Adenovirus Ad-p53AIP1-mediated gene therapy and its regulation of p53-MDM2 interactions

Overexpression of Tumor Protein p53-regulated Apoptosis-inducing Protein 1 Regulates Proliferation and Apoptosis of Breast Cancer Cells through the PI3K/Akt Pathway

Purpose

Tumor protein p53-regulated apoptosis-inducing protein 1 (TP53AIP1) functions in various cancers. We studied the effect and molecular mechanism of TP53AIP1 in breast cancer.

Methods

The degree of correlation between TP53AIP1 expression and overall survival in patients with breast cancer was obtained from the online The Cancer Genome Atlas database. Six of the TP53AIP1 levels in the tumor and adjacent non-tumor tissues randomly selected from 38 breast cancer patients were determined. Transgenic technology was used to enhance the expression of TP53AIP1 in breast cancer cell lines, MDA-MB-415 and MDA-MB-468, and to observe the effects of gene overexpression on the proliferation, cell cycle, and apoptosis of breast cancer cells. The molecular mechanism of association between cell cycle- and apoptosis-related factors and the phosphoinositide 3-kinases/protein kinase B (PI3K/Akt) pathway was also studied.

Results

The messenger RNA and protein expression levels of TP53AIP1 in cancer tissues were significantly lower than those in the control group. TP53AIP1 overexpression inhibits cell viability. The mechanism of TP53AIP1 inhibition of proliferation and growth of breast cancer cells includes cell cycle arrest, apoptosis promotion (p < 0.01), promotion of the expression of cleaved-caspase-3 (p < 0.01), cleaved-caspase-9 (p < 0.01), B cell lymphoma/leukemia-2 (Bcl-2)-associated X protein, and p53 (p < 0.01), and the inhibition of Bcl-2, Ki67, and PI3K/Akt pathways (p < 0.01).

Conclusion

TP53AIP1 may be a novel tumor suppressor gene in breast cancer and can potentially be used as an effective target gene for the treatment of breast cancer.

Anti-apoptotic roles for the mutant p53R248Q through suppression of p53-regulated apoptosis-inducing protein 1 in the RA-derived fibroblast-like synoviocyte cell line MH7A

We previously reported that somatic mutations in the p53 gene accumulated at a higher frequency in AID(activation induced cytidine deaminase)(+) RA-FLS, which may result in the malfunction of p53, causing the tumor-like properties of RA-FLS. Among the p53 mutations identified from 3 sources of AID(+) RA-FLS, we focused on the p53R248Q mutation because it was reported to enhance the invasiveness of lung cancer cells and to have dominant-negative activity for pro-apoptotic molecules. We obtained cDNA encoding the p53R248Q mutant and introduced it into the MH7A RA-FLS cell line. P53R248Q dramatically suppressed the expression of the pro-apoptotic molecule p53AIP1 even under oxidative stress, which normally upregulates p53AIP1, leading to apoptosis. Moreover, overexpression of p53AIP1 increased apoptosis, whereas p53AIP1 knockdown rescued the cells from apoptosis. Together, these studies indicate the critical role of p53AIP1 under DNA damaging stresses for cell fate determination in RA-FLS containing the p53R248Q mutation.