Multipolar mitosis and aneuploidy after chrysotile treatment: a consequence of abscission failure and cytokinesis regression

Calpeptin is a potent cathepsin inhibitor and drug candidate for SARS-CoV-2 infections

Several drug screening campaigns identified Calpeptin as a drug candidate against SARS-CoV-2. Initially reported to target the viral main protease (Mpro), its moderate activity in Mpro inhibition assays hints at a second target. Indeed, we show that Calpeptin is an extremely potent cysteine cathepsin inhibitor, a finding additionally supported by X-ray crystallography. Cell infection assays proved Calpeptin's efficacy against SARS-CoV-2. Treatment of SARS-CoV-2-infected Golden Syrian hamsters with sulfonated Calpeptin at a dose of 1 mg/kg body weight reduces the viral load in the trachea. Despite a higher risk of side effects, an intrinsic advantage in targeting host proteins is their mutational stability in contrast to highly mutable viral targets. Here we show that the inhibition of cathepsins, a protein family of the host organism, by calpeptin is a promising approach for the treatment of SARS-CoV-2 and potentially other viral infections.

Synthetic Secoisolariciresinol Diglucoside (LGM2605) Prevents Asbestos-Induced Inflammation and Genotoxic Cell Damage in Human Mesothelial Cells

Although alveolar macrophages play a critical role in malignant transformation of mesothelial cells following asbestos exposure, inflammatory and oxidative processes continue to occur in the mesothelial cells lining the pleura that may contribute to the carcinogenic process. Malignant transformation of mesothelial cells following asbestos exposure occurs over several decades; however, amelioration of DNA damage, inflammation, and cell injury may impede the carcinogenic process. We have shown in an in vitro model of asbestos-induced macrophage activation that synthetic secoisolariciresinol diglucoside (LGM2605), given preventively, reduced inflammatory cascades and oxidative/nitrosative cell damage. Therefore, it was hypothesized that LGM2605 could also be effective in reducing asbestos-induced activation and the damage of pleural mesothelial cells. LGM2605 treatment (50 µM) of huma n pleural mesothelial cells was initiated 4 h prior to exposure to asbestos (crocidolite, 20 µg/cm2). Supernatant and cells were evaluated at 0, 2, 4, and 8 h post asbestos exposure for reactive oxygen species (ROS) generation, DNA damage (oxidized guanine), inflammasome activation (caspase-1 activity) and associated pro-inflammatory cytokine release (IL-1β, IL-18, IL-6, TNFα, and HMGB1), and markers of oxidative stress (malondialdehyde (MDA) and 8-iso-prostaglandin F2a (8-iso-PGF2α). Asbestos induced a time-dependent ROS increase that was significantly (p < 0.0001) reduced (29.4%) by LGM2605 treatment. LGM2605 pretreatment also reduced levels of asbestos-induced DNA damage by 73.6% ± 1.0%. Although levels of inflammasome-activated cytokines, IL-1β and IL-18, reached 29.2 pg/mL ± 0.7 pg/mL and 43.9 pg/mL ± 0.8 pg/mL, respectively, LGM2605 treatment significantly (p < 0.0001) reduced cytokine levels comparable to baseline (non-asbestos exposed) values (3.8 pg/mL ± 0.2 pg/mL and 5.4 pg/mL ± 0.2 pg/mL, respectively). Furthermore, levels of IL-6 and TNFα in asbestos-exposed mesothelial cells were high (289.1 pg/mL ± 2.9 pg/mL and 511.3 pg/mL ± 10.2 pg/mL, respectively), while remaining undetectable with LGM2605 pretreatment. HMGB1 (a key inflammatory mediator and initiator of malignant transformation) release was reduced 75.3% ± 0.4% by LGM2605. Levels of MDA and 8-iso-PGF2α, markers of oxidative cell injury, were significantly (p < 0.001) reduced by 80.5% ± 0.1% and 76.6% ± 0.3%, respectively. LGM2605, given preventively, reduced ROS generation, DNA damage, and inflammasome-activated cytokine release and key inflammatory mediators implicated in asbestos-induced malignant transformation of normal mesothelial cells.

