Nuclear Envelope Integrity in Health and Disease: Consequences on Genome Instability and Inflammation

Sculpting nuclear envelope identity from the endoplasmic reticulum during the cell cycle

The nuclear envelope (NE) regulates nuclear functions, including transcription, nucleocytoplasmic transport, and protein quality control. While the outer membrane of the NE is directly continuous with the endoplasmic reticulum (ER), the NE has an overall distinct protein composition from the ER, which is crucial for its functions. During open mitosis in higher eukaryotes, the NE disassembles during mitotic entry and then reforms as a functional territory at the end of mitosis to reestablish nucleocytoplasmic compartmentalization. In this review, we examine the known mechanisms by which the functional NE reconstitutes from the mitotic ER in the continuous ER-NE endomembrane system during open mitosis. Furthermore, based on recent findings indicating that the NE possesses unique lipid metabolism and quality control mechanisms distinct from those of the ER, we explore the maintenance of NE identity and homeostasis during interphase. We also highlight the potential significance of membrane junctions between the ER and NE.

Nuclear pore dysfunction and disease: a complex opportunity

The separation of genetic material from bulk cytoplasm has enabled the evolution of increasingly complex organisms, allowing for the development of sophisticated forms of life. However, this complexity has created new categories of dysfunction, including those related to the movement of material between cellular compartments. In eukaryotic cells, nucleocytoplasmic trafficking is a fundamental biological process, and cumulative disruptions to nuclear integrity and nucleocytoplasmic transport are detrimental to cell survival. This is particularly true in post-mitotic neurons, where nuclear pore injury and errors to nucleocytoplasmic trafficking are strongly associated with neurodegenerative disease. In this review, we summarize the current understanding of nuclear pore biology in physiological and pathological contexts and discuss potential therapeutic approaches for addressing nuclear pore injury and dysfunctional nucleocytoplasmic transport.

Identification of inflammatory response-related molecular mechanisms based on the ATM/ATR/p53 pathway in tumor cells

Inflammatory response is a crucial factor that affects prognosis and therapeutic effect in tumor cells. Although some studies have shown that inflammation could make DNA more vulnerable to external attacks, resulting in serious DNA damage, the underlying mechanism remains unknown. Then, using tumor necrosis factor α (TNF-α) and lipopolysaccharide (LPS), this research elevated the level of inflammation in cancer cells, and hydrogen peroxide (H2O2) and ultraviolet (UV) were utilized as common reactive oxygen species (ROS)-induced DNA damage agents. We show that either H2O2 or UV achieved a more substantial antiproliferative effect in the inflammation environment compared with H2O2 or UV treatment alone. The inflammation environment enhanced H2O2- or UV-induced cell apoptosis and ROS production. Although the phenomenon that inflammation itself could trigger ROS-dependent DNA damage was well known, the underlying mechanism for the sensitization of inflammation to trigger intense DNA damage via ROS in cancer cells remains unclear. In this study, the inflammation-related genes and the corresponding expression information were obtained from the TCGA and fetched genes associated with inflammatory factors. Screening of thirteen inflammatory-related, including ATM, and prognostic genes. In addition, KEGG analysis of prognostic genes shows that biological processes such as DNA replication. ATM and ATR, which belong to the PI3/PI4-kinase family, can activate p53. Inflammation promotes the vulnerability of DNA by activating the ATM/ATR/p53 pathway, while not affecting the DNA damage repair pathway. In brief, this research suggested that inflammation made DNA vulnerable due to the amplifying H2O2- or UV-induced ROS production and the motoring ATM/ATR/p53 pathway. In addition, our findings revealed that inflammation's motoring of the ATM/ATR/p53 pathway plays a crucial role in DNA damage. Therefore, exploring the mechanism between inflammation and ROS-dependent DNA damage would be extremely valuable and innovative. This study would somewhat establish a better understanding of inflammation, DNA damage, and cancer.

