Nuclear Nestin deficiency drives tumor senescence via lamin A/C-dependent nuclear deformation

At the nucleus of cancer: how the nuclear envelope controls tumor progression

Historically considered downstream effects of tumorigenesis-arising from changes in DNA content or chromatin organization-nuclear alterations have long been seen as mere prognostic markers within a genome-centric model of cancer. However, recent findings have placed the nuclear envelope (NE) at the forefront of tumor progression, highlighting its active role in mediating cellular responses to mechanical forces. Despite significant progress, the precise interplay between NE components and cancer progression remains under debate. In this review, we provide a comprehensive and up-to-date overview of how changes in NE composition affect nuclear mechanics and facilitate malignant transformation, grounded in the latest molecular and functional studies. We also review recent research that uses advanced technologies, including artificial intelligence, to predict malignancy risk and treatment outcomes by analyzing nuclear morphology. Finally, we discuss how progress in understanding nuclear mechanics has paved the way for mechanotherapy-a promising cancer treatment approach that exploits the mechanical differences between cancerous and healthy cells. Shifting the perspective on NE alterations from mere diagnostic markers to potential therapeutic targets, this review calls for further investigation into the evolving role of the NE in cancer, highlighting the potential for innovative strategies to transform conventional cancer therapies.

Phosphorylation of Lamin A/C regulates the structural integrity of the nuclear envelope

Dynamic disassembly and reconstruction of the nuclear lamina during entry and exit of mitosis, respectively, are pivotal steps in the proliferation of higher eukaryotic cells. Although numerous post-translational modifications of lamin proteins have been identified, key factors driving the nuclear lamina dynamics remain elusive. Here we identified CDK1-elicited phosphorylation sites on endogenous Lamin A/C and characterized their functions in regulation of the nuclear lamina. Specifically, mass spectrometry revealed CDK1-mediated phosphorylation of Lamin A/C at the N-terminal Thr19/Ser22 and the C-terminal Ser390/Ser392 during mitosis. Importantly, the phospho-mimicking 4D mutant T19D/S22D/S390D/S392D completely disrupted Lamin A filamentous structure in interphase cells. Conversely, the non-phosphorylatable mutant T19A/S22A and especially the 4A mutant T19A/S22A/S390A/S392A protected Lamin A from depolymerization during mitosis. These results suggest that phosphorylation and dephosphorylation of both N- and C-terminal sites regulate the nuclear lamina dynamics. Engineering the non-phosphorylatable mutant T19A/S22A into the endogenous LMNA gene resulted in nuclear abnormalities and micronucleus formation during telophase. Perturbation of the Lamin A phosphorylation is shown to prevent proper nuclear envelope dynamics and impair nuclear integrity. These findings reveal a previously undefined link between the CDK1-elicited Lamin A phosphorylation dynamics, nuclear envelope plasticity, and genomic stability during the cell cycle.

Surface Acoustic Wave-Enhanced Multi-View Acoustofluidic Rotation Cytometry (MARC) for Pre-Cytopathological Screening

Cytopathology, crucial in disease diagnosis, commonly uses microscopic slides to scrutinize cellular abnormalities. However, processing high volumes of samples often results in numerous negative diagnoses, consuming significant time and resources in healthcare. To address this challenge, a surface acoustic wave-enhanced multi-view acoustofluidic rotation cytometry (MARC) technique is developed for pre-cytopathological screening. MARC enhances cellular morphology analysis through comprehensive and multi-angle observations and amplifies subtle cell differences, particularly in the nuclear-to-cytoplasmic ratio, across various cell types and between cancerous and normal tissue cells. By prioritizing MARC-screened positive cases, this approach can potentially streamline traditional cytopathology, reducing the workload and resources spent on negative diagnoses. This significant advancement enhances overall diagnostic efficiency, offering a transformative vision for cytopathological screening.

Unveiling Potential Neurotoxic Mechansisms: Pb-Induced Activation of CDK5-p25 Signaling Axis in Alzheimer's Disease Development, Emphasizing CDK5 Inhibition and Formation of Toxic p25 Species

Alzheimer's disease (AD) is a complex neurodegenerative disorder with an etiology influenced by various genetic and environmental factors. Heavy metals, such as lead (Pb), have been implicated in AD pathogenesis, but the underlying mechanisms remain poorly understood. This study investigates the potential neurodegenerative role of Pb and amyloid β peptides (1-40 and 25-35) via their interaction with cyclin-dependent kinase 5 (CDK5) and its activator, p25, in an attempt to unravel the molecular basis of Pb-induced neurotoxicity in neuronal cells. To this end, a CDK5 inhibitor was utilized to selectively inhibit CDK5 activity and investigate its impact on neurodegeneration. The results revealed that Pb exposure led to elevated Pb uptake (56.7% at 15 μM Pb) and disturbances in intracellular calcium (19.6% increase upon Pb treatment). The results revealed a significant decrease in total antioxidant capacity (by 88.6% upon Pb treatment) and also elevation in protein carbonylation (by 26.2% upon Pb and Aβp's combination treatment), indicative of oxidative damage, suggesting an impaired cellular defence against oxidative stress and elevated DNA oxidative damage (178 pg/ml and 182 pg/ml of 8-OH-dG upon Pb and All treatment). Additionally, dysregulations in levels of calpain, p25-35 and CDK5 are observed and markers associated with antioxidant metabolism (phospho-Peroxiredoxin 1), DNA damage responses (phospho-ATM and phospho-p53), and nuclear membrane disruption (phospho-lamin A/C) were observed, supporting the role of Pb-induced CDK5-p25 signaling in AD pathogenesis. These findings shed light on the intricate molecular events underlying Pb-induced neurotoxicity and provide valuable insights into the mechanisms that contribute to AD development.

Intermediate, but not average: The unusual lives of the nuclear lamin proteins

The nuclear lamins are polymeric intermediate filament proteins that scaffold the nucleus and organize the genome in nearly all eukaryotic cells. This review focuses on the dynamic regulation of lamin filaments through their biogenesis, assembly, disassembly, and degradation. The lamins are unusually long-lived proteins under homeostatic conditions, but their turnover can be induced in select contexts that are highlighted in this review. Finally, we discuss recent investigations into the influence of laminopathy-linked mutations on the assembly, folding, and stability of the nuclear lamins.

Vimentin: from a cytoskeletal protein to a critical modulator of immune response and a target for infection

Vimentin is an intermediate filament protein that plays a role in cell processes, including cell migration, cell shape and plasticity, or organelle anchorage. However, studies from over the last quarter-century revealed that vimentin can be expressed at the cell surface and even secreted and that its implications in cell physiology largely exceed structural and cytoskeletal functions. Consequently, vimentin contributes to several pathophysiological conditions such as cancer, autoimmune and inflammatory diseases, or infection. In this review, we aimed at covering these various roles and highlighting vimentin implications in the immune response. We also provide an overview of how some microbes including bacteria and viruses have acquired the ability to circumvent vimentin functions in order to interfere with host responses and promote their uptake, persistence, and egress from host cells. Lastly, we discuss the therapeutic approaches associated with vimentin targeting, leading to several beneficial effects such as preventing infection, limiting inflammatory responses, or the progression of cancerous events.

