Fig. 6: Pharmacologic MERTK blockade inhibits tumor progression and cancer-induced bone loss in breast- and lung cancer bone metastasis.

a–n After intracardiac injection of luciferase⁺ H460 and MDA-MB-231 cells, NSG mice were treated with vehicle or 60 mg/kg R992 BID. a Representative images from bioluminescence imaging indicating the amount of tumor load. b, c Luminoscore (whole-body radiance intensity) in the H460 (b) and MDA-MB-231 (c) mouse model (H460 model: Vehicle n = 6 and R992 n = 8; MDA-MB-231 model: Vehicle n = 10 and R992 n = 8). d μCT analysis of bone loss by calculating the change in bone volume (BV/TV) of tumor-bearing mice in relation to healthy age-matched control mice (H460 model: healthy controls n = 5, vehicle n = 14, and R992 n = 10; MDA-MB-231 model: healthy controls n = 8, vehicle n = 20, and R992 n = 16). e 3D reconstructions of microcomputed tomography (μCT) recordings of the metaphyseal proximal region of the tibia of healthy and tumor-bearing mice treated with vehicle or R992. f Representative pictures of TRAP/Hematoxylin staining of bone metastasis of MDA-MB-231 injected mice. Osteoclasts are stained in red, green arrows pointing to osteoblasts, and yellow arrows pointing to intratumoral TRAP-positive mononuclear cells. g Histomorphometric analysis of osteoblast number (H460: vehicle n = 14 and n = 10; MDA-MB-231: vehicle n = 20 and R992 n = 16). h Determination of serum bone formation marker P1NP by ELISA (H460: vehicle n = 7 and R992 n = 5; MDA-MB-231: vehicle n = 9 and R992 n = 8). i Histomorphometric analysis of osteoclast number per bone perimeter (H460: vehicle n = 14 and R992 n = 10; MDA-MB-231: vehicle n = 20 and R992 n = 16). j Determination of serum osteoclast marker TRAP5b by ELISA (H460: vehicle n = 7 and R992 n = 5; MDA-MB-231: vehicle n = 10 and R992 n = 8). k, l Histomorphometric analysis of the number of TRAP⁺ mononuclear cells in the bone marrow in the H460 model (vehicle n = 14 and R992 n = 10) (k) and in the MDA-MB-231 model (vehicle n = 12 and R992 n = 7) (l). m, n Kaplan–Meier curves of overall survival in the H460 (m) and MDA-MB-231 (n) model (H460: vehicle n = 6 and R992 n = 8; p = 0.0463 Mantel–Cox test; Median survival 16 vs. 19 days) (MDA-MB-231: vehicle n = 5 and R992 n = 5; p = 0.0391 Mantel–Cox test; Median survival 55 vs. 60 days). Data were mean ± SEM. Statistical significance was determined by a two-tailed unpaired t-test unless otherwise stated.