The endoplasmic reticulum connects to the nucleus by constricted junctions that mature after mitosis

Junctions between the endoplasmic reticulum (ER) and the outer membrane of the nuclear envelope (NE) physically connect both organelles. These ER-NE junctions are essential for supplying the NE with lipids and proteins synthesized in the ER. However, little is known about the structure of these ER-NE junctions. Here, we systematically study the ultrastructure of ER-NE junctions in cryo-fixed mammalian cells staged in anaphase, telophase, and interphase by correlating live cell imaging with three-dimensional electron microscopy. Our results show that ER-NE junctions in interphase cells have a pronounced hourglass shape with a constricted neck of 7-20 nm width. This morphology is significantly distinct from that of junctions within the ER network, and their morphology emerges as early as telophase. The highly constricted ER-NE junctions are seen in several mammalian cell types, but not in budding yeast. We speculate that the unique and highly constricted ER-NE junctions are regulated via novel mechanisms that contribute to ER-to-NE lipid and protein traffic in higher eukaryotes.

Pervasive nuclear envelope ruptures precede ECM signaling and disease onset without activating cGAS-STING in Lamin-cardiomyopathy mice

Nuclear envelope (NE) ruptures are emerging observations in Lamin-related dilated cardiomyopathy, an adult-onset disease caused by loss-of-function mutations in Lamin A/C, a nuclear lamina component. Here, we test a prevailing hypothesis that NE ruptures trigger the pathological cGAS-STING cytosolic DNA-sensing pathway using a mouse model of Lamin cardiomyopathy. The reduction of Lamin A/C in cardio-myocyte of adult mice causes pervasive NE ruptures in cardiomyocytes, preceding inflammatory transcription, fibrosis, and fatal dilated cardiomyopathy. NE ruptures are followed by DNA damage accumulation without causing immediate cardiomyocyte death. However, cGAS-STING-dependent inflammatory signaling remains inactive. Deleting cGas or Sting does not rescue cardiomyopathy in the mouse model. The lack of cGAS-STING activation is likely due to the near absence of cGAS expression in adult cardiomyocytes at baseline. Instead, extracellular matrix (ECM) signaling is activated and predicted to initiate pro-inflammatory communication from Lamin-reduced cardiomyocytes to fibroblasts. Our work nominates ECM signaling, not cGAS-STING, as a potential inflammatory contributor in Lamin cardiomyopathy.

Pervasive nuclear envelope ruptures precede ECM signaling and disease onset without activating cGAS-STING in Lamin-cardiomyopathy mice

Nuclear envelope (NE) ruptures are emerging observations in Lamin-related dilated cardiomyopathy, an adult-onset disease caused by loss-of-function mutations in Lamin A/C, a nuclear lamina component. Here, we tested a prevailing hypothesis that NE ruptures trigger pathological cGAS-STING cytosolic DNA-sensing pathway, using a mouse model of Lamin-cardiomyopathy. Reduction of Lamin A/C in cardiomyocytes of adult mice caused pervasive NE ruptures in cardiomyocytes, preceding inflammatory transcription, fibrosis, and fatal dilated cardiomyopathy. NE ruptures were followed by DNA damage accumulation without causing immediate cardiomyocyte death. However, cGAS-STING-dependent inflammatory signaling remained inactive. Deleting cGas or Sting did not rescue cardiomyopathy. The lack of cGAS-STING activation was likely due to the near absence of cGAS expression in adult cardiomyocytes at baseline. Instead, extracellular matrix (ECM) signaling was activated and predicted to initiate pro-inflammatory communication from Lamin-reduced cardiomyocytes to fibroblasts. Our work nominates ECM signaling, not cGAS-STING, as a potential inflammatory contributor in Lamin-cardiomyopathy.

