Depression of MAD2 inhibits apoptosis and increases proliferation and multidrug resistance in gastric cancer cells by regulating the activation of phosphorylated survivin. Tumour Biol. 2010;31:225-232. [PMID: 20440596 DOI: 10.1007/s13277-010-0036-6]

Investigation of BAK, BAX and MAD2L1 gene expression in human aneuploid blastocysts

Maintaining genomic stability is crucial for normal development. At earlier stages of preimplantation development, as the embryonic genome activation is not fully completed, the embryos may be more prone to abnormalities. Aneuploidies are one of the most common genetic causes of implantation failure or first-trimester miscarriages. Apoptosis is a crucial mechanism to eliminate damaged or abnormal cells from the organism to enable healthy growth. Therefore, this study aimed to determine the relationship between the expression levels of genes involved in apoptosis in human aneuploid and euploid blastocysts. In total, 32 human embryos obtained from 21 patients were used for this study. Trophectoderm biopsies were performed and next-generation screening was carried out for aneuploidy screening. Total RNA was extracted from each blastocyst separately and cDNA was synthesized. Gene expression levels were evaluated using RT-PCR. The statistical analysis was performed to evaluate the gene expression level variations in the euploid and aneuploid embryos, respectively. The expression level of the BAX gene was significantly different between the aneuploid and euploid samples. BAX expression levels were found to be 1.5-fold lower in aneuploid cells. However, the expression levels of BAK and MAD2L1 genes were similar in each group. This study aimed to investigate the possible role of genes involved in apoptosis and aneuploidy mechanisms. The findings of this investigation revealed that the BAX gene was expressed significantly differently between aneuploid and euploid embryos. Therefore, it is possible that the genes involved in the apoptotic pathway have a role in the aneuploidy mechanism.

A New Method for Chromosomes Preparation by ATP-Competitive Inhibitor SP600125 via Enhancement of Endomitosis in Fish

Previous studies have suggested that 1,9-Pyrazoloanthrone, known as SP600125, can induce cell polyploidization. However, what is the phase of cell cycle arrest caused by SP600125 and the underlying regulation is still an interesting issue to be further addressed. Research in this article shows that SP600125 can block cell cycle progression at the prometaphase of mitosis and cause endomitosis. It is suggested that enhancement of the p53 signaling pathway and weakening of the spindle assembly checkpoint are associated with the SP600125-induced cell cycle arrest. Using preliminary SP600125 treatment, the samples of the cultured fish cells and the fish tissues display a great number of chromosome splitting phases. Summarily, SP600125 can provide a new protocol of chromosomes preparation for karyotype analysis owing to its interference with prometaphase of mitosis.

MAD2 Combined with Mitotic Spindle Apparatus (MSA) and Anticentromere Antibody (ACA) for Diagnosis of Small Cell Lung Cancer (SCLC)

BACKGROUND MAD2 is the gene controlling mitosis. Many studies have assessed MAD2 in various types of carcinoma. Antinuclear mitotic spindle apparatus antibody (MSA) and anticentromere antibody (ACA) are related mitotic antibodies, playing roles in autoimmune diseases and carcinomas, but the expression of MAD2, MSA, and ACA in SCLC is unclear. MATERIAL AND METHODS We enrolled 70 SCLC patients, 72 non-small cell lung cancer (NSCLC) patients, and 65 pulmonary nodule (PN) patients. MAD2 expression was measured through agarose electrophoresis and qt-PCR. Antinuclear mitotic spindle apparatus antibody (MSA) and anticentromere antibody (ACA) were detected by indirect immunofluorescence (IIF). RESULTS MAD2 was found both in SCLC and NSCLC. Interestingly, there was a significant difference found between SCLC and NSCLC using qt-PCR (P<0.05). The area under the ROC curve of MAD2 expression was 0.799, with medium diagnostic value. MAD2 expression was related to age, lymphatic metastasis, and survival time, but not with sex. The positivity for MSA and ACA by IIF assay were 37.20% and 34.00%, respectively, in the SCLC group, which were higher than in the NSCLC and pulmonary nodule groups (P<0.05). The kappa values of MSA and ACA with MAD2 expression were 0.73 and 0.65, respectively, with moderate consistency. Combining MAD2 with MSA and ACA enhanced the sensitivity and specificity for diagnosing SCLC. CONCLUSIONS MAD2 expression was found to be involved in carcinogenesis and prognosis of SCLC. The combination of MAD2 with MSA and ACA is useful for early diagnosis and shows promise in treatment of SCLC.

