A NSC-34 cell line-derived spheroid model: Potential and challenges for in vitro evaluation of neurodegeneration.

Three-dimensional (3D) spheroid models aim to bridge the gap between traditional two-dimensional (2D) cultures and the complex in vivo tissue environment. These models, created by self-clustering cells to mimic a 3D environment with surrounding extracellular framework, provide a valuable research tool. The NSC-34 cell line, generated by fusing mouse spinal cord motor neurons and neuroblastoma cells, is essential for studying neurodegenerative diseases like amyotrophic lateral sclerosis (ALS), where abnormal protein accumulation, such as TAR-DNA-binding protein 43 (TDP-43), occurs in affected nerve cells. However, NSC-34 behavior in a 3D context remains underexplored, and this study represents the first attempt to create a 3D model to determine its suitability for studying pathology. We generated NSC-34 spheroids using a nonadhesive hydrogel-based template and characterized them for 6 days. Light microscopy revealed that NSC-34 cells in 3D maintained high viability, a distinct round shape, and forming stable membrane connections. Scanning electron microscopy identified multiple tunnel-like structures, while ultrastructural analysis highlighted nuclear bending and mitochondria alterations. Using inducible GFP-TDP-43-expressing NSC-34 spheroids, we explored whether 3D structure affected TDP-43 expression, localization, and aggregation. Spheroids displayed nuclear GFP-TDP-43 expression, albeit at a reduced level compared with 2D cultures and generated both TDP-35 fragments and TDP-43 aggregates. This study sheds light on the distinctive behavior of NSC-34 in 3D culture, suggesting caution in the use of the 3D model for ALS or TDP-43 pathologies. Yet, it underscores the spheroids' potential for investigating fundamental cellular mechanisms, cell adaptation in a 3D context, future bioreactor applications, and drug penetration studies. RESEARCH HIGHLIGHTS: 3D spheroid generation: NSC-34 spheroids, developed using a hydrogel-based template, showed high viability and distinct shapes for 6 days. Structural features: advanced microscopy identified tunnel-like structures and nuclear and mitochondrial changes in the spheroids. Protein dynamics: the study observed how 3D structures impact TDP-43 behavior, with altered expression but similar aggregation patterns to 2D cultures. Research implications: this study reveals the unique behavior of NSC-34 in 3D culture, suggests a careful approach to use this model for ALS or TDP-43 pathologies, and highlights its potential in cellular mechanism research and drug testing applications.

Neratinib is a TFEB and TFE3 activator that potentiates autophagy and unbalances energy metabolism in ERBB2+ breast cancer cells.

Neratinib (NE) is an irreversible pan-ERBB tyrosine kinase inhibitor used to treat breast cancers (BCa) with amplification of the ERBB2/HER2/Neu gene or overexpression of the ERBB2 receptor. However, the mechanisms behind this process are not fully understood. Here we investigated the effects of NE on critical cell survival processes in ERBB2+ cancer cells. By kinome array analysis, we showed that NE time-dependently inhibited the phosphorylation of two distinct sets of kinases. The first set, including ERBB2 downstream signaling kinases such as ERK1/2, ATK, and AKT substrates, showed inhibition after 2 h of NE treatment. The second set, which comprised kinases involved in DNA damage response, displayed inhibition after 72 h. Flow cytometry analyses showed that NE induced G0/G1 cell cycle arrest and early apoptosis. By immunoblot, light and electron microscopy, we revealed that NE also transiently induced autophagy, mediated by increased expression levels and nuclear localization of TFEB and TFE3. Altered TFEB/TFE3 expression was accompanied by dysregulation of mitochondrial energy metabolism and dynamics, leading to a decrease in ATP production, glycolytic activity, and a transient downregulation of fission proteins. Increased TFEB and TFE3 expression was also observed in ERBB2-/ERBB1 + BCa cells, supporting that NE may act through other ERBB family members and/or other kinases. Overall, this study highlights NE as a potent activator of TFEB and TFE3, leading to the suppression of cancer cell survival through autophagy induction, cell cycle arrest, apoptosis, mitochondrial dysfunction and inhibition of DNA damage response.

