Therapeutic targeting of the mTOR-signalling pathway in cancer: benefits and limitations

Exogenous APN protects normal tissues from radiation-induced oxidative damage and fibrosis in mice and prostate cancer patients with higher levels of APN have less radiation-induced toxicities

Radiation causes damage to normal tissues that leads to increased oxidative stress, inflammation, and fibrosis, highlighting the need for the selective radioprotection of healthy tissues without hindering radiotherapy effectiveness in cancer. This study shows that adiponectin, an adipokine secreted by adipocytes, protects normal tissues from radiation damage invitro and invivo. Specifically, adiponectin (APN) reduces chronic oxidative stress and fibrosis in irradiated mice. Importantly, APN also conferred no protection from radiation to prostate cancer cells. Adipose tissue is the primary source of circulating endogenous adiponectin. However, this study shows that adipose tissue is sensitive to radiation exposure exhibiting morphological changes and persistent oxidative damage. In addition, radiation results in a significant and chronic reduction in blood APN levels from adipose tissue in mice and human prostate cancer patients exposed to pelvic irradiation. APN levels negatively correlated with bowel toxicity and overall toxicities associated with radiotherapy in prostate cancer patients. Thus, protecting, or modulating APN signaling may improve outcomes for prostate cancer patients undergoing radiotherapy.

Hypoxia-associated autophagy flux dysregulation in human cancers

A general feature of cancer is hypoxia, determined as low oxygen levels. Low oxygen levels may cause cells to alter in ways that contribute to tumor growth and resistance to treatment. Hypoxia leads to variations in cancer cell metabolism, angiogenesis and metastasis. Furthermore, a hypoxic tumor microenvironment might induce immunosuppression. Moreover, hypoxia has the potential to impact cellular processes, such as autophagy. Autophagy refers to the catabolic process by which damaged organelles and toxic macromolecules are broken down. The abnormal activation of autophagy has been extensively recorded in human tumors and it serves as a regulator of cell growth, spread to other parts of the body, and resistance to treatment. There is a correlation between hypoxia and autophagy in human malignancies. Hypoxia can regulate the activity of AMPK, mTOR, Beclin-1, and ATGs to govern autophagy in human malignancies. Furthermore, HIF-1α, serving as an indicator of low oxygen levels, controls the process of autophagy. Hypoxia-induced autophagy has a crucial role in regulating the growth, spread, and resistance to treatment in human malignancies. Hypoxia-induced regulation of autophagy can impact other mechanisms of cell death, such as apoptosis. Chemoresistance and radioresistance have become significant challenges in recent years. Hypoxia-mediated autophagy plays a crucial role in determining the response to these therapeutic treatments.

The PI3K/AKT/mTOR signaling pathway in breast cancer: Review of clinical trials and latest advances

Breast cancer (BC) is the most commonly diagnosed cancer and the leading cause of cancer mortality in women. As the phosphatidylinositol 3-kinase (PI3K) signaling pathway is involved in a wide range of physiological functions of cells including growth, proliferation, motility, and angiogenesis, any alteration in this axis could induce oncogenic features; therefore, numerous preclinical and clinical studies assessed agents able to inhibit the components of this pathway in BC patients. To the best of our knowledge, this is the first study that analyzed all the registered clinical trials investigating safety and efficacy of the PI3K/AKT/mTOR axis inhibitors in BC. Of note, we found that the trends of PI3K inhibitors in recent years were superior as compared with the inhibitors of either AKT or mTOR. However, most of the trials entering phase III and IV used mTOR inhibitors (majorly Everolimus) followed by PI3K inhibitors (majorly Alpelisib) leading to the FDA approval of these drugs in the BC context. Despite favorable efficacies, our analysis shows that the majority of trials are utilizing PI3K pathway inhibitors in combination with hormone therapy and chemotherapy; implying monotherapy cannot yield huge clinical benefits, at least partly, due to the activation of compensatory mechanisms. To emphasize the beneficial effects of these inhibitors in combined-modal strategies, we also reviewed recent studies which investigated the conjugation of nanocarriers with PI3K inhibitors to reduce harmful toxicities, increase the local concentration, and improve their efficacies in the context of BC therapy.

A common molecular and cellular pathway in developing Alzheimer and cancer

Globally cancer and Alzheimer's disease (AD) are two major diseases and still, there is no clearly defined molecular mechanism. There is an opposite relation between cancer and AD which are the proportion of emerging cancer was importantly slower in AD patients, whereas slow emerging AD in patients with cancer. In cancer, regulation of cell mechanisms is interrupted by an increase in cell survival and proliferation, while on the contrary, AD is related to augmented neuronal death, that may be either produced by or associated with amyloid-β (Aβ) and tau deposition. Stated that the probability that disruption of mechanisms takes part in the regulation of cell survival/death and might be implicated in both diseases. The mechanism of actions such as DNA-methylation, genetic polymorphisms, or another mechanism of actions that induce alteration in the action of drugs with significant roles in resolving the finding to repair and live or die might take part in the pathogenesis of these two ailments. The functions of miRNA, p53, Pin1, the Wnt signaling pathway, PI3 KINASE/Akt/mTOR signaling pathway GRK2 signaling pathway, and the pathophysiological role of oxidative stress are presented in this review as potential candidates which hypothetically describe inverse relations between cancer and AD. Innovative materials almost mutual mechanisms in the aetiology of cancer and AD advocates novel treatment approaches. Among these treatment strategies, the most promising use treatment such as tyrosine kinase inhibitor, nilotinib, protein kinase C, and bexarotene.

Caffeic acid 3,4-dihydroxyphenethyl ester prevents colorectal cancer through inhibition of multiple cancer-promoting signal pathways in 1,2-Dimethylhydrazine/dextran sodium sulphate mouse model

OBJECTIVE

To elucidate the potential feature and mechanism of the caffeic acid 3,4-dihydroxyphenethyl ester (CADPE) molecule, which can prevent colorectal cancer (CRC) in the 1,2-Dimethylhydrazine (DMH)/dextran sodium sulphate (DSS)-induced mouse model.

METHODS

Institute of cancer research (ICR) male mice were injected with 20 mg/kg DMH for a week. After that, 2% DSS was administered in the drinking water for another 7 d. The CADPE treatment was given to the DMH/DSS induced male mice at three different periods until their sacrifice. Histopathological examination was used for observing the CRC development at colonic mucosa. Immunohistochemistry (IHC), blood cells smearing and crypt damage scoring methods were used for investigating the anti-inflammation feature of CADPE related to CRC. The reversing targets searching method was applied with artificial intelligence (AI), computer-aided drug designing (CADD) and Ingenuity Pathway Analysis (IPA) techniques for predicting the potential targets and mechanism of CADPE highly related to CRC.

RESULTS

The data indicated that CADPE inhibited CRC tumor development in the colitis-associated DMH/DSS induced mouse model after giving the early treatment. CADPE also impeded the acute inflammation by decreasing the infiltration of neutrophils significantly during the initial stage of CRC development. Finally, our data showed that CADPE prevented CRC by blocking active sites of three pivotal protein targets including epidermal growth factor receptor (EGFR), extracellular signal-regulated kinase (ERK) and mammalian target of rapamycin (mTOR) in two major cancer development pathways.

CONCLUSIONS

CADPE effectively prevented CRC at early stage of tumor germination in the DMH/DSS mouse model highly likely due to its anti-acute inflammation characteristic and the ability of blocking EGFR, ERK and mTOR activities in two highly related CRC developing pathways.

CD133-Dependent Activation of Phosphoinositide 3-Kinase /AKT/Mammalian Target of Rapamycin Signaling in Melanoma Progression and Drug Resistance

Melanoma frequently harbors genetic alterations in key molecules leading to the aberrant activation of PI3K and its downstream pathways. Although the role of PI3K/AKT/mTOR in melanoma progression and drug resistance is well documented, targeting the PI3K/AKT/mTOR pathway showed less efficiency in clinical trials than might have been expected, since the suppression of the PI3K/mTOR signaling pathway-induced feedback loops is mostly associated with the activation of compensatory pathways such as MAPK/MEK/ERK. Consequently, the development of intrinsic and acquired resistance can occur. As a solid tumor, melanoma is notorious for its heterogeneity. This can be expressed in the form of genetically divergent subpopulations including a small fraction of cancer stem-like cells (CSCs) and non-cancer stem cells (non-CSCs) that make the most of the tumor mass. Like other CSCs, melanoma stem-like cells (MSCs) are characterized by their unique cell surface proteins/stemness markers and aberrant signaling pathways. In addition to its function as a robust marker for stemness properties, CD133 is crucial for the maintenance of stemness properties and drug resistance. Herein, the role of CD133-dependent activation of PI3K/mTOR in the regulation of melanoma progression, drug resistance, and recurrence is reviewed.

