mTOR inhibition reprograms cellular proteostasis by regulating eIF3D-mediated selective mRNA translation and promotes cell phenotype switching.

Cells maintain and dynamically change their proteomes according to the environment and their needs. Mechanistic target of rapamycin (mTOR) is a key regulator of proteostasis, homeostasis of the proteome. Thus, dysregulation of mTOR leads to changes in proteostasis and the consequent progression of diseases, including cancer. Based on the physiological and clinical importance of mTOR signaling, we investigated mTOR feedback signaling, proteostasis, and cell fate. Here, we reveal that mTOR targeting inhibits eIF4E-mediated cap-dependent translation, but feedback signaling activates a translation initiation factor, eukaryotic translation initiation factor 3D (eIF3D), to sustain alternative non-canonical translation mechanisms. Importantly, eIF3D-mediated protein synthesis enables cell phenotype switching from proliferative to more migratory. eIF3D cooperates with mRNA-binding proteins such as heterogeneous nuclear ribonucleoprotein F (hnRNPF), heterogeneous nuclear ribonucleoprotein K (hnRNPK), and Sjogren syndrome antigen B (SSB) to support selective mRNA translation following mTOR inhibition, which upregulates and activates proteins involved in insulin receptor (INSR)/insulin-like growth factor 1 receptor (IGF1R)/insulin receptor substrate (IRS) and interleukin 6 signal transducer (IL-6ST)/Janus kinase (JAK)/signal transducer and activator of transcription (STAT) signaling. Our study highlights the mechanisms by which cells establish the dynamic change of proteostasis and the resulting phenotype switch.

Improved recurrence-free survival in patients with HCC with post-transplant plasma exchange.

Total plasma exchange (TPE) can play a role in cancer treatment by eliminating immune checkpoint inhibitors. This study investigated whether TPE improved oncological outcomes in patients with HCC who underwent ABO-incompatible living donor liver transplantation (LT). The study included 152 patients who underwent ABO-incompatible living donor LT for HCC between 2010 and 2021 at Samsung Medical Center. Overall survival was analyzed using the Kaplan-Meier curve, whereas HCC-specific recurrence-free survival (RFS) was analyzed using the cumulative incidence curve after propensity score matching. Cox regression and competing risks subdistribution hazard models were used to identify the risk factors associated with overall survival and HCC-specific RFS, respectively. The propensity score matching resulted in 54 matched pairs, grouped according to whether they underwent postoperative TPE [post-transplant TPE(+)] or not [post-transplant TPE(-)]. The 5-year HCC-specific RFS cumulative incidence was superior in the post-transplant TPE (+) group [12.5% (95% CI: 3.1%-21.9%)] compared with the post-transplant TPE(-) group [38.1% (95% CI: 24.4%-51.8%), p = 0.005]. In subgroup analysis for patients with microvascular invasion and those beyond the Milan criteria, the post-transplant TPE(+) group showed significantly superior HCC-specific survival. The multivariable analysis also showed that postoperative TPE had a protective effect on HCC-specific RFS (HR = 0.26, 95% CI: 0.10-0.64, p = 0.004) and that the more post-transplant TPE was performed, the better RFS was observed (HR = 0.71, 95% CI: 0.55-0.93, p = 0.012). Post-transplant TPE was found to improve RFS after ABO-incompatible living donor LT for HCC, particularly in advanced cases with microvascular invasion and beyond Milan criteria. These findings suggest that TPE may have a potential role in improving oncological outcomes in patients with HCC undergoing LT.

Validity and Reliability of the Korean-Translated Version of the International Cooperative Ataxia Rating Scale in Cerebellar Ataxia

Objective@#The International Cooperative Ataxia Rating Scale (ICARS) is a semiquantitative clinical scale for ataxia that is widely used in numerous countries. The purpose of this study was to investigate the validity and reliability of the Korean-translated version of the ICARS. @*Methods@#Eighty-eight patients who presented with cerebellar ataxia were enrolled. We investigated the construct validity using exploratory factor analysis (EFA) and confirmatory factor analysis (CFA). We also investigated the internal consistency using Cronbach’s α and intrarater and interrater reliability using intraclass correlation coefficients. @*Results@#The Korean-translated ICARS showed satisfactory construct validity using EFA and CFA. It also revealed good interrater and intrarater reliability and showed acceptable internal consistency. However, subscale 4 for assessing oculomotor disorder showed moderate internal consistency. @*Conclusion@#This is the first report to investigate the validity and reliability of the Korean-translated ICARS. Our results showed excellent construct and convergent validity. The reliability is also acceptable.

