In a phage display study, Brown and Ruoslahti (10) identified that a lung homing domain (amino acids 378–440 in mice and 381–443 in humans) in AEG-1/MTDH was a mediator of 4T1 mouse mammary tumor cell adhesion to the lung vasculature, and suggested that AEG-1/MTDH is important in breast cancer metastasis. The gene discussed is MTDH; the disease is breast carcinoma.