Myeloid leukemic cells express and secrete bioactive pituitary-sized 23 kDa prolactin

Prolactin (PRL) is a 23 kDa polypeptide hormone of pituitary origin which i s of major importance for reproduction. In addition, PRL has immunomodulato ry effects and can be produced in small quantities in nonpituitary tissues. To address possible autocrine or paracrine functions of PRL in leukemia, w e characterized immunoreactive PRL from the culture medium of leukemic cell s. The myeloid cell line Eol-1 expresses the long extrapituitary type mRNA for PRL and synthesizes immunoreactive PRL with a molecular weight of 29 kD a. The biological activity in Eol-1 culture medium was determined using the Nb2 bioassay. This activity co-eluted with recombinant human (rh) PRL on a n S-200 Sephacryl gel filtration column and could be blocked by anti-PRL an tiserum. Western blot analysis and Nb2 bioassays also suggest that acute my elogenous leukemic blasts secrete bioactive 23 kDa PRL in one out of three tested patients. (C) 2000 Elsevier Science B.V. All rights reserved.