TGFB1 and breast carcinoma: As shown in Fig. 5a, overexpression of CystC or Δ14CystC in human MDA-MB-231 breast cancer cells significantly reduced reporter gene expression stimulated by moderate TGF-β concentrations (such as 0.5 ng/ml), an effect that was overcome by stimulation with supraphysiological TGF-β concentrations (such as 5 ng/ml).