The PIKK-AKT connection in the DNA damage response.

DNA damage and subsequent cellular response are the basis for many cancer treatments. In this issue of Science Signaling, Liu et al. elucidate a mechanism by which cancer cells survive DNA damage induced by radiation and chemotherapy.

Dynamic Incorporation of Histone H3 Variants into Chromatin Is Essential for Acquisition of Aggressive Traits and Metastatic Colonization.

Metastasis is the leading cause of cancer mortality. Chromatin remodeling provides the foundation for the cellular reprogramming necessary to drive metastasis. However, little is known about the nature of this remodeling and its regulation. Here, we show that metastasis-inducing pathways regulate histone chaperones to reduce canonical histone incorporation into chromatin, triggering deposition of H3.3 variant at the promoters of poor-prognosis genes and metastasis-inducing transcription factors. This specific incorporation of H3.3 into chromatin is both necessary and sufficient for the induction of aggressive traits that allow for metastasis formation. Together, our data clearly show incorporation of histone variant H3.3 into chromatin as a major regulator of cell fate during tumorigenesis, and histone chaperones as valuable therapeutic targets for invasive carcinomas.

The primitive growth factor NME7AB induces mitochondrially active naïve-like pluripotent stem cells.

Naïve pluripotent stem cells (PSCs) display a distinctive phenotype when compared to their "primed" counterparts, including, but not limited to, increased potency to differentiate and more robust mitochondrial respiration. The cultivation and maintenance of naïve PSCs have been notoriously challenging, requiring the use of complex cytokine cocktails. NME7AB is a newly discovered embryonic stem cell growth factor that is expressed exclusively in the first few days of human blastocyst development. It has been previously reported that growing primed induced PSCs (iPSCs) in bFGF-depleted medium with NME7AB as the only added growth factor facilitates the regression of these cells to their naïve state. Here, we confirm this regression by demonstrating the reactivation of mitochondrial function in the induced naïve-like PSCs and increased ATP production in these cells, as compared to that in primed iPSCs.

Metabolic switching in pluripotent stem cells reorganizes energy metabolism and subcellular organelles.

Metabolic studies of human pluripotent stem cells (hPSCs) have focused on how the cells produce energy through the catabolic pathway. The less-studied anabolic pathway, by which hPSCs expend energy in the form of adenosine triphosphate (ATP), is not yet fully understood. Compared to fully differentiated somatic cells, hPSCs undergo significant changes not only in their gene expression but also in their production and/or expenditure of ATP. Here, we investigate how hPSCs tightly control their energy homeostasis by studying the main energy-consuming process, mRNA translation. In addition, change of subcellular organelles regarding energy homeostasis has been investigated. Lysosomes are organelles that play an important role in the elimination of unnecessary cellular materials by digestion and in the recycling system of the cell. We have found that hPSCs control their lysosome numbers in part by regulating lysosomal gene/protein expression. Thus, because the levels of mRNA translation rate are lower in hPSCs than in somatic cells, not only the global translational machinery but also the lysosomal recycling machinery is suppressed in hPSCs. Overall, the results of our study suggest that hPSCs reprogram gene expression and signaling to regulate energy-consuming processes and energy-controlling organelles.

ERK2 regulates epithelial-to-mesenchymal plasticity through DOCK10-dependent Rac1/FoxO1 activation.

ERK is a key coordinator of the epithelial-to-mesenchymal transition (EMT) in that a variety of EMT-inducing factors activate signaling pathways that converge on ERK to regulate EMT transcription programs. However, the mechanisms by which ERK controls the EMT program are not well understood. Through an analysis of the global changes of gene expression mediated by ERK2, we identified the transcription factor FoxO1 as a potential mediator of ERK2-induced EMT, and thus we investigated the mechanism by which ERK2 regulates FoxO1. Additionally, our analysis revealed that ERK2 induced the expression of Dock10, a Rac1/Cdc42 GEF, during EMT. We demonstrate that the activation of the Rac1/JNK signaling axis downstream of Dock10 leads to an increase in FoxO1 expression and EMT. Taken together, our study uncovers mechanisms by which epithelial cells acquire less proliferative but more migratory mesenchymal properties and reveals potential therapeutic targets for cancers evolving into a metastatic disease state.