TRIP13 impairs mitotic checkpoint surveillance and is associated with poor prognosis in multiple myeloma

AAA-ATPase TRIP13 is one of the chromosome instability gene recently established in multiple myeloma (MM), the second most common and incurable hematological malignancy. However, the specific function of TRIP13 in MM is largely unknown. Using sequential gene expression profiling, we demonstrated that high TRIP13 expression levels were positively correlated with progression, disease relapse, and poor prognosis in MM patients. Overexpressing human TRIP13 in myeloma cells prompted cell growth and drug resistance, and overexpressing murine TRIP13, which shares 93% sequence identity with human TRIP13, led to colony formation of NIH/3T3 fibroblasts in vitro and tumor formation in vivo. Meanwhile, the knockdown of TRIP13 inhibited myeloma cell growth, induced cell apoptosis, and reduced tumor burden in xenograft MM mice. Mechanistically, we observed that the overexpression of TRIP13 abrogated the spindle checkpoint and induced proteasome-mediated degradation of MAD2 primarily through the Akt pathway. Thus, our results demonstrate that TRIP13 may serve as a biomarker for MM disease development and prognosis, making it a potential target for future therapies.

MAD2γ, a novel MAD2 isoform, reduces mitotic arrest and is associated with resistance in testicular germ cell tumors

Background: Prolonged mitotic arrest in response to anti-cancer chemotherapeutics, such as DNA-damaging agents, induces apoptosis, mitotic catastrophe, and senescence. Disruptions in mitotic checkpoints contribute resistance to DNA-damaging agents in cancer. MAD2 has been associated with checkpoint failure and chemotherapy response. In this study, a novel splice variant of MAD2, designated MAD2γ, was identified, and its association with the DNA damage response was investigated.

Methods: Endogenous expression of MAD2γ and full-length MAD2 (MAD2α) was measured using RT-PCR in cancer cell lines, normal foreskin fibroblasts, and tumor samples collected from patients with testicular germ cell tumors (TGCTs). A plasmid expressing MAD2γ was transfected into HCT116 cells, and its intracellular localization and checkpoint function were evaluated according to immunofluorescence and mitotic index.

Results: MAD2γ was expressed in several cancer cell lines and non-cancerous fibroblasts. Ectopically expressed MAD2γ localized to the nucleus and reduced the mitotic index, suggesting checkpoint impairment. In patients with TGCTs, the overexpression of endogenous MAD2γ, but not MAD2α, was associated with resistance to cisplatin-based chemotherapy. Likewise, cisplatin induced the overexpression of endogenous MAD2γ, but not MAD2α, in HCT116 cells.

Conclusions: Overexpression of MAD2γ may play a role in checkpoint disruption and is associated with resistance to cisplatin-based chemotherapy in TGCTs.

Helicobacter pylori infection and gastric carcinoma: Not all the strains and patients are alike

