BACKGROUND: Autoantibodies function as markers of tumorigenesis and have been proposed to enhance early detection of malignancies. We recently reported, using immunoscreening of a T7 complementary DNA (cDNA) library of breast cancer (BC) proteins with sera from patients with BC, the presence of autoantibodies targeting several mitochondrial DNA (mtDNA)-encoded subunits of the electron transport chain (ETC) in complexes I, IV, and V.
METHODS: In this study, we have characterized the role of Mitochondrial-Nuclear Retrograde Regulator 1 (MNRR1, also known as CHCHD2), identified on immunoscreening, in breast carcinogenesis. We assessed the protein as well as transcript levels of MNRR1 in BC tissues and in derived cell lines representing tumors of graded aggressiveness. Mitochondrial function was also assayed and correlated with the levels of MNRR1. We studied the invasiveness of BC derived cells and the effect of MNRR1 levels on expression of genes associated with cell proliferation and migration such as Rictor and PGC-1α. Finally, we manipulated levels of MNRR1 to assess its effect on mitochondria and on some properties linked to a metastatic phenotype.
RESULTS: We identified a nuclear DNA (nDNA)-encoded mitochondrial protein, MNRR1, that was significantly associated with the diagnosis of invasive ductal carcinoma (IDC) of the breast by autoantigen microarray analysis. In focusing on the mechanism of action of MNRR1 we found that its level was nearly twice as high in malignant versus benign breast tissue and up to 18 times as high in BC cell lines compared to MCF10A control cells, suggesting a relationship to aggressive potential. Furthermore, MNRR1 affected levels of multiple genes previously associated with cancer metastasis.
CONCLUSIONS: MNRR1 regulates multiple genes that function in cell migration and cancer metastasis and is higher in cell lines derived from aggressive tumors. Since MNRR1 was identified as an autoantigen in breast carcinogenesis, the present data support our proposal that both mitochondrial autoimmunity and MNRR1 activity in particular are involved in breast carcinogenesis. Virtually all other nuclear encoded genes identified on immunoscreening of invasive BC harbor an MNRR1 binding site in their promoters, thereby placing MNRR1 upstream and potentially making it a novel marker for BC metastasis.

Phosphatases of regenerating liver (PRL-1, PRL-2, and PRL-3, also known as PTP4A1, PTP4A2, and PTP4A3) control magnesium homeostasis through an association with the CNNM magnesium transport regulators. Although high PRL levels have been linked to cancer progression, regulation of their expression is poorly understood. Here we show that modulating intracellular magnesium levels correlates with a rapid change of PRL expression by a mechanism involving its 5'UTR mRNA region. Mutations or CRISPR-Cas9 targeting of the conserved upstream ORF present in the mRNA leader derepress PRL protein synthesis and attenuate the translational response to magnesium levels. Mechanistically, magnesium depletion reduces intracellular ATP but up-regulates PRL protein expression via activation of the AMPK/mTORC2 pathway, which controls cellular energy status. Hence, altered PRL-2 expression leads to metabolic reprogramming of the cells. These findings uncover a magnesium-sensitive mechanism controlling PRL expression, which plays a role in cellular bioenergetics.

Proximity-dependent biotin labeling (BioID) may identify new targets for cancers driven by difficult-to-drug oncogenes such as Ras. Therefore, BioID was used with wild-type (WT) and oncogenic mutant (MT) H-, K-, and N-Ras, identifying known interactors, including Raf and PI3K, as well as a common set of 130 novel proteins proximal to all Ras isoforms. A CRISPR screen of these proteins for Ras dependence identified mTOR, which was also found proximal to MT Ras in human tumors. Oncogenic Ras directly bound two mTOR complex 2 (mTORC2) components, mTOR and MAPKAP1, to promote mTORC2 kinase activity at the plasma membrane. mTORC2 enabled the Ras pro-proliferative cell cycle transcriptional program, and perturbing the Ras-mTORC2 interaction impaired Ras-dependent neoplasia in vivo. Combining proximity-dependent proteomics with CRISPR screening identified a new set of functional Ras-associated proteins, defined mTORC2 as a new direct Ras effector, and offers a strategy for finding new proteins that cooperate with dominant oncogenes.

