CTBP1 and breast carcinoma: High concentrations (10 mM) of MTOB, an intermediate in the methionine salvage pathway [75], are required to antogonize the CtBP-regulated activities in colon and breast cancer, while NSC95397 has been shown to be a weaker CtBP inhibitor than MTOB and also not being selective for CtBP1 activities [76–79].