Gastric carcinoma (GC) develops in only 1%-3% of Helicobacter pylori (H. pylori) infected people. The role in GC formation of the bacterial genotypes, gene polymorphisms and host's factors may therefore be important. The risk of GC is enhanced when individuals are infected by strains expressing the oncoprotein CagA, in particular if CagA has a high number of repeats containing the EPIYA sequence in its C'-terminal variable region or particular amino acid sequences flank the EPIYA motifs. H. pylori infection triggers an inflammatory response characterised by an increased secretion of some chemokines by immunocytes and colonised gastric epithelial cells; these molecules are especially constituted by proteins composing the interleukin-1beta (IL-1β) group and tumour necrosis factor-alpha (TNF-α). Polymorphisms in the promoter regions of genes encoding these molecules, could account for high concentrations of IL-1β and TNF-α in the gastric mucosa, which may cause hypochlorhydria and eventually GC. Inconsistent results have been attained with other haplotypes of inflammatory and anti-inflammatory cytokines. Genomic mechanisms of GC development are mainly based on chromosomal or microsatellite instability (MSI) and deregulation of signalling transduction pathways. H. pylori infection may induce DNA instability and breaks of double-strand DNA in gastric mucocytes. Different H. pylori strains seem to differently increase the risk of cancer development run by the host. Certain H. pylori genotypes (such as the cagA positive) induce high degrees of chronic inflammation and determine an increase of mutagenesis rate, oxidative-stress, mismatch repair mechanisms, down-regulation of base excision and genetic instability, as well as generation of reactive oxygen species that modulate apoptosis; these phenomena may end to trigger or concur to GC development.

Multidrug-Resistance Related Long Non-Coding RNA Expression Profile Analysis of Gastric Cancer

The effect of chemotherapy of gastric cancer (GC) remains very poor because of multidrug resistance (MDR). However, the mechanisms underlying MDR of GC remains far from fully understood. The aim of this study is to illustrate the potential mechanisms of the MDR of GC at mainly the long non-coding RNA (lncRNA) level. In this study, GC cell line, SGC7901, and two MDR sublines, SGC7901/VCR and SGC7901/ADR were subjected to an lncRNA microarray analysis. Bioinformatics and verification experiments were performed to investigate the potential lncRNAs involved in the development of MDR. Pathway analysis indicated that 15 pathways corresponded to down-regulated transcripts and that 20 pathways corresponded to up-regulated transcripts (p-value cut-off is 0.05). GO analysis showed that the highest enriched GOs targeted by up-regulated transcripts were “system development” and the highest esenriched GOs targeted by the down-regulated transcripts were “sterol biosynthetic process”. Our study is the first to interrogate differentially expressed lncRNAs in human GC cell line and MDR sublines and indicates that lncRNAs are worthwhile for further study to be the novel candidate biomarkers for the clinical diagnosis of MDR and potential targets for further therapy.

Relationship between Survivin and gastric cancer

Survivin is a member of the apoptosis inhibitory protein family [inhibitor of apoptosis proteins (IAPs)] found in recent years. It is expressed in tumors and fetal tissue and closely related to tumor cell differentiation, proliferation, invasion and metastasis. Currently, functional studies reveal that survivin is directly related to invasion, metastasis, resistance to chemotherapy, angiogenesis, diagnosis and prognosis in gastric cancer. Survivin may provide a new target for early diagnosis, gene therapy and prognosis evaluation in gastric cancer. This paper reviews the structure and biological characteristics of Survivin and discuss its relationship with tumor susceptibility, treatment, diagnosis and prognosis in gastric cancer.

Disruption of FAT10-MAD2 binding inhibits tumor progression

FAT10 (HLA-F-adjacent transcript 10) is a ubiquitin-like modifier that is commonly overexpressed in various tumors. It was found to play a role in mitotic regulation through its interaction with mitotic arrest-deficient 2 (MAD2). Overexpression of FAT10 promotes tumor growth and malignancy. Here, we identified the MAD2-binding interface of FAT10 to be located on its first ubiquitin-like domain whose NMR structure thus was determined. We further proceeded to demonstrate that disruption of the FAT10-MAD2 interaction through mutation of specific MAD2-binding residues did not interfere with the interaction of FAT10 with its other known interacting partners. Significantly, ablation of the FAT10-MAD2 interaction dramatically limited the promalignant capacity of FAT10, including promoting tumor growth in vivo and inducing aneuploidy, proliferation, migration, invasion, and resistance to apoptosis in vitro. Our results strongly suggest that the interaction of FAT10 with MAD2 is a key mechanism underlying the promalignant property of FAT10 and offer prospects for the development of anticancer strategies.