The pathological potential of ependymal cells in mild traumatic brain injury

Mild traumatic brain injury (mTBI) is a common neurological condition affecting millions of individuals worldwide. Although the pathology of mTBI is not fully understood, ependymal cells present a promising approach for studying the pathogenesis of mTBI. Previous studies have revealed that DNA damage in the form of γH2AX accumulates in ependymal cells following mTBI, with evidence of widespread cellular senescence in the brain. Ependymal ciliary dysfunction has also been observed, leading to altered cerebrospinal fluid homeostasis. Even though ependymal cells have not been extensively studied in the context of mTBI, these observations reflect the pathological potential of ependymal cells that may underlie the neuropathological and clinical presentations of mTBI. This mini review explores the molecular and structural alterations that have been reported in ependymal cells following mTBI, as well as the potential pathological mechanisms mediated by ependymal cells that may contribute to overall dysfunction of the brain post-mTBI. Specifically, we address the topics of DNA damage-induced cellular senescence, dysregulation of cerebrospinal fluid homeostasis, and the consequences of impaired ependymal cell barriers. Moreover, we highlight potential ependymal cell-based therapies for the treatment of mTBI, with a focus on neurogenesis, ependymal cell repair, and modulation of senescence signaling pathways. Further insight and research in this field will help to establish the role of ependymal cells in the pathogenesis of mTBI and may lead to improved treatments that leverage ependymal cells to target the origins of mTBI pathology.

AKT2-mediated nuclear deformation leads to genome instability during epithelial-mesenchymal transition

Nuclear deformation has been observed in some cancer cells for decades, but its underlying mechanism and biological significance remain elusive. To address these questions, we employed human lung cancer A549 cell line as a model in context with transforming growth factor β (TGFβ)-induced epithelial-mesenchymal transition. Here, we report that nuclear deformation induced by TGFβ is concomitant with increased phosphorylation of lamin A at Ser390, defective nuclear lamina and genome instability. AKT2 and Smad3 serve as the downstream effectors for TGFβ to induce nuclear deformation. AKT2 directly phosphorylates lamin A at Ser390, whereas Smad3 is required for AKT2 activation upon TGFβ stimulation. Expression of the lamin A mutant with a substitution of Ser390 to Ala or suppression of AKT2 or Smad3 prevents nuclear deformation and genome instability induced by TGFβ. These findings reveal a molecular mechanism for TGFβ-induced nuclear deformation and establish a role of nuclear deformation in genome instability during epithelial-mesenchymal transition.

Enhanced Expression of a Novel Lamin A/C Splice Variant in Idiopathic Pulmonary Fibrosis Lung

In idiopathic pulmonary fibrosis (IPF), the normal delicate lung architecture is replaced with rigid extracellular matrix (ECM) as a result of the accumulation of activated myofibroblasts and excessive deposition of ECM. Lamins have a role in fostering mechanosignaling from the ECM to the nucleus. Although there is a growing number of studies on lamins and associated diseases, there are no prior reports linking aberrations in lamins with pulmonary fibrosis. Here, we discovered, through analysis of RNA sequencing data, a novel isoform of lamin A/C that is more highly expressed in IPF compared with control lung. This novel LMNA (lamin A/C) splice variant includes retained introns 10 and 11 and exons 11 and 12 as documented by rapid amplification of cDNA ends. We found that this novel isoform is induced by stiff ECM. To better clarify the specific effects of this novel isoform of lamin A/C and how it may contribute to the pathogenesis of IPF, we transduced the lamin transcript into primary lung fibroblasts and alveolar epithelial cells and found that it impacts several biological effects, including cell proliferation, senescence, cell contraction, and the transition of fibroblasts to myofibroblasts. We also observed that type II epithelial cells and myofibroblasts in the IPF lung exhibited wrinkled nuclei, and this is notable because this has not been previously described and is consistent with laminopathy-mediated cellular effects.

Overview of cellular homeostasis-associated nuclear envelope lamins and associated input signals

With the discovery of the role of the nuclear envelope protein lamin in human genetic diseases, further diverse roles of lamins have been elucidated. The roles of lamins have been addressed in cellular homeostasis including gene regulation, cell cycle, cellular senescence, adipogenesis, bone remodeling as well as modulation of cancer biology. Features of laminopathies line with oxidative stress-associated cellular senescence, differentiation, and longevity and share with downstream of aging-oxidative stress. Thus, in this review, we highlighted various roles of lamin as key molecule of nuclear maintenance, specially lamin-A/C, and mutated LMNA gene clearly reveal aging-related genetic phenotypes, such as enhanced differentiation, adipogenesis, and osteoporosis. The modulatory roles of lamin-A/C in stem cell differentiation, skin, cardiac regulation, and oncology have also been elucidated. In addition to recent advances in laminopathies, we highlighted for the first kinase-dependent nuclear lamin biology and recently developed modulatory mechanisms or effector signals of lamin regulation. Advanced knowledge of the lamin-A/C proteins as diverse signaling modulators might be biological key to unlocking the complex signaling of aging-related human diseases and homeostasis in cellular process.

TPX2 promotes ovarian tumorigenesis by interacting with Lamin A/C and affecting its stability

OBJECTIVE

Ovarian cancer (OC) is one of the fatal gynecologic malignancies. However, there are no effective prognostic or therapeutic indicators for OC. Herein, we aim to reveal the potential function of targeting protein for Xklp2 (TPX2) in OC progression.

METHODS

Immunohistochemical and bioinformatic analyses were used to evaluate the level of TPX2 in OC samples. Effects of TPX2 on cell proliferation, cell apoptosis and ROS production were evaluated in vivo and in vitro. Mass spectrometry, Co-IP and immunofluorescence assays were performed to identify and verify protein-protein interactions.

RESULTS

Our data showed that pathological overexpression (OE) of the TPX2 in OC could manifest a poor prognosis. Functional studies demonstrated that TPX2 silencing led to the suppression of cell proliferation in vitro and in vivo through an increase in reactive oxygen species (ROS) level and apoptosis, while TPX2 OE exhibited the opposite effect. Furthermore, by mass spectrometric analysis, we identified a novel interacting partner, Lamin A/C, for TPX2. Mechanistically, TPX2 regulated Lamin A/C's stability by modulating the level of phospho-Lamin A/C (Ser 22).

CONCLUSION

Our findings thus suggest that TPX2 may be a promising therapeutic target for OC.

Comparative analysis of markers for H2O2-induced senescence in renal tubular cells

To address what marker(s) is/are most suitable for determining renal cell senescence, cell area, granularity, cycle shift/arrest, SA-β-Gal, SIRT1 and p16 were evaluated after inducing senescence in HK-2 cells with 0.2-0.8 mM H₂O₂. Only cell area and granularity concentration-dependently increased at all time-points, whereas SA-β-Gal, SIRT1 and p16 showed significant coefficient of determination (R²) at two time-points. Cell granularity had significant correlation coefficient (R) with other six, whereas SA-β-Gal had significant R with five, and cell area, SIRT1 and p16 had significant R with four others. Comparing to SA-β-Gal, other markers had significantly lower fold-changes only at 72-h with 0.8 mM H₂O₂, whereas p16 provided greater fold-changes at 48-h with 0.4 and 0.8 mM H₂O₂. Therefore, cell area, granularity, SA-β-Gal and p16 may serve as the most suitable markers for determining H₂O₂-induced senescence in HK-2 renal cells, whereas other markers can be also used but with inferior quantitative precision.

