Overexpression of s6 kinase 1 in brain tumours is associated with induction of hypoxia-responsive genes and predicts patients' survival

Recent progress on FAK inhibitors with dual targeting capabilities for cancer treatment

Focal adhesion kinase (FAK, also known as PTK2) is a tyrosine kinase that regulates integrin and growth factor signaling pathways and is involved in the migration, proliferation and survival of cancer cells. FAK is a promising target for cancer treatment. Many small molecule FAK inhibitors have been identified and proven in both preclinical and clinical studies to be effective inhibitors of tumor growth and metastasis. There are many signaling pathways, such as those involving FAK, Src, AKT, MAPK, PI3K, and EGFR/HER-2, that provide survival signals in cancer cells. Dual inhibitors that simultaneously block FAK and another factor can significantly improve efficacy and overcome some of the shortcomings of single-target inhibitors, including drug resistance. In this review, the antitumor mechanisms and research status of dual inhibitors of FAK and other targets, such as Pyk2, IGF-IR, ALK, VEGFR-3, JAK2, EGFR, S6K1, and HDAC2, are summarized, providing new ideas for the development of effective FAK dual-target preparations.

p70 S6 kinase as a therapeutic target in cancers: More than just an mTOR effector

p70 S6 kinase (p70^S6K) is best-known for its regulatory roles in protein synthesis and cell growth by phosphorylating its primary substrate, ribosomal protein S6, upon mitogen stimulation. The enhanced expression/activation of p70^S6K has been correlated with poor prognosis in some cancer types, suggesting that it may serve as a biomarker for disease monitoring. p70^S6K is a critical downstream effector of the oncogenic PI3K/Akt/mTOR pathway and its activation is tightly regulated by an ordered cascade of Ser/Thr phosphorylation events. Nonetheless, it should be noted that other upstream mechanisms regulating p70^S6K at both the post-translational and post-transcriptional levels also exist. Activated p70^S6K could promote various aspects of cancer progression such as epithelial-mesenchymal transition, cancer stemness and drug resistance. Importantly, novel evidence showing that p70^S6K may also regulate different cellular components in the tumor microenvironment will be discussed. Therapeutic targeting of p70^S6K alone or in combination with traditional chemotherapies or other microenvironmental-based drugs such as immunotherapy may represent promising approaches against cancers with aberrant p70^S6K signaling. Currently, the only clinically available p70^S6K inhibitors are rapamycin analogs (rapalogs) which target mTOR. However, there are emerging p70^S6K-selective drugs which are going through active preclinical or clinical trial phases. Moreover, various screening strategies have been used for the discovery of novel p70^S6K inhibitors, hence bringing new insights for p70^S6K-targeted therapy.

A Preclinical Investigation of GBM-N019 as a Potential Inhibitor of Glioblastoma via Exosomal mTOR/CDK6/STAT3 Signaling

Glioblastoma (GBM) is one of the most aggressive brain malignancies with high incidences of developing treatment resistance, resulting in poor prognoses. Glioma stem cell (GSC)-derived exosomes are important players that contribute to GBM tumorigenesis and aggressive properties. Herein, we investigated the inhibitory roles of GBM-N019, a novel small molecule on the transfer of aggressive and invasive properties through the delivery of oncogene-loaded exosomes from GSCs to naïve and non-GSCs. Our results indicated that GBM-N019 significantly downregulated the expressions of the mammalian target of rapamycin (mTOR), signal transducer and activator of transcription 3 (STAT3), and cyclin-dependent kinase 6 (CDK6) signaling networks with concomitant inhibitory activities against viability, clonogenicity, and migratory abilities of U251 and U87MG cells. Treatments with GBM-N019 halted the exosomal transfer of protein kinase B (Akt), mTOR, p-mTOR, and Ras-related protein RAB27A to the naïve U251 and U87MG cells, and rescued the cells from invasive and stemness properties that were associated with activation of these oncogenes. GBM-N019 also synergized with and enhanced the anti-GBM activities of palbociclib in vitro and in vivo. In conclusion, our results suggested that GBM-N019 possesses good translational relevance as a potential anti-glioblastoma drug candidate worthy of consideration for clinical trials against recurrent glioblastomas.

