Amplification of the BCAS2 gene at chromosome 1p13.3-21 in human primary breast cancer

Molecular characterization, expression patterns and cellular localization of BCAS2 gene in male Hezuo pig

Background

Breast carcinoma amplified sequence 2 (BCAS2) participates in pre-mRNA splicing and DNA damage response, which is implicated in spermatogenesis and meiosis initiation in mouse. Nevertheless, the physiological roles of BCAS2 in the testes of large mammals especially boars remain largely unknown.

Methods

In this study, testes were collected from Hezuo pig at three development stages including 30 days old (30 d), 120 days old (120 d), and 240 days old (240 d). BCAS2 CDS region was firstly cloned using RT-PCR method, and its molecular characteristics were identified using relevant bioinformatics software. Additionally, the expression patterns and cellular localization of BCAS2 were analyzed by quantitative real-time PCR (qRT-PCR), Western blot, immunohistochemistry and immunofluorescence.

Results

The cloning and sequence analysis indicated that the Hezuo pig BCAS2 CDS fragment encompassed 678 bp open reading frame (ORF) capable of encoding 225 amino acid residues, and possessed high identities with some other mammals. The results of qRT-PCR and Western blot displayed that BCAS2 levels both mRNA and protein were age-dependent increased (p < 0.01). Additionally, immunohistochemistry and immunofluorescence results revealed that BCAS2 protein was mainly observed in nucleus of gonocytes at 30 d testes as well as nucleus of spermatogonia and Sertoli cells at 120 and 240 d testes. Accordingly, we conclude that BCAS2 is critical for testicular development and spermatogenesis of Hezuo pig, perhaps by regulating proliferation or differentiation of gonocytes, pre-mRNA splicing of spermatogonia and functional maintenance of Sertoli cells, but specific mechanism still requires be further investigated.

BCAS2 is involved in alternative mRNA splicing in spermatogonia and the transition to meiosis

Breast cancer amplified sequence 2 (BCAS2) is involved in multiple biological processes, including pre-mRNA splicing. However, the physiological roles of BCAS2 are still largely unclear. Here we report that BCAS2 is specifically enriched in spermatogonia of mouse testes. Conditional disruption of Bcas2 in male germ cells impairs spermatogenesis and leads to male mouse infertility. Although the spermatogonia appear grossly normal, spermatocytes in meiosis prophase I and meiosis events (recombination and synapsis) are rarely observed in the BCAS2-depleted testis. In BCAS2 null testis, 245 genes are altered in alternative splicing forms; at least three spermatogenesis-related genes (Dazl, Ehmt2 and Hmga1) can be verified. In addition, disruption of Bcas2 results in a significant decrease of the full-length form and an increase of the short form (lacking exon 8) of DAZL protein. Altogether, our results suggest that BCAS2 regulates alternative splicing in spermatogonia and the transition to meiosis initiation, and male fertility.

Breast cancer amplified sequence 2 (BCAS2) is involved in pre-mRNA splicing but its physiological role is unclear. Here, the authors find BCAS2 enriched in mice spermatogonia in the testes, and BCAS2 deletion in germ cells alters alternative splicing of spermatogenesis-related genes, causing male infertility.

Conditional Knockout of Breast Carcinoma Amplified Sequence 2 (BCAS2) in Mouse Forebrain Causes Dendritic Malformation via β-catenin

Breast carcinoma amplified sequence 2 (BCAS2) is a core component of the hPrP19 complex that controls RNA splicing. Here, we performed an exon array assay and showed that β-catenin is a target of BCAS2 splicing regulation. The regulation of dendrite growth and morphology by β-catenin is well documented. Therefore, we generated conditional knockout (cKO) mice to eliminate the BCAS2 expression in the forebrain to investigate the role of BCAS2 in dendrite growth. BCAS2 cKO mice showed a microcephaly-like phenotype with a reduced volume in the dentate gyrus (DG) and low levels of learning and memory, as evaluated using Morris water maze analysis and passive avoidance, respectively. Golgi staining revealed shorter dendrites, less dendritic complexity and decreased spine density in the DG of BCAS2 cKO mice. Moreover, the cKO mice displayed a short dendrite length in newborn neurons labeled by DCX, a marker of immature neurons, and BrdU incorporation. To further examine the mechanism underlying BCAS2-mediated dendritic malformation, we overexpressed β-catenin in BCAS2-depleted primary neurons and found that the dendritic growth was restored. In summary, BCAS2 is an upstream regulator of β-catenin gene expression and plays a role in dendrite growth at least partly through β-catenin.

