GROWTH SUPPRESSION BY TRANSFORMING GROWTH-FACTOR BETA(1) OF HUMAN SMALL-CELL LUNG-CANCER CELL-LINES IS ASSOCIATED WITH EXPRESSION OF THE TYPE-II RECEPTOR

Nine human small-cell lung cancer cell lines were treated with transfo rming growth factor beta(1) (TGF-beta(1)). Seven of the cell lines exp ressed receptors for transforming growth factor beta (TGF-beta-r) in d ifferent combinations between the three human subtypes I, II and III, and two were receptor negative. Growth suppression was induced by TGF- beta(1) exclusively in the five cell lines expressing the type II rece ptor. For the first time growth suppression by TGF-beta(1) of a cell l ine expressing the type II receptor without coexpression of the type I receptor is reported. No effect on growth was observed in two cell li nes expressing only type III receptor and in TGF-beta-r negative cell lines. In two cell lines expressing all three receptor types, growth s uppression was accompanied by morphological changes. To evaluate the p ossible involvement of the retinoblastoma protein (pRb) in mediating t he growth-suppressive effect of TGF-beta(1), the expression of functio nal pRb, as characterised by nuclear localisation, was examined by imm unocytochemistry. Nuclear association of pRb was only seen in two of t he five TGF-beta(1)-responsive cell lines. These results indicate that in SCLC pRb is not required for mediation of TGF-beta(1)-induced grow th suppression.