Abstract 856: High expression of DUSP4 in ER-negative breast cancer cells suppresses growth and invasion.
Authors: Mazumdar Abhijit , Den Hollander Petra , Poage Graham , Hill Jamal , Zhang Yun , Tsimelzon Anna , Hilsenbeck Susan , Chang Jenny , Mills Gordon , Brown Powel H. 
Published: August 2014

Background: Estrogen receptor (ER) -negative breast cancers are poor prognosis tumors that occur more commonly in young women. Current treatments for ER-negative tumors include cytotoxic chemotherapy, or for those ER-negative breast cancers that overexpress HER2, the anti-HER2 antibody herceptin. Similar therapy for ER-negative, Her2 negative tumors, particularly for (triple-negative breast cancers) is urgently needed. In this project, we investigated whether phosphatases that are differentially expressed in ER-negative as compared to ER-positive breast cancers. We hypothesized that: (1) the specific phosphatases that govern the growth of ER-negative cancers are different from those of ER-positive cancers, (2) Induced expression of some of those phosphatases that are lowly expressed in ER-negative breast cancers will suppress the growth and invasion of ER-negative breast cancers.

Methods: Using 102 human breast tumors (57 ER-positive & 45 ER-negative) from the neo-adjuvant studies from the Baylor Breast Center tumor bank, we isolated RNA and performed Affymetrix microarray studies. cDNA was synthesized and Biotin-labeled and hybridized onto an Affymetrix HGU133A GeneChipTM. Statistical analysis was done with dChip software, and phosphatases more highly (&gt;1.5 fold; FDR &lt;0.05) or lowly (&lt;0.66-fold; FDR&lt;0.05) expressed in ER-negative breast cancers as compared to ER-positive breast cancers were selected for further study. Regulated expression of DUSP4 in breast cancer cells was achieved using a Tet-regulated vector (Tet on Gateway System). Cell growth Soft agar and invasion assays were performed using previously published protocols. Mouse xenograft experiments were performed by injecting inducible DUSP4-clones and vector- clones in mammary fat pad of nu/nu and SCID mice and to induced DUSP4 expression were treated with doxycycline when tumor volume reached 50 mm3 and tumor growth was measured.

Results: We identified 20 highly-expressed (&gt;1.5 fold; FDR=0.05), and 29 lowly-expressed (&lt;0.66-fold; FDR&lt;0.05) phosphatases in ER-negative breast cancers. We selected the lowly expressed phosphatase DUSP4 for further study. Induced expression of DUSP4 in ER-negative cells inhibited anchorage-dependent and independent growth but had no effect on ER-positive cell. Induced expression of DUSP4 also suppressed the invasion of MDA-MB-231 and SUM159 cells. DUSP4 expression also inhibited MDA-MB 231 and SUM159 cells growth in vivo.

Conclusions: We identified a set of highly and lowly expressed phosphatases in ER-negative breast cancers as compared to ER-positive cancers. Overexpression of DUSP4 in ER-negative breast cancer cells inhibits growth and invasion of these cells. By identifying the molecules that regulate breast cancer cells growth we are identifying potential new targets for the treatment of these aggressive ER-negative breast cancers. Supported by Komen Promise grant KG081694 (PHB).

Citation Format: Abhijit Mazumdar, Petra Den Hollander, Graham Poage, Jamal Hill, Yun Zhang, Anna Tsimelzon, Susan Hilsenbeck, Jenny Chang, Gordon Mills, Powel H. Brown. High expression of DUSP4 in ER-negative breast cancer cells suppresses growth and invasion. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 856. doi:10.1158/1538-7445.AM2013-856