Adenosine Kinase on Deoxyribonucleic Acid Methylation: Adenosine Receptor-Independent Pathway in Cancer Therapy

Methylation is an important mechanism contributing to cancer pathology. Methylation of tumor suppressor genes and oncogenes has been closely associated with tumor occurrence and development. New insights regarding the potential role of the adenosine receptor-independent pathway in the epigenetic modulation of DNA methylation offer the possibility of new interventional strategies for cancer therapy. Targeting DNA methylation of cancer-related genes is a promising therapeutic strategy; drugs like 5-Aza-2′-deoxycytidine (5-AZA-CdR, decitabine) effectively reverse DNA methylation and cancer cell growth. However, current anti-methylation (or methylation modifiers) are associated with severe side effects; thus, there is an urgent need for safer and more specific inhibitors of DNA methylation (or DNA methylation modifiers). The adenosine signaling pathway is reported to be involved in cancer pathology and participates in the development of tumors by altering DNA methylation. Most recently, an adenosine metabolic clearance enzyme, adenosine kinase (ADK), has been shown to influence methylation on tumor suppressor genes and tumor development and progression. This review article focuses on recent updates on ADK and its two isoforms, and its actions in adenosine receptor-independent pathways, including methylation modification and epigenetic changes in cancer pathology.

Extract of bulbus of Fritillaria cirrhosa induces spindle multipolarity in human-derived colonic epithelial NCM460 cells through promoting centrosome fragmentation

Bulbus of Fritillaria cirrhosa D. Don (BFC), an outstanding antitussive and expectorant herbal drug used in China and many other countries, has potential but less understood genotoxicity. Previously, we have reported that aqueous extract of BFC compromised the spindle assembly checkpoint and cytokinesis in NCM460 cells. Here, we found that one remarkable observation in BFC-treated NCM460 cells was multipolar mitosis, a trait classically compromises the fidelity of chromosome segregation. More detailed investigation revealed that BFC-induced spindle multipolarity in metaphases and ana-telophases in a dose- and time-dependent manner, suggesting BFC-induced multipolar spindle conformation was not transient. The frequency of multipolar metaphase correlated well to that of multipolar ana-telophases, indicating that BFC-induced multipolar metaphases often persisted through anaphase. Unexpectedly, BFC blocked the proliferation of binucleated cells, suggesting spindle multipolarity was not downstream of BFC-induced cytokinesis failure. Exposure of BFC to early mitotic cells, rather than S/G2 cells, contributed greatly to spindle multipolarity, indicating BFC might disrupt centrosome integrity rather than induce centrosome overduplication. The immunofluorescence results showed that the centrosomes were severely fragmented by a short-term treatment of BFC and the extent of centrosome fragmentation in early mitotic cells was larger than this in S/G2 cells. Consistently, several genes (e.g. p53, Rb centrin-2, Plk-4, Plk-1 and Aurora-A) involved in regulating centrosome integrity were significantly deregulated by BFC. Together, our results suggest that BFC causes multipolar spindles primarily by inducing centrosome fragmentation. Coupling these results to our previous observations, we recommend the risk/benefit ratio should be considered in the practical use of BFC.

Centrosome amplification in cancer and cancer-associated human diseases

Accumulated evidence from genetically modified cell and animal models indicates that centrosome amplification (CA) can initiate tumorigenesis with metastatic potential and enhance cell invasion. Multiple human diseases are associated with CA and carcinogenesis as well as metastasis, including infection with oncogenic viruses, type 2 diabetes, toxicosis by environmental pollution and inflammatory disease. In this review, we summarize (1) the evidence for the roles of CA in tumorigenesis and tumor cell invasion; (2) the association between diseases and carcinogenesis as well as metastasis; (3) the current knowledge of CA in the diseases; and (4) the signaling pathways of CA. We then give our own thinking and discuss perspectives relevant to CA in carcinogenesis and cancer metastasis in human diseases. In conclusion, investigations in this area might not only identify CA as a biological link between these diseases and the development of cancer but also prove the causal role of CA in cancer and progression under pathophysiological conditions, potentially taking cancer research into a new era.