The Impact of Impulsivity on Quality of Life in Early Drug-Naïve Parkinson's Disease Patients

OBJECTIVE: Impulse control disorders (ICDs) in Parkinson's disease (PD) are mostly related to dopamine replacement therapy (DRT); however, drug-naïve PD patients have also frequently experienced impulsivity. This phenomenon makes clinicians hesitate treating patients with DRT. In this study, we assessed the effect of impulsivity on quality of life (QOL) in drug-naïve PD patients. METHODS: Two hundred three newly diagnosed, nonmedicated PD patients were enrolled, and they received structured clinical interviews, physical examinations and validated questionnaires to evaluate motor and nonmotor symptoms and QOL. Impulsivity was evaluated using the Questionnaire for Impulsive-Compulsive Disorders in Parkinson's Disease-Rating Scale (QUIP-RS). RESULTS: Thirty-eight patients (18.7%) had impulsivity with QUIP-RS scores ≥ 1 and 4 patients (2.0%) were diagnosed with combined ICDs. Motor and nonmotor symptoms were significantly correlated with the Parkinson's Disease Questionnaire-39 summary index. Female sex and QUIP-RS scores were also correlated with QOL in drug-naïve PD patients. CONCLUSION: The results of the present study showed that impulsivity negatively influences QOL in early drug-naïve PD patients. In addition, more severe motor and nonmotor symptoms were also associated with lower QOL. Such findings complicate treatment but provide valuable information for managing early PD.

mTORC1 Promotes Metabolic Reprogramming by the Suppression of GSK3-Dependent Foxk1 Phosphorylation.

The mammalian Target of Rapamycin Complex 1 (mTORC1)-signaling system plays a critical role in the maintenance of cellular homeostasis by sensing and integrating multiple extracellular and intracellular cues. Therefore, uncovering the effectors of mTORC1 signaling is pivotal to understanding its pathophysiological effects. Here we report that the transcription factor forkhead/winged helix family k1 (Foxk1) is a mediator of mTORC1-regulated gene expression. Surprisingly, Foxk1 phosphorylation is increased upon mTORC1 suppression, which elicits a 14-3-3 interaction, a reduction of DNA binding, and nuclear exclusion. Mechanistically, this occurs by mTORC1-dependent suppression of nuclear signaling by the Foxk1 kinase, Gsk3. This pathway then regulates the expression of multiple genes associated with glycolysis and downstream anabolic pathways directly modulated by Foxk1 and/or by Foxk1-regulated expression of Hif-1α. Thus, Foxk1 mediates mTORC1-driven metabolic rewiring, and it is likely to be critical for metabolic diseases where improper mTORC1 signaling plays an important role.

RSK Regulates PFK-2 Activity to Promote Metabolic Rewiring in Melanoma.

Metabolic reprogramming is a hallmark of cancer that includes increased glucose uptake and accelerated aerobic glycolysis. This phenotype is required to fulfill anabolic demands associated with aberrant cell proliferation and is often mediated by oncogenic drivers such as activated BRAF. In this study, we show that the MAPK-activated p90 ribosomal S6 kinase (RSK) is necessary to maintain glycolytic metabolism in BRAF-mutated melanoma cells. RSK directly phosphorylated the regulatory domain of 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase 2 (PFKFB2), an enzyme that catalyzes the synthesis of fructose-2,6-bisphosphate during glycolysis. Inhibition of RSK reduced PFKFB2 activity and glycolytic flux in melanoma cells, suggesting an important role for RSK in BRAF-mediated metabolic rewiring. Consistent with this, expression of a phosphorylation-deficient mutant of PFKFB2 decreased aerobic glycolysis and reduced the growth of melanoma in mice. Together, these results indicate that RSK-mediated phosphorylation of PFKFB2 plays a key role in the metabolism and growth of BRAF-mutated melanomas.Significance: RSK promotes glycolytic metabolism and the growth of BRAF-mutated melanoma by driving phosphorylation of an important glycolytic enzyme. Cancer Res; 78(9); 2191-204. ©2018 AACR.

Focal Adhesion- and IGF1R-Dependent Survival and Migratory Pathways Mediate Tumor Resistance to mTORC1/2 Inhibition.

Aberrant signaling by the mammalian target of rapamycin (mTOR) contributes to the devastating features of cancer cells. Thus, mTOR is a critical therapeutic target and catalytic inhibitors are being investigated as anti-cancer drugs. Although mTOR inhibitors initially block cell proliferation, cell viability and migration in some cancer cells are quickly restored. Despite sustained inhibition of mTORC1/2 signaling, Akt, a kinase regulating cell survival and migration, regains phosphorylation at its regulatory sites. Mechanistically, mTORC1/2 inhibition promotes reorganization of integrin/focal adhesion kinase-mediated adhesomes, induction of IGFR/IR-dependent PI3K activation, and Akt phosphorylation via an integrin/FAK/IGFR-dependent process. This resistance mechanism contributes to xenograft tumor cell growth, which is prevented with mTOR plus IGFR inhibitors, supporting this combination as a therapeutic approach for cancers.

