[Effect of inorganic pyrophosphatase PPA1 on proliferation and apoptosis of abnormal naive cells in acute B-lymphocytic leukemia].

Objective: To investigate the role of inorganic pyrophosphatase (PPA1) in the proliferation of abnormal naive lymphocytes in B-cell acute lymphoblastic leukemia (B-ALL) and evaluate its potential as a tumor marker. Methods: Bioinformatics analysis predicted the characteristics of the PPA1 gene. Bone marrow specimens were collected from patients with B-ALL, and abnormal immature B lymphocytes were isolated by CD19 and CD10 immunomagnetic beads, with normal cells as controls. PPA1 expression was detected with quantitative polymerase chain reaction (qPCR) and Western blot. B-ALL cell lines NALM-6 and HAL-01 were cultured in vitro, and recombinant PPA1 protein (rPPA1) or PPA1 monoclonal antibody was added to assess changes in cell proliferation, apoptosis, mitochondrial membrane potential, and cell cycle. The GV492-PPA1 overexpression plasmid was constructed and transfected into cells to assess the effect of PPA1 overexpression. shRNA was designed to construct the GV644-shPPA1 recombinant plasmid, and lentiviral transduction was performed to inhibit PPA1 expression. The impact on tumor cells was observed, and the expression levels of key proteins in the PI3K/AKT pathway and apoptosis-related factors were detected. Results: In abnormal immature B lymphocytes from patients with B-ALL, the transcription and expression levels of PPA1 were 3.75 - 14.89 times and 1.25 - 3.79 times those of normal cells, respectively. rPPA1 promoted NALM-6 and HAL-01 cell proliferation, with increased proliferation rates of 29.97% and 20.96% after treatment with 10 μg/ml for 72 h and 48.40% and 58.08% at 20 μg/ml, respectively. PPA1 monoclonal antibody (1:2 000, 1:1 000, 1:500) significantly inhibited proliferation at 19.53%, 46.90%, and 49.42% for NALM-6 cells and 22.29%, 52.41%, and 58.35% for HAL-01 cells, respectively. PPA1 monoclonal antibody (1:2 000, 1:1 000) induced apoptosis, increasing the apoptosis rate of NALM-6 cells from 10.01% to 20.17% and 29.11%, and that of HAL-01 cells from 12.65% to 18.53% and 31.80%. After treatment with the same PPA1 monoclonal antibody dilutions, the proportion of JC-1 monomers significantly increased, reaching 4.08- and 6.49-fold of the control in NALM-6 cells, and 3.99- and 6.42-fold in HAL-01 cells, indicating a decrease in mitochondrial membrane potential, whereas the cell cycle was arrested at the G(0)/G(1) phase. Overexpression of PPA1 for 48 and 72 h increased the proliferation rate of NALM-6 cells by 25.05% and 26.14%, and that of HAL-01 cells by 26.14% and 29.25%, respectively. PPA1 expression inhibition suppressed proliferation, with inhibition rates of 19.77% (48 h) and 28.99% (72 h) for NALM-6 cells, and 20.90% (72 h) for HAL-01 cells. qPCR and Western blot results revealed that PPA1 inhibition reduced the phosphorylation level of the PI3K/AKT pathway and regulated the expression of MDM2, P53, and apoptosis-related factors. Conclusion: PPA1 is closely associated with the proliferation and development of abnormal immature lymphocytes in B-ALL. PPA1 expression inhibition suppresses abnormal cell proliferation and promotes apoptosis, indicating that PPA1 has potential as a new target for tumor prevention and treatment.