Karyotype Aberrations in Action: The Evolution of Cancer Genomes and the Tumor Microenvironment

Cancer is a disease of cellular evolution. For this cellular evolution to take place, a population of cells must contain functional heterogeneity and an assessment of this heterogeneity in the form of natural selection. Cancer cells from advanced malignancies are genomically and functionally very different compared to the healthy cells from which they evolved. Genomic alterations include aneuploidy (numerical and structural changes in chromosome content) and polyploidy (e.g., whole genome doubling), which can have considerable effects on cell physiology and phenotype. Likewise, conditions in the tumor microenvironment are spatially heterogeneous and vastly different than in healthy tissues, resulting in a number of environmental niches that play important roles in driving the evolution of tumor cells. While a number of studies have documented abnormal conditions of the tumor microenvironment and the cellular consequences of aneuploidy and polyploidy, a thorough overview of the interplay between karyotypically abnormal cells and the tissue and tumor microenvironments is not available. Here, we examine the evidence for how this interaction may unfold during tumor evolution. We describe a bidirectional interplay in which aneuploid and polyploid cells alter and shape the microenvironment in which they and their progeny reside; in turn, this microenvironment modulates the rate of genesis for new karyotype aberrations and selects for cells that are most fit under a given condition. We conclude by discussing the importance of this interaction for tumor evolution and the possibility of leveraging our understanding of this interplay for cancer therapy.

Intrinsic and chemically-induced daughter number variations in cancer cell lines

Multipolar mitosis was observed in cancer cells under mechanical stress or drug treatment. However, a comprehensive understanding of its basic properties and significance to cancer cell biology is lacking. In the present study, live-cell imaging was employed to investigate the division and nucleation patterns in four different cell lines. Multi-daughter divisions were observed in the three cancer cell lines HepG2, HeLa and A549, but not in the transformed non-cancer cell line RPE1. Multi-daughter mother cells displayed multi-nucleation, enlarged cell area, and prolonged division time. Under acidic pH or treatment with the anti-cancer drug 5-fluorouracil (5-FU) or the phytochemical compound wogonin, multi-daughter mitoses were increased to different extents in all three cancer cell lines, reaching as high as 16% of all mitoses. While less than 0.4% of the bi-daughter mitosis were followed by cell fusion events under the various treatment conditions, 50% or more of the multi-daughter mitoses were followed by fusion events at neutral, acidic or alkaline pH. These findings revealed a "Daughter Number Variation" (DNV) process in the cancer cells, with multi-daughter divisions in Stage 1 and cell fusions leading to the formation of cells containing up to five nuclei in Stage 2. The Stage 2-fusions were inhibited by 5-FU in A549 and HeLa, and by wogonin in A549, HeLa and HepG2. The parallel relationship between DNV frequency and malignancy among the different cell lines suggests that the inclusion of anti-fusion agents exemplified by wogonin and 5-FU could be beneficial in combinatory cancer chemotherapies.

Structure and function of Septin 9 and its role in human malignant tumors

The treatment and prognosis of malignant tumors are closely related to the time when the tumors are diagnosed; the earlier the diagnosis of the tumor, the better the prognosis. However, most tumors are not detected in the early stages of screening and diagnosis. It is of great clinical significance to study the correlation between multiple pathogeneses of tumors and explore simple, safe, specific, and sensitive molecular indicators for early screening, diagnosis, and prognosis. The Septin 9 (SEPT9) gene has been found to be associated with a variety of human diseases, and it plays a role in the development of tumors. SEPT9 is a member of the conserved family of cytoskeletal GTPase, which consists of a P-loop-based GTP-binding domain flanked by a variable N-terminal region and a C-terminal region. SEPT9 is involved in many biological processes such as cytokinesis, polarization, vesicle trafficking, membrane reconstruction, deoxyribonucleic acid repair, cell migration, and apoptosis. Several studies have shown that SEPT9 may serve as a marker for early screening, diagnosis, and prognosis of some malignant tumors, and have the potential to become a new target for anti-cancer therapy. This article reviews the progress in research on the SEPT9 gene in early screening, diagnosis, and prognosis of tumors.

Septin and Ras regulate cytokinetic abscission in detached cells

Background

Integrin-mediated adhesion is normally required for cytokinetic abscission, and failure in the process can generate potentially oncogenic tetraploid cells. Here, detachment-induced formation of oncogenic tetraploid cells was analyzed in non-transformed human BJ fibroblasts and BJ expressing SV40LT (BJ-LT) ± overactive HRas.

