The temporal balance between self-renewal and differentiation of human neural stem cells requires the amyloid precursor protein

Neurogenesis in the developing human cerebral cortex occurs at a particularly slow rate owing in part to cortical neural progenitors preserving their progenitor state for a relatively long time, while generating neurons. How this balance between the progenitor and neurogenic state is regulated, and whether it contributes to species-specific brain temporal patterning, is poorly understood. Here, we show that the characteristic potential of human neural progenitor cells (NPCs) to remain in a progenitor state as they generate neurons for a prolonged amount of time requires the amyloid precursor protein (APP). In contrast, APP is dispensable in mouse NPCs, which undergo neurogenesis at a much faster rate. Mechanistically, APP cell-autonomously contributes to protracted neurogenesis through suppression of the proneurogenic activator protein-1 transcription factor and facilitation of canonical WNT signaling. We propose that the fine balance between self-renewal and differentiation is homeostatically regulated by APP, which may contribute to human-specific temporal patterns of neurogenesis.

Establishment and characterization of cetuximab resistant head and neck squamous cell carcinoma cell lines: focus on the contribution of the AP-1 transcription factor

BACKGROUND

After an initial response to EGFR targeted therapy, secondary resistance almost invariably ensues, thereby limiting the clinical benefit of the drug. Hence, it has been recognized that the successful implementation of targeted therapy in the treatment of HNSCC cancer is very much dependent on predictive biomarkers for patient selection.

METHODS

We generated an in vitro model of acquired cetuximab resistance by chronically exposing three HNSCC cell lines to increasing cetuximab doses. Gene expression profiles of sensitive parental cells and resistant daughter cells were compared using microarray analysis. Growth inhibitory experiments were performed with an HB-EGF antibody and the MMP inhibitor, both in combination with cetuximab. Characteristics of EMT were analyzed using migration and invasion assays, immunofluorescent vimentin staining and qRT-PCR for several genes involved in this process. The function of the transcription factor AP-1 was investigated using qRT-PCR for several genes upregulated or downregulated in cetuximab resistant cells. Furthermore, anchorage-independent growth was investigated using the soft agar assay.

RESULTS

Gene expression profiling shows that cetuximab resistant cells upregulate several genes, including interleukin 8, the EGFR ligand HB-EGF and the metalloproteinase ADAM19. Cytotoxicity experiments with neutralizing HB-EGF antibody could not induce any growth inhibition, whereas an MMP inhibitor inhibited cell growth in cetuximab resistant cells. However, no synergetic effects combined with cetuximab could be observed. Cetuximab resistant cells showed traits of EMT, as witnessed by increased migratory potential, increased invasive potential, increased vimentine expression and increased expression of several genes involved in EMT. Furthermore, expression of upregulated genes could be repressed by the treatment with apigenin. The cetuximab resistant LICR-HN2 R10.3 cells tend to behave differently in cell culture, forming spheres. Therefore, soft agar assay was performed and showed more and larger colonies when challenged with cetuximab compared to PBS challenged cells.

CONCLUSIONS

In summary, our results indicate that increased expression of the ligand HB-EGF could contribute to resistance towards cetuximab in our cetuximab resistant HNSCC cells. Furthermore, several genes upregulated or downregulated in cetuximab resistant cells are under control of the AP-1 transcription factor. However, more studies are warranted to further unravel the role of AP-1 in cetuximab resistance.

A core invasiveness gene signature reflects epithelial-to-mesenchymal transition but not metastatic potential in breast cancer cell lines and tissue samples

Introduction

Metastases remain the primary cause of cancer-related death. The acquisition of invasive tumour cell behaviour is thought to be a cornerstone of the metastatic cascade. Therefore, gene signatures related to invasiveness could aid in stratifying patients according to their prognostic profile. In the present study we aimed at identifying an invasiveness gene signature and investigated its biological relevance in breast cancer.

Methods & Results

We collected a set of published gene signatures related to cell motility and invasion. Using this collection, we identified 16 genes that were represented at a higher frequency than observed by coincidence, hereafter named the core invasiveness gene signature. Principal component analysis showed that these overrepresented genes were able to segregate invasive and non-invasive breast cancer cell lines, outperforming sets of 16 randomly selected genes (all P<0.001). When applied onto additional data sets, the expression of the core invasiveness gene signature was significantly elevated in cell lines forced to undergo epithelial-mesenchymal transition. The link between core invasiveness gene expression and epithelial-mesenchymal transition was also confirmed in a dataset consisting of 2420 human breast cancer samples. Univariate and multivariate Cox regression analysis demonstrated that CIG expression is not associated with a shorter distant metastasis free survival interval (HR = 0.956, 95%C.I. = 0.896–1.019, P = 0.186).

