bims-tubesc 2021-09-26 papers

bims-tubesc

Biomed News

on Molecular mechanisms in tuberous sclerosis

Issue of 2021‒09‒26
nineteen papers selected by
Marti Cadena Sandoval
metabolic-signalling.eu

Tuberous sclerosis complex-lymphangioleiomyomatosis involving several visceral organs: A case report.
Vigabatrin - new data on indications and safety in paediatric epilepsy.
Interleukin-6 mediates PSAT1 expression and serine metabolism in TSC2-deficient cells.
[Eosinophilic, solid, and cystic renal cell carcinoma (ESC-NZK)].
Story of the solitary subependymal giant cell astrocytoma: A case report and literature review.
Dysregulation of DPYSL2 expression by mTOR signaling in schizophrenia: multi-level study of postmortem brain.
A Case Report of Cystic Fibrosis Plus Tuberous Sclerosis: A Cautionary Tale Regarding Lung Transplantation.
Germline and sporadic mTOR pathway mutations in low-grade oncocytic tumor of the kidney.
Translational Aspects of the Mammalian Target of Rapamycin Complexes in Diabetic Nephropathy.
Retraction: Drosophila yakuba - Tsc1.
TSC2-mutant uterine sarcomas with JAZF1-SUZ12 fusions demonstrate hybrid features of endometrial stromal sarcoma and PEComa and are responsive to mTOR inhibition.
Dual mTORC1/2 inhibitor AZD2014 diminishes myeloid-derived suppressor cells accumulation in ovarian cancer and delays tumor growth.
Activation of Autophagy Ameliorates Age-Related Neurogenesis Decline and Neurodysfunction in Adult Mice.
Amino acids and mechanistic target of rapamycin regulate the fate of live engulfed cells.
Inhibition of Mammalian Target of Rapamycin Attenuates Recurrent Seizures Associated Cardiac Damage in a Zebrafish Kindling Model of Chronic Epilepsy.
Body fatness and mTOR pathway activation of breast cancer in the Women's Circle of Health Study.
STAT3 contributes to cisplatin resistance, modulating EMT markers, and the mTOR signaling in lung adenocarcinoma.
Co-treatment With Everolimus, an mTOR-Specific Antagonist, or Downregulation of ELK1 Enhances the Sensitivity of Pancreatic Cancer Cells to Genistein.
KARATE: PKA-induced KRAS4B-RHOA-mTORC2 supercomplex phosphorylates AKT in insulin signaling and glucose homeostasis.

World J Clin Cases. 2021 Aug 26. 9(24): 7085-7091

Tuberous sclerosis complex-lymphangioleiomyomatosis involving several visceral organs: A case report.

Hong-Bin Chen, Xiao-Hong Xu, Cai-Gui Yu, Meng-Ting Wan, Chuang-Li Feng, Zhi-Yu Zhao, Dan-E Mei, Jin-Ling Chen.

  BACKGROUND: Lymphangioleiomyomatosis (LAM) is a rare cystic lung disease characterized by the proliferation, metastasis, and infiltration of smooth muscle cells in the lung and other tissues, which can be associated with tuberous sclerosis complex (TSC). The disorder of TSC has a variable expression, and there is great phenotypic variability.CASE SUMMARY: A 32-year-old Chinese woman with a history of multiple renal angioleiomyolipoma presented with a productive cough persisting for over 2 wk. High-resolution chest computed tomography revealed interstitial changes, multiple pulmonary bullae, bilateral pulmonary nodules, and multiple fat density areas of the inferior mediastinum. Conventional and contrast ultrasonography revealed multiple high echogenic masses of the liver, kidneys, retroperitoneum, and inferior mediastinum. These masses were diagnosed as angiomyolipomas. Pathology through thoracoscopic lung biopsy confirmed LAM. Furthermore, high-throughput genome sequencing of peripheral blood DNA confirmed the presence of a heterozygous mutation, c.1831C>T (p.Arg611Trp), of the TSC2 gene. The patient was diagnosed with TSC-LAM.
CONCLUSION: We highlight a rare case of TSC-LAM and the first report of a mediastinum lymphangioleiomyoma associated with TSC-LAM.

Keywords:  Angioleiomyolipoma; Case report; Contrast ultrasonography; High-resolution chest computed tomography; Lymphangioleiomyomatosis; Tuberous sclerosis complex

DOI:  https://doi.org/10.12998/wjcc.v9.i24.7085
Neurol Neurochir Pol. 2021 Sep 20.

Vigabatrin - new data on indications and safety in paediatric epilepsy.

Weronika Golec, Elżbieta Sołowiej, Jolanta Strzelecka, Elżbieta Jurkiewicz, Sergiusz Jóźwiak.

