Cyclin D1, EMS1 and 11q13 amplification in breast cancer

Overexpression of SERTAD3, a putative oncogene located within the 19q13 amplicon, induces E2F activity and promotes tumor growth

The amplified region of chromosome 19q13.1-13.2 has been associated with several cancers. The well-characterized oncogene AKT2 is located in this amplicon. Two members of the same gene family (SERTAD1 and SERTAD3) are also located within this region. We report herein the genomic structure and potential functions of SERTAD3. SERTAD3 has two transcript variants with short mRNA half-lives, and one of the variants is tightly regulated throughout G1 and S phases of the cell cycle. Overexpression of SERTAD3 induces cell transformation in vitro and tumor formation in mice, whereas inhibition of SERTAD3 by small interfering RNA (siRNA) results in a reduction in cell growth rate. Furthermore, luciferase assays based on E2F-1 binding indicate that SERTAD3 increases the activity of E2F, which is reduced by inhibition of SERTAD3 by siRNA. Together, our data support that SERTAD3 contributes to oncogenesis, at least in part, via an E2F-dependent mechanism.

Novel patterns of genome rearrangement and their association with survival in breast cancer

Representational Oligonucleotide Microarray Analysis (ROMA) detects genomic amplifications and deletions with boundaries defined at a resolution of approximately 50 kb. We have used this technique to examine 243 breast tumors from two separate studies for which detailed clinical data were available. The very high resolution of this technology has enabled us to identify three characteristic patterns of genomic copy number variation in diploid tumors and to measure correlations with patient survival. One of these patterns is characterized by multiple closely spaced amplicons, or "firestorms," limited to single chromosome arms. These multiple amplifications are highly correlated with aggressive disease and poor survival even when the rest of the genome is relatively quiet. Analysis of a selected subset of clinical material suggests that a simple genomic calculation, based on the number and proximity of genomic alterations, correlates with life-table estimates of the probability of overall survival in patients with primary breast cancer. Based on this sample, we generate the working hypothesis that copy number profiling might provide information useful in making clinical decisions, especially regarding the use or not of systemic therapies (hormonal therapy, chemotherapy), in the management of operable primary breast cancer with ostensibly good prognosis, for example, small, node-negative, hormone-receptor-positive diploid cases.

BRCA1-IRIS activates cyclin D1 expression in breast cancer cells by downregulating the JNK phosphatase DUSP3/VHR

Cyclin D1 plays an important role in cell cycle progression. In breast cancer, Cyclin D1 expression is deregulated by several mechanisms. We previously showed that in breast cancer cells, overexpression of BRCA1-IRIS induces Cyclin D1 overexpression and increases cell proliferation. BRCA1-IRIS alone or in complex with steroid receptor co-activators was targeted to the cyclin D1 promoter pre-bound by the c-Jun/AP1 and activated its transcription, which could explain the co-overexpression of BRCA1-IRIS and Cyclin D1 in breast cancer cells coupled with their increased proliferation. We report here an alternate or a complementary pathway by which BRCA1-IRIS activates Cyclin D1 expression. BRCA1-IRIS overexpression decreases the expression of the dual specificity phosphatase, DUSP3/VHR, an endogenous inhibitor of several MAPKs, including c-Jun N-terminal kinase. Although, the mechanism by which BRCA1-IRIS overexpression accomplishes that is not yet known, it is sufficient to induce Cyclin D1 overexpression in a human mammary epithelial cell model. Cyclin D1 overexpression could be blocked by co-overexpression of VHR in those cells. Furthermore, in 2 breast cancer cell lines that overexpress both BRCA1-IRIS and Cyclin D1 (MCF-7 and SKBR3) depletion of BRCA1-IRIS by RNA interference attenuated the expression of Cyclin D1 by elevating the expression level of VHR. These data demonstrate a critical role for BRCA1-IRIS in human breast cancer cell-cycle control and suggest that deregulated expression of BRCA1-IRIS is likely to reduce dependence on normal physiological growth stimuli, thereby providing a growth advantage to tumor cells and a potential mechanism of resistance to endocrine therapy.

Cortactin: the gray eminence of the cytoskeleton

Cortactin, an actin filament-binding protein and target of multiple kinases, has emerged as a central element connecting signaling pathways with cytoskeleton restructuring. It is involved in a perplexingly diverse array of cellular processes, including cell motility, invasiveness, synaptogenesis, endocytosis, intercellular contact assembly, and host-pathogen interactions, where the common denominator appears to be a role in the coordination of membrane dynamics with cytoskeletal remodeling. Although in recent years our knowledge about cortactin has increased exponentially, the exact mechanisms underlying its fundamental roles remain to be defined.

Specificity, selection and significance of gene amplifications in cancer

DNA copy number amplifications activate oncogenes and are found in the majority of advanced solid tumors. Cell-lineage specificity and oncogene affinity of DNA amplifications in cancer suggest that properties of precursor stem cells and selection pressure in the tissue micro-environment determine the genomic location of gene amplifications. Biological specificity and significance of gene amplifications make them potential targets for clinical applications. Here we discuss the specificity of non-randomly occurring DNA copy number amplifications as defining features for cancers, their selection in the tumor tissue, and significance in the clinical practice.

