Aneuploidy In Cancer Cells Research Articles

Abstract PR008: Targeting mechanisms of dosage compensation to selectively kill aneuploid cancer cells

Abstract Aneuploidy is an abnormal chromosome composition and a general hallmark of human cancer. Aneuploidy causes detrimental cellular stresses, but cancer cells evolve to cope with these stresses. Consequently, targeting such mitigation mechanisms is a promising potential therapeutic strategy. As an abnormal dosage of gene products from altered chromosomes can cause RNA and proteotoxic stress, dosage compensation (DC) of imbalanced gene products was reported to mitigate these stresses in aneuploid cells. However, the mechanisms that regulate DC remain elusive. To address these mechanisms, we focused on the role(s) of stress granules (SGs) and RNA binding proteins (RBPs) in aneuploid cancer cells. Our recent study revealed that aneuploid cancer cells preferentially depend on RNA and protein metabolism, and need to attenuate translation in order to cope with proteotoxic stress (Ippolito & Zerbib et al. bioRxiv 2023). In yeast, it has been previously reported that Ssd1, one of the RBPs localized in P-bodies, is indispensable to tolerating aneuploidy stress. Based on these findings, we set out to explore SGs as potential regulators of gene expression in aneuploid cancer cells. As expected, we revealed that SGs emerged in cells under acute aneuploidy stress induced by chromosome mis-segregation. These results imply that SGs are formed in cells during and right after aneuploidization, potentially as a way to mediate DC and ameliorate aneuploidy-induced cellular stress. To gain further insight into RNA regulation in aneuploid cells, we analyzed the essentiality of RBPs across cancer cell lines. We found that the RNA-editing enzyme ADAR, a suppressor of SG formation, is preferentially essential in aneuploid cancer cells. Remarkably, ADAR disruption synergized with acute aneuploidy stress to induce SGs, and ADAR exhibited increased RNA editing activity following chromosome mis-segregation. Our results suggest that SGs and their suppressor ADAR might contribute to ameliorating acute aneuploidy-induced stress. We are currently investigating the target RNAs regulated by SGs and ADAR and examining their functional role(s) in DC, with the goal of uncovering potential synthetic lethalities associated with aneuploidy in cancer cells. Citation Format: Hajime Okada, Eran Sdeor, Miriam Karmon, Erez Levanon, Uri Ben-David. Targeting mechanisms of dosage compensation to selectively kill aneuploid cancer cells [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Expanding and Translating Cancer Synthetic Vulnerabilities; 2024 Jun 10-13; Montreal, Quebec, Canada. Philadelphia (PA): AACR; Mol Cancer Ther 2024;23(6 Suppl):Abstract nr PR008.

Diagnostic Accuracy of Flow Cytometric DNA Index in Saudi Children with B Cell Acute Lymphoblastic Leukemia.

B cell Acute Lymphoblastic Leukemia (B-ALL) is one of the most common types of cancer diagnosed in children in Saudi Arabia. Cytogenetic investigations, including karyotyping and FISH, are used to determine the incidence and prognostic significance of chromosomal abnormalities in B-ALL. However, in ALL, accurate identification of the morphology of chromosomes is sometimes not achieved. Flow cytometric DI may have the advantage of being technically fast, using either fresh or frozen samples to correctly stratify the patient into the appropriate risk group for treatment. In this study, we evaluated the reliability and validity of using fixed samples instead of fresh samples to determine aneuploidy in cancer cells using a DNA index. The results of the DNA index obtained by flow cytometry were compared with those of conventional cytogenetic analysis to validate the accuracy. Fixed samples (n = 72) from children diagnosed with B-ALL at King Fahad Medical City in Riyadh between 2017 and 2019 were investigated. The results showed strong and statistically significant positive correlation between DNAI-FCM and conventional cytogenetic analysis (p = 0.000 < 0.01). The DNA index value by flow cytometry was proportional to the cytogenetic study in 94.36% (67) of the cases, while discrepancy was observed in 5.6% (four) cases. Our findings highlight the ability of the DNA index method to provide complementary information for the accurate diagnosis of aneuploidy in patients with B-ALL.

