Abstract B52: Profiling of genes associated with sustained high calcium adaptation of invasive breast cancer cells
Authors: Sakwe Amos M. 
Published: August 2014

Younger African American and Hispanic patients are frequently diagnosed with highly invasive and metastatic breast cancers with poorer prognosis. The molecular mechanisms underlying the aggressiveness and in particular, race-related differences in progression of these cancers, remain poorly understood. Patients with advanced and metastatic breast cancer inevitably become hypercalcemic, but about 30% of most solid tumor cases develop this abnormal metabolic syndrome early in the course of the disease. The cancer-induced hypercalcemia (CIH) is primarily due to increased bone resorption that is provoked by tumor cell-derived osteolytic factors. In the CIH susceptible patients, it is expected that tumor progression may be accompanied by progressive severity of CIH. Here we examined the effects of sustained high (5 mM) Ca2+ on the growth of breast epithelial and breast cancer cells and attempted to identify the genes mediating high calcium adaptation of invasive breast cancer cells. We show that normal breast epithelial cells (184A1) and luminal breast cancer cells (MCF-7) grow poorly at high Ca2+ while triple negative breast cancer (TNBC) cells (MDA-MB-231, BT-549, HCC-1806) are to a greater extent high Ca2+ tolerant cell lines. To gain a better understanding of the mechanisms of sustained high calcium adaptation by TNBC cell lines, we examined the gene expression profiles of MDA-MB-231 cells maintained at high (5 mM) Ca2+ for 48 h. Cells maintained in complete medium containing 1 mM Ca2+ were used as controls. Analysis of the cDNA microarrays revealed that at least 111 genes were up regulated and 69 genes were down regulated at +/- 1.5 fold and p &lt; 0.05. Some of the most up- and down-regulated genes were validated by quantitative RT-PCR in MDA-MB-231, BT-549, HCC-1806 and MCF-7 cell lines. Among the up-regulated genes, we identified and validated the early response genes FOS and EGR1 as well as MAGEC2 (CT10), SERPINB2, NCF2, SCG5, IL11, IL24 and IL6. Among the consistently down-regulated genes were DNM1 and ITGB4. Interestingly, MCF-7 cells that express relatively low levels of the calcium sensing receptor (CaSR) and are sensitive to high Ca2+, did not show significant up regulation of FOS, EGR1 and MAGEC2. MAGEC2 is strongly expressed by HCC1806 and is remarkable induced by high Ca2+ in BT-549 cells. These data suggests that high Ca2+ adaptation of invasive breast cancer cells is mediated via the CaSR and initiated by the up regulation of early response genes and presumably sustained by the up regulation of tumor promoters and/or down regulation of tumor suppressors. Further studies are ongoing to determine how some of these genes mediate the high calcium response and their potential implication in breast cancer progression and outcomes.

Citation Format: Amos M. Sakwe. Profiling of genes associated with sustained high calcium adaptation of invasive breast cancer cells. [abstract]. In: Proceedings of the Third AACR International Conference on Frontiers in Basic Cancer Research; Sep 18-22, 2013; National Harbor, MD. Philadelphia (PA): AACR; Cancer Res 2013;73(19 Suppl):Abstract nr B52.