Lipid Metabolism Reprogramming and Trastuzumab Resistance in Breast Cancer Cell Lines Overexpressing the ERBB2 Membrane Receptor.

Trastuzumab (Tz), an antibody targeting ERBB2, has significantly improved the prognosis for breast cancer (BCa) patients with overexpression of the ERBB2 receptor. However, Tz resistance poses a challenge to patient outcomes. Numerous mechanisms have been suggested to contribute to Tz resistance, and this study aimed to uncover shared mechanisms in in vitro models of acquired BCa Tz resistance. Three widely used ERBB2+ BCa cell lines, adapted to grow in Tz, were examined. Despite investigating potential changes in phenotype, proliferation, and ERBB2 membrane expression in these Tz-resistant (Tz-R) cell lines compared to wild-type (wt) cells, no common alterations were discovered. Instead, high-resolution mass spectrometry analysis revealed a shared set of differentially expressed proteins (DEPs) in Tz-R versus wt cells. Bioinformatic analysis demonstrated that all three Tz-R cell models exhibited modulation of proteins associated with lipid metabolism, organophosphate biosynthesis, and macromolecule methylation. Ultrastructural examination corroborated the presence of altered lipid droplets in resistant cells. These findings strongly support the notion that intricate metabolic adaptations, including lipid metabolism, protein phosphorylation, and potentially chromatin remodeling, may contribute to Tz resistance. The detection of 10 common DEPs across all three Tz-resistant cell lines offers promising avenues for future therapeutic interventions, providing potential targets to overcome Tz resistance and potentially improve patient outcomes in ERBB2+ breast cancer.

Responses of Mytilus galloprovincialis to challenge with environmental isolates of the potential emerging pathogen Malaciobacter marinus.

Bacteria of the Arcobacter-like spp. represent emerging foodborne zoonotic pathogens in humans and animals. Their increasing presence in seafood, suggesting higher occurrence in seawater due to marine pollution, is raising some environmental concern. Although Arcobacter is frequently detected in diseased oysters and stressed bivalve species, no data are available so far on its potential pathogenicity or interactions with the immune system of the bivalve host. In this work, responses to challenge with two strains of Malaciobacter marinus IRTA-19-131 and IRTA-19-132, R1 and R2), isolated from adult Crassostrea gigas during a mortality event in 2019 in Spain, were investigated in the mussel Mytilus galloprovincialis. In vivo experiments were performed in larvae (48 h post-fertilization), and in adult mussels at 24 h post-injection, in order to evaluate the pathogenicity for early developmental stages, and the hemolymph immune responses, respectively. Both R1 and R2 were moderately pathogenic to early larvae, with significant decreases in the development of normal D-veligers from 104 and 103 CFU/mL, respectively. In adults, both strains decreased hemocyte lysosomal membrane stability (LMS), and stimulated extracellular defense responses (ROS production and lysozyme activity). The interactions between mussel hemocytes and M. marinus were investigated in in vitro short-term experiments (30-90 min) using the R1 strain (106-108 CFU/mL). R1 decreased LMS and induced lysosomal enlargement, but not cell detachment or death, and stimulated extracellular ROS production and lysozyme release, confirming in vivo data. Moreover, lysosomal internalization and degradation of bacteria were observed, together with changes in levels of activated mTor and LC3, indicating phagocytic activity. Overall, the results indicate the activation of both extracellular and intracellular immune defenses against M. marinus R1. Accordingly, these responses resulted in a significant hemolymph bactericidal activity, with a large contribution of hemolymph serum. The results represent the first data on the potential pathogenicity of Arcobacter isolated from a shellfish mortality to bivalve larvae and adults, and on their interactions with the immune system of the host.

The Role of Endoplasmic Reticulum in the Differential Endurance against Redox Stress in Cortical and Spinal Astrocytes from the Newborn SOD1G93A Mouse Model of Amyotrophic Lateral Sclerosis.

