Model Of Breast Cancer Progression Research Articles

Abstract 4971: WBP2: A novel phospho-oncoprotein in estrogen receptor-positive breast cancer

Abstract WBP2 (WW-domain Binding Protein 2) was first implicated in breast cancer through our previous phosphoproteomics screen on the MCF10AT xenograft-derived isogenic cell line model of human breast cancer progression, where WBP2 was found to be differentially phosphorylated during breast cancer development. We had also shown it to be an authentic tyrosine phosphorylation target of EGFR signaling. In a follow up study, we found that WBP2 expression was low or undetectable in normal breast epithelial cells but overexpressed in breast cancer progression model as well as multiple breast cancer cells of various subtypes. Therefore, we aimed to investigate the oncogenic role of WBP2 in the growth and progression of human breast cancer through its protein overexpression and tyrosine phosphorylation. We first mapped the EGF-dependent tyrosine phosphorylation sites on WBP2 and identified a member of the Src family of tyrosine kinases as the putative upstream kinase of WBP2. Next, we found that Estrogen (E2) stimulation could similarly induce tyrosine phosphorylation of WBP2 via a crosstalk between EGFR and ER pathways. Subcellular fractionation study revealed a phosphorylation-dependent nuclear entry of WBP2 upon E2 or EGF stimulation. Consistent with the reported role of WBP2 as a coactivator for nuclear hormone receptor (ERα/PR), abrogation of tyrosine phosphorylation on WBP2 significantly impaired the E2-induced ER transactivation through reduced E2/EGF-stimulated nuclear entry of WBP2 and in vivo E2-dependent WBP2-ER interaction. Stable overexpression of wild type and phospho-mimic mutant of WBP2 in ER-positive MCF7 breast cancer cell enhanced its cell proliferation, anchorage-independent growth in soft agar, cell migration and cell invasion in the E2-independent and/or E2-dependent manner. These cellular processes could be inhibited, at least in part, by the phosphorylation-defective mutant of WBP2. Potential mechanisms of WBP2-mediated oncogenic transformation will be presented. Collectively, our findings have uncovered the potential of WBP2 as a novel phospho-oncoprotein in ER+ breast cancer. It is conceivable that WBP2 and/or its tyrosine phosphorylated form could serve as a potential prognostic marker or therapeutic target for human breast cancer. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 4971.

Abstract 187: Epigenetic memory during breast cancer progression is sustained by Smad signaling pathway

Abstract The molecular basis for the “epigenetic memory” that ensures maintenance of unique patterns of regulatory DNA methylation of selected genes responsible for cancer progression has remained elusive. Using a breast cancer progression model system, we found that hyperactive TGFβ-TGFβR-Smad2 signaling axis is involved in the maintenance of DNA hypermethylation mediated silencing of critical target genes to facilitate breast cancer progression. Disruption of TGFβ signaling caused a corresponding decrease in DNMT1 binding activity accompanied with increased expression of the target genes and acquisition of tumorigenic properties. These observations are consistent with passive demethylation of the newly synthesized DNA due to absence of sustained TGFβ-Smad signaling downstream events. In summary, we provide conclusive evidence that the reversal of the DNA hypermethylation status of gene promoters occurs as a result of TGFβ/Smad signaling pathway perturbation. By extension, we predict that inhibition of TGFβ-TGFβR-Smad2 signaling axis is an effective therapeutic strategy for breast cancer. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 187.

Abstract 1210: TIMP-1 regulation of breast cancer cell survival and its co-expression with CD63 in vivo