Nestin prevents mesenchymal stromal cells from apoptosis in LPS-induced lung injury via inhibition of unfolded protein response sensor IRE1α

The clinical applications of MSC therapy have been intensely investigated in acute respiratory distress syndrome. However, clinical studies have fallen short of expectations despite encouraging preclinical results. One of the key problems is that transplanted stem cells can hardly survive in the harsh inflammatory environment. Prolonging the survival of transplanted MSCs might be a promising strategy to enhance the therapeutic efficacy of MSC therapy. Here, we identified Nestin, a class VI intermediate filament, as a positive regulator of MSC survival in the inflammatory microenvironment. We showed that Nestin knockout led to a significant increase of MSC apoptosis, which hampered the therapeutic effects in an LPS-induced lung injury model. Mechanistically, Nestin knockout induced a significant elevation of endoplasmic reticulum (ER) stress level. Further investigations showed that Nestin could bind to IRE1α and inhibit ER stress-induced apoptosis under stress. Furthermore, pretreatment with IRE1α inhibitor 4μ8C improved MSC survival and improved therapeutic effect. Our data suggests that Nestin enhances stem cell survival after transplantation by inhibiting ER stress-induced apoptosis, improving protection, and repair of the lung inflammatory injury.

LMNA Reduced Acquired Resistance to Erlotinib in NSCLC by Reversing the Epithelial-Mesenchymal Transition via the FGFR/MAPK/c-fos Signaling Pathway

For patients exhibiting non-small-cell lung cancer (NSCLC) with activating epidermal growth factor receptor (EGFR) mutations, epidermal growth factor receptor tyrosine kinase inhibitors (EGFR-TKIs) are a first-line treatment. However, most patients who initially responded to EGFR-TKIs eventually developed acquired resistance, limiting the effectiveness of therapy. It has long been known that epithelial-mesenchymal transition (EMT) leads to acquired resistance to EGFR-TKIs in NSCLC. However, the mechanisms underlying the resistance dependent on EMT are unknown. This research aimed to reveal the effects of LMNA in the regulation of acquired resistance to erlotinib by EMT in NSCLC. The acquired erlotinib-resistant cells (HCC827/ER) were induced by gradual increase of concentrations of erlotinib in erlotinib-sensitive HCC827 cells. RNA sequencing and bioinformatics analysis were performed to uncover the involvement of LMNA in the EMT process that induced acquired resistance to erlotinib. The effect of LMNA on cell proliferation and migration was measured by clone-formation, wound-healing, and transwell assays, respectively. The EMT-related protein, nuclear shape and volume, and cytoskeleton changes were examined by immunofluorescence. Western blot was used to identify the underlying molecular mechanism of LMNA regulation of EMT. HCC827/ER cells with acquired resistance to erlotinib underwent EMT and exhibited lower LMNA expression compared to parental sensitive cells. LMNA negatively regulated the expression of EMT markers; HCC827/ER cells showed a significant up-regulation of mesenchymal markers, such as CDH2, SNAI2, VIM, ZEB1, and TWIST1. The overexpression of LMNA in HCC827/ER cells significantly inhibited EMT and cell proliferation, and this inhibitory effect of LMNA was enhanced in the presence of 2.5 μM erlotinib. Furthermore, a decrease in LMNA expression resulted in a higher nuclear deformability and cytoskeletal changes. In HCC827/ER cells, AKT, FGFR, ERK1/2, and c-fos phosphorylation levels were higher than those in HCC827 cells; Furthermore, overexpression of LMNA in HCC827/ER cells reduced the phosphorylation of AKT, ERK1/2, c-fos, and FGFR. In conclusion, our findings first demonstrated that downregulation of LMNA promotes acquired EGFR-TKI resistance in NSCLC with EGFR mutations by EMT. LMNA inhibits cell proliferation and migration of erlotinib-resistant cells via inhibition of the FGFR/MAPK/c-fos signaling pathway. These findings indicated LMNA as a driver of acquired resistance to erlotinib and provided important information about the development of resistance to erlotinib treatment in NSCLC patients with EGFR mutations.

Combined alteration of lamin and nuclear morphology influences the localization of the tumor-associated factor AKTIP

Background

Lamins, key nuclear lamina components, have been proposed as candidate risk biomarkers in different types of cancer but their accuracy is still debated. AKTIP is a telomeric protein with the property of being enriched at the nuclear lamina. AKTIP has similarity with the tumor susceptibility gene TSG101. AKTIP deficiency generates genome instability and, in p53^−/− mice, the reduction of the mouse counterpart of AKTIP induces the exacerbation of lymphomas. Here, we asked whether the distribution of AKTIP is altered in cancer cells and whether this is associated with alterations of lamins.

Methods

We performed super-resolution imaging, quantification of lamin expression and nuclear morphology on HeLa, MCF7, and A549 tumor cells, and on non-transformed fibroblasts from healthy donor and HGPS (LMNA c.1824C > T p.Gly608Gly) and EDMD2 (LMNA c.775 T > G) patients. As proof of principle model combining a defined lamin alteration with a tumor cell setting, we produced HeLa cells exogenously expressing the HGPS lamin mutant progerin that alters nuclear morphology.

Results

In HeLa cells, AKTIP locates at less than 0.5 µm from the nuclear rim and co-localizes with lamin A/C. As compared to HeLa, there is a reduced co-localization of AKTIP with lamin A/C in both MCF7 and A549. Additionally, MCF7 display lower amounts of AKTIP at the rim. The analyses in non-transformed fibroblasts show that AKTIP mislocalizes in HGPS cells but not in EDMD2. The integrated analysis of lamin expression, nuclear morphology, and AKTIP topology shows that positioning of AKTIP is influenced not only by lamin expression, but also by nuclear morphology. This conclusion is validated by progerin-expressing HeLa cells in which nuclei are morphologically altered and AKTIP is mislocalized.

Conclusions

Our data show that the combined alteration of lamin and nuclear morphology influences the localization of the tumor-associated factor AKTIP. The results also point to the fact that lamin alterations per se are not predictive of AKTIP mislocalization, in both non-transformed and tumor cells. In more general terms, this study supports the thesis that a combined analytical approach should be preferred to predict lamin-associated changes in tumor cells. This paves the way of next translational evaluation to validate the use of this combined analytical approach as risk biomarker.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13046-022-02480-5.

Global crotonylome reveals hypoxia-mediated lamin A crotonylation regulated by HDAC6 in liver cancer

Lysine crotonylation is a recently discovered post-translation modification involved in transcription regulation, cell signal transduction, and other processes. Scientists have identified several crotonylases and decrotonylases of histones, including P300/CBP, HDACs, and SIRTs. However, the regulation of non-histone protein crotonylation remains unclear. In the current study, we verified that crotonylation was upregulated in hypoxia and promoted liver cancer cell growth. We performed TMT-labeled quantitative lysine crotonylome analysis in 12 pairs of hepatocellular carcinoma and adjacent liver tissue and identified 3,793 lysine crotonylation sites in 1,428 proteins. We showed that crotonylation of lamin A at the site of K265/270 maintains its subcellular position, promotes liver cancer cell proliferation, and prevents cellular senescence. Our data indicate that HDAC6 is the decrotonylase of lamin A and downregulated in response to hypoxia, resulting in lamin A K265/270cr. Taken together, our study reveals the lamin A crotonylation in liver cancer progression and fills the research gap in non-histone protein crotonylation function.