Inhibition of p70 isoforms of S6K1 induces anoikis to prevent transformed human hepatocyte growth

AIMS

The mTOR/S6K1 signaling axis, known for cell growth regulation, is hyper-activated in multiple cancers. In this study, we have examined the mechanisms for ribosomal protein p70-S6 kinase 1 (S6K1) associated transformed human hepatocyte (THH) growth regulation.

MAIN METHODS

THH were treated with p70-S6K1 inhibitor and analyzed for cell viability, cell cycle distribution, specific marker protein expression by western blot, and tumor inhibition in a xenograft mouse model. We validated our results by knockdown of p70-S6K1 using specific siRNA.

KEY FINDINGS

p70-S6K1 inhibitor treatment caused impairment of in vitro hepatocyte growth, and arrested cell cycle progression at the G1 phase. Further, p70-S6K1 inhibitor treatment exhibited a decrease in FAK and Erk activation, followed by altered integrin-β1 expression, caspase 8, and PARP cleavage appeared to be anoikis like growth inhibition. p70-S6K1 inhibitor also depolymerized actin microfilaments and diminished active Rac1/Cdc42 complex formation for loss of cellular attachment. Similar results were obtained with other transformed human hepatocyte cell lines. p70-S6K1 inhibition also resulted in a reduced phospho-EGFR, Slug and Twist; implicating an inhibition of epithelial-mesenchymal transition (EMT) state. A xenograft tumor model, generated from implanted THH in nude mice, following intraperitoneal injection of S6K1 inhibitor prevented further tumor growth.

SIGNIFICANCE

Our results suggested that p70-S6K1 inhibition alters orchestration of cell cycle progression, induces cell detachment, and sensitizes hepatocyte growth impairment. Targeting p70 isoform of S6K1 by inhibitor may prove to be a promising approach together with other therapies for hepatocellular carcinoma (HCC) treatment.

Hydrogen sulphide ameliorates dopamine-induced astrocytic inflammation and neurodegeneration in minimal hepatic encephalopathy

It has been demonstrated that the action of dopamine (DA) could enhance the production of tumour necrosis factor‐α (TNF‐α) by astrocytes and potentiate neuronal apoptosis in minimal hepatic encephalopathy (MHE). Recently, sodium hydrosulfide (NaHS) has been found to have neuroprotective properties. Our study addressed whether NaHS could rescue DA‐challenged inflammation and apoptosis in neurons to ameliorate memory impairment in MHE rats and in the neuron and astrocyte coculture system. We found that NaHS suppressed DA‐induced p65 acetylation, resulting in reduced TNF‐α production in astrocytes both in vitro and in vivo. Furthermore, decreased apoptosis was observed in neurons exposed to conditioned medium from DA + NaHS‐challenged astrocytes, which was similar to the results obtained in the neurons exposed to TNF‐α + NaHS, suggesting a therapeutic effect of NaHS on the suppression of neuronal apoptosis via the reduction of TNF‐α level. DA triggered the inactivation of p70 S6 ribosomal kinase (S6K1) and dephosphorylation of Bad, resulting in the disaggregation of Bclxl and Bak and the release of cytochrome c (Cyt. c), and this process could be reversed by NaHS administration. Our work demonstrated that NaHS attenuated DA‐induced astrocytic TNF‐α release and ameliorated inflammation‐induced neuronal apoptosis in MHE. Further research into this approach may uncover future potential therapeutic strategies for MHE.

FAK and S6K1 Inhibitor, Neferine, Dually Induces Autophagy and Apoptosis in Human Neuroblastoma Cells

Human neuroblastoma cancer is the most typical extracranial solid tumor. Yet, new remedial treatment therapies are demanded to overcome its sluggish survival rate. Neferine, isolated from the lotus embryos, inhibits the proliferation of various cancer cells. This study aimed to evaluate the anti-cancer activity of neferine in IMR32 human neuroblastoma cells and to expose the concealable molecular mechanisms. IMR32 cells were treated with different concentrations of neferine, followed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay to assess cell viability. In an effort to determine the molecular mechanisms in neferine-incubated IMR32 cells, cell cycle arrest, cell migration, and focal adhesion kinase (FAK), the 70-kDa ribosomal S6 kinase 1 (S6K1), poly (ADP-ribose) polymerase (PARP), caspase-3, Beclin-1, and microtubule-associated protein 1A/1B-light chain 3 (LC3) protein expressions were investigated. Neferine strongly disrupted the neuroblastoma cell growth via induction of G2/M phase arrest. Furthermore, neferine provoked autophagy and apoptosis in IMR32 cells, confirmed by p-FAK, and p-S6K1 reduction, LC3-II accumulation, Beclin-1 overexpression, and cleaved caspase-3/PARP improvement. Finally, neferine markedly retarded cell migration of neuroblastoma cancer cells. As a result, our findings for the first time showed an explicit anti-cancer effect of neferine in IMR32 cells, suggesting that neferine might be a potential candidate against human neuroblastoma cells to improve clinical outcomes with further in vivo investigation.