Results

In contrast to BJ and BJ-LT cells, non-adherent BJ-LT-Ras cells recruited ALIX and CHMP4B to the midbody and divided. In detached BJ and BJ-LT cells regression of the cytokinetic furrow was suppressed by intercellular bridge-associated septin; after re-adhesion these cells divided by cytofission, however, some cells became bi-nucleated because of septin reorganization and furrow regression. Adherent bi-nucleated BJ cells became senescent in G1 with p21 accumulation in the nucleus, apparently due to p53 activation since adherent bi-nucleated BJ-LT cells passed through next cell cycle and divided into mono-nucleated tetraploids; the two centrosomes present in bi-nucleated BJ cells fused after furrow regression, pointing to the PIDDosome pathway as a possible mechanism for the p53 activation.

Conclusions

Several mechanisms prevent detached normal cells from generating tumor-causing tetraploid cells unless they have a suppressed p53 response by viruses, mutation or inflammation. Importantly, activating Ras mutations promote colony growth of detached transformed cells by inducing anchorage-independent cytokinetic abscission in single cells.

Expression of septin 2 and association with clinicopathological parameters in colorectal cancer

Septin 2 (SEPT2) is a tumor-related gene belonging to the SEPT family that affects the cellular processes of hepatoma carcinoma cells, glioblastoma cells and mesangial cells and is highly expressed in breast cancer, biliary tract cancer and acute myeloid leukemia. Colorectal cancer (CRC) is the third most common type of malignancy in humans. In the present study, Oncomine database was used to compare the expression pattern of SEPT2 mRNA between CRC and normal tissues. Additionally, protein expression in 90 pairs of CRC and paracancerous tissues was analyzed by western blotting and immunohistochemistry (IHC). The results showed that SEPT2 was highly expressed in CRC tissues at the mRNA and protein levels. SEPT2 expression quantified by IHC was associated with lymph node metastasis, the degree of differentiation and TNM staging. Increased SEPT2 wass associated with reduced overall survival (OS) according to Kaplan-Meier analysis. COX proportional hazard analysis indicated that SEPT2 was an independent factor that influenced the OS of patients with CRC. Therefore, SEPT2 was associated with the occurrence, progression and prognosis of CRC and thus, may be a marker and prognostic indicator of CRC.

Ingested asbestos in filtered beer, in addition to occupational exposure, as a causative factor in oesophageal adenocarcinoma

Oesophageal adenocarcinoma has become much more common over the past 50 years, particularly in Britain, with an unexplained male to female ratio of > 4:1. Given the use of asbestos filtration in commercial brewing and reports of its unregulated use in British public houses in the 1970's to clear draught beer "slops", we have assessed the hypothesis that ingested asbestos could be a causative factor for this increased incidence. Importantly, occupational asbestos exposure increases the risk of adenocarcinoma but not squamous cell carcinoma of the oesophagus. The presence of asbestos fibres was consistently reported in filtered beverages including beers in the 1970s and asbestos bodies have been found in gastrointestinal tissue, particularly oesophageal tissue, at autopsy. There is no reported association between the intake of alcohol and oesophageal adenocarcinoma but studies would mostly have missed exposure from draught beer before 1980. Oesophageal adenocarcinoma has some molecular similarities to pleural mesothelioma, a condition that is largely due to inhalation of asbestos fibres, including predominant loss of tumour suppressor genes rather than an increase of classical oncogenic drivers. Trends in incidence of oesophageal adenocarcinoma and mesothelioma are similar, rising rapidly over the past 50 years but now plateauing. Asbestos ingestion, either from beer consumed before around 1980, or from occupational exposure, seems a plausible causative factor for oesophageal adenocarcinoma. If this is indeed the case, its incidence should fall back to a low baseline by around 2050.

