A Monoclonal Antibody Produced Against a Rat Esophageal Carcinoma Cell Line Reacts with an Integrin-Like Molecule Expressed by Rat Epithelial Cells

Abstract

A monoclonal antibody, designated MAb-5A (IgG₁), was generated against a tumorigenic rat esophageal epithelial cell line, B-2T. MAb-5A reacted with a series of non-tumorigenic and tumorigenic epithelial cell lines derived from F-344 rat esophagi or tracheas. However, the highest level of antigen expression was detected on tumorigenic rat epithelial cell lines. A trace amount of antigen was detected in primary cultures of normal rat epithelial cells derived from either esophagi or tracheas. MAb-5A did not react with rat fibroblasts. MAb-5A reacted with B-2T derived tumor tissues propagated in vivo but showed only slight reactivity with normal rat esophageal epithelial tissues.

Cell surface radioiodination, extraction and immunoprecipitation experiments were conducted to characterize the antigen molecule. Analysis of the immunoprecipitates by SDS-PAGE and autoradiography revealed two protein bands with mobilities corresponding to ∼ 140 and 120 kDa, respectively. Under reducing conditions the 140 kDa band shifted to ∼ 120 kDa whereas the 120 kDa band shifted upward to∼ 130 kDa. The non-reduced/reduced mobilities of these bands suggest that they may be members of the integrin family of matrix receptors. A polyclonal antibody to the β₁ subunit immunoprecipitated two similar bands detected by MAb-5A, further suggesting that the antigen complex may be related to members of the integrin superfamily.