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One of the most important tumor suppression functions of p53 is its ability to induce apoptosis. iASPP is an inhibitory member of the ASPP protein family. It can specifically inhibit the normal function of p53 as a suppressor. The mechanism of iASPP suppressing the cell apoptotosis is through inhibiting the transactivation function of p53 on the promoters of proapoptotic genes by binding with p53. Therefore, relieving the combination of iASPP with p53 and leaving p53 free may be a useful strategy to activate p53 function. We therefore use A34, a small peptide derived from p53 linker region, to investigate the possibility of resuming the apoptosis activity of p53 by sequestering iASPP with p53 and derepressing p53. The results show that A34 can competitively combine with iASPP and therefore release p53 from iASPP; A34 can enhance the transcriptional activity of p53 on the promoters of Bax and PUMA; A34 can increase cell apoptosis and slow tumor growth in vitro and vivo. This study will open the way for using small molecule peptides that directly disturb the interaction of p53 with iASPP, thereby resume function of p53 as a suppressor., (Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.)

The ability to induce apoptosis is the most important tumor-suppression function of p53. Inhibitory member of apoptosis-stimulating protein of p53 family (iASPP) is an apoptotic-specific regulator of p53. iASPP suppresses apoptosis by inhibiting the transactivation function of p53 on the promoters of proapoptotic genes; however, the mechanism whereby iASPP influences apoptosis in tumor cells with mutant or deficient p53 has not been completely defined. In this study, we investigated the role of iASPP in the p63/p73 apoptosis pathway. iASPP inhibited apoptosis independently of p53 in tumor cells, mainly by inhibiting the transcriptional activity of p63/p73 on the promoters of proapoptotic genes. Because p63 and p73 are rarely mutated in human cancers, inhibiting the expression of endogenous iASPP may provide a useful strategy for restoring the apoptotic activity of p63 and p73 in human tumors with p53 loss or mutation. These results represent a promising new strategy for the treatment of cancers with non-wild-type p53.

ASPP family is proved to be apoptotic specific regulators of p53. Among them, iASPP acts as an inhibitor of p53. To investigate the effect of the iASPP RNAi on the apoptosis of breast cancer cell MCF-7, we transfected the recombinant plasmid PGCsilencer H1/Neo/GFP/RNAi into MCF-7. The iASPP expression was analyzed by RT-PCR and Western blot. The cell apoptosis was detected by FCM. The results show that the expression of iASPP is descended and the apoptosis rate is increased after transfection. Therefore, we conclude that inhibition of expression of iASPP may resume the ability of p53 to induce apoptosis in MCF-7 cells.

Aim: To evaluate the expressions of apoptotic signal proteins FADD, TRADD, FasL, Fas, and NFkappaB in gastric carcinoma tissues and their clinical significance., Methods: Western blot immune trace method was adopted to detect the expressions of apoptotic signal proteins FADD, TRADD, FasL, Fas, and NFkappaB in 55 tissue specimens of gastric carcinoma., Results: Five apoptotic signal proteins had different expressions in the gastric carcinoma samples and their expressions were not correlated to age (P = 0.085). Expressions of the FADD, FasL, Fas, and NFkappaB proteins reduced with increase of the volume of tumor with the exception of increased expression the TRADD protein (64.7-71.1%, P = 0.031). With gradual increase of the malignancy of gastric carcinoma tissues, expressions of the FADD, FasL, and Fas proteins decreased (78.6-28.0%, P = 0.008; 78.6-65.9%, P = 0.071; 100.0-46.3%, P = 0.014), while expressions of the TRADD and NFkappaB proteins increased (42.9-78.1%, P = 0.063; 78.6-79.1%, P = 0.134). With gradual increase of serum CEA, expression of the FADD protein decreased (62.5-34.0%, P = 0.073), but expressions of the TRADD, FasL, Fas, and NFkappaB proteins increased (0.0-80.8%, P = 0.005; 62.5-70.2%, P = 0.093; 0.0-70.2%, P = 0.003; 62.5-80.9%, P = 0.075). When compared to the tissues of gastric carcinoma without metastasis, the positive rate of expressions of the FADD and FasL proteins increased, whereas expressions of the TRADD, FADD, and NFkappaB proteins decreased. There was no significant difference between them (P = 0.095)., Conclusion: Gastric carcinoma is endurable to Fas-related apoptosis and apoptotic signal proteins are differently expressed in gastric carcinoma.