Investigating ultrastructural morphology in MIRAGE syndrome-derived fibroblasts using transmission electron microscopy

Background

Heterozygous de novo variants in the gene SAMD9 cause the complex multisystem disorder, MIRAGE syndrome. Patients are characterised by myelodysplasia, infections, growth restriction, adrenal insufficiency, gonadal dysfunction and enteropathies. Pathogenic variants in SAMD9 are gain-of-function and enhance its role as a growth repressor, leading to growth restriction of many tissues. Two studies have reported changes in skin fibroblasts derived from MIRAGE patients, more specifically identifying enlarged endosomes. We have also previously shown subtle changes in endosome size in patients' fibroblasts compared to controls. However, these variations in endosomes were not as marked as those described in the literature.

Methods

We have performed an observational study using transmission electron microscopy (TEM) in a larger number of cells derived from three patients' fibroblasts to assess ultrastructure morphology compared to control images.

Results

Consistent changes were observed in cell organelles in all patient samples. In particular, increased endosomal activity was detected, characterised by augmented pinocytosis and vesicle budding, increased endosome number, as well as by large lysosomes and endosomes. Endoplasmic reticulum was also prominent. Mitochondria appeared enlarged in selected cells, possibly due to cellular stress. Cell nuclei did not display major differences compared to controls.

Conclusions

TEM is a powerful tool to investigate morphological features of tissues and cell organelles, although TEM data could be affected by sample preparation methodology, therefore potentially explaining the variability between independent studies, and its analysis can be dependent on the experience of the researcher. The increased endosomal activity we have observed in patients' fibroblasts could indicate that SAMD9 regulates endocytosis of receptors, acting as an endosome fusion facilitator, or in lysosomal activation. However, the precise mechanism(s) by which SAMD9 regulates cell growth is still not fully understood, and further studies are needed to elucidate its pathogenic pathway and develop therapeutic approaches to support patients.

DNA density is a better indicator of a nuclear bleb than lamin B loss

Nuclear blebs are herniations of the nucleus that occur in diseased nuclei that cause nuclear rupture leading to cellular dysfunction. Chromatin and lamins are two of the major structural components of the nucleus that maintain its shape and function, but their relative roles in nuclear blebbing remain elusive. Lamin B is reported to be lost in blebs by qualitative data while quantitative studies reveal a spectrum of lamin B levels in nuclear blebs dependent on perturbation and cell type. Chromatin has been reported to be decreased or de-compacted in nuclear blebs, but again the data are not conclusive. To determine the composition of nuclear blebs, we compared the immunofluorescence intensity of lamin B and DNA in the main nucleus body and nuclear bleb across cell types and perturbations. Lamin B nuclear bleb levels varied drastically across MEF wild type and chromatin or lamins perturbations, HCT116 lamin B1-GFP imaging, and human disease model cells of progeria and prostate cancer. However, DNA concentration was consistently decreased to about half that of the main nucleus body across all measured conditions. Using Partial Wave Spectroscopic (PWS) microscopy to measure chromatin density in the nuclear bleb vs body we find similar results that DNA is consistently less dense in nuclear blebs. Thus, our data spanning many different cell types and perturbations supports that decreased DNA is a better marker of a nuclear bleb than lamin B levels that vary widely.

Nuclear envelope assembly relies on CHMP-7 in the absence of BAF-LEM-mediated hole closure

Barrier-to-autointegration factor (BAF) protein is a DNA-binding protein that crosslinks chromatin to allow mitotic nuclear envelope (NE) assembly. The LAP2-emerin-MAN1 (LEM)-domain protein LEMD2 and ESCRT-II/III hybrid protein CHMP7 close NE holes surrounding spindle microtubules (MTs). BAF binds LEM-domain family proteins to repair NE ruptures in interphase, but whether BAF-LEM binding participates in NE hole closure around spindle MTs is not known. Here, we took advantage of the stereotypical event of NE formation in fertilized Caenorhabditis elegans oocytes to show that BAF-LEM binding and LEM-2-CHMP-7 have distinct roles in NE closure around spindle MTs. LEM-2 and EMR-1 (homologs of LEMD2 and emerin) function redundantly with BAF-1 (the C. elegans BAF protein) in NE closure. Compromising BAF-LEM binding revealed an additional role for EMR-1 in the maintenance of the NE permeability barrier. In the absence of BAF-LEM binding, LEM-2-CHMP-7 was required for NE assembly and embryo survival. The winged helix domain of LEM-2 recruits CHMP-7 to the NE in C. elegans and a LEM-2-independent nucleoplasmic pool of CHMP-7 also contributes to NE stability. Thus, NE hole closure surrounding spindle MTs requires redundant mechanisms that safeguard against failure in NE assembly to support embryogenesis.