CTNNBL1 facilitates the association of CWC15 with CDC5L and is required to maintain the abundance of the Prp19 spliceosomal complex

In order to catalyse the splicing of messenger RNA, multiple proteins and RNA components associate and dissociate in a dynamic highly choreographed process. The Prp19 complex is a conserved essential part of the splicing machinery thought to facilitate the conformational changes the spliceosome undergoes during catalysis. Dynamic protein interactions often involve highly disordered regions that are difficult to study by structural methods. Using amine crosslinking and hydrogen-deuterium exchange coupled to mass spectrometry, we describe the architecture of the Prp19 sub-complex that contains CTNNBL1. Deficiency in CTNNBL1 leads to delayed initiation of cell division and embryonic lethality. Here we show that in vitro CTNNBL1 enhances the association of CWC15 and CDC5L, both core Prp19 complex proteins and identify an overlap in the region of CDC5L that binds either CTNNBL1 or CWC15 suggesting the two proteins might exchange places in the complex. Furthermore, in vivo, CTNNBL1 is required to maintain normal levels of the Prp19 complex and to facilitate the interaction of CWC15 with CDC5L. Our results identify a chaperone function for CTNNBL1 within the essential Prp19 complex, a function required to maintain the integrity of the complex and to support efficient splicing.

Deregulation of splicing factors and breast cancer development

It is well known that many genes implicated in the development and progression of breast cancer undergo aberrant alternative splicing events to produce proteins with pro-cancer properties. These changes in alternative splicing can arise from mutations or single-nucleotide polymorphisms (SNPs) within the DNA sequences of cancer-related genes, which can strongly affect the activity of splicing factors and influence the splice site choice. However, it is important to note that absence of mutations is not sufficient to prevent misleading choices in splice site selection. There is now increasing evidence to demonstrate that the expression profile of ten splicing factors (including SRs and hnRNPs) and eight RNA-binding proteins changes in breast cancer cells compared with normal cells. These modifications strongly influence the alternative splicing pattern of many cancer-related genes despite the absence of any detrimental mutations within their DNA sequences. Thus, a comprehensive assessment of the splicing factor status in breast cancer is important to provide insights into the mechanisms that lead to breast cancer development and metastasis. Whilst most studies focus on mutations that affect alternative splicing in cancer-related genes, this review focuses on splicing factors and RNA-binding proteins that are themselves deregulated in breast cancer and implicated in cancer-related alternative splicing events.

The role of the human psoralen 4 (hPso4) protein complex in replication stress and homologous recombination

Psoralen 4 (Pso4) is an evolutionarily conserved protein that has been implicated in a variety of cellular processes including RNA splicing and resistance to agents that cause DNA interstrand cross-links. Here we show that the hPso4 complex is required for timely progression through S phase and transition through the G2/M checkpoint, and it functions in the repair of DNA lesions that arise during replication. Notably, hPso4 depletion results in delayed resumption of DNA replication after hydroxyurea-induced stalling of replication forks, reduced repair of spontaneous and hydroxyurea-induced DNA double strand breaks (DSBs), and increased sensitivity to a poly(ADP-ribose) polymerase inhibitor. Furthermore, we show that hPso4 is involved in the repair of DSBs by homologous recombination, probably by regulating the BRCA1 protein levels and the generation of single strand DNA at DSBs. Together, our results demonstrate that hPso4 participates in cell proliferation and the maintenance of genome stability by regulating homologous recombination. The involvement of hPso4 in the recombinational repair of DSBs provides an explanation for the sensitivity of Pso4-deficient cells to DNA interstrand cross-links.