Mad2 checkpoint gene silencing using epidermal growth factor receptor-targeted chitosan nanoparticles in non-small cell lung cancer model

RNA interference has emerged as a powerful strategy in cancer therapy because it allows silencing of specific genes associated with tumor progression and resistance. Mad2 is an essential mitotic checkpoint component required for accurate chromosome segregation during mitosis, and its complete abolition leads to cell death. We have developed an epidermal growth factor receptor (EGFR)-targeted chitosan system for silencing the Mad2 gene as a strategy to efficiently induce cell death in EGFR overexpressing human A549 non-small cell lung cancer cells. Control and EGFR-targeted chitosan nanoparticles loaded with small interfering RNAs (siRNAs) against Mad2 were formulated and characterized for size, charge, morphology, and encapsulation efficiency. Qualitative and quantitative intracellular uptake studies by confocal imaging and flow cytometry, respectively, showed time-dependent enhanced and selective intracellular internalization of EGFR-targeted nanoparticles compared to nontargeted system. Targeted nanoparticles showed nearly complete depletion of Mad2 expression in A549 cells contrasting with the partial depletion in the nontargeted system. Accordingly, Mad2-silencing-induced apoptotic cell death was confirmed by cytotoxicity assay and flow cytometry. Our results demonstrate that EGFR-targeted chitosan loaded with Mad2 siRNAs is a potent delivery system for selective killing of cancer cells.

Microarray analysis of cell cycle gene expression in adult human corneal endothelial cells

Corneal endothelial cells (ECs) form a monolayer that controls the hydration of the cornea and thus its transparency. Their almost nil proliferative status in humans is responsible, in several frequent diseases, for cell pool attrition that leads to irreversible corneal clouding. To screen for candidate genes involved in cell cycle arrest, we studied human ECs subjected to various environments thought to induce different proliferative profiles compared to ECs in vivo. Donor corneas (a few hours after death), organ-cultured (OC) corneas, in vitro confluent and non-confluent primary cultures, and an immortalized EC line were compared to healthy ECs retrieved in the first minutes of corneal grafts. Transcriptional profiles were compared using a cDNA array of 112 key genes of the cell cycle and analysed using Gene Ontology classification; cluster analysis and gene map presentation of the cell cycle regulation pathway were performed by GenMAPP. Results were validated using qRT-PCR on 11 selected genes. We found several transcripts of proteins implicated in cell cycle arrest and not previously reported in human ECs. Early G1-phase arrest effectors and multiple DNA damage-induced cell cycle arrest-associated transcripts were found in vivo and over-represented in OC and in vitro ECs. Though highly proliferative, immortalized ECs also exhibited overexpression of transcripts implicated in cell cycle arrest. These new effectors likely explain the stress-induced premature senescence that characterizes human adult ECs. They are potential targets for triggering and controlling EC proliferation with a view to increasing the cell pool of stored corneas or facilitating mass EC culture for bioengineered endothelial grafts.

Inhibition of Hec1 expression enhances the sensitivity of human ovarian cancer cells to paclitaxel

AIM

Hec1, a member of the Ndc80 kinetochore complex, is highly expressed in cancers. The aim of this study was to explore the role and mechanism of action of Hec1 with respect to the cytotoxicity of paclitaxel in ovarian cancer.

METHODS

Thirty ovarian cancer samples and 6 normal ovarian samples were collected. Hec1 expression in these samples was determined with immunohistochemistry. Ovarian cancer cell lines A2780, OV2008, C13K, SKOV3, and CAOV3 and A2780/Taxol were examined. Cell apoptosis and cell cycle analysis were detected with flow cytometric technique. siRNA was used to delete Hec1 in the cells. The expression of related mRNAs and proteins was measured using RT-PCR and Western blot analysis, respectively.