Nuclear envelope assembly relies on CHMP-7 in the absence of BAF-LEM-mediated hole closure

Barrier-to-autointegration factor (BAF) is a DNA binding protein that crosslinks chromatin to assemble the nuclear envelope (NE) after mitosis. BAF also binds the Lap2b-Emerin-Man1 (LEM) domain family of NE proteins to repair interphase ruptures. The NE adaptors to ESCRTs, LEMD2-CHMP7, seal NE holes surrounding mitotic spindle microtubules (MTs), but whether NE hole closure in mitosis involves BAF-LEM binding is not known. Here, we analyze NE sealing after meiosis II in C. elegans oocytes to show that BAF-LEM binding and LEM-2 LEMD2 -CHMP-7 have distinct roles in hole closure around spindle MTs. LEM-2/EMR-1 emerin function redundantly with BAF-1 to seal the NE. Compromising BAF-LEM binding revealed an additional role for EMR-1 in maintenance of the NE permeability barrier and an essential role for LEM-2-CHMP-7 in preventing NE assembly failure. The WH domain of LEM-2 recruits the majority of CHMP-7 to the NE in C. elegans and a LEM-2 -independent pool of CHMP-7, which is mostly enriched in the nucleoplasm, also contributes to NE stability. Thus, NE hole closure surrounding spindle MTs requires redundant mechanisms that safeguard against failure in NE assembly to support embryogenesis.

Chromosomal Instability in Genome Evolution: From Cancer to Macroevolution

The integrity of the genome is crucial for the survival of all living organisms. However, genomes need to adapt to survive certain pressures, and for this purpose use several mechanisms to diversify. Chromosomal instability (CIN) is one of the main mechanisms leading to the creation of genomic heterogeneity by altering the number of chromosomes and changing their structures. In this review, we will discuss the different chromosomal patterns and changes observed in speciation, in evolutional biology as well as during tumor progression. By nature, the human genome shows an induction of diversity during gametogenesis but as well during tumorigenesis that can conclude in drastic changes such as the whole genome doubling to more discrete changes as the complex chromosomal rearrangement chromothripsis. More importantly, changes observed during speciation are strikingly similar to the genomic evolution observed during tumor progression and resistance to therapy. The different origins of CIN will be treated as the importance of double-strand breaks (DSBs) or the consequences of micronuclei. We will also explain the mechanisms behind the controlled DSBs, and recombination of homologous chromosomes observed during meiosis, to explain how errors lead to similar patterns observed during tumorigenesis. Then, we will also list several diseases associated with CIN, resulting in fertility issues, miscarriage, rare genetic diseases, and cancer. Understanding better chromosomal instability as a whole is primordial for the understanding of mechanisms leading to tumor progression.

Leucocyte Abnormalities in Synovial Fluid of Degenerative and Inflammatory Arthropathies

Genome damage has been related to the induction of autoimmune processes, chronic inflammation, and apoptosis. Recent studies suggest that some rheumatological diseases are associated with overall genomic instability in the T cell compartment. However, no data regarding leucocyte abnormalities in synovial fluid (SF) and their relationship with inflammation are available. The aim of this study was to investigate cellular phenotypes in SF collected from patients with different inflammatory arthropathies, including rhematoid arthritis (RA), psoriatic arthritis (PsA), crystal-induced arthritis (CIA), and non-inflammatory arthropathies, such as osteoarthritis (OA). We found high percentage of micronuclei in SF from CIA compared to the other groups and a high frequency of pyknotic cell in RA and CIA patients. A correlation between pyknosis and immature polymorphonuclear cells with local inflammatory indices was observed. The study of the apoptosis process revealed an increased BAX expression in CIA and RA compared to OA and PsA, while Bcl-2 was higher in CIA. Caspase-3 activity was increased in SF from RA patients and correlates with inflammatory and anti-inflammatory cytokines. In conclusion, our results showed that inflammatory SF is associated with genomic instability and abnormal cell subsets.

