Apoptosis-inducing Effects And Mechanism Of N-phosphoryl Peptide Methyl Esters On K562 Cells

Phosphorus plays a crucial role in life science. Many phosphoryl proteinsand phosphoryl peptides have important biological activities. In the presentdissertation, the synthesis and activities of inhibiting K562 cells' (humanchronic myelogenous leukemia (CML) cell line) proliferation of a series ofN-phosphoryl peptide methyl esters have been investigated, and theapoptosis-inducing mechanism of (DIPP-L-Leu)₂-L-Lys-OMe on K562 cellshas been further studied.Study on the structure-activity relationship of the analogues of(DIPP-Leu)₂-LysOMe and (DIPP-Trp)₂-LysOMe showed the configurations ofamino acids and the phosphoryl groups of N-phosphoryl peptide methyl estersaffect the compounds' activities of inhibiting K562 cells' proliferation. TheN-phosphoryl peptide methyl esters synthesized by L-amino acides have thehigher activities than those synthesized by D-amino acids. The configurationof Lysine has the greater influence on the compounds' activities than that ofother amino acids. The result also indicated that (N-diisopropyosyl-L-Leu)₂-L-LysOMe has the higher activity than other substituted alkyloxy(N-phosphoryl-L-Leu)₂-L-LysOMe.(DIPP-L-Leu)₂-L-LysOMe was known to induce apoptosis of K562 cells.Studies on the molecular and cellular mechanism involved in this processshowed that (DIPP-L-Leu)₂-L-LysOMe-induced apoptosis is associated withcytosolic accumulation of cytochrome c (Cyto c), sustained loss ofmitochondrial transmembrane potential (MMP), transient generation ofreactive oxygen species (ROS) and elevation of intracellular Ca²⁺concentration. Immunofluorescence analysis indicates that (DIPP-L-Leu)₂-L-LysOMe induced upregulation of pro-apoptotic Bax and downregulation ofanti-apoptotic Bcl-2 and Bcl-x_L. Together with previous research that(DIPP-L-Leu)₂-L-LysOMe cause the activation of caspase-9 and -3 but notcaspase-8, present findings suggest that (DIPP-L-Leu)₂-L-LysOMe induce theapoptosis through mitochondria-dependent pathway in K562 cells. Theregulation of Bcl-2 family members and mitochondrial dysfunction aredirectly responsible for the pro-apoptotic effects of (DIPP-L-Leu)2-L-Lys-OMe.