Fig. 2.

IL-6-secreting TNBC cells attract IL-6R-expressing/PGE₂-secreting MSCs, in the orthotopic model. a Schematic representation of the assays performed. b The volume of orthotopic mammary tumors developed following injection of 2 × 10⁶ cells of MDA-231/shCtrl cells (light blue, n = 5), MDA-231/shIRIS (dark blue, n = 5), MDA-468/shCtrl (yellow, n = 5), and MDA-468/shIRIS (red, n = 5). The inset shows the expression of IRIS in these cells. c The levels of circulating IL-6 (upper) or PGE₂ (lower) as detected using ELISA in sera from mice bearing MDA-231/shCtrl or MDA-231/shIRIS and MDA-468/shCtrl, or MDA-468/shIRIS tumors. d FACS analysis of the percentage of IL-6R⁻CD90⁻, IL-6R⁻CD90⁺, IL-6R⁺CD90⁻, or IL-6R⁻CD90⁺ cells within MDA-231/shCtrl and MDA-231/shIRIS tumors (upper), or MDA-468/shCtrl and MDA-468/shIRIS tumors (lower). Fluorescence IHC staining of MDA-231/shCtrl or MDA-231/shIRIS tumor sections with CK5 (green), the MSC marker CD90 (red), and IL-6R (yellow). In 3`, 5`, and 9`, arrowheads denote cancer cells and arrows denote MSCs. The asterisk in 8 denotes immune cells (e.g., B cells) or red blood cells non-specific labeling with most likely a subset of secondary antibodies. Scale bars = 100 μm in 1–6 and 7–12 and 50 μm in 3`, 9`, 5`, and 11`