SMN1 and central nervous system cancer: In accordance with these findings, quantification of TGF-β1 and TGF-β2 transcriptlevels by real-time PCR revealed that U-373 MG and SMA-560 glioma cells expressboth TGF-β1 and TGF-β2, respectively,while TGF-β1 is clearlythe predominant isoform in F98 and U-87 MG glioma cells (data not shown).