title: Analysing the mutational status of PIK3CA in circulating tumor cells from metastatic breast cancer patients.
abstract: The 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(®). 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 enriched from peripheral blood and can be easily adopted for analysing further therapeutically relevant SNPs.
authors.affiliation: Department of Obstetrics and Gynecology, Eberhard Karls University of Tuebingen, Calwerstr. 7, 72076 Tuebingen, Germany. Electronic address: Helschn84@gmail.com.
authors.forename: Helen
authors.initials: H
authors.lastname: Schneck
authors.forename: Christina
authors.initials: C
authors.lastname: Blassl
authors.forename: Franziska
authors.initials: F
authors.lastname: Meier-Stiegen
authors.forename: Rui Pedro
authors.initials: RP
authors.lastname: Neves
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Janni
authors.forename: Tanja
authors.initials: T
authors.lastname: Fehm
authors.forename: Hans
authors.initials: H
authors.lastname: Neubauer
mesh_terms: D000328:Adult; D000368:Aged; D000483:Alleles; D001943:Breast Neoplasms / Q000150:complications / Q000235:genetics*; D058534:Class I Phosphatidylinositol 3-Kinases; D004252:DNA Mutational Analysis; D005260:Female; D006801:Humans; D008875:Middle Aged; D009154:Mutation; D009360:Neoplastic Cells, Circulating / Q000378:metabolism; D019869:Phosphatidylinositol 3-Kinases / Q000235:genetics*; D020641:Polymorphism, Single Nucleotide / Q000235:genetics
chemical_list: D019869:Phosphatidylinositol 3-Kinases; D058534:Class I Phosphatidylinositol 3-Kinases; C484760:PIK3CA protein, human
keywords: 4,6-diamidino-2-phenylindole; APC; CK-PE; CS; CTC(s); Catalytic subunit alpha; CellSearch(®); Circulating tumor cells; DAPI; DTCs; ER; FITC; HER2; Metastatic breast cancer; PI3K; PIK3CA; PIK3CA mutations; PR; PTEN; Phosphatidylinositol-4,5-bisphosphate 3-kinase; SNP; SNaPshot assay; WGA; Whole Genome Amplification; allophycocyanin; circulating tumor cell(s); cytokeratin-phycoerythrin; disseminated tumor cells; estrogen receptor; fluorescein-isothiocyanate; human epidermal growth factor receptor 2; phosphatase and tensin homolog; phosphatidylinositol-3-kinase; progesterone receptor; single nucleotide polymorphism
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