EXPRESSION OF ALPHA-THYMOSINS IN HUMAN TISSUES IN NORMAL AND ABNORMALGROWTH

Radioimmunoassays specific for the N and C termini of human prothymosi n alpha and the N terminus of human parathymosin alpha were employed f or the measurement of the levels of alpha-thymosins in human thymus, s pleen, and liver during normal growth and intestine and breast in mali gnant growth. A differential expression of the two alpha-thymosins was observed in thymus (prothymosin alpha-rich) and liver (parathymosin a lpha-rich). A decline in the levels of both alpha-thymosins was found with age, with prothymosin alpha in thymus showing the sharpest change (15- to 30-fold). The levels of both alpha-thymosins were higher in m alignant tissues as compared with healthy ones. In breast cancer, in p articular, the mean increase for prothymosin alpha and parathymosin al pha was 17.9- and 11.5-fold, respectively. The major crossreactive mat erial was characterized in all cases as intact prothymosin alpha and p arathymosin alpha. These results suggest an in vivo relationship of th e expression of alpha-thymosins with the human tissue cell proliferati on activity.