Low-dose TNF-α promotes angiogenesis of oral squamous cell carcinoma cells via TNFR2/Akt/mTOR axis

OBJECTIVES

To assess the role of TNF-α/TNFR2 axis on promoting angiogenesis in oral squamous cell carcinoma (OSCC) cells and uncover the underlying mechanisms.

MATERIALS AND METHODS

The expression of TNFR2 and CD31 in OSCC tissues was examined; gene expression relationship between TNF-α/TNFR2 and angiogenic markers or signaling molecules was analyzed; the expression of angiogenic markers, signaling molecules, TNFR1, and TNFR2 in TNF-α-stimulated OSCC cells treated with or without TNFR2 neutralizing antibody (TNFR2 Nab) were assessed; the concentration of angiogenic markers in the supernatant of OSCC cells was detected; conditioned mediums of OSCC cells treated with TNF-α or TNF-α + TNFR2 Nab were applied to human umbilical vein endothelial cells (HUVECs), followed by tube formation and cell migration assays.

RESULTS

Significantly elevated expression of TNFR2 and CD31 in OSCC tissues was observed. A positive gene expression correlation was identified between TNF-α/TNFR2 and angiogenic markers or signaling molecules. TNFR2 Nab inhibited the effects of TNF-α on enhancing the expression of angiogenic factors and TNFR2, the phosphorylation of the Akt/mTOR signaling pathway, HUVECs migration, and tube formation.

CONCLUSIONS

TNFR2 Nab counteracts the effect of TNF-α on OSCC cells through the TNFR2/Akt/mTOR axis, indicating that blocking TNFR2 might be a promising strategy against cancer.

Unmasking the tumourigenic role of SIN1/MAPKAP1 in the mTOR complex 2

BACKGROUND

Although the PI3K/AKT/mTOR pathway is one of the most altered pathways in human tumours, therapies targeting this pathway have shown numerous adverse effects due to positive feedback paradoxically activating upstream signaling nodes. The somewhat limited clinical efficacy of these inhibitors calls for the development of novel and more effective approaches for targeting the PI3K pathway for therapeutic benefit in cancer.

MAIN BODY

Recent studies have shown the central role of mTOR complex 2 (mTORC2) as a pro-tumourigenic factor of the PI3K/AKT/mTOR pathway in a number of cancers. SIN1/MAPKAP1 is a major partner of mTORC2, acting as a scaffold and responsible for the substrate specificity of the mTOR catalytic subunit. Its overexpression promotes the proliferation, invasion and metastasis of certain cancers whereas its inhibition decreases tumour growth in vitro and in vivo. It is also involved in epithelial-mesenchymal transition, stress response and lipogenesis. Moreover, the numerous interactions of SIN1 inside or outside mTORC2 connect it with other signaling pathways, which are often disrupted in human tumours such as Hippo, WNT, Notch and MAPK.

CONCLUSION

Therefore, SIN1's fundamental characteristics and numerous connexions with oncogenic pathways make it a particularly interesting therapeutic target. This review is an opportunity to highlight the tumourigenic role of SIN1 across many solid cancers and demonstrates the importance of targeting SIN1 with a specific therapy.

The Role of mTOR Inhibitors after Liver Transplantation for Hepatocellular Carcinoma

Liver transplantation is a treatment option for nonresectable patients with early-stage HCC, with more significant advantages when Milan criteria are fulfilled. An immunosuppressive regimen is required to reduce the risk of graft rejection after transplantation, and CNIs represent the drugs of choice in this setting. However, their inhibitory effect on T-cell activity accounts for a higher risk of tumour regrowth. mTOR inhibitors (mTORi) have been introduced as an alternative immunosuppressive approach to conventional CNI-based regimens to address both immunosuppression and cancer control. The PI3K-AKT-mTOR signalling pathway regulates protein translation, cell growth, and metabolism, and the pathway is frequently deregulated in human tumours. Several studies have suggested the role of mTORi in reducing HCC progression after LT, accounting for a lower recurrence rate. Furthermore, mTOR immunosuppression controls the renal damage associated with CNI exposure. Conversion to mTOR inhibitors is associated with stabilizing and recovering renal dysfunction, suggesting an essential renoprotective effect. Limitations in this therapeutic approach are related to their negative impact on lipid and glucose metabolism as well as on proteinuria development and wound healing. This review aims to summarize the roles of mTORi in managing patients with HCC undergoing LT. Strategies to overcome common adverse effects are also proposed.

Role of mammalian target of rapamycin (mTOR) signalling in oncogenesis

The signalling system known as mammalian target of rapamycin (mTOR) is believed to be required for several biological activities involving cell proliferation. The serine-threonine kinase identified as mTOR recognises PI3K-AKT stress signals. It is well established in the scientific literature that the deregulation of the mTOR pathway plays a crucial role in cancer growth and advancement. This review focuses on the normal functions of mTOR as well as its abnormal roles in cancer development.

Interacting Networks of the Hypothalamic-Pituitary-Ovarian Axis Regulate Layer Hens Performance

Egg production is a vital biological and economic trait for poultry breeding. The 'hypothalamic-pituitary-ovarian (HPO) axis' determines the egg production, which affects the layer hens industry income. At the organism level, the HPO axis is influenced by the factors related to metabolic and nutritional status, environment, and genetics, whereas at the cellular and molecular levels, the HPO axis is influenced by the factors related to endocrine and metabolic regulation, cytokines, key genes, signaling pathways, post-transcriptional processing, and epigenetic modifications. MiRNAs and lncRNAs play a critical role in follicle selection and development, atresia, and ovulation in layer hens; in particular, miRNA is known to affect the development and atresia of follicles by regulating apoptosis and autophagy of granulosa cells. The current review elaborates on the regulation of the HPO axis and its role in the laying performance of hens at the organism, cellular, and molecular levels. In addition, this review provides an overview of the interactive network regulation mechanism of the HPO axis in layer hens, as well as comprehensive knowledge for successfully utilizing their genetic resources.

FGF9 promotes cell proliferation and tumorigenesis in TM3 mouse Leydig progenitor cells

Fibroblast growth factor 9 (FGF9) modulates cell proliferation, differentiation and motility for development and tissue repair in normal cells. Growing evidence shows that abnormal activation of FGF9 signaling is associated with tumor malignancy. We have previously reported that FGF9 increases MA-10 mouse Leydig tumor cell proliferation, in vitro, and tumor growth, in vivo. Also, FGF9 promotes the tumor growth and liver metastasis of mouse Lewis lung cancer cells, in vivo. However, the effects of FGF9 in the early stage of tumorigenesis remains elusive. In this study, TM3 mouse Leydig progenitor cells, that are not tumorigenic in immunocompromised mice, were used as a model cell line to investigate the role of FGF9 in tumorigenesis. The results demonstrated that FGF9 significantly induced cell proliferation and activated the MAPK, PI3K and PLCγ signaling pathways in TM3 cells. The percentage of the cell number in G1 phase was reduced and that in S and G2/M phases was increased after FGF9 stimulation in TM3 cells. Cyclin D1, cyclin A1, CDK2, CDK1, and p21 expressions and the phosphorylation level of Rb were all induced in FGF9-treated TM3 cells. In addition, FGF9 increased the expression of FGF receptor 1-4 in TM3 cells, suggesting the positive feedback loop between FGF9 and FGFRs. Furthermore, in the allograft mouse model, FGF9 promoted the tumorigenesis of TM3 cells characterized by higher expression of tumor markers, such as tumor necrosis factor alpha (TNFα) and α-fetoprotein (AFP), in the subcutaneously inoculated TM3 cell tissue. Conclusively, FGF9 induced cell cycle to increase cell proliferation of TM3 cells through FAK, MAPK, PI3K/Akt and PLCγ signaling pathways, in vitro, and promoted the tumorigenesis of TM3 cell allograft tissue, in vivo, which is a potential marker for tumor as well as a target for cancer therapeutic strategies.

