Abstract 3394: CITED2: A potential facilitator of breast cancer metastasis

Abstract

Abstract Metastasis is the ultimate cause of mortality in breast cancer patients. Critical to our ability to prevent and treat metastasis is the identification of the key factors mediating the metastatic process and the understanding of their biological function. Using a murine model of breast cancer metastasis, we recently identified the transcriptional co-activator CITED2 as a potential mediator of bone metastasis. Here, we further explore the potential role of CITED2 in facilitating metastasis using human breast cancer cells. First, we examined the expression of CITED2 mRNA in human breast cancer patient samples by qRT-PCR. Interestingly, CITED2 mRNA levels were significantly (p < 0.05) elevated in primary breast tumors from patients surviving less than 5 years from time of diagnosis (non-survivors, n = 8) relative to those who survived greater than 5 years (survivors, n = 11). Further, mRNA levels of CITED2 were significantly (p < 0.05) elevated in breast cancer metastases (n = 25) relative to both primary breast tumors from survivors and normal mammary organoids. Consistent with mRNA expression, CITED2 protein levels were elevated in primary breast tumors and metastases relative to normal mammary epithelium by immunohistochemical analysis. To investigate the function of CITED2 we generated cell lines in which CITED2 expression was stably increased (CITED2) or decreased (shCITED2) using the human breast cancer cell line MDA-MB-231. While increased expression of CITED2 did not affect cell proliferation in vitro by MTS assay, survival following intracardiac injection was significantly reduced (p < 0.01) suggesting that CITED2 may enhance the ability of cancer cells to survive and grow at secondary sites. Consistent with this hypothesis, we also observed enhanced osteolysis at sites of bone metastasis in animals harboring CITED2 cells relative to vector control. In contrast, stable reduction of CITED2 levels significantly (p < 0.05) inhibited cell proliferation in vitro by MTS assay, consistent with the transcriptional regulation of numerous genes controlling cell cycle events (eg. cyclin E, cdk1, p21, ATM) as observed by qRT-PCR. Moreover, reduced expression of CITED2 resulted in the reversion of MDA-MB-231 cells to a more epithelial-like phenotype as evidenced by a more cuboidal morphology under light microscopy. This observation was further supported by Western analysis demonstrating decreased protein expression of the mesenchymal marker vimentin and increased expression of the epithelial markers E-cadherin and claudin-3. Further, reduction of CITED2 expression inhibited invasive ability by Matrigel invasion assay, while increased levels of CITED2 enhanced invasion. Taken together, these data support a potential role for CITED2 in regulating the metastatic potential of breast cancer cells. Note: This abstract was not presented at the AACR 101st Annual Meeting 2010 because the presenter was unable to attend. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 3394.