PI3K-mTOR Signaling Research Articles

Inflammatory cytokines in midbrain periaqueductal gray contribute to diabetic induced pain hypersensitivity through phosphoinositide 3-kinase/protein kinase B/mammalian target of rapamycin signaling pathway.

BackgroundDiabetes-related neuropathic pain frequently occurs, and the underpinning mechanism remains elusive. The periaqueductal gray (PAG) exhibits descending inhibitory effects on central pain transmission. The current work aimed to examine whether inflammatory cytokines regulate mechanical allodynia and thermal hyperalgesia induced by diabetes through the phosphoinositide 3-kinase (PI3K)-mammalian target of rapamycin (mTOR) pathway in the PAG.MethodsStreptozotocin (STZ) was administered intraperitoneally to mimic allodynia and hyperalgesia evoked by diabetes in rats. Behavioral assays were carried out for determining mechanical pain and thermal hypersensitivity. Immunoblot and ELISA were performed to examine PAG protein amounts of interleukin-1β (IL-1β), IL-6, and tumor necrosis factor-α (TNF-α), as well as their corresponding receptors in STZ rats, and the expression of PI3K/protein kinase B (Akt)/mTOR signaling effectors.ResultsIncreased PAG p-PI3K/p-Akt/p-mTOR protein amounts were observed in STZ-induced animals, a PI3K-mTOR pathway inhibition in the PAG attenuated neuropathic pain responses. Moreover, the PAG concentrations of IL-1β, IL-6, and TNF-α and their receptors (namely, IL-1R, IL-6R, and tumor necrosis factor receptor [TNFR] subtype TNFR1, respectively) were increased in the STZ rats. Additionally, inhibiting IL-1R, IL-6R, and TNFR1 ameliorated mechanical allodynia and thermal hyperalgesia in STZ rats, alongside the downregulation of PI3K-mTOR signaling.ConclusionsOverall, the current study suggests that upregulated proinflammatory cytokines and their receptors in the PAG activate PI3K-mTOR signaling, thereby producing a de-inhibition effect on descending pathways in modulating pain transmission, and eventually contributing to neuropathic pain.

Control of adipogenic commitment by a STAT3-VSTM2A axis.

White adipose tissue (WAT) is a dynamic organ that plays crucial roles in controlling metabolic homeostasis. During development and periods of energy excess, adipose progenitors are recruited and differentiate into adipocytes to promote lipid storage capability. The identity of adipose progenitors and the signals that promote their recruitment are still incompletely characterized. We have recently identified V-set and transmembrane domain-containing protein 2A (VSTM2A) as a novel protein enriched in preadipocytes that amplifies adipogenic commitment. Despite the emerging role of VSTM2A in promoting adipogenesis, the molecular mechanisms regulating Vstm2a expression in preadipocytes are still unknown. To define the molecular mechanisms controlling Vstm2a expression, we have treated preadipocytes with an array of compounds capable of modulating established regulators of adipogenesis. Here, we report that Vstm2a expression is positively regulated by PI3K/mTOR and cAMP-dependent signaling pathways and repressed by the MAPK pathway and the glucocorticoid receptor. By integrating the impact of all the molecules tested, we identified signal transducer and activator of transcription 3 (STAT3) as a novel downstream transcription factor affecting Vstm2a expression. We show that activation of STAT3 increased Vstm2a expression, whereas its inhibition repressed this process. In mice, we found that STAT3 phosphorylation is elevated in the early phases of WAT development, an effect that strongly associates with Vstm2a expression. Our findings identify STAT3 as a key transcription factor regulating Vstm2a expression in preadipocytes.NEW & NOTEWORTHY cAMP-dependent and PI3K-mTOR signaling pathways promote the expression of Vstm2a. STAT3 is a key transcription factor that controls Vstm2a expression in preadipocytes. STAT3 is activated in the early phases of WAT development, an effect that strongly associates with Vstm2a expression.

