Lamin A/C Mechanosensor Drives Tumor Cell Aggressiveness and Adhesion on Substrates With Tissue-Specific Elasticity

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.

Nuclear deformability facilitates apical nuclear migration in the developing zebrafish retina

Nuclear positioning is a crucial aspect of cell and developmental biology. One example is the apical movement of nuclei in neuroepithelia before mitosis, which is essential for proper tissue formation. While the cytoskeletal mechanisms that drive nuclei to the apical side have been explored, the influence of nuclear properties on apical nuclear migration is less understood. Nuclear properties, such as deformability, can be linked to lamin A/C expression levels, as shown in various in vitro studies. Interestingly, many nuclei in early development, including neuroepithelial nuclei, express only low levels of lamin A/C. Therefore, we investigated whether increased lamin A expression in the densely packed zebrafish retinal neuroepithelium affects nuclear deformability and, consequently, migration phenomena. We found that overexpressing lamin A in retinal nuclei increases nuclear stiffness, which in turn indeed impairs apical nuclear migration. Interestingly, nuclei that do not overexpress lamin A but are embedded in a stiffer lamin A-overexpressing environment also exhibit impaired apical nuclear migration, indicating that these effects can be cell non-autonomous. Additionally, in the less crowded hindbrain neuroepithelium, only minor effects on apical nuclear migration are observed. Together, this suggests that the material properties of the nucleus influence nuclear movements in a tissue-dependent manner.

Role of lamins in cellular physiology and cancer

Lamins, which are crucial type V intermediate filament proteins found in the nuclear lamina, are essential for maintaining the stability and function of the nucleus in higher vertebrates. They are classified into A- and B-types, and their distinct expression patterns contribute to cellular survival, development, and functionality. Lamins emerged during the transition from open to closed mitosis, with their complexity increasing alongside organism evolution. Derived from the LMNA, LMNB1, and LMNB2 genes, lamins undergo alternative splicing to produce seven variants, influencing cellular processes such as stiffness, chromatin condensation, and cell cycle regulation. The lamin network interacts with the cytoskeleton via Linkers of the nucleoskeleton to the cytoskeleton (LINC) complexes, playing a critical role in cellular stability and mechanotransduction. Lamins also regulate active transport into and out of the nucleus, affecting nuclear integrity, positioning, DNA maintenance, and gene expression. Genetic mutations in lamin genes lead to laminopathies, highlighting their functional significance and organizational roles. Changes in lamin subtype composition within the nuclear lamina have significant implications for cancer development, impacting cellular stiffness, mobility, and the Epithelial-to-Mesenchymal Transition (EMT). Lamin A/C, in particular, plays multifaceted roles in cancer biology, influencing progression, metastasis, and therapy response through interactions with various proteins and pathways. Dysregulated lamin expression is commonly observed in cancers, suggesting their potential as diagnostic and prognostic markers. This chapter underscores the pivotal roles of lamins in nuclear architecture and cancer biology, emphasizing their impact on cellular functions and disease pathology. Understanding lamin behavior and regulation mechanisms holds promise for developing novel diagnostic tools and targeted therapies in cancer treatment.

Development of an Optical System for Strain Drop Measurement of Osteosarcoma Cells on Substrates with Different Stiffness

Adherent cells perceive mechanical feedback from the underlying matrix and convert it into biochemical signals through a process known as mechanotransduction. The response to changes in the microenvironment relies on the cell's mechanical properties, including elasticity, which was recently identified as a biomarker for various diseases. Here, we propose the design, development, and characterization of a new system for the measurement of adherent cells' strain drop, a parameter correlated with cells' elasticity. To consider the interplay between adherent cells and the host extracellular matrix, cell stretching was combined with adhesion on substrates with different stiffnesses. The technique is based on the linear stretching of silicone chambers, high-speed image acquisition, and feedback for image centering. The system was characterized in terms of the strain homogeneity, impact of collagen coating, centering capability, and sensitivity. Subsequently, it was employed to measure the strain drop of two osteosarcoma cell lines, low-aggressive osteoblast-like SaOS-2 and high-aggressive 143B, cultured on two different substrates to recall the stiffness of the bone and lung extracellular matrices. Results demonstrated good substrate homogeneity, a negligible effect of the collagen coating, and an accurate image centering. Finally, the experimental results showed an average strain drop that was lower in the 143B cells in comparison with the SaOS-2 cells in all the tested conditions.

