Metastatic Cells Will Take Any Help They Can Get

Two recent papers in Cancer Cell (Lu et al., this issue of Cancer Cell, and Kang et al.) illustrate means whereby acquisition of VCAM-1 by tumor cells can promote metastasis. First, monocyte/macrophages expressing α4 integrin bind VCAM-1 and provide survival signals enhancing establishment of metastases. Second, VCAM-1 allows dormant tumor cells to interact with osteoclasts, yielding paracrine signals and enhancing osteolytic metastatic growth.