Role of aneuploidy in the carcinogenic process: Part 3 of the report of the 2017 IWGT workgroup on assessing the risk of aneugens for carcinogenesis and hereditary diseases

Aneuploidy is regarded as a hallmark of cancer, however, its role is complex with both pro- and anti-carcinogenic effects evident. In this IWGT review, we consider the role of aneuploidy in cancer biology; cancer risk associated with constitutive aneuploidy; rodent carcinogenesis with known chemical aneugens; and chemotherapy-related malignant neoplasms. Aneuploidy is seen at various stages in carcinogenesis. However, the relationship between induced aneuploidy occurring after exposure and clonal aneuploidy present in tumours is not clear. Recent evidence indicates that the induction of chromosomal instability (CIN), may be more important than aneuploidy per se, in the carcinogenic process. Down Syndrome, trisomy 21, is associated with altered hematopoiesis in utero which, in combination with subsequent mutations, results in an increased risk for acute megakaryoblastic and lymphoblastic leukemias. In contrast, there is reduced cancer risk for most solid tumours in Down Syndrome. Mouse models with high levels of aneuploidy are also associated with increased cancer risk for particular tumours with long latencies, but paradoxically other types of tumour often show decreased incidence. The aneugens reviewed that induce cancer in humans and animals all possess other carcinogenic properties, such as mutagenicity, clastogenicity, cytotoxicity, organ toxicities, hormonal and epigenetic changes which likely account for, or interact with aneuploidy, to cause carcinogenesis. Although the role that aneuploidy plays in carcinogenesis has not been fully established, in many cases, it may not play a primary causative role. Tubulin-disrupting aneugens that do not possess other properties linked to carcinogenesis, were not carcinogenic in rodents. Similarly, in humans, for the tubulin-disrupting aneugens colchicine and albendazole, there is no reported association with increased cancer risk. There is a need for further mechanistic studies on agents that induce aneuploidy, particularly by mechanisms other than tubulin disruption and to determine the role of aneuploidy in pre-neoplastic events and in early and late stage neoplasia.

Preliminary investigation of the effects of an FCF inhibitor interference with Septin in the early stage embryos in mice

The objective of the present study was to investigate the effects of for chlorfenuron (FCF) interference with the septin protein on early stage embryos in mice. The 1‑cell embryos were collected and divided into an FCF interference group and a control group. The FCF interference group was cultured in FCF media and the control group was cultured in dimethyl sulphoxide media at 37˚C with 5% CO2 until the desired phase was achieved. Septin2 protein expression was detected using immunofluorescence and western blot analysis. Blastocyst α‑tubulin was stained by immunofluorescence to observe the alterations in spindles and microtubules. The rate of early embryo development into blastocysts was significantly reduced following FCF treatment (P<0.05). In the control group, septin2 was observed with a confocal microscope; septin2 was expressed in embryos at all stages and mainly in the blastomeres from the 2‑cell stage onwards, with the expression concentrated in the nuclei of the blastomeres as identified by strong fluorescence. In the FCF interference group, septin2 was weakly expressed in the nuclei of blastomeres at the 2‑ and 4‑cell stages, and in the granulated blastomeres at the 4‑ and 8‑cell stages. Expression was barely observed in and following the morula. Granulation was observed starting from the 4‑ and 8‑cell stages. Compared with the control group, the FCF interference group exhibited irregular microtubules, abnormal spindle morphology and disordered chromosome arrangement in the blastocysts. The septin2 protein was expressed throughout the early stage embryo from the 2‑cell stage to the blastocyst and localized in the nuclei of blastomeres. When the septin protein experienced interference by the FCF inhibitor, septin2 protein expression was reduced, which simultaneously resulted in abnormal embryonic development, uneven cytoplasmic division, various sizes and a reduced number of blastomeres, granulation in the blastomeres, disordered blastocyst microtubule distribution, spindle shape alterations and an abnormality of chromosome arrangement.

Plagiochiline A Inhibits Cytokinetic Abscission and Induces Cell Death

We previously reported on the isolation and biological activities of plagiochiline A (1), a 2,3-secoaromadendrane-type sesquiterpenoid from the Peruvian medicinal plant, Plagiochila disticha. This compound was found to have antiproliferative effects on a variety of solid tumor cell lines, as well as several leukemia cell lines. Other researchers have also noted the cytotoxicity of plagiochiline A (isolated from different plant species), but there are no prior reports regarding the mechanism for this bioactivity. Here, we have evaluated the effects of plagiochiline A on cell cycle progression in DU145 prostate cancer cells. A cell cycle analysis indicated that plagiochiline A caused a significant increase in the percentage of cells in the G₂/M phase when compared with control cells. When cells were stained and observed by fluorescence microscopy to examine progress through the mitotic phase, we found a significant increase in the proportion of cells with features of late cytokinesis (cells connected by intercellular bridges) in the plagiochiline A-treated samples. These results suggest that plagiochiline A inhibits cell division by preventing completion of cytokinesis, particularly at the final abscission stage. We also determined that plagiochiline A reduces DU145 cell survival in clonogenic assays and that it induces substantial cell death in these cells.