  Vigabatrin (VGB), a second-generation antiepileptic drug, is effective for the treatment of infantile spasms and focal seizures, primarily in tuberous sclerosis complex (TSC) patients. However, reports of adverse events of VGB, including VGB-associated visual field loss and brain abnormalities in neuroimaging, have raised concerns about the broader use of VGB and thus significantly limited its application. The goal of this review was to summarise the recent therapeutic guidelines, the use of VGB in focal seizures and new VGB applications as a disease-modifying treatment in TSC patients. Moreover, we discuss the current opinions on potential VGB-associated toxicity and the safety of VGB.

Keywords:  VGB-associated brain abnormalities; VGB-associated visual field loss; focal seizures; infantile spasms; preventive treatment; tuberous sclerosis complex; vigabatrin

DOI:  https://doi.org/10.5603/PJNNS.a2021.0063
Proc Natl Acad Sci U S A. 2021 09 28. pii: e2101268118. [Epub ahead of print]118(39):

Interleukin-6 mediates PSAT1 expression and serine metabolism in TSC2-deficient cells.

Ji Wang, Harilaos Filippakis, Thomas Hougard, Heng Du, Chenyang Ye, Heng-Jia Liu, Long Zhang, Khadijah Hindi, Shefali Bagwe, Julie Nijmeh, John M Asara, Wei Shi, Souheil El-Chemaly, Elizabeth P Henske, Hilaire C Lam.

  Tuberous sclerosis complex (TSC) and lymphangioleiomyomatosis (LAM) are caused by aberrant mechanistic Target of Rapamycin Complex 1 (mTORC1) activation due to loss of either TSC1 or TSC2 Cytokine profiling of TSC2-deficient LAM patient-derived cells revealed striking up-regulation of Interleukin-6 (IL-6). LAM patient plasma contained increased circulating IL-6 compared with healthy controls, and TSC2-deficient cells showed up-regulation of IL-6 transcription and secretion compared to wild-type cells. IL-6 blockade repressed the proliferation and migration of TSC2-deficient cells and reduced oxygen consumption and extracellular acidification. U-13C glucose tracing revealed that IL-6 knockout reduced 3-phosphoserine and serine production in TSC2-deficient cells, implicating IL-6 in de novo serine metabolism. IL-6 knockout reduced expression of phosphoserine aminotransferase 1 (PSAT1), an essential enzyme in serine biosynthesis. Importantly, recombinant IL-6 treatment rescued PSAT1 expression in the TSC2-deficient, IL-6 knockout clones selectively and had no effect on wild-type cells. Treatment with anti-IL-6 (αIL-6) antibody similarly reduced cell proliferation and migration and reduced renal tumors in Tsc2 +/- mice while reducing PSAT1 expression. These data reveal a mechanism through which IL-6 regulates serine biosynthesis, with potential relevance to the therapy of tumors with mTORC1 hyperactivity.

Keywords:  interleukin 6; lymphangioleiomyomatosis; mTORC1; phosphoserine aminotransferase 1 (PSAT1); tuberous sclerosis complex

DOI:  https://doi.org/10.1073/pnas.2101268118
Pathologe. 2021 Sep 22.

[Eosinophilic, solid, and cystic renal cell carcinoma (ESC-NZK)].

Arndt Hartmann, Abbas Agaimy.

  Despite its descriptive name, eosinophilic, solid, and cystic renal cell carcinoma (ESC-RCC) represents a distinctive epithelial renal tumor entity defined by characteristic clinicopathological and molecular features. ESC-RCC occurs predominantly in women and is characterized in the majority of cases by sporadic (somatic) TSC mutations. A small subset of cases, however, affects patients with TSC germline mutations (tuberous sclerosis syndrome). TSC mutations have therefore been shown to be pathogenetic in this type of tumor. Most tumors present as small (pT1) well circumscribed but not encapsulated lesions with variable macrocystic spaces on their cut surface. Immunohistochemically, their CD117-/CK7-/CK20+ profile is characteristic. Although the tumor cell nuclei of the ESC-RCC occasionally correspond to ISUP/WHO grade 2-3, these tumors are essentially indolent with aggressive cases being only rarely observed. Single case reports have documented effective treatment of aggressive cases with mTOR inhibitors. ESC-RCC needs to be distinguished from a variety of eosinophilic RCC types with secondary cystic changes including cystic SDH-deficient RCC, the recently proposed eosinophilic vacuolated tumor (EVT; also mTOR-related), oncocytoma, and low-grade oncocytic tumor (LOT). The generally indolent behavior and frequent TSC/mTOR alterations in ESC-RCC, EVT, and some LOTs raise the question of whether these lesions represent independent tumor entities or are merely morphological variants on the spectrum of eosinophilic low-grade TSC/mTOR-related neoplasms.