Abstract IA02: The PI3K-mTOR signaling network and tumor cell metabolism

Abstract The mechanistic target of rapamycin (mTOR) complex 1 (mTORC1) is a key signaling node, universal to eukaryotic cells, which links the sensing of nutrients to the coordinated regulation of nutrient metabolism. mTORC1 has the ability to integrate signals from a variety of sources, including intracellular nutrients and secreted growth factors. The activation state of mTORC1 is tightly controlled through a small G protein switch involving the TSC1-TSC2-TBC1D7 complex (the TSC complex) and the Ras-related small G protein Rheb. The direct phosphorylation and inhibition of the TSC complex by the protein kinase Akt provides the major mechanistic link between growth factor signaling and mTORC1. Current evidence indicates that this signal is integrated with amino acid sensing pathways upstream of mTORC1 through independent spatial control over the subcellular localization of the TSC complex and mTORC1 to the surface of the lysosome. This talk will include unpublished data on additional signals that regulate mTORC1 through the TSC-Rheb circuit. Our data suggest that both physiologic growth signals and common oncogenic events in cancer activate mTORC1 through mechanisms leading to dissociation of the TSC protein complex from the lysosomal subpopulation of Rheb, which is required for mTORC1 activation. Physiologic and pathologic activation of PI3K-mTOR signaling results in a shift from catabolic processes to anabolic biosynthetic processes. This pathway acutely responds to feeding and is also frequently and aberrantly activated in human cancers. Through unbiased genomic and metabolomic approaches, we have found that, in addition to its established roles in promoting protein synthesis and inhibiting autophagy, mTORC1 stimulates changes in specific metabolic pathways through transcriptional and post-translational effects on metabolic enzymes. In this manner, mTORC1 serves to link growth signals to metabolic processes that promote the growth of cells, tissues, and tumors, including the de novo synthesis of proteins, lipids, and nucleotides. Research in our lab is focused on understanding the coordinated anabolic program downstream of PI3K-mTOR signaling and identifying metabolic vulnerabilities stemming from uncontrolled pathway activation that can be targeted in tumors. I will discuss our latest data on additional metabolic enzymes under control of the PI3K-mTOR network that contribute to an integrated metabolic program underlying cell growth in both normal and cancer cells. Citation Format: Brendan D. Manning. The PI3K-mTOR signaling network and tumor cell metabolism [abstract]. In: Proceedings of the AACR Special Conference on Targeting PI3K/mTOR Signaling; 2018 Nov 30-Dec 8; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Res 2020;18(10_Suppl):Abstract nr IA02.

NLRC3 inhibits PDGF-induced PASMCs proliferation via PI3K-mTOR pathway.

Few studies about nucleotide-oligomerization domain-like receptor subfamily C3 (NLRC3) in PASMCs have been conducted. This research aimed to investigate the role of NLRC3 on platelet-derived growth factor (PDGF)-induced proliferation of pulmonary artery smooth muscle cells (PASMCs) and its underlying mechanism. We found that the proliferation of PASMCs stimulated with PDGF decreased when phosphoinositide 3-kinase (PI3K) or mammalian target of rapamycin (mTOR) inhibitors pretreatment. Overexpression of NLRC3 inhibited the proliferation of PASMCs and the phosphorylation of PI3K and mTOR while knocking down NLRC3 reversed this effect. Targeted to PI3K or mTOR can also reverse the effect of NLRC3. Activation of PI3K increased the phosphorylation of mTOR while inhibition of PI3K reduced it. Our data suggest that PDGF can induce abnormal proliferation of PASMCs, and NLRC3 suppresses activation of the PI3K-mTOR signaling thus inhibits PASMCs proliferation. These findings unveiled the effect of NLRC3 as an inhibitor of the PI3K-mTOR pathway mediating protection against PASMCs proliferation.

Human liver CD8+ MAIT cells exert TCR/MR1-independent innate-like cytotoxicity in response to IL-15

Mucosal-associated invariant T (MAIT) cells, the most abundant innate-like T cells in the human liver, can be activated by cytokines during viral infection without TCR stimulation. Here, we examined the mechanisms underlying TCR/MR1-independent innate-like cytotoxicity of cytokine-activated liver MAIT cells. We also examined the phenotype and function of MAIT cells from patients with acute viral hepatitis. We obtained liver sinusoidal mononuclear cells from donor liver perfusate during liver transplantation and examined the effect of various cytokines on liver MAIT cells using flow cytometry and invitro cytotoxicity assays. We also obtained peripheral blood and liver-infiltrating T cells from patients with acute hepatitis A (AHA) and examined the phenotype and function of MAIT cells using flow cytometry. IL-15-stimulated MAIT cells exerted granzyme B-dependent innate-like cytotoxicity in the absence of TCR/MR1 interaction. PI3K-mTOR signaling, NKG2D ligation, and CD2-mediated conjugate formation were critically required for this IL-15-induced innate-like cytotoxicity. MAIT cells from patients with AHA exhibited activated and cytotoxic phenotypes with higher NKG2D expression. The innate-like cytotoxicity of MAIT cells was significantly increased in patients with AHA and correlated with serum alanine aminotransferase levels. Taken together, the results demonstrate that liver MAIT cells activated by IL-15 exert NKG2D-dependent innate-like cytotoxicity in the absence of TCR/MR1 engagement. Furthermore, the innate-like cytotoxicity of MAIT cells is associated with liver injury in patients with AHA, suggesting that MAIT cells contribute to immune-mediated liver injury. Immune-mediated liver injury commonly occurs during viral infections of the liver. Mucosal-associated invariant T (MAIT) cells are the most abundant innate-like T cells in the human liver. Herein, we have identified a mechanism by which MAIT cells circumvent conventional T cell receptor interactions to exert cytotoxicity. We show that this innate-like cytotoxicity is increased during acute hepatitis A virus infection and correlates with the degree of hepatocyte injury.

