Centrosome aberrations and chromosome instability contribute to tumorigenesis and intratumor heterogeneity

Centrosomes serve as the major microtubule organizing centers in cells and thereby contribute to cell shape,polarity,and motility.Also,centrosomes ensure equal chromosome segregation during mitosis.Centrosome aberrations arise when the centrosome cycle is deregulated,or as a result of cytokinesis failure.A long-standing postulate is that centrosome aberrations are involved in the initiation and progression of cancer.However,this notion has been a subject of controversy because until recently the relationship has been correlative.Recently,it was shown that numerical or structural centrosome aberrations can initiate tumors in certain tissues in mice,as well as invasion.Particularly,we will focus on centrosome amplification and chromosome instability as drivers of intra-tumor heterogeneity and their consequences in cancer.We will also discuss briefly the controversies surrounding this theory to highlight the fact that the role of both centrosome amplification and chromosome instability in cancer is highly context-dependent.Further,we will discuss single-cell sequencing as a novel technique to understand intra-tumor heterogeneity and some therapeutic approaches to target chromosome instability.

Microsatellite instability and MLH1 promoter hypermethylation in colorectal cancer

Colorectal cancer （CRC） is caused by a series of genetic or epigenetic changes, and in the last decade there has been an increased awareness that there are multiple forms of colorectal cancer that develop through different pathways. Microsatellite instability is involved in the genesis of about 15% of sporadic colorectal cancers and most of hereditary nonpolyposis cancers. Tumors with a high frequency of microsatellite instability tend to be diploid, to possess a mucinous histology, and to have a surrounding lymphoid reaction. They are more prevalent in the proximal colon and have a fast pass from polyp to cancer. Nevertheless, they are associated with longer survival than stage-matched tumors with microsateUite stability. Resistance of colorectal cancers with a high frequency of microsatellite instability to 5-fluorouracilbased chemotherapy is well established. Silencing the MLH1 gene expression by its promoter methylation stops the formation of MLH1 protein, and prevents the normal activation of the DNA repair gene. This is an important cause for genomic instability and cell proliferation to the point of colorectal cancer formation. Better knowledge of this process will have a huge impact on colorectal cancer management, prevention, treatment and prognosis.

Role of chromosomal instability and clonal heterogeneity in the therapy response of breast cancer cell lines

Objective:Chromosomal instability(CIN)is a hallmark of cancer characterized by cell-to-cell variability in the number or structure of chromosomes,frequently observed in cancer cell populations and is associated with poor prognosis,metastasis,and therapeutic resistance.Breast cancer(BC)is characterized by unstable karyotypes and recent reports have indicated that CIN may influence the response of BC to chemotherapy regimens.However,paradoxical associations between extreme CIN and improved outcome have been observed.Methods:This study aimed to 1)evaluate CIN levels and clonal heterogeneity(CH)in MCF7,ZR-751,MDA-MB468,BT474,and KPL4 BC cells treated with low doses of tamoxifen(TAM),docetaxel(DOC),doxorubicin(DOX),Herceptin(HT),and combined treatments(TAM/DOC,TAM/DOX,TAM/HT,HT/DOC,and HT/DOX)by using fluorescence in situ hybridization(FISH),and 2)examine the association with response to treatments by comparing FISH results with cell proliferation.Results:Intermediate CIN was linked to drug sensitivity according to three characteristics:estrogen receptorα(ERα)and HER2 status,pre-existing CIN level in cancer cells,and the CIN induced by the treatments.ERα+/HER2-cells with intermediate CIN were sensitive to treatment with taxanes(DOC)and anthracyclines(DOX),while ERα-/HER2-,ERα+/HER2+,and ERα-/HER2+cells with intermediate CIN were resistant to these treatments.Conclusions:A greater understanding of CIN and CH in BC could assist in the optimization of existing therapeutic regimens and/or in supporting new strategies to improve cancer outcomes.

