Telomere length and micronuclei trajectories in APP/PS1 mouse model of Alzheimer's disease: Correlating with cognitive impairment and brain amyloidosis in a sexually dimorphic manner.

Although studies have demonstrated that genome instability is accumulated in patients with Alzheimer's disease (AD), the specific types of genome instability linked to AD pathogenesis remain poorly understood. Here, we report the first characterization of the age- and sex-related trajectories of telomere length (TL) and micronuclei in APP/PS1 mice model and wild-type (WT) controls (C57BL/6). TL was measured in brain (prefrontal cortex, cerebellum, pituitary gland, and hippocampus), colon and skin, and MN was measured in bone marrow in 6- to 14-month-old mice. Variation in TL was attributable to tissue type, age, genotype and, to a lesser extent, sex. Compared to WT, APP/PS1 had a significantly shorter baseline TL across all examined tissues. TL was inversely associated with age in both genotypes and TL shortening was accelerated in brain of APP/PS1. Age-related increase of micronuclei was observed in both genotypes but was accelerated in APP/PS1. We integrated TL and micronuclei data with data on cognition performance and brain amyloidosis. TL and micronuclei were linearly correlated with cognition performance or Aß40 and Aß42 levels in both genotypes but to a greater extent in APP/PS1. These associations in APP/PS1 mice were dominantly driven by females. Together, our findings provide foundational knowledge to infer the TL and micronuclei trajectories in APP/PS1 mice during disease progression, and strongly support that TL attrition and micronucleation are tightly associated with AD pathogenesis in a female-biased manner.

Presenilin-1, mutated in familial Alzheimer's disease, maintains genome stability via a γ-secretase dependent way.

Mutations in Presenilin-1 (PS1) account for over 80 % mutations linked to familial Alzheimer's disease (AD). However, the mechanisms of action of PS1 mutations in causing familial AD are not fully understood, limiting opportunities to develop targeted disease-modifying therapies for individuals carrying PS1 mutation. To gain more comprehensive insights into the impact of PS1 mutations on genome stability, we knocked down PS1 in SH-SY5Y, HMC3 and A549 cells. This revealed that PS1 knockdown (KD) dramatically induces genome instability (GIN) in all cell types, as indicated by the increased incidence of micronuclei, nucleoplasmic bridges and/or nuclear buds. Although amyloid ß (Aß) was able to induce GIN, PS1-KD was associated with decreased expression of Aß in SH-SY5Y cells, suggesting Aß is not the primary cause of GIN in PS1-KD cells. In contrast, inhibiting the PS1 γ-secretase activity by DAPT recapitulated GIN phenotype as seen in PS1-KD cells, indicating that the induction of GIN following PS1 KD can be attributed to the loss of γ-secretase activity. PS1 KD or γ-secretase inhibition markedly sensitizes SH-SY5Y to the genotoxicity of mitomycin C. Interestingly, overexpression of the wildtype PS1 dramatically increased GIN in SH-SY5Y. Collectively, our study demonstrates the potential of PS1 and its γ-secretase activity in maintaining genome stability, highlighting a novel potential link between PS1 loss-of-function or gain-of-function mutations and familial AD through GIN. Several mechanisms by which GIN induced by PS1 dys-expression may contribute to AD are discussed.

Effects of folate on telomere length and chromosome stability of human fibroblasts and melanoma cells in vitro: a comparison of folic acid and 5-methyltetrahydrofolate.

Telomere length (TL), which is maintained by human telomerase reverse transcriptase (hTERT; component of telomerase) and/or TRF1/TRF2 (core components of shelterin) via different mechanisms, is essential for chromosomal stability and cell survival. Folates comprise a group of essential B9 vitamin that involve in DNA synthesis and methylation. This study aimed to evaluate the effects of folic acid (FA) and 5-methyltetrahydrofolate (5-MeTHF) on TL, chromosome stability, and cell survival of telomerase-negative BJ and telomerase-positive A375 cells in vitro. BJ and A375 cells were cultured in modified medium with FA or 5-MeTHF (22.6 or 2260 nM) for 28 days. TL and mRNA expression were determined by RT-qPCR. Chromosome instability (CIN) and cell death were measured by CBMN-Cyt assay. Results showed that abnormal TL elongation was observed in FA- and 5-MeTHF-deficient BJ cells. The TL of A375 cells showed no obvious alterations under the FA-deficient condition but was significantly elongated under the 5-MeTHF-deficient condition. In both BJ and A375 cells, FA and 5-MeTHF deficiency caused decreased TRF1, TRF2, and hTERT expression, increased CIN and cell death; while a high concentration of 5-MeTHF induced elongated TL, elevated CIN, increased TRF1 and TRF2 expression, and decreased hTERT expression, when compared with the FA counterpart. These findings concluded that folate deficiency induced TL instability in both telomerase-negative and -positive cells, and FA was more efficient in maintaining TL and chromosome stability compared with 5-MeTHF.

