CXCL5 secreted from adipose tissue-derived stem cells promotes cancer cell proliferation

Accumulating data suggest that adipose tissue facilitates breast tumor initiation and progression through paracrine and endocrine pathways, and that adipose tissue-derived stem cell (ASC) is likely the major cell type responsible for tumorigenesis and tumor development. However, it remains unknown how ASCs exert their effects. In the present study, in cultured breast cancer cell lines, including estrogen receptor (ER)-positive MCF-7 cells and ER-negative MDA-MB-231 cells, the effects on tumor proliferation of isolated ASCs from human breasts were examined. The expression of 174 cytokines was additionally identified in this medium. With an anti-human C-X-C motif ligand 5 (CXCL5) monoclonal antibody, the effects of neutralization of CXCL5 on the actions of ASCs in a co-culture medium of ASCs and tumor cells were studied The results demonstrated that ASCs significantly increased the number of breast cancer cells compared with controls. Similarly, the co-culture medium of ASCs with breast cancer cells exhibited potent effects on tumor cell proliferation. In the co-culture medium of ASCs with breast cancer cells, CXCL5 levels were significantly increased. In addition, depletion of CXCL5 with its specific antibody in ASC-conditioned medium blocked the stimulatory effect of ASCs on the proliferation of breast cancer cells. To the best of our knowledge, these results indicate for the first time that ASC-secreted CXCL5 is a key factor promoting breast tumor cell proliferation.