Lamin-A/C Is Modulated by the Involvement of Histamine-Mediated Calcium/Calmodulin-Dependent Kinase II in Lung Cancer Cells

Lamins are nuclear envelope proteins involved in various cellular functions, such as DNA modulation, cellular differentiation, and development. In this study, we investigate the role of histamine in lung cancer biology. Since it is known that lamin-A/C is negatively regulated in lung cancer, we hypothesize that histamine signaling is related to nuclear lamin-A/C regulation and cancer progression. Our findings reveal that histamine stimulation enhances lamin-A/C expression in lung cancer cells. Lamin-A/C expression is dependent on histamine-mediated intracellular calcium signaling and subsequent calcium/calmodulin-dependent kinase II (Ca/CaMKII) activation. The nuclear protein nestin, which stabilizes lamin-A/C expression, is also modulated by Ca/CaMKII. However, histamine-mediated lamin-A/C expression is independent of Akt/focal adhesion kinase or autophagy signaling. Histamine stimulation attenuates lung cancer motility in the presence of enhanced lamin-A/C expression. In conclusion, we propose a regulatory mechanism that accounts for the modulation of lamin-A/C levels through the involvement of Ca/CaMKII in cancer cells and provides molecular evidence of histamine signaling in lamin-A/C biology.

Restructuring of Lamina-Associated Domains in Senescence and Cancer

Induction of cellular senescence or cancer is associated with a reshaping of the nuclear envelope and a broad reorganization of heterochromatin. At the periphery of mammalian nuclei, heterochromatin is stabilized at the nuclear lamina via lamina-associated domains (LADs). Alterations in the composition of the nuclear lamina during senescence lead to a loss of peripheral heterochromatin, repositioning of LADs, and changes in epigenetic states of LADs. Cancer initiation and progression are also accompanied by a massive reprogramming of the epigenome, particularly in domains coinciding with LADs. Here, we review recent knowledge on alterations in chromatin organization and in the epigenome that affect LADs and related genomic domains in senescence and cancer.

Mesenchymal stromal cells attenuate alveolar type 2 cells senescence through regulating NAMPT-mediated NAD metabolism

Background

Idiopathic pulmonary fibrosis (IPF) is a chronic and progressive deadly fibrotic lung disease with high prevalence and mortality worldwide. The therapeutic potential of mesenchymal stem cells (MSCs) in pulmonary fibrosis may be attributed to the strong paracrine, anti-inflammatory, anti-apoptosis and immunoregulatory effects. However, the mechanisms underlying the therapeutic effects of MSCs in IPF, especially in terms of alveolar type 2 (AT2) cells senescence, are not well understood. The purpose of this study was to evaluate the role of MSCs in NAD metabolism and senescence of AT2 cells in vitro and in vivo.

Methods

MSCs were isolated from human bone marrow. The protective effects of MSCs injection in pulmonary fibrosis were assessed via bleomycin mouse models. The senescence of AT2 cells co-cultured with MSCs was evaluated by SA-β-galactosidase assay, immunofluorescence staining and Western blotting. NAD+ level and NAMPT expression in AT2 cells affected by MSCs were determined in vitro and in vivo. FK866 and NAMPT shRNA vectors were used to determine the role of NAMPT in MSCs inhibiting AT2 cells senescence.

Results

We proved that MSCs attenuate bleomycin-induced pulmonary fibrosis in mice. Senescence of AT2 cells was alleviated in MSCs-treated pulmonary fibrosis mice and when co-cultured with MSCs in vitro. Mechanistic studies showed that NAD+ and NAMPT levels were rescued in AT2 cells co-cultured with MSCs and MSCs could suppress AT2 cells senescence mainly via suppressing lysosome-mediated NAMPT degradation.

Conclusions

MSCs attenuate AT2 cells senescence by upregulating NAMPT expression and NAD+ levels, thus exerting protective effects in pulmonary fibrosis.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-021-02688-w.

Loss of lamin-B1 and defective nuclear morphology are hallmarks of astrocyte senescence in vitro and in the aging human hippocampus

The increase in senescent cells in tissues, including the brain, is a general feature of normal aging and age-related pathologies. Senescent cells exhibit a specific phenotype, which includes an altered nuclear morphology and transcriptomic changes. Astrocytes undergo senescence in vitro and in age-associated neurodegenerative diseases, but little is known about whether this process also occurs in physiological aging, as well as its functional implication. Here, we investigated astrocyte senescence in vitro, in old mouse brains, and in post-mortem human brain tissue of elderly. We identified a significant loss of lamin-B1, a major component of the nuclear lamina, as a hallmark of senescent astrocytes. We showed a severe reduction of lamin-B1 in the dentate gyrus of aged mice, including in hippocampal astrocytes, and in the granular cell layer of the hippocampus of post-mortem human tissue from non-demented elderly. The lamin-B1 reduction was associated with nuclear deformations, represented by an increased incidence of invaginated nuclei and loss of nuclear circularity in senescent astrocytes in vitro and in the aging human hippocampus. We also found differences in lamin-B1 levels and astrocyte nuclear morphology between the granular cell layer and polymorphic layer in the elderly human hippocampus, suggesting an intra-regional-dependent aging response of human astrocytes. Moreover, we described senescence-associated impaired neuritogenic and synaptogenic capacity of mouse astrocytes. Our findings show that reduction of lamin-B1 is a conserved feature of hippocampal cells aging, including astrocytes, and shed light on significant defects in nuclear lamina structure which may contribute to astrocyte dysfunctions during aging.

Changes of stem cell niche during experimental pituitary tumor development

To investigate the putative stem cell/tumor stem cell (SC/TSC) niche contribution to hyperplasic/adenomatous pituitary lesions, we analyzed variation in the pituitary stem cell population during the development of experimental pituitary tumors. Pituitary tumors were induced in female F344 rats with estradiol benzoate for 5, 10, 20 and 30 days. Cells positive for GFRa2, Sox2, Sox9, Nestin, CD133 and CD44 were identified in the marginal zone and in the adenoparenchyma in both control and 30D groups, with predominant adenoparenchyma localization of GRFa2 and SOX9 found in tumoral pituitaries. GFRa2, Nestin, CD133 and CD44 were upregulated at the initial stages of tumor growth, whereas Sox9 significantly decreased at 5D, with Sox2 remaining invariable during the hyperplasic/adenomatous development. In addition, isolated pituispheres from normal and tumoral pituitary glands enriched in SC/TSC were characterized. Pituispheres from the 30D glands were positive for the above-mentioned markers and showed a significant increase in the proliferation. In conclusion, our data revealed pituitary SC pool fluctuations during hyperplastic/adenomatous development, with differential localization of the SC/TSC niche in this process. These findings may help to provide a better understanding of these cell populations, which is crucial for achieving advancements in the field of pituitary tumor biology.

Assembly and recognition of keratins: A structural perspective

Keratins are one of the major components of cytoskeletal network and assemble into fibrous structures named intermediate filaments (IFs), which are important for maintaining the mechanical properties of cells and tissues. Over the past decades, evidence has shown that the functions of keratins go beyond providing mechanical support for cells, they interact with multiple cellular components and are widely involved in the pathways of cell proliferation, differentiation, motility and death. However, the structural details of keratins and IFs are largely missing and many questions remain regarding the mechanisms of keratin assembly and recognition. Here we briefly review the current structural models and assembly of keratins as well as the interactions of keratins with the binding partners, which may provide a structural view for understanding the mechanisms of keratins in the biological activities and the related diseases.

Nestin promotes pulmonary fibrosis via facilitating recycling of TGF-β receptor I

Background

Idiopathic pulmonary fibrosis (IPF) is a progressive fibrotic lung disease that is characterised by aberrant proliferation of activated myofibroblasts and pathological remodelling of the extracellular matrix. Previous studies have revealed that the intermediate filament protein nestin plays key roles in tissue regeneration and wound healing in different organs. Whether nestin plays a critical role in the pathogenesis of IPF needs to be clarified.