Discussion

These data demonstrate that we have identified a set of core invasiveness genes, the expression of which is associated with epithelial-mesenchymal transition in breast cancer cell lines and in human tissue samples. Despite the connection between epithelial-mesenchymal transition and invasive tumour cell behaviour, we were unable to demonstrate a link between the core invasiveness gene signature and enhanced metastatic potential.

Expression profiling of migrated and invaded breast cancer cells predicts early metastatic relapse and reveals Krüppel-like factor 9 as a potential suppressor of invasive growth in breast cancer

Cell motility and invasion initiate metastasis. However, only a subpopulation of cancer cells within a tumor will ultimately become invasive. Due to this stochastic and transient nature, in an experimental setting, migrating and invading cells need to be isolated from the general population in order to study the gene expression profiles linked to these processes. This report describes microarray analysis on RNA derived from migrated or invaded subpopulations of triple negative breast cancer cells in a Transwell set-up, at two different time points during motility and invasion, pre-determined as “early” and “late” in real-time kinetic assessments. Invasion- and migration-related gene expression signatures were generated through comparison with non-invasive cells, remaining at the upper side of the Transwell membranes. Late-phase signatures of both invasion and migration indicated poor prognosis in a series of breast cancer data sets. Furthermore, evaluation of the genes constituting the prognostic invasion-related gene signature revealed Krüppel-like factor 9 (KLF9) as a putative suppressor of invasive growth in breast cancer. Next to loss in invasive vs non-invasive cell lines, KLF9 also showed significantly lower expression levels in the “early” invasive cell population, in several public expression data sets and in clinical breast cancer samples when compared to normal tissue. Overexpression of EGFP-KLF9 fusion protein significantly altered morphology and blocked invasion and growth of MDA-MB-231 cells in vitro. In addition, KLF9 expression correlated inversely with mitotic activity in clinical samples, indicating anti-proliferative effects.

Abstract 4300: Comparative assessment of cell viability and motility kinetics by novel real-time technology and classic endpoint assays

Background Elucidation of biological mechanisms underlying deregulated proliferation and motility of cancer cells and identification of potential therapeutic targets require accurate cell-based monitoring. The xCELLigence Real Time Cell Analysis (RTCA) technology (Roche Applied Science) constitutes a non-invasive and label-free approach to assess cell viability and motility in real time, hereby countering key features of classic label-based endpoint detection methods. Here we show results of in vitro detection of cell viability and migration on 2 cancer cell lines using xCELLigence RTCA DP and correlate these with data obtained from parallel experiments carried out using established assessment methods for each process. Methods and results Kinetic viability and migration measurements were carried out on the MDA-MB-231 (breast cancer) and A549 (lung cancer) cell lines using the xCELLigence RTCA DP instrument. Cell viability was assessed during 10 days of incubation using modified 16-well plates (E-plate) containing microelectrodes at the well bottoms for impedance-based detection of attachment, spreading and proliferation, expressed as a Cell Index (CI) value. Cell migration was measured during 38 hours using 16-well plates (CIM16-plate) consisting of an upper and a lower chamber separated by a microporous membrane equipped with a similar detection system at the bottom side. The Sulforhodamine B (SRB) assay and a 24-well Transwell system served as reference tools to assess viability and migratory kinetics. Viability was estimated by optical density (OD) reading (540 nm) of solubilized cells that were fixed and stained with SRB at a rate of 1 plate per day. Good correlations were observed between SRB and RTCA CI for 5x103 and 104 MDA-MB-231 cells/mL (Spearman's ≤ = 0.79 and 0.84 resp) and similar doubling times (p = 0.459). The experimental Transwell design allowed dynamic quantitation of cancer cell migration by fixing and staining of the insert membranes in methanol and crystal violet in duplicates at 10 time points during a 24 hour-incubation. Pixel area quantitation showed strong correlation with xCELLigence CI (Spearman's ≤ = 0.90 for both cell lines). However, OD measurements (590 nm) correlated even stronger with CI (Spearman's ≤ = 0.96 and 1.00 for MDA-MB-231 and A549). Moreover, analysis of random migration indicated a significant difference between RTCA CI and area / OD (p &lt; 0.001) implying reduced detection limits of the xCELLigence system. Conclusions The similarity between observations as performed with conventional approaches and xCELLigence makes both methods interchangeable. Added with results indicating reduced detection limits, xCELLigence provides an accurate detection platform for high-throughput kinetic screenings and for determination of time-dependent cell proliferation and motility dynamics.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 4300. doi:1538-7445.AM2012-4300

