Background and objectives: High-dose chemotherapy with peripheral blood stem cell transplantation (PBSCT) has become an important treatment for hematological and solid tumors. Several reports on endogeneous production of thrombopoietin (TPO) in patients undergoing intensive chemotherapy have been published. We measured TPO levels in patients undergoing autologous PBSCT in order to elucidate the role of TPO in megakaryopoiesis and platelet recovery following stem cell transplantation. We also examined whether PBSC from different patient groups (patients with lung cancer and malignant lymphoma) had different effects on TPO levels.
Materials and methods: Serum levels of TPO and other cytokines were determined by ELISA before and after PBSCT in 10 patients with lung cancer and 18 patients with malignant lymphoma.
Results: Compared to platelet counts at 1 week after transplantation, those at 3 weeks were significantly increased (p<0.001). In contrast, serum TPO levels were significantly decreased 3 weeks after PBSCT (p<0.01). There were no significant differences in levels of other cytokines between 1 and 3 weeks after transplantation. A strong correlation was found between serum TPO levels and circulating platelet counts (r = -0. 675; p<0.0001). Platelet counts exhibited a significant recovery and TPO levels also decreased significantly in malignant lymphoma patients after transplantation. There were no significant differences in TPO levels in lung cancer patients, although the same tendencies as for malignant lymphoma patients were observed for both platelet count and TPO level. On analysis of transfused PBSC, we found that the numbers of CFU-GM were similar in lung cancer and malignant lymphoma patients. However, the numbers of CD34+ cells were significantly higher in lung cancer patients than in malignant lymphoma patients.
Conclusion: Our findings suggest that TPO plays a critical role in the reconstitution of megakaryopoiesis and platelet production following PBSCT, and that the type of stem cell, tumor, and preceding chemotherapy affect serum TPO levels after transplantation.