Metformin overcomes chemoresistance by regulating stemness via KLF4 in oral squamous cell carcinoma.

OBJECTIVE: Chemoresistance is a common event after chemotherapy, including oral squamous cell carcinoma (OSCC). Accumulated evidence suggests that the cancer stemness significantly contributes to therapy resistance. An unresolved question remains regarding how to effectively overcome OSCC chemoresistance by targeting stemness. This study aims to investigate the antitumor effect of metformin and clarify the potential molecular mechanisms. METHODS: Cellular models resistant to chemotherapy were established, and their viability and sphere-forming ability were assessed using CCK-8 and soft agar formation assays, respectively. RNA-seq and Western blotting analyses were employed to delve into the molecular pathways. Furthermore, to corroborate the inhibitory effects of metformin and cisplatin at an animal level, a subcutaneous tumor transplantation model was instituted. RESULTS: Metformin as a monotherapy exhibited inhibition of stemness traits via Krüppel-like factor 4 (KLF4). Metformin and cisplatin can synergically inhibit cell proliferation and induce cell apoptosis. Animal experiments confirmed the inhibitory effect of cisplatin and metformin on tumor in mice. CONCLUSION: Our study proposes a potential therapeutic approach of combining chemotherapy with metformin to overcome chemoresistance in OSCC.

Nociceptive adenosine A2A receptor on trigeminal nerves orchestrates CGRP release to regulate the progression of oral squamous cell carcinoma.

Oral squamous cell carcinoma (OSCC) associated pain commonly predicts adverse events among patients. This clinical feature indicates the engagement of nociceptors on sensory neurons during the development of malignancy. However, it is yet to be determined if targeting oncometabolite-associated nociception processes can hinder OSCC progression. In this study, we reported that nociceptive endings infiltrating both clinical samples and mouse tumor xenografts were associated with poorer clinical outcomes and drove tumor progression in vivo, as evidenced by clinical tissue microarray analysis and murine lingual denervation. We observed that the OSCC microenvironment was characteristic of excessive adenosine due to CD73 upregulation which negatively predicted clinical outcomes in the TCGA-HNSC patient cohort. Notably, such adenosine concentrative OSCC niche was associated with the stimulation of adenosine A2A receptor (A2AR) on trigeminal ganglia. Antagonism of trigeminal A2AR with a selective A2AR inhibitor SCH58261 resulted in impeded OSCC growth in vivo. We showed that trigeminal A2AR overstimulation in OSCC xenograft did not entail any changes in the transcription level of CGRP in trigeminal ganglia but significantly triggered the release of CGRP, an effect counteracted by SCH58261. We further demonstrated the pro-tumor effect of CGRP by feeding mice with the clinically approved CGRP receptor antagonist rimegepant which inhibited the activation of ERK and YAP. Finally, we diminished the impact of CGRP on OSCC with istradefylline, a clinically available drug that targets neuronal A2AR. Therefore, we established trigeminal A2AR-mediated CGRP release as a promising druggable circuit in OSCC treatment.

Type 17 immune response promotes oral epithelial cell proliferation in periodontitis.

OBJECTIVES: This study aims to investigate the effects of type 17 immune response on the proliferation of oral epithelial cells in periodontitis. DESIGN: A time-dependent ligature induced periodontitis mouse model was utilized to explore gingival hyperplasia and the infiltration of interleukin 17A (IL-17A) positive cells. Immunohistochemistry and flow cytometry were employed to determine the localization and expression of IL-17A in the ligature induced periodontitis model. A pre-existing single-cell RNA sequencing dataset, comparing individuals affected by periodontitis with healthy counterparts, was reanalyzed to evaluate IL-17A expression levels. We examined proliferation markers, including proliferating cell nuclear antigen (PCNA), signal transducer and activator of transcription (STAT3), Yes-associated protein (YAP), and c-JUN, in the gingival and tongue epithelium of the periodontitis model. An anti-IL-17A agent was administered daily to observe proliferative changes in the oral mucosa within the periodontitis model. Cell number quantification, immunofluorescence, and western blot analyses were performed to assess the proliferative responses of human normal oral keratinocytes to IL-17A treatment in vitro. RESULTS: The ligature induced periodontitis model exhibited a marked infiltration of IL-17A-positive cells, alongside significant increase in thickness of the gingival and tongue epithelium. IL-17A triggers the proliferation of human normal oral keratinocytes, accompanied by upregulation of PCNA, STAT3, YAP, and c-JUN. The administration of an anti-IL-17A agent attenuated the proliferation in oral mucosa. CONCLUSIONS: These findings indicate that type 17 immune response, in response to periodontitis, facilitates the proliferation of oral epithelial cells, thus highlighting its crucial role in maintaining the oral epithelial barrier.