Abstract 1898: Potential molecular mechanisms of intrinsic resistance to EGFR-targeting monoclonal antibodies in HNSCC

Background: Head and Neck Squamous Cell Carcinoma (HNSCC) comprises 90% of all head and neck cancers and is still a major cause of morbidity and mortality worldwide. The epidermal growth factor receptor (EGFR) is overexpressed in 80-95% of all HNSCC tumors. Since EGFR initiates important signal transduction pathways in HNSCC carcinogenesis, anti-EGFR therapeutics were developed in order to prevent its activation. However, many tumors remain non-responsive, since the single-agent response rate of the monoclonal antibody cetuximab is less than 15%. Therefore, biomarkers predicting sensitivity to EGFR-targeted therapy are needed. Methods: First, the IC50 (drug dose reducing cell growth to 50%) of cetuximab and panitumumab was determined on seven HNSCC cell lines by the sulforhodamine B assay. In addition, these cell lines were screened for mutations in K-Ras by High Resolution Melting Analysis, EGFRvIII mutation and HPV infection by PCR. Cell growth was monitored in real-time using an xCELLigence system (Roche Applied Science) in order to determine the optimal incubation period at which a clear effect of cetuximab treatment on cell growth could be detected. Next, “sensitive” and “resistant” cell lines were treated with 15nM cetuximab for the predefined incubation period and RNA was isolated using the Trizol method. A genome-wide gene expression analysis was performed by comparison of expression profiles of “sensitive” and “resistant” HNSCC cells. Results: Neither K-Ras nor EGFRvIII mutation and no HPV DNA could be detected. Based on the IC50 values for cetuximab and panitumumab, cell lines were either classified as “sensitive” (n=3), “resistant” (n=2) or “intermediate” (n=2). The IC50 values of the “sensitive” cell lines ranged between 0.05 - 0.43nM for cetuximab and 0.01 - 0.45nM for panitumumab. Discussion: The IC50 values of cetuximab and panitumumab were very similar, as expected since both drugs belong to the same family of EGFR-targeting therapeutics. The cell lines used in our study did not show K-Ras or EGFRvIII mutations and were HPV negative. The xCELLigence results indicate that cetuximab (15nM) starts showing a clear effect on cell growth after 13h, implying that the signalling pathways elicited by cetuximab have been activated at this time point. Preliminary results from microarray analysis indicate that intrinsic cetuximab-resistance in HNSCC can be mediated cell line-dependently by different signaling pathways. In addition, putative characteristics of epithelial-to-mesenchymal transition were seen in “resistant” compared to “sensitive” cell lines.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 1898. doi:1538-7445.AM2012-1898

Abstract 4319: Gene expression profiling of isolated small migratory and invasive breast cancer cells at different times during chemotaxis