ERRβ signalling through FST and BCAS2 inhibits cellular proliferation in breast cancer cells

Background:

The overexpression of oestrogen-related receptor-β (ERRβ) in breast cancer patients is correlated with improved prognosis and longer relapse-free survival, and the level of ERRβ mRNA is inversely correlated with the S-phase fraction of cells from breast cancer patients.

Methods:

Chromatin immunoprecipitation (ChIP) cloning of ERRβ transcriptional targets and gel supershift assays identified breast cancer amplified sequence 2 (BCAS2) and Follistatin (FST) as two important downstream genes that help to regulate tumourigenesis. Confocal microscopy, co-immunoprecipitation (CoIP), western blotting and quantitative real-time PCR confirmed the involvement of ERRβ in oestrogen signalling.

Results:

Overexpressed ERRβ induced FST-mediated apoptosis in breast cancer cells, and E-cadherin expression was also enhanced through upregulation of FST. However, this anti-proliferative signalling function was challenged by ERRβ-mediated BCAS2 upregulation, which inhibited FST transcription through the downregulation of β-catenin/TCF4 recruitment to the FST promoter. Interestingly, ERRβ-mediated upregulation of BCAS2 downregulated the major G1-S transition marker cyclin D1, despite the predictable oncogenic properties of BCAS2.

Interpretation:

Our study provides the first evidence that ERRβ, which is a coregulator of ERα also acts as a potential tumour-suppressor molecule in breast cancer. Our current report also provides novel insights into the entire cascade of ERRβ signalling events, which may lead to BCAS2-mediated blockage of the G1/S transition and inhibition of the epithelial to mesenchymal transition through FST-mediated regulation of E-cadherin. Importantly, matrix metalloprotease 7, which is a classical mediator of metastasis and E-cadherin cleavage, was also restricted as a result of ERRβ-mediated FST overexpression.

The PSO4 protein complex associates with replication protein A (RPA) and modulates the activation of ataxia telangiectasia-mutated and Rad3-related (ATR)

The PSO4 core complex is composed of PSO4/PRP19/SNEV, CDC5L, PLRG1, and BCAS2/SPF27. Besides its well defined functions in pre-mRNA splicing, the PSO4 complex has been shown recently to participate in the DNA damage response. However, the specific role for the PSO4 complex in the DNA damage response pathways is still not clear. Here we show that both the BCAS2 and PSO4 subunits of the PSO4 complex directly interact and colocalize with replication protein A (RPA). Depletion of BCAS2 or PSO4 impairs the recruitment of ATR-interacting protein (ATRIP) to DNA damage sites and compromises CHK1 activation and RPA2 phosphorylation. Moreover, we demonstrate that both the RPA1-binding ability of BCAS2 and the E3 ligase activity of PSO4 are required for efficient accumulation of ATRIP at DNA damage sites and the subsequent CHK1 activation and RPA2 phosphorylation. Our results suggest that the PSO4 complex functionally interacts with RPA and plays an important role in the DNA damage response.

Integrative genome-wide expression analysis bears evidence of estrogen receptor-independent transcription in heregulin-stimulated MCF-7 cells

Heregulin ß-1 (HRG) is an extracellular ligand that activates mitogen-activated protein kinase (MAPK) and phosphatidylinositol-3-OH kinase (PI3K)/Akt signaling pathways through ErbB receptors. MAPK and Akt have been shown to phosphorylate the estrogen receptor (ER) at Ser-118 and Ser-167, respectively, thereby mimicking the effects of estrogenic activity such as estrogen responsive element (ERE)-dependent transcription. In the current study, integrative analysis was performed using two tiling array platforms, comprising histone H3 lysine 9 (H3K9) acetylation and RNA mapping, together with array comparative genomic hybridization (CGH) analysis in an effort to identify HRG-regulated genes in ER-positive MCF-7 breast cancer cells. Through application of various threshold settings, 333 (326 up-regulated and 7 down-regulated) HRG-regulated genes were detected. Prediction of upstream transcription factors (TFs) and pathway analysis indicated that 21% of HRG-induced gene regulation may be controlled by the MAPK cascade, while only 0.6% of the gene expression is controlled by ERE. A comparison with previously reported estrogen (E2)-regulated gene expression data revealed that only 12 common genes were identified between the 333 HRG-regulated (3.6%) and 239 E2-regulated (5.0%) gene groups. However, with respect to enriched upstream TFs, 4 common TFs were identified in the 14 HRG-regulated (28.6%) and 13 E2-regulated (30.8%) gene groups. These results indicated that while E2 and HRG may induce common TFs, the regulatory mechanisms that govern HRG- and E2-induced gene expression differ.