Mammalian target of rapamycin complex 2 (mTORC2) with its pivotal component rapamycin-insensitive companion of mTOR (RICTOR) is the major regulator of AKT phosphorylation and is increasingly implicated in tumor growth and progression. In cutaneous melanoma, an extremely aggressive and highly metastatic disease, RICTOR overexpression is involved in tumor development and invasiveness. Therefore, we investigated the impact of RICTOR inhibition in melanoma cells in vitro and in vivo with special emphasis on hepatic metastasis. Moreover, our study focused on the interaction of tumor cells and hepatic stellate cells (HSC) which play a crucial role in the hepatic microenvironment. In silico analysis revealed increased RICTOR expression in melanoma cells and tissues and indicated higher expression in advanced melanoma stages and metastases. In vitro, transient RICTOR knock-down via siRNA caused a significant reduction of tumor cell motility. Using a syngeneic murine splenic injection model, a significant decrease in liver metastasis burden was detected in vivo. Moreover, stimulation of melanoma cells with conditioned medium (CM) from activated HSC or hepatocyte growth factor (HGF) led to a significant induction of AKT phosphorylation and tumor cell motility. Blocking of RICTOR expression in cancer cells diminished constitutive and HGF-induced AKT phosphorylation as well as cell motility. Interestingly, RICTOR blockade also led to an abrogation of CM-induced effects on AKT phosphorylation and motility in melanoma cells. In conclusion, these results provide first evidence for a critical role of mTORC2/RICTOR in melanoma liver metastasis via cancer cell/HSC interactions.

Endometriosis is a well‑known risk factor for ovarian cancer. The genetic changes that characterise endometriosis are poorly understood; however, the mechanistic target of rapamycin (mTOR) pathway is involved. In this study, we investigated the expression of key mTOR components in endometriosis and the effects of rapalogues using an endometrioid ovarian carcinoma cell line (MDAH 2774) as an in vitro model. Gene expression of mTOR, DEPTOR, Rictor and Raptor was assessed by qPCR in 24 endometriosis patients and in silico in ovarian cancer patients. Furthermore, the effects of Rapamycin, Everolimus, Deforolimus, Temsirolimus, Resveratrol, and BEZ235 (Dactolisib, a dual kinase inhibitor) on mTOR signalling components was assessed. mTOR showed a significant increase in the expression in endometriosis and ovarian endometrioid adenocarcinoma patients compared to non‑affected controls. DEPTOR, an inhibitor of mTOR, was downregulated in the advanced stages of ovarian cancer (III and IV) compared to earlier stages (I and II). Treatment of MDAH‑2774 cells with the mTOR inhibitors resulted in the significant upregulation of DEPTOR mRNA, whereas treatment with rapamycin and BEZ‑235 (100 nM) resulted in downregulation of the mTOR protein expression after 48 h of treatment. None of the treatments resulted in translocation of mTOR from cytoplasm to nucleus. Upregulation of DEPTOR is a positive prognostic marker in ovarian cancer and is increased in response to mTOR pathway inhibition suggesting that it functions as a tumour suppressor gene in endometrioid ovarian carcinoma. Collectively, our data suggest the mTOR pathway as a potential connection between endometriosis and ovarian cancer and may be a potential target in the treatment of both conditions.

Recent advancement in the field of molecular cancer research has clearly revealed that abnormality of oncogenes or tumor suppressor genes causes tumor progression thorough the promotion of intracellular metabolism. Metabolic reprogramming is one of the strategies for cancer cells to ensure their survival by enabling cancer cells to obtain the macromolecular precursors and energy needed for the rapid growth. However, an orchestration of appropriate metabolic reactions for the cancer cell survival requires the precise mechanism to sense and harness the nutrient in the microenvironment. Mammalian/mechanistic target of rapamycin (mTOR) complexes are known downstream effectors of many cancer-causing mutations, which are thought to regulate cancer cell survival and growth. Recent studies demonstrate the intriguing role of mTOR to achieve the feat through metabolic reprogramming in cancer. Importantly, not only mTORC1, a well-known regulator of metabolism both in normal and cancer cell, but mTORC2, an essential partner of mTORC1 downstream of growth factor receptor signaling, controls cooperatively specific metabolism, which nominates them as an essential regulator of cancer metabolism as well as a promising candidate to garner and convey the nutrient information from the surrounding environment. In this article, we depict the recent findings on the role of mTOR complexes in cancer as a master regulator of cancer metabolism and a potential sensor of nutrients, especially focusing on glucose and amino acid sensing in cancer. Novel and detailed molecular mechanisms that amino acids activate mTOR complexes signaling have been identified. We would also like to mention the intricate crosstalk between glucose and amino acid metabolism that ensures the survival of cancer cells, but at the same time it could be exploitable for the novel intervention to target the metabolic vulnerabilities of cancer cells.