Shaoxia: a web-based interactive analysis platform for single cell RNA sequencing data.

BACKGROUND: In recent years, Single-cell RNA sequencing (scRNA-seq) is increasingly accessible to researchers of many fields. However, interpreting its data demands proficiency in multiple programming languages and bioinformatic skills, which limited researchers, without such expertise, exploring information from scRNA-seq data. Therefore, there is a tremendous need to develop easy-to-use software, covering all the aspects of scRNA-seq data analysis. RESULTS: We proposed a clear analysis framework for scRNA-seq data, which emphasized the fundamental and crucial roles of cell identity annotation, abstracting the analysis process into three stages: upstream analysis, cell annotation and downstream analysis. The framework can equip researchers with a comprehensive understanding of the analysis procedure and facilitate effective data interpretation. Leveraging the developed framework, we engineered Shaoxia, an analysis platform designed to democratize scRNA-seq analysis by accelerating processing through high-performance computing capabilities and offering a user-friendly interface accessible even to wet-lab researchers without programming expertise. CONCLUSION: Shaoxia stands as a powerful and user-friendly open-source software for automated scRNA-seq analysis, offering comprehensive functionality for streamlined functional genomics studies. Shaoxia is freely accessible at http://www.shaoxia.cloud , and its source code is publicly available at https://github.com/WiedenWei/shaoxia .

The effects of land use types on microplastics in river water: A case study on the mainstream of the Wei River, China.

Microplastics are widely found in rivers and their sediments, which will cause harm to the water ecological environment. The Wei River is a first-class tributary of the Yellow River, the fifth largest river in the world, and has vulnerable ecological environment and most sediment in the world. However, understanding how anthropogenic activities and environmental factors affect the microplastics distribution in this river is not clear. Based on this, the spatiotemporal distribution of microplastics in the Wei River were investigated. The abundance of microplastics ranged from 1033 to 8333 items/m3 and from 120 to 840 items/kg in the water and in the sediment, respectively. Fibers and fragments were the main shapes of Wei River, microplastics less than 500 µm were the main sizes, and black and white/transparent were the main colors. In Wei River, the abundance of microplastics in urban areas was higher than that in agricultural areas and mountainous areas. Furthermore, the correlation analysis revealed that microplastic abundance in the water was related to anthropogenic activities (population density, per capita GDP and distance) and environmental factors (water temperature, NH3-N, ORP), while in the sediments was correlated with anthropogenic activities (per capita GDP) and environmental factors (water temperature and NH3-N). This study reveals new patterns in microplastic pollution in the Wei River, underscoring the need for targeted environmental strategies. Our findings provide novel insights into the characteristics and distribution of microplastics, significantly adding to the current understanding of riverine microplastic pollution.

Clinical and prognostic significance analysis of glycolysis-related genes in HNSCC.

BACKGROUND: Head and neck squamous cell carcinoma (HNSCC) represents one of the most malignant cancers worldwide, with poor survival. Experimental evidence implies that glycolysis/hypoxia is associated with HNSCC. In this study, we aimed to construct a novel glycolysis-/hypoxia-related gene (GHRG) signature for survival prediction of HNSCC. METHODS: A multistage screening strategy was used to establish the GHRG prognostic model by univariate/least absolute shrinkage and selection operator (LASSO)/step multivariate Cox regressions from The Cancer Genome Atlas cohort. A nomogram was constructed to quantify the survival probability. Correlations between risk score and immune infiltration and chemotherapy sensitivity were explored. RESULTS: We established a 12-GHRG mRNA signature to predict the prognosis in HNSCC patients. Patients in the high-risk score group had a much worse prognosis. The predictive power of the model was validated by external HNSCC cohorts, and the model was identified as an independent factor for survival prediction. Immune infiltration analysis showed that the high-risk score group had an immunosuppressive microenvironment. Finally, the model was effective in predicting chemotherapeutic sensitivity. CONCLUSIONS: Our study demonstrated that the GHRG model is a robust prognostic tool for survival prediction of HNSCC. Findings of this work provide novel insights for immune infiltration and chemotherapy of HNSCC, and may be applied clinically to guide therapeutic strategies.