RESULTS

Hec1 expression was significantly higher in ovarian cancer samples than in normal ovarian samples, and was associated with paclitaxel-resistance and poor prognosis. Among the 6 ovarian cancer cell lines examined, Hec1 expression was highest in paclitaxel-resistant A2780/Taxol cells, and lowest in A2780 cells. Depleting Hec1 in A2780/Taxol cells with siRNA decreased the IC50 value of paclitaxel by more than 10-fold (from 590±26.7 to 45.6±19.4 nmol/L). Depleting Hec1 in A2780 cells had no significant effect on the paclitaxel sensitivity. In paclitaxel-treated A2780/Taxol cells, depleting Hec1 significantly increased the cleaved PARP and Bax protein levels, and decreased the Bcl-xL protein level.

CONCLUSION

Hec1 overexpression is associated with the progression and poor prognosis of ovarian cancer. Inhibition of Hec1 expression can sensitize ovarian cancer cells to paclitaxel.

The Mad1-Mad2 balancing act--a damaged spindle checkpoint in chromosome instability and cancer

Cancer cells are commonly aneuploid. The spindle checkpoint ensures accurate chromosome segregation by controlling cell cycle progression in response to aberrant microtubule-kinetochore attachment. Damage to the checkpoint, which is a partial loss or gain of checkpoint function, leads to aneuploidy during tumorigenesis. One form of damage is a change in levels of the checkpoint proteins mitotic arrest deficient 1 and 2 (Mad1 and Mad2), or in the Mad1:Mad2 ratio. Changes in Mad1 and Mad2 levels occur in human cancers, where their expression is regulated by the tumor suppressors p53 and retinoblastoma 1 (RB1). By employing a standard assay, namely the addition of a mitotic poison at mitotic entry, it has been shown that checkpoint function is normal in many cancer cells. However, in several experimental systems, it has been observed that this standard assay does not always reveal checkpoint aberrations induced by changes in Mad1 or Mad2, where excess Mad1 relative to Mad2 can lead to premature anaphase entry, and excess Mad2 can lead to a delay in entering anaphase. This Commentary highlights how changes in the levels of Mad1 and Mad2 result in a damaged spindle checkpoint, and explores how these changes cause chromosome instability that can lead to aneuploidy during tumorigenesis.

Genome-wide profiling of pluripotent cells reveals a unique molecular signature of human embryonic germ cells

Human embryonic germ cells (EGCs) provide a powerful model for identifying molecules involved in the pluripotent state when compared to their progenitors, primordial germ cells (PGCs), and other pluripotent stem cells. Microarray and Principal Component Analysis (PCA) reveals for the first time that human EGCs possess a transcription profile distinct from PGCs and other pluripotent stem cells. Validation with qRT-PCR confirms that human EGCs and PGCs express many pluripotency-associated genes but with quantifiable differences compared to pluripotent embryonic stem cells (ESCs), induced pluripotent stem cells (IPSCs), and embryonal carcinoma cells (ECCs). Analyses also identified a number of target genes that may be potentially associated with their unique pluripotent states. These include IPO7, MED7, RBM26, HSPD1, and KRAS which were upregulated in EGCs along with other pluripotent stem cells when compared to PGCs. Other potential target genes were also found which may contribute toward a primed ESC-like state. These genes were exclusively up-regulated in ESCs, IPSCs and ECCs including PARP1, CCNE1, CDK6, AURKA, MAD2L1, CCNG1, and CCNB1 which are involved in cell cycle regulation, cellular metabolism and DNA repair and replication. Gene classification analysis also confirmed that the distinguishing feature of EGCs compared to ESCs, ECCs, and IPSCs lies primarily in their genetic contribution to cellular metabolism, cell cycle, and cell adhesion. In contrast, several genes were found upregulated in PGCs which may help distinguish their unipotent state including HBA1, DMRT1, SPANXA1, and EHD2. Together, these findings provide the first glimpse into a unique genomic signature of human germ cells and pluripotent stem cells and provide genes potentially involved in defining different states of germ-line pluripotency.

