Elevated activity and expression of Src-family kinases in human breast carcinoma tissue versus matched non-tumor tissue

Src-family kinase expression was measured in 52 human mammary tumor (T) spe cimens compared with non-tumor (NT) tissue from the same patient by enzymat ic assays employing a Src-kinase family-specific peptide substrate and by i mmunoblotting with an antibody recognizing the Src-family kinases Src, Fyn, and Yes. In the T specimens, the mean enzymatic activity was moderately el evated (T: 160 fmol ATP min(-1) mg(-1); NT: 115 fmol ATP min(-1) mg(-1)) wi th 25 tumor samples having higher activity than the corresponding NT tissue , 17 having lower activity, and no activity detectable in ten T/NT pairs. I mmunoblotting revealed clearly elevated expression in 25 tumor tissues and no differences or expression below the detection limit in the remaining T/N T pairs. The data are in agreement with a possible role of Src-family kinas es for the biology of mammary carcinoma.