Recent studies reported that the uptake of [18F]-fluorodeoxyglucose (FDG) is increased in the spinal cord (SC) and decreased in the motor cortex (MC) of patients with ALS, suggesting that the disease might differently affect the two nervous districts with different time sequence or with different mechanisms. Here we show that MC and SC astrocytes harvested from newborn B6SJL-Tg (SOD1G93A) 1Gur mice could play different roles in the pathogenesis of the disease. Spectrophotometric and cytofluorimetric analyses showed an increase in redox stress, a decrease in antioxidant capacity and a relative mitochondria respiratory uncoupling in MC SOD1G93A astrocytes. By contrast, SC mutated cells showed a higher endurance against oxidative damage, through the increase in antioxidant defense, and a preserved respiratory function. FDG uptake reproduced the metabolic response observed in ALS patients: SOD1G93A mutation caused a selective enhancement in tracer retention only in mutated SC astrocytes, matching the activity of the reticular pentose phosphate pathway and, thus, of hexose-6P dehydrogenase. Finally, both MC and SC mutated astrocytes were characterized by an impressive ultrastructural enlargement of the endoplasmic reticulum (ER) and impairment in ER-mitochondria networking, more evident in mutated MC than in SC cells. Thus, SOD1G93A mutation differently impaired MC and SC astrocyte biology in a very early stage of life.

Imaging of Endocytic Trafficking and Extracellular Vesicles Released Under Neratinib Treatment in ERBB2+ Breast Cancer Cells.

Breast cancers (BCa) with ERBB2 amplification show rapid tumor growth, increased disease progression, and lower survival rate. Deregulated intracellular trafficking and extracellular vesicle (EVs) release are mechanisms that support cancer progression and resistance to treatments. Neratinib (NE) is a Food and Drug Administration-approved pan-ERBB inhibitor employed for the treatment of ERBB2+ BCa that blocks signaling and causes survival inhibition. However, the effects of NE on ERBB2 internalization, its trafficking to multivesicular bodies (MVBs), and the release of EVs that originate from these organelles remain poorly studied. By confocal and electron microscopy, we observed that low nanomolar doses of NE induced a modest ERBB2 internalization along with an increase of clathrin-mediated endocytosis and of the CD63+ MVB compartment in SKBR-3 cells. Furthermore, we showed in the culture supernatant two distinct EV subsets, based on their size and ERBB2 positivity: small (30-100 nm) ERBB2- EVs and large (>100 nm) ERBB2+ EVs. In particular, we found that NE increased the overall release of EVs, which displayed a reduced ERBB2 positivity compared with controls. Taken together, these results provide novel insight into the effects of NE on ERBB2+ BCa cells that may lead to a reduction of ERBB2 potentially transferred to distant target cells by EVs.

Trastuzumab Modulates the Protein Cargo of Extracellular Vesicles Released by ERBB2+ Breast Cancer Cells.

Cancers overexpressing the ERBB2 oncogene are aggressive and associated with a poor prognosis. Trastuzumab is an ERBB2 specific recombinant antibody employed for the treatment of these diseases since it blocks ERBB2 signaling causing growth arrest and survival inhibition. While the effects of Trastuzumab on ERBB2 cancer cells are well known, those on the extracellular vesicles (EVs) released from these cells are scarce. This study focused on ERBB2+ breast cancer cells and aimed to establish what type of EVs they release and whether Trastuzumab affects their morphology and molecular composition. To these aims, we performed immunoelectron microscopy, immunoblot, and high-resolution mass spectrometry analyses on EVs purified by differential centrifugation of culture supernatant. Here, we show that EVs released from ERBB2+ breast cancer cells are polymorphic in size and appearance and that ERBB2 is preferentially associated with large (120 nm) EVs. Moreover, we report that Trastuzumab (Tz) induces the expression of a specific glycosylated 50 kDa isoform of the CD63 tetraspanin and modulates the expression of 51 EVs proteins, including TOP1. Because these proteins are functionally associated with organelle organization, cytokinesis, and response to lipids, we suggest that Tz may influence these cellular processes in target cells at distant sites via modified EVs.

