Fig. 5: Identification of Gremlin1 as a pro-myeloma SASP factor that is expressed by MGUS and MM MSCs.

A In silico analysis of gene expression in BM MSCs from MM patients (n = 4) and age-matched healthy controls (n = 3) in publicly available microarray dataset GSE36474. Heat map shows the average z-score for significantly up- or down-regulated genes. B Expression of GREM1, normalised to ACTB, was analysed in passage 5 MSCs from young non-cancer controls (n = 11), aged non-cancer controls (n = 8) and newly diagnosed MGUS (n = 11) and MM (n = 12) patients. Box and whisker plots depict median and interquartile ranges. C Human MSCs from young non-cancer controls (n = 6) were irradiated (60 Gy) to induce senescence and GREM1 expression, normalised to ACTB, was assessed. Data are normalised to non-irradiated cells. D Replicative senescence was induced in human MSCs from young non-cancer controls (n = 11) by sequential passage (passage 13–15) and GREM1 expression, normalised to ACTB, was analysed. Data are normalised to low passage (passage 3) cells. Luciferase-expressing KMM1 (E), RPMI-8226 (F) and 5TGM1 (G) cells were cocultured with OP9 cells overexpressing Gremlin1 (OP9-Grem1), and empty vector control cells (OP9-EV) and, after three days, the relative number of MM cells was quantitated using BLI (n = 3 independent experiments). Graphs depict mean ± SEM. p values are shown for Kruskal-Wallis test with Dunn’s post-test (B) or Wilcoxon matched-pairs signed rank test (C, D) or paired t tests (E–G).