Keywords:  Eosinophilic renal tumors; Human mTOR protein; Kidney neoplasms; TOR serine-threonine kinases; Tuberous sclerosis

DOI:  https://doi.org/10.1007/s00292-021-00998-7
Clin Neuropathol. 2021 Sep 20.

Story of the solitary subependymal giant cell astrocytoma: A case report and literature review.

Mahjabeen Khan, Miguel A Guzman, Aline Tanios.

Subependymal giant cell astrocytoma (SEGA) is the characteristic benign, slow-growing brain tumor seen in tuberous sclerosis (TS). There are several case reports of a diagnosis of SEGA in patients with no clinical or radiological diagnosis of TS. However, there is limited literature describing the tumor genetics in such cases. We report a case of a 17-year-old girl who was diagnosed with SEGA bearing the TSC2 mutation, while testing negative for TSC mutations on germline testing. We also did a literature review of studies that reported the genetics behind solitary SEGAs. Genetic testing of both the tumor itself and germline genetic testing can provide valuable information with clinical implications, for example, the basis for the need of close surveillance in TS patients.

DOI: https://doi.org/10.5414/NP301406
Neurosci Res. 2021 Sep 17. pii: S0168-0102(21)00206-6. [Epub ahead of print]

Dysregulation of DPYSL2 expression by mTOR signaling in schizophrenia: multi-level study of postmortem brain.

Ryuta Izumi, Mizuki Hino, Atsuko Nagaoka, Risa Shishido, Akiyoshi Kakita, Mikio Hoshino, Yasuto Kunii, Hirooki Yabe.

  The mechanistic target of rapamycin (mTOR)-signaling and dihydropyrimidinase-like 2 (DPYSL2), which are increasingly gaining attention as potential therapeutic targets for schizophrenia, are connected via Cap-dependent translation of the 5'TOP motif. We quantified the expression of molecules constituting the mTOR-signaling and DPYSL2 in the prefrontal cortex (PFC) and superior temporal gyrus (STG) of postmortem brain tissue samples from 24 patients with schizophrenia and 32 control individuals and conducted association analysis to examine abnormal regulation of DPYSL2 expression by the mTOR-signaling in schizophrenia. The average ribosomal protein S6 (S6) levels in the PFC and STG were lower in patients with schizophrenia (p < 0.01). DPYSL2 expression showed a significant positive correlation with phospho-S6 expression levels, which were effectors of mTOR translational regulation, and the correlation slope between phospho-S6 and DPYSL2 expressions differed between cases and controls. Association analyses of these mTOR-signaling and DPYSL2 alterations with genetic polymorphisms and the clinical profile suggested that certain genetic variants of DPYSL2 require high mTOR-signaling activity. Thus, the findings confirmed decreased S6 expression levels in schizophrenia and supported the relationship between the mTOR-signaling and DPYSL2 via 5'TOP Cap-dependent translation, thus providing insights connecting the two major schizophrenia treatment strategies associated with the mTOR-signaling and DPYSL2.

Keywords:  DPYSL2; RPS6; mTOR; postmortem-brain; schizophrenia

DOI:  https://doi.org/10.1016/j.neures.2021.09.004
Transplant Proc. 2021 Sep 18. pii: S0041-1345(21)00553-4. [Epub ahead of print]

A Case Report of Cystic Fibrosis Plus Tuberous Sclerosis: A Cautionary Tale Regarding Lung Transplantation.

Franco A Laghi, Marina Saad, Erin M Lowery.

BACKGROUND: Cystic fibrosis (CF) and tuberous sclerosis complex (TSC) are 2 rare genetic diseases that often affect the lungs. Pulmonary compromise in TSC or CF can be severe enough to require lung transplantation. In rare instances patients with CF undergo pneumonectomy to control recurrent lung infections and lung necrosis affecting one lung more than the other. Lung transplantation in these patients is exceedingly rare because preexistent pneumonectomy increases the risk of lung transplant-associated morbidity and mortality.CASE PRESENTATION: We present the case of a young woman with co-occurrence of TSC and CF, who underwent left-sided pneumonectomy and, approximately 2 years later, right-sided single lung transplant. The posttransplant clinical course was complicated by phrenic nerve injury, ventilator dependency, Aspergillus endocarditis with embolic shower, and death. Pretransplant pneumonectomy, Aspergillus colonization, and posttransplant phrenic nerve injury contributed to the complex postoperative course, ventilatory dependence, and poor outcome.
CONCLUSION: This cautionary case should alert physicians on the challenges associated with single lung transplant in patients with preexistent pneumonectomy.

DOI: https://doi.org/10.1016/j.transproceed.2021.08.022
Mod Pathol. 2021 Sep 20.

Germline and sporadic mTOR pathway mutations in low-grade oncocytic tumor of the kidney.