Effects of folate on telomere length and chromosome stability of human fibroblasts and melanoma cells in vitro: a comparison of folic acid and 5-methyltetrahydrofolate.

Telomere length (TL), which is maintained by human telomerase reverse transcriptase (hTERT; component of telomerase) and/or TRF1/TRF2 (core components of shelterin) via different mechanisms, is essential for chromosomal stability and cell survival. Folates comprise a group of essential B9 vitamin that involve in DNA synthesis and methylation. This study aimed to evaluate the effects of folic acid (FA) and 5-methyltetrahydrofolate (5-MeTHF) on TL, chromosome stability, and cell survival of telomerase-negative BJ and telomerase-positive A375 cells in vitro. BJ and A375 cells were cultured in modified medium with FA or 5-MeTHF (22.6 or 2260 nM) for 28 days. TL and mRNA expression were determined by RT-qPCR. Chromosome instability (CIN) and cell death were measured by CBMN-Cyt assay. Results showed that abnormal TL elongation was observed in FA and 5-MeTHF deficient BJ cells. The TL of A375 cells showed no obvious alterations under the FA-deficient condition but was significantly elongated under the 5-MeTHF-deficient condition. In both BJ and A375 cells, FA and 5-MeTHF deficiency caused decreased TRF1, TRF2, and hTERT expression, increased CIN and cell death; while a high concentration of 5-MeTHF induced elongated TL, elevated CIN, increased TRF1 and TRF2 expression and decreased hTERT expression, when compared with the FA counterpart. These findings concluded that folate deficiency induced TL instability in both telomerase-negative and -positive cells, and FA was more efficient in maintaining TL and chromosome stability compared with 5-MeTHF.

Effects of dietary restriction on genome stability are sex and feeding regimen dependent.

Preserving genome stability is essential to prevent aging and cancer. Dietary restriction (DR) is the most reproducible non-pharmacological way to improve health and extend lifespan in various species. Whether DR helps to preserve genome stability and whether this effect is altered by experimental variables remain unclear. Moreover, DR research relies heavily on experimental animals, making the development of reliable in vitro mimetics of great interest. Therefore, we tested the effects of sex and feeding regimen (time-restricted eating, alternate day fasting and calorie restriction) on genome stability in CF-1 mice and whether these effects can be recapitulated by cell culture paradigms. Here, we show that calorie restriction significantly decreases the spontaneous micronuclei (MN), a biomarker of genome instability, in bone marrow cells of females instead of males. Alternate day fasting significantly decreases cisplatin-induced MN in females instead of males. Unexpectedly, daily time-restricted eating significantly exacerbates cisplatin-induced MN in males but not in females. Additionally, we design several culture paradigms that are able to faithfully recapitulate the key effects of these DR regimens on genome stability. In particular, 30% reduction of serum, a mimetic of calorie restriction, exhibits a strong ability to decrease spontaneous and cisplatin-induced MN in immortalized human umbilical vein endothelial cells. We conclude that the effects of different DR regimens on genome stability are not universal and females from each diet regimen sustain a more stable genome than males. Our results provide novel insight into the understanding of how DR influences genome stability in a sex and regimen dependent way, and suggest that our in vitro DR mimetics could be adopted to study the underlying molecular mechanisms.

Interplay of cGAS with micronuclei: Regulation and diseases.