Frequency, prognostic impact, and subtype association of 8p12, 8q24, 11q13, 12p13, 17q12, and 20q13 amplifications in breast cancers

Background

Oncogene amplification and overexpression occur in tumor cells. Amplification status may provide diagnostic and prognostic information and may lead to new treatment strategies. Chromosomal regions 8p12, 8q24, 11q13, 17q12 and 20q13 are recurrently amplified in breast cancers.

Methods

To assess the frequencies and clinical impact of amplifications, we analyzed 547 invasive breast tumors organized in a tissue microarray (TMA) by fluorescence in situ hybridization (FISH) and calculated correlations with histoclinical features and prognosis. BAC probes were designed for: (i) two 8p12 subregions centered on RAB11FIP1 and FGFR1 loci, respectively; (ii) 11q13 region centered on CCND1; (iii) 12p13 region spanning NOL1; and (iv) three 20q13 subregions centered on MYBL2, ZNF217 and AURKA, respectively. Regions 8q24 and 17q12 were analyzed with MYC and ERBB2 commercial probes, respectively.

Results

We observed amplification of 8p12 (amplified at RAB11FIP1 and/or FGFR1) in 22.8%, 8q24 in 6.1%, 11q13 in 19.6%, 12p13 in 4.1%, 17q12 in 9.9%, 20q13^Z (amplified at ZNF217 only) in 9.9%, and 20q13^Co (co-amplification of two or three 20q13 loci) in 8.5% of cases. The 8q24, 12p13, and 17q12 amplifications were correlated with high grade. The most frequent single amplifications were 8p12 (9.8%), 8q24 (3.3%) and 12p13 (3.3%), 20q13^Z and 20q13^Co (1.6%) regions. The 17q12 and 11q13 regions were never found amplified alone. The most frequent co-amplification was 8p12/11q13. Amplifications of 8p12 and 17q12 were associated with poor outcome. Amplification of 12p13 was associated with basal molecular subtype.

Conclusion

Our results establish the frequencies, prognostic impacts and subtype associations of various amplifications and co-amplifications in breast cancers.

Net1 and Myeov: computationally identified mediators of gastric cancer

Gastric adenocarcinoma (GA) is a significant cause of mortality worldwide. The molecular mechanisms of GA remain poorly characterised. Our aim was to characterise the functional activity of the computationally identified genes, NET 1 and MYEOV in GA. Digital Differential Display was used to identify genes altered expression in GA-derived EST libraries. mRNA levels of a subset of genes were quantitated by qPCR in a panel of cell lines and tumour tissue. The effect of pro- and anti-inflammatory stimuli on gene expression was investigated. Cell proliferation and invasion were measured using in an in-vitro GA model following inhibition of expression using siRNA. In all, 23 genes not previously reported in association with GA were identified. Two genes, Net1 and Myeov, were selected for further analysis and increased expression was detected in GA tissue compared to paired normal tissue using quantitative PCR. siRNA-mediated downregulation of Net1 and Myeov resulted in decreased proliferation and invasion of gastric cancer cells in vitro. These functional studies highlight a putative role for NET1 and Myeov in the development and progression of gastric cancer. These genes may provide important targets for intervention in GA, evidenced by their role in promoting invasion and proliferation, key phenotypic hallmarks of cancer cells.

Regulation of the actin cytoskeleton in cancer cell migration and invasion

Malignant cancer cells utilize their intrinsic migratory ability to invade adjacent tissues and the vasculature, and ultimately to metastasize. Cell migration is the sum of multi-step processes initiated by the formation of membrane protrusions in response to migratory and chemotactic stimuli. The driving force for membrane protrusion is localized polymerization of submembrane actin filaments. Recently, several studies revealed that molecules that link migratory signals to the actin cytoskeleton are upregulated in invasive and metastatic cancer cells. In this review, we summarize recent progress on molecular mechanisms of formation of invasive protrusions used by tumor cells, such as lamellipodia and invadopodia, with regard to the functions of key regulatory proteins of the actin cytoskeleton; WASP family proteins, Arp2/3 complex, LIM-kinase, cofilin, and cortactin.