Abstract Purpose: The purpose of our study is to unveil the multi-faceted roles of Tissue Inhibitor of Metalloproteinases-1 (TIMP-1) in cancer progression with a particular focus on anti-apoptotic activity of TIMP-1. Introduction: TIMP-1 has been thought to inhibit cancer invasion/metastasis via its inhibition of Matrix Metalloproteinases (MMPs). However, clinical data showed that TIMP-1 is a poor prognostic marker in many human cancers. Recently, our lab has made a novel finding that TIMP-1 promotes MCF10A cell survival independent of its MMP-inhibitory activity through its interaction with the trans-membrane protein CD63. To investigate TIMP-1's anti-apoptotic effects in the cancerous setting, we have analyzed apoptosis in MDA-MB-231 breast cancer cells. Also, we have examined TIMP-1 and CD63 expression in MCF10DCIS.com tumor xenografts, a human breast cancer progression model. Experimental Procedures: TIMP-1 is highly expressed in the malignant human breast cancer cell line, MDA-MB-231. To evaluate TIMP-1 regulation of cell survival, we generated shRNA-mediated TIMP-1 knockdown MDA-MB-231 cell line. Upon apoptosis induction by staurosporine treatment or growth factor (GF) withdrawal, cell survival and apoptosis were examined by WST-1 assay and caspase activity assay, respectively. Expression and localization of TIMP-1 and CD63 in MCF10DCIS.com tumors was assessed in invasive and pre-invasive ductal lesions by immunohistochemical (IHC) analysis. Co-localization between TIMP-1 and CD63 was detected by confocal microscopic analysis of immunofluorescent staining and quantitated using a statistics-based software, Volocity. Results: Knockdown of TIMP-1 expression greatly increased the rate of apoptotic cell death in MDA-MB-231 cells after staurosporine treatment or GF withdrawal. IHC analysis of MCF10DCIS.com tumors revealed TIMP-1 cell surface staining in ducts without apoptotic/necrotic cores and fewer cells with surface TIMP-1 staining in comedo-necrotic ducts. CD63 staining pattern was punctate within cells as well as on the cell surface throughout the lesions. Confocal microscopic analysis of TIMP-1 and CD63, revealed positive correlation (Pearson's) and increased co-localization at the cell surface (Kx, Ky, and Mx, My -Volocity parameters). Conclusions: We previously demonstrated a novel function of TIMP-1 in cell survival via activation of the CD63 signaling complex in “normal” human breast epithelial cell line MCF10A, independent of its well-known MMP inhibitory activity. Here we report a similar protective role of TIMP-1 in human breast cancer cells. In addition, we show that TIMP-1 is co-expressed with CD63 in MCF10DCIS.com ductal tumors and co-localizes at the cell surface. Taken together, our findings further depict a dual nature of TIMP-1 in cancer progression: tumor-promoting activity via increased cell survival, and tumor-suppressing activity via its MMP-inhibitory activity. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 1210.

DNA methylation changes in a human cell model of breast cancer progression

Epigenetic inactivation of genes by DNA hypermethylation plays an important role in carcinogenesis. An in vitro model of human breast epithelial cell transformation was used to study epigenetic changes induced by estradiol during the neoplastic process. Different stages of tumor initiation and progression are represented in this model being MCF-10F the normal stage; trMCF cells, the transformed stage; bsMCF cells, the invasive stage and, caMCF cells, the tumor stage. Global methylation studies by restriction landmark genomic scanning (RLGS) showed an increased DNA methylation during the in the invasive and tumor stages. Expression studies showed that NRG1 (neuregulin 1), CSS3 (chondroitin sulfate synthase 3) and SNIP (SNAP-25-interacting protein) were downregulated in the invasive and tumor cells. The transformed cells showed low expression of STXBP6 (amysin) compared to the parental cells MCF-10F. The treatment of these cells with the demethylating agent 5-aza-dC alone or in combination with the histone deacetylase inhibitor trichostatin increased the expression of NRG1, STXBP6, CSS3 and SNIP confirming that DNA methylation plays an important role in the regulation of the expression of these genes. The NRG1 exon 1 has a region located between −136 and +79 (considering +1, the translational initiation site) rich in CpG sites that was analyzed by methylation specific PCR (MSP). NRG1 exon 1 showed progressive changes in the methylation pattern associated with the progression of the neoplastic process in this model; NRG1 exon 1 was unmethylated in MCF-10F and trMCF cells, becoming hypermethylated in the invasive (bsMCF) and tumor (caMCF) stages. Studies of human breast tissue samples showed that NRG1 exon 1 was partially methylated in 14 out of 17 (82.4%) invasive carcinomas although it was unmethylated in normal tissues (8 out of 10 normal breast tissue samples). Furthermore, NRG1 exon 1 was partially methylated in 9 out of 14 (64.3%) morphologically normal tissue samples adjacent to invasive carcinomas.