mTOR inhibition attenuates chemosensitivity through the induction of chemotherapy resistant persisters

Chemotherapy can eradicate a majority of cancer cells. However, a small population of tumor cells often survives drug treatments through genetic and/or non-genetic mechanisms, leading to tumor recurrence. Here we report a reversible chemoresistance phenotype regulated by the mTOR pathway. Through a genome-wide CRISPR knockout library screen in pancreatic cancer cells treated with chemotherapeutic agents, we have identified the mTOR pathway as a prominent determinant of chemosensitivity. Pharmacological suppression of mTOR activity in cancer cells from diverse tissue origins leads to the persistence of a reversibly resistant population, which is otherwise eliminated by chemotherapeutic agents. Conversely, activation of the mTOR pathway increases chemosensitivity in vitro and in vivo and predicts better survival among various human cancers. Persister cells display a senescence phenotype. Inhibition of mTOR does not induce cellular senescence per se, but rather promotes the survival of senescent cells through regulation of autophagy and G2/M cell cycle arrest, as revealed by a small-molecule chemical library screen. Thus, mTOR plays a causal yet paradoxical role in regulating chemotherapeutic response; inhibition of the mTOR pathway, while suppressing tumor expansion, facilitates the development of a reversible drug-tolerant senescence state.

Lomitapide, a cholesterol-lowering drug, is an anticancer agent that induces autophagic cell death via inhibiting mTOR

Autophagy is a biological process that maintains cellular homeostasis and regulates the internal cellular environment. Hyperactivating autophagy to trigger cell death has been a suggested therapeutic strategy for cancer treatment. Mechanistic target of rapamycin (mTOR) is a crucial protein kinase that regulates autophagy; therefore, using a structure-based virtual screen analysis, we identified lomitapide, a cholesterol-lowering drug, as a potential mTOR complex 1 (mTORC1) inhibitor. Our results showed that lomitapide directly inhibits mTORC1 in vitro and induces autophagy-dependent cancer cell death by decreasing mTOR signaling, thereby inhibiting the downstream events associated with increased LC3 conversion in various cancer cells (e.g., HCT116 colorectal cancer cells) and tumor xenografts. Lomitapide also significantly suppresses the growth and viability along with elevated autophagy in patient-derived colorectal cancer organoids. Furthermore, a combination of lomitapide and immune checkpoint blocking antibodies synergistically inhibits tumor growth in murine MC38 or B16-F10 preclinical syngeneic tumor models. These results elucidate the direct, tumor-relevant immune-potentiating benefits of mTORC1 inhibition by lomitapide, which complement the current immune checkpoint blockade. This study highlights the potential repurposing of lomitapide as a new therapeutic option for cancer treatment.

mTOR Signaling in the Regulation of CD4+ T Cell Subsets in Periodontal Diseases

Periodontal disease results from the inflammatory infiltration by the microbial community which is marked through tooth mobility and alveolar bone resorption. The inflammation in periodontal disease is mediated by CD4⁺ T cells through cytokine secretion and osteoclastogenetic activity. Historically, the inflammatory model in periodontal disease is described through disruption of the balance between two subsets of T helper cells which are T-helper type 1 (Th1) and T-helper type 2 (Th2). However, more and more studies have found that apart from subsets of helper T cells, regulatory T-cells and Th17 cells are also involved in the pathogenesis of periodontal diseases. Growing evidence proves that helper T cells differentiation, activation, and subset determination are under the strong impact of mTOR signaling. mTOR signaling could promote Th1 and Th17 cell differentiation and inhibit Treg commitment through different mTOR complexes, therefore we anticipate a regulation effect of mTOR signaling on periodontal diseases by regulating CD4⁺ T cell subsets. This review aims to integrate the topical researches about the role of different types of Th cells in the pathogenesis of periodontal diseases, as well as the regulation of mTOR signaling in the specification and selection of Th cell commitment.

Phase I or II Study of Ribociclib in Combination With Topotecan-Temozolomide or Everolimus in Children With Advanced Malignancies: Arms A and B of the AcSé-ESMART Trial

PURPOSE

AcSé-ESMART is a proof-of-concept, phase I or II, platform trial, designed to explore targeted agents in a molecularly enriched cancer population. Arms A and B aimed to define the recommended phase II dose and activity of the CDK4/6 inhibitor ribociclib with topotecan and temozolomide (TOTEM) or everolimus, respectively, in children with recurrent or refractory malignancies.

PATIENTS AND METHODS

Ribociclib was administered orally once daily for 16 days after TOTEM for 5 days (arm A) or for 21 days with everolimus orally once daily continuously in a 28-day cycle (arm B). Dose escalation followed the continuous reassessment method, and activity assessment the Ensign design. Arms were enriched on the basis of molecular alterations in the cell cycle or PI3K/AKT/mTOR pathways.

RESULTS

Thirty-two patients were included, 14 in arm A and 18 in arm B, and 31 were treated. Fourteen patients had sarcomas (43.8%), and 13 brain tumors (40.6%). Main toxicities were leukopenia, neutropenia, and lymphopenia. The recommended phase II dose was ribociclib 260 mg/m2 once a day, temozolomide 100 mg/m2 once a day, and topotecan 0.5 mg/m2 once a day (arm A) and ribociclib 175 mg/m2 once a day and everolimus 2.5 mg/m2 once a day (arm B). Pharmacokinetic analyses confirmed the drug-drug interaction of ribociclib on everolimus exposure. Two patients (14.3%) had stable disease as best response in arm A, and seven (41.2%) in arm B, including one patient with T-acute lymphoblastic leukemia with significant blast count reduction. Alterations considered for enrichment were present in 25 patients (81%) and in eight of nine patients with stable disease; the leukemia exhibited CDKN2A/B and PTEN deficiency.

CONCLUSION

Ribociclib in combination with TOTEM or everolimus was well-tolerated. The observed activity signals initiated a follow-up study of the ribociclib-everolimus combination in a population enriched with molecular alterations within both pathways.

Pharmacometabolomics by NMR in Oncology: A Systematic Review

Pharmacometabolomics (PMx) studies aim to predict individual differences in treatment response and in the development of adverse effects associated with specific drug treatments. Overall, these studies inform us about how individuals will respond to a drug treatment based on their metabolic profiles obtained before, during, or after the therapeutic intervention. In the era of precision medicine, metabolic profiles hold great potential to guide patient selection and stratification in clinical trials, with a focus on improving drug efficacy and safety. Metabolomics is closely related to the phenotype as alterations in metabolism reflect changes in the preceding cascade of genomics, transcriptomics, and proteomics changes, thus providing a significant advance over other omics approaches. Nuclear Magnetic Resonance (NMR) is one of the most widely used analytical platforms in metabolomics studies. In fact, since the introduction of PMx studies in 2006, the number of NMR-based PMx studies has been continuously growing and has provided novel insights into the specific metabolic changes associated with different mechanisms of action and/or toxic effects. This review presents an up-to-date summary of NMR-based PMx studies performed over the last 10 years. Our main objective is to discuss the experimental approaches used for the characterization of the metabolic changes associated with specific therapeutic interventions, the most relevant results obtained so far, and some of the remaining challenges in this area.

Synthesis and biological activity of 1H-imidazo[4,5-f][1,10]phenanthroline as a potential antitumor agent with PI3K/AKT/mTOR signaling

1H-imidazo[4,5-f][1,10]phenanthroline (IPM713) is a type of tricyclic conjugated rigid planar structure with potential medical applications, but its anticancer activity has not yet been fully studied. In the present research, cells from seven different cancer types were used to study the anticancer effect, and IPM713 was found to inhibit the colorectal cancer cell line HCT116 most significantly, with a half maximal inhibitory concentration (IC₅₀) of 1.7 μM. The mechanisms by which IPM713 exerts anti-colorectal cancer activity were studied. IPM713 blocked the cell cycle in G0/G1 phase and induced apoptosis by suppressing the PI3K/AKT/mTOR axis. In addition, an acute toxicity test showed that the median lethal dose (LD₅₀) was above 5000 mg/kg. The findings of this research suggest that IPM713 can interfere with the PI3K/AKT/mTOR signaling pathway and might be a potential therapeutic candidate for the treatment of colorectal cancer.

