Abstract 1236: A gemini vitamin D analogue, BXL0124, represses mammosphere formation and decreases expression of stem cell markers in MCF10DCIS breast cancer cells

Proceedings: AACR Annual Meeting 2014; April 5-9, 2014; San Diego, CA It has been suggested that cancer stem cells (CSCs), which represent a subset of tumor cells, are responsible for the possible origination and maintenance of tumors. Moreover, CSCs are believed to be the main cause of progression to metastasis and recurrence of cancer because of their tumor-initiating abilities and resistance to conventional therapies. Ductal carcinoma in situ (DCIS) is an early precursor in breast carcinogenesis which progresses to invasive ductal carcinoma (IDC). The involvement of CSCs in the progression of DCIS to IDC has yet to be elucidated. In order to investigate the role of CSCs in DCIS progression to IDC, we utilized the MCF10DCIS.com cell line in the mammosphere cell culture system, which enriches for mammary progenitor cells and mammary CSCs. We have previously reported that a novel Gemini vitamin D analog, 1α,25-dihydroxy-20R-21(3-hydroxy-3-deuteromethyl-4,4,4-trideuterobutyl)-23-yne-26,27-hexafluoro-cholecalciferol (BXL0124), inhibits the progression of DCIS to IDC. Therefore, we have determined whether BXL0124 plays a role in regulating the CSC or progenitor cell populations, resulting in reduced tumorigenicity. MCF10DCIS.com cells were plated in ultra-low attachment plates and treated with BXL0124 or 1α25(OH)2D3 over the course of 1, 3 and 5 days. Starting at day 2, MCF10DCIS.com cells began to form mammospheres of 100 µm in size. MCF10DCIS.com mammospheres showed enrichment in the CD44+/CD24- and the CD49f+/CD24- populations compared to monolayer cell culture. The phenotype of MCF10DCIS.com mammospheres showed a disorganized, undefined and irregular shape. However, when the MCF10DCIS.com mammospheres were treated with BXL0124 or 1α25(OH)2D3, mammospheres form a more organized, symmetrical and circular shape, which is similar to the phenotype of the spheres formed by the non-malignant, normal mammary epithelial cell line, MCF10A. In addition, the mammosphere forming efficiency (MFE) was decreased upon BXL0124 and 1α25(OH)2D3 treatment, showing that there is an inhibitory effect on mammosphere development. Treatment with BXL0124 repressed markers associated with the stem cell-like phenotype, such as CD44, Notch1 and JAG1. Furthermore, BXL0124 demonstrated the reduced expression of MMPs, such as MMP2, 9, 14, 15, and 16, in mammospheres, suggesting that BXL0124 reduces the tumorigenicity and invasive potential of MCF10DCIS.com cells by targeting the stem cell-like population. In conclusion, the Gemini vitamin D analog BXL0124 represses the CSC population, potentially contributing to the inhibition of the progression of DCIS to IDC. (This work was supported in part by the National Institutes of Health National Cancer Institute R01-CA127645 and the National Institute of Environmental Health Sciences Grant ES005022). Citation Format: Joseph Wahler, Hubert Maehr, Milan Uskokovic, Nanjoo Suh. A gemini vitamin D analogue, BXL0124, represses mammosphere formation and decreases expression of stem cell markers in MCF10DCIS breast cancer cells. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 1236. doi:10.1158/1538-7445.AM2014-1236