Down-regulation of vitamin D receptor in mammospheres: implications for vitamin D resistance in breast cancer and potential for combination therapy

• Published in: PloS one Vol. 8; no. 1; p. e53287
• Main Authors: Pervin, Shehla, Hewison, Martin, Braga, Melissa, Tran, Lac, Chun, Rene, Karam, Amer, Chaudhuri, Gautam, Norris, Keith, Singh, Rajan
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 14.01.2013; Public Library of Science (PLoS)
• Subjects: Aldehyde dehydrogenase; Animals; Antineoplastic Combined Chemotherapy Protocols - pharmacology; Antineoplastic Combined Chemotherapy Protocols - therapeutic use; Biology; Bone surgery; Breast cancer; Breast Neoplasms - drug therapy; Breast Neoplasms - enzymology; Breast Neoplasms - genetics; Breast Neoplasms - pathology; Cancer; Cancer prevention; CD44 antigen; Cell cycle; Cell Line, Tumor; Cell Separation; Cholera; Combination therapy; Combined treatment; Comparative analysis; Dephosphorylation; Dihydroxyvitamin D; Down-regulation; Down-Regulation - drug effects; Down-Regulation - genetics; Drug delivery; Drug Resistance, Neoplasm - drug effects; Drug Resistance, Neoplasm - genetics; Drugs; Epidermal growth factor; Epithelial-Mesenchymal Transition - drug effects; Epithelial-Mesenchymal Transition - genetics; Extracellular signal-regulated kinase; Female; Gene Expression Profiling; Gene Expression Regulation, Neoplastic - drug effects; Gynecology; H-Ras protein; Humans; Hyaluronan Receptors - metabolism; Insulin; Intercellular Signaling Peptides and Proteins - pharmacology; Internal medicine; Kinases; Mammary Glands, Human - drug effects; Mammary Glands, Human - pathology; MAP kinase phosphatase; Medical prognosis; Medicine; Mice; Mice, Nude; Neoplastic Stem Cells - drug effects; Neoplastic Stem Cells - metabolism; Neoplastic Stem Cells - pathology; Nitric oxide; Nitric Oxide - pharmacology; Obstetrics; Orthopedics; Overexpression; Receptors, Calcitriol - genetics; Retinoid X Receptors - metabolism; Rodents; Science; Signaling; siRNA; Snail Family Transcription Factors; Spheroids, Cellular - drug effects; Spheroids, Cellular - metabolism; Spheroids, Cellular - pathology; Stem cell transplantation; Stem cells; Therapy; Transcription factors; Transcription Factors - metabolism; Tumor cell lines; Tumors; Up-Regulation - drug effects; Up-Regulation - genetics; Vitamin D; Vitamin D - analogs & derivatives; Vitamin D - pharmacology; Vitamin D - therapeutic use; Vitamin D receptors; Xenograft Model Antitumor Assays; Xenografts; Los Angeles California; United States > US; California
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0053287

Vitamin D signaling in mammary cancer stem cells (MCSCs), which are implicated in the initiation and progression of breast cancer, is poorly understood. In this study, we examined vitamin D signaling in mammospheres which are enriched in MCSCs from established breast cancer cell lines. Breast cancer cells positive for aldehyde dehydrogenase (ALDH(+)) had increased ability to form mammospheres compared to ALDH(-) cells. These mammospheres expressed MCSC-specific markers and generated transplantable xenografts in nude mice. Vitamin D receptor (VDR) was significantly down-regulated in mammospheres, as well as in ALDH(+) breast cancer cells. TN aggressive human breast tumors as well as transplantable xenografts obtained from SKBR3 expressed significantly lower levels of VDR but higher levels of CD44 expression. Snail was up-regulated in mammospheres isolated from breast cancer cells. Inhibition of VDR expression by siRNA led to a significant change in key EMT-specific transcription factors and increased the ability of these cells to form mammospheres. On the other hand, over-expression of VDR led to a down-regulation of Snail but increased expression of E-cad and significantly compromised the ability of cells to form mammospheres. Mammospheres were relatively insensitive to treatment with 1,25-dihydroxyvitamin D (1,25D), the active form of vitamin D, compared to more differentiated cancer cells grown in presence of serum. Treatment of H-Ras transformed HMLE(HRas) cells with DETA NONOate, a nitric oxide (NO)-donor led to induction of MAP-kinase phosphatase -1 (MKP-1) and dephosphorylation of ERK1/2 in the mammospheres. Combined treatment of these cells with 1,25D and a low-concentration of DETA NONOate led to a significant decrease in the overall size of mammospheres and reduced tumor volume in nude mice. Our findings therefore, suggest that combination therapy using 1,25D with drugs specifically targeting key survival pathways in MCSCs warrant testing in prospective clinical trial for treatment of aggressive breast cancer.