CC10 is infrequently expressed in non-small cell lung cancer cell lines, despite being abundantly produced by progenitor cells for normal and neoplastic airway epithelium. We overexpressed CC10 cDNA in the non-small cell lung cancer cell line A549 to determine its effect on the neoplastic phenotype. A549 cells transfected with CC10 demonstrated a marked reduction in invasiveness that was paralleled by diminished 92-kDa and absent 72-kDa metalloproteinase activity by zymography. Western analysis revealed the near absence of the corresponding matrix metalloproteinases (MMPs) MMP-2 and MMP-9 in the CC10-transfected cell lines, but not in the vector-transfected cell lines. The CC10-transfected cell lines also demonstrated decreased adhesiveness to fibronectin compared with the controls. CC10 expression was associated with decreased anchorage-independent growth but not with decreased anchorage-dependent growth. These data suggest that loss of CC10 may contribute to carcinogenesis, because CC10 antagonizes the neoplastic phenotype.