Role of Inflammatory Mediators, Macrophages, and Neutrophils in Glioma Maintenance and Progression: Mechanistic Understanding and Potential Therapeutic Applications

Simple Summary

The tumor microenvironment is a complex network comprised of neoplastic and a variety of immune cells, proteins, and inflammatory mediators. Previous studies have shown that during cancer progression, diverse inflammatory molecules, either directly or indirectly via recruiting immune cells, support the process of carcinogenesis. The present review focuses on the mechanistic understanding of the oncogenic role of these inflammatory mediators and immune cells, particularly tumor-associated macrophages (TAMs) and tumor-associated neutrophils (TANs) in glioma maintenance and progression. Moreover, the potential therapeutic benefits of targeting inflammatory mediators, immune cells, and associated signaling pathways in glioma genesis have also been discussed.

Abstract

Gliomas are the most common, highly malignant, and deadliest forms of brain tumors. These intra-cranial solid tumors are comprised of both cancerous and non-cancerous cells, which contribute to tumor development, progression, and resistance to the therapeutic regimen. A variety of soluble inflammatory mediators (e.g., cytokines, chemokines, and chemotactic factors) are secreted by these cells, which help in creating an inflammatory microenvironment and contribute to the various stages of cancer development, maintenance, and progression. The major tumor infiltrating immune cells of the tumor microenvironment include TAMs and TANs, which are either recruited peripherally or present as brain-resident macrophages (microglia) and support stroma for cancer cell expansion and invasion. These cells are highly plastic in nature and can be polarized into different phenotypes depending upon different types of stimuli. During neuroinflammation, glioma cells interact with TAMs and TANs, facilitating tumor cell proliferation, survival, and migration. Targeting inflammatory mediators along with the reprogramming of TAMs and TANs could be of great importance in glioma treatment and may delay disease progression. In addition, an inhibition of the key signaling pathways such as NF-κB, JAK/STAT, MAPK, PI3K/Akt/mTOR, and TLRs, which are activated during neuroinflammation and have an oncogenic role in glioblastoma (GBM), can exert more pronounced anti-glioma effects.

Alteration in the mRNA expression profile of the autophagy-related mTOR pathway in schizophrenia patients treated with olanzapine

BACKGROUND

The mammalian target of rapamycin protein (mTOR) signaling pathway is involved in the pathogenesis of schizophrenia and the mechanism of extrapyramidal adverse reactions to antipsychotic drugs, which might be mediated by an mTOR-dependent autophagy impairment. This study aimed to examine the expression of mTOR pathway genes in patients with schizophrenia treated with olanzapine, which is considered an mTOR inhibitor and autophagy inducer.

METHODS

Thirty-two patients with acute schizophrenia who had been treated with olanzapine for four weeks (average dose 14.24 ± 4.35 mg/d) and 32 healthy volunteers were recruited. Before and after olanzapine treatment, the Positive and Negative Syndrome Scale (PANSS) was used to evaluate the symptoms of patients with schizophrenia, and the mRNA expression levels of mTOR pathway-related genes, including MTOR, RICTOR, RAPTOR, and DEPTOR, were detected in fasting venous blood samples from all subjects using real-time quantitative PCR.

RESULTS

The MTOR and RICTOR mRNA expression levels in patients with acute schizophrenia were significantly decreased compared with those of healthy controls and further significantly decreased after four weeks of olanzapine treatment. The DEPTOR mRNA expression levels in patients with acute schizophrenia were not significantly different from those of healthy controls but were significantly increased after treatment. The expression levels of the RAPTOR mRNA were not significantly different among the three groups. The pairwise correlations of MTOR, DEPTOR, RAPTOR, and RICTOR mRNA expression levels in patients with acute schizophrenia and healthy controls were significant. After olanzapine treatment, the correlations between the expression levels of the DEPTOR and MTOR mRNAs and between the DEPTOR and RICTOR mRNAs disappeared.

CONCLUSIONS

Abnormalities in the mTOR pathway, especially DEPTOR and mTORC2, might play important roles in the autophagy mechanism underlying the pathophysiology of schizophrenia and effects of olanzapine treatment.

Bioinformatic Analysis of Two TOR (Target of Rapamycin)-Like Proteins Encoded by Entamoeba histolytica Revealed Structural Similarities with Functional Homologs

The target of rapamycin (TOR), also known as FKBP-rapamycin associated protein (FRAP), is a protein kinase belonging to the PIKK (phosphatidylinositol 3-kinase (PI3K)-related kinases) family. TOR kinases are involved in several signaling pathways that control cell growth and proliferation. Entamoeba histolytica, the protozoan parasite that causes human amoebiasis, contains two genes encoding TOR-like proteins: EhFRAP and EhTOR2. To assess their potential as drug targets to control the cell proliferation of E. histolytica, we studied the structural features of EhFRAP and EhTOR2 using a biocomputational approach. The overall results confirmed that both TOR amoebic homologs share structural similarities with functional TOR kinases, and show inherent abilities to form TORC complexes and participate in protein-protein interaction networks. To our knowledge, this study represents the first in silico characterization of the structure-function relationships of EhFRAP and EhTOR2.

Amino Acid Metabolic Vulnerabilities in Acute and Chronic Myeloid Leukemias

Amino acid (AA) metabolism plays an important role in many cellular processes including energy production, immune function, and purine and pyrimidine synthesis. Cancer cells therefore require increased AA uptake and undergo metabolic reprogramming to satisfy the energy demand associated with their rapid proliferation. Like many other cancers, myeloid leukemias are vulnerable to specific therapeutic strategies targeting metabolic dependencies. Herein, our review provides a comprehensive overview and TCGA data analysis of biosynthetic enzymes required for non-essential AA synthesis and their dysregulation in myeloid leukemias. Furthermore, we discuss the role of the general control nonderepressible 2 (GCN2) and-mammalian target of rapamycin (mTOR) pathways of AA sensing on metabolic vulnerability and drug resistance.

A functional outside-in signaling network of proteoglycans and matrix molecules regulating autophagy

Proteoglycans and selected extracellular matrix constituents are emerging as intrinsic and critical regulators of evolutionarily conversed, intracellular catabolic pathways. Often, these secreted molecules evoke sustained autophagy in a variety of cell types, tissues, and model systems. The unique properties of proteoglycans have ushered in a paradigmatic shift to broaden our understanding of matrix-mediated signaling cascades. The dynamic cellular pathway controlling autophagy is now linked to an equally dynamic and fluid signaling network embedded in a complex meshwork of matrix molecules. A rapidly emerging field of research encompasses multiple matrix-derived candidates, representing a menagerie of soluble matrix constituents including decorin, biglycan, endorepellin, endostatin, collagen VI and plasminogen kringle 5. These matrix constituents are pro-autophagic and simultaneously anti-angiogenic. In contrast, perlecan, laminin α2 chain, and lumican have anti-autophagic functions. Mechanistically, each matrix constituent linked to intracellular catabolic events engages a specific cell surface receptor that often converges on a common core of the autophagic machinery including AMPK, Peg3 and Beclin 1. We consider this matrix-evoked autophagy as non-canonical given that it occurs in an allosteric manner and is independent of nutrient availability or prevailing bioenergetics control. We propose that matrix-regulated autophagy is an important outside-in signaling mechanism for proper tissue homeostasis that could be therapeutically leveraged to combat a variety of diseases.

mTOR regulates GPVI-mediated platelet activation

Background

Due to mTOR (mammalian/mechanistic target of rapamycin) gene-loss mice die during embryonic development, the role of mTOR in platelets has not been evaluated using gene knockout technology.

Methods

A mouse model with megakaryocyte/platelet-specific deletion of mTOR was established, and be used to evaluate the role of mTOR in platelet activation and thrombus formation.