We analyzed the expression of miR-503 in osteosarcoma tissues (OS) and discussed the clinical significance of our findings. To provide a theoretical basis for clinical applications, prognosis prediction and treatment of osteosarcoma, we studied the biological function of miR-503 and its mechanism in MG63 osteosarcoma cells. Real-time polymerase chain reaction (PCR) was used to detect the expression of miR-503 in 45 OS tissues and 20 osteochondroma tumors, analyzing the relationship between clinical pathology and follow-up data. Cox multivariate analysis revealed the clinical and pathological features of the osteosarcoma index and the influence of miR-503 expression on OS prognosis. To observe the effect on cell proliferation and invasion, MG-63 cells were transfected with miR-503. The TargetScan and PicTar bioinformatics method was used to analyze the probable target gene of miR-503 and, combined with the function of the target genes, resulted in a final validation of related pathways. miR-503 was significantly down-regulated in primary OS samples (26/45, 57.8%). The median miR-503 expression level in osteosarcoma was two-fold lower than that in osteochondroma (median expression 6.4 and 13.09, respectively, P< 0.05). The less-expressed miR-503 was associated with Enneking stage (p= 0.004) and invasion (p= 0.015) of OC. Patients with low miR-503 expression had poorer overall survival time. In the multivariate analysis, miR-503 was a significant prognostic factor (P= 0.010). miR-503 can inhibit proliferation and invasion in the MG63 cell line. Using bioinformatics, VEGFA and Rictor were determined to be the likely downstream target genes of miR-503. VEGFA, Rictor, Akt and Erk1/2 were negatively regulated by the overexpression of miR-503. In conclusion, miR-503 has significant tumor-suppressor biological activity and is thus likely to become a new target for the treatment of osteosarcoma.

The mammalian target of rapamycin complex 2 (mTORC2) plays critical roles in various biological processes. To better understand the functions of mTORC2 and the underlying molecular mechanisms, we established a stable cell line with reduced Rictor, a specific component in mTORC2, and investigated the quantitative changes of the cellular proteome. As a result, we observed that 101 proteins were down-regulated and 50 proteins were up-regulated in Rictor knockdown cells. A protein-protein interaction network regulated by Rictor/mTORC2 was established, showing that Rictor/mTORC2 was involved in various cellular processes. Intriguingly, gene ontology analysis indicated that the proteome regulated by Rictor/mTORC2 was significantly involved with cell adhesion. Rictor knockdown affected the expressions of multiple cell adhesion associated molecules, e.g. integrin α-5 (ITGA5), transforming growth factor beta-1-induced transcript 1 protein (TGFB1I1), lysyl oxidase homologue 2 (LOXL2), etc. Further study suggested that Rictor/mTORC2 may regulate cell adhesion and invasion by modulating the expressions of these cell adhesion molecules through AKT. Taken together, this study maps the proteome regulated by Rictor/mTORC2 and reveals its role in promoting renal cancer cell invasion through modulating cell adhesion and migration.

N

PI3K/Akt/mTOR signaling pathway plays a vital role in regulating cell survival, differentiation, metabolism and migration, which is frequently hyperactive in a number of cancers, including esophageal squamous cell carcinoma (ESCC). As the core subunit of mTORC2, Rictor is shown to be amplified in ESCC patients' tissues and plays an important role in regulation of Akt. The objective of this study is to evaluate the effects of Rictor knockdown on cell sensitivity to PI3K inhibitor LY294002 in ESCC cells and ESCC xenografts as well as its mechanisms. We found LY294002 obviously restrained cell proliferation in dose-dependent and time-dependent manners by inhibiting PI3K/Akt/mTOR/p70S6K signaling pathway, whereas triggered mTORC2-medicated phosphorylation of Akt (Ser473)/PRAS40 (Thr246) in ECa109 and EC9706 cells. Stable knockdown of Rictor by shRNA enhanced the inhibitory effects of LY294002 on cell proliferative, migration and colony formation, as well as promoted its effects on cell cycle arrest and cell apoptosis in vitro. Furthermore, stable knockdown of Rictor enhanced the antitumor effects of LY294002 by inhibiting tumor growth and promoting cell apoptosis in vivo. Mechanistic assay revealed that knockdown of Rictor could attenuate LY294002-induced phosphorylation of Akt (Ser473)/PRAS40 (Thr246). Our results provide rationale that combined inhibition of Rictor/mTORC2 and PI3K for the treatment of ESCC.

Reprogramming of mRNA translation has a key role in cancer development and drug resistance

Mantle cell lymphoma (MCL) is a distinct and highly aggressive subtype of B-cell non-Hodgkin lymphoma. Dihydrocelastrol (DHCE) is a dihydro-analog of celastrol, which is isolated from the traditional Chinese medicinal plant Tripterygium wilfordii. The present study aimed to investigate the effects of DHCE treatment on MCL cells, and to determine the mechanism underlying its potent antitumor activity in vitro and in vivo using the Cell Counting kit-8 assay, clonogenic assay, apoptosis assay, cell cycle analysis, immunofluorescence staining, western blotting and tumor xenograft models. The results demonstrated that DHCE treatment exerted minimal cytotoxic effects on normal cells, but markedly suppressed MCL cell proliferation by inducing G0/G1 phase cell cycle arrest, and inhibited MCL cell viability by stimulating apoptosis via extrinsic and intrinsic pathways. In addition, the results revealed that DHCE suppressed cell growth and proliferation by inhibiting mammalian target of rapamycin complex (mTORC)1-mediated phosphorylation of ribosomal protein S6 kinase and eukaryotic initiation factor 4E binding protein. Simultaneously, DHCE induced apoptosis and inhibited cell survival by suppressing mTORC2-mediated phosphorylation of protein kinase B and nuclear factor-κB activity. In addition to in vitro findings, DHCE treatment reduced the MCL tumor burden in a xenograft mouse model, without indications of toxicity. Furthermore, combined treatment with DHCE and bortezomib, a proteasome inhibitor, induced a synergistic cytotoxic effect on MCL cells. These findings indicated that DHCE may have the potential to serve as a novel therapeutic agent for the treatment of MCL through dually inhibiting mTORC1 and mTORC2.