Regulation of plant innate immunity by three proteins in a complex conserved across the plant and animal kingdoms

Innate immunity against pathogen infection is an evolutionarily conserved process among multicellular organisms. Arabidopsis SNC1 encodes a Resistance protein that combines attributes of multiple mammalian pattern recognition receptors. Utilizing snc1 as an autoimmune model, we identified a discrete protein complex containing at least three members--MOS4 (Modifier Of snc1, 4), AtCDC5, and PRL1 (Pleiotropic Regulatory Locus 1)--that are all essential for plant innate immunity. AtCDC5 has DNA-binding activity, suggesting that this complex probably regulates defense responses through transcriptional control. Since the complex components along with their interactions are highly conserved from fission yeast to Arabidopsis and human, they may also have a yet-to-be-identified function in mammalian innate immunity.

High-resolution mapping of molecular events associated with immortalization, transformation, and progression to breast cancer in the MCF10 model

BACKGROUND

A comprehensive and consistent picture of the genetic changes that underlie breast cancer initiation, development, and progression remains unresolved. The MCF10 series of cell lines represents many steps in that progression. We performed high resolution mapping of the MCF10 series of cell lines to identify specific gene targets to elucidate the molecular correlates of immortalization, development, and progression of breast cancer at the level of individual genes.

DESIGN

We evaluated the initial untransformed outgrowths (MCF-10MS and MCF-10A) with six transformed cell lines with benign proliferations (MCF-10AT1, MCF-10AT1kcl2), carcinoma in situ (MCF-10CA1h cl13), and invasive carcinoma (MCF-10CA1h cl2, MCF-10CA1a cl1, MCF-10CA1d cl1). Losses and gains of loci at 112 unique human genome sites were interrogated using the multiplex ligation-dependent probe amplification assay (MLPA).

RESULTS

Cytogenetic alterations in the four benign progenitors that persisted in the CIS and invasive cell lines corresponded to gains and losses of genes by MLPA. MCF-10MS had only normal gene copies. The untransformed MCF-10A had cytogenetic gain of 5q13-qter with corresponding gains of the IL3, IL4 and IL12B genes at 5q31-q33; gain of distal 19q12-qter was reflected in gains in KLK3 and BAX gene loci at 19q13-q13.4. The observed genic gain of cMYC at 8q24.12 was not indicated by cytogenetics. The apparently balanced t(3;9) component of the t(3;9)(p13;p22)t(3;5)(p26;q31) resulted in complete loss of the CDKN2A and CDKN2B genes at 9p21. Additional clonal cytogenetic changes in the DCIS cell line (MCF-10A1h cl13) involving chromosomes 1, 3 and 10 persisted in the invasive progeny, with gain of corresponding genes at 1p13 (BCAR2, BCAR3, NRAS, TGFB2), at 3p12-13 (IL12A), and 3q21-27 (MME, PIK3CA, BCL6).

CONCLUSIONS

Our study adopted a comprehensive exploration of genetic changes using high resolution molecular probes applied to the MCF10 family of cell lines to identify individual genes in a continuum starting from normal breast epithelial cells and progressing through immortalization, transformation and invasive malignancy. Homozygous loss of CDKN2A and CDKN2B genes and gain of MYC were initiating immortalization events. Transformation and progression to malignancy event were marked by gains of IL13, VEGF, HRAS, TRAF2, and BCAS2, IL12A, and MME, respectively.