The chromodomain helicase CHD4 regulates ERBB2 signaling pathway and autophagy in ERBB2+ breast cancer cells.

The chromodomain helicase DNA-binding 4 (CHD4), a member of the nucleosome remodeling and deacetylases (NuRD) complex, has been identified as an oncogene that modulates proliferation and migration of breast cancers (BC). ERBB2 is an oncogenic driver in 20-30% of BC in which its overexpression leads to increased chemoresistance. Here we investigated whether CHD4 depletion affects the ERBB2 cascade and autophagy, which represents a mechanism of resistance against Trastuzumab (Tz), a therapeutic anti-ERBB2 antibody. We show that CHD4 depletion in two ERBB2+ BC cell lines strongly inhibits cell proliferation, induces p27KIP1 upregulation, Tyr1248 ERBB2 phosphorylation, ERK1/2 and AKT dephosphorylation, and downregulation of both ERBB2 and PI3K levels. Moreover, CHD4 silencing impairs late stages of autophagy, resulting in increased levels of LC3 II and SQSTM1/p62, lysosomal enlargement and accumulation of autolysosomes (ALs). Importantly, we show that CHD4 depletion and concomitant treatment with Tz prevent cell proliferation in vitro Our results suggest that CHD4 plays a critical role in modulating cell proliferation, ERBB2 signaling cascade and autophagy and provide new insights on CHD4 as a potential target for the treatment of ERBB2+ BC.

Autophagic processes in Mytilus galloprovincialis hemocytes: Effects of Vibrio tapetis.

Autophagy is a highly conserved and regulated catabolic process involved in maintaining cell homeostasis in response to different stressors. The autophagic machinery is also used as an innate immune mechanism against microbial infection. In invertebrates, that lack acquired immunity, autophagy may thus play a key role in the protection against potential pathogens. In aquatic molluscs, evidence has been provided for induction of autophagy by starvation and different environmental stressors; however, no information is available on autophagic pathways in the immune cells, the hemocytes. In this work, the autophagic processes were investigated in the hemocytes of the marine bivalve, the mussel Mytilus galloprovincialis. The effects of classical inducers/inhibitors of mammalian autophagy were first tested. Rapamycin induced a decrease in lysosomal membrane stability-LMS that was prevented by the autophagy inhibitor Wortmannin. Increased MDC fluorescence and expression of LC3-II were also observed. Moreover, responses to in vitro challenge with the bivalve pathogen Vibrio tapetis were evaluated. Mussel hemocytes were unable to activate the immune response towards V. tapetis; however, bacterial challenge induced a moderate decrease in LMS, corresponding to lysosomal activation but no cytotoxicity; the effect was prevented by Wortmannin. TEM observations showed that V. tapetis resulted in rapid formation of autophagosomes and autolysosomes. Accordingly, increased LC3-II expression, decreased levels of phosphorylated mTor and of p62 were observed. The results represent the first evidence for autophagic processes in bivalve hemocytes in response to bacterial challenge, and underline the protective role of autophagy towards potential pathogenic vibrios.

Cooperative antitumor activities of carnosic acid and Trastuzumab in ERBB2+ breast cancer cells.