Lymphangioleiomyomatosis (LAM) is a rare progressive cystic lung disease with features of a low-grade neoplasm. It is primarily caused by mutations in TSC1 or TSC2 genes. Sirolimus, an inhibitor of mTOR complex 1 (mTORC1), slows down disease progression in some, but not all patients. Hitherto, other potential therapeutic targets such as mTOR complex 2 (mTORC2) and various metabolic pathways have not been investigated in human LAM tissues. The aim of this study was to assess activities of mTORC1, mTORC2 and various metabolic pathways in human LAM tissues through analysis of protein expression. Immunohistochemical analysis of p-S6 (mTORC1 downstream protein), Rictor (mTORC2 scaffold protein) as well as GLUT1, GAPDH, ATPB, GLS, MCT1, ACSS2 and CPT1A (metabolic pathway markers) were performed on lung tissue from 11 patients with sporadic LAM. Immunoreactivity was assessed in LAM cells with bronchial smooth muscle cells as controls. Expression of p-S6, Rictor, GAPDH, GLS, MCT1, ACSS2 and CPT1A was significantly higher in LAM cells than in bronchial smooth muscle cells (P<.01). No significant differences were found between LAM cells and normal bronchial smooth muscle cells in GLUT1 and ATPB expression. The results are uniquely derived from human tissue and indicate that, in addition to mTORC1, mTORC2 may also play an important role in the pathobiology of LAM. Furthermore, glutaminolysis, acetate utilization and fatty acid β-oxidation appear to be the preferred bioenergetic pathways in LAM cells. mTORC2 and these preferred bioenergetic pathways appear worthy of further study as they may represent possible therapeutic targets in the treatment of LAM.

PURPOSE: It has been reported that PI3K/AKT pathway is altered in various cancers and AKT isoforms specifically regulate cell growth and metastasis of cancer cells; AKT1, but not AKT2, reduces invasion of cancer cells but maintains cancer growth. We propose here a novel mechanism of the tumor suppresser, TIS21
METHODS: Transduction of adenovirus carrying TIS21
RESULTS: We observed that TIS21
CONCLUSIONS: TIS21

Triple-negative breast cancer (TNBC) is characterized by its aggressive behavior, metastasis and lack of targeted therapies. Herein, we discuss the clinical, histopathological and genetic profile of a woman diagnosed with TNBC. Since the patient had no durable response to chemotherapy, a genetic profiling was carried out. Next-generation sequencing analysis of 592 genes showed a missense mutation, p.E545A in PIK3CA, thus the patient was started on the mTOR inhibitor everolimus, in combination with exemestane, which controlled her pain; however, the disease progressed aggressively. More importantly, next-generation sequencing analysis showed a RICTOR gene amplification (eight copies) suggesting that RICTOR promotes the genesis of TNBC. We conclude that determining regulators of RICTOR and furthermore, their inhibitors might decrease cancer cells proliferation rate in patients with TNBC.

The mammalian target of rapamycin (mTOR) pathway is overactivated in thyroid cancer (TC). We previously demonstrated that phospho-mTOR expression is associated with tumor aggressiveness, therapy resistance, and lower mRNA expression of

Previously, BEX family members have been reported to participate in cancer development. However, little is known about the role of BEX4 in lung adenocarcinoma (LAC). Here, we found that BEX4 was over-expressed in LAC tissues compared with adjacent tissues. LAC tissues from metastatic patients exhibited higher expression of BEX4 comparing to those from non-metastatic ones. In vitro, BEX4 ectopic expression accelerated the proliferation of both A549 and H1975 cells. By contrast, knockdown of BEX4 suppressed the proliferation of A549 and H1975 cells. BEX4 positively regulated the expression of OCT4, silencing of which reduced the proliferation of A549 and H1975 cells with over-expressed BEX4. Additionally, mTOR activation, which is frequently observed in LAC, potentiated BEX4 depending on mTORC1 but not mTORC2. BEX4 abundance dictated the sensitivity of A549 and H1975 cells to rapamycin treatment. Our findings reveal that BEX4 is an oncogene in LAC and may contribute to the hyper-active mTOR-induced LAC development.