BRCA1-IRIS regulates cyclin D1 expression in breast cancer cells

The regulator of cell cycle progression, cyclin D1, is up-regulated in breast cancer cells; its expression is, in part, dependent on ERalpha signaling. However, many ERalpha-negative tumors and tumor cell lines (e.g., SKBR3) also show over-expression of cyclin D1. This suggests that, in addition to ERalpha signaling, cyclin D1 expression is under the control of other signaling pathways; these pathways may even be over-expressed in the ERalpha-negative cells. We previously noticed that both ERalpha-positive and -negative cell lines over-express BRCA1-IRIS mRNA and protein. Furthermore, the level of over-expression of BRCA1-IRIS in ERalpha-negative cell lines even exceeded its over-expression level in ERalpha-positive cell lines. In this study, we show that: (1) BRCA1-IRIS forms complex with two of the nuclear receptor co-activators, namely, SRC1 and SRC3 (AIB1) in an ERalpha-independent manner. (2) BRCA1-IRIS alone, or in connection with co-activators, is recruited to the cyclin D1 promoter through its binding to c-Jun/AP1 complex; this binding activates the cyclin D1 expression. (3) Over-expression of BRCA1-IRIS in breast cells over-activates JNK/c-Jun; this leads to the induction of cyclin D1 expression and cellular proliferation. (4) BRCA1-IRIS activation of JNK/c-Jun/AP1 appears to account for this, because in cells that were depleted from BRCA1-IRIS, JNK remained inactive. However, depletion of SRC1 or SRC3 instead reduced c-Jun expression. Our data suggest that this novel signaling pathway links BRCA1-IRIS to cellular proliferation through c-Jun/AP1 nuclear pathway; finally, this culminates in the increased expression of the cyclin D1 gene.

Association between Pak1 expression and subcellular localization and tamoxifen resistance in breast cancer patients

BACKGROUND

p21-activated kinase 1 (Pak1) phosphorylates many proteins in both normal and transformed cells. Its ability to phosphorylate and thereby activate the estrogen receptor alpha (ERalpha) potentially limits the effectiveness of antiestrogen treatment in breast cancer. Here we studied associations between Pak1 expression and subcellular localization in tumor cells and tamoxifen resistance.

METHODS

Pak1 protein expression was evaluated in 403 primary breast tumors from premenopausal patients who had been randomly assigned to 2 years of adjuvant tamoxifen or no treatment. Tamoxifen response was evaluated by comparing recurrence-free survival in relation to Pak1 and ERalpha expression in untreated versus tamoxifen-treated patients. Tamoxifen responsiveness of human MCF-7 breast cancer cells that inducibly expressed constitutively active Pak1 or that transiently overexpressed wild-type Pak1 (Wt-Pak1) or Pak1 that lacked functional nuclear localization signals (Pak1DeltaNLS) was evaluated by analyzing cyclin D1 promoter activation and protein levels as markers for ERalpha activation. The response to tamoxifen in relation to Pak1 expression was analyzed in naturally tamoxifen-resistant Ishikawa human endometrial cancer cells. All statistical tests were two-sided.

RESULTS

Among patients who had ERalpha-positive tumors with low Pak1 expression, those treated with tamoxifen had better recurrence-free survival than those who received no treatment (hazard ratio [HR] = 0.502, 95% confidence interval [CI] = 0.331 to 0.762; P = .001) whereas there was no difference in recurrence-free survival between treatment groups for patients whose tumors had high cytoplasmic (HR = 0.893, 95% CI = 0.420 to 1.901; P = .769) or any nuclear Pak1 expression (HR = 0.955, 95% CI = 0.405 to 2.250; P = .916). In MCF-7 cells, overexpression of Wt-Pak1, but not of Pak1DeltaNLS, compromised tamoxifen response by stimulating cyclin D1 expression. Treatment of Ishikawa cells with tamoxifen led to an increase in the amount of nuclear Pak1 and Pak1 kinase activity, suggesting that tamoxifen, to some extent, regulates Pak1 expression.

CONCLUSIONS

Our data support a role for Pak1, particular Pak1 localized to the nucleus, in ERalpha signaling and in tamoxifen resistance.

Alterations of the CCND1 and HER-2/neu (ERBB2) proteins in esophageal and gastric cancers

We evaluated the relationship of amplification and polysomy of both the CCND1 and the ERBB2 (alias HER-2/NEU) genes to the overexpression of their proteins in esophageal and gastric cancers and also their association with clinicopathological features. CCND1 gene amplification (45%) was more prevalent than polysomy (25%) in esophageal carcinoma, but the pattern observed was similar in gastric adenocarcinoma (10% amplification, 15% polysomy). For ERBB2, polysomy was a more frequent mechanism than amplification in both esophageal (32.5 vs. 7.5%) and gastric (15 vs. 5%) cancers. Overexpression of cyclin D1 protein was identified in 37.5% of the specimens of esophageal tumors and 35% of gastric tumors, and overexpression of Her-2/neu protein in 12.5 and 7.5%, respectively. The kappa-statistics revealed a fair agreement in both types of tumors only in overexpression and amplification of the CCND1 gene; the ERBB2 gene showed a fair agreement in amplification and polysomy and the level of protein expression in gastric adenocarcinoma. Thus, polysomy 17 could contribute to a high Her-2/neu protein level, at least in gastric cancer. Our data indicated an association with alcohol consumption and the CCND1 gene or protein levels, in both esophageal and gastric cancers.

Cyclin D1 and breast cancer

Cyclin D1 is one of the frequently overexpressed proteins and one of the commonly amplified genes in breast cancer. This article reviews the roles of cyclin D1 in cell-cycle regulation (normal and abnormal), mammary gland development and carcinogenesis and the relationship to oestrogen in breast tissues. It concludes by presenting the clinical, prognostic and therapeutic implications of our current knowledge of cyclin D1 in breast cancer.

