THROMBOPOIETIN IN PATIENTS WITH HEPATOBLASTOMA

Marked thrombocytosis (over 50 x 10(4)/mu l) is frequently seen in pat ients with hepatoblastoma, Thrombopoietin (TPO), c-mpl ligand, has rec ently been purified as the major physiological regulator of the thromb opoiesis and is mainly produced in the liver, Since it is possible tha t TPO participates in thrombocytosis and the tumor growth of this part icular hepatic tumor, serum TPO levels in addition to interleukin 1 be ta (IL-1 beta) and IL-6 levels were assessed in seven untreated patien ts by using a sandwich enzyme-linked immunosorbent assay. High serum T PO levels were observed in all of the examined patients. The level ran ged from 3.15 to 11.02 (mean +/- standard deviation; 6.08 +/- 1.25) fm ol/ml, IL-6 levels were also somewhat higher than normal, Platelet cou nts, however, appeared to correlate more with serum TPO levels (p = 0. 1) than with IL-1 beta (p = 0.5) and IL-6 (p = 0.2) levels, Furthermor e, using the reverse transcriptase polymerase chain reaction method, t he expression of c-mpl mRNA was found in five of eight hepatoblastoma tissues as well as TPO mRNA in all eight tissues. These observations s uggest that thrombocytosis in hepatoblastoma patients results from the production of cytokine members, including TPO, within tumor tissues, Additionally, it is possible that TPO might act as a type of autocrine and/or paracrine system for cellular growth in this tumor.