De la cellule mammaire normale à la cellule cancéreuse

The normal mammary gland is characterized by plasticity, related to hormonal influences. The knowledge of different types of epithelial cells, basal and luminal cells, associated with myoepithelial cells, as the concept of normal stem cell, have allowed the description of molecular entities through the studies of genomic profiling. These entities, or molecular portraits, are correlated to morphological heterogeneity. It was postulated that breast carcinoma arised from terminal ductulolobular unit. The classic model of breast cancer progression is seen as a linear multistep process (the stochastic theory) manifesting as a sequence of pathologically defined stages: atypical lesions, in situ carcinoma and invasive carcinoma with a succession of molecular alterations. The transformation defined is a pathway by stage. There are now some morphological, phenotypic, cytogenetic and genomic arguments to support a multiple distinct linear pathway model of progression and a hierarchical theory. Prevention and treatment of breast cancer must integrate these new concepts.

The Role of microRNA Genes in Breast Cancer Progression and Metastasis.

Abstract MicroRNAs influence tumor progression and metastasis via action as metastasis promoting genes (for example mir-373 and mir-520) or metastasis suppressor genes (for example mir-335). To identify additional microRNAs capable of driving breast cancer metastasis in vivo, we employed a functional genomics screen using the '4T1' syngeneic (Balb/c) mouse model of breast cancer progression. Approximately 400 microRNA sequences were subcloned into the pMSCV_puro retroviral expression vector and the resultant microRNA expression library transduced into fluorescent non-metastatic 67NR-pMSCV_mCherry and mildy-metastatic 66cl4-pMSCV_mCherry cells and selected with puromycin. The transduced cell lines were then implanted into the mammary fat pads of 20 syngeneic Balb/c mice per cell line. Following establishment of primary tumors, the primary tumors and secondary organs (lung, liver, spine, femurs), including any overt metastatic deposits, were dissected under a fluorescent stereomicroscope and the microRNA inserts amplified from the integrated retroviral genome by PCR.In an alternative approach, we have studied two populations of MDA-MB-231 human breast cancer cells that exhibit different behavior in vitro and in vivo to elucidate processes involved in cellular invasion and metastasis. A late-passage MDA-MB-231 (231variant) population formed invasive clusters when embedded in Matrigel, whereas early-passage (P3) MDA-MB-231 (231) cells did not. Moreover, 231v cells were more motile than 231 cells and showed enhanced tumorigenicity when grown as subcutaneous xenografts in nude mice, whereas proliferation and apoptotic response were indistinguishable between the two lines in vitro. Molecular characterization of the two cell populations cultured in 3D by array-based gene expression profiling revealed elevated expression of NF kappa B target genes in 231v cells (IL1A, IL1B, IL6, PTX3, NR4A2, HMOX1, FLIP). MicroRNA array analysis of 3D cultures also revealed marked induction (approximately 8-fold) of the related NF kappa B target microRNAs, mir-146a and mir-146b (Figure 1). Further evaluation of a panel of human breast cancer cell lines revealed that mir-146a and mir-146b were dramatically elevated in metastatic human breast cancer cell lines that display both epithelial-to-mesenchymal transition and high NF kappa B activity (MDA-MB-231, Hs578T, MDA-MB-436), compared to non-metastatic lines. Experiments to elucidate the function of mir-146a and mir-146b during breast cancer progression are underway. Figure 1: TaqMan qPCR analysis of mir-146a and mir-146b expression in 231 and 231v cells. Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 6142.

Apomab, a fully human agonistic antibody to DR5, exhibits potent antitumor activity against primary and metastatic breast cancer

