Differential Expression Of ASPP1 And ASPP2 In Non-small-cell Lung Cancer Cell Lines

Background and Objective: p53,a crucial tumor suppressor gene , is located on human chromosome 17q13.1 and is also one of the most frequently mutated genes in human cancer. p53 protein, as a tumor suppressor, mediates apoptosis and DNA repair.ASPP protein family including ASPP1, ASPP2, iASPP has been involved in the apoptotic function of p53. A number of literatures have show that ASPP1 and ASPP2 specifically stimulated the apoptotic effect of p53, whereas iASPP, the third member of the ASPP family, is the most conserved inhibitor of P53-mediated apoptosis. It has been expected that expression levels of ASPP1 and ASPP2 would be reduced in human carcinoma bearing wild-type p53. Samuels-L evet al examined the expression levels of both ASPP1 and ASPP2 in breast cancer samples expressing wild-type p53 with semiquantitative RT-PCR technique, showing that the levels of ASPP1 and ASPP2 mRNA were decreased in 24, 9 of 40 samples, respectively. In addition, Liu et al examined the expression levels of ASPP family members mRNA in three leukemia cell lines and Zhang et al analyzed the mRNA expression of iASPP in acute leukemias. Mori T et al found that ASPP2 mRNA levels were highly variable in various human cancer cell lines and higher ASPP2 mRNA expression was associated with the chenmosensitivity to cis-diamine-dichloroplatinum (CDDP).Recently, X Agirre et al have reported that downregulated expression of ASPP1 in patients with ALL was detected and was correlated with a poor prognosis.In this study, we investigate the expression of ASPP family in NSCLC cell lines in order to explore the relationship between p53 status and the expression of the ASPP family members.Methods: RQ-RT-PCR was performed to detect ASPP1 and ASPP2 mRNA in NCI-H157 and A549 cell lines. Western blot was used to detect ASPP proteins in the cell lines. Chemosensitivity of the cell lines to CDDP was analyzed by MTT assay, and flow cytometry (FCM) was developed to compare the discrepancy of apoptosis of two cell lines.Results: ASPP mRNA expression level was higher in NCI-H157 than in A549 cell line. In NCI-H157 cell line, there was stronger ASPP protein expression than in A549 cell line. IC50 values of NCI-H157 and A549 are 3.7ug/ml, 10.48ug/ml respectively. The apoptosis cell rates of NCI-H157 and A549 are 12.76%, 4.54% respectively.Conclusion: ASPPs mRNA and protein expression levels were stronger in NCI-H157 than that in A549 cell line. The chemosensitivity of CDDP to NCI-H157 was higher than that to A549. There is a clear trend that the higher expression levels of ASPPs may be related to the chemosensitivity of CDDP.