In higher eukaryotes, sophisticate regulation of genome function requires all chromosomes to be packed into a single nucleus. Micronucleus (MN), the dissociative nucleus-like structure frequently observed in aging and multiple disease settings, has critical, yet under-recognized, pathophysiological functions. Micronuclei (MNi) have recently emerged as major sources of cytosolic DNA that can activate the cGAS-STING axis in a cell-intrinsic manner. However, MNi induced from different genotoxic stressors display great heterogeneity in binding or activating cGAS and the signaling responses downstream of the MN-induced cGAS-STING axis have divergent outcomes including autoimmunity, autoinflammation, metastasis, or cell death. Thus, full characterization of molecular network underpinning the interplay of cGAS and MN is important to elucidate the pathophysiological roles of immunogenic MN and design improved drugs that selectively target cancer via boosting the MN-derived cGAS-STING axis. Here, we summarize our current understanding of the mechanisms for self-DNA discrimination by cGAS. We focus on discussing how MN immunogencity is dictated by multiple mechanisms including integrity of micronuclear envelope, state of nucleosome and DNA, competitive factors, damaged mitochondrial DNA and micronucleophagy. We also describe emerging links between immunogenic MN and human diseases including cancer, neurodegenerative diseases and COVID-19. Particularly, we explore the exciting concept of inducing immunogenic MN as a therapeutic approach in treating cancer. We propose a new theoretical framework to describe immunogenic MN as a biological sensor to modulate cellular processes in response to genotoxic stress and provide perspectives on developing novel experimental approaches to unravel the complexity of MN immunogenicity regulation and immunogenic MN pathophysiology.

MicroRNA-22-3p and MicroRNA-149-5p Inhibit Human Hepatocellular Carcinoma Cell Growth and Metastasis Properties by Regulating Methylenetetrahydrofolate Reductase.

microRNAs are small endogenous noncoding RNAs that have emerged as key negative regulators that target gene expression through RISC. Our previous study showed that the methylenetetrahydrofolate reductase gene (MTHFR) plays a key role in one carbon metabolism, which is downregulated by miR-22-3p and miR-149-5p, and that it could exert a potential anti-cancer effect. Whether miR-22-3p/miR-149-5p can regulate MTHFR to exert anti-cancer effects has become the focus of our research. Normal (HL-7702 cells) and cancerous (QGY-7703/HepG2 cells) human hepatocellular cells were transfected with 100 nM hsa-miR-22-3p/hsa-miR-149-5p mimic or controls. After 24, 48, and 72 h, cell proliferation ability was tested using CCK-8. The changes in MTHFR expression at both the transcriptional and translational levels were determined by RT-qPCR and Western blotting, respectively. Cancerous cell invasion and migration ability were confirmed by means of a transwell assay. We found that ectopic miR-22-3p/miR-149-5p inhibits hepatocellular carcinoma cell proliferation but does not inhibit normal human hepatocyte proliferation. The transfection of ectopic miR-22-3p/miR-149-5p downregulated the MTHFR expression in QGY-7703 and HepG2 but not in HL-7702. QGY-7703 and HepG2 migration and invasion were inhibited by ectopic miR-22-3p/miR-149-5p. Additionally, we found that ectopic miR-22-3p/miR-149-5p significantly increased the expression of TP53INP1 and PDCD4 in QGY-7703. The results of the study suggest that miRNA-22-3p and miRNA-149-5p inhibit tumor growth and metastasis properties may be by regulating MTHFR and that they exert anticancer effects in hepatocellular carcinoma cells.

High-dose metformin induces a low-glucose dependent genotoxic stress.

Epidemiological studies have demonstrated that metformin (a cornerstone of diabetes treatment) has anticancer activity, but the underlying mechanism remains elusive. We aimed to investigate whether metformin elicits anticancer activity via increasing genotoxic stress, a state of increased genome damage that becomes tumor-suppressing if it goes beyond an intolerable threshold. We found that metformin (1-16 mM) suppressed proliferation and colony formation in a panel of cancer cell lines (HeLa, A375, A549 and QGY). Metformin induced a dose-dependent increase of genotoxic stress (including micronucleus, nucleoplasmic bridge and nuclear bud) and the increase of genotoxic stress correlated well with metformin's anticancer potential. Metformin deregulated the expression of BUBR1 and MAD2, two core genes of spindle assembly checkpoint (SAC) that surveillances chromosome segregation. Metformin had weakened antiproliferative effect and a corresponding attenuated genotoxic effect in HeLa cells cultured in high glucose (16 mg/ml). Meanwhile, metformin significantly increased genotoxicity in non-cancer cells (NCM460 and HUVECs). Metformin became non-genotoxic to HUVECs in high-glucose (8 and 16 mg/ml) conditions and reduced the genotoxicity of high glucose. Overall, these results infer a new mechanism of high-dose metformin, whereby low-glucose dependent genotoxic stress derived from SAC dysfunction might mediate some of the anticancer effect of this drug.