The effect of cellular nuclear function alteration on the pathogenesis of shoulder adhesive capsulitis: an immunohistochemical study on lamin A/C expression

BACKGROUND

The network of intermediate filament proteins underlying the inner nuclear membrane forms the nuclear lamina. Lamins have been associated with important cellular functions: DNA replication, chromatin organization, differentiation of the cell, apoptosis and in maintenance of nuclear structure. Little is known regarding the etiopathogenesis of adhesive capsulitis (AC); recently, a dysregulating fibrotic response starting from a subpopulation has been described within the fibroblast compartment, which suddenly turns on an activated phenotype. Considering the key role of A-type lamins in the regulation of cellular stability and function, our aim was to compare the lamin A/C expression between patients with AC and healthy controls.

MATERIALS AND METHODS

A case-control study was performed between January 2020 and December 2021. Tissue samples excised from the rotator interval were analysed for lamin A/C expression by immunohistochemistry. Patients with AC were arbitrarily distinguished according to the severity of shoulder flexion limitation: ≥ 90° and < 90°. Controls were represented by samples obtained by normal rotator interval excised from patients submitted to shoulder surgery. The intensity of staining was graded, and an H-score was assigned. Statistical analysis was performed (Chi-square analysis; significance was set at alpha = 0.05).

RESULTS

We enrolled 26 patients [12 male and 14 female, mean age (SD): 52.3 (6.08)] and 15 controls [6 male and 9 female, mean age (SD): 57.1 (5.3)]. The expression of lamin A/C was found to be significantly lower in the fibroblasts of patients with adhesive capsulitis when compared with controls (intensity of staining: p: 0.005; H-score: 0.034); no differences were found regarding the synoviocytes (p: > 0.05). Considering only patients with AC, lamin A/C intensity staining was found to be significantly higher in samples where acute inflammatory infiltrate was detected (p: 0.004). No significant changes in levels of lamin A/C expression were documented between the mild and severe adhesive capsulitis severity groups.

CONCLUSIONS

Our study demonstrated that the activity of lamin A/C in maintaining nuclear structural integrity and cell viability is decreased in patients with adhesive capsulitis. The phase of the pathogenetic process (freezing and early frozen) is the key factor for cell functionality. On the contrary, the clinical severity of adhesive capsulitis plays a marginal role in nuclear stability.

LEVEL OF EVIDENCE

III.

Determination of a Measurement Procedure for the Study of Cells' Dielectric Properties through Descriptive Statistic

This paper presents a measurement procedure for analyzing the dielectric properties of cells using descriptive statistics. The study focuses on four cancer cell lines (MDA-MB-231 and MCF-7 breast cancer, SaOS-2, and 143B osteosarcoma) and DMEM culture medium, utilizing the Lorentzian fit model of the return-loss function. The measurements are performed using a circular patch resonator with a 40 mm diameter, powered by a miniVNA operating in the frequency range of 1 MHz to 3 GHz. Eight specimens are prepared for each group to ensure reliability, and the return loss is recorded ten times for each specimen. Various statistical parameters are calculated and evaluated, including the average value, standard deviation, coefficient of variation, and relative error between the average and the first values. The results demonstrate that one single acquisition highly represents the entire set of ten data points, especially for the resonant frequency, with an accuracy error lower than 0.05%. These findings have significant implications for the methodological approach to detecting cells' dielectric properties, as they substantially reduce time and preserve the specimens without compromising the accuracy of the experimental results.