Payal Kapur, Ming Gao, Hua Zhong, Suneetha Chintalapati, Midori Mitui, Spencer D Barnes, Qinbo Zhou, Jeffrey Miyata, Deyssy Carrillo, Venkat S Malladi, Dinesh Rakheja, Ivan Pedrosa, Lin Xu, Lisa Kinch, James Brugarolas.

Low-grade oncocytic tumor (LOT) of the kidney is a recently described entity with poorly understood pathogenesis. Using next-generation sequencing (NGS) and complementary approaches, we provide insight into its biology. We describe 22 LOT corresponding to 7 patients presenting with a median age of 75 years (range 63-86 years) and male to female ratio 2:5. All 22 tumors demonstrated prototypical microscopic features. Tumors were well-circumscribed and solid. They were composed of sheets of tumor cells in compact nests. Tumor cells had eosinophilic cytoplasm, round to oval nuclei (without nuclear membrane irregularities), focal subtle perinuclear halos, and occasional binucleation. Sharply delineated edematous stromal islands were often observed. Tumor cells were positive for PAX8, negative for CD117, and exhibited diffuse and strong cytokeratin-7 expression. Six patients presented with pT1 tumors. At a median follow-up of 29 months, four patients were alive without recurrence (three patients had died from unrelated causes). All tumors were originally classified as chromophobe renal cell carcinoma, eosinophilic variant (chRCC-eo). While none of the patients presented with known syndromic features, one patient with multiple bilateral LOTs was subsequently found to have a likely pathogenic germline TSC1 mutation. Somatic, likely activating, mutations in MTOR and RHEB were identified in all other evaluable LOTs. As assessed by phospho-S6 and phospho-4E-BP1, mTOR complex 1 (mTORC1) was activated across all cases but to different extent. MTOR mutant LOT exhibited lower levels of mTORC1 activation, possibly related to mTORC1 dimerization and the preservation of a wild-type MTOR copy (retained chromosome 1). Supporting its distinction from related entities, gene expression analyses showed that LOT clustered separately from classic chRCC, chRCC-eo, and RO. In summary, converging mTORC1 pathway mutations, mTORC1 complex activation, and a distinctive gene expression signature along with characteristic phenotypic features support LOT designation as a distinct entity with both syndromic and non-syndromic cases associated with an indolent course.

DOI: https://doi.org/10.1038/s41379-021-00896-6
Antioxid Redox Signal. 2021 Sep 21.

Translational Aspects of the Mammalian Target of Rapamycin Complexes in Diabetic Nephropathy.

Alaa Abou Daher, Sahar Alkhansa, William S Azar, Rim Rafeh, Hilda E Ghadieh, Assaad Antoine Eid.

SIGNIFICANCE: Despite the many efforts put into understanding diabetic nephropathy (DN), direct treatments for DN have yet to be discovered. Understanding the mechanisms behind DN is an essential step in the development of novel therapeutic regimens. The mTOR pathway has emerged as an important candidate in the quest for drug discovery because of its role in regulating growth, proliferation, as well as protein and lipid metabolism. Recent Advances: Kidney cells have been found to rely on basal autophagy for survival and for conserving kidney integrity. Recent studies have shown that diabetes induces renal autophagy deregulation, leading to kidney injury. Hyper-activation of the mTOR pathway and oxidative stress have been suggested to play a role in diabetes-induced autophagy imbalance.CRITICAL ISSUES: A detailed understanding of the role of mTOR signaling in diabetes-associated complications is of major importance in the search for a cure. In this review, we provide evidence that mTOR is heavily implicated in diabetes-induced kidney injury. We suggest possible mechanisms through which mTOR exerts its negative effects by increasing insulin resistance, upregulating oxidative stress, and inhibiting autophagy.
FUTURE DIRECTIONS: Increased oxidative stress and autophagy deregulation are both deeply embedded in DN. However, the mechanisms controlling oxidative stress and autophagy are not well understood. While Akt/mTOR signaling seems to play an important role in oxidative stress and autophagy, further investigation is required to uncover the details of this signaling pathway.

DOI: https://doi.org/10.1089/ars.2021.0217
MicroPubl Biol. 2021 ;2021

Retraction: Drosophila yakuba - Tsc1.

[This retracts the article DOI: 10.17912/micropub.biology.000407.].

DOI: https://doi.org/10.17912/micropub.biology.000470
Mod Pathol. 2021 Sep 24.

TSC2-mutant uterine sarcomas with JAZF1-SUZ12 fusions demonstrate hybrid features of endometrial stromal sarcoma and PEComa and are responsive to mTOR inhibition.

