4-OHT induced IGFBP-1 transcription and extracellular accumulation in MCF-7 cells. (A) Relative IGFBP-1 gene transcription determined by quantitative real-time PCR after 24 hours of treatment with vehicle (V), 100 nM 4-OHT, or 1μM 4-OHT. Relative transcription was normalized to the RPL30 transcript. (B) Immunoblot analysis of concentrated MCF-7 cell culture medium after 24 hours of treatment with vehicle (V), 100 nM 4-OHT, or 1μM 4-OHT. Results are representative of at least three independent experiments. *, p<0.05 compared to vehicle control, and the error bars are SEM.