A comprehensive study of the genotoxic and anti-genotoxic effects of homocysteine in HUVECs and mouse bone marrow cells.

Elevated Homocysteine (Hcy) is associated with increased risk of vascular disease, but whether it induces genotoxicity to vascular endothelial cells remains unknown. Here, we conducted a comprehensive study of the genotoxicity, and unexpected anti-genotoxicity, of Hcy by cytokinesis-blocked micronucleus assay in HUVECs and erythrocyte micronucleus test in mouse bone marrow cells. Our experiments led to several important findings. First, while supraphysiological Hcy (SP-Hcy) exhibited remarkable genotoxicity, physiologically-relevant Hcy (PR-Hcy) reduced the basal genotoxicity. Second, among the metabolites of Hcy, cysteine phenocopied the anti-genotoxicity of PR-Hcy and, methionine, S-adenosylhomocysteine and H2S phenocopied the genotoxicity of SP-Hcy. Third, the genotoxicity of SP-Hcy was mitigated by vitamin B6, Fe2+ and Cu2+, but was exacerbated by N-acetylcysteine. Fourth, under pre-, co- or post-treatment protocol, both SP-Hcy and PR-Hcy attenuated the genotoxicity of cisplatin, mitomycin-C, nocodazole or deoxycholate. Finally, 100 and 250 mg/kg Hcy ameliorated cisplatin-induced genotoxicity in bone marrow cells of CF-1 and Kunming mice. Our results suggest that genotoxicity may be one mechanism through which Hcy confers an increased risk for vascular disease, but more importantly, they challenge the long-standing paradigm that Hcy is always harmful to human health. Our study calls for a more systematic effort in understanding the molecular mechanisms underlying the anti-genotoxicity of Hcy.

Decoding and rejuvenating human ageing genomes: Lessons from mosaic chromosomal alterations.

One of the most curious findings emerged from genome-wide studies over the last decade was that genetic mosaicism is a dominant feature of human ageing genomes. The clonal dominance of genetic mosaicism occurs preceding the physiological and physical ageing and associates with propensity for diseases including cancer, Alzheimer's disease, cardiovascular disease and diabetes. These findings are revolutionizing the ways biologists thinking about health and disease pathogenesis. Among all mosaic mutations in ageing genomes, mosaic chromosomal alterations (mCAs) have the most significant functional consequences because they can produce intercellular genomic variations simultaneously involving dozens to hundreds or even thousands genes, and therefore have most profound effects in human ageing and disease etiology. Here, we provide a comprehensive picture of the landscapes, causes, consequences and rejuvenation of mCAs at multiple scales, from cell to human population, by reviewing data from cytogenetic, genetic and genomic studies in cells, animal models (fly and mouse) and, more frequently, large-cohort populations. A detailed decoding of ageing genomes with a focus on mCAs may yield important insights into the genomic architecture of human ageing, accelerate the risk stratification of age-related diseases (particularly cancers) and development of novel targets and strategies for delaying or rejuvenating human (genome) ageing.

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.

Small but strong: Mutational and functional landscapes of micronuclei in cancer genomes.

Micronuclei, small spatially-separated, nucleus-like structures, are a common feature of human cancer cells. There are considerable heterogeneities in the sources, structures and genetic activities of micronuclei. Accumulating evidence suggests that micronuclei and main nuclei represent separate entities with respect to DNA replication, DNA damage sensing and repairing capacity because micronuclei are not monitored by the same checkpoints nor covered by the same nuclear envelope as the main nuclei. Thus, micronuclei are spatially restricted "mutation factories." Several large-scale DNA sequencing and bioinformatics studies over the last few years have revealed that most micronuclei display a mutational signature of chromothripsis immediately after their generation and the underlying molecular mechanisms have been dissected extensively. Clonal expansion of the micronucleated cells is context-dependent and is associated with chromothripsis and several other mutational signatures including extrachromosomal circular DNA, kataegis and chromoanasynthesis. These results suggest what was once thought to be merely a passive indicator of chromosomal instability is now being recognized as a strong mutator phenotype that may drive intratumoral genetic heterogeneity. Herein, we revisit the actionable determinants that contribute to the bursts of mutagenesis in micronuclei and present the growing number of evidence which suggests that micronuclei have distinct short- and long-term mutational and functional effects to cancer genomes. We also pose challenges for studying the long-term effects of micronucleation in the upcoming years.