Background Chemotactic cell motility and tissue invasion are key processes initiating cancer cell dissemination and metastasis. Adequate molecular profiling of chemotaxis-driven tumor cells is impeded by the transient and stochastic nature of motility occurring in only a small subset of tumor cells. To unveil molecular pathways implicated in breast cancer cell invasion and migration, an in vitro set-up was designed to isolate total RNA for microarray hybridisation from sequestered migratory and invasive breast cancer cell subpopulations at two predefined incubation stages. These target populations were compared to non-migratory and non-invasive cells to obtain a molecular picture of migratory and invasive breast cancer cell behavior. Methods and results A 24-well Transwell set-up was used to perform both migration and Matrigel invasion experiments on MDA-MB-231 breast cancer cells after 24h serum starvation (4x105 cells/insert). A Matrigel coating (20%/15μL) was applied to the bottom-side of insert membranes in both settings. For invasion experiments, a layer of Matrigel (20%/20μL) was added to the top side of the membranes. Initially, an “early” and a “late” timepoint for RNA-extraction have been selected by monitoring migration and invasion using the xCELLigence system (Roche Applied Science). High-quality total RNA was isolated at these predefined timepoints from both migratory / invasive and reference cells and hybridized onto Illumina HumanHT-12 v4 BeadChips in biological triplicates. Differential gene expression analysis and pathway analysis were done using BioConductor in R and Ingenuity Pathway Analysis respectively, considering only FDR-corrected p-values &lt; 0.1 as significant. First, a time-independent comparison was performed between all grouped migratory and invasive samples, revealing a total of 988 differentially expressed genes, of which the majority occurring in the late phase. Further analysis focused on early expression changes as these may be causative to more extended late events. Pathway analysis of differential genes associated with early migratory and early invasive cells in comparison with their reference counterparts identified NF-κB-related (p=0.0034) and TGFβ-related (p=0.04) expression to be closely associated with migration and invasion respectively. Conclusions This work has aimed to determine specific gene expression characteristics of solely migrating and invading breast cancer cells. Preliminary findings suggest strong involvement of NF-κB-based pathways early in migration, but not in invasion. On the other hand, TGFβ-signaling changes were more closely associated with early invasive behaviour. Moreover, a global comparison identified significant expression differences between both states of cell motility.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 4319. doi:1538-7445.AM2012-4319

Abstract 3427: A core invasiveness gene signature reveals reduced EMT in samples from patients with IBC, potentially regulated by decreased EGFR- and TGFb-signaling

Introduction. We identified a core invasiveness gene (CIG) signature that predicts the invasive properties of breast cancer cell lines. In the current study, we investigate the translational utility of the current gene signature in human breast cancer, including inflammatory breast cancer (IBC). The latter is a highly invasive and metastatic breast cancer subtype.

Materials and methods. Six publicly available gene expression data sets and a data set on 137 IBC and 252 non-IBC samples were analyzed. Each sample was classified according to sets of stromal (N=2), prognostic (N=2), stem cell (N=3), epithelial-to-mesenchymal transition (EMT) (N=3) and pathway (N=20) gene signatures. In addition, the cell-of-origin subtype classifier and our own CIG-signature were applied. Associations between the CIG-signature and clinicopathological or molecular features were searched for using univariate and multivariate analysis.

Results. We identified associations of the CIG signature (FDR&lt;0.01) with a mammosphere-derived classifier (median Rs=0.49) and with two EMT-signatures (Core-EMT: median Rs=0.52; EMT/stromal classifier: median Rs=0.59). In addition EGFR, STAT3 and TGFb were found to be hyperactivated in CIG-positive tumors (median Rs=0.45; 0.33 and 0.60 respectively). No relations between CIG-expression and stromal gene expression, molecular subtypes or any of the clinicopathological variables were observed. Compared to non-IBC, decreased CIG-expression, TGFb- and EGFR-activation were observed in IBC (respectively P&lt;0.0001, P&lt;0.0001 and P=0.036). As for other EMT-associated gene signatures, both positive (Claudin-low and LYN-signatures: P=0.004 and P=0.015) and negative (EMT/stromal classifier: P=0.015) associations with IBC have been observed. When testing the core-EMT signature, no difference was found (P=0.166).

Discussion. We show that the CIG signature in breast cancer is correlated with EMT, stem cell biology and EGFR-, TGFb- and STAT3-activation. Samples from patients with IBC demonstrate ambiguous EMT-patterns, suggest that tumor cells from patients with IBC are in a specific state of cell plasticity and EMT as such is not the main mode of invasion in IBC. On the contrary, lowered TGFb signaling in IBC suggest a form of collective invasion.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 3427. doi:10.1158/1538-7445.AM2011-3427

Is there a role for mammary stem cells in inflammatory breast carcinoma?: a review of evidence from cell line, animal model, and human tissue sample experiments

Stem cells are pluripotent cells, with a large replicative potential, which perform normal physiological functions such as tissue renewal and damage repair. However, because of their long lifespan and high replicative potential, stem cells are ideal targets to accumulate multiple mutations. Therefore, they can be regarded as being responsible for the initiation of tumor formation. In the past, numerous studies have shown that the presence of an elaborate stem cell compartment within a tumor is associated with aggressive tumor cell behavior, frequent formation of metastases, resistance to therapy, and poor patient survival. From this perspective, tumors from patients with inflammatory breast cancer (IBC), an aggressive breast cancer subtype with a dismal clinical course, are most likely to be associated with stem cell biology. To date, this hypothesis is corroborated by evidence resulting from in vitro and in vivo experiments. Both gene and microRNA expression profiles highlighted several stem cell-specific signal transduction pathways that are hyperactivated in IBC. Also, these stem cell-specific signal transduction pathways seem to converge in the activation of nuclear factor-kappa B, a molecular hallmark of IBC, and induction of epithelial-to-mesenchymal transition. Recently, the latter mechanism was identified as a prerequisite for the induction of stem cell characteristics in breast cancer cells.

