Cancer-related mortality is caused in a large part by the metastasis of primary tumor. Each cancer has a particular way of spreading cancerous cells. Recently, genetic and pharmacological analysis identified the set of genes, such as epidermal growth factor receptor ligand epiregulin (EREG), cyclooxygenase-2 (COX2) and matrix metalloproteinases 1 and 2 (MMP-1 and MMP-2) that have been found to be associated with metastasis of breast cancer to lung. Inhibition of EGFR and COX2 could minimize lung metastasis of breast cancer in a clinical setting. In this review, we summarized the current knowledge on EREG, COX2, MMP-1 and MMP-2 in tumor development and metastasis.