Fig 2: Visfatin mediates its effects both directly via cAbl/STAT3 and indirectly mediated by ADSCs via GDF15/AKT on promoting malignant behavior in breast cancer. Previously, we discovered visfatin mainly produced by adipocytes promoted breast cancer cells directly through activation of c-Abl and STAT3, which was blocked by Imatinib and Stattic inhibitor, respectively (black arrow). In this study, we showed that visfatin can act via an indirect pathway by priming ADSCs, which may be recruited from the adipose tissue to tumor site or generated from autologous fat transfer, to produce GDF15 that stimulated AKT activation in breast cancer cells to promote malignant behaviors (white arrow). The effect can be blocked by the treatment of GDF15 neutralizing Ab or Wortmannin inhibitor.

Fig 3: GDF15 play a crucial role in the regulations of breast cancer cells activities by visfatin-treated ADSCs (vADSCs). (A) After the three-day co-culture of MDA-MB-231 cells and vADSCs (V50 and V100 group) or untreated ADSCs (Ctrl group), the CM was collected and analyzed by using a cytokine array kit. (B) The expression of GDF15 in the co-cultured CM was validated by ELISA represented in a histogram. The ADSCs and MDA-MB-231 cells collected from the co-culture system were extracted for cell lysate to analyze the GDF15 expression by western blotting. (C) The migration and invasion of MDA-MB-231 treated with GDF15 at various concentrations for 48 h were evaluated by using a transwell system. (D) The indirect co-culture was performed in the presence or absence of the GDF15 neutralizing antibody of for three days. After that, the migration and invasion of the MDA-MB-231 cells collected from the co-culture were evaluated in a transwell system. (E) The expression of phosphor-AKT (pAKT) of MDA-MB-231 treated with GDF15 (50 ng/mL) at different time point was detected by western blotting. (F) The pAKT was detected in the MDA-MB-231 cells from the co-culture by western blotting. (G) After the three-day co-culture in the presence or absence of the wortmannin (400 nM), the MDA-MB-231 cells were collected from the co-culture for performing the migration assay. All experiments were performed in triplicate.

Fig 4: Visfatin-primed ADSCs promoted the tube formation of HUVEC. (A) HUVEC cells were co-cultured with visfatin-treated ADSCs or untreated ADSCs, noted as V50 and V100 or Ctrl, respectively, for three days. The HUVEC cells were collected from the co-culture and seeded in a matrix gel-coated 96-well plate. The tube formation of HUVEC was observed using a microscope. The length of branches was determined by using the ImageJ software. (B) After the three-day co-culture in the presence or absence of GDF15 neutralizing antibody (GDF15 Nab, 5 µg/mL), the HUVEC cells were collected from the co-culture for performing the tube formation assay. The experiments were performed in triplicate.

Fig 5: Visfatin-pretreated ADSCs (vADSCs) enhanced the tumor growth and metastasis in human breast cancer xenograft mouse model. (A) The nude mice were injected with mixture of MDA-MB-231 and untreated ADSCs (uADSCs) or vADSCs, noted as Ctrl or V50, respectively, to the mammary fat pads. The tumor volumes were measured every week after injection (Ctrl, n = 5; V50, n = 6). (B) After sacrificing the mice, the weight of the resected tumor was measured. (C) The expressions of GDF15, ß-catenin, CD31, and pAKT in the tumor sections were detected by immunohistochemistry. The IHC score was calculated by multiplying the percentage of positive cells by the intensity and present as histogram. (D) The luciferase-expressing MDA-MB-231 were collected and injected into the tail vein of NOD/SCID mice after co-culturing with uADSCs or vADSCs, noted as Ctrl or V50, respectively (Ctrl, n = 8; V50, n = 8). The IVIS radiance signals of the mice were assessed at week 4. The representative images of high and low signal were shown. The statistical differences were calculated by t-test, *, p-value < 0.05; **, p-value < 0.01.