| Bcl-2family proteins are crucial regulators of apoptosis. The anti-apoptotic Bcl-2-like members (Bcl-2, Bcl-XL, Mcl-1, Bcl-W and Al) oppose two pro-apoptotic groups:the multidomain proteins (Bax, Bak and Bok) and the BH3-only proteins (Bom, Puma, Noxa, Bad, Bid, Bmf, Bik and Hrk).They through Protein-protein to regulate endogenous apoptotic pathway. It has been established that many types of solid tumor and hematologic neoplasms exhibit inherent overexpressed pro-apoptotic Bcl-2-like protein. Mcl-1protein, for example, is critical for sustained survival and expansion in AMLBax and Bak are the crucial apoptosis effectors in the Bcl-2pathway, as they could help to execute mitochondrial dysfunction upon receipt of death signals. It is still a moot question whether Bax and Bak are redundant or nonredundant. Most of the traditional models suggested that Bak and Bax can compensate for each other in apoptosis, however, in some cases they play separated role.Small molecules that neutralize pro-apoptotic Bcl-2-like proteins are promising antitumor agents. The clinical candidates ABT-737and obatoclax have been used in leukemia treatment. However, there has been evidence that AML cells develop resistance to ABT-737because ABT-737does not target Mcl-1. Obatoclax can inhibit both Bcl-2and Mcl-1, but it is not as putative as ABT-737that it induces apoptosis not thoroughly depending on Bax/Bak. The nonspecific activity could limit its therapeutic efficiency and potentially provoke undesirable side effects. We previously identified that the putative BH3mimetic S1exhibits high affinity toward Mcl-1(Ki=58nM), and kills the cancer cells completely through Bax/Bak. S1may play an efficient anti-cancer activity in the ABT-737-resistant AML cells.The aim of the present study is to dissect the details of apoptosis signaling induced by S1in AML cells and to provide a molecular basis for the use of S1in AML treatment. A tumor marker is a substance found in the blood, urine, or body tissues that can be elevated in cancer, among other tissue types. There are many different tumor markers, each indicative of a particular disease process, and they are used in oncology to help detect the presence of cancer. An elevated level of a tumor marker can indicate cancer; however, there can also be other causes of the elevation. Tumor markers can be produced directly by the tumor or by non-tumor cells as a response to the presence of a tumor. Most tumor markers are tumor antigens, but not all tumor antigens can be used as tumor markers.The anti-leukemic activity of S1was evaluated in three cultured AML cell lines and Twenty-seven patient samples. Avvexiin-FITC-PI double staining cells and flow cytometry. caspase detection, immune co-precipitation experiments proved S1induced apoptosis via an intrinsic apoptosis pathway by disruption of protein-protein interactions of Bcl-2family members and triggered the activation of Bax and Bak in AML cells. The anti-leukemic activity of S1is difference in sensitivity in different cells (EC50range between3μM-55μM). Through data analysis,we prove four Bcl-2family of anti-apoptotic protein expression levels are not predictive molecular markers can be used as S1, Bak protein activation linear correlation of anti-leukemic activity EC50values. Furthermore, S1-induced apoptosis was largely reduced in cells with shRNA-mediated down-regulation of Bak but not Bax. Finally, the S1derivatives proved to improve the Mcl-1protein ubiquitination thereby enhancing activation of Bak protein can be efficiently anti-S1resistant AML cells. Our study identifies Bak protein is the molecular markers in S1induced apoptosis in AML. Most of leukemia exhibit inherent overexpressed Bcl-2-like proteins. Small molecule S1is a BH3mimetic discovered by our previous studies. The aim of this study is to dissect the details of apoptosis signaling induced by S1in AML cells and to provide a molecular basis for the use of S1in AML treatment. The anti-leukemic activity of S1was evaluated in three cultured AML cell lines and Twenty-seven patient samples. S1induced apoptosis via an intrinsic apoptosis pathway by disruption of protein-protein interactions of Bcl-2family members and triggered the activation of Bax and Bak in AML cells. Bak activation and release determined S1sensitivity in AML cells. Furthermore, S1-induced apoptosis was largely reduced in cells with shRNA-mediated down-regulation of Bak but not Bax. The application derivative of S1can make Mcl-1ubiquitination and enhance Bak release from Mcl-1. Our study identified Bak as a key mediator of S1-induced intrinsic apoptosis in AML cells. This study could contribute to the future clinical development of S1. |
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