To determine in vivo biological significance of Sema4D expression in breast cancer as it relates to skeletal metastasis, we injected MDA-MB-231 cells stably expressing luciferase, controls and those with silenced Sema4D, into the left ventricle of immunosuppressed (nude) mice, which avoids passage through the lung, and tracked the development of skeletal lesions through bioluminescence imaging. This evidence concerns the gene SEMA4D and breast cancer.