Methods

Nestin expression in lung tissues from bleomycin-treated mice and IPF patients was determined. Transfection with nestin short hairpin RNA vectors in vitro that regulated transcription growth factor (TGF)-β/Smad signalling was conducted. Biotinylation assays to observe plasma membrane TβRI, TβRI endocytosis and TβRI recycling after nestin knockdown were performed. Adeno-associated virus serotype (AAV)6-mediated nestin knockdown was assessed in vivo.

Results

We found that nestin expression was increased in a murine pulmonary fibrosis model and IPF patients, and that the upregulated protein primarily localised in lung α-smooth muscle actin-positive myofibroblasts. Mechanistically, we determined that nestin knockdown inhibited TGF-β signalling by suppressing recycling of TβRI to the cell surface and that Rab11 was required for the ability of nestin to promote TβRI recycling. In vivo, we found that intratracheal administration of AAV6-mediated nestin knockdown significantly alleviated pulmonary fibrosis in multiple experimental mice models.

Conclusion

Our findings reveal a pro-fibrotic function of nestin partially through facilitating Rab11-dependent recycling of TβRI and shed new light on pulmonary fibrosis treatment.

Nestin regulates the vesicular trafficking system by promoting Rab11-dependent recycling of TβRI and thereby contributes to the progression of pulmonary fibrosis. Precise targeting of nestin may represent a potential therapeutic strategy for IPF.https://bit.ly/3zO75c3

Nestin Is Required for Spindle Assembly and Cell-Cycle Progression in Glioblastoma Cells

Nestin, a class IV intermediate filament protein, is generally considered as a putative marker of neural stem and progenitor cells in the central nervous system. Glioma is a common type of adult brain tumors, and glioblastoma (GBM) represents the most aggressive form of glioma. Here, we report that Nestin expression is significantly upregulated in human GBM, compared with other types of glioma. Nestin knockdown or deletion in U251 cells and tumor cells from GBM patients derived xenografts resulted in G2-M arrest, finally leading to apoptosis in tumor cells. Using proximity-dependent biotin identification method, we identified βII-tubulin as an interacting protein of Nestin in U251 cells. Nestin stabilized βII-tubulin in U251 cells through physical interaction. Knockdown of Nestin or βII-tubulin disrupted spindle morphology in tumor cells. Our studies further revealed that Nestin deficiency in U251 cells and GBM PDX cells repressed tumor growth upon transplantation. Finally, we found that Nestin deficiency sensitized GBM cells to microtubule-destabilizing drugs such as vinblastine and vincristine. Our studies demonstrate the essential functions and underlying mechanisms of Nestin in the growth and drug response of GBM cells. IMPLICATIONS: Through interaction with βII-tubulin, Nestin facilitates cell-cycle progression and spindle assembly of tumor cells in glioblastoma.

Cellular senescence in musculoskeletal homeostasis, diseases, and regeneration

Emerging insights into cellular senescence highlight the relevance of senescence in musculoskeletal disorders, which represent the leading global cause of disability. Cellular senescence was initially described by Hayflick et al. in 1961 as an irreversible nondividing state in in vitro cell culture studies. We now know that cellular senescence can occur in vivo in response to various stressors as a heterogeneous and tissue-specific cell state with a secretome phenotype acquired after the initial growth arrest. In the past two decades, compelling evidence from preclinical models and human data show an accumulation of senescent cells in many components of the musculoskeletal system. Cellular senescence is therefore a defining feature of age-related musculoskeletal disorders, and targeted elimination of these cells has emerged recently as a promising therapeutic approach to ameliorate tissue damage and promote repair and regeneration of the skeleton and skeletal muscles. In this review, we summarize evidence of the role of senescent cells in the maintenance of bone homeostasis during childhood and their contribution to the pathogenesis of chronic musculoskeletal disorders, including osteoporosis, osteoarthritis, and sarcopenia. We highlight the diversity of the senescent cells in the microenvironment of bone, joint, and skeletal muscle tissue, as well as the mechanisms by which these senescent cells are involved in musculoskeletal diseases. In addition, we discuss how identifying and targeting senescent cells might positively affect pathologic progression and musculoskeletal system regeneration.

Lamin post-translational modifications: emerging toggles of nuclear organization and function

Nuclear lamins are ancient type V intermediate filaments with diverse functions that include maintaining nuclear shape, mechanosignaling, tethering and stabilizing chromatin, regulating gene expression, and contributing to cell cycle progression. Despite these numerous roles, an outstanding question has been how lamins are regulated. Accumulating work indicates that a range of lamin post-translational modifications (PTMs) control their functions both in homeostatic cells and in disease states such as progeria, muscular dystrophy, and viral infection. Here, we review the current knowledge of the diverse types of PTMs that regulate lamins in a site-specific manner. We highlight methods that can be used to characterize lamin PTMs whose functions are currently unknown and provide a perspective on the future of the lamin PTM field.

Polystyrene nanoplastics exposure caused defective neural tube morphogenesis through caveolae-mediated endocytosis and faulty apoptosis

Growing evidence demonstrated that bioaccumulation of polystyrene nanoplastics (PS-NPs) in various organisms including human beings caused destructive effects on health. Nanoplastics may adversely affect fetal development potentially since they can pass through the placental barrier. However, very little has been known about the embryonic toxicity of polystyrene nanoplastics, especially in embryonic neurulation, the early developmental stage of the fetus, as well as the corresponding mechanisms. In this study, we first observed that 60- or 900-nm PS-NPs (especially 60-nm PS-NPs) could cross mouse placentas and affect developing mice fetuses. To avoid the indirect adverse effects derived from the restricted placenta, we employed early chick embryos as a developmental model to evaluate direct adverse effects of PS-NPs on embryo/fetal development, revealing suppressive effects on embryo development and an increased frequency of congenital abnormalities (especially in the nervous system), including neural tube defects. Thus, we focused on the potential negative effects of PS-NPs on neurulation, the earliest stage of nervous system development. Using caveolin-1 immunofluorescent staining of SH-SY5Y cells exposed to PS-NPs-GFP, we demonstrated that PS-NPs were internalized by SH-SY5Y cells via caveolae-mediated endocytosis. Transmission electron microscopy; LC3B immunofluorescent staining; and Atg7, Atg5, p62 and LC3B western blot results revealed that autophagy was activated in SH-SY5Y cells exposed to PS-NPs. However, PS-NPs were not degraded by the autophagic-lysosomal system given the lack of LAMP1 changes and minimal PS-NPs-GFP and LAMP1 colocalization. Furthermore, the cytoplasmic accumulation of PS-NPs caused faulty apoptotic cell death in SH-SY5Y cells and the developing neural tube as revealed by c-caspase3 immunofluorescent staining. Thus, defective neural tube morphogenesis, as demonstrated by neural tube defects, occurred during embryogenesis in the context of PS-NP exposure.

miR-940 is a new biomarker with tumor diagnostic and prognostic value

miR-940 is a microRNA located on chromosome 16p13.3, which has varying degrees of expression imbalance in many diseases. It binds to the 3′ untranslated region (UTR) and affects the transcription or post-transcriptional regulation of target protein-coding genes. For a diversity of cellular processes, including cell proliferation, migration, invasion, apoptosis, epithelial-to-mesenchymal transition (EMT), cell cycle, and osteogenic differentiation, miR-940 can affect them not only by regulating protein-coding genes but also long non-coding RNAs (lncRNAs) and circular RNAs (circRNAs) in pathways. Intriguingly, miR-940 participates in four pathways that affect cancer development, including the Wnt/β-catenin pathway, mitogen-activated protein kinase (MAPK) pathway, PD-1 pathway, and phosphatidylinositol 3-kinase (PI3K)-Akt pathway. Importantly, the expression of miR-940 is intimately correlated with the diagnosis and prognosis of tumor patients, as well as to the efficacy of tumor chemotherapy drugs. In conclusion, our main purpose is to outline the expression of miR-940 in various diseases and the molecular biological and cytological functions of target genes in order to reveal its potential diagnostic and prognostic value as well as its predictive value of drug efficacy.

