Effects of Overexpressed P2X7 on Leukemia Progression in Mouse Acute Myeloid Leukemia Model

P2X7 is one of the P2X family ligand-gated ion channel receptors. High level expression of P2X7 is reported in various malignant cells. High level expression of P2X7 was also detected in leukemia patients, especially in relapsed cases. A hyposensitive P2X7 mutant, N187D P2X7, was cloned from leukemia cells. However, the role of P2X7 on the progression of leukemia was poorly understood. In the present study, we studied the effects of P2X7 receptor in acute myeloid leukemia mouse model.

We established MLL-AF9 induced AML mouse model with high level expression of P2X7 (MA9-P2X7). High level of P2X7 significantly accelerated the progression of leukemia. Homing capability experiment demonstrated that MA9-P2X7 cells had lower homing potential. The apoptotic rate of freshly isolated leukemia cells had no significant difference between two groups. However, both in vitro culture experiments and in vivo BrdU incorporation assay demonstrated that MA9-P2X7 cells had enhanced proliferation potential, i.e. more S and G2/M phase cells but less G0/G1 phase cells. Moreover, upon treatment with Ara-C, though MA9-P2X7 cells were more sensitive to Ara-C, but the mice had shorter survival time. Furthermore, in vitro colony assay and limiting dilution transplantation experiments showed that MA9-P2X7 cells formed more colonies and had a 7.25-folds increase in LICs frequency. We also detected the expression of c-Kit, and the results showed that the majority of MA9-P2X7 cells were c-Kit⁺, whereas control cells have two populations and more than half of them were c-Kit^-. Leukemia mice in MA9-P2X7 group had shorter survival time than those in the c-Kit⁺ control group.

Our results suggested that leukemia cells overexpressing P2X7 possessed the characteristics of both greater proliferation potential and higher LICs frequency, which contributed to the accelerated progression of leukemia.

This work was supported by grants 81570153, 81770183 and 81170511 from the National Natural Science Foundation of China (NSFC); programs 2016-I2M-2-006 and 2017-I2M-1-015 from the CAMS Innovation Fund for Medical Sciences (CIFMS); grant 17JCZDJC35000 from the Tianjin Natural Science Foundation; and Graduate Student Innovation Fund (2014-0710-1021) from Peking Union Medical College. Z.GG. is a recipient of the New Century Excellent Talents in University (NCET-08-0329).