294 Identification of MCAK Inhibitors that Induce Aneuploidy in Triple Negative Breast Cancer Models

OBJECTIVES/GOALS: Microtubule poisons, like Taxol, are used to treat triple negative breast cancer (TNBC) and may induce lethal aneuploidy in cancer cells. Patients initially respond, but often develop drug resistance. New targeted drugs that cause aneuploidy may be a valuable approach to therapy. One potential target is the Kinesin 13 MCAK, which limits aneuploidy. METHODS/STUDY POPULATION: TCGA and GSE47561 databases were probed for MCAK expression, and data was stratified by subtype and survival statistics. Knockdown studies were performed to test whether MCAK knockdown sensitizes cells to taxanes for cell proliferation and for induction of aneuploidy. FRET and image-based screens were used to identify MCAK inhibitors from small molecule inhibitor libraries. Inhibitors were then tested for functional effects in multiple cell-based assays and for clonal growth in colony formation assays. RESULTS/ANTICIPATED RESULTS: MCAK expression is upregulated in TNBC and associated with reduced overall survival. Knockdown of MCAK caused a two-to-five-fold reduction of the IC50 for Taxol in cancer cell lines, with no change in normal cell lines. Taxol treatment or MCAK knockdown increased aneuploidy induction, with no additive effect between the two. Our small molecule screen identified three putative MCAK inhibitors, which induced aneuploidy in both taxane-sensitive and taxane-resistant cells. These inhibitors also reduced clonogenic growth, and the most potent inhibitor, C4, caused an approximate five-fold reduction in the IC50 for Taxol in cell proliferation assays. DISCUSSION/SIGNIFICANCE: MCAK can serve as a biomarker of breast cancer prognosis. MCAK knockdown or inhibition sensitizes cancer cells to Taxol without affecting normal cells, making it a potential target in combination therapy. MCAK inhibitors also reduce growth as single agents in taxane resistant lines, giving them potential use as therapies in resistant disease.

Mitochondrial RNA methyltransferase TRMT61B is a new, potential biomarker and therapeutic target for highly aneuploid cancers.

Despite being frequently observed in cancer cells, chromosomal instability (CIN) and its immediate consequence, aneuploidy, trigger adverse effects on cellular homeostasis that need to be overcome by anti-stress mechanisms. As such, these safeguard responses represent a tumor-specific Achilles heel, since CIN and aneuploidy are rarely observed in normal cells. Recent data have revealed that epitranscriptomic marks catalyzed by RNA-modifying enzymes change under various stress insults. However, whether aneuploidy is associated with such RNA modifying pathways remains to be determined. Through an in silico search for aneuploidy biomarkers in cancer cells, we found TRMT61B, a mitochondrial RNA methyltransferase enzyme, to be associated with high levels of aneuploidy. Accordingly, TRMT61B protein levels are increased in tumor cell lines with an imbalanced karyotype as well as in different tumor types when compared to control tissues. Interestingly, while TRMT61B depletion induces senescence in melanoma cell lines with low levels of aneuploidy, it leads to apoptosis in cells with high levels. The therapeutic potential of these results was further validated by targeting TRMT61B in transwell and xenografts assays. We show that TRM61B depletion reduces the expression of several mitochondrial encoded proteins and limits mitochondrial function. Taken together, these results identify a new biomarker of aneuploidy in cancer cells that could potentially be used to selectively target highly aneuploid tumors.

Cell cycle regulation of ER membrane biogenesis protects against chromosome missegregation.

Failure to reorganize the endoplasmic reticulum (ER) in mitosis results in chromosome missegregation. Here, we show that accurate chromosome segregation in human cells requires cell cycle-regulated ER membrane production. Excess ER membranes increase the viscosity of the mitotic cytoplasm to physically restrict chromosome movements, which impedes the correction of mitotic errors leading to the formation of micronuclei. Mechanistically, we demonstrate that the protein phosphatase CTDNEP1 counteracts mTOR kinase to establish a dephosphorylated pool of the phosphatidic acid phosphatase lipin 1 in interphase. CTDNEP1 control of lipin 1 limits the synthesis of fatty acids for ER membrane biogenesis in interphase that then protects against chromosome missegregation in mitosis. Thus, regulation of ER size can dictate the biophysical properties of mitotic cells, providing an explanation for why ER reorganization is necessary for mitotic fidelity. Our data further suggest that dysregulated lipid metabolism is a potential source of aneuploidy in cancer cells.