Targeting Nestin+ hepatic stellate cells ameliorates liver fibrosis by facilitating TβRI degradation

BACKGROUND & AIMS

Liver fibrosis is a wound healing response that arises from various aetiologies. The intermediate filament protein Nestin has been reported to participate in maintaining tissue homeostasis during wound healing responses. However, little is known about the role Nestin plays in liver fibrosis. This study investigated the function and precise regulatory network of Nestin during liver fibrosis.

METHODS

Nestin expression was assessed via immunostaining and quantitative real-time PCR (qPCR) in fibrotic/cirrhotic samples. The induction of Nestin expression by transforming growth factor beta (TGFβ)-Smad2/3 signalling was investigated through luciferase reporter assays. The functional role of Nestin in hepatic stellate cells (HSCs) was investigated by examining the pathway activity of profibrogenic TGFβ-Smad2/3 signalling and degradation of TGFβ receptor I (TβRI) after interfering with Nestin. The in vivo effects of knocking down Nestin were examined with an adeno-associated virus vector (serotype 6, AAV6) carrying short-hairpin RNA targeting Nestin in fibrotic mouse models.

RESULTS

Nestin was mainly expressed in activated HSCs and increased with the progression of liver fibrosis. The profibrogenic pathway TGFβ-Smad2/3 induced Nestin expression directly. Knocking down Nestin promoted caveolin 1-mediated TβRI degradation, resulting in TGFβ-Smad2/3 pathway impairment and reduced fibrosis marker expression in HSCs. In AAV6-treated murine fibrotic models, knocking down Nestin resulted in decreased levels of inflammatory infiltration, hepatocellular damage, and a reduced degree of fibrosis.

CONCLUSION

The expression of Nestin in HSCs was induced by TGFβ and positively correlated with the degree of liver fibrosis. Knockdown of Nestin decreased activation of the TGFβ pathway and alleviated liver fibrosis both in vitro and in vivo. Our data demonstrate a novel role of Nestin in controlling HSC activation in liver fibrosis.

LAY SUMMARY

Liver fibrosis has various aetiologies but represents a common process in chronic liver diseases that is associated with high morbidity and mortality. Herein, we demonstrate that the intermediate filament protein Nestin plays an essential profibrogenic role in liver fibrosis by forming a positive feedback loop with the TGFβ-Smad2/3 pathway, providing a potential therapeutic target for the treatment of liver fibrosis.

Lamin A/C: Function in Normal and Tumor Cells

Simple Summary

The aim of this review is to summarize lamin A/C’s currently known functions in both normal and diseased cells. Lamin A/C is a nuclear protein with many functions in cells, such as maintaining a cell’s structural stability, cell motility, mechanosensing, chromosome organization, gene regulation, cell differentiation, DNA damage repair, and telomere protection. Mutations of the lamin A/C gene, incorrect processing of the protein, and lamin A/C deregulation can lead to various diseases and cancer. This review touches on diseases caused by mutation and incorrect processing of lamin A/C, called laminopathies. The effect of lamin A/C deregulation in cancer is also reviewed, and lamin A/C’s potential in helping to diagnose prostate cancers more accurately is discussed.

Abstract

This review is focused on lamin A/C, a nuclear protein with multiple functions in normal and diseased cells. Its functions, as known to date, are summarized. This summary includes its role in maintaining a cell’s structural stability, cell motility, mechanosensing, chromosome organization, gene regulation, cell differentiation, DNA damage repair, and telomere protection. As lamin A/C has a variety of critical roles within the cell, mutations of the lamin A/C gene and incorrect processing of the protein results in a wide variety of diseases, ranging from striated muscle disorders to accelerated aging diseases. These diseases, collectively termed laminopathies, are also touched upon. Finally, we review the existing evidence of lamin A/C’s deregulation in cancer. Lamin A/C deregulation leads to various traits, including genomic instability and increased tolerance to mechanical insult, which can lead to more aggressive cancer and poorer prognosis. As lamin A/C’s expression in specific cancers varies widely, currently known lamin A/C expression in various cancers is reviewed. Additionally, Lamin A/C’s potential as a biomarker in various cancers and as an aid in more accurately diagnosing intermediate Gleason score prostate cancers is also discussed.

Keratin 17 regulates nuclear morphology and chromatin organization

Keratin 17 (KRT17; K17), a non-lamin intermediate filament protein, was recently found to occur in the nucleus. We report here on K17-dependent differences in nuclear morphology, chromatin organization, and cell proliferation. Human tumor keratinocyte cell lines lacking K17 exhibit flatter nuclei relative to normal. Re-expression of wild-type K17, but not a mutant form lacking an intact nuclear localization signal (NLS), rescues nuclear morphology in KRT17-null cells. Analyses of primary cultures of skin keratinocytes from a mouse strain expressing K17 with a mutated NLS corroborated these findings. Proteomics screens identified K17-interacting nuclear proteins with known roles in gene expression, chromatin organization and RNA processing. Key histone modifications and LAP2β (an isoform encoded by TMPO) localization within the nucleus are altered in the absence of K17, correlating with decreased cell proliferation and suppression of GLI1 target genes. Nuclear K17 thus impacts nuclear morphology with an associated impact on chromatin organization, gene expression, and proliferation in epithelial cells.This article has an associated First Person interview with the first author of the paper.

Conversion of Neural Stem Cells into Functional Neuron-Like Cells by MicroRNA-218: Differential Expression of Functionality Genes

Conversion of mesenchymal stem cells (MSC) into neuron-like cells (NLC) is a feasible cell therapy strategy for replacing lost neurons in neuronal disorders. In this study, adipose-derived MSC (ADMSC) were converted into neural stem cells (NSC) via neurosphere. The resulting NSC were then differentiated into NLC by transduction with microRNA-218, using a lentiviral vector. ADMSC, NSC, and NLC were first characterized by flow cytometry, RT-PCR, and immunocytochemistry. The functionality of the NLC was evaluated by qRT-PCR and patch clamp recording. Immunophenotyping of ADMSC showed their immunoreactivity to MSC markers CD90, CD73, CD105, and CD49d, but not to CD31 and CD45. RT-PCR results demonstrated the expression of nestin, neurogenin, neurod1, neurofilament light, and GAP43 genes in NSC while NLC expressed synaptophysin, neurofilament heavy, and GAP43. In addition, NSC morphology changed into multipolar with long processes after transduction with miR-218. Moreover, using qRT-PCR, the expression levels of miR-218 and functionality genes CACNA1C, SNAP25, KCNH1, KCNMA1, and SCN9A were significantly increased in NLC, compared with NSC, and ADMSC at 3 weeks and 5 months post-transduction. Furthermore, the generated NLC expressed significantly higher protein levels of neurofilament heavy polypeptide (NFh) and enolase 2 (Eno2) neuronal markers, compared with ADMSC and NSC. Finally, action potentials were successfully recorded by the generated NLC, using patch clamp. In summary, ADMSC-derived NSC differentiated into functional NLC by transduction with miR-218. The generated NLC expressed functional SNAP25, CACNA1C, KCNH1, KCNMA1, and SCN9A and produced an action potential, which provides useful insights into the generation of functional neuronal cells.