Chromosome nondisjunction during bipolar mitoses of binucleated intermediates promote aneuploidy formation along with multipolar mitoses rather than chromosome loss in micronuclei induced by asbestos

Asbestos is a well-known occupational carcinogen that can cause aneuploidy during the early stages of neoplastic development. To explore the origins of asbestos-induced aneuploidy, we performed long-term live-cell imaging followed by fluorescence in situ hybridization of chromosomes 8 and 12 in human bronchial epithelial (HBEC) and mesothelial (MeT5A) cells. We demonstrate that asbestos induces aneuploidy via binucleated intermediates resulting from cytokinesis failure. On the one hand, asbestos increases chromosome nondisjunction during bipolar divisions of binucleated intermediates and produces near-tetraploidy. On the other hand, asbestos increases multipolar divisions of binucleated intermediates to produce aneuploidy. Surprisingly, chromosomes in asbestos-induced micronucleated cells are not truly lost by the cells, and do not contribute to aneuploid cell formation in either cell type. These results clarify the cellular source of asbestos-induced aneuploidy. In particular, they show the asbestos-induced disruption of bipolar chromosomal segregation in tetraploid cells, thereby demonstrating the causality between binucleated intermediates and aneuploidy evolution, rather than chromosome loss in micronuclei.

Evaluating the mechanistic evidence and key data gaps in assessing the potential carcinogenicity of carbon nanotubes and nanofibers in humans

In an evaluation of carbon nanotubes (CNTs) for the IARC Monograph 111, the Mechanisms Subgroup was tasked with assessing the strength of evidence on the potential carcinogenicity of CNTs in humans. The mechanistic evidence was considered to be not strong enough to alter the evaluations based on the animal data. In this paper, we provide an extended, in-depth examination of the in vivo and in vitro experimental studies according to current hypotheses on the carcinogenicity of inhaled particles and fibers. We cite additional studies of CNTs that were not available at the time of the IARC meeting in October 2014, and extend our evaluation to include carbon nanofibers (CNFs). Finally, we identify key data gaps and suggest research needs to reduce uncertainty. The focus of this review is on the cancer risk to workers exposed to airborne CNT or CNF during the production and use of these materials. The findings of this review, in general, affirm those of the original evaluation on the inadequate or limited evidence of carcinogenicity for most types of CNTs and CNFs at this time, and possible carcinogenicity of one type of CNT (MWCNT-7). The key evidence gaps to be filled by research include: investigation of possible associations between in vitro and early-stage in vivo events that may be predictive of lung cancer or mesothelioma, and systematic analysis of dose-response relationships across materials, including evaluation of the influence of physico-chemical properties and experimental factors on the observation of nonmalignant and malignant endpoints.

Cancer-Related Functions and Subcellular Localizations of Septins

Since the initial discovery of septin family GTPases, the understanding of their molecular organization and cellular roles keeps being refined. Septins have been involved in many physiological processes and the misregulation of specific septin gene expression has been implicated in diverse human pathologies, including neurological disorders and cancer. In this minireview, we focus on the importance of the subunit composition and subcellular localization of septins relevant to tumor initiation, progression, and metastasis. We especially underline the importance of septin polymer composition and of their association with the plasma membrane, actin, or microtubules in cell functions involved in cancer and in resistance to cancer therapies. Through their scaffolding role, their function in membrane compartmentalization or through their protective function against protein degradation, septins also emerge as critical organizers of membrane-associated proteins and of signaling pathways implicated in cancer-associated angiogenesis, apoptosis, polarity, migration, proliferation, and in metastasis. Also, the question as to which of the free monomers, hetero-oligomers, or filaments is the functional form of mammalian septins is raised and the control over their spatial and temporal localization is discussed. The increasing amount of crosstalks identified between septins and cellular signaling mediators reinforces the exciting possibility that septins could be new targets in anti-cancer therapies or in therapeutic strategies to limit drug resistance.