Tumor growth inhibition and prevention of metastasis and angiogenesis formation by relaxin-2 inhibition. A, treatment with anti- relaxin-2 mAb at 100 ug weekly i.p for 42 d. inhibited primary tumor growth by 73 ± 6% compared with controls (n = 6; *P <0.01). B, treatment with anti- relaxin-2 mAb at 100 ug weekly i.p for 42 d. promotes apoptosis in primary tumor cells by 8.2 ± 1.2% compared with controls (n = 6; *P <0.01). C, inhibition of tumor angiogenesis by anti- relaxin-2 mAb treatment as measured by MVD. The vascular density of the anti- relaxin-2 mAb–treated tumor was 0.57 ± 0.22%, which was significantly lower than the controls 1.84 ± 0.26%.( n = 6). *, P < 0.01. D, MG-63 cells transfected with Relaxin-2 siRNA (1 × 105 cells/100 uL in PBS) were injected into the tail vein of SCID mice, followed by analysis of settlement of tumor cells to lung after 2 weeks. The number of macroscopic tumor nodules in Relaxin-2 siRNA–treated mice was 9.46 ± 1.8 lung nodules per mouse versus 62.4 ± 7.4 nodules in the controls (n = 5 mice/group). One way ANOVA analysis was performed to compare the number of micro-metastasis in the lung of mice. *, P < 0.05.