Evidence of increased chromosomal instability in infertile males after exposure to mitomycin C and caffeine

Aim： To evaluate the genetic instability of 11 fertile and 25 infertile men. Methods： The methodology of sister chromatid exchanges （SCEs） was applied to cultures of peripheral blood lymphocytes, and the levels of SCEss were analyzed as a quantitative index of genotoxicity, along with the values of the mitotic index （MI） and the proliferation rate index （PRI） as qualitative indices of cytotoxicity and cytostaticity, respectively. The genotoxic and antineoplastic agent, mitomycin C （MMC）, and caffeine （CAF） - both well-known inhibitors of DNA repair mechanism - were used in an attempt to induce chromosomal instability in infertile men, so as to more easily detect the probable underlying damage on DNA. Results： Our experiments illustrated that infertile men, compared with fertile ones, demonstrated a statistically significant DNA instability in peripheral blood lymphocytes after being exposed simultaneously to MMC and CAF. Conclusion： The current study showed vividly that there was genetic instability in infertile men which probably contributes to the development of an impaired reproductive capacity. （Asian JAndro12006 Mar; 8： 199-204）

Genetic Predisposition to Retinoblastoma (Rb)

Determination of 8 cytogenetic indicators in 14 cases of Rb,their 21 parents and 14 normal controls revealed various degrees ofchromosome instability and nondisjunction in the patients and their parents,indicating the presence of genetic neoplastic predisposition to neoplasm inRb patients.Eye Science 1993;9:149-152.

Genetic alterations in hepatocellular carcinoma: An update

Hepatocellular carcinoma(HCC) is one of the leading causes of cancer-related deaths worldwide. Although recent advances in therapeutic approaches for treating HCC have improved the prognoses of patients with HCC, this cancer is still associated with a poor survival rate mainly due to late diagnosis. Therefore, a diagnosis must be made sufficiently early to perform curative and effective treatments. There is a need for a deeper understanding of the molecular mechanisms underlying the initiation and progression of HCC because these mechanisms are critical for making early diagnoses and developing novel therapeutic strategies. Over the past decade, much progress has been made in elucidating the molecular mechanisms underlying hepatocarcinogenesis. In particular, recent advances in next-generation sequencing technologies have revealed numerous genetic alterations, including recurrently mutated genes and dysregulated signaling pathways in HCC. A better understanding of the genetic alterations in HCC could contribute to identifying potential driver mutations and discovering novel therapeutic targets in the future. In this article, we summarize the current advances in research on the genetic alterations, including genomic instability, single-nucleotide polymorphisms, somatic mutations and deregulated signaling pathways, implicated in the initiation and progression of HCC. We also attempt to elucidate some of the genetic mechanisms that contribute to making early diagnoses of and developing molecularly targeted therapies for HCC.

Molecular alterations in gastric cancer with special reference to the early-onset subtype

Currently, gastric cancer(GC) is one of the most frequently diagnosed neoplasms, with a global burden of 723000 deaths in 2012. It is the third leading cause of cancer-related death worldwide. There are numerous possible factors that stimulate the procarcinogenic activity of important genes. These factors include genetic susceptibility expressed in a singlenucleotide polymorphism, various acquired mutations(chromosomal instability, microsatellite instability, somatic gene mutations, epigenetic alterations) and environmental circumstances(e.g., helicobcter pylori infection, EBV infection, diet, and smoking). Most of the aforementioned pathways overlap, and authors agree that a clear-cut pathway for GC may not exist. Thus, the categorization of carcinogenic events is complicated. Lately, it has been claimed that research on early-onset gastric carcinoma(EOGC) and hereditary GC may contribute towards unravelling some part of the mystery of the GC molecular pattern because young patients are less exposed to environmental carcinogens and because carcinogenesis in this setting may be more dependent on genetic factors. The comparison of various aspects that differ and coexist in EOGCs and conventional GCs might enable scientists to: distinguish which features in the pathway of gastric carcinogenesisare modifiable, discover specific GC markers and identify a specific target. This review provides a summary of the data published thus far concerning the molecular characteristics of GC and highlights the outstanding features of EOGC.

