Thus, we analyzed the mRNA expression levels of TGF-β isoforms (TGF-β1, TGF-β2 and TGF-β3) and their receptors (TβRI and TβRII) by qRT-PCR in this panel of five human breast cancer cell lines in cultures that had reached the same confluence level (Figure 2). Here, TGFB1 is linked to breast cancer.