Presence of perivascular neuroblastoma cells with high expression of hypoxia inducible factor (HIF)-2α correlates with distant metastasis and aggressive disease. Regulation of HIFs are traditionally considered to occur post-translationally, but we have recently shown that HIF-2α is unconventionally regulated also at the transcriptional level in neuroblastoma cells. Regulatory factors binding directly to EPAS1 (encoding HIF-2α) to promote transcription are yet to be defined. Here, we employ the novel CRISPR/Cas9-based engineered DNA-binding molecule-mediated chromatin immunoprecipitation (enChIP) - mass spectrometry (MS) methodology to, in an unbiased fashion, identify proteins that associate with the EPAS1 promoter under normoxic and hypoxic conditions. Our enChIP analysis resulted in 27 proteins binding to the EPAS1 promoter in neuroblastoma cells. In agreement with a general hypoxia-driven downregulation of gene transcription, the majority (24 out of 27) of proteins dissociate from the promoter at hypoxia. Among them were several nucleosome-associated proteins suggesting a general opening of chromatin as one explanation to induced EPAS1 transcription at hypoxia. Of particular interest from the list of released factors at hypoxia was the highly divergent homeobox (HDX) transcription factor, that we show inversely correlates with HIF-2α in neuroblastoma cells. We propose a putative model where HDX negatively regulates EPAS1 expression through a release-of-inhibition mechanism.

The etiopathogenesis of infantile haemangioma has not been well understood, and it is accepted that angiogenic mediator dysregulation is the main contributor to the abnormal haemangioma capillary formation. The role of NDRG1, a hypoxia-inducible protein; FOXOs, which are tumor suppressor proteins; and the mTOR complex 2 pathway in infantile haemangioma have not been studied yet. The purpose of this study was to investigate NDRG1 and FOXO1 expression in the infantile haemangioma and the correlation of these proteins with proliferation and involution. Primary endothelial cells were obtained, with parental agreement, from 12 infantile haemangioma patients during surgery; 6 patients had proliferating infantile haemangiomas and 6 had involuting IHs. We compared the infantile haemangioma tissues and primary endothelial cells with human vein endothelial cells using microarrays, real-time PCR, Western blotting and immunohistochemical staining. Our data indicated that FOXO1 expression was downregulated in proliferating infantile haemangioma tissue. We found that the expression of NDRG1, a molecule upstream of the FOXO1 pathway, increased during haemangioma proliferation. NDRG1 knockdown decreased haemangioma endothelial cell proliferation and downregulated c-MYC oncoprotein levels. Our findings suggest that NDRG1 positively regulates haemangioma proliferation. FOXO1 dysregulation plays an important role in infantile haemangiomas pathogenesis.

BACKGROUND: Although the mechanistic target of rapamycin (MTOR) kinase, included in the mTORC1 and mTORC2 signalling hubs, has been demonstrated to be active in a significant fraction of patients with pancreatic ductal adenocarcinoma (PDAC), the value of the kinase as a therapeutic target needs further clarification.
METHODS: We used Mtor floxed mice to analyse the function of the kinase in context of the pancreas at the genetic level. Using a dual-recombinase system, which is based on the flippase-FRT (Flp-FRT) and Cre-loxP recombination technologies, we generated a novel cellular model, allowing the genetic analysis of MTOR functions in tumour maintenance. Cross-species validation and pharmacological intervention studies were used to recapitulate genetic data in human models, including primary human 3D PDAC cultures.
RESULTS: Genetic deletion of the Mtor gene in the pancreas results in exocrine and endocrine insufficiency. In established murine PDAC cells, MTOR is linked to metabolic pathways and maintains the glucose uptake and growth. Importantly, blocking MTOR genetically as well as pharmacologically results in adaptive rewiring of oncogenic signalling with activation of canonical extracellular signal-regulated kinase and phosphoinositide 3-kinase-AKT pathways. We provide evidence that interfering with such adaptive signalling in murine and human PDAC models is important in a subgroup.
CONCLUSIONS: Our data suggest developing dual MTORC1/TORC2 inhibitor-based therapies for subtype-specific intervention.