DNA end binding activity and Ku70/80 heterodimer expression in human colorectal tumor

AIM： TO determine the DNA binding activity and protein levels of the Ku70/80 heterodimer, the functional mediator of the NHEJ activity, in human colorectal carcinogenesis. METHODS： The Ku70/80 DNA-binding activity was determined by electrophoretic mobility shift assays in 20 colon adenoma and 15 colorectal cancer samples as well as matched normal colonic tissues. Nuclear and cytoplasmic protein expression was determined by immunohistochemistry and Western blot analysis. RESULTS： A statistical found in both adenomas y significant difference was and carcinomas as compared to matched normal colonic mucosa （P〈0.00）. However, changes in binding activity were not homogenous with approximately 50% of the tumors showing a clear increase in the binding activity, 30% displaying a modest increase and 15% showing a decrease of the activity.Tumors, with increased DNA-binding activity, also showed a statistically significant increase in Ku70 and Ku86 nuclear expression, as determined by Western blot and immunohistochemical analyses （P〈0.001）. Cytoplasmic protein expression was found in pathological samples, but not in normal tissues either from tumor patients or from healthy subjects. CONCLUSION： Overall, our DNA-binding activity and protein level are consistent with a substantial activation of the NHEJ pathway in colorectal tumors. Since the NHEJ is an error prone mechanism, its abnormal activation can result in chromosomal instability and ultimately lead to tumorigenesis.

Early-onset colorectal cancer:A separate subset of colorectal cancer

Colorectal cancer(CRC)has a great impact on the world population.With increasing frequency,CRC is described according to the presenting phenotype,based on its molecular characteristics.Classification of CRC tumors according to their genetic and/or epigenetic alterations is not only important for establishing the molecular bases of the disease,but also for predicting patient outcomes and developing more individualized treatments.Early-onset CRC is a heterogeneous disease,with a strong familial component,although the disease is sporadic in an important proportion of cases.Different molecular alterations appear to contribute to the apparent heterogeneity of the early-onset population and subgroups can be distinguished with distinct histopathologic and familial characteristics.Moreover,compared with late-onset CRC,there are characteristicsthat suggest that early-onset CRC may have a different molecular basis.The purpose of this review was to analyze the current state of knowledge about earlyonset CRC with respect to clinicopathologic,familial and molecular features.Together,these features make it increasingly clear that this subset of CRC may be a separate disease,although it has much in common with late-onset CRC.

Multiple primary colorectal cancer: Individual or familial predisposition?

Colorectal carcinoma(CRC) is one of the most frequent cancers. Along the surface of the large bowel, several foci of CRC may appear simultaneously or over the time. The development of at least two different tumours has been defined as multiple primary CRC(MPCRC):When more than one tumour is diagnosed at the same time, it is known as synchronous CRC(SCRC), while when a second neoplasm is diagnosed some time after the resection and/or diagnosis of the first lesion, it is called metachronous CRC(MCRC). Multiple issues can promote the development of MPCRC, ranging from different personal factors, such as environmental exposure, to familial predisposition due to hereditary factors. However, most studies do not distinguish this dichotomy. High- and low-pentrance genetic variants are involved in MPCRC. An increased risk for MPCRC has been described in Lynch syndrome, familial adenomatous polyposis, and serrated polyposis. Non-syndromic familial CRCs should also be considered as risk factors for MPCRC. Environmental factors can promote damage to colon mucosae that enable the concurrence of MPCRC. Epigenetics are thought to play a major role in the carcinogenesis of sporadic MPCRC. The methylation state of the DNA depends on multiple environmental factors(e.g., smoking and eating foods cooked at high temperatures), and this can contribute to increasing the MPCRC rate. Certain clinical features may also suggest individual predisposition for MPCRC. Different etiopathogenic factors are suspected to be involved in SCRC and MCRC, and different familial vs individual factors may be implicated. MCRC seems to follow a familial pattern, whereas individual factors are more important in SCRC. Further studies must be carried out to know the molecular basis of risks for MPCRC in order to modify, if necessary, its clinical management, especially from a preventive point of view.