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.

p53 regulates expression of nuclear envelope components in cancer cells

Nuclear organisation and architecture are essential for the maintenance of genomic integrity as well as for the epigenetic regulations and gene expression. Disruption of lamin B1, major structural and functional member of the nuclear lamina, is observed in human laminopathies and in sporadic cancers, and leads to chromosomal rearrangements and alterations of gene expression. The tumour suppressor p53 has been shown to direct specific transcriptional programmes by regulating lamin A/C, however its relationship with lamin B1 has remained elusive. Here, we show that loss of p53 correlates with increased expression of members belonging to the nuclear pore complex and nuclear lamina and directly regulates transcription of lamin B1. We show that the genomic loci of a fraction of p53-dependent genes physically interact with lamin B1 and Nup210. This observation provides a possible mechanistic explanation for the p53-depedent changes of chromatin accessibility, with the consequent influence of expression and rearrangement of these genomic sites in pancreatic cancer. Overall, these data suggest a potential functional and biochemical regulatory network connecting p53 and nuclear architecture.

Mechanobiology of solid tumors

Mechanical features of cancer cells emerge as a distinct trait during development and progression of solid tumors. Herein, we discuss recent key findings regarding the impact of various types of mechanical stresses on cancer cell properties. Data suggest that different mechanical forces, alterations of matrix rigidity and tumor microenvironment facilitate cancer hallmarks, especially invasion and metastasis. Moreover, a subset of mechanosensory proteins are responsible for mediating mechanically induced oncogenic signaling and response to chemotherapy. Delineating cancer dynamics and decoding of respective signal transduction mechanisms will provide new therapeutic strategies against solid tumors in the future.

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.

Intermediate filaments: Integration of cell mechanical properties during migration

Cell migration is a vital and dynamic process required for the development of multicellular organisms and for immune system responses, tissue renewal and wound healing in adults. It also contributes to a variety of human diseases such as cancers, autoimmune diseases, chronic inflammation and fibrosis. The cytoskeleton, which includes actin microfilaments, microtubules, and intermediate filaments (IFs), is responsible for the maintenance of animal cell shape and structural integrity. Each cytoskeletal network contributes its unique properties to dynamic cell behaviour, such as cell polarization, membrane protrusion, cell adhesion and contraction. Hence, cell migration requires the dynamic orchestration of all cytoskeleton components. Among these, IFs have emerged as a molecular scaffold with unique mechanical features and a key player in the cell resilience to mechanical stresses during migration through complex 3D environment. Moreover, accumulating evidence illustrates the participation of IFs in signalling cascades and cytoskeletal crosstalk. Teaming up with actin and microtubules, IFs contribute to the active generation of forces required for cell adhesion and mesenchymal migration and invasion. Here we summarize and discuss how IFs integrate mechanical properties and signalling functions to control cell migration in a wide spectrum of physiological and pathological situations.

The Paradox of Nuclear Lamins in Pathologies: Apparently Controversial Roles Explained by Tissue-Specific Mechanobiology

The nuclear lamina is a complex meshwork of intermediate filaments (lamins) that is located beneath the inner nuclear membrane and the surrounding nucleoplasm. The lamins exert both structural and functional roles in the nucleus and, by interacting with several nuclear proteins, are involved in a wide range of nuclear and cellular activities. Due their pivotal roles in basic cellular processes, lamin gene mutations, or modulations in lamin expression, are often associated with pathological conditions, ranging from rare genetic diseases, such as laminopathies, to cancer. Although a substantial amount of literature describes the effects that are mediated by the deregulation of nuclear lamins, some apparently controversial results have been reported, which may appear to conflict with each other. In this context, we herein provide our explanation of such “controversy”, which, in our opinion, derives from the tissue-specific expression of nuclear lamins and their close correlation with mechanotransduction processes, which could be very different, or even opposite, depending on the specific mechanical conditions that should not be compared (a tissue vs. another tissue, in vivo studies vs. cell cultures on glass/plastic supports, etc.). Moreover, we have stressed the relevance of considering and reproducing the “mechano-environment” in in vitro experimentation. Indeed, when primary cells that are collected from patients or donors are maintained in a culture, the mechanical signals deriving from canonical experimental procedures of cell culturing could alter the lamin expression, thereby profoundly modifying the assessed cell type, in some cases even too much, compared to the cell of origin.

RNA 5-methylcytosine status is associated with DNMT2/TRDMT1 nuclear localization in osteosarcoma cell lines

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Selected phenotypic features of three osteosarcoma (OS) cell lines were evaluated.