BACKGROUND: ERBB2 is overexpressed in up to 20-30% of human breast cancers (BCs), and it is associated with aggressive disease. Trastuzumab (Tz), a humanized monoclonal antibody, improves the prognosis associated with ERBB2-amplified BCs. However, the development of resistance remains a significant challenge. Carnosic acid (CA) is a diterpene found in rosemary and sage, endowed with anticancer properties. In this in vitro study, we have investigated whether Tz and CA have cooperative effects on cell survival of ERBB2 overexpressing (ERBB2+) cells and whether CA might restore Tz sensitivity in Tz-resistant cells. METHODS: We have studied BC cell migration and survival upon CA and Tz treatment. In particular, migration ability was assessed by transwell assay while cell survival was assessed by MTT assay. In addition, we have performed cell cycle and apoptosis analysis by high-resolution DNA flow cytometry and annexin-V, resazurin and sytox blue staining by flow cytometry, respectively. The expression of proteins involved in cell cycle progression, ERBB2 signaling pathway, and autophagy was evaluated by immunoblot and immunofluorescence analysis. Cellular structures relevant to the endosome/lysosome and autophagy pathways have been studied by immunofluorescence and transmission electron microscopy. RESULTS: We report that, in ERBB2+ BC cells, CA reversibly enhances Tz inhibition of cell survival, cooperatively inhibits cell migration and induces cell cycle arrest in G0/G1. These events are accompanied by ERBB2 down-regulation, deregulation of the PI3K/AKT/mTOR signaling pathway and up-regulation of both CDKN1A/p21WAF1 and CDKN1B/p27KIP1. Furthermore, we have demonstrated that CA impairs late autophagy and causes derangement of the lysosomal compartment as shown by up-regulation of SQSTM1/p62 and ultrastructural analysis. Accordingly, we have found that CA restores, at least in part, sensitivity to Tz in SKBR-3 Tz-resistant cell line. CONCLUSIONS: Our data demonstrate the cooperation between CA and Tz in inhibiting cell migration and survival of ERBB2+ BC cells that warrant further studies to establish if CA or CA derivatives may be useful in vivo in the treatment of ERBB2+ cancers.

Cooperative but distinct early co-signaling events originate from ERBB2 and ERBB1 receptors upon trastuzumab treatment in breast cancer cells.

ERBB2 receptor belongs to the ERBB tyrosine kinase receptor family. At variance to the other family members, ERBB2 is a constitutively active orphan receptor. Upon ligand binding and activation, ERBB receptors form homo- or hetero-dimers with the other family members, including ERBB2, promoting an intracellular signaling cascade. ERBB2 is the preferred dimerization partner and ERBB2 heterodimers signaling is stronger and longer acting compared to heterodimers between other ERBB members. The specific contribution of ERBB2 in heterodimer signaling is still undefined. Here we report the formation of circular dorsal ruffles (CDRs) upon treatment of the ERBB2-overexpressing breast cancer cell lines SK-BR-3 and ZR751 with Trastuzumab, a therapeutic humanized monoclonal antibody directed against ERBB2. We found that in SK-BR-3 cells Trastuzumab leads to surface redistribution of ERBB2 and ERBB1 in CDRs, and that the ERBB2-dependent ERK1/2 phosphorylation and ERBB1 expression are both required for CDR formation. In particular, in these cells CDR formation requires activation of both the protein regulator of actin polymerization N-WASP, mediated by ERK1/2, and of the actin depolymerizing protein cofilin, mediated by ERBB1. Furthermore, we suggest that this latter event may be inhibited by the negative cell motility regulator p140Cap, as we found that p140Cap overexpression led to cofilin deactivation and inhibition of CDR formation. In conclusion, here we show for the first time an ERBB2-specific signaling contribution to an ERBB2/ERBB1 heterodimer, in the activation of a complex biological process such as the formation of CDRs.

Identification of an HSP90 modulated multi-step process for ERBB2 degradation in breast cancer cells.