Recurrent coamplification of cytoskeleton-associated genes EMS1 and SHANK2 with CCND1 in oral squamous cell carcinoma

Chromosomal band 11q13 is frequently amplified in oral squamous cell carcinoma (OSCC) and assumed to be critically involved in tumor initiation and progression by proto-oncogene activation. Though cyclin D1 (CCND1) is supposed to be the most relevant oncogene, several additional putative candidate genes are inside this chromosomal region, for which their actual role in tumorigenesis still needs to be elucidated. To characterize the 11q13 amplicon in detail, 40 OSCCs were analyzed by comparative genomic hybridization to DNA microarrays (matrix-CGH) containing BAC clones derived from chromosomal band 11q13. This high-resolution approach revealed a consistent amplicon about 1.7 Mb in size including the CCND1 oncogene. Seven BAC clones covering FGF3, EMS1, and SHANK2 were shown to be frequently coamplified inside the CCND1 amplicon. Subsequent analysis of tissue microarrays by FISH revealed amplification frequencies of 36.8% (88/239) for CCND1, 34.3% (60/175) for FGF3, 37.4% (68/182) for EMS1, and 36.3% (61/168) for SHANK2. Finally, quantitative mRNA expression analysis demonstrated consistent overexpression of CCND1 in all tumors and of EMS1 and SHANK2 in a subset of specimens with 11q13 amplification, but no expression of FGF3 in any of the cases. Our study underlines the critical role of CCND1 in OSCC development and additionally points to the functionally related genes EMS1 and SHANK2, both encoding for cytoskeleton-associated proteins, which are frequently coamplified with CCND1 and therefore could cooperatively contribute to OSCC pathogenesis.

A role for the scaffolding adapter GAB2 in breast cancer

The scaffolding adapter GAB2 maps to a region (11q13-14) commonly amplified in human breast cancer, and is overexpressed in breast cancer cell lines and primary tumors, but its functional role in mammary carcinogenesis has remained unexplored. We found that overexpression of GAB2 (Grb2-associated binding protein 2) increases proliferation of MCF10A mammary cells in three-dimensional culture. Coexpression of GAB2 with antiapoptotic oncogenes causes lumenal filling, whereas coexpression with Neu (also known as ErbB2 and HER2) results in an invasive phenotype. These effects of GAB2 are mediated by hyperactivation of the Shp2-Erk pathway. Furthermore, overexpression of Gab2 potentiates, whereas deficiency of Gab2 ameliorates, Neu-evoked breast carcinogenesis in mice. Finally, GAB2 is amplified in some GAB2-overexpressing human breast tumors. Our data suggest that GAB2 may be a key gene within an 11q13 amplicon in human breast cancer and propose a role for overexpression of GAB2 in mammary carcinogenesis. Agents that target GAB2 or GAB2-dependent pathways may be useful for treating breast tumors that overexpress GAB2 or HER2 or both.

The cell cycle checkpoint gene Rad9 is a novel oncogene activated by 11q13 amplification and DNA methylation in breast cancer

Human Rad9 (hRad9), a structural homologue of yeast Schizosaccharomyces pombe rad9, is involved in cell cycle checkpoints and apoptosis. hRad9 can serve as a corepressor of androgen receptor in prostate cancer cells, but little is known about its role in the development of breast or other cancers. In the present study, semiquantitative reverse transcription-PCR showed that Rad9 mRNA levels were up-regulated in 52.1% (25 of 48) of breast tumors, and this up-regulation correlated with tumor size (P = 0.037) and local recurrence (P = 0.033). Overexpression of Rad9 mRNA was partly due to an increase in Rad9 gene number as measured by quantitative PCR. In other breast tumors with Rad9 mRNA overexpression but without increase in gene number, there was differential methylation of two putative Sp1/3 binding sites within the first and second introns of the Rad9 gene, which was similarly found in MCF-7 breast cancer cell line with increased Rad9 mRNA. Silencing Rad9 expression by RNA interference in MCF-7 cell line inhibited its proliferation in vitro. Promoter assays indicated that the Sp1/3 site in intron 2 may act as a silencer. In vivo binding of Sp3 to intron 2 was shown by chromatin immunoprecipitation assays. Treatment of MCF-7 cell line with 5'-aza-2'-deoxycytidine reduced Rad9 mRNA expression and also increased binding of Sp3 to the demethylated intron 2 region. Collectively, these findings suggest that Rad9 is a novel oncogene candidate activated by 11q13 amplification and DNA hypermethylation in breast cancer and may play a role in tumor proliferation and local invasion.

