Abstract 3038: Characterization of ZHX1 in node-negative breast cancer

Abstract

Abstract Women with breast cancer but without local metastasis to the axillary lymph nodes (ANN) have a good prognosis. However, 20 to 30% of patients with ANN breast cancer will still experience recurrence and distant metastases. Lymphatic invasion (LVI) is an important prognostic factor for ANN breast cancer. Therefore, LVI status was incorporated to provide a unique approach to identify novel genes related to outcome in ANN breast cancer. Gene expression microarrays were used to discriminate between tumors 1) with or without LVI (LVI+ or LVI-, respectively) and 2) from patients who experienced early recurrence (within 4 years) and those who were disease-free (for at least 10 years). Biostatistical analyses were performed to compile a list of statistically significant genes common to both comparisons. Zinc fingers and homeoboxes 1 (ZHX1) was identified as a candidate gene involved in LVI and associated with early recurrence of ANN breast cancer. Real-time RT-PCR (qPCR) was performed to quantify ZHX1 expression in a subset of cell lines and tumor samples. ZHX1 is expressed at different levels, mostly at an intermediate level in the tumors. A more network-based approach was used to examine biological pathways that may be associated with this poor prognosis. We discovered that ZHX1 may be involved in transcription, signaling, metabolism, and development, which is consistent with previous findings. ZHX1 binds to the other two members of the ZHX family, ZHX2 and ZHX3. All three members bind to the activation domain of the alpha subunit of nuclear transcription factor γ (NF-γ). NF-γ activates transcription of several genes, including the cell cycle progression gene, cell division cycle 25 homolog C (CDC25C). However, ZHX2 represses promoter activity of CDC25C, which would prevent cells from progressing into mitosis. Since ZHX1 binds to ZHX2 and NF-γ, this suggests that ZHX1 may be involved in the cell cycle. ZHX1 is significantly over-expressed in LVI+ tumors and in those from patients who experienced early recurrence of ANN breast cancer. The potential role of ZHX1 in the cell cycle may be associated with this poor prognosis. Gene and protein expression of ZHX1 and its candidate interactors are being quantified in cell lines via qPCR and Western blotting, respectively, and potential correlations examined. Immunohistochemistry is being performed on tissue microarrays to observe ZHX1 protein levels and localization and correlate with gene expression. Cell lines are being transfected via vector- or siRNA- based methods to over-express or knock down ZHX1, respectively. Alterations in tumorigenicity are being investigated via MTT proliferation and migration and/or invasion assays. Findings may aid in determining which ANN breast cancer patients may benefit from systemic therapy and identifying novel targets for cancer therapeutics. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 3038. doi:10.1158/1538-7445.AM2011-3038