Localization of recognition site between transforming growth factor-beta1 (TGF-beta1) and TGF beta receptor type II: possible implications in breast cancer.

Although overexpression of TGF-beta1 protein has been demonstrated in advanced breast cancer (BC) patients, as well as in other solid tumours, the molecular mechanism of this process remains obscure. This paper proposes that a genetic/epigenetic alteration might occur in the TGF-beta1 gene, within the region coding for the recognition site with TGFbeta receptor type II, leading to a disruption of the ligand-receptor interaction and triggering the TGF-beta1 cascade-related BC progression. To establish the operational framework for this hypothesis, in the present study, this recognition site was identified by the Informational Spectrum Method (ISM) to comprise two TGF-beta1 peptides (positions 47-66 aa and 83-112 aa) and one receptor peptide at positions 112-151 aa of the extracellular domain of the receptor (TbetaRIIM). The TbetaRIIM locus was further evaluated by ISM-derived deletion analysis of the TbetaRII sequences. To provide experimental support for the proposed model, a pilot study of plasma TGF-beta1 analysis was performed in advanced BC patients (n = 8). Two commercial ELISA assays, one with specific alphaTGF-beta1 MAb (MAb) and other with TbetaRIIM as the immobilized phase, revealed pronounced differences in the pattern of plasma TGF-beta1 elevation. In MAb-profile, the TGF-beta1 increase was detected in 7 of 8 patients, whereas analogous TbetaRIIM-profile revealed the elevation in 3 of 8 patients, taking a 50% of maximal elevation as the cut-off value. These findings are consistent with the proposed aberration of TGF-beta1 ligand within the TbetaRII recognition site. Summarizing, this model system is a good starting point for further genetic studies, particularly on genetic/epigenetic alterations of sequences involved in TGF-beta1 and TbetaRIIM interaction, with putative prognostic value for breast cancer.