Using array-comparative genomic hybridization to define molecular portraits of primary breast cancers

We analysed 148 primary breast cancers using BAC-arrays containing 287 clones representing cancer-related gene/loci to obtain genomic molecular portraits. Gains were detected in 136 tumors (91.9%) and losses in 123 tumors (83.1%). Eight tumors (5.4%) did not have any genomic aberrations in the 281 clones analysed. Common (more than 15% of the samples) gains were observed at 8q11-qtel, 1q21-qtel, 17q11-q12 and 11q13, whereas common losses were observed at 16q12-qtel, 11ptel-p15.5, 1p36-ptel, 17p11.2-p12 and 8ptel-p22. Patients with tumors registering either less than 5% (median value) or less than 11% (third quartile) total copy number changes had a better overall survival (log-rank test: P=0.0417 and P=0.0375, respectively). Unsupervised hierarchical clustering based on copy number changes identified four clusters. Women with tumors from the cluster with amplification of three regions containing known breast oncogenes (11q13, 17q12 and 20q13) had a worse prognosis. The good prognosis group (Nottingham Prognostic Index (NPI) <or=3.4) tumors had frequent loss of 16q24-qtel. Genes significantly associated with estrogen receptor (ER), Grade and NPI were used to build k-nearest neighbor (KNN) classifiers that predicted ER, Grade and NPI status in the test set with an average misclassification rate of 24.7, 25.7 and 35.7%, respectively. These data raise the prospect of generating a molecular taxonomy of breast cancer based on copy number profiling using tumor DNA, which may be more generally applicable than expression microarray analysis.

Comparison of the latest commercial short and long oligonucleotide microarray technologies

Background

We compared the relative precision and accuracy of expression measurements obtained from three different state-of-the-art commercial short and long-oligonucleotide microarray platforms (Affymetrix GeneChip™, GE Healthcare CodeLink™ and Agilent Technologies). The design of the comparison was chosen to judge each platform in the context of a multi-project program.

Results

All wet-lab experiments and raw data acquisitions were performed independently by each commercial platform. Intra-platform reproducibility was assessed using measurements from all available targets. Inter-platform comparisons of relative signal intensities were based on a common and non-redundant set of roughly 3,400 targets chosen for their unique correspondence toward a single transcript. Despite many examples of strong similarities we found several areas of discrepancy between the different platforms.

Conclusion

We found a higher level of reproducibility from one-color based microarrays (Affymetrix and CodeLink) compared to the two-color arrays from Agilent. Overall, Affymetrix data had a slightly higher level of concordance with sample-matched real-time quantitative reverse-transcriptase polymerase chain reaction (QRT-PCR) data particularly for detecting small changes in gene expression levels.

Insights into gene expression changes impacting B-cell transformation: cross-species microarray analysis of bovine leukemia virus tax-responsive genes in ovine B cells

Large-animal models for leukemia have the potential to aid in the understanding of networks that contribute to oncogenesis. Infection of cattle and sheep with bovine leukemia virus (BLV), a complex retrovirus related to human T-cell leukemia virus type 1 (HTLV-1), is associated with the development of B-cell leukemia. Whereas the natural disease in cattle is characterized by a low tumor incidence, experimental infection of sheep leads to overt leukemia in the majority of infected animals, providing a model for studying the pathogenesis associated with BLV and HTLV-1. Tax(BLV), the major oncoprotein, initiates a cascade of events leading toward malignancy, although the basis of transformation is not fully understood. We have taken a cross-species ovine-to-human microarray approach to identify Tax(BLV)-responsive transcriptional changes in two sets of cultured ovine B cells following retroviral vector-mediated delivery of Tax(BLV). Using cDNA-spotted microarrays comprising 10,336 human genes/expressed sequence tags, we identified a cohort of differentially expressed genes, including genes related to apoptosis, DNA transcription, and repair; proto-oncogenes; cell cycle regulators; transcription factors; small Rho GTPases/GTPase-binding proteins; and previously reported Tax(HTLV-1)-responsive genes. Interestingly, genes known to be associated with human neoplasia, especially B-cell malignancies, were extensively represented. Others were novel or unexpected. The results suggest that Tax(BLV) deregulates a broad network of interrelated pathways rather than a single B-lineage-specific regulatory process. Although cross-species approaches do not permit a comprehensive analysis of gene expression patterns, they can provide initial clues for the functional roles of genes that participate in B-cell transformation and pinpoint molecular targets not identified using other methods in animal models.