Tinnitus Is Associated with a Higher Risk of Benign Brain Tumors: A Nationwide, Population-Based Secondary Cohort Study of Young and Middle-Aged Adults

BACKGROUND

It remains unclear whether tinnitus is associated with a higher risk of benign or malignant brain tumors in humans. Therefore, the aim of this secondary study was to investigate the risk of brain tumors in adult with tinnitus using data from a nationwide health claims research database.

METHODS

Patients aged 20-50 years who were newly diagnosed with tinnitus were identified from the Taiwan's National Health Insurance Research Database and they served as the study cohort. A comparison cohort was formed by using patients without tinnitus from the same database with frequency matching (4: 1) by 10-year age interval and gender to the patients in the tinnitus cohort. Cox proportional hazards models were used to calculate the adjusted hazard ratios (AHR) for benign and malignant brain tumors in patients with tinnitus, adjusting for age, gender, and comorbidities.

RESULTS

There were 15,819 patients in the tinnitus cohort and 63,276 in the comparison cohort. A significantly higher proportion of patients with tinnitus had benign brain tumor (p = 0.003) and all 11 comorbid conditions (p < 0.001) compared to those without tinnitus. Cox proportional hazards regression analysis performed on the basis of age, gender, and the 11 comorbidities revealed that tinnitus was independently associated with a higher risk for benign brain tumor (AHR 1.65, 95% CI 1.24-2.20, p = 0.001) and but not with malignant brain tumors (AHR 1.66, 95% CI 0.93-2.94, p = 0.085).

CONCLUSIONS

Findings from this secondary cohort analysis indicated that tinnitus is associated with a higher risk of benign brain tumors.

p53 modulates the effect of ribosomal protein S6 kinase1 (S6K1) on cisplatin toxicity in chronic myeloid leukemia cells

Chronic myeloid leukemia (CML) is characterized by the expression of the oncoprotein, BCR-ABL. BCR-ABL inhibitors revolutionized CML chemotherapy while blast crisis (BC) CML patients are less responsive. Since suppression of ribosomal protein S6 kinase1 (S6K1) phosphorylation reverses the resistance to BCR-ABL inhibitor in CML cells and S6K1 inhibitors augment cisplatin toxicity in lung cancer cells, we speculated that combination of S6K1 inhibitor and cisplatin may be beneficial for eliminating BC CML cells. To our surprise, S6K1 inhibition decreased cisplatin-induced DNA damage and cell death only in p53^-/- BC CML cells but not in p53^+/+ BC CML cells. During the progression of CML, p53 expression either decreases or mutates. Moreover, the expression of p53 affects drug response of CML cells. Our results confirmed that S6K1 inhibition reversed cisplatin toxicity is dependent on p53 expression in CML cells. Moreover, p53 attenuated the phosphorylation and localization of S6K1 via attenuating 3-phosphoinositide dependent protein kinase-1 (PDK1) phosphorylation. Furthermore, S6K1 acts via DNA-PKcs to regulate H2AX phosphorylation and PARP cleavage, respectively. Taken together, our results suggest that p53/PDK1/S6K1 is a novel pathway regulating cisplatin toxicity in BC CML cells.