Apomab, a fully human agonistic DR5 monoclonal antibody, triggers apoptosis through activation of the extrinsic apoptotic signaling pathway. In this study, we assessed the cytotoxic effect of Apomab in vitro and evaluated its antitumor activity in murine models of breast cancer development and progression. MDA-MB-231-TXSA breast cancer cells were transplanted into the mammary fat pad or directly into the tibial marrow cavity of nude mice. Apomab was administered early, postcancer cell transplantation, or after tumors progressed to an advanced stage. Tumor burden was monitored progressively using bioluminescence imaging, and the development of breast cancer-induced osteolysis was measured using microcomputed tomography. In vitro, Apomab treatment induced apoptosis in a panel of breast cancer cell lines but was without effect on normal human primary osteoblasts, fibroblasts, or mammary epithelial cells. In vivo, Apomab exerted remarkable tumor suppressive activity leading to complete regression of well-advanced mammary tumors. All animals transplanted with breast cancer cells directly into their tibiae developed large osteolytic lesions that eroded the cortical bone. In contrast, treatment with Apomab following an early treatment protocol inhibited both intraosseous and extraosseous tumor growth and prevented breast cancer-induced osteolysis. In the delayed treatment protocol, Apomab treatment resulted in the complete regression of advanced tibial tumors with progressive restoration of both trabecular and cortical bone leading to full resolution of osteolytic lesions. Apomab represents a potent immunotherapeutic agent with strong activity against the development and progression of breast cancer and should be evaluated in patients with primary and metastatic disease.

Key signalling nodes in mammary gland development and cancer. Mitogen-activated protein kinase signalling in experimental models of breast cancer progression and in mammary gland development

Seven classes of mitogen-activated protein kinase (MAPK) intracellular signalling cascades exist, four of which are implicated in breast disease and function in mammary epithelial cells. These are the extracellular regulated kinase (ERK)1/2 pathway, the ERK5 pathway, the p38 pathway and the c-Jun N-terminal kinase (JNK) pathway. In some forms of human breast cancer and in many experimental models of breast cancer progression, signalling through the ERK1/2 pathway, in particular, has been implicated as being important. We review the influence of ERK1/2 activity on the organised three-dimensional association of mammary epithelial cells, and in models of breast cancer cell invasion. We assess the importance of epidermal growth factor receptor family signalling through ERK1/2 in models of breast cancer progression and the influence of ERK1/2 on its substrate, the oestrogen receptor, in this context. In parallel, we consider the importance of these MAPK-centred signalling cascades during the cycle of mammary gland development. Although less extensively studied, we highlight the instances of signalling through the p38, JNK and ERK5 pathways involved in breast cancer progression and mammary gland development.

Therapeutic targeting of the focal adhesion complex prevents oncogenic TGF-β signaling and metastasis

IntroductionMammary tumorigenesis is associated with the increased expression of several proteins in the focal adhesion complex, including focal adhesion kinase (FAK) and various integrins. Aberrant expression of these molecules occurs concomitant with the conversion of TGF-β function from a tumor suppressor to a tumor promoter. We previously showed that interaction between β3 integrin and TβR-II facilitates TGF-β-mediated oncogenic signaling, epithelial-mesenchymal transition (EMT), and metastasis. However, the molecular mechanisms by which the focal adhesion complex contributes to β3 integrin:TβR-II signaling and the oncogenic conversion of TGF-β remain poorly understood.MethodsFAK expression and activity were inhibited in normal and malignant mammary epithelial cells (MECs) either genetically by using lentiviral-mediated delivery of shRNAs against FAK, or pharmacologically through in vitro and in vivo use of the FAK inhibitors, PF-562271 and PF-573228. Altered Smad2/3 and p38 MAPK activation, migration, EMT, and invasion in response to TGF-β1 were monitored in FAK-manipulated cells. TβR-II expression was increased in metastatic breast cancer cells by retroviral transduction, and the metastasis of FAK- and TβR-II-manipulated tumors was monitored by using bioluminescent imaging.ResultsTGF-β stimulation of MECs stabilized and activated FAK in a β3 integrin- and Src-dependent manner. Furthermore, by using the human MCF10A breast cancer progression model, we showed that increased FAK expression in metastatic breast cancer cells mirrored the acquisition of enhanced activation of p38 MAPK by TGF-β. Administering FAK inhibitors or rendering metastatic breast cancer cells FAK deficient abrogated the interaction between β3 integrin and TβR-II, thereby preventing TGF-β from (a) activating p38 MAPK; (b) stimulating MEC invasion, migration, and EMT; and (c) inducing early primary tumor dissemination to the lungs. Finally, in contrast to FAK depletion, adjuvant FAK chemotherapy of mammary tumors decreased their growth in part by diminished macrophage tumor infiltration.ConclusionsOur studies identify an essential function for FAK in mediating the interaction between β3 integrin and TβR-II, and thus in facilitating the oncogenic conversion of TGF-β required for mammary tumor metastasis. Furthermore, this study establishes chemotherapeutic targeting of FAK as an effective, two-pronged approach in preventing tumor progression both by decreasing innate immune cell infiltration, and by inhibiting early TGF-β-dependent metastasis.