Comprehensive copy number profiles of breast cancer cell model genomes

Introduction

Breast cancer is the most commonly diagnosed cancer in women worldwide and consequently has been extensively investigated in terms of histopathology, immunochemistry and familial history. Advances in genome-wide approaches have contributed to molecular classification with respect to genomic changes and their subsequent effects on gene expression. Cell lines have provided a renewable resource that is readily used as model systems for breast cancer cell biology. A thorough characterization of their genomes to identify regions of segmental DNA loss (potential tumor-suppressor-containing loci) and gain (potential oncogenic loci) would greatly facilitate the interpretation of biological data derived from such cells. In this study we characterized the genomes of seven of the most commonly used breast cancer model cell lines at unprecedented resolution using a newly developed whole-genome tiling path genomic DNA array.

Methods

Breast cancer model cell lines MCF-7, BT-474, MDA-MB-231, T47D, SK-BR-3, UACC-893 and ZR-75-30 were investigated for genomic alterations with the submegabase-resolution tiling array (SMRT) array comparative genomic hybridization (CGH) platform. SMRT array CGH provides tiling coverage of the human genome permitting break-point detection at about 80 kilobases resolution. Two novel discrete alterations identified by array CGH were verified by fluorescence in situ hybridization.

Results

Whole-genome tiling path array CGH analysis identified novel high-level alterations and fine-mapped previously reported regions yielding candidate genes. In brief, 75 high-level gains and 48 losses were observed and their respective boundaries were documented. Complex alterations involving multiple levels of change were observed on chromosome arms 1p, 8q, 9p, 11q, 15q, 17q and 20q. Furthermore, alignment of whole-genome profiles enabled simultaneous assessment of copy number status of multiple components of the same biological pathway. Investigation of about 60 loci containing genes associated with the epidermal growth factor family (epidermal growth factor receptor, HER2, HER3 and HER4) revealed that all seven cell lines harbor copy number changes to multiple genes in these pathways.

Conclusion

The intrinsic genetic differences between these cell lines will influence their biologic and pharmacologic response as an experimental model. Knowledge of segmental changes in these genomes deduced from our study will facilitate the interpretation of biological data derived from such cells.

Differential gene expression in genetically matched mouse melanoma cells with different metastatic potential

In vitro fusion of weakly metastatic Cloudman S91 melanoma cells with macrophages from DBA/2J mice (syngeneic with Cloudman S91 melanoma) produced hybrids with metastatic potentials ranging from low to high, with more than half showing enhanced metastasis over the parental melanoma [Clin. Exp. Metastasis 16 (1998) 299]. These hybrids, derived from the same parental fusion partners, represent a unique genetically matched model for analyzing differential gene expression regulating the metastatic phenotype. We have examined the differences in gene expression in metastatic fusion hybrid compared to its parental partners, non-/poorly metastatic melanoma cells and normal macrophages. An approach by selective polymerase chain reaction (PCR) amplification and display of 3' end restriction fragments of double-stranded cDNAs was used [Methods Enzymol. 303 (1999) 272]. Gene expression analyses showed an extensive set of transcripts that were up- or down-regulated in the most metastatic hybrid, H95-1, compared to the parental macrophages or melanoma cells. Sequence analyses of more than 60 of these differentially expressed cDNAs revealed significant up- or down-regulation of a number of genes known to be associated with metastasis of melanoma and other solid tumors. Some genes are found to express exclusively either in normal macrophages or in melanoma. Thirteen fragment sequences were found with no matches with GenBank search. Comparison of these gene expression patterns should be of great value in understanding the coordinate programs regulating metastasis. Further, the increased expression of gene(s) common in macrophage and fusion hybrids may be of importance in identifying the regulatory factor(s) related to macrophage-like trait, motility, a critical step of metastatic processes, in hybrids.