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Redox disequilibrium promoted sustained AKT and ERK1/2 activation.

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Redox imbalance modulated cell death pathways in OS cells.

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Nuclear levels of TRDMT1 methyltransferase were associated with RNA methylation.

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A novel marker for predicting therapy response in OS patients is proposed.

Osteosarcoma (OS) is a pediatric malignant bone tumor with unsatisfying improvements in survival rates due to limited understanding of OS biology and potentially druggable targets. The present study aims to better characterize osteosarcoma U-2 OS, SaOS-2, and MG-63 cell lines that are commonly used as in vitro models of OS. We focused on evaluating the differences in cell death pathways, redox equilibrium, the activity of proliferation-related signaling pathways, DNA damage response, telomere maintenance, DNMT2/TRDMT1-based responses and RNA 5-methylcytosine status. SaOS-2 cells were characterized by higher levels of superoxide and nitric oxide that promoted AKT and ERK1/2 activation thus modulating cell death pathways. OS cell lines also differed in the levels and localization of DNA repair regulator DNMT2/TRDMT1. SaOS-2 cells possessed the lowest levels of total, cytoplasmic and nuclear DNMT2/TRDMT1, whereas in MG-63 cells, the highest levels of nuclear DNMT2/TRDMT1 were associated with the most pronounced status of RNA 5-methylcytosine. In silico analysis revealed potential phosphorylation sites at DNMT2/TRDMT1 that may be related to the regulation of DNMT2/TRDMT1 localization. We postulate that redox homeostasis, proliferation-related pathways and DNMT2/TRDMT1-based effects can be modulated as a part of anti-osteosarcoma strategy reflecting diverse phenotypic features of OS cells.

Toll-like receptor 8 agonists improve NK-cell function primarily targeting CD56brightCD16− subset

Background

Toll-like receptors (TLRs) are pattern-recognition sensors mainly expressed in innate immune cells that directly recognize conserved pathogen structures (pathogen-associated molecular patterns-PAMPs). Natural killer (NK) cells have been described to express different endosomal TLRs triggered by RNA and DNA sequences derived from both viruses and bacteria. This study was addressed to establish which endosomal TLR could directly mediate NK activation and function after proper stimuli. It was also important to establish the most suitable TLR agonist to be used as adjuvant in tumor vaccines or in combined cancer immunotherapies.

Methods

We assessed endosomal TLR expression in total NK cells by using RT-qPCR and western blotting technique. In some experiments, we purified CD56^brightCD16⁻ and CD56^dimCD16⁺ cells subsets by using NK Cell Isolation Kit Activation marker, cytokine production, CD107a expression and cytotoxicity assay were evaluated by flow cytometry. Cytokine release was quantified by ELISA. NK cells obtained from ovarian ascites underwent the same analyses.

Results

Although the four endosomal TLRs (TLR3, TLR7/8, and TLR9) were uniformly expressed on CD56^brightCD16⁻ and CD56^dimCD16⁺ cell subsets, the TLR7/8 (R848), TLR3 (polyinosinic-polycytidylic acid, Poly I:C) and TLR9 (ODN2395) ligands promoted NK-cell function only in the presence of suboptimal doses of cytokines, including interleukin (IL)-2, IL-12, IL-15, and IL-18, produced in vivo by other environmental cells. We showed that R848 rather than TLR3 and TLR9 agonists primarily activated CD56^brightCD16⁻ NK cells by increasing their proliferation, cytokine production and cytotoxic activity. Moreover, we demonstrated that R848, which usually triggers TLR7 and TLR8 on dendritic cells, macrophages and neutrophils cells, activated CD56^brightCD16⁻ NK-cell subset only via TLR8. Indeed, specific TLR8 but not TLR7 agonists increased cytokine production and cytotoxic activity of CD56^brightCD16⁻ NK cells. Importantly, these activities were also observed in peritoneal NK cells from patients with metastatic ovarian carcinoma, prevalently belonging to the CD56^brightCD16⁻ subset.

Conclusion

These data highlight the potential value of TLR8 in NK cells as a new target for immunotherapy in patients with cancer.