Quantitative methylation profiling in tumor and matched morphologically normal tissues from breast cancer patients

Background

In the present study, we determined the gene hypermethylation profiles of normal tissues adjacent to invasive breast carcinomas and investigated whether these are associated with the gene hypermethylation profiles of the corresponding primary breast tumors.

Methods

A quantitative methylation-specific PCR assay was used to analyze the DNA methylation status of 6 genes (DAPK, TWIST, HIN-1, RASSF1A, RARβ2 and APC) in 9 normal breast tissue samples from unaffected women and in 56 paired cancerous and normal tissue samples from breast cancer patients.

Results

Normal tissue adjacent to breast cancer displayed statistically significant differences to unrelated normal breast tissues regarding the aberrant methylation of the RASSF1A (P = 0.03), RARβ2 (P = 0.04) and APC (P = 0.04) genes. Although methylation ratios for all genes in normal tissues from cancer patients were significantly lower than in the cancerous tissue from the same patient (P ≤ 0.01), in general, a clear correlation was observed between methylation ratios measured in both tissue types for all genes tested (P < 0.01). When analyzed as a categorical variable, there was a significant concordance between methylation changes in normal tissues and in the corresponding tumor for all genes tested but RASSF1A. Notably, in 73% of patients, at least one gene with an identical methylation change in cancerous and normal breast tissues was observed.

Conclusions

Histologically normal breast tissues adjacent to breast tumors frequently exhibit methylation changes in multiple genes. These methylation changes may play a role in the earliest stages of the development of breast neoplasia.

A microRNA Expression Profile Consisting of 12 microRNAs Is Associated with Inflammatory Breast Cancer

Introduction: Inflammatory breast cancer (IBC) is an aggressive form of breast cancer with a dismal clinical outcome. In the past we showed that IBC is characterized by a specific gene expression pattern. In this study, we investigate if microRNAs (miRNAs) are responsible for the specific IBC gene signature.Materials and methods: 377 miRNAs were profiled in 20 IBC tumor samples and 50 non-stage matched nIBC tumour samples using the human MicroRNA A Array Set version 2.0 (Applied Biosystems). The IBC and nIBC study populations are matched for tumor grade and ER status. All miRNAs with Ct-values less than 35 in 25% of the samples were included for analysis. Data normalization was performed relative to the median miRNA expression level per sample and expression values were log2-transformed. Principal component analysis (PCA) was performed to identify metagenes of miRNAs, associated with the IBC phenotype. Relevant metagenes were compared with prognostic/predictive gene signature-classifications (wound healing response, invasiveness gene signature, 70-gene prognostic signature, genomic grade index, recurrence score, HOXB13/IL17RB-expression ratio and the molecular breast cancer subtypes). Data were validated by analysing relevant miRNA target gene sets on an IBC/nIBC gene expression data set.Results: Using PCA, we identified a metagene associated with the IBC phenotype (Hazard Ratio: 4.500; P=0.011). This metagene was also significantly associated with the Luminal B phenotype, the IBC signature and with an elevated HOXB13/IL17RB-expresion ratio (range Rs = 0.302 – 0.366; P&lt;0.05). MiRNAs significantly (FDR&lt;0.1) associated with this metagene were: miR29A, miR544, miR574-3p, miR548C-3p, miR451, miR548B-5p, miR24, miR28-5p, miR137, miR302B, miR148A and miR302A (range Rs: -0.367 – 0.307). Cluster analysis using this miRNA signature identified two sample clusters, one containing 70% of the IBC samples and a second one containing 64% of the nIBC samples (Pearson X2; P=0.021). Using gene set enrichment analysis for miR24-, miR28-, miR29A-, miR137-, miR148A-, miR302A- and miR302B target gene sets, we confirmed the differential expression for the above mentioned miRNAs (P&lt;0.01) except for miR28. Using Oncomine analyses we were able to associate the identified miRNAs with NFkB activation (miR29, miR148), steroid receptor signalling (miR302A, miR302B, and miR137), cell adhesion (miR29), stem cell signalling (miR137, miR28) and regulation of the extracellular matrix composition (miR29, miR148).Discussion: Through PCA we identified a miRNA signature associated with IBC. The miRNA signature was partly validated on the gene expression level. Interestingly, most identified miRNAs regulate biological processes previously associated with IBC through gene expression analysis, confirming our results also at the biological level. The association of the IBC-specific miRNA-metagene with the Luminal B phenotype and elevated HOXB13/IL17RB-expression ratios confirms our data that ER+ IBC samples, which constitute the majority of the present IBC study population, generally belong to the Luminal B subtype and are associated with resistance to endocrine therapy.

Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 6119.

A Phase II Study of the Combination of Endocrine Treatment and Bortezomib in Patients with Endocrine Resistant Metastatic Breast Cancer

Background: The introduction of anti-hormonal treatment has been a major revolution in breast cancer management. The majority of patients with metastatic hormone receptor-positive breast cancer eventually suffer from progression of their disease despite different types of anti-hormonal treatment. Preclinical studies have indicated bidirectional inhibitory interactions between ER and NF-kappaB, governing in part endocrine-resistance and enhanced growth. The hypothesis that inhibition of NF-kappaB activation by a proteasome inhibitor might reverse the sensitivity to endocrine therapy was the rationale to initiate a phase II trial.Aim, Material and Methods: The aim is to investigate whether the addition of open label bortezomib to either a SERM or an AI will result in documented activity in patients with progressive and measurable disease on the identical endocrine agent. This endpoint is evaluated according to RECIST criteria every 8 weeks. The patients are stratified into 2 treatment groups, according to their current endocrine treatment either tamoxifen or an AI. Bortezomib is administered on days 1, 8, 15, 21 of a 6 week regimen at a dose of 1.6 mg/sqm on each treatment day. Consecutive tumour biopsies (if accessible) and blood samples are collected for translational purposes. Clinical benefit was predefined by the patients obtaining at least either stable disease, or a partial or a complete response according to RECIST criteria, lasting for at least four weeks. A two-stage statistical approach showed that this should at least occur in 1 patient in the first cohort of 14 patients, prior to further accrual.Results: At present N=9 patients have been enrolled. Eight patients received AI+bortezomib, while one received TAM+bortezomib. N=5/9 patients had progressive disease, N=4/9 patients had stable disease of which two patients (N=2/9) had stable disease continuing for more than 4 weeks. There were no objective antitumour responses observed. N=4/9 had grade III diarrhoea. Median time to treatment failure was 69 days [35-140], either due to toxicity (N=3/9) or (eventual) progression (N=6/9).Conclusions: Preliminary results shows that the clinical benefit rate is 22% (N=2/9). Although preliminary, these results warrant further accrual and suggest that the biological hypothesis seems clinically valid. Further recruitment is ongoing.

Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 4099.

A microRNA Expression Profile Consisting of 15 microRNAs, Including miR205, Is Associated with Poor Prognosis in Breast Cancer