Integrative analysis defines DDIT3 amplification as a correlative and essential factor for glioma malignancy.

Glioma, particularly glioblastoma multiforme (GBM), is a highly aggressive and lethal primary brain tumor with poor prognosis. Metabolic reprogramming and endoplasmic reticulum (ER) stress are two crucial factors contributing to glioma pathogenesis. However, the intricate coordination between these processes remains incompletely understood. Here, we conducted an integrative analysis to elucidate the nodal role of DNA Damage Inducible Transcript 3 (DDIT3) to couple metabolisms and stress responses in glioma. We demonstrated a positive association between DDIT3 amplification/enhanced expression with glioma malignancy, indicating its potential as a novel biomarker for prognosis and treatment stratification. Genomic and transcriptomic analyses further revealed the involvement of DDIT3 enhancement in glioma progression. Moreover, immune infiltration analysis showed that distinct DDIT3 expression groups had different immune microenvironment. Finally, in vitro validations confirmed the impact of DDIT3 on proliferation and migration of glioma cells. Our findings provide novel insights into the complex interplay between metabolic reprogramming and ER stress, and defines DDIT3 as a promising therapeutic target in glioma.

Comparative analysis of two arecoline-induced oral submucous fibrosis models.

OBJECTIVE: The limited understanding of the molecular mechanism for oral submucosal fibrosis (OSF) poses challenges to the development of effective prevention and treatment strategies. The lack of suitable animal models is a major hindrance. Therefore, this study aimed to address this issue by comparing commonly used arecoline-induced water drinking and injection mouse models. MATERIALS AND METHODS: The mice were subjected to two protocols: receiving 2 mg/mL arecoline in drinking water and 4 mg/mL arecoline saline solution injections every other day. Tissues were collected at regular 4-week intervals, with a final time point of 20 weeks. Stereo microscopy and histomorphological analysis were performed on live and harvested tissues, respectively. RESULTS: During arecoline treatment, collagen deposition and myofibroblast proliferation progressively increased in both models. Changes in the collagen I/III ratio indicated that both models exhibited characteristics of the early and intermediate stages of OSF after 20 weeks of arecoline induction. The water-drinking model also demonstrated multi-organ fibrosis involving the tongue, lungs, and small intestine. CONCLUSION: Both the water drinking and injection mouse models effectively induced OSF, but the water-drinking model better mirrored the observed pathogenesis in patients with OSF. These models provide valuable tools for investigating the mechanisms underlying OSF.

Clinical and molecular analysis of cilia-associated gene signature for prognostic prediction in glioma.

PURPOSE: Glioma is a highly malignant and unfavorable cancer in the brain. Recent evidence highlights the vital role of cilia-related pathways as novel regulators of glioma development. However, the prognostic potential of ciliary pathways in glioma is still ambiguous. In this study, we aim to construct a gene signature using cilia-related genes to facilitate the prognostication of glioma. METHODS: A multi-stage approach was employed to build the ciliary gene signature for prognostication of glioma. The strategy involved the implementation of univariate, LASSO, and stepwise multivariate Cox regression analyses based on TCGA cohort, followed by independent validation in CGGA and REMBRANDT cohort. The study further revealed molecular differences at the genomic, transcriptomic, and proteomic levels between distinct groups. RESULTS: A prognostic tool utilizing a 9-gene signature based on ciliary pathways was developed to assess the clinical outcomes of glioma patients. The risk scores generated by the signature demonstrated a negative correlation with patient survival rates. The validation of the signature in an independent cohort reinforced its prognostic capabilities. In-depth analysis uncovered distinctive molecular characteristics at the genomic, transcriptomic, and protein-interactive levels in the high- and low-risk groups. Furthermore, the gene signature was able to predict the sensitivity of glioma patients to conventional chemotherapeutic drugs. CONCLUSION: This study has established the utility of a ciliary gene signature as a reliable prognostic predictor of glioma patient survival. Findings not only enhance our comprehension of the intricate molecular mechanisms of cilia pathways in glioma, but also hold significant clinical implications in directing chemotherapeutic strategies.