A CTDNEP 1-Lipin 1-mTOR Regulatory Network Restricts ER Membrane Biogenesis to Enable Chromosome Motions Necessary for&amp;nbsp;Mitotic Fidelity

The endoplasmic reticulum (ER) dramatically restructures in open mitosis to become excluded from the mitotic spindle; however, the significance of ER reorganization to mitotic progression is not known. Here, we demonstrate that limiting ER membrane biogenesis enables mitotic chromosome movements necessary for chromosome biorientation and prevention of micronuclei formation. Aberrantly expanded ER membranes increase the effective viscosity of the mitotic cytoplasm to physically restrict chromosome dynamics – slowed chromosome motions impede correction of mitotic errors induced by transient disassembly, leading to severe micronucleation. We define the mechanistic link between regulation of ER membrane biogenesis and mitotic fidelity by demonstrating that a CTDNEP1-lipin 1-mTOR regulatory network limits ER lipid synthesis to prevent chromosome missegregation. Together, this work shows that ER membranes reorganize in mitosis to enable chromosome movements necessary for mitotic error correction and reveal dysregulated lipid metabolism as a potential source of aneuploidy in cancer cells. 

Defective Nuclear Lamina in Aneuploidy and Carcinogenesis.

Aneuploidy, loss or gain of whole chromosomes, is a prominent feature of carcinomas, and is generally considered to play an important role in the initiation and progression of cancer. In high-grade serous ovarian cancer, the only common gene aberration is the p53 point mutation, though extensive genomic perturbation is common due to severe aneuploidy, which presents as a deviant karyotype. Several mechanisms for the development of aneuploidy in cancer cells have been recognized, including chromosomal non-disjunction during mitosis, centrosome amplification, and more recently, nuclear envelope rupture at interphase. Many cancer types including ovarian cancer have lost or reduced expression of Lamin A/C, a structural component of the lamina matrix that underlies the nuclear envelope in differentiated cells. Several recent studies suggest that a nuclear lamina defect caused by the loss or reduction of Lamin A/C leads to failure in cytokinesis and formation of tetraploid cells, transient nuclear envelope rupture, and formation of nuclear protrusions and micronuclei during the cell cycle gap phase. Thus, loss and reduction of Lamin A/C underlies the two common features of cancer—aberrations in nuclear morphology and aneuploidy. We discuss here and emphasize the newly recognized mechanism of chromosomal instability due to the rupture of a defective nuclear lamina, which may account for the rapid genomic changes in carcinogenesis.

A centrosomal route for cancer genome instability.

Despite the widespread occurrence of aneuploidy in cancer cells, the molecular causes for chromosomal instability are not well established. Cyclin B2 is now shown to control a pathway - involving the centrosomal kinases aurora A and Plk1 and the tumour suppressor p53 - the alteration of which causes defective centrosome separation, aneuploidy and tumour development.

STAG2 expression in oral cancer and potentially malignant lesions

Oral cancer is a world health problem, and one of the highest incidence rates of oral cancer worldwide occurs in Brazil. STAG2 is part of the cohesin complex which is responsible for sister chromatid cohesion. STAG2 loss of expression was reported in a range of tumors, and STAG2 loss was found to cause chromosomal instability and aneuploidy in cancer cells. On the basis of these findings, we investigated STAG2 expression in oral cancer and potentially malignant lesions. We investigated STAG2 immunoexpression in oral cancer, lip cancer, oral leukoplakia, and actinic cheilitis, including complete clinical information. Normal oral mucosa samples were included as normal controls. STAG2 protein was highly expressed in all samples. We further tested STAG2 expression in gastric adenocarcinomas and glioblastomas, as these tumor types were previously shown to lose STAG2 expression. We found homogenous expression of STAG2 by these tumor cells. Our results suggest that STAG2 loss of expression is not a common event in oral carcinogenesis.