Sarah Chiang, Varshini Vasudevaraja, Jonathan Serrano, Colin J R Stewart, Esther Oliva, Amir Momeni-Boroujeni, Achim A Jungbluth, Arnaud Da Cruz Paula, Edaise M da Silva, Britta Weigelt, Kay J Park, Robert A Soslow, Rajmohan Murali, Lora H Ellenson, Ryma Benayed, Marc Ladanyi, Nadeem R Abu-Rustum, Mark A Dickson, Seth Cohen, Carol Aghajanian, Martee L Hensley, Cheng-Han Lee, Matija Snuderl, Jason A Konner.

Uterine perivascular epithelioid cell tumor (PEComa) is a rare mesenchymal neoplasm that occasionally shares morphologic and immunohistochemical overlap with low- and high-grade endometrial stromal sarcoma (LGESS and HGESS). In this study, we sought to characterize the clinical, morphologic, genetic, and epigenetic features of five uterine sarcomas that display histologic features of LGESS, HGESS, and PEComa. All tumors demonstrated epithelioid cells often associated with a low-grade spindled component resembling LGESS, with both regions expressing CD10, ER, PR, variable HMB45, and Melan-A immunoreactivity, and strong cathepsin K and pS6 expression. Targeted massively parallel sequencing analysis revealed the presence of somatic TSC2 mutations in all five cases, of which four harbored concurrent or consecutive JAZF1-SUZ12 gene fusions. Unsupervised hierarchical clustering analysis of methylation profiles of TSC2-mutant uterine sarcomas (n = 4), LGESS (n = 10), and HGESS (n = 12) demonstrated two clusters consisting of (1) all LGESS and TSC2-mutant uterine sarcomas and (2) all HGESS. KEGG pathway analysis detected methylation differences in genes involved in PI3K/AKT, calcium, and Rap1 signaling. TSC2-mutant uterine sarcomas were responsive to hormone suppression, and mTOR inhibition demonstrated clinical benefit in four patients with these neoplasms. Our results suggest that these tumors represent histologically distinctive LGESS with TSC2 mutations. TSC2 mutations and JAZF1-SUZ12 fusion may help diagnose these tumors and possibly direct effective treatment.

DOI: https://doi.org/10.1038/s41379-021-00922-7
Cancer Lett. 2021 Sep 21. pii: S0304-3835(21)00464-X. [Epub ahead of print]

Dual mTORC1/2 inhibitor AZD2014 diminishes myeloid-derived suppressor cells accumulation in ovarian cancer and delays tumor growth.

Ruyu Pi, Yang Yang, Xiaoyi Hu, Hongyi Li, Houhui Shi, Yu Liu, Xi Wang, An Tong, Tianqi Lu, Yuquan Wei, Xia Zhao, Xiawei Wei.

  Mechanistic target of rapamycin (mTOR) forms two distinct complexes, mTOR complex 1 (mTORC1) and mTORC2. Here we investigated the antitumor effect of dual mTORC1/2 inhibitor AZD2014 on epithelial ovarian cancer (EOC) and its potential effect on immunosuppressive myeloid-derived suppressor cells (MDSCs). Immunohistochemical analysis of mTORC1 and mTORC2 was performed on a human ovarian cancer tissue microarray. High mTORC2 expression level was associated with shorter survival in EOC, whereas mTORC1 was not correlate with patients' prognosis. AZD2014 suppressed mTOR signaling pathway in ovarian cancer cells, inhibited proliferation and induced G1-phase cell cycle arrest and apoptosis. In tumor-bearing mice, AZD2014 treatment limited tumor growth, reduced peritoneal ascites, and prolonged survival. AZD2014 specifically reduced MDSCs migration and accumulation in EOC peritoneal fluid but not in the spleen. Moreover, subsequent AZD2014 treatment after cisplatin chemotherapy delayed EOC recurrence. Collectively, we observed that high mTORC2 expression level in EOC indicated a poor prognosis. Remarkably, in tumor-bearing mice, AZD2014 diminished MDSC accumulation and delayed tumor growth and recurrence.

Keywords:  MDSC; Ovarian cancer; mTOR inhibitor

DOI:  https://doi.org/10.1016/j.canlet.2021.09.017
Stem Cell Rev Rep. 2021 Sep 21.

Activation of Autophagy Ameliorates Age-Related Neurogenesis Decline and Neurodysfunction in Adult Mice.

Na Yang, Xueqin Liu, Xiaojie Niu, Xiaoqiang Wang, Rong Jiang, Na Yuan, Jianrong Wang, Chengwu Zhang, Kah-Leong Lim, Li Lu.