Elevated GIGYF2 expression suppresses tumor migration and enhances sensitivity to temozolomide in malignant glioma.

Glioma is a common type of malignant and aggressive tumor in the brain. Despite progress on mechanistic studies, current understanding of the initiation and progression of glioma remains incomplete. GIGYF2 is a critical regulator in neural development and degeneration, however, its contribution in glioma is not yet elucidated. In this study, using an integrative approach spanning bioinformatic analysis and functional approaches, we explored the potential contribution of GIGYF2 in glioma. Bioinformatic data from public database and our cohort showed that GIGYF2 expression was closely associated with low glioma malignancy and better patient survival. Elevation of GIGYF2 expression impaired cell migration and enhanced temozolomide sensitivity of human glioma cells. We further establish its molecular mechanism by demonstrating that GIGYF2 inhibits MMP-9 mediated cell migration pathway and pro-survival AKT/Bax/Caspase-3 signaling. Our work identifies the suppressive role of GIGYF2 in gliomas, and clarifies the relationship between GIGYF2 expression and glioma malignancy, which may provide a potential target for future interventions.

Rheb-regulated mitochondrial pyruvate metabolism of Schwann cells linked to axon stability.

The metabolic coupling of Schwann cells (SCs) and peripheral axons is poorly understood. Few molecules in SCs are known to regulate axon stability. Using SC-specific Rheb knockout mice, we demonstrate that Rheb-regulated mitochondrial pyruvate metabolism is critical for SC-mediated non-cell-autonomous regulation of peripheral axon stability. Rheb knockout suppresses pyruvate dehydrogenase (PDH) activity (independently of mTORC1) and shifts pyruvate metabolism toward lactate production in SCs. The increased lactate causes age-dependent peripheral axon degeneration, affecting peripheral nerve function. Lactate, as an energy substrate and a potential signaling molecule, enhanced neuronal mitochondrial metabolism and energy production of peripheral nerves. Albeit beneficial to injured peripheral axons in the short term, we show that persistently increased lactate metabolism of neurons enhances ROS production, eventually damaging mitochondria, neuroenergetics, and axon stability. This study highlights the complex roles of lactate metabolism to peripheral axons and the importance of lactate homeostasis in preserving peripheral nerves.

Rheb mediates neuronal-activity-induced mitochondrial energetics through mTORC1-independent PDH activation.

Neuronal activity increases energy consumption and requires balanced production to maintain neuronal function. How activity is coupled to energy production remains incompletely understood. Here, we report that Rheb regulates mitochondrial tricarboxylic acid cycle flux of acetyl-CoA by activating pyruvate dehydrogenase (PDH) to increase ATP production. Rheb is induced by synaptic activity and lactate and dynamically trafficked to the mitochondrial matrix through its interaction with Tom20. Mitochondria-localized Rheb protein is required for activity-induced PDH activation and ATP production. Cell-type-specific gain- and loss-of-function genetic models for Rheb reveal reciprocal changes in PDH phosphorylation/activity, acetyl-CoA, and ATP that are not evident with genetic or pharmacological manipulations of mTORC1. Mechanistically, Rheb physically associates with PDH phosphatase (PDP), enhancing its activity and association with the catalytic E1α-subunit of PDH to reduce PDH phosphorylation and increase its activity. Findings identify Rheb as a nodal point that balances neuronal activity and neuroenergetics via Rheb-PDH axis.

Inhibition of mitochondrial carrier homolog 2 (MTCH2) suppresses tumor invasion and enhances sensitivity to temozolomide in malignant glioma.

