CD45-CD34+ Endothelial Progenitor Cells (EPCs) from Human Adipose Tissue Promote Tumor Growth and Metastases

Abstract 2208

A catalytic role has been proposed in neoplastic angiogenesis and cancer progression for bone marrow-derived endothelial progenitor cells (EPCs). However, in preclinical and clinical studies the quantitative role of marrow-derived EPCs in cancer vascularization was found to be extremely variable. Adipose tissue represents an attractive source of autologous adult stem cells due to its abundance and surgical accessibility.

Lipotransfer aspirates (LAs) from patients undergoing breast reconstruction after breast cancer surgery were analyzed by six colors flow cytometry and tissue culture. After collagenase digestion, cells were stained with the nuclear binding antigen Syto16 and 7-AAD and with CD34, CD45, CD133, CD31, CD140b, CD105, CD90, CD44, CD13, CD144, CD10, CD29, CD109, CD117, CD146,CD16, CD11c, CD14, CD38, CXCR4, VEGFR-1, VEGFR-2, VEGFR-3, Tie-2. The absolute count of CD45-CD34+ cells was obtained using reference beads in Trucount tubes (BD, Mountain View, CA). LAs were found to contain a large amount of CD45-CD34+ cells fulfilling the most recent criteria for EPC identification. These CD45-CD34+ cells included two subpopulations: CD45-CD34++ CD13+ CD140b+ CD44+ CD90++ cells and CD45-CD34+ CD31+CD105+ cells. We found in the adipose tissue about 263 fold more CD45-CD34+ EPCs/mL when compared to the bone marrow. In particular, the median of CD45-CD34+CD31- cells/mL was 181,046 (range 35,970–465,357), and the median of CD45-CD34+CD31+ cells/mL was 76,946 (range13,982-191,287).

When compared to marrow-derived CD34+ cells, purified CD45-CD34+ adipose cells expressed similar levels of stemness-related genes such as NANOG, SOX2, Lin28 and significantly increased levels of angiogenesis-related genes such as CD144, VEGFR2, ALK-1. In vitro, CD45-CD34+ cells generated mature endothelial cells and capillary tubes as well as mature mesenchymal cells.

When coinjected with triple negative human breast cancer MDA-MB-436 and HCC1937 cells in the mammary fat of a murine model of human breast cancer, purified CD45-CD34+ cells significantly increased tumor growth, and immunohistochemistry studies demonstrated the presence of human CD31+, CD34+, CD105+ endothelial cells lining the vessels of orthotopic breast cancers growing in mice co-injected with human adipose tissue-derived CD45-CD34+ cells. Moreover, in a mouse model of breast cancer metastatization we found an increased number of lung and axillary lymph node metastases when purified CD34+ WAT cells were injected into the third mammary fat pad after the primary tumor resection.

In conclusion our data demonstrate that the phenotype of adipose derived EPCs is consistent with that reported for both bone marrow and circulating EPCs, but their frequency in adipose tissue is more than 250 fold higher. Further studies are ongoing to clarify what cell populations residing in the adipose tissue can be used safely for breast reconstruction and what are at risk for supporting the growth of otherwise quiescent cancer cells still resident after surgery.