  Adult neurogenesis is the ongoing generation of functional new neurons from neural progenitor cells (NPCs) in the mammalian brain. However, this process declines with aging, which is implicated in the recession of brain function and neurodegeneration. Understanding the mechanism of adult neurogenesis and stimulating neurogenesis will benefit the mitigation of neurodegenerative diseases. Autophagy, a highly conserved process of cellular degradation, is essential for maintaining cellular homeostasis and normal function. Whether and how autophagy affects adult neurogenesis remains poorly understood. In present study, we revealed a close connection between impaired autophagy and adult neurogenetic decline. Expression of autophagy-related genes and autophagic activity were significantly declined in the middle-adult subventricular/subgranular zone (SVZ/SGZ) homogenates and cultured NPCs, and inhibiting autophagy by siRNA interference resulted in impaired proliferation and differentiation of NPCs. Conversely, stimulating autophagy by rapamycin not only revitalized the viability of middle-adult NPCs, but also facilitated the neurogenesis in middle-adult SVZ/SGZ. More importantly, autophagic activation by rapamycin also ameliorated the olfactory sensitivity and cognitional capacities in middle-adult mice. Taken together, our results reveal that compromised autophagy is involved in the decline of adult neurogenesis, which could be reversed by autophagy activation. It also shed light on the regulation of adult neurogenesis and paves the way for developing a therapeutic strategy for aging and neurodegenerative diseases.

Keywords:  Adult neurogenesis; Autophagy; Neural progenitor cell; Rapamycin; mTOR

DOI:  https://doi.org/10.1007/s12015-021-10265-0
FASEB J. 2021 Oct;35(10): e21909

Amino acids and mechanistic target of rapamycin regulate the fate of live engulfed cells.

Sung Eun Kim, Justin Zhang, Enoch Jiang, Michael Overholtzer.

  Metabolic stress contributes to the regulation of cell death in normal and diseased tissues. While different forms of cell death are known to be regulated by metabolic stress, how the cell engulfment and killing mechanism entosis is regulated is not well understood. Here we find that the death of entotic cells is regulated by the presence of amino acids and activity of the mechanistic target of rapamycin (mTOR). Amino acid withdrawal or mTOR inhibition induces apoptosis of engulfed cells and blocks entotic cell death that is associated with the lipidation of the autophagy protein microtubule-associated protein light chain 3 (LC3) to entotic vacuoles. Two other live cell engulfment programs, homotypic cell cannibalism (HoCC) and anti-CD47 antibody-mediated phagocytosis, known as phagoptosis, also undergo a similar vacuole maturation sequence involving LC3 lipidation and lysosome fusion, but only HoCC involves mTOR-dependent regulation of vacuole maturation and engulfed cell death similar to entosis. We further find that the regulation of cell death by mTOR is independent of autophagy activation and instead involves the 4E-BP1/2 proteins that are known regulators of mRNA translation. Depletion of 4E-BP1/2 proteins can restore the mTOR-regulated changes of entotic death and apoptosis rates of engulfed cells. These results identify amino acid signaling and the mTOR-4E-BP1/2 pathway as an upstream regulation mechanism for the fate of live engulfed cells formed by entosis and HoCC.

Keywords:  amino acids; cell death; entosis; mTOR; metabolism

DOI:  https://doi.org/10.1096/fj.202100870R
J Neuroimmune Pharmacol. 2021 Sep 19.

Inhibition of Mammalian Target of Rapamycin Attenuates Recurrent Seizures Associated Cardiac Damage in a Zebrafish Kindling Model of Chronic Epilepsy.

Supriya Sharma, Anil Kumar Rana, Aditi Sharma, Damanpreet Singh.

  Sudden Unexpected Death in Epilepsy (SUDEP) is primarily linked with the cardiac irregularities that occur due to recurrent seizures. Our previous studies found a role of mTOR pathway activation in seizures-linked cardiac damage in a rat model. In continuation to the earlier work, the present study was devised to explore the role of rapamycin (mTOR inhibitor and clinically used immunosuppressive agent) in a zebrafish kindling model and associated cardiac damage. Adult zebrafish were incubated with increasing concentrations of rapamycin (1, 2 and, 4 μM), followed by pentylenetetrazole (PTZ) exposure to record seizure latency and severity. In another experiment, zebrafish were subjected to a standardized PTZ kindling protocol. The kindled fish were treated daily with rapamycin for up to 25 days, along with PTZ to record seizure severity. At the end, zebrafish heart was excised for carbonylation assay, gene expression, and protein quantification studies. In the acute PTZ convulsion test, treatment with rapamycin showed a significant increase in seizure latency and decreased seizure severity without any change in seizure incidence. Treatment with rapamycin also reduced the severity of seizures in kindled fish. The cardiac expressions of gpx, nppb, kcnh2, scn5a, mapk8, stat3, rps6 and ddit were decreased, whereas the levels of trxr2 and beclin 1 were increased following rapamycin treatment in kindled fish. Furthermore, rapamycin treatment also decreased p-mTOR expression and protein carbonyls level in the fish cardiac tissue. The present study concluded that rapamycin reduces seizures and associated cardiac damage by inhibiting mTOR activation in the zebrafish kindling model.

