Down-regulation of vitamin D receptor in mammospheres: implications for vitamin D resistance in breast cancer and potential for combination therapy.
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.
Department of Internal Medicine, Charles Drew University of Medicine and Science, Los Angeles, CA, USA. shehlapervin@cdrewu.edu
Shehla
S
Pervin
Martin
M
Hewison
Melissa
M
Braga
Lac
L
Tran
Rene
R
Chun
Amer
A
Karam
Gautam
G
Chaudhuri
Keith
K
Norris
Rajan
R
Singh
D000818:Animals; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000494:pharmacology / Q000627:therapeutic use; D001943:Breast Neoplasms / Q000188:drug therapy* / Q000201:enzymology / Q000235:genetics / Q000473:pathology; D045744:Cell Line, Tumor; D002469:Cell Separation; D015536:Down-Regulation / Q000187:drug effects / Q000235:genetics*; D019008:Drug Resistance, Neoplasm / Q000187:drug effects* / Q000235:genetics; D058750:Epithelial-Mesenchymal Transition / Q000187:drug effects / Q000235:genetics; D005260:Female; D020869:Gene Expression Profiling; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D006801:Humans; D018960:Hyaluronan Receptors / Q000378:metabolism; D036341:Intercellular Signaling Peptides and Proteins / Q000494:pharmacology; D042361:Mammary Glands, Human / Q000187:drug effects / Q000473:pathology*; D051379:Mice; D008819:Mice, Nude; D014411:Neoplastic Stem Cells / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D009569:Nitric Oxide / Q000494:pharmacology; D018167:Receptors, Calcitriol / Q000235:genetics*; D047488:Retinoid X Receptors / Q000378:metabolism; D000071250:Snail Family Transcription Factors; D018874:Spheroids, Cellular / Q000187:drug effects / Q000378:metabolism / Q000473:pathology*; D014157:Transcription Factors / Q000378:metabolism; D015854:Up-Regulation / Q000187:drug effects / Q000235:genetics; D014807:Vitamin D / Q000031:analogs & derivatives* / Q000494:pharmacology / Q000627:therapeutic use; D023041:Xenograft Model Antitumor Assays
D018960:Hyaluronan Receptors; D036341:Intercellular Signaling Peptides and Proteins; D018167:Receptors, Calcitriol; D047488:Retinoid X Receptors; D000071250:Snail Family Transcription Factors; D014157:Transcription Factors; C579457:VDR protein, human; D014807:Vitamin D; D009569:Nitric Oxide; C097949:1,25-dihydroxyvitamin D