Abstract 3077: Nek3/Vav2 modulation of the expression of genes involved in breast cancer pathogenesis

Abstract

Abstract The pituitary hormone prolactin (PRL) is generally recognized for its role in breast growth and differentiation; however, a role for PRL in the pathogenesis of breast cancer has emerged from epidemiological studies and basic science research using both human breast cancer cells and animal models. Activation of the prolactin receptor (PRLr) by PRL contributes to the growth, survival, and motility of human breast cancer cells. PRLr stimulation by PRL results in the activation of multiple signaling complexes including serine/threonine kinase Nek3 and guanine nucleotide exchange factor Vav2. Nek3 is necessary for the activation of Vav2, and Nek3 knockdown results in decreased cytoskeletal re-organization, cell motility, and cell invasion in PRL-stimulated human breast cancer cells. The overexpression of a kinase inactive form of Nek3 in human breast cancer cells results in increased apoptosis, indicating a pro-survival function for Nek3. Furthermore, Nek3 expression is increased in malignant vs. normal human breast tissue. These data make the Nek3/Vav2 complex an interesting target for novel breast cancer therapeutics. To this end, a greater understanding of the role of Nek3/Vav2 in breast cancer pathogenesis is necessary. We hypothesized that the Nek3/Vav2 complex modulates PRL-driven expression of genes involved in the pathogenesis of breast cancer. In these studies, luciferase assays and quantitative PCR were used to evaluate the effects of gain- or loss-of-function of Nek3/Vav2 on the expression of CISH (cytokine-inducible SH2-containing protein). Gain- or loss-of-function of Nek3/Vav2 was found to alter the expression of CISH in response to PRL in both MCF7 and T47D human breast cancer cell lines. The CISH promoter has 4 binding sites for the transcription factor Stat5, which is known to contribute to malignant transformation and tumor growth in breast cancer. Luciferase assay showed that gain- or loss-of-function of Nek3 was also found to alter the activation of a reporter construct containing the lactogenic hormone response element which consists of six tandem Stat5 DNA-binding elements. This suggests that Nek3/Vav2 modulates the PRL-driven expression of CISH by regulating activity of the transcription factor Stat5. Gain- or loss-of-function of Nek3/Vav2 was not found to alter the subcellular localization of Stat5 in response to PRL. Ongoing studies are examining the mechanism of Nek3/Vav2 modulation of PRL-responsive gene expression in breast cancer cells. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 3077. doi:1538-7445.AM2012-3077