BACKGROUND: Malignant glioma exerts a metabolic shift from oxidative phosphorylation (OXPHOs) to aerobic glycolysis, with suppressed mitochondrial functions. This phenomenon offers a proliferation advantage to tumor cells and decrease mitochondria-dependent cell death. However, the underlying mechanism for mitochondrial dysfunction in glioma is not well elucidated. MTCH2 is a mitochondrial outer membrane protein that regulates mitochondrial metabolism and related cell death. This study aims to clarify the role of MTCH2 in glioma. METHODS: Bioinformatic analysis from TCGA and CGGA databases were used to investigate the association of MTCH2 with glioma malignancy and clinical significance. The expression of MTCH2 was verified from clinical specimens using real-time PCR and western blots in our cohorts. siRNA-mediated MTCH2 knockdown were used to assess the biological functions of MTCH2 in glioma progression, including cell invasion and temozolomide-induced cell death. Biochemical investigations of mitochondrial and cellular signaling alternations were performed to detect the mechanism by which MTCH2 regulates glioma malignancy. RESULTS: Bioinformatic data from public database and our cohort showed that MTCH2 expression was closely associated with glioma malignancy and poor patient survival. Silencing of MTCH2 expression impaired cell migration/invasion and enhanced temozolomide sensitivity of human glioma cells. Mechanistically, MTCH2 knockdown may increase mitochondrial OXPHOs and thus oxidative damage, decreased migration/invasion pathways, and repressed pro-survival AKT signaling. CONCLUSION: Our work establishes the relationship between MTCH2 expression and glioma malignancy, and provides a potential target for future interventions.

LanCL1 promotes motor neuron survival and extends the lifespan of amyotrophic lateral sclerosis mice.

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease characterized by progressive loss of motor neurons. Improving neuronal survival in ALS remains a significant challenge. Previously, we identified Lanthionine synthetase C-like protein 1 (LanCL1) as a neuronal antioxidant defense gene, the genetic deletion of which causes apoptotic neurodegeneration in the brain. Here, we report in vivo data using the transgenic SOD1G93A mouse model of ALS indicating that CNS-specific expression of LanCL1 transgene extends lifespan, delays disease onset, decelerates symptomatic progression, and improves motor performance of SOD1G93A mice. Conversely, CNS-specific deletion of LanCL1 leads to neurodegenerative phenotypes, including motor neuron loss, neuroinflammation, and oxidative damage. Analysis reveals that LanCL1 is a positive regulator of AKT activity, and LanCL1 overexpression restores the impaired AKT activity in ALS model mice. These findings indicate that LanCL1 regulates neuronal survival through an alternative mechanism, and suggest a new therapeutic target in ALS.

Developmental and activity-dependent expression of LanCL1 confers antioxidant activity required for neuronal survival.

Production of reactive oxygen species (ROS) increases with neuronal activity that accompanies synaptic development and function. Transcription-related factors and metabolic enzymes that are expressed in all tissues have been described to counteract neuronal ROS to prevent oxidative damage. Here, we describe the antioxidant gene LanCL1 that is prominently enriched in brain neurons. Its expression is developmentally regulated and induced by neuronal activity, neurotrophic factors implicated in neuronal plasticity and survival, and oxidative stress. Genetic deletion of LanCL1 causes enhanced accumulation of ROS in brain, as well as development-related lipid, protein, and DNA damage; mitochondrial dysfunction; and apoptotic neurodegeneration. LanCL1 transgene protects neurons from ROS. LanCL1 protein purified from eukaryotic cells catalyzes the formation of thioether products similar to glutathione S-transferase. These studies reveal a neuron-specific glutathione defense mechanism that is essential for neuronal function and survival.

Genetic deletion of Rheb1 in the brain reduces food intake and causes hypoglycemia with altered peripheral metabolism.

Excessive food/energy intake is linked to obesity and metabolic disorders, such as diabetes. The hypothalamus in the brain plays a critical role in the control of food intake and peripheral metabolism. The signaling pathways in hypothalamic neurons that regulate food intake and peripheral metabolism need to be better understood for developing pharmacological interventions to manage eating behavior and obesity. Mammalian target of rapamycin (mTOR), a serine/threonine kinase, is a master regulator of cellular metabolism in different cell types. Pharmacological manipulations of mTOR complex 1 (mTORC1) activity in hypothalamic neurons alter food intake and body weight. Our previous study identified Rheb1 (Ras homolog enriched in brain 1) as an essential activator of mTORC1 activity in the brain. Here we examine whether central Rheb1 regulates food intake and peripheral metabolism through mTORC1 signaling. We find that genetic deletion of Rheb1 in the brain causes a reduction in mTORC1 activity and impairs normal food intake. As a result, Rheb1 knockout mice exhibit hypoglycemia and increased lipid mobilization in adipose tissue and ketogenesis in the liver. Our work highlights the importance of central Rheb1 signaling in euglycemia and energy homeostasis in animals.

