Expression Of Livin In Lung Cancer Tissues And The Machenism Of Its Resistance To Apoptosis

Background It is suggested livin, a novel inhibitor of apoptosis protein (IAP), be overexpressed in a variety of carcinomas including lung cancer, which might be associated with neoplasm development, such as anti-apoptosis. However, its mechanism still remains to be clarified in future, regarding to its effect upon malignant cells to resistant apoptosis. It could be served as a potential target for cancer treatment with current evidence of investigation.Objective To explore the expression of two types of livin isoform in lung cancer tissue, and the relationship between livin expression and histopathology, chemotherapy and lymphnode metastasis. To investigate the mechanism of livin abrogating apoptosis, the associability of expression between livin and casepase-3, and the impact of livin on JNK1 pathway.Methods The expression of two types of livin isoform and caspase 3 was assayed by both reverse transcription-polymerase chain reaction (RT-PCR) and Western blot. The abrogation of livin expression in SPC-A1 strain originated from lung adenocarcinoma was carried out by microRNA interfering technique. The apoptosis of SPC-A1 cells was assayed by propidine iodide staining,flow cytometry and Cleaved Caspase 3 Western detection. JNK1 expression was assayed by both real time reverse transcription-polymerase chain reaction(Real Time RT-PCR) and Western blot.Results (1) The expression of livinαmRNA, livinβmRNA, livinαprotein in lung cancer tissues were much higher than those in para-neoplasma and benign lung tissues(44.44% versus 0.00%,0.00%,70.30% versus 0.00%,8.33%,and 55.60%versus 20.00%,16.7% respectively, P<0.05,P<0.05,P<0.05.) LivinαmRNA and its protein expression in adenocarcinoma were significantly higher than those in squamous carcinoma (50.00% versus 33.33%, 76.92% versus 38.46 % respectively, P<0.05). However, there was no statistically significant difference of livinβmRNA expression between adenocarcinoma and squamous carcinoma (64.28 % versus 75.00%, P>0.05).(2) Meanwhile, caspase3mRNA expression in lung cancer tissues was significantly lower than that in controls(P<0.01),while pro-caspase3 protein expression showed higher than that (P<0.05) .The quantitative levels of either each of two isoforms of livin mRNA expression or their sum was negatively associated with that of caspase3 mRNA (r=0.30,P<0.05; r=0.44,P<0.01; r=0.41,P<0.01),but the quantitative levels of livinαprotein seemed to potively associate with that of pro-caspase3 protein(F=3.16,P=0.053).(3)The positive expression rates of livinαmRNA,livinβmRNA,livinαprotein in lung cancer tissues with chemotherapy before operation,seemed to be higher than those in tissues without chemotherapy(50.00% versus 42.85%, 83.33% versus 66.67%,50.00% versus 44.44% ,respectively,P=1.0,P=0.63,P=1.0).However,there was no statistically significant difference of these expression between lung cancer tissues with and without lymphoid node metastasis (46.15 %versus 42.85%, 53.85% versus 85.71%,46.15% versus 64.28% ,respectively,P>0.05,P>0.05,P>0.05).(4)More apoptosis SPC-A1 cells were observed by fluorescence microscope after propidine iodide staining,hypodiploid showed up by flow cytometry and cleaved Caspase 3 upregulated by western blot detection on the 10th day or so after livin mRNAexpression was knocked down by microRNA interfering technique.(5)There was no statistically significant differences of the expressin of Caspase3mRNA, jnk1mRNA and total jnk1 protein between the groups before and after livin expression was knocked down(KD), but Cleaved-caspase3 protein upregulated, Phospho-jnk1 protein downregulated in the latter group.Conclusion(1)Two isoforms of livin are differently expressed in various histological types of lung cancer and may contribute to corresponding neoplasm development; it is presumed isoformαparticipate in the development of lung adenocarcinoma.(2)The quantitative levels of livinmRNA are negatively associated with those of caspase3mRNA,on the other hand ,the quantitative levels of livinα protein seems to be potively associate with those of pro-caspase3 protein,this may due to the fact that livin could resist against apoptosis by binding its BIR domain to pro-caspase so as to suppress caspase activation.(3)High expression of livin tends to be related to chemotherapy but not lymphoid node metastasis.(4)Livin has not so strong abrogating apoptosis effect or it has a late onset effect.(5)Livin abrogates apoptosis possibly by affecting caspase3 activation, or by upgrating jnk1 phosphorylation with its protein domain.