal epithelial cells to anchorage loss. For example, under detached conditions, the untransformed mammary epithelial cell (MEC) line MCF-10 A, which exhibits myoepithelial characteristics, underwent anoikis dependent on classical ERK signaling. On the other hand, recent studies have revealed a variety of phenotypes resulting in cell death modalities distinct from anoikis, such as autophagy, necrosis, and cornification, in detached epithelial cells. In the present study, we characterized detachment-induced cell death (DICD) in primary human MECs immortalized with hTERT (^TertHMECs), which are bipotent progenitor-like cells with a differentiating phenotype to luminal cells. In contrast to MCF-10 A cells, apoptosis was not observed in detached ^TertHMECs; instead, non-apoptotic cell death marked by features of entosis, cornification, and necrosis was observed along with downregulation of focal adhesion kinase (FAK) signaling. Cell death was overcome by anchorage-independent activities of FAK but not PI3K/AKT, SRC, and MEK/ERK, suggesting critical roles of atypical FAK signaling pathways in the regulation of non-apoptotic cell death. Further analysis revealed an important role of TRAIL (tumor necrosis factor (TNF)-related apoptosis-inducing ligand) as a mediator of FAK signaling in regulation of entosis and necrosis and a role of p38 MAPK in the induction of necrosis. Overall, the present study highlighted outstanding cell subtype or differentiation stage specificity in cell death phenotypes induced upon anchorage loss in human MECs.

PI3K in cancer: divergent roles of isoforms, modes of activation and therapeutic targeting

Phosphatidylinositol 3-kinases (PI3Ks) are crucial coordinators of intracellular signalling in response to extracellular stimuli. Hyperactivation of PI3K signalling cascades is one of the most common events in human cancers. In this Review, we discuss recent advances in our knowledge of the roles of specific PI3K isoforms in normal and oncogenic signalling, the different ways in which PI3K can be upregulated, and the current state and future potential of targeting this pathway in the clinic.

Targeting apoptosis pathways in cancer and perspectives with natural compounds from mother nature

Although the incidences are increasing day after day, scientists and researchers taken individually or by research group are trying to fight against cancer by several ways and also by different approaches and techniques. Sesquiterpenes, flavonoids, alkaloids, diterpenoids, and polyphenolic represent a large and diverse group of naturally occurring compounds found in a variety of fruits, vegetables, and medicinal plants with various anticancer properties. In this review, our aim is to give our perspective on the current status of the natural compounds belonging to these groups and discuss their natural sources, their anticancer activity, their molecular targets, and their mechanism of actions with specific emphasis on apoptosis pathways, which may help the further design and conduct of preclinical and clinical trials. Unlike pharmaceutical drugs, the selected natural compounds induce apoptosis by targeting multiple cellular signaling pathways including transcription factors, growth factors, tumor cell survival factors, inflammatory cytokines, protein kinases, and angiogenesis that are frequently deregulated in cancers and suggest that their simultaneous targeting by these compounds could result in efficacious and selective killing of cancer cells. This review suggests that they provide a novel opportunity for treatment of cancer, but clinical trials are still required to further validate them in cancer chemotherapy.

Phosphatidylinositol-3,4,5-trisphosphate: tool of choice for class I PI 3-kinases

Class I PI 3-kinases signal by producing the signaling lipid phosphatidylinositol(3,4,5) trisphosphate, which in turn acts by recruiting downstream effectors that contain specific lipid-binding domains. The class I PI 3-kinases comprise four distinct catalytic subunits linked to one of seven different regulatory subunits. All the class I PI 3-kinases produce the same signaling lipid, PIP3, and the different isoforms have overlapping expression patterns and are coupled to overlapping sets of upstream activators. Nonetheless, studies in cultured cells and in animals have demonstrated that the different isoforms are coupled to distinct ranges of downstream responses. This review focuses on the mechanisms by which the production of a common product, PIP3, can produce isoform-specific signaling by PI 3-kinases.