PNAS4 knockout does not induce obviously neurocytes apoptosis and abnormal development in mice brain.

Apoptosis is one kind of programmed cell death and contributes to development of a variety of organs such as brain. PNAS4 has been reported to be a novel apoptosis-related gene. Overexpression and knocking down of PNAS4 would cause zebrafish and Xenopus lavis developmental abnormalities. But its function and apoptotic mechanism in mammals are still unknown. Here, we first reported that established PNAS4 CKO (conditional knock out) mice using recombineering technology. We prepared its polyclonal antibodies which recognized both myc-PNAS4 overexpression protein and WT and CKO mice brain tissue and MEFS cells with high titre and specificity. Further we detected that PNAS4 was highly expressed in the embryonic period. However, we observed neither neural structural abnormality nor apoptosis signal in PNAS4 CKO mice brain. Our data suggested that PNAS4 was not involved in mice brain development and apoptosis.

[The CD133 polyclonal antibody generation and cancer stem cells identification].

OBJECTIVE: To generate the cancer stem cells (CSCs) specific protein CD133 polyclonal antibody for the study of the biological characteristics of CSCs in tumor tissues and CSCs screening for the mouse model. METHODS: The extracellular peptide of the human CD133 was injected into rabbits to generate polyclonal antibody which was used for glioblastoma(GBM) Western blot and immunohistochemistry. RESULTS: The CD133 antiserum we made could detect both overexpressed myc-CD133 and endogenous CD133 efficiently by Western blot. Immunohistochemistry indicated that the CD133 polyclonal antibody can label CSCs in GBM sections. CONCLUSION: High efficient and specific CD133 antibody was generated successfully and could be used to label CSCs in tumor sections and screen CSCs for the mouse model.

Detection of human herpes virus 6B in patients with mesial temporal lobe epilepsy in West China and the possible association with elevated NF-κB expression.

BACKGROUND: There has been a long-standing suspicion that an association exists between mesial temporal lobe epilepsy (MTLE) and the herpes virus. Evidence for HHV-6B involvement has been reported. However, no investigation has been performed in China. METHODS: We used nested PCR and immunohistochemistry to detect viral DNA of human herpes virus (HHV)-6B, HHV-6A, herpes simplex virus (HSV)-1 and HSV-2 in resected brain tissues from patients with MTLE and control. A principal transcription factor, NF-κB, that is associated with the inflammatory response was also investigated by real-time PCR, western blotting and immunohistochemistry. RESULTS: HHV-6B DNA was detected in hippocampal samples from 9 out of 32 (28.1%) patients with MTLE and in 1 of 12 (8.3%) control samples. Immunoreactivity for HHV-6B was consistently present in MTLE patients positive for HHV-6 detected by PCR. Significant staining for HHV-6B antigen was distributed mainly around or in the nucleus of cells that morphologically resembled astrocytes and microglia. HHV-6B positivity was related to febrile convulsion history of patients with MTLE. The expression of NF-κB was up-regulated and distributed in the nucleus of glial cells in MTLE patients positive for HHV-6B. CONCLUSION: This study was first to find HHV-6B in MTLE patients from West China and demonstrate a possible association between HHV-6B positivity and activation of NF-κB. The detailed role of HHV-6B and its association with NF-κB in the development of chronic MTLE requires further investigation.

Rheb1 is required for mTORC1 and myelination in postnatal brain development.

mTor kinase is involved in cell growth, proliferation, and differentiation. The roles of mTor activators, Rheb1 and Rheb2, have not been established in vivo. Here, we report that Rheb1, but not Rheb2, is critical for embryonic survival and mTORC1 signaling. Embryonic deletion of Rheb1 in neural progenitor cells abolishes mTORC1 signaling in developing brain and increases mTORC2 signaling. Remarkably, embryonic and early postnatal brain development appears grossly normal in these Rheb1f/f,Nes-cre mice with the notable exception of deficits of myelination. Conditional expression of Rheb1 transgene in neural progenitors increases mTORC1 activity and promotes myelination in the brain. In addition the Rheb1 transgene rescues mTORC1 signaling and hypomyelination in the Rheb1f/f,Nes-cre mice. Our study demonstrates that Rheb1 is essential for mTORC1 signaling and myelination in the brain, and suggests that mTORC1 signaling plays a role in selective cellular adaptations, rather than general cellular viability.