Nestin Selectively Facilitates the Phosphorylation of the Lissencephaly-Linked Protein Doublecortin (DCX) by cdk5/p35 to Regulate Growth Cone Morphology and Sema3a Sensitivity in Developing Neurons

Nestin, an intermediate filament protein widely used as a marker of neural progenitors, was recently found to be expressed transiently in developing cortical neurons in culture and in developing mouse cortex. In young cortical cultures, nestin regulates axonal growth cone morphology. In addition, nestin, which is known to bind the neuronal cdk5/p35 kinase, affects responses to axon guidance cues upstream of cdk5, specifically, to Sema3a. Changes in growth cone morphology require rearrangements of cytoskeletal networks, and changes in microtubules and actin filaments are well studied. In contrast, the roles of intermediate filament proteins in this process are poorly understood, even in cultured neurons. Here, we investigate the molecular mechanism by which nestin affects growth cone morphology and Sema3a sensitivity. We find that nestin selectively facilitates the phosphorylation of the lissencephaly-linked protein doublecortin (DCX) by cdk5/p35, but the phosphorylation of other cdk5 substrates is not affected by nestin. We uncover that this substrate selectivity is based on the ability of nestin to interact with DCX, but not with other cdk5 substrates. Nestin thus creates a selective scaffold for DCX with activated cdk5/p35. Last, we use cortical cultures derived from Dcx KO mice to show that the effects of nestin on growth cone morphology and on Sema3a sensitivity are DCX-dependent, thus suggesting a functional role for the DCX-nestin complex in neurons. We propose that nestin changes growth cone behavior by regulating the intracellular kinase signaling environment in developing neurons. The sex of animal subjects is unknown.SIGNIFICANCE STATEMENT Nestin, an intermediate filament protein highly expressed in neural progenitors, was recently identified in developing neurons where it regulates growth cone morphology and responsiveness to the guidance cue Sema3a. Changes in growth cone morphology require rearrangements of cytoskeletal networks, but the roles of intermediate filaments in this process are poorly understood. We now report that nestin selectively facilitates phosphorylation of the lissencephaly-linked doublecortin (DCX) by cdk5/p35, but the phosphorylation of other cdk5 substrates is not affected. This substrate selectivity is based on preferential scaffolding of DCX, cdk5, and p35 by nestin. Additionally, we demonstrate a functional role for the DCX-nestin complex in neurons. We propose that nestin changes growth cone behavior by regulating intracellular kinase signaling in developing neurons.

Intermediate filaments in developing neurons: Beyond structure

Neuronal development relies on a highly choreographed progression of dynamic cellular processes by which newborn neurons migrate, extend axons and dendrites, innervate their targets, and make functional synapses. Many of these dynamic processes require coordinated changes in morphology, powered by the cell's cytoskeleton. Intermediate filaments (IFs) are the third major cytoskeletal elements in vertebrate cells, but are rarely considered when it comes to understanding axon and dendrite growth, pathfinding and synapse formation. In this review, we first introduce the many new and exciting concepts of IF function, discovered mostly in non-neuronal cells. These roles include dynamic rearrangements, crosstalk with microtubules and actin filaments, mechano-sensing and -transduction, and regulation of signaling cascades. We then discuss the understudied roles of neuronally expressed IFs, with a particular focus on IFs expressed during development, such as nestin, vimentin and α-internexin. Lastly, we illustrate how signaling modulation by the unconventional IF nestin shapes neuronal morphogenesis in unexpected and novel ways. Even though the first IF knockout mice were made over 20 years ago, the study of the cell biological functions of IFs in the brain still has much room for exciting new discoveries.

Tissue-type plasminogen activator-primed human iPSC-derived neural progenitor cells promote motor recovery after severe spinal cord injury

The goal of stem cell therapy for spinal cord injury (SCI) is to restore motor function without exacerbating pain. Induced pluripotent stem cells (iPSC) may be administered by autologous transplantation, avoiding immunologic challenges. Identifying strategies to optimize iPSC-derived neural progenitor cells (hiNPC) for cell transplantation is an important objective. Herein, we report a method that takes advantage of the growth factor-like and anti-inflammatory activities of the fibrinolysis protease, tissue plasminogen activator tPA, without effects on hemostasis. We demonstrate that conditioning hiNPC with enzymatically-inactive tissue-type plasminogen activator (EI-tPA), prior to grafting into a T3 lesion site in a clinically relevant severe SCI model, significantly improves motor outcomes. EI-tPA-primed hiNPC grafted into lesion sites survived, differentiated, acquired markers of motor neuron maturation, and extended βIII-tubulin-positive axons several spinal segments below the lesion. Importantly, only SCI rats that received EI-tPA primed hiNPC demonstrated significantly improved motor function, without exacerbating pain. When hiNPC were treated with EI-tPA in culture, NMDA-R-dependent cell signaling was initiated, expression of genes associated with stemness (Nestin, Sox2) was regulated, and thrombin-induced cell death was prevented. EI-tPA emerges as a novel agent capable of improving the efficacy of stem cell therapy in SCI.

Mechanistic insight of cyclin-dependent kinase 5 in modulating lung cancer growth

Lung harbors the growth of primary and secondary tumors. Even though numerous factors regulate the complex signal transduction and cytoskeletal remodeling toward the progression of lung cancer, cyclin-dependent kinase 5 (Cdk5), a previously known kinase in the central nervous system, has raised much attention in the recent years. Patients with aberrant Cdk5 expression also lead to poor survival. Cdk5 has already been employed in various cellular processes which shape the fate of cancer. In lung cancer, Cdk5 mainly regulates tumor suppressor genes, carcinogenesis, cytoskeletal remodeling, and immune checkpoints. Inhibiting Cdk5 by using drugs, siRNA or CRISP-Cas9 system has rendered crucial therapeutic advantage in the combat against lung cancer. Thus, the relation of Cdk5 to lung cancer needs to be addressed in detail. In this review, we will discuss various cellular events modulated by Cdk5 and we will go further into their underlying mechanism in lung cancer.

Nestin regulates cellular redox homeostasis in lung cancer through the Keap1-Nrf2 feedback loop

Abnormal cancer antioxidant capacity is considered as a potential mechanism of tumor malignancy. Modulation of oxidative stress status is emerging as an anti-cancer treatment. Our previous studies have found that Nestin-knockdown cells were more sensitive to oxidative stress in non-small cell lung cancer (NSCLC). However, the molecular mechanism by which Nestin protects cells from oxidative damage remains unclear. Here, we identify a feedback loop between Nestin and Nrf2 maintaining the redox homeostasis. Mechanistically, the ESGE motif of Nestin interacts with the Kelch domain of Keap1 and competes with Nrf2 for Keap1 binding, leading to Nrf2 escaping from Keap1-mediated degradation, subsequently promoting antioxidant enzyme generation. Interestingly, we also map that the antioxidant response elements (AREs) in the Nestin promoter are responsible for its induction via Nrf2. Taken together, our results indicate that the Nestin-Keap1-Nrf2 axis regulates cellular redox homeostasis and confers oxidative stress resistance in NSCLC.