Small-molecule inhibitors of the mTORC2 kinase (torkinibs) have shown efficacy in early clinical trials. However, the torkinibs under study also inhibit the other mTOR-containing complex mTORC1. While mTORC1/mTORC2 combined inhibition may be beneficial in cancer cells, recent reports describe compensatory cell survival upon mTORC1 inhibition due to loss of negative feedback on PI3K, increased autophagy, and increased macropinocytosis. Genetic models suggest that selective mTORC2 inhibition would be effective in breast cancers, but the lack of selective small-molecule inhibitors of mTORC2 have precluded testing of this hypothesis to date. Here we report the engineering of a nanoparticle-based RNAi therapeutic that can effectively silence the mTORC2 obligate cofactor Rictor. Nanoparticle-based Rictor ablation in HER2-amplified breast tumors was achieved following intratumoral and intravenous delivery, decreasing Akt phosphorylation and increasing tumor cell killing. Selective mTORC2 inhibition

miR-let-7a is the most widely studied miRNA, whose functions have been well-established by scientists in both carcinogenesis and progression of human cancer, including gastric cancer (GC). However, to date there is a lack of information concerning the relationship between miR-let-7a and cellular autophagy. Using western blotting and immunofluorescence, we determined that upregulation of miR-let-7a led to increased cellular autophagic level, whereas miR-let-7a suppression decreased autophagy activity in GC cells. To further elucidate the mechanisms underlying this, we screened potential targets of miR-let-7a using bioinformatics analyses, validated by a series of assays. Our results indicated that Rptor independent companion of mTOR complex 2 (Rictor) was a direct target of miR-let-7a. In addition, rescue experiments in vitro showed that miR-let-7a promoted cellular autophagic level by inhibiting Rictor expression in GC cells. Furthermore, as an upstream executor of Akt-mTOR signaling pathway, we found that Rictor elaborated its effect on autophagy by phosphorylating Akt and mTOR, and this regulatory process could also be mediated by miR-let-7a. Taken together, our results present a novel role for miR-let-7a in GC which modulates autophagy by targeting Rictor, following the regulation of Akt-mTOR signal pathway.

Hepatocellular carcinoma (HCC) is a deadly malignancy with limited treatment options. Activation of the AKT/mTOR cascade is one of the most frequent events along hepatocarcinogenesis. mTOR is a serine/threonine kinase and presents in two distinct complexes: mTORC1 and mTORC2. While mTORC1 has been extensively studied in HCC, the functional contribution of mTORC2 during hepatocarcinogenesis has not been well characterized, especially in vivo. Pten expression is one of the major mechanisms leading to the aberrant activation of the AKT/mTOR signaling. Here, we show that concomitant downregulation of Pten and upregulation of c-Met occurs in a subset of human HCC, mainly characterized by poor prognosis. Using CRISPR-based gene editing in combination with hydrodynamic injection, Pten was deleted in a subset of mouse hepatocytes (sgPten). We found that loss of Pten synergizes with overexpression of c-Met to promote HCC development in mice (sgPten/c-Met). At the molecular level, sgPten/c-Met liver tumor tissues display increased AKT and mTOR signaling. Using Rictor conditional knockout mice, we demonstrate that sgPten/c-Met-driven HCC development strictly depends on an intact mTORC2 complex. Our findings therefore support the critical role of mTORC2 in hepatocarcinogenesis. sgPten/c-Met mouse model represents a novel valuable system that can be used for the development of targeted therapy against this deadly malignancy.

AIMS: HIF is an important transcription-regulator for adaptation to cellular stress in cells of myeloid origin. Classically, expression and activity of HIF1-α is regulated by oxygen-concentration within cell. However, there exists an alternative regulatory mechanism affecting HIF1-α levels independent of oxygen concentration particularly in inflammatory cells like macrophages. Here we report the mechanism of HIF1-α upregulation in TAMs by Oncostatin-M (OSM) independent of cellular oxygen concentration.
MAIN METHODS: THP-1 derived macrophages were treated with OSM. HIF1-α levels and interaction with pVHL were evaluated via immunoblot-analysis and Co-immunoprecipitation. Translocation of HIF1-α to nucleus was visualized using confocal-microscopy. Fold change in mRNA levels of ARG-1 and COX-2 was analyzed using RT-PCR.
KEY FINDINGS: Current study demonstrates that OSM treatment to TAMs led to an increased expression of HIF1-α under normoxic conditions via activation of mTORC2. This HIF1-α upregulation was dependent on both de novo synthesis of HIF1-α and its enhanced stability due to disruption of its binding to pVHL. Furthermore, we evaluated that OSM not only enhances the expression of HIF1-α but also increases its localization to nucleus where it acts as a transcription factor regulating expression of genes like ARG-1 and COX-2.
SIGNIFICANCE: Inflammation is a critical hallmark of cancer as tumor microenvironment is largely infiltrated with macrophages. These tumor associated macrophages (TAMs) display a M2 skewed phenotype. Many target genes of TAMs are HIF1-α responsive. These TAMs are involved in tumor progression, metastasis and angiogenesis. Targeting of HIF1-α/OSM can lead to devising of better therapeutic strategy against cancer.

