Abstract
OBJECTIVES: Prevention of metastasis is of utmost importance for increasing survival in breast cancer patients. Oxygen tension is variable throughout tumors, creating regions of hypoxia that have been linked with poor cancer prognosis. Hypoxia increases glycolytic flux via hypoxia-inducible factor-1α (HIF1α), and can therefore alter growth and survival of cancer cells. Our objectives are to (1) characterize changes in metabolism and survival that occur when metastatic and non-metastatic mammary cancer cell lines are cultured in hypoxia, and (2) determine whether 1,25-dihydroxyvitamin D (1,25(OH)(2)D) reduces overall survival in hypoxia. METHODS: We utilized Wnt oncogene-driven murine mammary cancer cells that are non-metastatic (M-Wnt) or that preferentially metastasize to the lung in vivo (metM-Wnt(lung)). Viability of M-Wnt and metM-Wnt(lung) cells treated with 10 nM 1,25(OH)(2)D and/or 20 mM 2-deoxyglucose (2DG, an inhibitor of glycolysis) was measured with MTT. Expression of HIF1α protein was determined by Western blotting. RESULTS: We show that 1,25(OH)(2)D treatment significantly decreased viability of metastatic metM-Wnt(lung) cells grown in hypoxia by 41%, whereas viability of M-Wnt cells was not significantly impacted by 1,25(OH)(2)D treatment. Furthermore, treating cells with 2DG significantly decreased viability of both cells lines in hypoxia, with metM-Wnt(lung) cells being more sensitive to 2DG. Interestingly, 1,25(OH)(2)D treatment partially rescued M-Wnt cells by 22% and metM-Wnt(lung) cells by 24% when treated with 2DG in hypoxia. Finally, we show that M-Wnt cells have 1.9-fold increased expression of HIF1α protein compared to metM-Wnt(lung) cells when grown in hypoxia. CONCLUSIONS: Our results collectively suggest that non-metastatic M-Wnt cells are less sensitive to treatment with 1,25(OH)(2)D and 2DG in hypoxia than metastatic metM-Wnt(lung)cells. These data may be explained, in part, by elevated expression of HIF1α in M-Wnt cells, which may contribute to their improved survival in hypoxia. FUNDING SOURCES: National Institute of Health and USDA.