The second half of mitosis and its implications in cancer biology

The nucleus undergoes dramatic structural and functional changes during cell division. With the entry into mitosis, in human cells the nuclear envelope breaks down, chromosomes rearrange into rod-like structures which are collected and segregated by the spindle apparatus. While these processes in the first half of mitosis have been intensively studied, much less is known about the second half of mitosis, when a functional nucleus reforms in each of the emerging cells. Here we review our current understanding of mitotic exit and nuclear reformation with spotlights on the links to cancer biology.

Exercise sustains the hallmarks of health

Exercise has long been known for its active role in improving physical fitness and sustaining health. Regular moderate-intensity exercise improves all aspects of human health and is widely accepted as a preventative and therapeutic strategy for various diseases. It is well-documented that exercise maintains and restores homeostasis at the organismal, tissue, cellular, and molecular levels to stimulate positive physiological adaptations that consequently protect against various pathological conditions. Here we mainly summarize how moderate-intensity exercise affects the major hallmarks of health, including the integrity of barriers, containment of local perturbations, recycling and turnover, integration of circuitries, rhythmic oscillations, homeostatic resilience, hormetic regulation, as well as repair and regeneration. Furthermore, we summarize the current understanding of the mechanisms responsible for beneficial adaptations in response to exercise. This review aimed at providing a comprehensive summary of the vital biological mechanisms through which moderate-intensity exercise maintains health and opens a window for its application in other health interventions. We hope that continuing investigation in this field will further increase our understanding of the processes involved in the positive role of moderate-intensity exercise and thus get us closer to the identification of new therapeutics that improve quality of life.

Bibliometric and Visualized Analysis of the Current Status on STING Signaling Pathway and Cancer

Cancer, as the second leading cause of death worldwide, has become an ongoing public health challenge and its treatment has received much attention, with immunotherapy becoming a hot research topic in recent years. The interferon gene stimulating factor (STING)-mediated signaling pathway has a “double-edged sword” role in cancer, which plays different roles in different types and stages of tumors. In this paper, we discuss the current research status, cooperation, and hotspots of STING signaling pathway in cancer from 2008–2022 using CiteSpace software based on the literature of cancer and STING signaling pathway. In addition, we predicted future research trends in this field by analysis, and the results showed that the STING signaling pathway is rapidly increasing in cancer research, and its role in tumor microenvironment and immunotherapy has become a new hot spot in current research and will continue to receive high attention.

Grease in the Nucleus: Insights into the Dynamic Life of Nuclear Membranes

Nucleus is at the center stage of cellular drama orchestrated in the life of a cell and the nucleoplasm is surrounded by a double membranous compartment constituting the Nuclear membrane/envelope (NE) that separates it from the cytoplasm in nucleated cells. The initial understanding of the NE was that of a border security entity between the nucleus and the cytoplasm, separating gene regulation and transcription in the nucleus from translation in the cytoplasm. However, the discovery of a wide array of inherited diseases caused by mutations in genes encoding proteins that reside or interact with NE diverted the interest into deciphering the lipid-protein-rich environment of the NE. Today, the NE is considered a dynamic organelle which forms a functional linkage between the nucleus and the rest of the cell. The exposure of NE to constant mechanical constraints by its connectivity to the large polymer network of the lamina and chromatin on one side, and to the cytoskeleton on the other side results, in a variety of shape changes. We discuss two such deformation, the formation of nuclear blebs and nucleoplasmic reticulum (NER). Although the protein and the lipid composition of NE comprises a small fraction of the total lipid-protein load of the cell, the ability to define the lipid-protein composition of Inner nuclear membrane (INM) and Outer nuclear membrane (ONM) with precision is crucial for obtaining a deeper mechanistic understanding of their lipid-protein interaction and the various signaling pathways that are triggered by them. In addition, this allows us to further understand the direct and indirect roles of NE machinery in the chromosomal organization and gene regulation.

