Figure 1. Expression of CXCL16 by prostate cancer recruits MSCs into tumors to support tumor growth.
(a) CXCR6 mRNA expression by human MSCs (P1 and P2). (b) Expression of CXCR6 protein by human MSCs. Controls included isotype matched controls and fibroblast-specific protein 1 (FSP1) for MSCs. Scale bars, 100μm. (c) CXCR6 mRNA by mMSCs. CXCR6 expression was determined in freshly isolated, non-cultured (P0) or P2 murine MSCs from CXCR6+/+ or CXCR6−/− mice. Human and murine osteoblasts (HOB and MC3T3-E1) were used as a negative control. (d) Expression of CXCR6 by murine P2 CXCR6+/+ or CXCR6−/− MSCs by IHC staining. Scale bar 100μm. Data in (a-c) are representative of mean with standard deviation for triplicates in each of three independent experiments (Student’s t-test). (e) CXCL16 expression in human prostate cancer tissue microarray in Supplementary Fig. S1b. Differences noted between normal prostate (n = 30), Gleason 4+5 (n = 9), Gleason 6+7 (n = 18), and Gleason 8+9 (n = 15) (mean±s.d. Student’s t-test). Secretionof CXCL16 by human prostate cancer cell lines (f) and murine prostate cancer cell lines (g) as determined by ELISA (mean±s.d., n = 3 independent experiments, Student’s t-test). (h) Migration of freshly isolated, non-cultured (P0) or P2 murine MSCs from CXCR6+/+ or CXCR6−/− mice in response to CXCL16. The % migrated MSC was determined by hemocytometer counting (mean±s.d., n = 3 independent experiments, Student’s t-test). (i) CXCR6+/+ or CXCR6−/− mice were implanted s.c. with RM1 cells and caliper measurements of tumor growth performed over 25 days. *Significant differences between tumors grown CXCR6+/+ and CXCR6−/− mice (mean±s.d, for 7 animals/group, n = 3 independent experiments, P < 0.05; Student’s t-test). (j) % MSCs (P0) present in RM1 tumors grown in CXCR6+/+ or CXCR6−/− mice at day 25 (mean±s.d. for 7 animals/group, n = 3 independent experiments, Student’s t-test). (k) SCID mice were implanted s.c. with PC3 cells mixed with MSCP0CXCR6+/+ or MSCP0CXCR6−/− cells and tumor growth was evaluated by caliper measurements over 42 days. *Significant differences between tumors grown with PC3 cells mixed with MSCP0CXCR6+/+ and MSCP0CXCR6−/− cells (mean±s.d. for n = 5 animals/group, n = 1 independent experiment, P < 0.05, Student’s t-test).