Abnormal expression pattern of the ASPP family of proteins in human non-small cell lung cancer and regulatory functions on apoptosis through p53 by iASPP.

The p53 protein is one of the best-known tumor suppressors. Recently discovered ASPP1 and ASPP2 are specific activators and iASPP is an inhibitor of p53. In the present study, we found that of 37 NSCLC patients, p53 alterations were detected in 20 tumors (54.1%), the mRNA expression of ASPP1 and ASPP2 was frequently dowregulated in tumor tissues, and this decreased significantly in samples expressing wild-type p53. The expression of ASPP1 and ASPP2 was downregulated and that of iASPP was upregulated in two NSCLC cell lines (the NCI-H157 cell line with altered p53 and the A549 cell line with wild-type p53). The NCI-H157 cell with higher ASPP1 and ASPP2 levels was more sensitive to cisplatin than the A549 cells with lower ASPP1 and ASPP2 levels. Downregulation of iASPP by siRNA stimulated apoptosis through p53 in two NSCLC cell lines. These findings provide new insights into the molecular mechanisms of action of the ASPP family in NSCLC and may have potent therapeutic applications.