Cytogenetic and cDNA Microarray Expression Analysis of MCF10 Human Breast Cancer Progression Cell Lines

We used a combination of spectral karyotyping, array comparative genomic hybridization, and cDNA microarrays to gain insights into the structural and functional changes of the genome in the MCF10 human breast cancer progression model cell lines. Spectral karyotyping data showed several chromosomal aberrations and array comparative genomic hybridization analysis identified numerous genomic gains and losses that might be involved in the progression toward cancer. Analysis of the expression levels of genes located within these genomic regions revealed a lack of correlation between chromosomal gains and losses and corresponding up-regulation or down-regulation for the majority of the approximately 1,000 genes analyzed in this study. We conclude that other mechanisms of gene regulation that are not directly related to chromosomal gains and losses play a major role in breast cancer progression.

MicroRNA-661, a c/EBPα Target, Inhibits Metastatic Tumor Antigen 1 and Regulates Its Functions

MicroRNAs (miR) have been identified as posttranscriptional modifiers of target gene regulation and control the expression of gene products important in cancer progression. Here, we show that miR-661 inhibits the expression of metastatic tumor antigen 1 (MTA1), a widely up-regulated gene product in human cancer, by targeting the 3' untranslated region (UTR) of MTA1 mRNA. We found that endogenous miR-661 expression was positively regulated by the c/EBPalpha transcription factor, which is down-regulated during cancer progression. c/EBPalpha directly interacted with the miR-661 chromatin and bound to miR-661 putative promoter that contains a c/EBPalpha-consensus motif. In addition, we found that the level of MTA1 protein was progressively up-regulated, whereas that of miR-661 and its activator, c/EBPalpha, were down-regulated in a breast cancer progression model consisting of MCF-10A cell lines whose phenotypes ranged from noninvasive to highly invasive. c/EBPalpha expression in breast cancer cells resulted in increased miR-661 expression and reduced MTA1 3'UTR-luciferase activity and MTA1 protein level. We also provide evidence that the introduction of miR-661 inhibited the motility, invasiveness, anchorage-independent growth, and tumorigenicity of invasive breast cancer cells. We believe our findings show for the first time that c/EBPalpha regulates the level of miR-661 and in turn modifies the functions of the miR661-MTA1 pathway in human cancer cells. Based on these findings, we suggest that miR-661 be further investigated for therapeutic use in down-regulating the expression of MTA1 in cancer cells.

Regulation of Macrophage Inhibitory Factor (MIF) by Epidermal Growth Factor Receptor (EGFR) in the MCF10AT Model of Breast Cancer Progression

Genetic aberration of EGFR is one of the major molecular characteristics of breast cancer. However, the molecular changes associated with EGFR signaling during different stages of breast cancer development have not been studied. In this study, complementary two-dimensional-DIGE and iTRAQ technologies were used to profile the expression level of proteins in 4 isogenic cell lines in the MCF10AT model of breast cancer progression following a time course of EGF stimulation. A total of 80 proteins (67 from iTRAQ, 15 from DIGE, 2 common in both) were identified to be up- or down-regulated by EGF treatment. Following EGF stimulation, the expression level of MIF, a cytokine that has been implicated in many human cancers, was decreased in MCF10A1 normal breast mammary epithelial cells, increased in MCF10AT1k preneoplastic and MCF10CA1h low grade breast cancer cells, but showed no obvious difference in the MCF10CA1a high grade cancer cells. The increase in MIF expression level following EGF treatment could also be observed in A431 cervical cancer cells. EGF-induced increases of MIF expression levels in CA1h breast cancer cells were abrogated when MEK, but not PIK3CA, was knocked down. In addition, silencing of MIF diminished the proliferation of EGF-stimulated CA1h cells when compared to control cells. Taken together, our data suggested an EGFR --> MEK --> MIF proliferative pathway that has never been reported previously and that this pathway "evolves" during disease progression as modeled by the MCF10AT system. Revelation of the novel relationship between MIF and EGF may contribute to an integrated understanding of the roles of these oncogenic factors during breast cancer development.