Adverse effect of adjuvant tamoxifen in premenopausal breast cancer with cyclin D1 gene amplification

Cyclins D1 and A2 are cell cycle regulators that also have the ability to interact with the estrogen receptor (ER) and consequently interfere with antiestrogen treatment in breast cancer. Experimental data support this concept, but the clinical relevance needs to be further established. In this study, we evaluated cyclin D1 and A2 protein expression by immunohistochemistry and cyclin D1 gene (CCND1) amplification by fluorescence in situ hybridization in 500 primary breast cancers arranged in tissue microarrays. Patients had been randomized to 2 years of adjuvant tamoxifen or no treatment with a median follow-up of 14 years, allowing for subgroup analysis of treatment response defined by cyclin status. We found that both cyclin D1 and A2 protein overexpression was associated with an impaired tamoxifen response, although not significant in multivariate interaction analyses, whereas tamoxifen-treated patients with CCND1-amplified tumors had a substantially increased risk for disease recurrence after tamoxifen treatment in univariate analyses [relative risk (RR), 2.22; 95% confidence interval (95% CI), 0.94-5.26; P = 0.06] in contrast to non-amplified tumors (RR, 0.39; 95% CI, 0.23-0.65; P < 0.0001). Consequently, a highly significant interaction between tamoxifen treatment and CCND1 amplification could be shown regarding both recurrence-free survival (RR, 6.38; 95% CI, 2.29-17.78; P < 0.001) and overall survival (RR, 5.34; 95% CI, 1.84-15.51; P = 0.002), suggesting an agonistic effect of tamoxifen in ER-positive tumors. In node-positive patients, the disparate outcome according to gene amplification status was even more accentuated. In summary, our data implicate that despite a significant correlation to cyclin D1 protein expression, amplification status of the CCND1 gene seems a strong independent predictor of tamoxifen response, and possibly agonism, in premenopausal breast cancer.

Amplification of EMSY, a novel oncogene on 11q13, in high grade ovarian surface epithelial carcinomas

OBJECTIVES

Amplification of the 11q13 locus is commonly observed in a number of human cancers including both breast and ovarian cancer. Cyclin D1 and EMS1 have been implicated as candidate oncogenes involved in the emergence of amplification at this locus. Detailed analysis of the 11q13 amplicon in breast cancer led to the discovery of four regions of amplification suggesting the involvement of other genes. Here, we investigate the role of EMSY, a recently described BRCA2 interacting protein, as a key element of the 11q13 amplicon in ovarian cancer. EMSY maps to 11q13.5 and is amplified in 13% of breast and 17% of ovarian carcinomas.

METHODS

EMSY amplification was assessed by fluorescent in-situ hybridization (FISH) in 674 ovarian cancers in a tissue microarray and correlated with histopathological subtype and tumor grade. A detailed map of the 11q13 amplicon in 51 cases of ovarian cancer was obtained using cDNA-array-based comparative genomic hybridization (aCGH). To further characterize the role of EMSY within this amplicon, we evaluated both the amplification profiles and RNA expression levels of EMSY and two other genes from the 11q13 amplicon in an additional series of 22 ovarian carcinomas.

RESULTS

EMSY amplification was seen in 52/285 (18%) high grade papillary serous carcinomas, 4/27 (15%) high grade endometrioid carcinomas, 3/38 (8%) clear cell carcinomas, and 3/10 (30%) undifferentiated carcinomas. aCGH mapping of 11q13 in ovarian cancer showed that EMSY localized to the region with the highest frequency of copy number gain. Cyclin D1 and EMS1 showed a lower frequency of copy number gain. A highly significant correlation between EMSY gene amplification and RNA expression was also observed (P = 0.0001). This was a stronger correlation than for other genes at 11q13 including Cyclin D1 and PAK1.

CONCLUSIONS

These findings support the role of EMSY as a key oncogene within the 11q13 amplicon in ovarian cancer.

Cortactin overexpression results in sustained epidermal growth factor receptor signaling by preventing ligand-induced receptor degradation in human carcinoma cells

The chromosome 11q13 region is frequently amplified in human carcinomas and results in an increased expression of various genes including cortactin, and is also associated with an increased invasive potential. Cortactin acts as an important regulator of the actin cytoskeleton. It is therefore very tempting to speculate that cortactin is the crucial gene within the 11q13 amplicon that mediates the invasive potential of these carcinomas. Cortactin also participates in receptor-mediated endocytosis, and recent findings have shown that, during receptor internalization, cortactin overexpression inhibits the ubiquitylation-mediated degradation of the epidermal growth factor receptor, resulting in a sustained ligand-induced epidermal growth factor receptor activity.

Aberrations of 11q13 in laryngeal squamous cell lines and their prognostic significance

Chromosomal aberrations were analyzed in 12 established cell lines derived from laryngeal squamous cell carcinoma. Cytogenetic and fluorescence in situ hybridization studies were used to identify aberrations in the 11q13 region and in some other chromosome regions. Amplification of 11q13 was established only in the cell lines derived from subjects with a survival period of less than 5 years and, together with the 3q gain, were the only chromosomal structural abnormalities connected with short survival. In this group we also found translocations with a breakpoint within 11q13. In three cell lines, 11q13 was observed as a homogenously staining region. The results suggest that amplification of 11q13, as well as re-arrangements potentially involved in up-regulation of the oncogenes mapped in 11q13, should be considered as markers of poor prognosis in laryngeal cancer. A diagnostic significance of 11q13 may be increased by a parallel determination with 3q gain.