Transcranial focused ultrasound pulsation suppresses pentylenetetrazol induced epilepsy in vivo

BackgroundEpilepsy is a neurological disorder characterized by abnormal neuron discharge, and one-third of epilepsy patients suffer from drug-resistant epilepsy (DRE). The current management for DRE includes epileptogenic lesion resection, disconnection, and neuromodulation. Neuromodulation is achieved through invasive electrical stimulus including deep brain stimulation, vagus nerve stimulation, or responsive neurostimulation (RNS). As an alternative therapy, transcranial focused ultrasound (FUS) can transcranially and non-invasively modulate neuron activity. ObjectiveThis study seeks to verify the use of FUS pulsations to suppress spikes in an acute epileptic small-animal model, and to investigate possible biological mechanisms by which FUS pulsations interfere with epileptic neuronal activity. MethodsThe study used a total of 76 Sprague-Dawley rats. For the epilepsy model, rats were administered pentylenetetrazol (PTZ) to induce acute epileptic-like abnormal neuron discharges, followed by FUS exposure. Various ultrasound parameters were set to test the epilepsy-suppressing effect, while concurrently monitoring and analyzing electroencephalogram (EEG) signals. Animal behavior was monitored and histological examinations were conducted to evaluate the hazard posed by ultrasound exposure and the expression of neuronal activity markers. Western blotting was used to evaluate the correlation between FUS-induced epileptic suppression and the PI3K-mTOR signaling pathway. ResultsWe observed that FUS pulsations effectively suppressed epileptic activity and observed EEG spectrum oscillations; the spike-suppressing effect depended on the selection of ultrasound parameters and highly correlated with FUS exposure level. Expression level changes of c-Fos and GAD65 were confirmed in the cortex and hippocampus, indicating that FUS pulsations deactivated excitatory cells and activated GABAergic terminals. No tissue damage, inflammatory response, or behavioral abnormalities were observed in rats treated with FUS under these exposure parameters. We also found that the FUS pulsations down-regulated the S6 phosphorylation and decreased pAKT expression. ConclusionOur results suggest that pulsed FUS exposure effectively suppresses epileptic spikes in an acute epilepsy animal model, and finds that ultrasound pulsation interferes with neuronal activity and affects the PTZ-induced PI3K-Akt-mTOR pathway, which might help explain the mechanism underlying ultrasound-related epileptic spike control.

Cellular Senescence as a Mechanism and Target in Chronic Lung Diseases.

Cellular senescence is now considered an important driving mechanism for chronic lung diseases, particularly chronic obstructive pulmonary disease (COPD) and idiopathic pulmonary fibrosis. Cellular senescence is due to replicative and stress-related senescence with activation of p53 and p16INK4a, respectively, leading to activation of p21CIP1 and cell cycle arrest. Senescent cells secrete multiple inflammatory proteins known as the senescence-associated secretory phenotype, leading to low-grade chronic inflammation, which further drives senescence. Loss of key antiaging molecules sirtuin-1 and sirtuin-6 may be important in acceleration of aging and arises from oxidative stress reducing phosphatase PTEN (phosphatase tensin homolog), thereby activating PI3K (phosphoinositide-3-kinase) and mTOR (mammalian target of rapamycin). MicroRNA-34a (miR-34a), which is regulated by PI3K-mTOR signaling, plays a pivotal role in reducing sirtuin-1/6, and its inhibition with an antagomir results in their restoration, reducing markers of senescence, reducing senescence-associated secretory phenotype, and reversing cell cycle arrest in epithelial cells from peripheral airways of patients with COPD. miR-570 is also involved in reduction of sirtuin-1 and cellular senescence and is activated by p38 mitogen-activated protein kinase. These miRNAs may be released from cells in extracellular vesicles that are taken up by other cells, thereby spreading senescence locally within the lung but also outside the lung through the circulation; this may account for comorbidities of COPD and other lung diseases. Understanding the mechanisms of cellular senescence may result in new treatments for chronic lung disease, either by inhibiting PI3K-mTOR signaling, by inhibiting specific miRNAs, or by deletion of senescent cells with senolytic therapies, already shown to be effective in experimental lung fibrosis.

Abstract 3464: CBAP: A novel rheostat molecule for regulation of TSC GAP activity and mTORC1 signaling in cancer cells

Abstract The PI3K-mTOR signaling pathway is one of the most frequently dysregulated signaling cascades in cancer. Understanding the molecular wiring of the PI3K-mTOR signaling network and its activation in cancer will improve our understanding of their contribution to cancer pathology and provide novel therapeutic strategies by targeting this network. Our previous works demonstrated that Common receptor Beta chain Associated Protein (CBAP) is required for Jurkat cell leukemogenesis and regulates Akt-dependent TSC2 phosphorylation and lysosomal dissociation of TSC complexes, and in turn enhances mTORC1 signalling and expression of c-MYC and HIF-1a in Jurkat T-ALL leukemic cells. In this report, we tackle the question how TSC/Rheb/mTORC1 pathway is regulated by CBAP via cell-based functional assay, immunoprecipitation and in vitro GTPase assay. Our data revealed that CBAP interacted with TSC2 via tuberin-binding domain and could compete for TSC2 binding with TSC1 and suppressed the GTPase activation activity of TSC1/2 complexes. Akt could also associate with TSC2 complexes and CBAP in both Jurkat and CBAP-knockout Jurkat cells, except that TSC1 could be detected within the complexes only in the absence of CBAP. Moreover, the Rheb-GAP activity of this Akt-associated TSC2 complexes was sensitive to the presence of CBAP and TSC1/2 GAP activity was strongly suppressed by recombinant CBAP proteins in the in vitro reconstituted assay. Finally, a peptide domain of CBAP interacting with TSC2 was mapped and disruption of CBAP-TSC2 interaction by overexpressing this peptide inhibits the Akt/Rheb signal axis and suppresses leukemia cell growth. In summary, our data revealed an important role of the interaction between CBAP and TSC2 proteins in promoting Rheb/mTORC1 signaling activity, and suggested a crucial role of overexpression of CBAP protein in tumor cell proliferation. Citation Format: Jong-Young J. Yen, Yun-Jung Chiang, Wei-Ting Liao, Shih-Hao Wang, Hsin-Fang Yang-Yen. CBAP: A novel rheostat molecule for regulation of TSC GAP activity and mTORC1 signaling in cancer cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 3464.