Increased production and secretion of HGF α‐chain and an antagonistic HGF fragment in a human breast cancer progression model

Invasive human breast carcinomas frequently coexpress increased hepatocyte growth factor (HGF) and its receptor Met, suggesting that establishment of an autocrine HGF loop is important in malignant disease. This study examines the expression patterns of HGF and Met activation during tumorigenesis and metastasis using a MCF10A-based model of Ha-Ras-induced human breast cancer progression. Deregulation of cadherin-based cell-cell adhesions, decreased expression of cytokeratins 8/18 and increased activity of matrix metalloproteinases such as MMP-2 occurs in premalignant and malignant (metastatic) cell lines compared to the parental nonmalignant cell line. Compared to the benign parent cell line, premalignant and malignant cell lines exhibit increased secretion of full length HGF alpha-chain and elevated Met tyrosine phosphorylation in complete medium. Interestingly, the premalignant and malignant cells also secrete a approximately 55 kDa HGF fragment. Epitope mapping of the approximately 55 kDa HGF fragment supports the presence of the N-terminal domain of the HGF alpha-chain with a truncation in the C-terminal domain. The approximately 55 kDa HGF fragment shows mobility in SDS-PAGE faster than HGF alpha-chain, but slightly slower than NK4, a previously established full antagonist of HGF. The separated approximately 55 kDa HGF fragment binds to animmobilized Met-IgG fusion protein, and inhibits both HGF/Met-IgG binding and HGF-induced Met-tyrosine phosphorylation. These results are the first demonstration of an antagonistic approximately 55 kDa HGF fragment secreted during breast carcinoma progression, which may have a negative regulatory effect on HGF signaling in premalignant breast epithelial cells.

Expression of Estrogenicity Genes in a Lineage Cell Culture Model of Human Breast Cancer Progression

The mRNA levels of estrogen receptors (ERα and ERβ), cytosolic sulfotransferases (SULT1E1, SULT1A1, SULT2A1 and SULT2B1), steroid sulfatase (STS), aromatase (CYP19), 17β‐hydroxysteroid dehydrogenases (17βHSD1 and 2), CYP1B1 and catechol‐O‐methyltransferase (COMT) were examined in MCF7 and in MCF10A‐derived cell lines representing a lineage cell culture model for breast cancer progression. Relative to MCF7, MCF10A‐derived cells expressed low levels of ERα but comparable levels of ERβ. In benign parental MCF10A breast epithelial cells, SULT1E1 mRNA was induced in confluent relative to subconfluent cell cultures. Proestrogenic 17βHSD1 mRNA was expressed in all of the MCF10A lineage cell lines while 17βHSD2 mRNA was most abundant in MCF10A cells. CYP1B1, SULT1A1 and SULT2B1 were expressed in MCF7 cells, while STS and COMT were widely detected across cell lines. Treatment with the potent histone deacetylase inhibitor trichostatin A (TSA) induced SULT1E1, SULT2B1 and CYP19 mRNA, but suppressed CYP1B1, STS, COMT, 17βHSD1 and 17βHSD2 mRNA in MCF10A lineage cell lines. In MCF7 cells, TSA treatment suppressed ERα, CYP1B1, STS, COMT, SULT1A1, and SULT2B1 but induced ERβ, CYP19 and SULT2A1 mRNA expression. The results indicate that relative to ER‐positive MCF7 cells, key determinants of breast estrogen metabolism are differentially regulated during neoplastic progression. Supported by ES05823 and ES06636.

