Cancer stemness in bone marrow micrometastases of human breast cancer Journal Article

Authors: Kuo, M. C.; Kothari, A. N.; Kuo, P. C.; Mi, Z.
Article Title: Cancer stemness in bone marrow micrometastases of human breast cancer
Abstract: BACKGROUND: Cancer cells metastasize to the bone marrow to create the premetastatic niche. Cancer stemness (expression of stem cell characteristics) is regulated by the tumor microenvironment and associated with self-renewal and poor clinical outcomes. Osteopontin induces mesenchymal stem cells in the tumor microenvironment to adopt a cancer-associated fibroblast phenotype to potentiate cancer growth and metastasis. The mechanisms by which cancer cells and tumor microenvironment regulate stemness in the bone marrow premetastatic niche is unknown. METHODS: Human breast cancer cell lines, MDA-MB-231 and MCF-7 were used in an orthotopic murine xenograft model. NOD-scid mice were implanted with 2 x 10(6) tumor cells in the presence and absence of human mesenchymal stem cells-green fluorescent protein cells and/or osteopontin aptamer, which blocks and inactivates extracellular osteopontin, or mutant aptamer (osteopontin mutant aptamer). In select instances, MCF-7 cells transfected to express osteopontin were coimplanted instead of MCF-7. Stemness markers (Nanog, Oct4, Sox2) in the tumor cells and cancer-associated fibroblast (alpha-smooth muscle actin, Vimentin) markers in the mesenchymal stem cells were measured in femoral bone marrow via real-time polymerase chain reaction. Cell number was determined by titrating cell number to Ct value in vitro. RESULTS: Tumor cells and mesenchymal stem cells migrate from the primary tumor site to the bone marrow. Migration of mesenchymal stem cells is osteopontin dependent. In both MDA-MB-231 and MCF-7 cell lines, levels of both cancer-associated fibroblast and stemness markers were 3 to 4 times greater under conditions wherein mesenchymal stem cells were present with osteopontin. Inactivation of extracellular osteopontin with an aptamer decreased migration of mesenchymal stem cells and expression of both cancer-associated fibroblast and stemness markers. Cancer cells exhibited a significantly increased stem cell profile in the presence of cancer-associated fibroblast in the bone marrow. In the presence and absence of osteopontin, Sox2 knockdown abolished expression of both Nanog and Oct4. CONCLUSION: We conclude that osteopontin-dependent migration of cancer-associated fibroblast is required for increased cancer cell stemness in the bone marrow premetastatic niche.
Journal Title: Surgery
Volume: 163
Issue: 2
ISSN: 1532-7361; 0039-6060
Publisher: Elsevier Inc  
Journal Place: United States
Date Published: 2018
Start Page: 330
End Page: 335
Language: eng
Notes: LR: 20180123; CI: Copyright (c) 2017; JID: 0417347; 2017/02/25 00:00 [received]; 2017/06/13 00:00 [revised]; 2017/07/29 00:00 [accepted]; 2017/10/11 06:00 [pubmed]; 2017/10/11 06:00 [medline]; 2017/10/10 06:00 [entrez]; ppublish