Assessing the subcellular distribution of oncogenic phosphoinositide 3-kinase using microinjection into live cells

Oncogenic mutations in PIK3CA lead to an increase in intrinsic phosphoinositide kinase activity, but it is thought that increased access of PI3Kα (phosphoinositide 3-kinase α) to its PM (plasma membrane) localized substrate is also required for increased levels of downstream PIP₃/Akt [phosphoinositide-3,4,5-trisphosphate/also called PKB (protein kinase B)] signalling. We have studied the subcellular localization of wild-type and the two most common oncogenic mutants of PI3Kα in cells maintained in growth media, and starved or stimulated cells using a novel method in which PI3Kα is pre-formed as a 1:1 p110α:p85α complex in vitro then introduced into live cells by microinjection. Oncogenic E545K and H1047R mutants did not constitutively interact with membrane lipids in vitro or in cells maintained in 10% (v/v) FBS. Following stimulation of RTKs (receptor tyrosine kinases), microinjected PI3Kα was recruited to the PM, but oncogenic forms of PI3Kα were not recruited to the PM to a greater extent and did not reside at the PM longer than the wild-type PI3Kα. Instead, the E545K mutant specifically bound activated Cdc42 in vitro and microinjection of E545K was associated with the formation of cellular protrusions, providing some preliminary evidence that changes in protein–protein interactions may play a role in the oncogenicity of the E545K mutant in addition to the well-known changes in lipid kinase activity.

Oncogenic forms of PI3Kα (phosphoinositide 3-kinase α) microinjected into live cells are not recruited to the PM (plasma membrane) to a greater extent, and do not reside at the PM longer, than wild-type PI3Kα.

Gene Expression Profiling in Mouse Embryonic Stem Cells Reveals Glycogen Synthase Kinase-3-Dependent Targets of Phosphatidylinositol 3-Kinase and Wnt/β-Catenin Signaling Pathways

Glycogen synthase kinase-3 (Gsk-3) activity is an important regulator of numerous signal transduction pathways. Gsk-3 activity is the sum of two largely redundant proteins, Gsk-3α and Gsk-3β, and in general, Gsk-3 is a negative regulator of cellular signaling. Genetic deletion of both Gsk-3α and Gsk-3β in mouse embryonic stem cells (ESCs) has previously been shown to lead to the constitutive activation of the Wnt/β-catenin signaling pathway. However, in addition to Wnt signaling, all Gsk-3-regulated pathways, such as insulin signaling, are also affected simultaneously in Gsk-3α(-) (/) (-); Gsk-3β(-) (/) (-)ESCs. In an effort to better understand how specific signaling pathways contribute to the global pattern of gene expression in Gsk-3α(-) (/) (-); Gsk-3β(-) (/) (-)ESCs, we compared the gene expression profiles in Gsk-3α(-) (/) (-); Gsk-3β(-) (/) (-) ESCs to mouse ESCs in which either Wnt/β-catenin signaling or phosphatidylinositol 3-kinase (PI3K)-dependent insulin signaling are constitutively active. Our results show that Wnt signaling has a greater effect on up-regulated genes in the Gsk-3α(-) (/) (-); Gsk-3β(-) (/) (-)ESCs, whereas PI3K-dependent insulin signaling is more responsible for the down-regulation of genes in the same cells. These data show the importance of Gsk-3 activity on gene expression in mouse ESCs, and that these effects are due to the combined effects of multiple signaling pathways.