Elevated Tolerance to Aneuploidy in Cancer Cells: Estimating the Fitness Effects of Chromosome Number Alterations by In Silico Modelling of Somatic Genome Evolution

An unbalanced chromosome number (aneuploidy) is present in most malignant tumours and has been attributed to mitotic mis-segregation of chromosomes. However, recent studies have shown a relatively high rate of chromosomal mis-segregation also in non-neoplastic human cells, while the frequency of aneuploid cells remains low throughout life in most normal tissues. This implies that newly formed aneuploid cells are subject to negative selection in healthy tissues and that attenuation of this selection could contribute to aneuploidy in cancer. To test this, we modelled cellular growth as discrete time branching processes, during which chromosome gains and losses were generated and their host cells subjected to selection pressures of various magnitudes. We then assessed experimentally the frequency of chromosomal mis-segregation as well as the prevalence of aneuploid cells in human non-neoplastic cells and in cancer cells. Integrating these data into our models allowed estimation of the fitness reduction resulting from a single chromosome copy number change to an average of ≈30% in normal cells. In comparison, cancer cells showed an average fitness reduction of only 6% (p = 0.0008), indicative of aneuploidy tolerance. Simulations based on the combined presence of chromosomal mis-segregation and aneuploidy tolerance reproduced distributions of chromosome aberrations in >400 cancer cases with higher fidelity than models based on chromosomal mis-segregation alone. Reverse engineering of aneuploid cancer cell development in silico predicted that aneuploidy intolerance is a stronger limiting factor for clonal expansion of aneuploid cells than chromosomal mis-segregation rate. In conclusion, our findings indicate that not only an elevated chromosomal mis-segregation rate, but also a generalised tolerance to novel chromosomal imbalances contribute to the genomic landscape of human tumours.

Abstract B16: Cells containing mutations in the cohesin component, STAG2, are sensitive to PARP inhibition

Abstract Synthetic lethality (SL) has been proposed as a strategy to specifically target cells harboring cancer mutations while leaving unmutated, non-cancer cells unaffected, thus minimizing drug side effects. One genetic vulnerability common to many types of cancer is chromosome instability (or CIN). CIN can lead to increased genetic mutation and aneuploidy in cancer cells thereby distinguishing them from their normal neighbors and making it a possible candidate phenotype to target by SL. Here, we focus on the multifunctional cohesin complex that is critical for accurate chromosome segregation and genome stability because it tethers sister chromatids together after DNA replication and maintains cohesion until their separation in anaphase. Although several subunits of cohesin have been shown to be mutated in tumors, recent data identifies a cohesin component, STAG2 (Stromal Antigen 2 or SA-2) as a highly mutated gene in several types of cancer including Ewing's sarcoma, melanoma and glioblastomas (GBMs). As a previous study in our lab had shown that knockdown of any one of the core cohesion subunits SMC1A, SMC3 or RAD21 can render cells sensitive to the poly ADP-ribose polymerase (PARP) inhibitor olaparib, we sought to determine if cell lines harboring cancer-specific STAG2 mutations showed similar sensitivity. Using paired GBM cell lines containing either a truncated STAG2 or wild-type STAG2 knock-in, we found that STAG2 mutation status was, indeed, associated with significantly decreased proliferation in the presence of PARP inhibition. Interestingly, olaparib treatment led to an accumulation of cells in the G2 phase of the cell cycle and an increase in DNA damage markers. Furthermore, in the presence of increasing concentrations of olaparib, a higher percentage of STAG2-mutated cells had micronuclei and fragmented nuclei compared to their wild-type STAG2 knock-in counterparts. Taken together, these data suggest that the DNA repair enzyme PARP may be a potential therapeutic SL target for tumors harboring mutations in STAG2. Citation Format: Melanie L. Bailey, Nigel J. O'Neil, Derek M. van Pel, Phil Hieter. Cells containing mutations in the cohesin component, STAG2, are sensitive to PARP inhibition. [abstract]. In: Proceedings of the AACR Precision Medicine Series: Synthetic Lethal Approaches to Cancer Vulnerabilities; May 17-20, 2013; Bellevue, WA. Philadelphia (PA): AACR; Mol Cancer Ther 2013;12(5 Suppl):Abstract nr B16.

Abstract LB-97: Aurora kinase inhibition suppresses colon cancer cell growth through NF-κb-mediated PUMA induction.

