TGF-β1 resistance is not associated with alterations in TGF-β type II receptors in immortalized human lung epithelial cells

A frequent cause of TGF-β resistance is decreased expression or mutation of TGF-β receptor Type II (TGFβRII) protein. We previously isolated two isogeneic subclones of the human bronchial epithelial cell line BEAS-2B that are respectively resistant (R.1) or sensitive (S.6) to the growth inhibitory effects of TGF-β1. In this study, we examined TGFβIIR expression, ability to bind TGF-β1, and cDNA sequence in the resistant cell line. Immunofluorescent analyses with antibody to TGFβRII indicated that this protein was expressed at the surface of R.1 cells. Affinity binding studies showed that TGF-β1 bound equally well to the resistant (R.1) and sensitive (S.6) cell lines. PCR cloning and sequencing of TGFβRII cDNA revealed no changes from wild type in the resistant cell line. We conclude that alterations in TGF-β Type II receptor are not responsible for TGF-β resistance in this cell line.