Colorectal cancer carcinogenesis:a review of mechanisms

Colorectal cancer(CRC) is the second most common cancer in women and the third most common in men globally. CRC arises from one or a combination of chromosomal instability, Cp G island methylator phenotype, and microsatellite instability. Genetic instability is usually caused by aneuploidy and loss of heterozygosity. Mutations in the tumor suppressor or cell cycle genes may also lead to cellular transformation. Similarly, epigenetic and/or genetic alterations resulting in impaired cellular pathways, such as DNA repair mechanism, may lead to microsatellite instability and mutator phenotype. Non-coding RNAs, more importantly micro RNAs and long non-coding RNAs have also been implicated at various CRC stages. Understanding the specific mechanisms of tumorigenesis and the underlying genetic and epigenetic traits is critical in comprehending the disease phenotype. This paper reviews these mechanisms along with the roles of various non-coding RNAs in CRCs.

The more the messier：centrosome amplification as a novel biomarker for personalized treatment of colorectal cancers

Colon cancer is currently the third most common cancer and second most fatal cancer in the United States,resulting in approximately 600,000 deaths annually.Though colorectal cancer death rates are decreasing by about 3%every year,disease outcomes could be substantially improved with more research into the drivers of colon carcinogenesis,the determinants of aggressiveness in colorectal cancer and the identification of biomarkers that could enable choice of more optimal treatments.Colon carcinogenesis is notably a slow process that can take decades.Known factors that contribute to the development of colon cancer are mutational,epigenetic and environmental,and risk factors include age,history of polyps and family history of colon cancer.Colorectal cancers exhibit heterogeneity in their features and are often characterized by the presence of chromosomal instability,microscopic satellite instability,or CpG island methylator phenotype.In this review,we propose that centrosome amplification may be a widespread occurrence in colorectal cancers and could potently influence tumor biology.Moreover,the quantitation of this cancer-specific anomaly could offer valuable prognostic information and pave the way for further customization of treatment based on the organellar profile of patients.Patient stratification models that take into account centrosomal status could thus potentially reduce adverse side effects and result in improved outcomes for colorectal cancer patients.

Genomic dissection of gastrointestinal and lung neuroendocrine neoplasm

Objective:Neuroendocrine neoplasms(NENs)are relatively rare and heterogeneous malignancies with two major subtypes:low-grade neuroendocrine tumor(NET)and high-grade neuroendocrine carcinoma(NEC).Comprehensive molecular characterization of NENs is needed to refine our understanding of the biological underpinnings of different NEN subtypes and to predict disease progression more accurately.Methods:We performed whole-exome sequencing(WES)of NEN samples from 49 patients(25 NETs and 24 NECs)arising from the stomach,intestines or lung.Clinicopathologic features were assessed and associated with molecular events.Results:NENs generally harbor a low mutation burden,with TP53 being the top mutated gene found in 31%of patients.Consistent with other studies,p53 signaling pathway dysfunction is significantly enriched in NECs compared to NETs(P<0.01).Other than TP53,tissue type-specific mutation profiles of NENs were observed in our cohort compared to those reported in pancreatic NETs.Importantly,we observed significant genomic instability,with increased copy number alterations observed across the NEN genome,which was more profound in NECs and independently correlated with poor overall survival(OS)(P<0.001).NECs could be further stratified into two molecular subtypes based on OS(P<0.001)and the chromosomal instability score(CIS).Interestingly,we discovered that the gain of whole chromosome 5 occurred at the early stage of NEN development,followed by the loss of 5 q exclusively in NECs(P<0.001).Conclusions:These findings provide novel insights into the molecular characteristics of NENs and highlight the association of genomic stability with clinical outcomes.