Enzyme activity effects of N-terminal His-tag attached to catalytic sub-unit of phosphoinositide-3-kinase

NTT (N-terminal tags) on the catalytic (p110) sub-unit of PI 3-K (phosphoinositol 3-kinase) have previously been shown to increase cell signalling and oncogenic transformation. Here we test the impact of an NT (N-terminal) His-tag on in vitro lipid and protein kinase activity of all class-1 PI 3-K isoforms and two representative oncogenic mutant forms (E545K and H1047R), in order to elucidate the mechanisms behind this elevated signalling and transformation observed in vivo. Our results show that an NT His-tag has no impact on lipid kinase activity as measured by enzyme titration, kinetics and inhibitor susceptibility. Conversely, the NT His-tag did result in a differential effect on protein kinase activity, further potentiating the elevated protein kinase activity of both the helical domain and catalytic domain oncogenic mutants with relation to p110 phosphorylation. All other isoforms also showed elevated p110 phosphorylation (although not statistically significant). We conclude that the previously reported increase in cell signalling and oncogenic-like transformation in response to p110 NTT is not mediated via an increase in the lipid kinase activity of PI 3-K, but may be mediated by increased p110 autophosphorylation and/or other, as yet unidentified, intracellular protein/protein interactions. We further observe that tagged recombinant protein is suitable for use in in vitro lipid kinase screens to identify PI 3-K inhibitors; however, we recommend that in vivo (including intracellular) experiments and investigations into the protein kinase activity of PI 3-K should be conducted with untagged constructs.

Targeting apoptosis pathways in cancer with alantolactone and isoalantolactone

Alantolactone and isoalantolactone, main bioactive compounds that are present in many medicinal plants such as Inula helenium, L. Inula japonica, Aucklandia lappa, Inula racemosa, and Radix inulae, have been found to have various pharmacological actions including anti-inflammatory, antimicrobial, and anticancer properties, with no significant toxicity. Recently, the anticancer activity of alantolactone and isoalantolactone has been extensively investigated. Here, our aim is to review their natural sources and their anticancer activity with specific emphasis on mechanism of actions, by which these compounds act on apoptosis pathways. Based on the literature and also on our previous results, alantolactone and isoalantolactone induce apoptosis by targeting multiple cellular signaling pathways that are frequently deregulated in cancers and suggest that their simultaneous targeting by these compounds could result in efficacious and selective killing of cancer cells. This review suggests that alantolactone and isoalantolactone are potential promising anticancer candidates, but additional studies and clinical trials are required to determine their specific intracellular sites of actions and derivative targets in order to fully understand the mechanisms of therapeutic effects to further validate in cancer chemotherapy.

Molecular pathways: sterols and receptor signaling in cancer

Accelerated cholesterol and lipid metabolism are the hallmarks of cancer and contribute to malignant transformation due to the obligatory requirement for cholesterol for the function of eukaryotic membranes. To build new membranes and maintain active signaling, cancer cells depend on high intensity of endogenous cholesterol biosynthesis and uptake of lipid particles. This metabolic dependency of cancer cells on cholesterol and other lipids is tightly regulated by the cholesterol homeostasis network, including (i) sterol response element-binding proteins (SREBP), master transcriptional regulators of cholesterol and fatty acid pathway genes; (ii) nuclear sterol receptors (liver X receptors, LXR), which coordinate growth with the availability of cholesterol; and (iii) lipid particle receptors, such as low-density lipid particle (LDL) receptor, providing exogenous sterol and lipids to cancer cells. In addition, activity of oncogenic receptors, such as MUC1 or EGFR, accelerates sterol uptake and biosynthesis. Therefore, a general strategy of reducing the cholesterol pool in cancer cells is challenged by the highly efficient feedback loops compensating for a blockade at a single point in the cholesterol homeostatic network. Besides the well-established structural role of cholesterol in membranes, recent studies have uncovered potent biologic activities of certain cholesterol metabolic precursors and its oxidized derivatives, oxysterols. The former, meiosis-activating sterols, exert effects on trafficking and signaling of oncogenic EGF receptor (EGFR). Cholesterol epoxides, the highly active products of cholesterol oxidation, are being neutralized by the distal sterol pathway enzymes, emopamyl-binding protein (EBP) and dehydrocholesterol-7 reductase (DHCR7). These recently discovered "moonlighting" activities of the cholesterol pathway genes and metabolites expand our understanding of the uniquely conserved roles these sterol molecules play in the regulation of cellular proliferation and in cancer.