Abstract Aurora kinases are a group of highly conserved protein kinases that play a key role in mitosis. It has been shown that aurora kinases are overexpressed in a variety of tumors, and their overexpression contributes to aneuploidy in cancer cells. Inhibitors of aurora kinases have been developed and showed promises in recent studies. However, the mechanisms by which aurora kinase inhibitors suppress tumor cell growth have remained unclear. In this study, we found that ZM-447439, an aurora B inhibitor that has been tested in a number of preclinical studies, suppressed colon cancer cell growth by inducing apoptosis through PUMA, a p53 downstream target and a BH3-only Bcl-2 family protein. Treatment with ZM-447439 strongly induced PUMA in a variety of colon cancer cells irrespective of their p53 status. The induction of PUMA by ZM-447439 is mediated by IκB-dependent activation of NF-κB, which directly binds to the PUMA promoter to activate its transcription. Deficiency in PUMA abrogated ZM-447439-induced apoptosis and caspase activation, and rendered ZM-447439 resistance in vitro and in vivo. Furthermore, chemosensitization by ZM-447439 was also found to be PUMA-dependent. Together, these results demonstrate a key role of PUMA-dependent apoptosis in mediating the therapeutic effect of aurora kinase inhibition. They provide a rationale for manipulating the apoptotic machinery to improve sensitivity and overcome resistance to aurora kinase inhibitors. Citation Format: Jing Sun, Kan He, Jian Yu, Lin Zhang. Aurora kinase inhibition suppresses colon cancer cell growth through NF-κb-mediated PUMA induction. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr LB-97. doi:10.1158/1538-7445.AM2013-LB-97

Integrative Functional Genomics Analysis of Sustained Polyploidy Phenotypes in Breast Cancer Cells Identifies an Oncogenic Profile for GINS2

Aneuploidy is among the most obvious differences between normal and cancer cells. However, mechanisms contributing to development and maintenance of aneuploid cell growth are diverse and incompletely understood. Functional genomics analyses have shown that aneuploidy in cancer cells is correlated with diffuse gene expression signatures and aneuploidy can arise by a variety of mechanisms, including cytokinesis failures, DNA endoreplication, and possibly through polyploid intermediate states. To identify molecular processes contributing to development of aneuploidy, we used a cell spot microarray technique to identify genes inducing polyploidy and/or allowing maintenance of polyploid cell growth in breast cancer cells. Of 5760 human genes screened, 177 were found to induce severe DNA content alterations on prolonged transient silencing. Association with response to DNA damage stimulus and DNA repair was found to be the most enriched cellular processes among the candidate genes. Functional validation analysis of these genes highlighted GINS2 as the highest ranking candidate inducing polyploidy, accumulation of endogenous DNA damage, and impairing cell proliferation on inhibition. The cell growth inhibition and induction of polyploidy by suppression of GINS2 was verified in a panel of breast cancer cell lines. Bioinformatic analysis of published gene expression and DNA copy number studies of clinical breast tumors suggested GINS2 to be associated with the aggressive characteristics of a subgroup of breast cancers in vivo. In addition, nuclear GINS2 protein levels distinguished actively proliferating cancer cells suggesting potential use of GINS2 staining as a biomarker of cell proliferation as well as a potential therapeutic target.

Depletion of the oncoprotein Bcl-3 induces centrosome amplification and aneuploidy in cancer cells

Bcl-3 is an atypical member of the inhibitor of NF-kappa B family of proteins since it can function as a coactivator of transcription. Although this oncogene was described in leukemia, it is overexpressed in a number of solid tumors as well. The oncogenic potential of Bcl-3 has been associated with its capacity to increase proliferation by means of activating the cyclin D1 promoter and to its antiapoptotic role mediated by the inhibiton of p53 activity. In the course of dissecting these properties, we found that depleting Bcl-3 protein using shRNAs induce a decrease of proliferation and clonogenic survival associated with the induction of multinucleation and increased ploidy. These effects were associated with a DNA damage response, a delay in G2/M checkpoint and the induction of centrosome amplification

Oxidative stress in cancer associated fibroblasts drives tumor-stroma co-evolution

