Downregulation of myc Promoter-Binding Protein 1 (MBP-1) in Growth-Arrested Malignant B cells

Normal human B lymphocytes are sensitive to the growth-inhibitory action of TGF-beta1 whereas malignant B lymphoma cells are mostly resistant to TGF-beta1 effects. We have shown in our previous work that, TGF-beta1 treatment resulted in significant growth inhibition of the DoHH2 cell line. In the present study we showed that TGF-beta1-induced growth arrest was associated with notable downregulation of the myc-binding protein-1 (MBP-1). Moreover, our results indicated that c-Myc overexpression in TGF-beta1-arrested malignant B cells is mediated by binding of MBP-1, as a transcription repressor, to the (+118/+153) element of the promoter region of the myc gene.