Results

mTOR^−/− platelets were deficient in thrombus formation when grown on low-concentration collagen-coated surfaces; however, no deficiency in thrombus formation was observed when mTOR^−/− platelets were perfused on higher concentration collagen-coated surfaces. In FeCl₃-induced mouse mesenteric arteriole thrombosis models, wild-type (WT) and mTOR^−/− mice displayed significantly different responses to low-extent injury with respect to the ratio of occluded mice, especially within the first 40 min. Additionally, mTOR^−/− platelets displayed reduced aggregation and dense granule secretion (ATP release) in response to low doses of the glycoprotein VI (GPVI) agonist collagen related peptide (CRP) and the protease-activated receptor-4 (PAR4) agonist GYPGKF-NH₂; these deficiencies were overcame by stimulation with higher concentration agonists, suggesting dose dependence of the response. At low doses of GPVI or PAR agonist, the activation of α_IIbβ₃ in mTOR^−/− platelets was reduced. Moreover, stimulation of mTOR^−/− platelets with low-dose CRP attenuated the phosphorylation of S6K1, S6 and Akt Ser473, and increased the phosphorylation of PKCδ Thr505 and PKCε Ser729. Using isoform-specific inhibitors of PKCs (δ, ɛ, and α/β), we established that PKCδ/ɛ, and especially PKCδ but not PKCα/β or PKCθ, may be involved in low-dose GPVI-mediated/mTOR-dependent signaling.

Conclusion

These observations indicate that mTOR plays an important role in GPVI-dependent platelet activation and thrombus formation.

Molecular Pathology of Well-Differentiated Gastro-entero-pancreatic Neuroendocrine Tumors

Well differentiated neuroendocrine tumors (NETs) arising in the gastrointestinal and pancreaticobiliary system are the most common neuroendocrine neoplasms. Studies of the molecular basis of these lesions have identified genetic mutations that predispose to familial endocrine neoplasia syndromes and occur both as germline events and in sporadic tumors. The mutations often involve epigenetic regulators rather than the oncogenes and tumor suppressors that are affected in other malignancies. Somatic copy number alterations and miRNAs have also been implicated in the development and progression of some of these tumors. The molecular profiles differ by location, but many are shared by tumors in other sites, including those outside the gastroenteropancreatic system. The approach to therapy relies on both the neuroendocrine nature of these tumors and the identification of specific alterations that can serve as targets for precision oncologic approaches.

Enhanced Sensitivity to NVP-BEZ235 by Inhibition of p62/SQSTM1 in Human Bladder Cancer KoTCC-1 Cells Both In Vitro and In Vivo

BACKGROUND/AIM

The prognosis of patients with invasive bladder cancer remains poor. The objective of this study was to evaluate the efficacy of NVP-BEZ235 (NVP), a dual PI3K/mTOR inhibitor, combined with the inactivation of p62/SQSTM1 (p62) in a human bladder cancer KoTCC-1 model.

MATERIALS AND METHODS

An expression plasmid with short hairpin RNA targeted against p62 was transfected into KoTCC-1 cells (KoTCC-1/sh-p62). The antitumor effects of NVP on KoTCC-1/sh-p62 were investigated in comparison with those on KoTCC-1 transfected with a control plasmid alone (KoTCC-1/C).

RESULTS

KoTCC-1/sh-p62 showed significantly higher sensitivity to NVP than KoTCC-1/C. Treatment of both cell lines with NVP markedly inactivated the PI3K/Akt/mTOR signaling pathway. However, NVP treatment stimulated the autophagic pathway in KoTCC-1/C, but not in KoTCC-1/sh-p62. Furthermore, compared with KoTCC-1/C, NVP treatment induced apoptosis of KoTCC-1/sh-p62 cells, which was accompanied by significant downregulation of c-IAP-1 and XIAP as well as upregulation of Bax. Moreover, the in vivo growth of KoTCC-1/sh-p62 tumors was significantly suppressed by treatment with NVP compared to KoTCC-1/C tumors.

CONCLUSION

Inhibition of p62 expression combined with NVP may represent an effective therapeutic approach for patients with invasive bladder cancer.

Role of Hypoxia-Mediated Autophagy in Tumor Cell Death and Survival

Programmed cell death or type I apoptosis has been extensively studied and its contribution to the pathogenesis of disease is well established. However, autophagy functions together with apoptosis to determine the overall fate of the cell. The cross talk between this active self-destruction process and apoptosis is quite complex and contradictory as well, but it is unquestionably decisive for cell survival or cell death. Autophagy can promote tumor suppression but also tumor growth by inducing cancer-cell development and proliferation. In this review, we will discuss how autophagy reprograms tumor cells in the context of tumor hypoxic stress. We will illustrate how autophagy acts as both a suppressor and a driver of tumorigenesis through tuning survival in a context dependent manner. We also shed light on the relationship between autophagy and immune response in this complex regulation. A better understanding of the autophagy mechanisms and pathways will undoubtedly ameliorate the design of therapeutics aimed at targeting autophagy for future cancer immunotherapies.

A systems pharmacology approach to identify the autophagy-inducing effects of Traditional Persian medicinal plants

Aging is correlated with several complex diseases, including type 2 diabetes, neurodegeneration diseases, and cancer. Identifying the nature of this correlation and treatment of age-related diseases has been a major subject of both modern and traditional medicine. Traditional Persian Medicine (TPM) embodies many prescriptions for the treatment of ARDs. Given that autophagy plays a critical role in antiaging processes, the present study aimed to examine whether the documented effect of plants used in TPM might be relevant to the induction of autophagy? To this end, the TPM-based medicinal herbs used in the treatment of the ARDs were identified from modern and traditional references. The known phytochemicals of these plants were then examined against literature for evidence of having autophagy inducing effects. As a result, several plants were identified to have multiple active ingredients, which indeed regulate the autophagy or its upstream pathways. In addition, gene set enrichment analysis of the identified targets confirmed the collective contribution of the identified targets in autophagy regulating processes. Also, the protein-protein interaction (PPI) network of the targets was reconstructed. Network centrality analysis of the PPI network identified mTOR as the key network hub. Given the well-documented role of mTOR in inhibiting autophagy, our results hence support the hypothesis that the antiaging mechanism of TPM-based medicines might involve autophagy induction. Chemoinformatics study of the phytochemicals using docking and molecular dynamics simulation identified, among other compounds, the cyclo-trijuglone of Juglans regia L. as a potential ATP-competitive inhibitor of mTOR. Our results hence, provide a basis for the study of TPM-based prescriptions using modern tools in the quest for developing synergistic therapies for ARDs.

Biomarkers and novel therapeutic approaches for diffuse large B-cell lymphoma in the era of precision medicine

Despite the great efforts for better treatment options for diffuse large B-cell lymphoma (DLBCL) (most common form of non-Hodgkin lymphoma, NHL) to treat and prevent relapse, it continues to be a challenge. Here, we present an overview of DLBCL and address the diagnostic assays and molecular techniques used in its diagnosis, role of biomarkers in detection, treatment of early and advanced stage DLBCL, and novel drug regimens. We discuss the significant biomarkers that have emerged as essential tools for stratifying patients according to risk factors and for providing insights into the use of more targeted and individualized therapeutics. We discuss techniques such as gene expression studies, including next-generation sequencing, which have enabled a more understanding of the complex pathogenesis of DLBCL and have helped determine molecular targets for novel therapeutic agents. We examine current treatment approaches, outline the findings of completed clinical trials, and provide updates for ongoing clinical trials. We highlight clinical trials relevant to the significant fraction of DLBCL patients who present with complex cases marked by high relapse rates. Supported by an increased understanding of targetable pathways in DLBCL, clinical trials involving specialized combination therapies are bringing us within reach the promise of an effective cure to DLBCL using precision medicine. Optimization of therapy remains a crucial objective, with the end goal being a balance between high survival rates through targeted and personalized treatment while reducing adverse effects in DLBCL patients of all subsets.

Phase 1 study of mTORC1/2 inhibitor sapanisertib (TAK-228) in advanced solid tumours, with an expansion phase in renal, endometrial or bladder cancer

Background

This Phase 1 dose-escalation/expansion study assessed safety/tolerability of sapanisertib, an oral, highly selective inhibitor of mTORC1/mTORC2, in advanced solid tumours.

Methods

Eligible patients received increasing sapanisertib doses once daily (QD; 31 patients), once weekly (QW; 30 patients), QD for 3 days on/4 days off QW (QD × 3dQW; 33 patients) or QD for 5 days on/2 days off QW (QD × 5dQW; 22 patients). In expansion cohorts, 82 patients with renal cell carcinoma (RCC), endometrial or bladder cancer received sapanisertib 5 mg QD (39 patients), 40 mg QW (26 patients) or 30 mg QW (17 patients).