Abstract LB-287: Combination therapies with CDK4/6 inhibitors to treat KRAS-mutant pancreatic cancer

Abstract Pancreatic ductal adenocarcinoma (PDAC) patients have a dismal five-year survival rate of just eight percent in the advanced metastatic setting. Outcomes with standard chemotherapy regimens are less than ideal; therefore, the development of targeted therapies for the treatment of PDAC is a significant unmet clinical need. The two most frequent genetic events in PDAC (mutational activation of KRAS and loss of the tumor suppressor CDKN2A) converge on activation of the kinases CDK4 and CDK6, which promote G1 cell cycle progression. While clinically relevant agents directly targeting KRAS in PDAC remain elusive, pharmacologic restoration of CDKN2A function by inhibition of CDK4/6 may be an effective anti-KRAS therapeutic strategy. Supporting this hypothesis, we found that CDK4/6 inhibitors (e.g., palbociclib, abemaciclib, lerociclib) elicited single-agent activity in a subset of tested PDAC cell lines. However, using Reverse Phase Protein Array (RPPA), we observed widespread compensatory changes that overcome CDK4/6 inhibition, including increased anti-apoptotic protein expression, PI3K-mTOR and ERK MAPK signaling. Concurrent treatment with the potent and selective ERK1/2 inhibitor (ERKi) SCH772984 reversed resistance and increased sensitivity to palbociclib. This combination caused synergistic reduction in anchorage-dependent cell growth, and increased apoptosis, G1 arrest, and senescence. In an organoid model of pancreatic cancer, cell viability was synergistically reduced and caspase activation enhanced. We have also evaluated the combination of ERKi with palbociclib or the clinical-stage CDK4/6 inhibitor lerociclib (G1T38) in mouse models of PDAC, supporting our initiation of a phase Ib clinical trial of the ERK inhibitor ulixertinib/BVD-523 in combination with palbociclib in advanced metastatic pancreatic cancer (NCT03454035). Next, we sought to identify additional genes that regulate sensitivity to CDK4/6 inhibition. Using a CRISPR/Cas9 loss-of-function screen, we individually silenced expression of 2500 genes from the “druggable genome” in combination with palbociclib in six KRAS-mutant pancreatic and two KRAS-mutant colorectal cancer cell lines. We identified a wide array of genes that enhanced growth suppression in combination, centered around diverse signaling nodes including PI3K-AKT-mTOR signaling, cell cycle regulation and mitosis, SRC family kinase signaling, cell metabolism and biosynthesis, chromosome regulation and maintenance, and DNA damage & repair pathways, suggesting novel small molecule combinations to overcome de novo or acquired CDK4/6 inhibitor resistance in the clinic. We also identified genes whose loss imparts a survival advantage, suggesting possible resistance mechanisms to single-agent CDK4/6 inhibition. In total, these data suggest that CDK4/6 inhibitors alone, or in combination, may benefit PDAC patients clinically. Citation Format: Craig M. Goodwin, Sehrish Javaid, Andrew M. Waters, Bjoern Papke, Runying Yang, Mariaelena Pierobon, Daniel M. Freed, Patrick J. Roberts, Adrienne D. Cox, Kris C. Wood, Emanuel F. Petricoin, Autumn J. McRee, Channing J. Der. Combination therapies with CDK4/6 inhibitors to treat KRAS-mutant pancreatic cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr LB-287.

HER2-L755S mutation induces hyperactive MAPK and PI3K-mTOR signaling, leading to resistance to HER2 tyrosine kinase inhibitor treatment

ABSTRACTL755S, a HER2 kinase domain mutation, is the most common HER2 mutation in breast cancer associated with resistance to anti-HER2 trastuzumab treatment. Here, we showed that HER2-L755S confers hyperactivation of MAPK and PI3K/AKT/mTOR pathways and resistance to both reversible and irreversible HER2 tyrosine kinase inhibitors. We further demonstrated that the HER2 TKIs in combination with MEK inhibitor, AZD6244, or PI3K inhibitor, GDC0941, yield robust killing in HER2-L755S cancer cells, indicating a novel targeted strategy to overcome HER2-L755S resistance to anti-HER2 treatment.

