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Protein Tyrosine Phosphatase UBASH3B is Overexpressed in Triple-Negative Breast Cancer and Promotes Invasion and Metastasis

ABSTRACT: Efforts to improve the clinical outcome of highly aggressive triple-negative breast cancer (TNBC) have been hindered by the lack of effective targeted therapies. Thus, it is important to identify the specific gene targets/pathways driving the invasive phenotype to develop more effective therapeutics. Here we show that ubiquitin-associated and SH3 domain-containing B (UBASH3B), a protein tyrosine phosphatase, is overexpressed in TNBC, where it supports malignant growth, invasion, and metastasis largely through modulating epidermal growth factor receptor (EGFR). We also show that UBASH3B is a functional target of anti-invasive microRNA200a (miR200a) that is down-regulated in TNBC. Importantly, the oncogenic potential of UBASH3B is dependent on its tyrosine phosphatase activity, which targets CBL ubiquitin ligase for dephosphorylation and inactivation, leading to EGFR up-regulation. Thus, UBASH3B may function as a crucial node in bridging multiple invasion-promoting pathways, thereby providing a potential therapeutic target for TNBC.

ORGANISM(S): Homo sapiens

PROVIDER: GSE36693 | GEO | 2013/06/01

SECONDARY ACCESSION(S): PRJNA153615

REPOSITORIES: GEO

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Project description:Basal-like and triple negative breast cancer (TNBC) share common molecular features, poor prognosis and a propensity for metastasis to the brain. Amplification of EGFR occurs in ~50% of basal-like breast cancer and mutations in the epidermal growth factor receptor (EGFR) have been reported in up to ~ 10% of Asian TNBC patients. In non-small cell lung cancer several different mutations in the EGFR tyrosine kinase domain confer sensitivity to receptor tyrosine kinase inhibitors, but the tumourigenic potential of EGFR mutations in breast cells and their potential for targeted therapy is unknown. Constructs containing wild type, G719S or E746-A750 deletion mutant forms of EGFR were transfected into the ‘near normal’ MCF10A breast cells and their tumorigenic derivative, MCF10CA1a. These transfected lines were used to investigate the effects of EGFR over-expression and mutation on proliferation, migration, invasion, response to gefitinib, and tumour formation in vivo. We also carried out copy number analysis and whole exome sequencing of the MCF10A and MCF10CA1a cell lines. Both activating mutations of EGFR increased the proliferative ability of MCF10A and MCF10CA1a cell lines, and increased the anchorage-independent growth and sensitivity to gefitinib in MCF10A cells. In addition, the EGFR-E746-A750 deletion increased the migratory and invasive abilities of the MCF10CA1a cell line in vitro, and greatly increased the formation and growth of MCF10CA1a tumours in vivo. Compared to MCF10A cells, MCF10CA1a cells had large regions of gain on chromosome 9 and the long arm of chromosome 3, deletion in the short arm of chromosome 7, and mutations in many genes implicated in cancer. The EGFR E746-A750 deletion mutation, and to a lesser extent G719S, greatly enhance the oncogenic properties of MCF10A cell line, and increase sensitivity to gefitinib. Although the addition of EGFR E746-A750 renders the MCF10CA1a cells more tumourigenic in vivo it is not accompanied by increased sensitivity to gefitinib, perhaps because of additional mutations, including the PIK3CA H1047R mutation, that the MCF10CA1a cell line has acquired. Screening TNBC/basal-like breast cancer for EGFR mutations may prove useful for directing therapy but, as in non-small cell lung cancer cancer, accompanying mutations in PIK3CA may confer gefitinib resistance.

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Protein Tyrosine Phosphatase UBASH3B is Overexpressed in Triple-Negative Breast Cancer and Promotes Invasion and Metastasis

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