Modeling of Cancer Classifier to Predict Site of Origin

Cancer classification based on site of origin is very significant research issue for prediction and treatment of cancer. This paper is addressing the problem of cancer classification for Homo Sapiens genes composed of amino acid chain. Cancer gene network is realized by equivalent electrical circuits based on hydrophilic/ hydrophobic property of amino acid and a classifier is modeled to determine the cancer origin. The phase value, peak gain value and shape of Nyquist curve of network model are investigated to characterize different types of cancer gene origins. The model achieves 81.09% of classification accuracy and proves to be more sensitive and simple, since it shows 69% better performance compare to the existing nucleotide based method. The proposed classifier successfully predicts the site of origin of 93 cancer gene samples.

mTOR in Brain Physiology and Pathologies

TOR (target of rapamycin) and its mammalian ortholog mTOR have been discovered in an effort to understand the mechanisms of action of the immunosuppressant drug rapamycin extracted from a bacterium of the Easter Island (Rapa Nui) soil. mTOR is a serine/threonine kinase found in two functionally distinct complexes, mTORC1 and mTORC2, which are differentially regulated by a great number of nutrients such as glucose and amino acids, energy (oxygen and ATP/AMP content), growth factors, hormones, and neurotransmitters. mTOR controls many basic cellular functions such as protein synthesis, energy metabolism, cell size, lipid metabolism, autophagy, mitochondria, and lysosome biogenesis. In addition, mTOR-controlled signaling pathways regulate many integrated physiological functions of the nervous system including neuronal development, synaptic plasticity, memory storage, and cognition. Thus it is not surprising that deregulation of mTOR signaling is associated with many neurological and psychiatric disorders. Preclinical and preliminary clinical studies indicate that inhibition of mTORC1 can be beneficial for some pathological conditions such as epilepsy, cognitive impairment, and brain tumors, whereas stimulation of mTORC1 (direct or indirect) can be beneficial for other pathologies such as depression or axonal growth and regeneration.

Preclinical and clinical studies of the NEDD9 scaffold protein in cancer and other diseases

Cancer progression requires a significant reprogramming of cellular signaling to support the essential tumor-specific processes that include hyperproliferation, invasion (for solid tumors) and survival of metastatic colonies. NEDD9 (also known as CasL and HEF1) encodes a multi-domain scaffolding protein that assembles signaling complexes regulating multiple cellular processes relevant to cancer. These include responsiveness to signals emanating from the T and B cell receptors, integrins, chemokine receptors, and receptor tyrosine kinases, as well as cytoplasmic oncogenes such as BCR-ABL and FAK- and SRC-family kinases. Downstream, NEDD9 regulation of partners including CRKL, WAVE, PI3K/AKT, ERK, E-cadherin, Aurora-A (AURKA), HDAC6, and others allow NEDD9 to influence functions as pleiotropic as migration, invasion, survival, ciliary resorption, and mitosis. In this review, we summarize a growing body of preclinical and clinical data that indicate that while NEDD9 is itself non-oncogenic, changes in expression of NEDD9 (most commonly elevation of expression) are common features of tumors, and directly impact tumor aggressiveness, metastasis, and response to at least some targeted agents inhibiting NEDD9-interacting proteins. These data strongly support the relevance of further development of NEDD9 as a biomarker for therapeutic resistance. Finally, we briefly discuss emerging evidence supporting involvement of NEDD9 in additional pathological conditions, including stroke and polycystic kidney disease.

mTOR Signaling in Protein Translation Regulation: Implications in Cancer Genesis and Therapeutic Interventions

mTOR is a central nutrient sensor that signals a cell to grow and proliferate. Through distinct protein complexes it regulates different levels of available cellular energy substrates required for cell growth. One of the important functions of the complex is to maintain available amino acid pool by regulating protein translation. Dysregulation of mTOR pathway leads to aberrant protein translation which manifests into various pathological states. Our review focuses on the role mTOR signaling plays in protein translation and its physiological role. It also throws some light on available data that show translation dysregulation as a cause of pathological complexities like cancer and the available drugs that target the pathway for cancer treatment.