554 Sirolimus gel effectively reduced neurofibromas in neurofibromatosis type 1 in a double-blind, placebo-controlled, randomized clinical trial

NF1 is an autosomal dominant inherited disease caused by the mutation of NF1 gene coding neurofibromin. Although many symptoms with wide variations are recognized, neurofibromas and café-au-lait spots are observed in nearly 100% of patients. Neurofibromin is a tumor suppressor and suppress RAS-MAPK and PI3K-mTOR signaling pathway. Although several clinical trials in NF1 patients have been conducted with RAS-MAPK inhibitors, they are not constantly effective for tumor suppression but resulted in severe side effects. Thus, safer and more effective treatment have been required. It is known that the tumor microenvironment (TME) is involved in the developement of neurofibromas in NF1. In addition to protein synthesis and cell proliferation, mTORC1 is known to be involved in the formation of TME. Therefore, mTORC1 inhibitors seem to be more effective than RAS-MAPK inhibitors. However, systemic administration of sirolimus, an mTORC1 inhibitor, has not been so effective for tumor suppression as expected probably because sirolimus is ineffectively transferred to dermal lesions from blood. We have developed a novel sirolimus gel which delivers sirolimus into the skin lesions with low migration into the blood. Then, we conducted a phase 2, randomized, double-blind clinical trial of the sirolimus 0.4% and 0.2% gel in 18 NF1 patients aged 16 to 70 years old which was approved by our IRB. Tumor size was measured by both CT and ruler to determine the best evaluation method. Statistically significant differences were observed in the sirolimus 0.2% group, and combination of the sirolimus 0.2% and 0.4% group for the change in tumor size by ruler through week 24. Adverse events were mild, and the treatment was not discontinued. As conclusion, topical sirolimus gel treatment was effective and safe for patients with dermal neurofibromas in NF1, which suggest a novel and effective therapeutic modality for NF1.

PDGF Signaling in Primitive Endoderm Cell Survival Is Mediated by PI3K-mTOR Through p53-Independent Mechanism.

Receptor tyrosine kinase signaling pathways are key regulators for the formation of the primitive endoderm (PrE) and the epiblast (Epi) from the inner cell mass (ICM) of the mouse preimplantation embryo. Among them, FGF signaling is critical for PrE cell specification, whereas PDGF signaling is critical for the survival of committed PrE cells. Here, we investigated possible functional redundancies among FGF, PDGF, and KIT signaling and showed that only PDGF signaling is involved in PrE cell survival. In addition, we analyzed the effectors downstream of PDGFRα. Our results suggest that the role of PDGF signaling in PrE cell survival is mediated through PI3K-mTOR and independently from p53. Lastly, we uncovered a role for PI3K-mTOR signaling in the survival of Epi cells. Taken together, we propose that survival of ICM cell lineages relies on the regulation of PI3K-mTOR signaling through the regulation of multiple signaling pathways. Stem Cells 2019;37:888-898.

4E-BP1 Is a Tumor Suppressor Protein Reactivated by mTOR Inhibition in Head and Neck Cancer.

Aberrant activation of the PI3K-mTOR signaling pathway occurs in >80% of head and neck squamous cell carcinomas (HNSCC), and overreliance on this signaling circuit may in turn represent a cancer-specific vulnerability that can be exploited therapeutically. mTOR inhibitors (mTORi) promote tumor regression in genetically defined and chemically induced HNSCC animal models, and encouraging results have been recently reported. However, the mTOR-regulated targets contributing to the clinical response have not yet been identified. Here, we focused on EIF4E-BP1 (4E-BP1), a direct target of mTOR that serves as key effector for protein synthesis. A systematic analysis of genomic alterations in the PIK3CA-mTOR pathway in HNSCC revealed that 4E-BP1 is rarely mutated, but at least one 4E-BP1 gene copy is lost in over 35% of the patients with HNSCC, correlating with decreased 4E-BP1 protein expression. 4E-BP1 gene copy number loss correlated with poor disease-free and overall survival. Aligned with a tumor-suppressive role, 4e-bp1/2 knockout mice formed larger and more lesions in models of HNSCC carcinogenesis. mTORi treatment or conditional expression of a mutant 4E-BP1 that cannot be phosphorylated by mTOR was sufficient to disrupt the translation-initiation complex and prevent tumor growth. Furthermore, CRISPR/Cas9-targeted 4E-BP1 HNSCC cells resulted in reduced sensitivity to mTORi in vitro and in vivo. Overall, these findings indicate that in HNSCC, mTOR persistently restrains 4E-BP1 via phosphorylation and that mTORi can restore the tumor-suppressive function of 4E-BP1. Our findings also support 4E-BP1 expression and phosphorylation status as a mechanistic biomarker of mTORi sensitivity in patients with HNSCC. SIGNIFICANCE: These findings suggest that EIF4E-BP1 acts as a tumor suppressor in HNSCC and that 4E-BP1 dephosphorylation mediates the therapeutic response to mTORi, providing a mechanistic biomarker for future precision oncology trials.