Graphical Abstract

Type-I Interferon Signaling in Fanconi Anemia

Fanconi Anemia (FA) is a genome instability syndrome caused by mutations in one of the 23 repair genes of the Fanconi pathway. This heterogenous disease is usually characterized by congenital abnormalities, premature ageing and bone marrow failure. FA patients also show a high predisposition to hematological and solid cancers. The Fanconi pathway ensures the repair of interstrand crosslinks (ICLs) DNA damage. Defect in one of its proteins prevents functional DNA repair, leading to the accumulation of DNA breaks and genome instability. Accumulating evidence has documented a close relationship between genome instability and inflammation, including the production of type-I Interferon. In this context, type-I Interferon is produced upon activation of pattern recognition receptors by nucleic acids including by the cyclic GMP-AMP synthase (cGAS) that detects DNA. In mouse models of diseases displaying genome instability, type-I Interferon response is responsible for an important part of the pathological symptoms, including premature aging, short stature, and neurodegeneration. This is illustrated in mouse models of Ataxia-telangiectasia and Aicardi-Goutières Syndrome in which genetic depletion of either Interferon Receptor IFNAR, cGAS or STING relieves pathological symptoms. FA is also a genetic instability syndrome with symptoms such as premature aging and predisposition to cancer. In this review we will focus on the different molecular mechanisms potentially leading to type-I Interferon activation. A better understanding of the molecular mechanisms engaging type-I Interferon signaling in FA may ultimately lead to the discovery of new therapeutic targets to rescue the pathological inflammation and premature aging associated with Fanconi Anemia.

Current Methods and Pipelines for Image-Based Quantitation of Nuclear Shape and Nuclear Envelope Abnormalities

Any given cell type has an associated "normal" nuclear morphology, which is important to maintain proper cellular functioning and safeguard genomic integrity. Deviations from this can be indicative of diseases such as cancer or premature aging syndrome. To accurately assess nuclear abnormalities, it is important to use quantitative measures of nuclear morphology. Here, we give an overview of several nuclear abnormalities, including micronuclei, nuclear envelope invaginations, blebs and ruptures, and review the current methods used for image-based quantification of these abnormalities. We discuss several parameters that can be used to quantify nuclear shape and compare their outputs using example images. In addition, we present new pipelines for quantitative analysis of nuclear blebs and invaginations. Quantitative analyses of nuclear aberrations and shape will be important in a wide range of applications, from assessments of cancer cell anomalies to studies of nucleus deformability under mechanical or other types of stress.

Nuclear Fragility in Radiation-Induced Senescence: Blebs and Tubes Visualized by 3D Electron Microscopy

Irreparable DNA damage following ionizing radiation (IR) triggers prolonged DNA damage response and induces premature senescence. Cellular senescence is a permanent state of cell-cycle arrest characterized by chromatin restructuring, altered nuclear morphology and acquisition of secretory phenotype, which contributes to senescence-related inflammation. However, the mechanistic connections for radiation-induced DNA damage that trigger these senescence-associated hallmarks are poorly understood. In our in vitro model of radiation-induced senescence, mass spectrometry-based proteomics was combined with high-resolution imaging techniques to investigate the interrelations between altered chromatin compaction, nuclear envelope destabilization and nucleo-cytoplasmic chromatin blebbing. Our findings confirm the general pathophysiology of the senescence-response, with disruption of nuclear lamin organization leading to extensive chromatin restructuring and destabilization of the nuclear membrane with release of chromatin fragments into the cytosol, thereby activating cGAS-STING-dependent interferon signaling. By serial block-face scanning electron microscopy (SBF-SEM) whole-cell datasets were acquired to investigate the morphological organization of senescent fibroblasts. High-resolution 3-dimensional (3D) reconstruction of the complex nuclear shape allows us to precisely visualize the segregation of nuclear blebs from the main nucleus and their fusion with lysosomes. By multi-view 3D electron microscopy, we identified nanotubular channels formed in lamin-perturbed nuclei of senescent fibroblasts; the potential role of these nucleo-cytoplasmic nanotubes for expulsion of damaged chromatin has to be examined.