Short-term in vitro glutamine restriction differentially impacts the chromosomal stability of transformed and non-transformed cells.

Glutamine (Gln) is a non-essential amino acid central for generating building blocks and cellular energy in tumours and rapidly proliferating non-transformed cells. However, the influence of Gln on regulating chromosomal stability of transformed and non-transformed cells remain poorly understand. We hypothesised that Gln is required for maintaining a homeostatic level of chromosomal stability. To this end, transformed cells HeLa and A375 and non-transformed cells NCM460 and HUVEC cells were intervened with varying concentrations of Gln (10, 1, 0.1 and 0.01 mM), with or without cisplatin (0.1 µg/ml), for 24 h. The cytokinesis-block micronucleus (MN) assay was used to determine chromosomal instability (CIN), the extent of which is reflected by the frequency of MN, nucleoplasmic bridge (NPB) and nuclear bud (NB). We demonstrated an unexpected decrease in the spontaneous rate of MN, but not NPB and NB, after Gln restriction in HeLa and A375 cells. Gln restriction reduced cisplatin-induced MN, but not NPB and NB, in HeLa and A375 cells. We further revealed that Gln restriction suppressed the proliferation of HeLa cells with high CIN induced by nocodazole, partially explaining why Gln restriction decreased the frequency of spontaneous and cisplatin-induced MN in transformed cells. In contrast, Gln restriction increased MN and NB, but not NPB, in NCM460 cells. In HUVEC cells, Gln restriction increased MN, NPB and NB. Meanwhile, Gln restriction sensitised NCM460 cells to cisplatin-induced genotoxicity. A similar but more pronounced pattern was observed in HUVEC cells. Collectively, these results suggest that the in vitro influences of Gln metabolism on CIN depend on cellular contexts: Transformed cells require high Gln to fine tune their CIN in an optimal rate to maximise genomic heterogeneity and fitness, whereas non-transformed cells need high Gln to prevent CIN.

Understanding the birth of rupture-prone and irreparable micronuclei.

Micronuclei are extra-nuclear bodies mainly derived from ana-telophase lagging chromosomes/chromatins (LCs) that are not incorporated into primary nuclei at mitotic exit. Unlike primary nuclei, most micronuclei are enclosed by nuclear envelope (NE) that is highly susceptible to spontaneous and irreparable rupture. Ruptured micronuclei act as triggers of chromothripsis-like chaotic chromosomal rearrangements and cGAS-mediated innate immunity and inflammation, raising the view that micronuclei play active roles in human aging and tumorigenesis. Thus, understanding the ways in which micronuclear envelope (mNE) goes awry acquires increased importance. Here, we review the data to present a general framework for this question. We firstly describe NE reassembly after mitosis and NE repair during interphase. Simultaneously, we briefly discuss how mNE is organized and how mNE rupture controls the fate of micronuclei and micronucleated cells. As a focus of this review, we highlight current knowledge about why mNE is rupture-prone and irreparable. For this, we survey observations from a series of elegant studies to provide a systematic overview. We conclude that the birth of rupture-prone and irreparable micronuclei may be the cumulative effects of their intracellular geographic origins, biophysical properties, and specific mNE features. We propose that DNA damage and immunogenicity in micronuclei increase stepwise from altered mNE components, mNE rupture, and refractory to repair. Throughout our discussion, we note interesting issues in mNE fragility that have yet to be resolved.

High homocysteine promotes telomere dysfunction and chromosomal instability in human neuroblastoma SH-SY5Y cells.

