Figure 7

Intimate interaction between invasive breast cancer cells and mesenchymal stem cells is mediated by the hyaluronan system via layilin. To investigate the role of the hyaluronan system in the interaction between cancer cells and bmMSCs either the HA synthesis of the bmMSCs was inhibited with 4-MU (100 µM) or by silencing the expression of the HA interacting receptors in the cancer cell lines MDA-MB-231 and U87-MG via siRNA. (a) Representative cytochemical stainings of a direct co-culture of bmMSCs and CFSE-labelled MDA-MB-231 and U87-MG cells (green). BmMSCs were previously treated with 4-MU (100 µM) over a period of 72 h. Cells were stained 48 h after the co-cultures were established. Scale bar = 50 µm. (b) Percentage of MDA-MB-231 and U87-MG cells co-localising with bmMSCs after bmMSCs were treated with 4-MU (100 µM). (c) The accumulated distance and (d) the time spent in juxtaposition of bmMSCs as quantified by time-lapse microscopy. (e) Representative cytochemical stainings of a direct co-culture of bmMSCs and HA receptor-depleted cancer cells. The expression of the HA interacting receptors in MDA-MB-231 and U87-MG cells was silenced via siRNAs directed against CD44, RHAMM and LAYN. Afterwards, the cancer cells were stained with CFSE (green). Scale bar = 200 µm, inset = 50 µm. (f) Analysis of the percentage of MDA-MB-231 and U87-MG cells co-localising with bmMSCs. Time-lapse quantification of (g) accumulated distance and (h) time spent in juxtaposition of HA receptor depleted cancer cells. n = 4. Mean ± SEM. *p < 0.05 compared to the respective control treated cells. This figure was prepared with GraphPad Prism (v9.2.0.332, www.graphpad.com).