Expression of estrogenicity genes in a lineage cell culture model of human breast cancer progression

TaqMan Gene Expression assays were used to profile the mRNA expression of estrogen receptor (ERalpha and ERbeta) and estrogen metabolism enzymes including cytosolic sulfotransferases (SULT1E1, SULT1A1, SULT2A1, and SULT2B1), steroid sulfatase (STS), aromatase (CYP19), 17beta-hydroxysteroid dehydrogenases (17betaHSD1 and 2), CYP1B1, and catechol-O-methyltransferase (COMT) in an MCF10A-derived lineage cell culture model for basal-like human breast cancer progression and in ERalpha-positive luminal MCF7 breast cancer cells. Low levels of ERalpha and ERbeta mRNA were present in MCF10A-derived cell lines. SULT1E1 mRNA was more abundant in confluent relative to subconfluent MCF10A cells, a non-tumorigenic proliferative breast disease cell line. SULT1E1 was also expressed in preneoplastic MCF10AT1 and MCF10AT1K.cl2 cells, but was markedly repressed in neoplastic MCF10A-derived cell lines as well as in MCF7 cells. Steroid-metabolizing enzymes SULT1A1 and SULT2B1 were only expressed in MCF7 cells. STS and COMT were widely detected across cell lines. Pro-estrogenic 17betaHSD1 mRNA was most abundant in neoplastic MCF10CA1a and MCF10DCIS.com cells, while 17betaHSD2 mRNA was more prominent in parental MCF10A cells. CYP1B1 mRNA was most abundant in MCF7 cells. Treatment with the histone deacetylase inhibitor trichostatin A (TSA) induced SULT1E1 and CYP19 mRNA but suppressed CYP1B1, STS, COMT, 17betaHSD1, and 17betaHSD2 mRNA in MCF10A lineage cell lines. In MCF7 cells, TSA treatment suppressed ERalpha, CYP1B1, STS, COMT, SULT1A1, and SULT2B1 but induced ERbeta, CYP19 and SULT2A1 mRNA expression. The results indicate that relative to the MCF7 breast cancer cell line, key determinants of breast estrogen metabolism are differentially regulated in the MCF10A-derived lineage model for breast cancer progression.

Apomab, a fully human agonistic DR5 monoclonal antibody inhibits tumour growth and osteolysis in murine models of breast cancer development and progression

Apomab, a fully human agonistic DR5 monoclonal antibody inhibits tumour growth and osteolysis in murine models of breast cancer development and progression

MicroRNA-7, a Homeobox D10 Target, Inhibits p21-Activated Kinase 1 and Regulates Its Functions

MicroRNAs are noncoding RNAs that inhibit the expression of their targets in a sequence-specific manner and play crucial roles during oncogenesis. Here we show that microRNA-7 (miR-7) inhibits p21-activated kinase 1 (Pak1) expression, a widely up-regulated signaling kinase in multiple human cancers, by targeting the 3'-untranslated region (UTR) of Pak1 mRNA. We noticed an inverse correlation between the levels of endogenous miR-7 and Pak1 expression in human cancer cells. We discovered that endogenous miR-7 expression is positively regulated by a homeodomain transcription factor, HoxD10, the loss of which leads to an increased invasiveness. HoxD10 directly interacts with the miR-7 chromatin. Accordingly, the levels of Pak1 protein are progressively up-regulated whereas those of miR-7 and its upstream activator HoxD10 are progressively down-regulated in a cellular model of breast cancer progression from low to highly invasive phenotypes. Furthermore, HoxD10 expression in highly invasive breast cancer cells resulted in an increased miR-7 expression but reduced Pak1 3'-UTR-luciferase activity and reduced Pak1 protein. Finally, we show that miR-7 introduction inhibits the motility, invasiveness, anchorage-independent growth, and tumorigenic potential of highly invasive breast cancer cells. Collectively, these findings establish for the first time that Pak1 is a target of miR-7 and that HoxD10 plays a regulatory role in modifying the expression of miR-7 and, consequently, the functions of the miR-7-Pak1 pathway in human cancer cells.