Telomeres, specialized structures at the ends of linear chromosomes, protect chromosome ends from degradation, recombination, and mis-repair. Critically short telomere length (TL) may result in chromosome instability (CIN), causing tumor promotion and, at higher levels, cell death and tumor suppression. Homocysteine (Hcy) is a sulfur-containing amino acid involved in one-carbon metabolism. Elevated plasma Hcy is a cancer risk factor. Human SH-SY5Y neuroblastoma cells were treated with pathophysiological concentrations of Hcy (15-120 µM) for 14 and 28 days. The cytokinesis-block micronucleus cytome assay was used to determine cytostasis (nuclear division index, NDI), cell death (apoptosis and necrosis), and CIN (micronuclei, nucleoplasmic bridges, and nuclear buds in binucleated cells). Quantitative PCR was used to measure TL and the expression of hTERT, the gene encoding the catalytic subunit of telomerase for TL elongation. The results showed that Hcy induced elongation of TL and fluctuating changes in expression of hTERT. TL elongation was associated with increased CIN. Hcy decreased the NDI and increased cell death. This study shows that there is cross-talk between Hcy and TL in tumor cells and supports the concept that high Hcy inhibits cell division and promotes the death of tumor cells by abnormal elongation of TL and elevation of CIN.

Aqueous extract of bulbus Fritillaria cirrhosa induces cytokinesis failure by blocking furrow ingression in human colon epithelial NCM460 cells.

Bulbus Fritillariacirrhosa D. Don (BFC) has been widely used as an herbal medicament for respiratory diseases in China for over 2000 years. The ethnomedicinal effects of BFC have been scientifically verified, nevertheless its toxicity has not been completely studied. Previously, we have reported that the aqueous extract of BFC induces mitotic aberrations and chromosomal instability (CIN) in human colon epithelial NCM460 cells via dysfunctioning the mitotic checkpoint. Here, we extend this study and specifically focus on the influence of BFC on cytokinesis, the final step of cell division. One remarkable change in NCM460 cells following BFC treatment is the high incidence of binucleated cells (BNCs). More detailed investigation of the ana-telophases reveals that furrow ingression, the first stage of cytokinesis, is inhibited by BFC. Asynchronous cultures treatment demonstrates that furrow ingression defects induced by BFCs are highly associated with the formation of BNCs in ensuing interphase, indicating the BNCs phenotype after BFC treatment was resulted from cytokinesis failure. In line with this, the expression of genes involved in the regulation of furrow ingression is significantly de-regulated by BFC (e.g., LATS-1/2 and Aurora-B are upregulated, and YB-1 is downregulated). Furthermore, long-term treatment of BFC elucidates that the BNCs phenotype is transient and the loss of BNCs is associated with increased frequency of micronuclei and nuclear buds, two biomarkers of CIN. In supporting of these findings, the Nin Jiom Pei Pa Koa and Chuanbei Pipa Gao, two commercially available Chinese traditional medicines containing BFC, are able to induce multinucleation and CIN in NCM460 cells. Altogether, these data provide the first in vitro experimental evidence linking BFC to cytokinesis failure and suggest the resultant BNCs may be intermediates to produce CIN progenies.

Mosaic loss of human Y chromosome: what, how and why.

Y chromosome (ChrY), the male-specific sex chromosome, has been considered as a genetic wasteland. Aging-related mosaic loss of ChrY (LOY) has been known for more than half a century, but it was constantly considered as a neutral karyotype related to normal aging. These views have been challenged with genome-wide association studies identifying mosaic LOY in human somatic cells is the most commonly acquired mutation in male's genome and is associated with a wide spectrum of human diseases including cancer, Alzheimer's disease, and cardiovascular disease. These previously undescribed clinical significances deeply modify our perception on ChrY and open up a range of new questions. Here, we review the latest advances in our knowledge of the biological origins and clinical consequences of mosaic LOY. We highlight the association of mosaic LOY to pathogenic conditions and evaluate the cause-and-consequence relationships between mosaic LOY and pathogenesis. The known risk factors of mosaic LOY including age, genetic variants, ChrY structural aberrations and environmental stressors are discussed. In light of evidence from pioneering and more recent studies, we propose the micronucleation hypothesis and centromere-dysfunction and telomere-attrition models to explain how mosaic LOY occurs and why ChrY is prone to lose. We believe it is importantly and timely to extend mosaic LOY research from epidemiological associations to mechanistic studies. In this regard, we outline important gaps and assess several future directions from a biological and clinical perspective. An improved understanding of mosaic LOY will open new pathways to modify and increase healthy aging in males.

The molecular origins and pathophysiological consequences of micronuclei: New insights into an age-old problem.

