EFFECTS OF TRANSFORMING GROWTH-FACTOR-BETA ON PARATHYROID HORMONE-RELATED PROTEIN-PRODUCTION AND RIBONUCLEIC-ACID EXPRESSION BY A SQUAMOUS CARCINOMA CELL-LINE IN-VITRO

The effects of human recombinant transforming growth factor (TGF)-beta (1), were determined on PTH-related protein (PTHrP) production and mes senger RNA (mRNA) expression by a canine squamous carcinoma cell line (SCC 2/88) in vitro. TGF-beta increased PTHrP production in a dose- an d time-dependent manner (P < 0.05) as measured by RIA, and the effects of TGF-beta treatment persisted up to 72 h after removal. TGF-beta in creased PTHrP production by SCC 2/88 cells until cellular confluence, at which time there was no longer a significant increase compared to c ontrol. Actinomycin D inhibited the TGF-beta-mediated increase in PTHr P production, suggesting that TGF-beta acted in part by increasing gen e transcription. SCC 2/88 cells also produced active TGF-beta as measu red by a [H-3]thymidine incorporation assay in mink lung epithelial ce lls. Exposure of SCC 2/88 cells to a neutralizing anti-TGF-beta monocl onal antibody decreased (up to 50%, P < 0.01) basal PTHrP production. TGF-beta increased PTHrP mRNA expression in a dose- and time-dependent manner as evaluated by northern blot analysis. Postconfluent SCC 2/88 cells expressed little mRNA for PTHrP, and there was only a minimal i ncrease in PTHrP mRNA expression in postconfluent TGF-beta-treated cel ls. These results indicate that TGF-beta increased PTHrP production an d mRNA expression in malignant keratinocytes and suggest that TGF-beta may be an important factor in the pathogenesis of humoral hypercalcem ia of malignancy.