Results

Maximum tolerated doses of sapanisertib were 6 mg QD, 40 mg QW, 9 mg QD × 3dQW and 7 mg QD × 5dQW. Frequent dose-limiting toxicities (DLTs) included hyperglycaemia, maculo-papular rash (QD), asthenia and stomatitis (QD × 3dQW/QD × 5dQW); expansion phase doses of 5 mg QD and 30 mg QW were selected based on tolerability beyond the DLT evaluation period. One patient with RCC achieved complete response; nine experienced partial responses (RCC: seven patients; carcinoid tumour/endometrial cancer: one patient each). Sapanisertib pharmacokinetics were time-linear and supported multiple dosing. Pharmacodynamic findings demonstrated treatment-related reductions in TORC1/2 biomarkers.

Conclusions

Sapanisertib demonstrated a manageable safety profile, with preliminary antitumour activity observed in RCC and endometrial cancer.

Clinical trial registration

ClinicalTrials.gov, NCT01058707.

Treatment options for localised renal cell carcinoma of the transplanted kidney

Currently, there is no consensus among the transplant community about the treatment of renal cell carcinoma (RCC) of the transplanted kidney. Until recently, graftectomy was universally considered the golden standard, regardless of the characteristics of the neoplasm. Due to the encouraging results observed in native kidneys, conservative options such as nephron-sparing surgery (NSS) (enucleation and partial nephrectomy) and ablative therapy (radiofrequency ablation, cryoablation, microwave ablation, high-intensity focused ultrasound, and irreversible electroporation) have been progressively used in carefully selected recipients with early-stage allograft RCC. Available reports show excellent patient survival, optimal oncological outcome, and preserved renal function with acceptable complication rates. Nevertheless, the rarity and the heterogeneity of the disease, the number of options available, and the lack of long-term follow-up data do not allow to adequately define treatment-specific advantages and limitations. The role of active surveillance and immunosuppression management remain also debated. In order to offer a better insight into this difficult topic and to help clinicians choose the best therapy for their patients, we performed and extensive review of the literature. We focused on epidemiology, clinical presentation, diagnostic work up, staging strategies, tumour characteristics, treatment modalities, and follow-up protocols. Our research confirms that both NSS and focal ablation represent a valuable alternative to graftectomy for kidney transplant recipients with American Joint Committee on Cancer stage T1aN0M0 RCC. Data on T1bN0M0 lesions are scarce but suggest extra caution. Properly designed multi-centre prospective clinical trials are warranted.

Macrophage-derived SPARC Attenuates M2-mediated Pro-tumour Phenotypes

Since the theory of seed and soil was put forward, people have increasingly recognized that the tumour microenvironment is an important regulator of tumour progression and therapeutic response. Among them, M2-type macrophages (M2, as the major macrophage subtype in the tumour foci) have important promoting effects on various biological behaviours. Secreted protein acidic and rich in cysteine (SPARC) is an important anti-tumour component in the microenvironment of gastric cancer. This study shows that macrophages are an important source of the SPARC and that SPARC overexpression in M2 can reduce M2-mediated promoting proliferation, migration and anti-apoptotic effects in gastric cancer. Additionally, the AKT/mTOR signalling pathways may participate in the malignant process.

mTOR Pathway in Gastroenteropancreatic Neuroendocrine Tumor (GEP-NETs)

Gastroenteropancreatic neuroendocrine neoplasms (GEP-NENs) originate from neuroendocrine cells in the gastrointestinal tract. They are heterogeneous, and though initially considered rare tumors, the incidence of GEP-NENs has increased in the last few decades. Therapeutic approaches for the metastatic disease include surgery, radiological intervention by chemoembolisation, radiofrequency ablation, biological therapy in addition to somatostatin analogs, and PRRT therapy (177Lu-DOTATATE). The PI3K-AKT-mTOR pathway is essential in the regulation of protein translation, cell growth, and metabolism. Evidence suggests that the mTOR pathway is involved in malignant progression and resistance to treatment through over-activation of several mechanisms. PI3K, one of the main downstream of the Akt-mTOR axis, is mainly involved in the neoplastic process. This pathway is frequently deregulated in human tumors, making it a central target in the development of new anti-cancer treatments. Recent molecular studies identify potential targets within the PI3K/Akt/mTOR pathway in GEP-NENs. However, the use of target therapy has been known to lead to resistance due to several mechanisms such as feedback activation of alternative pathways, inactivation of protein kinases, and deregulation of the downstream mTOR components. Therefore, the specific role of targeted drugs for the management of GEP-NENs is yet to be well-defined. The variable clinical presentation of advanced neuroendocrine tumors is a significant challenge for designing studies. This review aims to highlight the role of the PI3K/Akt/mTOR pathway in the development of neuroendocrine tumors and further specify its potential as a therapeutic target in advanced stages.

Histone Deacetylase Inhibitors in Tumor Immunotherapy

BACKGROUND

With an increasing understanding of the antitumor immune response, considerable progress has been made in the field of tumor immunotherapy in the last decade. Inhibition of histone deacetylases represents a new strategy in tumor therapy and histone deacetylase inhibitors have been recently developed and validated as potential antitumor drugs. In addition to the direct antitumor effects, histone deacetylase inhibitors have been found to have the ability to improve tumor recognition by immune cells that may contribute to their antitumor activity. These immunomodolutory effects are desirable, and their in-depth comprehension will facilitate the design of novel regimens with improved clinical efficacy.

OBJECTIVE

Our goal here is to review recent developments in the application of histone deacetylase inhibitors as immune modulators in cancer treatment.

METHODS

Systemic compilation of the relevant literature in this field.

RESULTS & CONCLUSION

In this review, we summarize recent advances in the understanding of how histone deacetylase inhibitors alter immune process and discuss their effects on various cytokines. We also discuss the challenges to optimize the use of these inhibitors as immune modulators in cancer treatment. Information gained from this review will be valuable to this field and may be helpful for designing tumor immunotherapy trials involving histone deacetylase inhibitors.

Therapeutic inhibition of Mcl-1 blocks cell survival in estrogen receptor-positive breast cancers

Cancers often overexpress anti-apoptotic Bcl-2 proteins for cell death evasion, a recognized hallmark of cancer progression. While estrogen receptor (ER)-α+ breast cancers express high levels of three anti-apoptotic Bcl-2 family members (Bcl-2, Bcl-xL, and Mcl-1), pharmacological inhibition of Bcl-2 and/or Bcl-xL fails to induce cell death in ERα+ breast cancer cell lines, due to rapid and robust Mcl-1 upregulation. The mechanisms of acute Mcl-1 upregulation in response to Bcl-2/Bcl-xL inhibition remain undefined in in ERα+ breast cancers. We report here that blockade of Bcl-2 or Bcl-xL, alone or together, rapidly induced mTOR signaling in ERα+ breast cancer cells, rapidly increasing cap-dependent Mcl-1 translation. Cells treated with a pharmacological inhibitor of cap-dependent translation, or with the mTORC1 inhibitor RAD001/everolimus, displayed reduced protein levels of Mcl-1 under basal conditions, and failed to upregulate Mcl-1 protein expression following treatment with ABT-263, a pharmacological inhibitor of Bcl-2 and Bcl-xL. Although treatment with ABT-263 alone did not sustain apoptosis in tumor cells in culture or in vivo, ABT-263 plus RAD001 increased apoptosis to a greater extent than either agent used alone. Similarly, combined use of the selective Mcl-1 inhibitor VU661013 with ABT-263 resulted in tumor cell apoptosis and diminished tumor growth in vivo. These findings suggest that rapid Mcl-1 translation drives ABT-263 resistance, but can be combated directly using emerging Mcl-1 inhibitors, or indirectly through existing and approved mTOR inhibitors.

Low expression of SPARC in gastric cancer-associated fibroblasts leads to stemness transformation and 5-fluorouracil resistance in gastric cancer

Background

The aim of the present study was to clarify the correlations between SPARC expression in gastric cancer-associated fibroblasts (GCAFs) and the prognosis of patients with gastric cancer and to elucidate the role of GCAF-derived SPARC in stemness transformation and 5-fluorouracil resistance in gastric cancer.