Diffuse intrinsic pontine glioma (DIPG) is an incurable childhood brain tumor. The mechanistic target of rapamycin (MTOR), a key oncogene, functions as two distinct signaling complexes, MTORC1 and MTORC2. We set out to determine the preclinical efficacy and mechanism of action of MTOR inhibitors in DIPG. We evaluated the MTORC1 inhibitor everolimus and the MTORC1/2 inhibitor AZD2014 in three patient-derived DIPG cell lines using cell culture models. We created dose-response curves for both compounds. We measured phenotypic effects on cell self-renewal, apoptosis, cell cycle, differentiation, senescence, and autophagy. We assessed the effects of each compound on the AKT pathway. Finally, we measured the efficacy of AZD2014 in combination with radiation therapy (RT) and a panel of FDA-approved chemotherapy drugs. While everolimus showed minimal antitumor efficacy, AZD2014 revealed IC50 levels of 410-552 nM and IC90 levels of 1.30-8.86 µM in the three cell lines. AZD2014 demonstrated increased inhibition of cell self-renewal compared to everolimus. AZD2014 decreased expression of phospho-AKT, while no such effect was noted with everolimus. Direct AKT inhibition showed similar efficacy to AZD2014, and induction of constitutive AKT activity rescued DIPG cells from the effects of AZD2014. AZD2014 exhibited synergistic relationships with both RT and various chemotherapy agents across classes, including the multikinase inhibitor ponatinib. MTORC1/2 inhibition shows antitumor activity in cell culture models of DIPG due to the effect of MTORC2 inhibition on AKT. This strategy should be further assessed for potential incorporation into combinatorial approaches to the treatment of DIPG.

Adult T-cell leukemia (ATL) has a poor prognosis as a result of severe immunosuppression and rapid tumor progression with resistance to conventional chemotherapy. Recent integrated-genome analysis has revealed mutations in many genes involved in the T-cell signaling pathway, suggesting that the aberration of this pathway is an important factor in ATL pathogenesis and ATL-cell proliferation. We screened a siRNA library to examine signaling-pathway functionality and found that the PI3K/Akt/mTOR pathway is critical to ATL-cell proliferation. We therefore investigated the effect of mammalian target of rapamycin (mTOR) inhibitors, including the dual inhibitors PP242 and AZD8055 and the mTORC1 inhibitors rapamycin and everolimus, on human T-cell leukemia virus type 1 (HTLV-1)-infected-cell and ATL-cell lines. Both dual inhibitors inhibited the proliferation of all tested cell lines by inducing G1-phase cell-cycle arrest and subsequent cell apoptosis, whereas the effects of the 2 mTORC1 inhibitors were limited, as they did not induce cell apoptosis. In the ATL-cell lines and in the primary ATL samples, both dual inhibitors inhibited phosphorylation of AKT at serine-473, a target of mTORC2, as well as that of S6K, whereas the mTORC1 inhibitors only inhibited mTORC1. Furthermore, AZD8055 more significantly inhibited the in vivo growth of the ATL-cell xenografts than did everolimus. These results indicate that the PI3K/mTOR pathway is critical to ATL-cell proliferation and might thus be a new therapeutic target in ATL.

Overexpression of Rictor has been demonstrated to result in increased mechanistic target of rapamycin C2 (mTORC2) nucleation and activity leading to tumor growth and increased invasive characteristics in glioblastoma multiforme (GBM). However, the mechanisms regulating Rictor expression in these tumors is not clearly understood. In this report, we demonstrate that Rictor is regulated at the level of mRNA translation via heat-shock transcription factor 1 (HSF1)-induced HuR activity. HuR is shown to directly bind the 3' untranslated region of the Rictor transcript and enhance translational efficiency. Moreover, we demonstrate that mTORC2/AKT signaling activates HSF1 resulting in a feed-forward cascade in which continued mTORC2 activity is able to drive Rictor expression. RNAi-mediated blockade of AKT, HSF1 or HuR is sufficient to downregulate Rictor and inhibit GBM growth and invasive characteristics in vitro and suppress xenograft growth in mice. Modulation of AKT or HSF1 activity via the ectopic expression of mutant alleles support the ability of AKT to activate HSF1 and demonstrate continued HSF1/HuR/Rictor signaling in the context of AKT knockdown. We further show that constitutive overexpression of HuR is able to maintain Rictor expression under conditions of AKT or HSF1 loss. The expression of these components is also examined in patient GBM samples and correlative associations between the relative expression of these factors support the presence of these signaling relationships in GBM. These data support a role for a feed-forward loop mechanism by which mTORC2 activity stimulates Rictor translational efficiency via an AKT/HSF1/HuR signaling cascade resulting in enhanced mTORC2 activity in these tumors.