Leukotriene Synthesis Is Critical for Medulloblastoma Progression

PURPOSE

Here, we examined the role of leukotrienes, well-known inflammatory mediators, in the tumorigenesis of hedgehog pathway-associated medulloblastoma, and tested the efficacies of antagonists of leukotriene biosynthesis in medulloblastoma treatment.Experimental Design: We examined the leukotriene levels in medulloblastoma cells by ELISA. We next tested whether leukotriene synthesis in medulloblastoma cells relied on activation of hedgehog pathway, or the presence of hedgehog ligand secreted by astrocytes. We then investigated whether leukotriene mediated hedgehog-induced Nestin expression in tumor cells. The functions of leukotriene in tumor cell proliferation and tumor growth in medulloblastoma were determined through knocking down 5-lipoxygenase (a critical enzyme for leukotriene synthesis) by shRNAs, or using 5-lipoxygenase-deficient mice. Finally, the efficacies of antagonists of leukotriene synthesis in medulloblastoma treatment were tested in vivo and in vitro.

RESULTS

Leukotriene was significantly upregulated in medulloblastoma cells. Increased leukotriene synthesis relied on hedgehog ligand secreted by astrocytes, a major component of medulloblastoma microenvironment. Leukotriene stimulated tumor cells to express Nestin, a cytoskeletal protein essential for medulloblastoma growth. Genetic blockage of leukotriene synthesis dramatically suppressed medulloblastoma cell proliferation and tumor growth in vivo. Pharmaceutical inhibition of leukotriene synthesis markedly repressed medulloblastoma cell proliferation, but had no effect on proliferation of normal neuronal progenitors. Moreover, antagonists of leukotriene synthesis exhibited promising tumor inhibitory efficacies on drug-resistant medulloblastoma.

CONCLUSIONS

Our findings reveal a novel signaling pathway that is critical for medulloblastoma cell proliferation and tumor progression, and that leukotriene biosynthesis represents a promising therapeutic target for medulloblastoma treatment.

Intermediate Filaments as Effectors of Cancer Development and Metastasis: A Focus on Keratins, Vimentin, and Nestin

Intermediate filament (IF) proteins make up the largest family of cytoskeletal proteins in metazoans, and are traditionally known for their roles in fostering structural integrity in cells and tissues. Remarkably, individual IF genes are tightly regulated in a fashion that reflects the type of tissue, its developmental and differentiation stages, and biological context. In cancer, IF proteins serve as diagnostic markers, as tumor cells partially retain their original signature expression of IF proteins. However, there are also characteristic alterations in IF gene expression and protein regulation. The use of high throughput analytics suggests that tumor-associated alterations in IF gene expression have prognostic value. Parallel research is also showing that IF proteins directly and significantly impact several key cellular properties, including proliferation, death, migration, and invasiveness, with a demonstrated impact on the development, progression, and characteristics of various tumors. In this review, we draw from recent studies focused on three IF proteins most associated with cancer (keratins, vimentin, and nestin) to highlight how several “hallmarks of cancer” described by Hanahan and Weinberg are impacted by IF proteins. The evidence already in hand establishes that IF proteins function beyond their classical roles as markers and serve as effectors of tumorigenesis.

An anti-cancerous protein fraction from Withania somnifera induces ROS-dependent mitochondria-mediated apoptosis in human MDA-MB-231 breast cancer cells

Withania somnifera exhibits different pharmacological activities which mainly stem from its broad range of bioactive molecules. Majority of these bioactive molecules, fall into the groupings of alkaloids, steroidal lactones, phenolic compounds and glycoproteins. In this study, we evaluated a novel protein fraction, named here as WSPF, isolated from Withania somnifera roots for its cytotoxic properties against various human cancer cell lines. WSPF exhibited apoptotic activity for each cancer cell line tested, demonstrating significant activity against MDA-MB-231 human breast cancer cells with an IC₅₀ value of 92 μg/mL. WSPF induced mitochondrial-mediated apoptosis of MDA-MB-231 cells via extensive reactive oxygen species generation, dysregulation of Bax/Bcl-2, loss of mitochondrial membrane potential and caspase-3 activation. Additionally, we observed G2/M-phase cell cycle arrest, cleavage of nuclear lamin A/C proteins, and nuclear morphological changes. The present results highlight the anti-cancer properties of WSPF, indicating that the proteins in this fraction can be potential therapeutic agents for triple negative breast cancer treatment.

Inhibition of FAK Signaling Elicits Lamin A/C-Associated Nuclear Deformity and Cellular Senescence

Focal adhesion kinase (FAK) is a non-receptor kinase that facilitates tumor aggressiveness. The effects of FAK inhibition include arresting proliferation, limiting metastasis, and inhibiting angiogenesis. PF-573228 is an ATP-competitive inhibitor of FAK. Treating lung cancer cells with PF-573228 resulted in FAK inactivation and changes in the expressions of lamin A/C and nuclear deformity. Since lamin A/C downregulation or deficiency was associated with cellular senescence, the senescence-associated β-galactosidase (SA-β-gal) assay was used to investigate whether PF-573228 treatment drove cellular senescence, which showed more SA-β-gal-positive cells in culture. p53 is known to play a pivotal role in mediating the progression of cellular senescence, and the PF-573228-treated lung cancer cells resulted in a higher p53 expression level. Subsequently, the FAK depletion in lung cancer cells was employed to confirm the role of FAK inhibition on cellular senescence. FAK depletion and pharmacological inhibition of lung cancer cells elicited similar patterns of cellular senescence, lamin A/C downregulation, and p53 upregulation, implying that FAK signaling is associated with the expression of p53 and the maintenance of lamin A/C levels to shape regular nuclear morphology and manage anti-senescence. Conversely, FAK inactivation led to p53 upregulation, disorganization of the nuclear matrix, and consequently cellular senescence. Our data suggest a new FAK signaling pathway, in that abolishing FAK signaling can activate the senescence program in cells. Triggering cellular senescence could be a new therapeutic approach to limit tumor growth.

RNase A Promotes Proliferation of Neuronal Progenitor Cells via an ERK-Dependent Pathway

Members of the ribonuclease A (RNase A) superfamily regulate various physiological processes. RNase A, the best-studied member of the RNase A superfamily, is widely expressed in different tissues, including brains. We unexpectedly found that RNase A can trigger proliferation of neuronal progenitor cells (NPC) both in vitro and in vivo. RNase A treatment induced cell proliferation in dissociated neuronal cultures and increased cell mass in neurosphere cultures. BrdU (5-Bromo-2'-Deoxyuridine) labeling confirmed the effect of RNase A on cell proliferation. Those dividing cells were Nestin- and SOX2-positive, suggesting that RNase A triggers NPC proliferation. The proliferation inhibitor Ara-C completely suppressed the effect of RNase A on NPC counts, further supporting that RNase A increases NPC number mainly by promoting proliferation. Moreover, we found that RNase A treatment increased ERK phosphorylation and blockade of the ERK pathway inhibited the effect of RNase A on NPC proliferation. Intracerebroventricular injection of RNase A into mouse brain increased the population of 5-ethynyl-2'-deoxyuridine (EdU) or BrdU-labeled cells in the subventricular zone. Those RNase A-induced NPCs were able to migrate into other brain areas, including hippocampus, amygdala, cortex, striatum, and thalamus. In conclusion, our study shows that RNase A promotes proliferation of NPCs via an ERK-dependent pathway and further diversifies the physiological functions of the RNase A family.