Loss of stromal fibroblast caveolin-1 (Cav-1) is a powerful single independent predictor of poor prognosis in human breast cancer patients, and is associated with early tumor recurrence, lymph node metastasis, and tamoxifen-resistance. We developed a novel co-culture system to understand the mechanism(s) by which a loss of stromal fibroblast Cav-1 induces a "lethal tumor micro-environment". Here, we propose a new paradigm to explain the powerful prognostic value of stromal Cav-1. In this model, cancer cells induce oxidative stress in cancer associated fibroblasts, which then acts as a "metabolic" and "mutagenic" motor to drive tumor-stroma co-evolution, DNA damage, and aneuploidy in cancer cells. More specifically, we show that an acute loss of Cav-1 expression leads to mitochondrial dysfunction, oxidative stress, and aerobic glycolysis in cancer associated fibroblasts. Also, we propose that defective mitochondria are removed from cancer-associated fibroblasts by autophagy/mitophagy that is induced by oxidative stress. As a consequence, cancer associated fibroblasts provide nutrients (such as lactate) to stimulate mitochondrial biogenesis and oxidative metabolism in adjacent cancer cells (the "Reverse Warburg Effect"). We provide evidence that oxidative stress in cancer associated fibroblasts is sufficient to induce genomic instability in adjacent cancer cells, via a bystander effect, potentially increasing their aggressive behavior. Finally, we directly demonstrate that nitric oxide (NO) over-production, secondary to Cav-1 loss, is the root cause for mitochondrial dysfunction in cancer associated fibroblasts. In support of this notion, treatment with anti-oxidants (such as N-acetyl-cysteine, metformin, and quercetin), or NO inhibitors (L-NAME) was sufficient to reverse many of the cancer-associated fibroblast phenotypes that we describe. Thus, cancer cells use "oxidative stress" in adjacent fibroblasts i) as an "engine" to fuel their own survival via the stromal production of nutrients, and ii) to drive their own mutagenic evolution towards a more aggressive phenotype, by promoting genomic instability. We also present evidence that the "field effect" in cancer biology could also be related to the stromal production of ROS and NO species. eNOS-expressing fibroblasts have the ability to down-regulate Cav-1 and induce mitochondrial dysfunction in adjacent fibroblasts that do not express eNOS. As such, the effects of stromal oxidative stress can be laterally propagated, amplified, and are effectively "contagious"-spread from cell-to-cell like a virus-creating an "oncogenic/mutagenic" field promoting widespread DNA damage.

Aurora Kinase Inhibitors - Rising Stars in Cancer Therapeutics?

Standard therapeutic approaches of cytotoxics and radiation in cancer are not only highly toxic, but also of limited efficacy in treatment of a significant number of cancer patients. The molecular analysis of the cancer genomes have shown a remarkable complexity and pointed to key genomic and epigenomic alterations in cancer. These discoveries are paving the way for targeted therapy approaches. However, although there are a large number of potential targets, only a few can regulate key cellular functions and intersect multiple signaling networks. The Aurora kinase family members (A, B, and C) are a collection of highly related and conserved serine-threonine kinases that fulfill these criteria, being key regulators of mitosis and multiple signaling pathways. Alterations in Aurora kinase signaling are associated with mitotic errors and have been closely linked to chromosomal aneuploidy in cancer cells. Several studies have shown amplification and/or overexpression of Aurora kinase A and B in hematologic malignancies and solid tumors. Over the past several years, Aurora kinases have become attractive targets. Several ongoing clinical trials and bench-based research are assessing the unique therapeutic potential of Aurora-based targeted therapy.

Nuclear Receptor-Induced Chromosomal Proximity and DNA Breaks Underlie Specific Translocations in Cancer

Chromosomal translocations are a hallmark of leukemia/lymphoma and also appear in solid tumors, but the underlying mechanism remains elusive. By establishing a cellular model that mimics the relative frequency of authentic translocation events without proliferation selection, we report mechanisms of nuclear receptor-dependent tumor translocations. Intronic binding of liganded androgen receptor (AR) first juxtaposes translocation loci by triggering intra- and interchromosomal interactions. AR then promotes site-specific DNA double-stranded breaks (DSBs) at translocation loci by recruiting two types of enzymatic activities induced by genotoxic stress and liganded AR, including activation-induced cytidine deaminase and the LINE-1 repeat-encoded ORF2 endonuclease. These enzymes synergistically generate site-selective DSBs at juxtaposed translocation loci that are ligated by nonhomologous end joining pathway for specific translocations. Our data suggest that the confluence of two parallel pathways initiated by liganded nuclear receptor and genotoxic stress underlies nonrandom tumor translocations, which may function in many types of tumors and pathological processes.