Methods

One hundred ninety-two patients were enrolled in the present study. SPARC expression levels were evaluated by immunohistochemical staining. Primary GCAFs were obtained and cultured from cancer patients for in vitro study, and a lentivirus infection method was employed to knock down SPARC expression in GCAFs. The stemness phenotype and 5-fluorouracil (5-FU) response of gastric cancer cells were assessed via a 3D co-culture model. The apoptotic status and stemness alterations were monitored by flow cytometry and western blotting. Additionally, label-free quantification proteomics was used to identify the differentially expressed proteins and potential pathways in gastric cancer cells treated with GCAF-derived SPARC.

Results

Low expression of GCAF-derived SPARC was associated with decreased differentiation and reduced 5-year overall survival and was an independent predictive factor for prognosis in gastric cancer. The 3D tumour growth and 5-FU resistance abilities of gastric cancer cells were elevated after treatment with GCAFs with SPARC knockdown relative to these abilities in negative control cells. Additionally, suppressing SPARC expression in GCAFs facilitated the phenotypic alteration of gastric cancer cells towards CD44⁺/CD24⁻ cancer stem cell (CSC)-like cells. Quantification proteomics analysis revealed that the differentially expressed proteins in gastric cancer cells were mainly involved in the AKT/mTOR and MEK/ERK signalling pathways.

Conclusions

SPARC expression in GCAFs is a useful prognostic factor in patients with gastric cancer. Low expression of GCAF-derived SPARC can lead to CSC transformation and 5-FU resistance. Additionally, the AKT/mTOR and MEK/ERK signalling pathways may participate in the malignant process.

Electronic supplementary material

The online version of this article (10.1186/s12935-019-0844-8) contains supplementary material, which is available to authorized users.

p53 Promotes Cancer Cell Adaptation to Glutamine Deprivation by Upregulating Slc7a3 to Increase Arginine Uptake

Cancer cells heavily depend on the amino acid glutamine to meet the demands associated with growth and proliferation. Due to the rapid consumption of glutamine, cancer cells frequently undergo glutamine starvation in vivo. We and others have shown that p53 is a critical regulator in metabolic stress resistance. To better understand the molecular mechanisms by which p53 activation promotes cancer cell adaptation to glutamine deprivation, we identified p53-dependent genes that are induced upon glutamine deprivation by using RNA-seq analysis. We show that Slc7a3, an arginine transporter, is significantly induced by p53. We also show that increased intracellular arginine levels following glutamine deprivation are dependent on p53. The influx of arginine has minimal effects on known metabolic pathways upon glutamine deprivation. Instead, we found arginine serves as an effector for mTORC1 activation to promote cell growth in response to glutamine starvation. Therefore, we identify a p53-inducible gene that contributes to the metabolic stress response.

Alzheimer's Disease and Cancer: When Two Monsters Cannot Be Together

Alzheimer's disease (AD) and cancer are among the leading causes of human death around the world. While neurodegeneration is the main feature of AD, the most important characteristic of malignant tumors is cell proliferation, placing these two diseases in opposite sides of cell division spectrum. Interestingly, AD and cancer's pathologies consist of a remarkable common feature and that is the presence of active cell cycle in both conditions. In an in vitro model of primary adult neuronal culture, we previously showed that treating cell with beta amyloid forced neurons to start a cell cycle. Instead of cell division, however, neuronal cell cycle was aborted and a massive neurodegeneration was left behind as the consequence. A high level of cell cycle entry, which is a requirement for cancer pathogenesis, was reported in clinically diagnosed cases of AD, leading to neurodegeneration. The diverse clinical manifestation of a similar etiology, have puzzled researchers for many years. In fact, the evidence showed an inverse association between AD and cancer prevalence, suggesting that switching pathogenesis toward AD protects patients against cancer and vice versa. In this mini review, we discussed the possibility of involvement of cell proliferation and survival dysregulation as the underlying mechanism of neurodegeneration in AD, and the leading event to develop both disorders' pathology. As examples, the role of phosphoinositide 3 kinase/Akt/ mammalian target of rapamycin (PI3K/Akt/mTOR) signaling pathway in cell cycle re-entry and blocking autophagy are discussed as potential common intracellular components between AD and cancer pathogenesis, with diverse clinical diagnosis.

Prediction of Optimal Drug Schedules for Controlling Autophagy

The effects of molecularly targeted drug perturbations on cellular activities and fates are difficult to predict using intuition alone because of the complex behaviors of cellular regulatory networks. An approach to overcoming this problem is to develop mathematical models for predicting drug effects. Such an approach beckons for co-development of computational methods for extracting insights useful for guiding therapy selection and optimizing drug scheduling. Here, we present and evaluate a generalizable strategy for identifying drug dosing schedules that minimize the amount of drug needed to achieve sustained suppression or elevation of an important cellular activity/process, the recycling of cytoplasmic contents through (macro)autophagy. Therapeutic targeting of autophagy is currently being evaluated in diverse clinical trials but without the benefit of a control engineering perspective. Using a nonlinear ordinary differential equation (ODE) model that accounts for activating and inhibiting influences among protein and lipid kinases that regulate autophagy (MTORC1, ULK1, AMPK and VPS34) and methods guaranteed to find locally optimal control strategies, we find optimal drug dosing schedules (open-loop controllers) for each of six classes of drugs and drug pairs. Our approach is generalizable to designing monotherapy and multi therapy drug schedules that affect different cell signaling networks of interest.

CK2 inhibition with silmitasertib promotes methuosis-like cell death associated to catastrophic massive vacuolization of colorectal cancer cells

Protein kinase CK2 is a highly conserved and constitutively active Ser/Thr-kinase that phosphorylates a large number of substrates, resulting in increased cell proliferation and survival. A known target of CK2 is Akt, a player in the PI3K/Akt/mTORC1 signaling pathway, which is aberrantly activated in 32% of colorectal cancer (CRC) patients. On the other hand, mTORC1 plays an important role in the regulation of protein synthesis, cell growth, and autophagy. Some studies suggest that CK2 regulates mTORC1 in several cancers. The most recently developed CK2 inhibitor, silmitasertib (formerly CX-4945), has been tested in phase I/II trials for cholangiocarcinoma and multiple myeloma. This drug has been shown to induce autophagy and enhance apoptosis in pancreatic cancer cells and to promote apoptosis in non-small cell lung cancer cells. Nevertheless, it has not been tested in studies for CRC patients. We show in this work that inhibition of CK2 with silmitasertib decreases in vitro tumorigenesis of CRC cells in response to G2/M arrest, which correlates with mTORC1 inhibition and formation of large cytoplasmic vacuoles. Notably, molecular markers indicate that these vacuoles derive from massive macropinocytosis. Altogether, these findings suggest that an aberrantly elevated expression/activity of CK2 may play a key role in CRC, promoting cell viability and proliferation in untreated cells, however, its inhibition with silmitasertib promotes methuosis-like cell death associated to massive catastrophic vacuolization, accounting for decreased tumorigenicity at later times. These characteristics of silmitasertib support a potential therapeutic use in CRC patients and probably other CK2-dependent cancers.

Role of mTOR Signaling in Female Reproduction

Mammalian target of rapamycin (mTOR) is a conserved serine/threonine kinase of the phosphatidylinositol kinase-related kinase family that regulates cell growth, metabolism, and autophagy. Extensive research has linked mTOR to several human diseases including cancer, neurodegenerative disorders, and aging. In this review, recent publications regarding the mechanisms underlying the role of mTOR in female reproduction under physiological and pathological conditions are summarized. Moreover, we assess whether strategies to improve or suppress mTOR expression could have therapeutic potential for reproductive diseases like premature ovarian failure, polycystic ovarian syndrome, and endometriosis.