BACKGROUND & AIMS: Intrahepatic cholangiocarcinoma (ICC) is a lethal malignancy without effective treatment options. MLN0128, a second generation pan-mTOR inhibitor, shows efficacy for multiple tumor types. We evaluated the therapeutic potential of MLN0128 vs. gemcitabine/oxaliplatin in a novel ICC mouse model.
METHODS: We established a novel ICC mouse model via hydrodynamic transfection of activated forms of AKT (myr-AKT) and Yap (YapS127A) protooncogenes (that will be referred to as AKT/YapS127A). Genetic approaches were applied to study the requirement of mTORC1 and mTORC2 in mediating AKT/YapS127A driven tumorigenesis. Gemcitabine/oxaliplatin and MLN0128 were administered in AKT/YapS127A tumor-bearing mice to study their anti-tumor efficacy in vivo. Multiple human ICC cell lines were used for in vitro experiments. Hematoxylin and eosin staining, immunohistochemistry and immunoblotting were applied for the characterization and mechanistic study.
RESULTS: Co-expression of myr-AKT and YapS127A promoted ICC development in mice. Both mTORC1 and mTORC2 complexes were required for AKT/YapS127A ICC development. Gemcitabine/oxaliplatin had limited efficacy in treating late stage AKT/YapS127A ICC. In contrast, partial tumor regression was achieved when MLN0128 was applied in the late stage of AKT/YapS127A cholangiocarcinogenesis. Furthermore, when MLN0128 was administered in the early stage of AKT/YapS127A carcinogenesis, it led to disease stabilization. Mechanistically, MLN0128 efficiently inhibited AKT/mTOR signaling both in vivo and in vitro, inducing strong ICC cell apoptosis and only marginally affecting proliferation.
CONCLUSIONS: This study suggests that mTOR kinase inhibitors may be beneficial for the treatment of ICC, even in tumors that are resistant to standard of care chemotherapeutics, such as gemcitabine/oxaliplatin-based regimens, especially in the subset of tumors exhibiting activated AKT/mTOR cascade. Lay summary: We established a novel mouse model of intrahepatic cholangiocarcinoma (ICC). Using this new preclinical model, we evaluated the therapeutic potential of mTOR inhibitor MLN0128 vs. gemcitabine/oxaliplatin (the standard chemotherapy for ICC treatment). Our study shows the anti-neoplastic potential of MLN0128, suggesting that it may be superior to gemcitabine/oxaliplatin-based chemotherapy for the treatment of ICC, especially in the tumors exhibiting activated AKT/mTOR cascade.

Signal transduction pathways consist of a variety of inter- and intra-cellular molecules. They act as supporting mechanisms for cell survival and homeostasis. Among them, the phosphatidylinositol 3-kinase (PI3K)/tumor suppressor phosphatase and tensin homologue deleted on chromosome ten (PTEN)/protein kinase B (Akt)/mammalian target of rapamycin (mTOR) pathway plays a crucial role in regulating normal cell growth based on growth factor receptors (GFRs) interaction, including epidermal GFR (type II-HER2) and insulin GFR (IGF). mTOR protein acts as a serine-threonine kinase that belongs to the PI3K-related kinase family. It mediates protein and lipid synthesis, mitochondrial metabolism, biogenesis, proliferation and also negatively regulates autophagy. Two distinct multiprotein complexes have been mainly identified and cloned: mTOR complex 1 (mTORC1) and mTOR complex 2 (mTORC2). mTOR is deregulated predominantly due to mutations, deletions, loss of heterozygosity (LOH) or abnormal phosphorylation of the upstream molecules inside the current pathway. Pure mTOR mutations are very rare. Development of specific inhibitors at the basis of targeted therapeutic strategies such as rapamycin (rapalogs) is an evolution in handling patients with mTOR abnormal overactivity. In the current special article we explored the role of the gene deregulation leading to abnormal protein expression in oral cavity squamous cell carcinoma (SCC).

mTORC2 is aberrantly activated in cancer and therefore is considered to be an important therapeutic target. The hedgehog pathway, which is also often hyperactivated, regulates transcription of several genes associated with angiogenesis, metastasis, cellular proliferation and cancer stem cell (CSC) regeneration. However, the contribution of mTORC2 toward hedgehog pathway activity has not been explored yet. Here we have addressed the molecular cross talk between mTORC2 and hedgehog pathway activities in the context of glioblastoma multiforme, a malignant brain tumor using as a model system. We observed that higher mTORC2 activity enhanced the expression of a few hedgehog pathway molecules (Gli1, Gli2 and Ptch1) and amplified its target genes (Cyclin D1, Cyclin D2, Cyclin E, Snail, Slug and VEGF) both in mRNA and protein levels as corroborated by increased metastasis, angiogenesis, cellular proliferation and stem cell regeneration. Inhibition of mTORC2 formation decreased hedgehog pathway activity and attenuated all these above-mentioned events, suggesting their cross talk with each other. Further investigations revealed that mTORC2 inhibited ubiquitination of Gli2 by inactivating GSK3β, and thus it promotes stability to Gli2 and its nuclear translocation. Moreover, enhanced mTORC2 activity led to the increased clonogenic properties and CD133