Cyclin D1 in Breast Cancer Pathogenesis

Taking a perspective on available evidence that emphasizes relevance to human disease, cyclin D1 is solidly established as an oncogene with an important pathogenetic role in breast cancer and other human tumors. However, the precise cellular mechanisms through which aberrant cyclin D1 expression drives human neoplasia are less well established. Indeed, emerging evidence suggests that cyclin D1 might act, predominantly or at least in part, through pathways that do not involve its widely accepted function as a cell cycle regulator. Although therapeutic exploitation of the role of cyclin D1 as a molecular driver of breast cancer carries great promise, it is also suggested that direct targeting of the cyclin D1 gene or gene products may prove more successful than approaches that rely on arguably incomplete knowledge of the oncogenic mechanisms of cyclin D1.

A 700-kb physical and transcription map of the cervical cancer tumor suppressor gene locus on chromosome 11q13

Nonrandom deletion of chromosome 11q13 sequences is a significant event in a number of human tumors. We have recently identified a 300-kb minimal area of deletion in primary cervical tumors that overlaps with deletions observed in endocrine and nasopharyngeal tumors. We have also observed a 5.7-kb homozygous deletion within this interval in HeLa cells (a cervical cancer cell line), HeLa cell-derived tumorigenic hybrids, and a primary cervical tumor, suggesting the presence of a tumor suppressor gene in this region. In the present investigation, we have constructed a 700-kb contig map encompassing the 300-kb deletion using the human genome sequence database and confirmed the map using various STS markers from the region. Our map also shows the overlap of a previously published rare, heritable fragile site, FRA11A, with the cervical cancer deletion locus. The mapped region contains highly repetitive GC-poor sequences. We have identified and characterized eight different polymorphic microsatellite markers from the sequences within and surrounding the deletion. Further, expression studies performed with 18 different ESTs localized adjacent to the homozygous deletion showed the presence of a transcript for only one of the ESTs, AA282789. This EST mapping within the homozygous deletion is also expressed in HeLa cells, thereby excluding the EST as the putative tumor suppressor gene. Additionally, analysis of four candidate genes (SF3B2, BRMS1, RIN1, and RAB1B) from the region showed expression of the expected size message in both the nontumorigenic and the tumorigenic HeLa cell hybrids, thereby excluding them as the putative tumor suppressor gene(s). However, Northern blot analysis with a fifth candidate gene, PACS1 (phosphofurin acidic cluster sorting protein), mapped to the deletion/FRA11A overlap region showed the expression of an 8-kb transcript in HeLa and five other tumor cell lines in addition to the expected 4.5-kb transcript. Since the gene shows abundant expression in normal tissues and an altered transcript is observed in tumor cell lines, we hypothesize that this gene could represent sequences of the putative tumor suppressor gene. Finally, we have observed a perfect 48-bp CAG/CCG repeat 99 kb proximal to D11S913, the marker linked to the neurodegenerative disorder spinocerebellar ataxia 5. The physical and transcription maps and the microsatellite markers of the 700-kb region of chromosome 11q13 should be helpful in the cloning of the cervical cancer tumor suppressor gene.

The actin cytoskeleton in normal and pathological cell motility

Cell motility is crucial for tissue formation and for development of organisms. Later on cell migration remains essential throughout the lifetime of the organism for wound healing and immune responses. The actin cytoskeleton is the cellular engine that drives cell motility downstream of a complex signal transduction cascade. The basic molecular machinery underlying the assembly and disassembly of actin filaments consists of a variety of actin binding proteins that regulate the dynamic behavior of the cytoskeleton in response to different signals. The multitude of proteins and regulatory mechanisms partaking in this system makes it vulnerable to mutations and alterations in expression levels that ultimately may cause diseases. The most familiar one is cancer that in later stages is characterized by active aberrant cell migration. Indeed tumor invasion and metastasis are increasingly being associated with deregulation of the actin system.

Regulation of apoptosis by fau revealed by functional expression cloning and antisense expression

Functional expression cloning is a powerful strategy for identifying critical steps in biological pathways independently of prior assumptions. It is particularly suitable for the identification of molecules crucial to the control of apoptosis. Our screen for sequences suppressing T-cell apoptosis isolated a sequence antisense to fau (Finkel-Biskis-Reilly murine sarcoma virus (FBR-MuSV)-associated ubiquitously expressed gene). The fox gene in FBR murine osteosarcoma virus is also antisense to fau and several reports have indicated that fau displays tumour suppressor and oncogenic properties in different contexts. Our observations indicate that the fau antisense sequence suppresses expression of endogenous fau mRNA and produces resistance to apoptosis induced both by the glucocorticoid analogue dexamethasone' by ultraviolet radiation, and by the anticancer drug cisplatin. In all cases, colony-forming ability is protected, indicating that fau affects the critical events prior to commitment to cell death. Overexpression of fau in the sense orientation induces cell death, which is inhibited both by Bcl-2 and by inhibition of caspases, in line with its proposed role in apoptosis.