Micronuclei (MN), the small nucleus-like bodies separated from the primary nucleus, can exist in cells with numerical and/or structural chromosomal aberrations in apparently normal tissues and more so in tumors in humans. While MN have been observed for over 100 years, they were merely and constantly considered as passive indicators of chromosome instability (CIN) for a long time. Relatively little is known about the molecular origins and biological consequences of MN. Rapid technological advances are helping to close these gaps. Very recent studies provide exciting evidence that MN act as key platform for chromothripsis and a trigger of innate immune response, suggesting that MN could affect cellular functions by both genetic and nongenetic means. These previously unappreciated findings have reawakened widespread interests in MN. In this review, the diverse mechanisms leading to MN generation and the complex fate profiles of MN are discussed, together with the evidence for their contribution to CIN, inflammation, senescence and cell death. Moreover, we put this knowledge together into a speculative perspective on how MN may be responsible for cancer development and how their presence may influence the choice of treatment. We suggest that the heterogeneous responses to MN may function physiological to ensure the arrestment, elimination and immune clearance of damaged cells, but pathologically, may enable the survival and oncogenic transformation of cells bearing CIN. These insights not only underscore the complexity of MN biology, but also raise a host of new questions and provide fertile ground for future research.

High concentration of sugars is genotoxic to folate-deficient cells.

Patients with type 2 diabetes mellitus (T2DM) are associated with an elevated, but poorly understood baseline of genomic instability (GIN). Expert panels are still debating on whether hyperglycemia is the key element in conferring this high GIN. Since high blood glucose and low blood folate are prevalent in T2DM, we hypothesized that high glucose may work with low folate to induce GIN. Using NCM460, CCD841 and L02 cell lines as in vitro cell models, we investigated the genotoxic effects of high sugars (HS; 1-2% glucose, fructose, galactose or sucrose) alone or in combination with folate deficiency (23 nM, FD) over a course of 7 days by the cytokinesis block micronucleus assay. We found that HS is nongenotoxic to NCM460, CCD841 and L02 cells. However, the combination of HS and FD induced significantly higher levels of micronuclei, nucleoplasmic bridges and nuclear buds. Our in vitro work demonstrates that HS is non-genotoxic under folate repletive condition, but is genotoxic under FD condition. These results provide preclinal proof of concept that concomitant hyperglycemia and low folate may explain, at least in part, the high baseline of GIN in T2DM patients, suggesting that folate levels should be kept under control in order to limit the risk of GIN and carcinogenesis in T2DM.

Geraniin Differentially Modulates Chromosome Stability of Colon Cancer and Noncancerous Cells by Oppositely Regulating their Spindle Assembly Checkpoint.

Geraniin has been reported to specifically induce apoptosis in multiple human cancers, but the underlying mechanism is poorly defined. The spindle assembly checkpoint (SAC) is a surveillance system to ensure high-fidelity chromosome segregation during mitosis. Weakening of SAC to enhance chromosome instability (CIN) can be therapeutic because very high levels of CIN are lethal. In this study, we have investigated the effects of geraniin on the SAC of colorectal cancer HCT116 cells and noncancerous colon epithelial CCD841 cells. We find that treatment of HCT116 cells with geraniin leads to dose-dependent decrease of cell proliferation, colony formation, and anchorage-independent growth. Geraniin is found to induce apoptosis in mitotic and postmitotic HCT116 cells. Furthermore, geraniin weakens the SAC function of HCT116 cells by decreasing the transcriptional expression of several SAC kinases (particularly Mad2 and Bub1), which in turn leads to premature anaphase entry, mitotic aberrations, and CIN in HCT116 cells. In contrast, the proliferation of CCD841 cells is slightly inhibited by geraniin. Even more interestingly, geraniin increases the transcriptional expression of several SAC kinases (e.g., Mad1 and BubR1) to strengthen SAC efficiency, which contributes to the reduction of mitotic aberrations and CIN in CCD841 cells. Altogether, our findings reveal that the SAC pathway in human colon cancer and noncancerous cell lineages responses oppositely to geraniin treatment, resulting CIN promotion and suppression, respectively. Specific abrogation of SAC to induce catastrophic CIN in HCT116 cells may account for the selective anticancer action of geraniin.. Environ. Mol. Mutagen. 60:254-268, 2019. © 2018 Wiley Periodicals, Inc.