[The Study of PI3K-Ⅲ Like Functional Polypeptide on Leukemia Cell K562 during the Process of Programmed Cell Death]

Objective: To study the molecular mechanism of PI3K-Ⅲ like functional domain inducing programmed cell death of leukemia cell line K562.

Methods: The purified PI3K-Ⅲ like functional domain protein was obtained by Pichia pastoris expression system. MTT assay and colony-forming assay were used to detect the effects of PI3K-Ⅲ like functional domain protein on K562 cell proliferation. The effects of PI3K-Ⅲ like functional domain protein on apoptosis and cell cycle of on K562 cells were detected by flow cytometry. The ultrastructural changes were detected by transmission electron microscopy. The expression of caspase-3 was detected by ELISA. The protein expressions of ATG4B, Beclin-1, Bcl-2 and LC3-II were evaluated by Western blot.

Results: PI3K-Ⅲ like functional domain protein could inhibit the proliferation and clony formation of K562 cells, which was significantly higher than the control group (P<0.05). In the experimental group, apoptosis and autophagosome were shown in K562 cells. The proportion of cells in G₀/G₁ phase increased significantly, while in S phase decreased significantly. Cell growth mostly stagnated in G₀/G₁ phase, which was significantly different from the control group (P<0.05). With the increase of concentration, the expression of caspase-3 protein increased significantly compared with the control group (r=0.966, P<0.05). The expression of ATG4B and beclin-1 appeared from increase to decrease, LC3-II increased while Bcl-2 decreased at different time points.

Conclusion: PI3K-Ⅲ like functional polypeptide could induce programmed cell death of leukemia cell K562. Beclin-1/Bcl-2 and caspase pathway may be involved in this way, which suggesting meant autophagy and apoptosis may work together at the same time.