Multiple forms of BRMS1 are differentially expressed in the MCF10 isogenic breast cancer progression model

Clinical studies evaluating the mRNA expression level of the BRMS1 metastasis suppressor in the progression of breast cancer have not been consistent. The purpose of this study was to characterize endogenous BRMS1 mRNA and protein in a model of the progression of breast cancer. BRMS1 protein expression was evaluated in the genetically related MCF10 cell lines representing 'normal' breast epithelial cells (MCF10A), pre-malignant breast disease (MCF10AT), comedo ductal carcinoma in situ (MCF10DCIS.com), and metastatic carcinoma (MCF10CAa.1 and MCF10CAd.1alpha) with two antibodies that recognize distinct epitopes in the BRMS1 protein. Nuclear expression of the characteristic *35 kDa BRMS1 protein was detected in all cell lines. Because BRMS1 was expressed in the metastatic MCF10 variants, the BRMS1 exons were sequenced to scan for possible genetic mutations. BRMS1 was wild-type with the exception of a synonymous T/C transition in exon 7. However, alternatively spliced variants were detected by RT-PCR. Two variants, BRMS1.v2 and BRMS1.v4 were only detected in the MCF10A and AT cell lines, while BRMS1 and BRMS1.v3 were detected in all lines. These results demonstrate that expression of the characteristic *35 kDa BRMS1 protein is not sufficient to prevent metastasis. The differential expression of alternative splice variants suggests caution should be taken when evaluating BRMS1 mRNA in clinical samples.

Differential Expression of Novel Tyrosine Kinase Substrates during Breast Cancer Development

To identify novel tyrosine kinase substrates that have never been implicated in cancer, we studied the phosphoproteomic changes in the MCF10AT model of breast cancer progression using a combination of phosphotyrosyl affinity enrichment, iTRAQ technology, and LC-MS/MS. Using complementary MALDI- and ESI-based mass spectrometry, 57 unique proteins comprising tyrosine kinases, phosphatases, and other signaling proteins were detected to undergo differential phosphorylation during disease progression. Seven of these proteins (SPAG9, Toll-interacting protein (TOLLIP), WBP2, NSFL1C, SLC4A7, CYFIP1, and RPS2) were validated to be novel tyrosine kinase substrates. SPAG9, TOLLIP, WBP2, and NSFL1C were further proven to be authentic targets of epidermal growth factor signaling and Iressa (gefitinib). A closer examination revealed that the expression of SLC4A7, a bicarbonate transporter, was down-regulated in 64% of the 25 matched normal and tumor clinical samples. The expression of TOLLIP in clinical breast cancers was heterogeneous with 25% showing higher expression in tumor compared with normal tissues and 35% showing the reverse trend. Preliminary studies on SPAG9, on the other hand, did not show differential expression between normal and diseased states. This is the first time SLC4A7 and TOLLIP have been discovered as novel tyrosine kinase substrates that are also associated with human cancer development. Future molecular and functional studies will provide novel insights into the roles of TOLLIP and SLC4A7 in the molecular etiology of breast cancer.

Serial transplantation of NMU‐induced rat mammary tumors: A model of human breast cancer progression

Human breast cancer is a heterogeneous disease that appears to progress from an in situ tumor to invasive cancer. Little is known about the molecular events driving this progression. Although microarray technology has helped us understand the genetic heterogeneity of breast cancer, its application to studying the transition from in situ to invasive disease is limited by the inability to follow the progression of a single patient's tumor. We previously used rat specific microarrays to show that N-methyl-N-nitrosourea induced tumors are similar to low-grade estrogen-receptor positive human breast cancer. Here, we transplanted these tumors through 5 generations of syngeneic hosts, and studied 65 resulting tumors. Most transplanted tumors gradually progressed from a noninvasive, low-grade cancer to a higher-grade invasive disease, losing p63 localization and basement membrane integrity. Invasive cancers frequently demonstrated a more mesenchymal phenotype with increased vimentin expression. Additionally, a unique transplant series is described with a phenotype similar to human basal-like breast cancer. Rat-specific Affymetrix gene arrays containing 15,866 gene probes identified genes that differentiated highly invasive tumors from those of low invasive potential. A linear regression analysis was used to find genes whose change in expression paralleled increasing invasive features independent of the transplant lineage of origin. Genes identified were assigned membership in cell adhesion, signal transduction, cell cycle and extracellular matrix groups, among others. This animal model overcomes the difficulty in studying human breast cancer progression. Our data support a gradual and continuous alteration in programs of gene expression during breast cancer invasion.