Isoalantolactone, a sesquiterpene lactone, induces apoptosis in SGC-7901 cells via mitochondrial and phosphatidylinositol 3-kinase/Akt signaling pathways

Isoalantolactone, a sesquiterpene lactone, possesses anti-fungal as well as cytotoxic properties. In this study, the effects of Isoalantolactone on cell viability, cell cycle, and apoptosis were investigated in human gastric adenocarcinoma SGC-7901 cells. The results demonstrated that Isoalantolactone induced morphological changes and decreased cell viability. Subsequently, we found that Isoalantolactone induced G2/M and S phase arrest, which was associated with a decrease in the expression level of cyclin B1. Apoptosis triggered by Isoalantolactone was visualized using propidium iodide (PI) and Annexin V-FITC/PI staining. Isoalantolactone-induced apoptosis of SGC-7901 cells was associated with the dissipation of mitochondrial membrane potential (ΔΨ m) that was due to the down-regulation of Bcl-2 and up-regulation of Bax that led to the cleavage of caspase-3. Additionally, it was found that Isoalantolactone was involved in the inhibition of phosphorylation of PI3K/Akt. Isoalantolactone-induced cytotoxicity and apoptosis of SGC-7901 cells involve mitochondria-caspase and PI3K/Akt dependent pathways, which gives the rationale for in vivo studies on the utilization of Isoalantolactone as a potential cancer therapeutic compound.

β-Elemene enhances susceptibility to cisplatin in resistant ovarian carcinoma cells via downregulation of ERCC-1 and XIAP and inactivation of JNK

β-Elemene is a promising new plant-derived drug with broad-spectrum anticancer activity. It also increases cisplatin cytotoxicity and enhances cisplatin sensitivity in resistant human carcinoma cells. However, little is known about the mechanism of its action. To explore the potential therapeutic application of β-elemene as a drug-resistance modulator, this study investigated the underlying mechanism of β-elemene activity in cisplatin-resistant ovarian cancer cells. β-Elemene enhanced cisplatin sensitivity to a much greater extent in chemoresistant A2780/CP70 and MCAS human ovarian carcinoma cells compared to the chemosensitive parental cell line A2780. The dose-modifying factors for cisplatin were between 35 and 60 for A2780/CP70 cells and between 1.6 and 2.5 for A2780 cells. In the cisplatin-resistant ovarian carcinoma cells, β-elemene abrogated cisplatin-induced expression of excision repair cross-complementation group-1 (ERCC-1), a marker gene in the nucleotide excision repair pathway that repairs cisplatin-caused DNA damage. In addition, β-elemene not only reduced the level of X-linked inhibitor of apoptosis protein (XIAP), but also downregulated cisplatin-mediated XIAP expression in chemoresistant cells. Furthermore, β-elemene blocked the cisplatin-stimulated increase in the level of phosphorylated c-Jun NH₂-terminal kinase (JNK) in these cells. These novel findings suggest that the β-elemene enhancement of cisplatin sensitivity in human chemoresistant ovarian cancer cells is mediated at least in part through the impairment of DNA repair activity and the activation of apoptotic signaling pathways, thereby making resistant ovarian cancer cells susceptible to cisplatin-induced cell death.