Physical Forces and Transient Nuclear Envelope Rupture during Metastasis: The Key for Success?

Simple Summary

Metastasis is the process that allows the seeding of tumor cells in a new organ. The migration and invasion of cancer cells involves the pulling, pushing, and squeezing of cells through narrow spaces and pores. Tumor cells need to cross several physical barriers, such as layers of basement membranes as well as the endothelium wall during the way in and out of the blood stream, to reach the new organ. The aim of this review is to highlight the role of physical compression in the success of metastasis. We will especially focus on nuclear squeezing and nuclear envelope rupture and explain how they can actively participate in the creation of genomic heterogeneity as well as supporting metastasis growth.

Abstract

During metastasis, invading tumor cells and circulating tumor cells (CTC) face multiple mechanical challenges during migration through narrow pores and cell squeezing. However, little is known on the importance and consequences of mechanical stress for tumor progression and success in invading a new organ. Recently, several studies have shown that cell constriction can lead to nuclear envelope rupture (NER) during interphase. This loss of proper nuclear compartmentalization has a profound effect on the genome, being a key driver for the genome evolution needed for tumor progression. More than just being a source of genomic alterations, the transient nuclear envelope collapse can also support metastatic growth by several mechanisms involving the innate immune response cGAS/STING pathway. In this review we will describe the importance of the underestimated role of cellular squeezing in the progression of tumorigenesis. We will describe the complexity and difficulty for tumor cells to reach the metastatic site, detail the genomic aberration diversity due to NER, and highlight the importance of the activation of the innate immune pathway on cell survival. Cellular adaptation and nuclear deformation can be the key to the metastasis success in many unsuspected aspects.

Investigations concerning the impact of consumption of hot beverages on acute cytotoxic and genotoxic effects in oral mucosa cells

Consumption of very hot beverages and foods increases the incidence of oral and esophageal cancer but the mechanisms are not known and the critical temperature is not well defined. We realized a study with exfoliated cells from the oral cavity of individuals (n = 73) that live in an area in Iran which has the highest incidence of EC worldwide. Consumption of beverages at very high temperatures is a characteristic feature of this population. We analyzed biomarkers which are (i) indicative for genetic instability (micronuclei that are formed as a consequence of chromosomal damage, nuclear buds which are a consequence of gene amplifications and binucleated cells which reflect mitotic disturbances), (ii) markers that reflect cytotoxic effects (condensed chromatin, karyorrhectic, karyolitic and pyknotic cells), (iii) furthermore, we determined the number of basal cells which is indicative for the regenerative capacity of the buccal mucosa. The impact of the drinking temperature on the frequencies of these parameters was monitored with thermometers. We found no evidence for induction of genetic damage but an increase of the cytotoxic effects with the temperature was evident. This effect was paralleled by an increase of the cell division rate of the mucosa which was observed when the temperature exceeded 60 °C. Our findings indicate that cancer in the upper digestive tract in drinkers of very hot beverages is not caused by damage of the genetic material but by an increase of the cell division rate as a consequence of cytotoxic effects which take place at temperatures over 60 °C. It is known from earlier experiments with rodents that increased cell divisions lead to tumor promotion in the esophagus. Our findings provide a mechanistic explanation and indicate that increased cancer risks can be expected when the drinking temperature of beverages exceeds 60 °C.