Pterostilbene inhibits nutrient metabolism and induces apoptosis through AMPK activation in multiple myeloma cells

Multiple myeloma (MM) cells are characterized by an abnormal nutrient metabolism that is distinct from normal plasma cells. Pterostilbene (PTE), a bioactive component of blueberries, has been demonstrated to induce apoptosis in multiple types of cancer cell. The present study evaluated whether PTE treatment affected the survival of MM cells from a metabolic perspective, and the potential mechanisms of this. It was observed that the administration of PTE induced apoptosis, which was mediated by the increased activation of AMP‑activated protein kinase (AMPK). Once activated, AMPK decreased the expression and/or activity of key lipogenic enzymes, including fatty acid synthase and acetyl‑CoA carboxylase. In addition, the activation of AMPK suppressed the downstream substrate, mechanistic target of rapamycin, which dephosphorylated eukaryotic initiation factor 4E‑binding protein 1, leading to a general decrease in mRNA translation. Pre‑treatment with the AMPK inhibitor compound C prior to PTE treatment compromised the anti‑myeloma apoptosis effect, suggesting the critical role of AMPK in mediating PTE‑induced cell toxicity. Consistent results were obtained in vivo. Finally, autophagy was adaptively upregulated subsequent to PTE treatment; the pro‑apoptotic efficacy of PTE was potentiated once autophagic flux was inhibited by 3‑methyladenine. Taken together, these data demonstrated that PTE exerts anti‑tumor effects on MM cells via AMPK‑induced nutrient suppression.

Mechanistic/mammalian target of rapamycin: Recent pathological aspects and inhibitors

The mechanistic/mammalian target of rapamycin (mTOR), also known as the mechanistic target of rapamycin, regulates many normal cell processes such as transcription, cell growth, and autophagy. Overstimulation of mTOR by its ligands, amino acids, sugars, and/or growth factors leads to physiological disorders, including cancer and neurodegenerative diseases. In this study, we reviewed the recent advances regarding the mechanism that involves mTOR in cancer, aging, and neurodegenerative diseases. The chemical and biological properties of recently reported small molecules that function as mTOR kinase inhibitors, including adenosine triphosphate-competitive inhibitors and dual mTOR/PI3K inhibitors, have also been reviewed. We focused on the reports published in the literature from 2012 to 2017.

Insights into Novel Prognostic and Possible Predictive Biomarkers of Lung Neuroendocrine Tumors

Primary lung neuroendocrine tumors (NETs) consist of typical and atypical carcinoids, large-cell neuroendocrine carcinomas and small-cell lung carcinomas. NETs are highly heterogeneous in histological characteristics, clinical presentation and natural history. While there are morphological and immunohistochemical criteria to establish diagnosis, there is a lack of universal consensus for prognostic factors or therapeutic targets for personalized treatment of the disease. Thus, identifying potential markers of neuroendocrine differentiation and prognostic factors remains of high importance. This review provides an insight into promising molecules and genes that are implicated in NET carcinogenesis, cell-cycle regulation, chromatin remodeling, apoptosis, intracellular cascades and cell-cell interactions. Additionally it supports a basis for classifying these tumors into categories that distinct molecular characteristics and disease natural history, which may have a direct impact on treatment options. In light of the recent approval of everolimus, mammalian target of rapamycin pathway inhibition and related biomarkers may play a central role in the treatment of pulmonary NETs. Future clinical trials that integrate molecular profiling are deemed necessary in order to treat patients with NET on a personalized basis.

Co-targeting PLK1 and mTOR induces synergistic inhibitory effects against esophageal squamous cell carcinoma

Both polo-like kinase 1 (PLK1) and mammalian/mechanistic target of rapamycin (mTOR) are attractive therapeutic targets for cancer therapy. However, the efficacy of the combined inhibition of both pathways for treating esophageal squamous cell carcinoma (ESCC), an aggressive malignancy with poor prognosis, remains unknown. In this study, we found that suppression of PLK1 by specific siRNA or inhibitor attenuated mTOR activity in ESCC cells. Phosphorylated S6, a downstream effector of mTOR signaling, was significantly correlated with overexpression of PLK1 in a subset of ESCC. These data suggest that PLK1 activates mTOR signaling in vitro and in vivo. More importantly, the mTOR inhibitor rapamycin synergized with PLK1 inhibitor BI 2536 to inhibit ESCC cell proliferation in culture and in mice. Notably, combined treatment with BI 2536 and rapamycin produced more potent inhibitory effects on the activation of S6 and AKT than either alone. Further analysis reveals that PLK1 modulates both mTOR complex 1 (mTORC1) and mTOR complex 2 (mTORC2) cascades. Therefore, dual inhibition of PLK1 and mTOR yields stronger antitumor effects, at least partially due to synergistic abrogated the activation of S6, eukaryotic initiation factor 4E-binding protein 1 (4E-BP1), and AKT by cooperatively blocking mTORC1 and mTORC2 cascades. These results provide evidence that the mTOR inhibitor rapamycin synergistically enhances the antitumor effect of PLK1 inhibitor BI 2536 in ESCC cells. Simultaneous targeting of PLK1 and mTOR may thus be a novel and promising therapeutic strategy for ESCC.

KEY MESSAGES

PLK1 potentiates both mTORC1 and mTORC2 activities in ESCC cells. PLK1 expression positively correlated with mTOR activity in a subset of ESCC. Co-targeting of PLK1 and mTOR produced stronger antitumor effects partially due to synergistic inhibition of AKT, 4E-BP1 and S6 through cooperatively blocking mTORC2 and mTORC1 cascades. Combination targeting of PLK1 and mTOR may be a novel and promising therapeutic strategy for ESCC treatment.

Noncanonical Pathway for Regulation of CCL2 Expression by an mTORC1-FOXK1 Axis Promotes Recruitment of Tumor-Associated Macrophages

C-C chemokine ligand 2 (CCL2) plays pivotal roles in tumor formation, progression, and metastasis. Although CCL2 expression has been found to be dependent on the nuclear factor (NF)-κB signaling pathway, the regulation of CCL2 production in tumor cells has remained unclear. We have identified a noncanonical pathway for regulation of CCL2 production that is mediated by mammalian target of rapamycin complex 1 (mTORC1) but independent of NF-κB. Multiple phosphoproteomics approaches identified the transcription factor forkhead box K1 (FOXK1) as a downstream target of mTORC1. Activation of mTORC1 induces dephosphorylation of FOXK1, resulting in transactivation of the CCL2 gene. Inhibition of the mTORC1-FOXK1 axis attenuated insulin-induced CCL2 production as well as the accumulation of tumor-associated monocytes-macrophages and tumor progression in mice. Our results suggest that FOXK1 directly links mTORC1 signaling and CCL2 expression in a manner independent of NF-κB and that CCL2 produced by this pathway contributes to tumor progression.

Alterations of mTOR signaling impact metabolic stress resistance in colorectal carcinomas with BRAF and KRAS mutations

Metabolic reprogramming is as a hallmark of cancer, and several studies have reported that BRAF and KRAS tumors may be accompanied by a deregulation of cellular metabolism. We investigated how BRAF^V600E and KRAS^G12V affect cell metabolism, stress resistance and signaling in colorectal carcinoma cells driven by these mutations. KRAS^G12V expressing cells are characterized by the induction of glycolysis, accumulation of lactic acid and sensitivity to glycolytic inhibition. Notably mathematical modelling confirmed the critical role of MCT1 designating the survival of KRAS^G12V cells. Carcinoma cells harboring BRAF^V600E remain resistant towards alterations of glucose supply or application of signaling or metabolic inhibitors. Altogether these data demonstrate that an oncogene-specific decoupling of mTOR from AMPK or AKT signaling accounts for alterations of resistance mechanisms and metabolic phenotypes. Indeed the inhibition of mTOR in BRAF^V600E cells counteracts the metabolic predisposition and demonstrates mTOR as a potential target in BRAF^V600E-driven colorectal carcinomas.

Beneficial Effects of Resveratrol-Mediated Inhibition of the mTOR Pathway in Spinal Cord Injury

Spinal cord injury (SCI) causes a high rate of morbidity and disability. The clinical features of SCI are divided into acute, subacute, and chronic phases according to its pathophysiological events. The mammalian target of rapamycin (mTOR) signaling pathway plays an important role in cell death and inflammation in the acute phase and neuroregeneration in the subacute/chronic phases at different times. Resveratrol has the potential of regulating cell growth, proliferation, metabolism, and angiogenesis through the mTOR signaling pathway. Herein, we explicate the role of resveratrol in the repair of SCI through the inhibition of the mTOR signaling pathway. The inhibition of the mTOR pathway by resveratrol has the potential of serving as a neuronal restorative mechanism following SCI.