DEVELOPMENT OF ELISA TO ESTIMATE THYMOSIN ALPHA(1), THE N-TERMINUS OFPROTHYMOSIN-ALPHA, IN HUMAN TUMORS

We reported that tumor content of prothymosin alpha (ProT alpha) is a proliferation index of human breast tumors that might be used to ident ify patients at high risk for distant metastasis (Dominguez et al., Eu r J Cancer 1993; 29A:893-7). In that study ProT alpha concentrations w ere measured by a RIA; here we present an alternative nonisotopic assa y that could be used in a standard clinical laboratory. Main features of the ELISA are: (a) A recombinant fusion protein glutathione S-trans ferase (GST)-human ProT alpha was used to coat the microtiter plates; (b) we used a polyclonal antiserum raised in rabbits that detects thym osin alpha(1), the NH2-terminal fragment of ProT alpha; (c) it is as s ensitive as the RIA; (d) it is faster than the RIA. ProT alpha concent rations in various human tumors (skin, esophagus, colorectal, and brea st) as assessed by ELISA were comparable with, although twofold greate r than, the values previously estimated by RIA.