Cortactin signalling and dynamic actin networks

Cortactin was first identified over a decade ago, and its initial characterization as both an F-actin binding protein and v-Src substrate suggested that it was likely to be a key regulator of actin rearrangements in response to tyrosine kinase signalling. The recent discovery that cortactin binds and activates the actin related protein (Arp)2/3 complex, and thus regulates the formation of branched actin networks, together with the identification of multiple protein targets of the cortactin SH3 domain, have revealed diverse cellular roles for this protein. This article reviews current knowledge regarding the role of cortactin in signalling to the actin cytoskeleton in the context of these developments.

Visualizing Chromosomes as Transcriptome Correlation Maps: Evidence of Chromosomal Domains Containing Co-expressed Genes—A Study of 130 Invasive Ductal Breast Carcinomas

Completion of the working draft of the human genome has made it possible to analyze the expression of genes according to their position on the chromosomes. Here, we used a transcriptome data analysis approach involving for each gene the calculation of the correlation between its expression profile and those of its neighbors. We used the U133 Affymetrix transcriptome data set for a series of 130 invasive ductal breast carcinomas to construct chromosomal maps of gene expression correlation (transcriptome correlation map). This highlighted nonrandom clusters of genes along the genome with correlated expression in tumors. Some of the gene clusters identified by this method probably arose because of genetic alterations, as most of the chromosomes with the highest percentage of correlated genes (1q, 8p, 8q, 16p, 16q, 17q, and 20q) were also the most frequent sites of genomic alterations in breast cancer. Our analysis showed that several known breast tumor amplicons (at 8p11-p12, 11q13, and 17q12) are located within clusters of genes with correlated expression. Using hierarchical clustering on samples and a Treeview representation of whole chromosome arms, we observed a higher-order organization of correlated genes, sometimes involving very large chromosomal domains that could extend to a whole chromosome arm. Transcription correlation maps are a new way of visualizing transcriptome data. They will help to identify new genes involved in tumor progression and new mechanisms of gene regulation in tumors.

Expression of AMAP1, an ArfGAP, provides novel targets to inhibit breast cancer invasive activities

Identification of the molecular machinery employed in cancer invasion, but not in normal adult cells, will greatly contribute to cancer therapeutics. Here we found that an ArfGAP, AMAP1/PAG2, is expressed at high levels in highly invasive breast cancer cells, but at very low levels in noninvasive breast cancer cells and normal mammary epithelial cells. siRNA-mediated silencing of AMAP1 effectively blocked the invasive activities. AMAP1 expression in human breast primary tumors also indicated its potential correlation with malignancy. Paxillin and cortactin have been shown to colocalize at invadopodia and play a pivotal role in breast cancer invasion. We found that AMAP1 is also localized at invadopodia, and acts to bridge paxillin and cortactin. This AMAP1-mediated trimeric protein complex was detected only in invasive cancer cells, and blocking this complex formation effectively inhibited their invasive activities in vitro and metastasis in mice. Our results indicate that AMAP1 is a component involved in invasive activities of different breast cancers, and provide new information regarding the possible therapeutic targets for prevention of breast cancer invasion and metastasis.

Genomic organization of the 8p11-p12 amplicon in three breast cancer cell lines

Amplification of chromosomal regions leads to an increase of DNA copy number and expression of oncogenes in human breast cancer (HBC). Amplification of the 8p11-p12 region occurs in 10-15% of primary, uncultured HBCs. In our panel of 11 breast cancer cells, three cell lines, SUM-44, SUM-52, and SUM-225, have overlapping amplicons in the 8p11-p12 region. To characterize genome structure of the amplified regions, we performed fluorescence in situ hybridization using 8p11-p12 BAC clones in the 3 cell lines. The results revealed that the 8p11-p12 amplicon has a highly complex structure and that FGFR1 is not in the common core-amplified domain in 3 breast cancer cell lines with the amplicon. These 3 cell lines provide good models for genetic and functional studies of candidate oncogenes of the 8p11-p12 region.

Oncogenic pathways in hereditary and sporadic breast cancer

Cancer is a genetic disease. Breast cancer tumorigenesis can be described as a multi-step process in which each step is thought to correlate with one or more distinct mutations in major regulatory genes. The question addressed is how far a multi-step progression model for sporadic breast cancer would differ from that for hereditary breast cancer. Hereditary breast cancer is characterized by an inherited susceptibility to breast cancer on basis of an identified germline mutation in one allele of a high penetrance susceptibility gene (such as BRCA1, BRCA2, CHEK 2, TP53 or PTEN). Inactivation of the second allele of these tumour suppressor genes would be an early event in this oncogenic pathway (Knudson's "two-hit" model). Sporadic breast cancers result from a serial stepwise accumulation of acquired and uncorrected mutations in somatic genes, without any germline mutation playing a role. Mutational activation of oncogenes, often coupled with non-mutational inactivation of tumour suppressor genes, is probably an early event in sporadic tumours, followed by more, independent mutations in at least four or five other genes, the chronological order of which is likely less important. Oncogenes that have been reported to play an early role in sporadic breast cancer are MYC, CCND1 (Cyclin D1) and ERBB2 (HER2/neu). In sporadic breast cancer, mutational inactivation of BRCA1/2 is rare, as inactivation requires both gene copies to be mutated or totally deleted. However, non-mutational functional suppression could result from various mechanisms, such as hypermethylation of the BRCA1 promoter or binding of BRCA2 by EMSY. In sporadic breast tumorigenesis, at least three different pathway-specific mechanisms of tumour progression are recognizable, with breast carcinogenesis being different in ductal versus lobular carcinoma, and in well differentiated versus poorly differentiated ductal cancers. Thus, different breast cancer pathways emerge early in the process of carcinogenesis, ultimately leading to clinically different tumour types. As mutations acquired early during tumorigenesis will be present in all later stages, large-scale gene expression profiling using DNA microarray analysis techniques can help to classify breast cancers into clinically relevant subtypes.