Multi-Parametric Single Cell Profiling Defines Distinct Drug Responses in Healthy Hematological Cell Lineages That Are Retained in Corresponding Malignant Cell Types

▪BackgroundDuring hematopoiesis, multipotent stem cells and pluripotent precursors undergo a complex differentiation program to generate a diverse set of blood cell types with wide-ranging phenotypes and functions that may shape their initial response to therapies. Therefore, innate drug sensitivity in healthy cells provides insight into cell specific responses, aids identification of lineage specific anticancer therapies and reveals off-target effects. To characterize the diversity in drug response and intracellular signal transduction patterns in the major hematopoietic cell types, we simultaneously assessed their sensitivity to 71 small molecules utilizing a multi-parametric flow cytometry assay and mapped onto their proteomic and basal signaling profiles.MethodsHuman BM aspirates and PB samples were collected after written informed consent in compliance with the Declaration of Helsinki. Mononuclear cells from 331 BM aspirates or PB samples were isolated by density gradient centrifugation (Ficoll-Paque Premium; GE Healthcare). Cytometric analyses of drug responses were performed assay using a high throughput flow cytometer (iQue®Screener PLUS) in both 384 well (in 3 healthy samples, 71 drugs) and 96 well plate formats (in 26 samples, 6 drugs) to study drug effects in 5 concentrations (1-10,000 nM). Effect of bortezomib, clofarabine, dexamethasone, omipalisib, venetoclax and navitoclax were assessed on 10 cell populations, namely hematopoietic stem cells (HSCs) (CD34+CD38-), common progenitor cells (CPCs) (CD34+CD38+), monocytes (CD14+), B cells (CD45+CD19+), cytotoxic T cells (CD45+CD3+CD8+), T helper cells (CD45+CD3+CD4+), NK-T cells (CD45+CD3+CD56+), NK cells (CD45+CD56+CD3-), plasma cells (CD138+CD38) and granulocytes (CD45+, SSC++). Mass cytometry (CyTOF) was applied to investigate basal signaling activity of 9 proteins involved in MAPK, JAK-STAT, NF-κB and PI3K-mTOR signaling. Protein abundances in CD3+, CD14+ and CD19+ cells were investigated in six samples using mass spectrometry. To evaluate whether the distinct drug sensitivities detected in the cells of origin could be exploited in the malignant cell counterpart cell, ex vivo drug responses detected in healthy cells were compared to a cohort of 281 primary samples derived from multiple hematological malignancies.ResultsUnsupervised hierarchical clustering of drug response to 71 small molecules identified distinct drug responses in healthy cell subsets based on their cellular lineage. Compared to other cell types, B and NK cells were more sensitive to dexamethasone, venetoclax and midostaurin. Monocytes were more sensitive to trametinib which did not correlate to resting ERK1/2 phosphorylation. Venetoclax exhibited dose dependent cell selectivity to lymphocytes that inversely correlated to STAT3 phosphorylation. Elevated expression of catalase (CAT) and calprotectin (S100A8/S100A9) in monocytes corresponded to their intrinsic resistance to dexamethasone and venetoclax. Comparison of drug responses for six aforementioned drugs in healthy and neoplastic cells across 281 patient samples showed that healthy cell responses are predictive of the corresponding malignant cell response.ConclusionApplying a high content, multi-parametric single-cell assay, we could assess the diversity in drug effects on 10 different cell populations in individual donor samples. Our results demonstrate that cell subtypes are drastically different from each other with respect to protein abundance, signaling profiles and drug-response patterns against a diverse collection of anticancer drugs. Importantly, cell subset specific sensitivity and resistance mechanisms were clearly reflected in their malignant state. Taken together, understanding drug sensitivity in the healthy cell-of-origin provides opportunities to obtain a new level of therapy precision and avoid off-target toxicity. DisclosuresMustjoki:Ariad: Research Funding; Pfizer: Honoraria, Research Funding; Novartis: Honoraria, Research Funding; Celgene: Honoraria; Bristol-Myers Squibb: Honoraria, Research Funding. Wennerberg:Novartis: Research Funding. Porkka:Novartis: Honoraria, Research Funding; Celgene: Honoraria, Research Funding. Gjertsen:Seattle Genetics: Consultancy; BerGenBio: Consultancy; Kinn Therapeutics: Membership on an entity's Board of Directors or advisory committees; Alden Cancer Therapy 2: Equity Ownership; Boehringer Ingelheim: Research Funding; Alden Cancer Therapy 2: Membership on an entity's Board of Directors or advisory committees; Alden Cancer Therapy 2: Patents & Royalties: Alden Cancer Therapy II patent application in relation to CryoIT trial.; Kinn Therapeutics: Equity Ownership; Novartis: Consultancy. Heckman:Novartis: Research Funding; Orion Pharma: Research Funding; Celgene: Research Funding.

Beneficial Effects of Electroacupuncture on Neuropathic Pain Evoked by Spinal Cord Injury and Involvement of PI3K-mTOR Mechanisms.