Keywords:  Cardiac tissue; Epilepsy; Mammalian target of rapamycin; Oxidative stress; Stat3; Sudden Unexpected Death in Epilepsy

DOI:  https://doi.org/10.1007/s11481-021-10021-8
NPJ Breast Cancer. 2020 Sep 21. 6(1): 45

Body fatness and mTOR pathway activation of breast cancer in the Women's Circle of Health Study.

Ting-Yuan David Cheng, Angela R Omilian, Song Yao, Pamela V Sanchez, Latasia Z Polk, Weizhou Zhang, Susmita Datta, Wiam Bshara, Rochelle Payne Ondracek, Warren Davis, Song Liu, Chi-Chen Hong, Elisa V Bandera, Thaer Khoury, Christine B Ambrosone.

Energy imbalance has an important role in breast cancer prognosis. Hyperactive mechanistic Target of Rapamycin (mTOR) pathway is associated with breast tumor growth, but the extent to which body fatness is associated with mTOR pathway activities in breast cancer is unclear. We performed immunostaining for mTOR, phosphorylated (p)-mTOR, p-AKT, and p-p70S6K in tumor tissue from 590 women (464 African Americans/Blacks and 126 Whites) with newly diagnosed invasive breast cancer in the Women's Circle of Health Study. Anthropometric measures were taken by study staff, and body composition was measured by bioelectrical impedance analysis. Linear regressions were used to estimate percent differences in protein expression between categories of body mass index (BMI), waist circumference, waist/hip ratio, fat mass, fat mass index, and percent body fat. We observed that BMI ≥ 35.0 vs. <25 kg/m2 was associated with 108.3% (95% CI = 16.9%-270.9%) and 101.8% (95% CI = 17.0%-248.8%) higher expression in p-mTOR and normalized p-mTOR, i.e., p-mTOR/mTOR, respectively. Quartiles 4 vs. 1 of waist/hip ratio was associated with 41.8% (95% CI = 5.81%-89.9%) higher mTOR expression. Similar associations were observed for the body fat measurements, particularly in patients with estrogen receptor-negative (ER-) tumors, but not in those with ER+ tumors, although the differences in associations were not significant. This tumor-based study found positive associations between body fatness and mTOR pathway activation, evident by a p-mTOR expression, in breast cancer. Our findings suggest that mTOR inhibition can be a treatment strategy to prevent the recurrence of these tumors in obese individuals.

DOI: https://doi.org/10.1038/s41523-020-00187-4
Neoplasia. 2021 Sep 17. pii: S1476-5586(21)00068-3. [Epub ahead of print]23(10): 1048-1058

STAT3 contributes to cisplatin resistance, modulating EMT markers, and the mTOR signaling in lung adenocarcinoma.

Ana Paula Morelli, Tharcísio Citrângulo Tortelli, Mariana Camargo Silva Mancini, Isadora Carolina Betim Pavan, Luiz Guilherme Salvino Silva, Matheus Brandemarte Severino, Daniela Campos Granato, Nathalie Fortes Pestana, Luis Gustavo Saboia Ponte, Guilherme Francisco Peruca, Bianca Alves Pauletti, Daniel Francisco Guimarães Dos Santos, Leandro Pereira de Moura, Rosângela Maria Neves Bezerra, Adriana Franco Paes Leme, Roger Chammas, Fernando Moreira Simabuco.

  Lung cancer is the second leading cause of cancer death worldwide and is strongly associated with cisplatin resistance. The transcription factor signal transducer and activator of transcription 3 (STAT3) is constitutively activated in cancer cells and coordinates critical cellular processes as survival, self-renewal, and inflammation. In several types of cancer, STAT3 controls the development, immunogenicity, and malignant behavior of tumor cells while it dictates the responsiveness to radio- and chemotherapy. It is known that STAT3 phosphorylation at Ser727 by mechanistic target of rapamycin (mTOR) is necessary for its maximal activation, but the crosstalk between STAT3 and mTOR signaling in cisplatin resistance remains elusive. In this study, using a proteomic approach, we revealed important targets and signaling pathways altered in cisplatin-resistant A549 lung adenocarcinoma cells. STAT3 had increased expression in a resistance context, which can be associated with a poor prognosis. STAT3 knockout (SKO) resulted in a decreased mesenchymal phenotype in A549 cells, observed by clonogenic potential and by the expression of epithelial-mesenchymal transition markers. Importantly, SKO cells did not acquire the mTOR pathway overactivation induced by cisplatin resistance. Consistently, SKO cells were more responsive to mTOR inhibition by rapamycin and presented impairment of the feedback activation loop in Akt. Therefore, rapamycin was even more potent in inhibiting the clonogenic potential in SKO cells and sensitized to cisplatin treatment. Mechanistically, STAT3 partially coordinated the cisplatin resistance phenotype via the mTOR pathway in non-small cell lung cancer. Thus, our findings reveal important targets and highlight the significance of the crosstalk between STAT3 and mTOR signaling in cisplatin resistance. The synergic inhibition of STAT3 and mTOR potentially unveil a potential mechanism of synthetic lethality to be explored for human lung cancer treatment.