The Role of p53 in Silica-Induced Cellular and Molecular Responses Associated with Carcinogenesis

Crystalline silica (silica), a suspected human carcinogen, produces an increase in reactive oxygen species (ROS) when fractured using mechanical tools used in several occupations. Although ROS has been linked to apoptosis, DNA damage, and carcinogenesis, the role of enhanced ROS production by silica in silica-induced carcinogenesis is not completely understood. The goal of this study was to compare freshly fractured and aged silica-induced molecular alterations in human immortalized/transformed bronchial epithelial cells (BEAS-IIB) and lung cancer cells with altered (H460) or deficient (H1299) p53 expression. Exposure to freshly fractured or aged silica produced divergent cellular responses in certain downstream cellular events, including ROS production, apoptosis, cell cycle and chromosomal changes, and gene expression. ROS production increased significantly following exposure to freshly fractured silica compared to aged silica in BEAS-IIB and H460 cells. Apoptosis showed a comparable enhanced level of induction with freshly fractured or aged silica in both cancer lines with p53 functional changes. p53 protein was present in the BEAS-IIB and was absent in cancer cell lines after silica exposure. Exposure to freshly fractured silica also resulted in a rise in aneuploidy in cancer cells with a significantly greater increase in p53-deficient cells. Cytogenetic analysis demonstrated increased metaphase spreads, chromosome breakage, rearrangements, and endoreduplication in both cancer cells. These results suggest that altered and deficient p53 affects the cellular response to freshly fractured silica exposure, and thereby enhances susceptibility and augments cell proliferation and lung cancer development.

Aurora B expression directly correlates with prostate cancer malignancy and influence prostate cell proliferation

Chromosomal instability is one of the most common features of prostate cancer (PC), especially in advanced stages. Recent studies suggest that defects in mitotic checkpoints play a role in carcinogenesis. Lack of mitotic regulation induces aneuploidy in cancer cells acting thereafter as a driving force for malignant progression. Serine/threonine protein kinases of the Aurora genes family play an important throughout the entire cell cycle. In that Aurora B regulates chromosome segregation by ensuring the orientation of sister chromatids. As a consequence, the overexpression of Aurora B in diploid human cells NHDF induces the appearance of multinucleate cells. Archive samples of normal and neoplastic prostate tissue, and prostate derived cell lines were screened for the expression of Aurora B. Immunohistochemical analysis showed increased nuclear expression of Aurora-B in high Gleason grade PCs respect to low and intermediate grade cases and in all cancers in respect to hyperplastic and normal glands. Furthermore, in the high Gleason grade anaplastic cancer tissues Aurora B expression was accompanied by the phosphorylation of the histone H3. In analogy to the in vivo situation, Aurora B was vigorously expressed in the androgen independent PC cell lines PC3 and DU145, while a very modest expression of the kinase was observed in the androgen sensitive LnCap cells and in the EPN cells, a line of epithelial cells derived from normal prostate tissue. In addition, in PC3 cells Aurora B expression is accompanied the by the phosphorylation of the histone H3. The block of Aurora B expression induced by an inhibitor of Aurora kinase activity significantly reduced the growth of prostate carcinoma cells, but not that of non-transformed EPN cells. Our data are the first demonstration of a role of Aurora B in PC progression. In addition, the observation that Aurora B specific inhibitors interfere with PC cell proliferation but not with that of non-transformed prostate epithelial cells suggest that Aurora B is a potential therapeutic target for PC.

Aurora B Overexpression Associates with the Thyroid Carcinoma Undifferentiated Phenotype and Is Required for Thyroid Carcinoma Cell Proliferation

Alterations in chromosome number (aneuploidy) are common in human neoplasias. Loss of mitotic regulation is believed to induce aneuploidy in cancer cells and act as a driving force during the malignant progression. The serine/theronine protein kinases of aurora family genes play a critical role in the regulation of key cell cycle processes. Aurora B mediates chromosome segregation by ensuring orientation of sister chromatids and overexpression of Aurora B in diploid human cells NHDF (normal human diploid fibroblast) induces multinuclearity. We analyzed Aurora B expression in human thyroid carcinomas. Cell lines originating from different histotypes showed an increase in Aurora B expression. Immunohistochemical analysis of archive samples showed a high expression of Aurora B in anaplastic thyroid carcinomas; conversely, Aurora B expression was not detectable in normal thyroid tissue. Real-time PCR analysis confirmed a strong expression of Aurora B in anaplastic thyroid carcinomas. The block of Aurora B expression induced by RNA interference or by using an inhibitor of Aurora kinase activity significantly reduced the growth of thyroid anaplastic carcinoma cells.