Introduction: MicroRNAs (miRNA) are a class of non-coding RNAs able to regulate gene expression at the post-transcriptional level. In breast cancer, levels of specific miRNAs differ between malignant and normal breast tissue and are able to classify tumors according to clinicopathologic variables. This highlights the potential of miRNAs as novel prognostic and/or predictive indicators. In this study we sought for miRNAs denoting poor prognosis in breast cancer.Materials and methods: 377 miRNAs were profiled in 70 breast tumor samples using the human MicroRNA A Array Set version 2.0 (Applied Biosystems). All miRNAs with Ct-values less than 35 in 25% of the samples were included for analysis. Data normalization was performed relative to the median miRNA expression level per sample and expression values were log2-transformed. Principal component analysis (PCA) was performed to identify metagenes of miRNAs associated with clinicopathological variables (TNM-status, tumor stage, histological grade, ER-, PR-, ErbB2- and P53-status) and prognostic/predictive gene signature-classifications (wound healing response, invasiveness gene signature, 70-gene prognostic signature, genomic grade index, recurrence score, HOXB13/IL17RB-expression ratio and the molecular breast cancer subtypes). Results were validated by investigating relationships between the expression of a relevant miRNA target gene signature and clinicopathological variables in 5 publicly available breast cancer gene expression data sets.Results: Using PCA-analysis we identified a metagene significantly associated with the Luminal B phenotype, an elevated genomic grade index, an elevated recurrence score, an activated wound healing response, the invasiveness gene signature and poor prognosis according to the 70-gene prognostic profile (range Rs: 0.325-0.372; P&lt;0.05). Using multivariate regression analysis we demonstrated that this metagene was also associated with loss of PR expression (Hazard Ratio (HR): 9.00; P=0.0001) and the presence of metastases at time of diagnosis (HR: 18.9; P=0.0002). MiRNAs significantly (FDR&lt;0.1) associated with this metagene were: miR205, miR548C-5p, miR548D-5p, miR187, miR671-3p, miR492, miR365, miR499-5p, miR548D-3p, miR615-3p, miR193A, miR589, miR660, miR219-1-3p, miR888 (range Rs: -0.415 – 0.456). At the gene expression level, a miR205 target gene signature, composed of 173 unique genes, was associated with relapse-free survival (range HR: 1.225 – 1.387; P&lt;0.01) and distant metastasis-free survival (HR: 3.950; P=0.006) in respectively 3 and 1 independent breast cancer data set(s).Discussion: Through principal component analysis we identified a miRNA signature associated with poor prognosis in breast cancer. This signature was composed of 15 individual miRNAs, including miR205 which is known for its role in epithelial-to-mesenchymal transition and the induction of stem cell characteristics. The association of a miR205 target gene signature with relapse-free and distant metastases-free survival confirms our results on the gene expression level.

Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 4062.

Prognostic Significance of Real-Time RT-PCR Detection of Disseminated Tumour Cells in Bone Marrow and Circulating Tumour Cells in Patients with Breast Cancer

Background: Despite optimal staging and treatment, up to 40% of stage I and II breast cancer (BC) patients will develop recurrent disease over time. These patients are believed to have disseminated tumour cells (DTC) at the time of diagnosis. Detection of minimal disease in bone marrow (BM) has been suggested to be a more direct approach to select metastasis-prone patients among this 'good prognosis group'. Peripheral blood (PB) sampling however is more convenient. The aim of this study was to evaluate whether the detection of DTC in either PB or BM predicts overall survival (OS). The initial analysis was published with a mean follow up time of 786 days (Benoy et al., BrJC 2006). We now report on these data after a mean follow up of nearly 5 years.Material and methods: PB and BM samples were collected from 148 patients with primary (M0, n=116) and metastatic (M+, n=32) BC before the initiation of any local or systemic treatment. PB of healthy volunteers and BM of patients with a nonmalignant breast lesion or a haematological malignancy served as control group. DTC were detected by measuring relative gene expression (RGE) for cytokeratin 19 (CK19) and mammaglobin (MAM), using a quantitative RT-PCR detection method. The 95 percentile of the RGE for CK19 and MAM of the control group was used as cutoff to determine elevation in BC patients. Kaplan-Meier analysis was used to predict OS.Results: Mean follow up time was 1518 days (+/- 719). Elevated CK19 expression was detected in 42 (28%) BM samples and in 22 (15%) PB samples. MAM expression was elevated in 20% (both PB and BM) of the patients with BC. There was a 68% (CK19) and 75% (MAM) concordance between PB and BM samples when classifying the results as either positive or negative. Patients with an elevated CK19 or MAM expression in BM had a worse OS than patients without elevated expression levels (p=0.002 (CK19) and p=0.001 (MAM)). For PB, no statistical significant difference in OS was observed between patients with or without elevated CK19 (p=0.227), but a strong trend for predicting OS was observed according to MAM status (p=0.054). Separate analyses of M0 and M+ patients revealed only a marked difference in OS according to BM CK19 in the M+ patient group. In M0 patients disease free survival (DFS) was not significantly predicted by CK19 and/or MAM status in BM alone (p=0.173 (CK19), p=0.219 (MAM)), but the presence of the double positive phenotype showed a trend for predicting DFS (p=0.059).Conclusions: DTC measured as elevated CK19 or MAM mRNA expression, could be detected in both PB and BM of patients with BC. Only the presence of DTC in BM was highly predictive for OS. However, with longer follow up differences in OS between patients with or without elevated CK19 and particularly MAM expression in PB also tend to become more significant. Furthermore, on the long term, double positivity for CK19/MAM in BM seems to predict DFS in patients with localized BC.

Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 3019.