p70 Ribosomal protein S6 kinase (Rps6kb1): an update

The Rps6kb1 gene encodes the 70 kDa ribosomal protein S6 kinase (p70S6K), which is a serine/threonine kinase regulated by phosphoinositide 3-kinase (PI3K)/mammalian target of rapamycin (mTOR) pathway. p70S6K plays a crucial role in controlling cell cycle, growth and survival. The PI3K/mTOR signalling pathway is one of the major mechanisms for controlling cell survival, proliferation and metabolism and is the central regulator of translation of some components of protein synthesis system. Upon activation, this kinase phosphorylates S6 protein of ribosomal subunit 40S resulting in selective translation of unique family of mRNAs that contain oligopyrimidine tract on 5' transcriptional site (5'TOP). 5'TOP mRNAs are coding the components of translational apparatus including ribosomal proteins and elongation factors. Due to the role of p70S6K in protein synthesis and also its involvement in a variety of human diseases ranging from diabetes and obesity to cancer, p70S6K is now being considered as a new therapeutic target for drug development. Furthermore, p70S6K acts as a biomarker for response to immunosuppressant as well as anticancer effects of inhibitors of the mTOR. Because of the narrow therapeutic index of mTOR inhibitors, drug monitoring is essential, and this is usually done by measuring blood drug levels, therapeutic response and drug-induced adverse effects. Recent studies have suggested that plasma p70S6K is a reliable index for the monitoring of patient response to mTOR inhibitors. Therefore, a better understanding of p70S6K and its role in various pathological conditions could enable the development of strategies to aid diagnosis, prognosis and treatment schedules.

Adaptors for disorders of the brain? The cancer signaling proteins NEDD9, CASS4, and PTK2B in Alzheimer's disease

No treatment strategies effectively limit the progression of Alzheimer's disease (AD), a common and debilitating neurodegenerative disorder. The absence of viable treatment options reflects the fact that the pathophysiology and genotypic causes of the disease are not well understood. The advent of genome-wide association studies (GWAS) has made it possible to broadly investigate genotypic alterations driving phenotypic occurrences. Recent studies have associated single nucleotide polymorphisms (SNPs) in two paralogous scaffolding proteins, NEDD9 and CASS4, and the kinase PTK2B, with susceptibility to late-onset AD (LOAD). Intriguingly, NEDD9, CASS4, and PTK2B have been much studied as interacting partners regulating oncogenesis and metastasis, and all three are known to be active in the brain during development and in cancer. However, to date, the majority of studies of these proteins have emphasized their roles in the directly cancer relevant processes of migration and survival signaling. We here discuss evidence for roles of NEDD9, CASS4 and PTK2B in additional processes, including hypoxia, vascular changes, inflammation, microtubule stabilization and calcium signaling, as potentially relevant to the pathogenesis of LOAD. Reciprocally, these functions can better inform our understanding of the action of NEDD9, CASS4 and PTK2B in cancer.

Rapamycin-enhanced mitomycin C-induced apoptotic death is mediated through the S6K1-Bad-Bak pathway in peritoneal carcinomatosis

Peritoneal carcinomatosis (PC) is the most common secondary cancerous disease, and more effective novel regimens are needed. In this study, we identified a novel combination treatment for PC, chemotherapeutic agent mitomycin C in combination with mTOR (mammalian target of rapamycin) inhibitor rapamycin. We observed that the combination of mitomycin C and rapamycin induced synergistic cytotoxicity and apoptosis, which was mediated through an increase in caspase activation. The combination of mitomycin C and rapamycin inactivated p70 S6 ribosomal kinase (S6K1) and dephosphorylated Bad, leading to dissociation of Bcl-xL from Bak, which resulted in Bak oligomerization, mitochondria dysfunction and cytochrome c release. PF-4708671, a S6K1-specific inhibitor, enhanced the combination treatment-induced apoptosis, whereas S6K1 E389 DeltaCT-HA (S6K1 active form) dramatically decreased the induction of apoptosis. In addition, the combination treatment significantly inhibited LS174T intraperitoneal tumor growth in vivo. This study provides a preclinical rationale for apoptosis induction linked with the mTOR pathway through a combination of chemotherapeutic agents and mTOR inhibitor, and will support this combinatorial strategy to PC patients.

Combination of pharmacophore hypothesis, genetic function approximation model, and molecular docking to identify novel inhibitors of S6K1

S6K1 has emerged as a potential target for the treatment for obesity, type II diabetes and cancer diseases. Discovery of S6K1 inhibitors has thus attracted much attention in recent years. In this investigation, a hybrid virtual screening method that involves pharmacophore hypothesis, genetic function approximation (GFA) model, and molecular docking technology has been used to discover S6K1 inhibitors especially with novel scaffolds. The common feature pharmacophore hypothesis and GFA regression model of S6K1 inhibitors were first developed and applied in a virtual screen of the Specs database for retrieving S6K1 inhibitors. Then, the molecular docking method was carried out to re-filter these screened compounds. Finally, 60 compounds with promising S6K1 inhibitory activity were carefully selected and have been handed over to the other group to complete the follow-up compound synthesis (or purchase) and activity test.