Rescue of p53 functions by in vitro-transcribed mRNA impedes the growth of high-grade serous ovarian cancer

Background:The cellular tumor protein p53(TP53)is a tumor suppressor gene that is frequently mutated in human cancers.Among various cancer types,the very aggressive high-grade serous ovarian carcinoma(HGSOC)exhibits the high-est prevalence of TP53 mutations,present in>96%of cases.Despite intensive efforts to reactivate p53,no clinical drug has been approved to rescue p53 func-tion.In this study,our primary objective was to administer in vitro-transcribed(IVT)wild-type(WT)p53-mRNA to HGSOC cell lines,primary cells,and ortho-topic mouse models,with the aim of exploring its impact on inhibiting tumor growth and dissemination,both in vitro and in vivo.Methods:To restore the activity of p53,WT p53 was exogenously expressed in HGSOC cell lines using a mammalian vector system.Moreover,IVT WT p53 mRNA was delivered into different HGSOC model systems(primary cells and patient-derived organoids)using liposomes and studied for proliferation,cell cycle progression,apoptosis,colony formation,and chromosomal instabil-ity.Transcriptomic alterations induced by p53 mRNA were analyzed using RNA sequencing in OVCAR-8 and primary HGSOC cells,followed by ingenuity path-way analysis.In vivo effects on tumor growth and metastasis were studied using orthotopic xenografts and metastatic intraperitoneal mouse models.Results:Reactivation of the TP53 tumor suppressor gene was explored in differ-ent HGSOC model systems using newly designed IVT mRNA-based methods.The introduction of WT p53 mRNA triggered dose-dependent apoptosis,cell cycle arrest,and potent long-lasting inhibition of HGSOC cell proliferation.Transcriptome analysis of OVCAR-8 cells upon mRNA-based p53 reactivation revealed significant alterations in gene expression related to p53 signaling,such as apoptosis,cell cycle regulation,and DNA damage.Restoring p53 function concurrently reduces chromosomal instability within the HGSOC cells,under-scoring its crucial contribution in safeguarding genomic integrity by moderating the baseline occurrence of double-strand breaks arising from replication stress.Furthermore,in various mouse models,treatment with p53 mRNA reduced tumor growth and inhibited tumor cell dissemination in the peritoneal cavity in a dose-dependent manner.Conclusions:The IVT mRNA-based reactivation of p53 holds promise as a potential therapeutic strategy for HGSOC,providing valuable insights into the molecular mechanisms underlying p53 function and its relevance in ovarian cancer treatment.

Effects on Genome Constitution and Novel Cell Wall Formation Caused by the Addition of 5RS Rye Chromosome to Common Wheat

The cytological instability of common wheat-rye addition lines was investigated in the present study. The chromosome numbers of almost all addition lines were considerably stable, but those of CS ＋ 5R were very variable. The rye chromosome added in this line was found to be much shorter than expected. Fluorescent in situ hybridization with 5S rDNA and the centromere-speciflc probes clearly revealed that the short rye chromosome contains only a short arm of chromosome 5R （5RS）. In this line, chromosome numbers of both 5RS and common wheat were changeable. The chromosome numbers ranged from 2n = 36 to 2n = 44 in the cells carrying two 5RS, and ranged from 2n = 31 to 2n = 44 in one 5RS cells. In addition to the chromosome instability, the muIticells wrapped in a sac-like structure were frequently observed in the root meristematic tissues of CS ＋5RS after the enzyme treatment for chromosome preparation. Genomic in situ hybridization with rye DNA as a probe showed that all cells in sacs investigated were at the interphase stage and contained one or two 5RS chromosomes. An electron microscopic analysis revealed that the cells of CS＋5RS, particularly in sacs, have abnormal （irregular and curved） cell walls. These results indicate that 5RS has （a） specific factor（s） influencing the cell wall development as well as the genome stability.