The receptor tyrosine kinase ERBB2 interacts with HSP90 and is overexpressed in aggressive breast cancers. Therapeutic HSP90 inhibitors, i.e. Geldanamycin (GA), target ERBB2 to degradation. We have previously shown that HSP90 is responsible for the missorting of recycling ERBB2 to degradation compartments. In this study, we used biochemical, immunofluorescence and electron microscopy techniques to demonstrate that in SKBR3 human breast cancer cells, GA strongly induces polyubiquitination and internalization of the full-length p185-ERBB2, and promotes its cleavage, with the formation of a p116-ERBB2 form in EEA1-positive endosomes (EE). p116-ERBB2 corresponds to a non-ubiquitinated, signaling-impaired, membrane-bound fragment, which is readily sorted to lysosomes and degraded. To define the sequence of events leading to p116-ERBB2 degradation, we first blocked the EE maturation/trafficking to late endosomes/lysosomes with wortmannin, and found an increase in GA-dependent formation of p116-ERBB2; we then inhibited the proteasome activity with MG-132 or lactacystin, and observed an efficient block of p185-ERBB2 cleavage, and its accumulation in EE, suggesting that p185-ERBB2 polyubiquitination is necessary for proteasome-dependent p116-ERBB2 generation occurring in EE. As polyubiquitination has also been implicated in autophagy-mediated degradation of ERBB2 under different experimental conditions, we exploited this possibility and demonstrate that GA strongly inhibits early autophagy, and reduces the levels of the autophagy markers atg5-12 and LC3-II, irrespective of GA-induced ERBB2 polyubiquitination, ruling out a GA-dependent autophagic degradation of ERBB2. In conclusion, we propose that HSP90 inhibition fosters ERBB2 polyubiquitination and proteasome-dependent generation of a non-ubiquitinated and inactive p116-ERBB2 form in EE, which is trafficked from altered EE to lysosomes.

Carnosic acid induces proteasomal degradation of Cyclin B1, RB and SOX2 along with cell growth arrest and apoptosis in GBM cells.

BACKGROUND: Carnosic acid (CA) is a diterpenoid found in Rosmarinus officinalis L. and Salvia officinalis L. as well as in many other Lamiaceae. This compound is reported to have antioxidant and antimicrobial properties. In addition, a number of reports showed that CA has a cytotoxic activity toward several cancer cell lines. PURPOSE: The aim of this study was to establish whether CA has any specific antiproliferative effect toward human glioblastoma (GBM) cells and to analyze the molecular mechanisms involved. METHODS: We evaluated cell survival by MTT assay, apoptosis and DNA content by flow cytometry, protein expression and phosphorylation by immunoblot analyses. RESULTS: Our results showed that CA inhibited cell survival on both normal astrocytes and GBM cells. In GBM cells, in particular, CA caused an early G2 block, a reduction in the percentage of cells expressing Ki67, an enhanced expression of p21(WAF) and induced apoptosis. Furthermore, we showed that CA promoted proteasomal degradation of several substrate proteins, including Cyclin B1, retinoblastoma (RB), SOX2, and glial fibrillary acid protein (GFAP), whereas MYC levels were not modified. In addition, CA dramatically reduced the activity of CDKs. CONCLUSION: In conclusion, our findings strongly suggest that CA promotes a profound deregulation of cell cycle control and reduces the survival of GBM cells via proteasome-mediated degradation of Cyclin B1, RB and SOX2.

TTF-1/NKX2.1 up-regulates the in vivo transcription of nestin.

TTF-1/NKX2.1, also known as T/EBP, is a homeodomain-containing gene involved in the organogenesis of the thyroid gland, lung and ventral forebrain. We have already reported that in 3T3 cells, TTF-1/NKX2.1 up-regulates the transcription of nestin, an intermediate filament protein expressed in multipotent neuroepithelial cells, by direct DNA-binding to a HRE/CRE-like site (NestBS) within a CNS-specific enhancer. Here, we demonstrate that TTF-1/NKX2.1 is co-expressed with nestin in the embryonal forebrain. We also performed a transgenic mouse embryo analysis in which NestBS was replaced by the canonical TTF-1/NKX2.1 consensus DNA-binding site (as identified in many thyroid- and lung-specific genes and very divergent from NestBS) or a random mutation. We observed beta-galactosidase expression in forebrain regions where TTF-1/NKX2.1 is expressed in wild-type embryos, and -to a minor extent- in rostralmost telencephalic regions and thalamus, whereas no beta-galactosidase expression was detected in forebrains of embryos bearing the random mutation. These data show that TTF-1/NKX2.1 regulates the transcription of the nestin gene in vivo through the NestBS site, suggesting that nestin might be at least one of the effectors of TTF-1/NKX2.1 during forebrain development. Finally, we have shown that the transactivating effect of TTF-1/NKX2.1 on the CNS-specific enhancer is unaffected by Retinoic Acid Receptor-alpha.