Unknown,Transcriptomics,Genomics,Proteomics

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Co-targeting of the PI3K pathway improves the response of BRCA1 deficient breast cancer cells to PARP1 inhibition

ABSTRACT: Although pre-clinical and clinical studies on PARP1 inhibitors, alone and in combination with DNA-damaging agents, show promising results, further ways to improve and broaden the scope of application of this therapeutic approach are warranted. To this end, we have investigated the possibility of improving the response of BRCA1 mutant breast cancer cells to PARP1 inhibition by co-targeting the PI3K pathway. The human breast cancer cell line MDA-MB-436, which lacks the expression of both BRCA1 and PTEN, was treated with the PARP1 inhibitor AG014699 as a single agent or in combination with the PI3K inhibitor LY294002 for 7 days. The human breast cancer cell line MDA-MB-436 was treated with the PARP1 inhibitor AG014699 as a single agent or in combination with the PI3K inhibitor LY294002 for 7 days. All treatments were performed in triplicates. Total RNA was extracted hybridized onto the Illumina HumanHT-12 v4.0 microarray platform.

ORGANISM(S): Homo sapiens

SUBMITTER: Ida Johansson

PROVIDER: E-GEOD-34817 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Project description:Abstract BACKGROUND: The basal-like breast cancer (BLBC) subtype is characterized by positive staining for basal mammary epithelial cytokeratin markers, lack of hormone receptor and HER2 expression, and poor prognosis with currently no approved molecularly-targeted therapies. The oncogenic signaling pathways driving basal-like tumorigenesis are not fully elucidated. METHODS: One hundred sixteen unselected breast tumors were subjected to integrated analysis of phosphoinositide 3-kinase (PI3K) pathway related molecular aberrations by immunohistochemistry, mutation analysis, and gene expression profiling. Incidence and relationships between molecular biomarkers were characterized. Findings for select biomarkers were validated in an independent series. Synergistic cell killing in vitro and in vivo tumor therapy was investigated in breast cancer cell lines and mouse xenograft models, respectively. RESULTS: Sixty-four % of cases had an oncogenic alteration to PIK3CA, PTEN, or INPP4B; when including upstream kinases HER2 and EGFR, 75 % of cases had one or more aberration including 97 % of estrogen receptor (ER)-negative tumors. PTEN-loss was significantly associated to stathmin and EGFR overexpression, positivity for the BLBC markers cytokeratin 5/14, and the BLBC molecular subtype by gene expression profiling, informing a potential therapeutic combination targeting these pathways in BLBC. Combination treatment of BLBC cell lines with the EGFR-inhibitor gefitinib plus the PI3K pathway inhibitor LY294002 was synergistic, and correspondingly, in an in vivo BLBC xenograft mouse model, gefitinib plus PI3K-inhibitor PWT-458 was more effective than either monotherapy and caused tumor regression. CONCLUSIONS: Our study emphasizes the importance of PI3K/PTEN pathway activity in ER-negative and basal-like breast cancer and supports the future clinical evaluation of combining EGFR and PI3K pathway inhibitors for the treatment of BLBC. Gene expression profiles were generated for 95 breast tumors using Agilent Human 44K v5 microarrays following the manufacturer protocol. Stratagene Universal Human Reference RNA was used as the common control sample.

Project description:This experiment is part of the FunGenES project (FunGenES - Functional Genomics in Embryonic Stem Cells partially funded by the 6th Framework Programme of the European Union, http://www.fungenes.org).The experiment was conducted at the Unyversity of Bath, Bath, UK. Aim is to identify genes regulated by PI3K-dependent signaling in undifferentiated ES cells. Materials and methods: E14tg2a cell line was used. Cells were cultured in Knock-out DMEM supplemented with 15% (v/v) Knock-out serum replacement, 1000U/ml LIF, 2mM glutamine, 50 ?M 2-mercaptothanol and 1x NEAA (as described in Handbook of work methods, 4.3.1.1). Cells were plated at 5x105 per 10cm gelatin-coated TC dish for 24h. ES cells were then starved for 24h in media lacking LIF and pre-incubated for 30 minutes with 5 <B5>M LY294002 (the concentration of this PI3K inhibitor that we have shown to perturb self-renewal in the presence of LIF and which knocks down PI3K signals) or DMSO alone. Cells were then stimulated with 103U/ml mLIF (Chemicon) for 2h (which gave maximal activation of STAT3), 24h, 48h or 72h.</p>\n<h3>Relationships between samples</h3>\n <p ALIGN="JUSTIFY">Samples were either maintained in LIF or LIF plus LY294002 (PI3K inhibitor) for the required treatment times.</p>\n<h3>Treatments</h3>\n <p ALIGN="JUSTIFY">Treatment times with PI3K inhibitor LY294002 at 5 <B5>M <96> 2h (n=5), 24h (n=3), 48h (n=3), 72h (n=3). DMSO was used as vehicle alone treatment control.</p>\n<h3>Culture conditions</h3>\n <p ALIGN="JUSTIFY">Gelatin-coated TC dishes (Nunc)</p>\n<h3>RNA isolation method</h3>\n <p ALIGN="JUSTIFY">RNA Easy with on-column DNase treatment</p>\n<h3>Experimental description</h3>\n <p ALIGN="JUSTIFY">This information is included above. Briefly, E14tg2a ES cells were either maintained in LIF or LIF plus LY294002 (5 <B5>M) for 2, 24, 48 or 72 hours, after which RNA was extracted from each sample and sent for expression profiling. During this time-course, only 72h time points plus LY294002 showed phenotypic evidence of differentiation. </p>\n

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Co-targeting of the PI3K pathway improves the response of BRCA1 deficient breast cancer cells to PARP1 inhibition

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