Promotion of Primary Murine Breast Cancer Growth and Metastasis by Adipose-Derived Stem Cells Is Reduced in the Presence of Autologous Fat Graft

Background: Cell-assisted lipotransfer involves enrichment of autologous fat with supraphysiologic numbers of adipose-derived stem cells to improve graft take. Adipose-derived stem cells have been shown to promote cancer progression, raising concerns over the safety of adipose-derived stem cells and cell-assisted lipotransfer in postoncologic breast reconstruction. The authors compared the effect of adipose-derived stem cells alone, cell-assisted lipotransfer, and conventional fat grafting on breast cancer growth and metastasis. Methods: Proliferation and migration of murine 4T1 breast cancer cells cultured in control medium or mouse adipose-derived stem cell-or fat graft-conditioned medium were assessed by flow cytometry and scratch assay, respectively. Transcription levels of arginase-1, transforming growth factor-beta, and vascular endothelial growth factor were assessed in adipose-derived stem cells and fat graft by quantitative reverse transcription polymerase chain reaction. An orthotopic mouse tumor model was used to evaluate breast cancer progression and metastasis. 4T1 cells were injected into the mammary pad of female BALB/c mice. Six days later, tumors were injected with saline, adipose-derived stem cells, fat graft, or cell-assisted lipotransfer (n = 7 per group). Two weeks later, primary tumors were examined by immunohistochemistry and lung metastasis was quantified. Results: Adipose-derived stem cell-conditioned medium increased cancer cell proliferation (p = 0.03); migration (p < 0.01); and transcription of arginase-1, transforming growth factor-beta, and vascular endothelial growth factor compared to fat graft-conditioned or control medium (p < 0.02). Tumor-site injection with adipose-derived stem cells alone led to increased primary tumor growth and lung metastasis compared to control, fat graft, or cell-assisted lipotransfer groups (p < 0.05). Adipose-derived stem cell injection increased CD31+ vascular density in tumors (p < 0.01). Conclusion: Adipose-derived stem cells alone, but not conventional fat graft or cell-assisted lipotransfer, promote breast cancer cell proliferation and invasiveness in vitro and in vivo.