Metastatic breast cancer PIK3CA mutations SNaPshot assay A B S T R A C TThe frequently altered phosphatidylinositol-3-kinase (PI3K)/Akt signaling pathway is involved in the regulation of cellular processes required for breast carcinogenesis. The aim of the project was to develop a method to identify hotspot mutations in the PIK3CA gene in circulating tumor cells (CTCs) of metastatic breast cancer (metBC) patients.From 44 enrolled CTC-positive metBC patients a total number of 57 peripheral blood samples were analysed by CellSearch Ò . Genomic DNA of enriched CTCs was isolated, amplified and analyzed for PIK3CA mutations in exons 9 and 20 which lead to E542K, E545K or H1047R amino acid changes and result in increased PI3K activity. The mutations were detected by using SNaPshot-methodology comprising PCR amplification and single nucleotide primer extension.SNaPshot analysis was established using genomic DNA from different breast cancer cell lines and then successfully transferred to investigate blood samples and single cells. Overall, twelve hotspot mutations in either exon 9/E545K (6/12, 50%) or exon 20/H1047R (6/12, 50%) could be determined within 9 out of 57 (15.8%) blood samples from 7 out of 44 (15.9%) patients; CTC counts ranged from 1 to 9748. PIK3CA variants E542K, E545G and E545A were not detected.Analysing the PIK3CA genotype of CTCs has clinical relevance with respect to drug resistance, e.g. against HER2-targeted therapy. The herein described approach including SNaPshot technology provides a simple method to characterize hotspot mutations within CTCs Abbreviations: APC, allophycocyanin; CK-PE, cytokeratin-phycoerythrin; CS, CellSearch Ò ; CTC(s), circulating tumor cell(s); DAPI, 4,6-diamidino-2-phenylindole; DTCs, disseminated tumor cells; ER, estrogen receptor; FITC, fluorescein-isothiocyanate; HER2, human epidermal growth factor receptor 2; PI3K, phosphatidylinositol-3-kinase; PTEN, phosphatase and tensin homolog; PR, progesterone receptor; SNP, single nucleotide polymorphism; WGA, Whole Genome Amplification.* Corresponding author.
A fundamental and clinically important step during breast tumourigenesis is the transition from ductal carcinoma in situ (DCIS) to invasive ductal carcinoma (IDC). Improved knowledge of this transition from pre-invasive to invasive breast cancer will pave the way for novel preventative and therapeutic strategies. We have previously reported on differential expression of the miRNA hsa-miR-199a-5p in 15 matched pairs of DCIS and IDC areas isolated by laser capture microdissection (LCM) from formalin fixed and paraffin embedded (FFPE) breast cancer tissues using Illumina miRNA BeadChip microarray platform. Differential expression of hsa-miR-199a-5p was validated by quantitative RT-PCR in additional independent DCIS/IDC sample pairs from 25 breast cancer patients. Knock down of hsa-miR-199a-5p in invasive MDA-MB-231 and TMX2-28 breast cancer cells using a specific inhibitor significantly reduced invasiveness by approx. 73% and 71%, respectively (P <0.01 and P<0.05). Now we report on experiments to validate differential expression of hsa-miR-199a-5p using a new platform – NanoString® (nCounter® miRNA Expression Assay, NanoString Technologies®). The NanoString® System is an automated, digital detection and counting system which uses a novel barcoding technology to directly profile up to 800 miRNAs simultaneously from a single sample. Total RNA from 6 DCIS/IDC FFPE tumours was used for miRNA expression analysis. This analysis resulted in 10 differentially expressed miRNAs including hsa-miR-199a-5p which is upregulated in IDC (P <0.05). Besides hsa-mir-199a-5p, hsa-miR-222 is significantly differentially expressed between DCIS and IDC which could be found in both expression data sets (Illumina® and NanoString®). In this project we identified candidate progression-associated miRNAs which are differentially expressed between DCIS and IDC. Hsa-miR-199a-5p was validated in an independent sample cohort and its expression was further verified using the new miRNA expression analysis platform NanoString®. Hsa-miR-199a5-p is influencing in vitro cell invasiveness and may therefore be a potential drugable regulator of tumour progression and invasion in breast cancer. Citation Format: Fehm T, Schultz S, Bartsch H, Petat-Dutter K, Kahlert S, Sotlar K, Niederacher D, Neubauer H. Verification of the breast cancer progression-associated miRNA hsa-miR-199a-5p using NanoString® platform. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P4-09-09.
Circulating tumor cells (CTCs) are the potential precursors of metastatic disease. Many assays have been established for the enumeration of CTCs. However, major limitations include the reliance on the expression of the cell surface marker epithelial cell adhesion molecule (EpCAM). These approaches may not detect CTCs that either express no/low levels of EpCAM or undergo epithelial-to-mesenchymal transition (EMT). We present an enrichment strategy combining different antibodies specific for surface proteins and extracellular matrix (ECM) components to capture EpCAMneg cell lines and EpCAMneg CTCs from EpCAM-depleted breast cancer blood samples. Expression of proteins (Trop2, CD49f, cMet, CK8, CD44, ADAM8, CD146, TEM8, CD47) was verified by immunofluorescence on EpCAM-positive (e.g. MCF7, SKBR3) and -negative (MDA-MB-231) breast cancer cell lines; antibodies and ECM proteins (e.g. hyaluronic acid (HA), collagen I, laminin) were further spotted in a single- and multi-arrayed format onto glass slides (Schott, NEXTERION® AL) and coupled to immunomagnetic beads (Dynabeads/Adembeads). Tumor cell adhesion of EpCAMpos/neg cell lines was visualized by Coomassie/MitoTracker; EpCAMneg CTCs enriched via functionalized Adem-/Dynabeads were identified by immunofluorescence staining for anti-pan-Cytokeratin(CK)-FITC/anti-CD45 AF647/DAPI and quantified manually by microscopy. Regarding cell lines, marginal binding of EpCAMneg MDA-MB-231 cells to EpCAM-antibodies could be observed. Efficient adhesion/capturing of EpCAMneg cells could be achieved via HA and immobilized antibodies against CD49f and Trop2. By analyzing 29 EpCAM-depleted fractions from 25 metastatic breast cancer patients, we were able to identify EpCAMneg CTCs in 69% of the samples [range 1-24] applying Trop2, CD49f, cMet, CK8 and/or HA magnetic enrichment. Accessorily, EpCAMneg dual-positive (CKpos/CD45pos) cells could be traced in 28 out of 29 samples [range 1-480]. Herein, we demonstrate an enhanced enrichment strategy to optimize capturing of EpCAMneg CTCs by targeting various cell surface antigens with antibody mixtures and ECM components. Thereby, potential relevant CTCs can be gathered and subjected to subsequent molecular analysis. Citation Format: Fehm T, Schneck H, Gierke B, Pawlak M, Templin M, Niederacher D, Neubauer H. EpCAM-independent enrichment approach for isolation of circulating tumor cells (CTCs) in breast cancer - What can be found in the EpCAM-depleted fraction?. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P2-02-13.
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