Keywords:  Cisplatin; Lung cancer; Proteomics; Rapamycin; STAT3; mTOR

DOI:  https://doi.org/10.1016/j.neo.2021.08.003
Front Cell Dev Biol. 2021 ;9 633035

Co-treatment With Everolimus, an mTOR-Specific Antagonist, or Downregulation of ELK1 Enhances the Sensitivity of Pancreatic Cancer Cells to Genistein.

Tianyu Li, Tiantao Kuang, Zhaoshuo Yang, Qiqi Zhang, Wen Zhang, Yue Fan.

  Genistein is a natural isoflavone with pharmacological or potentially anti-tumor properties. However, the resistance of cancer cells to genistein remains a major obstacle. This study focused on the mechanism implicated in the resistance of pancreatic cancer (PC) cells to genistein and the mechanism of action. First, key molecules and signaling pathways related to genistein resistance in PC cells were explored using bioinformatics tools. DEP domain containing MTOR interacting protein (DEPTOR), a typical inhibitor of the mammalian target of rapamycin (mTOR) signaling, was predicted to be poorly expressed in the genistein-resistant PC cells. Thereafter, genistein-resistant PC cells (Panc-1 and PaCa) were constructed. Altered expression of DEPTOR was introduced in cells, and everolimus (ELM), an mTOR-specific antagonist, was administrated in cells as well to examine their roles in genistein resistance. The cell apoptosis was examined in vitro and in vivo in mouse xenograft tumors. The upstream regulator of DEPTOR was predicted via bioinformatic tools. The bioinformatic analyses showed that the PI3K/AKT/mTOR signaling pathway was activated in the setting of DEPTOR downregulation in genistein-resistant PC cells. DEPTOR overexpression reduced the 50% inhibiting concentration (IC50) of genistein in PC cells and suppressed mTOR phosphorylation, and it increased caspase-3 activity, LDH release and apoptosis in PC cells. ELM treatment enhanced the sensitivity of PC cells to genistein in vitro and it strengthened the tumor-eliminating role of genistein in mice. ETS transcription factor ELK1 (ELK1), a transcription factor that negatively regulated DEPTOR transcription, was suppressed by genistein. Upregulation of ELK1 suppressed DEPTOR transcription and reduced the genistein sensitivity of cells, and it also blocked the genistein-sensitizing roles of ELM in PC cells. In conclusion, this study demonstrated that ELK1 reduces DEPTOR transcription, leading to mTOR phosphorylation and the drug resistance of PC cells.

Keywords:  DEPTOR; Elk1; everolimus; genistein; mTOR; pancreatic cancer

DOI:  https://doi.org/10.3389/fcell.2021.633035
Mol Cell. 2021 Sep 14. pii: S1097-2765(21)00735-8. [Epub ahead of print]

KARATE: PKA-induced KRAS4B-RHOA-mTORC2 supercomplex phosphorylates AKT in insulin signaling and glucose homeostasis.

Hiroshi Senoo, Daisuke Murata, May Wai, Kenta Arai, Wakiko Iwata, Hiromi Sesaki, Miho Iijima.

  AKT is a serine/threonine kinase that plays an important role in metabolism, cell growth, and cytoskeletal dynamics. AKT is activated by two kinases, PDK1 and mTORC2. Although the regulation of PDK1 is well understood, the mechanism that controls mTORC2 is unknown. Here, by investigating insulin receptor signaling in human cells and biochemical reconstitution, we found that insulin induces the activation of mTORC2 toward AKT by assembling a supercomplex with KRAS4B and RHOA GTPases, termed KARATE (KRAS4B-RHOA-mTORC2 Ensemble). Insulin-induced KARATE assembly is controlled via phosphorylation of GTP-bound KRAS4B at S181 and GDP-bound RHOA at S188 by protein kinase A. By developing a KARATE inhibitor, we demonstrate that KRAS4B-RHOA interaction drives KARATE formation. In adipocytes, KARATE controls insulin-dependent translocation of the glucose transporter GLUT4 to the plasma membrane for glucose uptake. Thus, our work reveals a fundamental mechanism that activates mTORC2 toward AKT in insulin-regulated glucose homeostasis.

Keywords:  AKT; KRAS GTPase; PKA; RHOA GTPase; insulin; mTORC2

DOI:  https://doi.org/10.1016/j.molcel.2021.09.001