Monoclonal antibody 14C5 targets integrin αvβ3

This study identifies and characterizes the antigen recognized by monoclonal antibody (mAb) 14C5. We compared the expression of antigen 14C5 with the expression of eight integrin subunits (alpha(1), alpha(2), alpha(3), alpha(v), beta(1), beta(2), beta(3), and beta(4)) and three integrin heterodimers (alpha(v)beta(3), alpha(v)beta(5), and alpha(5)beta(1)) by flow cytometry. Antigen 14C5 showed a similar expression to alpha(v)beta(5) in eight different epithelial cancer cell lines (A549, A2058, C32, Capan-2, Colo 16, HT-1080, HT-29, and SKBR-3). Specific binding of P1F6, an anti-alpha(v)beta(6) specific antibody, was blocked by mAb 14C5. After transient expression of alpha(v)beta(5) in 14C5-negative Colo16 cells, mAb 14C5 was able to bind a subpopulation of alpha(v)beta(5)-positive calls. We evaluated the tissue distribution of the 14C5 antigen in colon (n = 20) and lung (n = 16) cancer tissues, The colon carcinoma cells stained positive for 14C5 in 50% of tumors analyzed, whereas bronchoalveolar lung carcinoma and typical carcinoid were not positive for the antigen. More common types of non-small cell lung cancer, i.e., squamous (n = 5) and adenocarcinoma (n = 3), stained positive in 2 of 5 squamous carcinomas and in 1 of 3 investigated adenocarcinoma. Colon (95%) and lung (50%) carcinoma tissues showed extensive expression of antigen 14C5 in the stroma surrounding the tumor cells and on the membrane of the adjacent fibroblasts. We show for the first time that mAb 14C5 binds the vascular integrin alpha(v)beta(5), suggesting that mAb 14C5 can be used as a screening agent to select colon and lung cancer patients that are eligible for anti-alpha(v)beta(5)-based therapies. [Mol Cancer Ther 2008;7(12):3771-9]