The phosphoprotein StarD10 is overexpressed in breast cancer and cooperates with ErbB receptors in cellular transformation

We have identified that StarD10, a member of the START protein family, is overexpressed in both mouse and human breast tumors. StarD10 was initially discovered on the basis of its cross-reactivity with a phosphoserine-specific antibody in mammary tumors from Neu/ErbB2 transgenic mice and subsequently isolated from SKBR3 human breast carcinoma cells using a multistep biochemical purification strategy. We have shown that StarD10 is capable of binding lipids. StarD10 was found to be overexpressed in 35% of primary breast carcinomas and 64% of human breast cancer cell lines, correlating with their ErbB2/Her2 status. Coexpression of StarD10 with ErbB1/epidermal growth factor receptor in murine fibroblasts enhanced anchorage-independent growth in soft agar, providing evidence for functional cooperation between StarD10 and ErbB receptor signaling. Taken together, these data suggest that overexpression of this lipid-binding protein contributes to breast oncogenesis.

EMSY links breast cancer gene 2 to the 'Royal Family'

Although the role of the breast cancer gene 2 (BRCA2) tumor suppressor gene is well established in inherited breast and ovarian carcinomas, its involvement in sporadic disease is still uncertain. The recent identification of a novel BRCA2 binding protein, EMSY, as a putative oncogene implicates the BRCA2 pathway in sporadic tumors. Furthermore, EMSY's binding to members of the 'Royal Family' of chromatin remodeling proteins may lead to a better understanding of the physiological function of BRCA2 and its role in chromatin remodeling.

EMSY links the BRCA2 pathway to sporadic breast and ovarian cancer

The BRCA2 gene is mutated in familial breast and ovarian cancer, and its product is implicated in DNA repair and transcriptional regulation. Here we identify a protein, EMSY, which binds BRCA2 within a region (exon 3) deleted in cancer. EMSY is capable of silencing the activation potential of BRCA2 exon 3, associates with chromatin regulators HP1beta and BS69, and localizes to sites of repair following DNA damage. EMSY maps to chromosome 11q13.5, a region known to be involved in breast and ovarian cancer. We show that the EMSY gene is amplified almost exclusively in sporadic breast cancer (13%) and higher-grade ovarian cancer (17%). In addition, EMSY amplification is associated with worse survival, particularly in node-negative breast cancer, suggesting that it may be of prognostic value. The remarkable clinical overlap between sporadic EMSY amplification and familial BRCA2 deletion implicates a BRCA2 pathway in sporadic breast and ovarian cancer.

Cyclins and breast cancer

The D-type and E-type cyclins control the G(1) to S phase transition during normal cell cycle progression and are critical components of steroid- and growth factor-induced mitogenesis in breast epithelial cells. Mammary epithelial cell-specific overexpression of these genes leads to mammary carcinoma, while in cyclin D1-deficient mice mammary gland development is arrested prior to lobuloalveolar development. Cyclin D1 null mice are resistant to mammary carcinoma induced by the neu and ras oncogenes, indicating an essential role for cyclin D1 in the development of some mammary cancers. Cyclin D1 and E1 are commonly overexpressed in primary breast cancer, with some evidence of an association with an adverse patient outcome. This observation may result in part from their ability to confer resistance to endocrine therapies. The functional consequences of cyclin E overexpression in breast cancer are likely related to its role in cell cycle progression, whereas that of cyclin D1 may also be a consequence of a more recently defined role in transcriptional regulation.

The neuropeptide galanin augments lobuloalveolar development

Mammary lobuloalveolar development during pregnancy is controlled by ovarian sex steroids and pituitary prolactin release. In organ culture these hormones are incapable of reproducing the density and size of lobuloalveoli seen in mice, suggesting the existence of other undiscovered factors. We showed previously that galanin knockout mice fail to lactate sufficiently for pup survival following their first pregnancy. Here we demonstrate that prolactin treatment of galanin knockout mice allows pup survival but does not completely rescue lobuloalveolar development or reduced milk protein expression. When galanin was used in combination with prolactin in mammary organ culture, larger and more numerous lobules were produced than with prolactin alone. Galanin alone produced sustained activation of STAT5a and the induction of milk protein expression but did not induce lobulogenesis. Examination of the transcriptional interaction between galanin and prolactin using oligonucleotide microarrays demonstrated synergistic and antagonistic modes of interaction between these hormones. These data establish a new role for galanin as a hormone augmenting mammary development during pregnancy in concert with prolactin.