E3 ubiquitin ligase Cbl-b regulates Pten via Nedd4 in T cells independently of its ubiquitin ligase activity

E3 ubiquitin ligase Cbl-b plays a crucial role in T cell activation and tolerance induction. However, the molecular mechanism by which Cbl-b inhibits T cell activation remains unclear. Here, we report that Cbl-b does not inhibit PI3K but rather suppresses TCR/CD28-induced inactivation of Pten. The elevated Akt activity in Cbl-b(-/-) T cells is therefore due to heightened Pten inactivation. Suppression of Pten inactivation in T cells by Cbl-b is achieved by impeding the association of Pten with Nedd4, which targets Pten K13 for K63-linked polyubiquitination. Consistent with this finding, introducing Nedd4 deficiency into Cbl-b(-/-) mice abrogates hyper-T cell responses caused by the loss of Cbl-b. Hence, our data demonstrate that Cbl-b inhibits T cell activation by suppressing Pten inactivation independently of its ubiquitin ligase activity.

Autophosphorylation of serine 608 in the p85 regulatory subunit of wild type or cancer-associated mutants of phosphoinositide 3-kinase does not affect its lipid kinase activity

Background

The α-isoform of the Type 1A Phosphoinositide 3-kinases (PI3Kα) has protein kinase activity as well as phosphoinositide lipid kinase activity. The best described substrate for its protein kinase activity is its regulatory subunit, p85α, which becomes phosphorylated on Serine 608. Phosphorylation of Serine 608 has been reported to down-regulate its lipid kinase activity.

Results

We have assessed whether oncogenic mutants of PI3Kα, which have up-regulated lipid kinase activity, have altered levels of Serine 608 phosphorylation compared to wild type PI3Kα, and whether differential phosphorylation of Serine 608 contributes to increased activity of oncogenic forms of PI3Kα with point mutations in the helical or the kinase domains. Despite markedly increased lipid kinase activity, protein kinase activity was not altered in oncogenic compared to wild type forms of PI3Kα. By manipulating levels of phosphorylation of Serine 608 in vitro, we found no evidence that the protein kinase activity of PI3Kα affects its phosphoinositide lipid kinase activity in either wild-type or oncogenic mutants of PI3Kα.

Conclusions

Phosphorylation of p85α S608 is not a significant regulator of wild-type or oncogenic PI3Kα lipid kinase activity.

Mice expressing activated PI3K rapidly develop advanced colon cancer

Aberrations in the phosphoinositide 3-kinase (PI3K) signaling pathway play a key role in the pathogenesis of numerous cancers by altering cellular growth, metabolism, proliferation, and apoptosis. Mutations in the catalytic domain of PI3K that generate a dominantly active kinase are commonly found in human colorectal cancers and have been thought to drive tumor progression but not initiation. However, the effects of constitutively activated PI3K upon the intestinal mucosa have not been previously studied in animal models. Here, we show that the expression of a dominantly active form of the PI3K protein in the mouse intestine results in hyperplasia and advanced neoplasia. Mice expressing constitutively active PI3K in the epithelial cells of the distal small bowel and colon rapidly developed invasive adenocarcinomas in the colon that spread into the mesentery and adjacent organs. The histologic characteristics of these tumors were strikingly similar to invasive mucinous colon cancers in humans. Interestingly, these tumors formed without a benign polypoid intermediary, consistent with the lack of aberrant WNT signaling observed. Together, our findings indicate a noncanonical mechanism of colon tumor initiation that is mediated through activation of PI3K. This unique model has the potential to further our understanding of human disease and facilitate the development of therapeutics through pharmacologic screening and biomarker identification.

PI3K signaling in the regulation of branching morphogenesis

Branching morphogenesis drives the formation of epithelial organs including the mammary gland, lung, kidney, salivary gland and prostate. Branching at the cellular level also drives development of the nervous and vascular systems. A variety of signaling pathways are orchestrated together to establish the pattern of these branched organs. The phosphoinositide 3-kinase (PI3K) signaling network is of particular interest because of the diverse outcomes it generates, including proliferation, motility, growth, survival and cell death. Here, we focus on the role of the PI3K pathway in the development of branched tissues. Cultured cells, explants and transgenic mice have revealed that the PI3K pathway is critical for the regulation of cell proliferation, apoptosis and motility during branching of tissues.