Thrombopoietin Receptor Expression in Human Cancer Cell Lines and Primary Tissues

c-mpl is the receptor for the recently identified megakaryocyte growth and differentiation factor thrombopoietin. Thrombopoietin has been shown to be capable of raising platelet counts in animals and is about to enter clinical trials in humans. In anticipation of its likely use in the care of patients receiving cancer chemotherapy, we evaluated the expression of human c-mpl by reverse transcription PCR on 39 human cell lines and 20 primary human tissue samples derived from both normal and malignant sources. c-mpl transcripts were found in all megakaryocytic cell lines tested (CMK, CMK-2B, CMK-2D, SO, and DAMI), the CD34+ leukemia cell line KMT-2, and a hepatocellular carcinoma cell line (Hep3B). Among primary tissues, fetal liver cells and brain had detectable levels of c-mpl message, and among primary tumors, none were found to express c-mpl. These data support the conclusion that c-mpl has restricted expression that is primarily, but not exclusively, related to megakaryocytopoiesis. These observations suggest that thrombopoietin is unlikely to have direct effects on other malignant or normal tissue should it have a clinical role in the treatment of chemotherapy-induced thrombocytopenia.