Genetic aspects of gastric cancer instability

Unravelling the molecular mechanisms underlying gastric carcinogenesis is one of the major challenges in cancer genomics. Gastric cancer is a very complex and heterogeneous disease, and although much has been learned about the different genetic changes that eventually lead to its development, the detailed mechanisms still remain unclear. Malignant transformation of gastric cells is the consequence of a multistep process involving different genetic and epigenetic changes in numerous genes in combination with host genetic background and environmental factors. The majority of gastric adenocarcinomas are characterized by genetic instability, either microsatellite instability (MSI) or chromosomal instability (CIN). It is believed that chromosome destabilizations occur early in tumour progression. This review summarizes the most common genetic alterations leading to instability in sporadic gastric cancers and its consequences.

Low MAD2 expression levels associate with reduced progression-free survival in patients with high-grade serous epithelial ovarian cancer

Epithelial ovarian cancer (EOC) has an innate susceptibility to become chemoresistant. Up to 30% of patients do not respond to conventional chemotherapy [paclitaxel (Taxol®) in combination with carboplatin] and, of those who have an initial response, many patients relapse. Therefore, an understanding of the molecular mechanisms that regulate cellular chemotherapeutic responses in EOC cells has the potential to impact significantly on patient outcome. The mitotic arrest deficiency protein 2 (MAD2), is a centrally important mediator of the cellular response to paclitaxel. MAD2 immunohistochemical analysis was performed on 82 high-grade serous EOC samples. A multivariate Cox regression analysis of nuclear MAD2 IHC intensity adjusting for stage, tumour grade and optimum surgical debulking revealed that low MAD2 IHC staining intensity was significantly associated with reduced progression-free survival (PFS) (p = 0.0003), with a hazard ratio of 4.689. The in vitro analyses of five ovarian cancer cell lines demonstrated that cells with low MAD2 expression were less sensitive to paclitaxel. Furthermore, paclitaxel-induced activation of the spindle assembly checkpoint (SAC) and apoptotic cell death was abrogated in cells transfected with MAD2 siRNA. In silico analysis identified a miR-433 binding domain in the MAD2 3′ UTR, which was verified in a series of experiments. Firstly, MAD2 protein expression levels were down-regulated in pre-miR-433 transfected A2780 cells. Secondly, pre-miR-433 suppressed the activity of a reporter construct containing the 3′-UTR of MAD2. Thirdly, blocking miR-433 binding to the MAD2 3′ UTR protected MAD2 from miR-433 induced protein down-regulation. Importantly, reduced MAD2 protein expression in pre-miR-433-transfected A2780 cells rendered these cells less sensitive to paclitaxel. In conclusion, loss of MAD2 protein expression results in increased resistance to paclitaxel in EOC cells. Measuring MAD2 IHC staining intensity may predict paclitaxel responses in women presenting with high-grade serous EOC. Copyright © 2012 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Knockdown of Mad2 induces osteosarcoma cell apoptosis-involved Rad21 cleavage

BACKGROUND

Besides Mad2's role in carcinogenesis, recent study has shown that it is essential in cell survival. Here we found that knockdown of Mad2 causes osteosarcoma cell death through apoptosis, with the apoptotic signal resulting from Rad21 cleavage.

METHODS

U2OS and MG63 cells were divided into three groups: the Mad2 siRNA group, mock group and normal control group; the Mad2 siRNA group and mock group are transfected with Mad2 shRNA plasmid and mock plasmid, respectively. G418 was used to increase the transfection efficacy, which was evaluated by GFP fluorescence. Quantitative PCR and Western blotting analyses were used to detect the transcription and expression of Mad2, Rad21 and caspase-3, respectively. Flow cytometry assay using PE-labeled Annexin-V and PI, TUNEL assay and Hoechst 33258 staining were used to evaluate cell apoptosis.

RESULTS

We successfully achieved knockdown of Mad2 expression in cancer cells using RNA interference. We observed obvious apoptosis in the Mad2 siRNA group compared with the Mock and control group. We found that the apoptosis induced by Mad2 knockdown correlated with Rad21 cleavage.

CONCLUSION

These results confirmed that knockdown of Mad2 causes osteosarcoma cell death through apoptosis and provides evidence that the apoptotic signal resulted from Rad21 cleavage. This study suggested that Mad2 has potential to be a novel target for cancer therapy.