Pharmacologic Targeting of S6K1 in PTEN-Deficient Neoplasia.

Genetic S6K1 inactivation can induce apoptosis in PTEN-deficient cells. We analyzed the therapeutic potential of S6K1 inhibitors in PTEN-deficient T cell leukemia and glioblastoma. Results revealed that the S6K1 inhibitor LY-2779964 was relatively ineffective as a single agent, while S6K1-targeting AD80 induced cytotoxicity selectively in PTEN-deficient cells. In vivo, AD80 rescued 50% of mice transplanted with PTEN-deficient leukemia cells. Cells surviving LY-2779964 treatment exhibited inhibitor-induced S6K1 phosphorylation due to increased mTOR-S6K1 co-association, which primed the rapid recovery of S6K1 signaling. In contrast, AD80 avoided S6K1 phosphorylation and mTOR co-association, resulting in durable suppression of S6K1-induced signaling and protein synthesis. Kinome analysis revealed that AD80 coordinately inhibits S6K1 together with the TAM family tyrosine kinase AXL. TAM suppression by BMS-777607 or genetic knockdown potentiated cytotoxic responses to LY-2779964 in PTEN-deficient glioblastoma cells. These results reveal that combination targeting of S6K1 and TAMs is a potential strategy for treatment of PTEN-deficient malignancy.

mTORC1-Driven Tumor Cells Are Highly Sensitive to Therapeutic Targeting by Antagonists of Oxidative Stress.

mTORC1 is a central signaling node in controlling cell growth, proliferation, and metabolism that is aberrantly activated in cancers and certain cancer-associated genetic disorders, such as tuberous sclerosis complex (TSC) and sporadic lymphangioleiomyomatosis. However, while mTORC1-inhibitory compounds (rapamycin and rapalogs) attracted interest as candidate therapeutics, clinical trials have not replicated the promising findings in preclinical models, perhaps because these compounds tend to limit cell proliferation without inducing cell death. In seeking to address this issue, we performed a high-throughput screen for small molecules that could heighten the cytotoxicity of mTORC1 inhibitors. Here we report the discovery that combining inhibitors of mTORC1 and glutamate cysteine ligase (GCLC) can selectively and efficiently trigger apoptosis in Tsc2-deficient cells but not wild-type cells. Mechanistic investigations revealed that coinhibition of mTORC1 and GCLC decreased the level of the intracellular thiol antioxidant glutathione (GSH), thereby increasing levels of reactive oxygen species, which we determined to mediate cell death in Tsc2-deficient cells. Our findings offer preclinical proof of concept for a strategy to selectively increase the cytotoxicity of mTORC1 inhibitors as a therapy to eradicate tumor cells marked by high mTORC1 signaling, based on cotargeting a GSH-controlled oxidative stress pathway. Cancer Res; 76(16); 4816-27. ©2016 AACR.

Cardiovascular Autonomic Dysfunction in Mild and Advanced Parkinson's Disease

OBJECTIVE: The purpose of the present study was to investigate cardiovascular autonomic dysfunction in patients with Parkinson's disease (PD) with mild to severe stages of motor symptoms and to compare cardiovascular autonomic dysfunction between drug-naïve and dopaminergic drug-treated groups. METHODS: This study included 188 PD patients and 25 age-matched healthy controls who underwent head-up tilt-testing, 24-h ambulatory blood pressure (BP) monitoring and 24-h Holter monitoring. Autonomic function test results were evaluated among groups categorized by motor symptom severities (mild vs. moderate vs. severe) and treatment (drug-naïve or dopaminergic drug treatment). RESULTS: Orthostatic hypotension and supine hypertension were more frequent in patients with PD than in healthy controls. The frequencies of orthostatic hypotension, supine hypertension, nocturnal hypertension and non-dipping were not different among groups. Additionally, no significant differences were detected in supine BP, orthostatic BP change, nighttime BP, nocturnal BP dipping, or heart rate variabilities among groups. CONCLUSIONS: Cardiovascular autonomic dysfunction is not confined to moderate to severe PD patients, and starts early in the course of the disease in a high proportion of PD patients. In addition, dopaminergic drug treatments do not affect cardiovascular autonomic function.