The spindle assembly checkpoint:perspectives in tumorigenesis and cancer therapy

Loss or gain of chromosomes,a condition known as aneuploidy,is a common feature of tumor cells and has therefore been proposed as the driving force for tumorigenesis.Such chromosomal instability can arise during mitosis as a result of mis-segregation of the duplicated sister chromatids to the two daughter cells.In normal cells,missegregation is usually prevented by the spindle assembly checkpoint(SAC),a sophisticated surveillance mechanism that inhibits mitotic exit until all chromosomes have successfully achieved bipolar attachment to spindle microtubules.Complete abrogation of SAC activity is lethal to normal as well as to tumor cells,as a consequence of massive chromosome mis-segregation.Importantly,many human aneuploid tumor cells exhibit a weakened SAC activity that allows them to tolerate gains or losses of a small number of chromosomes;and interfering with this SAC residual activity may constitute a suitable strategy to kill cancer cells.This review focuses on the potential link between SAC and tumorigenesis,and the therapeutic strategy to target the SAC for cancer treatment.

Down-regulation of mitotic checkpoint in transformed human embryo lung fibroblasts induced by N-methyl-N'-nitro-N-nitrosoguaridine

Background Mutations in mitotic checkpoint genes have been detected in several human cancers, which exhibit chromosome instability. We wanted to know whether mutation of hBub1 could occur in transformed human embryo lung fibroblasts (HELF) cells induced by a chemical carcinogen.Methods HELF cells were transformed by N-methyl-N’-nitro-N- nitrosoguaridine (MNNG), and three flasks of transformed HELF cells (named as T1, T2, and T3) were selected as amplifiers, and mutations of hBub1 in these transformed cells were analyzed by PCR-SSCP and sequencing.Results It was found that any one of three transformed cell lines exhibited aneuploidy with a low mitotic checkpoint function. Subsequent PCR-SSCP and sequence analysis showed an AGT to CGT or ATT mutation at codon 80 in hBub1 gene in T1 cells with a resultant change in amino acid sequence.Conclusion Our study demonstrated that the mitotic checkpoint genes could be targets of MNNG.

NAT10 promotes cell proliferation by acetylating CEP170 mRNA to enhance translation efficiency in multiple myeloma

Multiple myeloma(MM) is still an incurable hematologic malignancy, which is eagerly to the discovery of novel therapeutic targets and methods. N-acetyltransferase 10(NAT10) is the first reported regulator of mRNA acetylation that is activated in many cancers. However, the function of NAT10 in MM remains unclear. We found significant upregulation of NAT10 in MM patients compared to normal plasma cells, which was also highly correlated with MM poor outcome. Further enforced NAT10 expression promoted MM growth in vitro and in vivo, while knockdown of NAT10 reversed those effects. The correlation analysis of acetylated RNA immunoprecipitation sequencing(ac RIP-seq) and ribosome profiling sequencing(Ribo-seq) combined with RIP-PCR tests identified centrosomal protein 170(CEP170) as an important downstream target of NAT10. Interfering CEP170 expression in NAT10-OE cells attenuated the acceleration of cellular growth caused by elevated NAT10. Moreover,CEP170 overexpression promoted cellular proliferation and chromosomal instability(CIN) in MM.Intriguingly, remodelin, a selective NAT10 inhibitor, suppressed MM cellular growth, induced cellular apoptosis in vitro and prolonged the survival of 5TMM3VT mice in vivo. Collectively, our data indicate that NAT10 acetylates CEP170 mRNA to enhance CEP170 translation efficiency, which suggests that NAT10 may serve as a promising therapeutic target in MM.

The Fanconi anemia pathway and DNA interstrand cross-link repair

Fanconi anemia(FA)is an autosomal or X-linked recessive disorder characterized by chromosomal instability,bone marrow failure,cancer susceptibility,and a profound sensitivity to agents that produce DNA interstrand cross-link(ICL).To date,15 genes have been identified that,when mutated,result in FA or an FA-like syndrome.It is believed that cellular resistance to DNA interstrand cross-linking agents requires all 15 FA or FAlike proteins.Here,we review our current understanding of how these FA proteins participate in ICL repair and discuss the molecular mechanisms that regulate the FA pathway to maintain genome stability.