The purpose of this study was to examine the beneficial effects of electroacupuncture (EA) on neuropathic pain evoked by spinal cord injury (SCI) and determine the underlying molecular mechanisms of these effects. SCI was induced in rats. Behavioral tests were performed to examine pain responses induced by mechanical and thermal stimulation. Western blot analysis was used to measure the protein expression of phosphorylated mammalian target of rapamycin (p-mTOR), mTOR-mediated phosphorylated ribosomal protein S6 kinase beta-1 (p-S6K1), and phosphorylated eukaryotic translation initiation factor 4E-binding protein 1 (p-4E-BP1) in the superficial dorsal horn of the spinal cord. We showed that SCI increased the expression of p-mTOR, p-S6K1, and p-4E-BP1. The EA intervention attenuated the upregulation of mTOR signaling and alleviated mechanical and thermal pain responses in SCI rats. Blocking spinal mTOR by intrathecal injection of rapamycin also inhibited mechanical and thermal pain. In addition, blocking spinal phosphorylated phosphatidylinositide 3-kinase (p-PI3K) pathway attenuated p-mTOR pathways and mechanical and thermal hyperalgesia in SCI rats. EA also decreased the enhanced p-PI3K in the superficial dorsal horn of SCI rats. In conclusion, findings revealed specific signaling pathways that lead to neuropathic pain in response to SCI, including activation of PI3K-mTOR signaling. Further, results link the beneficial role of EA in alleviating SCI-induced neuropathic pain to its effect on these molecular mechanisms.

CC Chemokine Ligand 18 Promotes Cell Proliferation and Metastasis of Urothelial Carcinoma via Activating PI3K/mTOR Signaling in Patient with Renal Transplantation

Objective: The study aimed to investigate the role of chemokine (C-C motif) ligand 18 (CCL18) in the progression of urothelial carcinoma (UC) after renal transplants (RT). Methods: Tissues were collected from 60 patients with UC in which 24 were after RT. The tissues were all obtained from patients after radical cystectomy. Expression levels of CCL18 were examined by immunohistochemistry, RT-polymerase chain ­reaction (RT-PCR), and quantitative RT-PCR, respectively. WST-1 assay was performed to determine proliferative capacity of UC cells. Migration and invasion of UC cells were analyzed by the using of chemotaxis and Transwell system. Western blotting was applied to assess the activation of PI3K-mTOR (Mammalian Target of Rapamycin) signaling. Results: Compared to normal urothelial tissues, the expression levels of CCL18 were significantly increased in tumors of UC, and even more in tumors of UC after RT. Ectopic expression of CCL18 efficiently enhanced the proliferation of UC cells and moreover, exacerbated the migration and invasion of UC cells. Furthermore, overexpressed CCL18 increased the phosphorylation of PI3K, Akt, and mTOR in UC cells, suggesting the hyperactivation of PI3K/Akt/mTOR signaling. Conclusions: The results demonstrate the critical role of CCL18 in the progression of UC, especially in receipt with RT. Our study indicates that CCL18 could serve as a biomarker and therapeutic target in diagnosis of recipients with UC after RT.

Suppression of insulin feedback enhances the efficacy of PI3K inhibitors.

Mutations in PIK3CA, encoding the insulin-activated phosphoinositide-3-kinase (PI3K), and loss of function mutations in PTEN, a phosphatase that degrades the phosphoinositide lipids generated by PI3K, are among the most frequent events in human cancers1,2. Yet, pharmacological inhibition of PI3K has resulted in variable clinical responses, raising the possibility of an inherent mechanism of resistance. Since the PIK3CA-encoded enzyme, p110α, mediates virtually all cellular responses to insulin, targeted inhibition of this enzyme disrupts glucose metabolism in multiple tissue types. For example, blocking insulin signaling promotes glycogen breakdown in the liver and prevents glucose uptake in the skeletal muscle and adipose tissue, resulting in transient hyperglycemia that occurs within a few hours of PI3K inhibition. The effect is usually transient because compensatory insulin release from the pancreas (i.e. insulin feedback) restores normal glucose homeostasis3. However, the hyperglycemia may be exacerbated or prolonged in patients with any degree of insulin resistance and, in these cases, requires discontinuation of therapy3–6. We hypothesized that insulin feedback induced by PI3K inhibitors may be reactivating the PI3K-mTOR signaling axis in tumors, compromising their effectiveness7,8. Here, we show in several model tumors, that systemic glucose-insulin feedback caused by targeted inhibition of this pathway is sufficient to activate PI3K signaling, even in the presence of PI3K inhibitors. We demonstrate that this insulin feedback can be prevented using dietary or pharmaceutical approaches, which greatly enhance the efficacy/toxicity ratios of these compounds. These findings have direct clinical implications for the multiple p110α inhibitors that are in clinical trials and provide a means to significantly increase treatment efficacy for patients with a myriad of tumor types.

PO-505 Targeting PIM kinase to overcome resistance to PI3K-mTOR inhibition in NSCLC

IntroductionNon-small cell lung cancer (NSCLC) is the leading cause of cancer mortality globally, having a 5 year survival rate of less than 15%. PI3K-mTOR signalling has been implicated in various hallmarks of cancer and is frequently dysregulated in NSCLC. Efforts to therapeutically target the PI3K-mTOR pathway have been hampered by the inevitable emergence of drug resistance inhibiting a durable response to treatment. Our group developed NSCLC cell line models of acquired resistance to PI3K-mTOR inhibitor GDC-0980. Resistant cells (H1975GR) were also less sensitive to PI3K-mTOR dual targeting inhibitor, BEZ235 compared to matched parent cells (H1975P) making them an ideal model to identify and interrogate drug resistance mechanisims.Material and methodsThe sensitivity of GDC-0980 resistant cells (H1975GR) versus age-matched parent cells (H1975P) to BEZ235 following a 72 hour treatment was compared using a Cell Titre Blue cell viability assay (n=3). Alterations to the mRNA expression profile of H1975GR versus H1975P were examined using an IL-6/STAT3 signalling-specific RT2 gene profiler array (n=1). Selected genes from the array were validated by SYBR-based qPCR, immunofluorescence (IF) and western blot analysis (n=3–4). 11 miRNAs (regulated by or regulators of c-Myc/PIM) plus housekeeping control miRNAs were quantified in the H1975P/GR model by QPCR. IC50 values of pan-PIM kinase inhibitors AZD1208, IBL101 and novel PI3K/mTOR/PIM inhibitor IBL301 inhibiting growth in H1975P versus H1975GR were compared using the BrdU assay. The effect of these drugs on RTK and c-Myc expression were examined in H1975GR by IF and western blot analysis.Results and discussionsIn-depth characterisation of the H1975GR cells identified activation of several receptor tyrosine kinases (RTKs) including EGFR, IGF1R, EPHA2 and members of the IL-6/STAT3 pathway including c-Myc and PIM1, PIM2 and PIM3 kinases. IL-6/STAT3 overexpression in cancer stimulates angiogenesis, migration, invasiveness, cytokine signalling and notably drug resistance. A miRNA signature of PI3K/mTOR inhibitor resistance was validated which can be used to monitor patients on treatment. IC50 values of IBL301 were significantly less for H1975GR cells (0.02 uM) compared to H1975P cells (0.75 uM) highlighting activated PIM kinase as a mechanism of resistance to PI3K-mTOR inhibition. Targeting PIM kinase in H1975GR cells inhibits activated c-Myc and RTKs.ConclusionDual targeting of both PIM and PI3K-mTOR may provide a more durable response to treatment for patients with NSCLC.

Egr2-independent, Klf1-mediated induction of PD-L1 in CD4+ T cells

Programmed death ligand 1 (PD-L1)-mediated induction of immune tolerance has been vigorously investigated in autoimmunity and anti-tumor immunity. However, details of the mechanism by which PD-L1 is induced in CD4+ T cells are unknown. Here, we revealed the potential function of Klf1 and Egr2-mediated induction of PD-L1 in CD4+ T cells. We focused on the molecules specifically expressed in CD4+CD25−LAG3+ regulatory T cells (LAG3+ Tregs) highly express of PD-L1 and transcription factor Egr2. Although ectopic expression of Egr2 induced PD-L1, a deficiency of Egr2 did not affect its expression, indicating the involvement of another PD-L1 induction mechanism. Comprehensive gene expression analysis of LAG3+ Tregs and in silico binding predictions revealed that Krüppel-like factor 1 (Klf1) is a candidate inducer of the PD-L1 gene (Cd274). Klf1 is a transcription factor that promotes β-globin synthesis in erythroid progenitors, and its role in immunological homeostasis is unknown. Ectopic expression of Klf1 induced PD-L1 in CD4+ T cells through activation of the PI3K-mTOR signaling pathway, independent of STATs signaling and Egr2 expression. Our findings indicate that Klf1 and Egr2 are modulators of PD-L1-mediated immune suppression in CD4+ T cells and might provide new insights into therapeutic targets for autoimmune diseases and malignancies.

Discrete roles and bifurcation of PTEN signaling and mTORC1-mediated anabolic metabolism underlie IL-7-driven B lymphopoiesis

Abstract IL-7 drives early B lymphopoiesis, but the underlying molecular circuits remain poorly understood, especially how Stat5-dependent and independent pathways contribute to this process. Combining transcriptome and proteome analyses and mouse genetic models, we show that IL-7 promotes anabolic metabolism and biosynthetic programs in pro-B cells. IL-7-mediated mTORC1 activation supported cell proliferation and metabolism in a Stat5-independent, Myc-dependent manner, but was largely dispensable for cell survival or Rag1 and Rag2 gene expression. mTORC1 was also required for Myc-driven lymphomagenesis. Importantly, PI3K and mTORC1 had discrete effects on Stat5 signaling and independently controlled B cell development. In fact, PI3K was actively suppressed by PTEN in pro-B cells to ensure proper IL-7R expression, Stat5 activation, heavy chain rearrangement and survival, suggesting the unexpected bifurcation of the classical PI3K-mTOR signaling. Altogether, our integrative analyses establish IL-7R-mTORC1-Myc and PTEN-mediated PI3K suppression as discrete signaling axes driving B cell development, with differential effects on IL-7R-Stat5 signaling.