The Mutation, Expression And Related Signal Pathway Of PTEN In Non Small Cell Of Lung Cancer And Correlation With Patients' Prognosis

IntrodutionLung Cancer is one of the most common and maligant tumors in the world and the patients have poor prognosis. About 80%of lung cancer is non small cell of lung cancer (NSCLC). Just like some tumors, the development of NSCLC is a complex process involving many genes and factors. The phosphorylation level of protein tyrosine, precisely regulated by PTKs and PTPs, plays an important role in the cellular signal transduction and cell cycle progression. As many PTKs are encoded by pro-oncogenes, it has been postulated that some of PTPs may act as tumor suppressor gene for a long time. But this assumption is not testified until the discovery ofPTEN tumor suppressor gene.Since characterized and cloned seperatedly by Jing Li, Peter A. steck and DaMing Li. in 1997, PTEN has been found to be inactivated by point mutations or homozygous deletions in many malignant tumors such as glioblastoma, protate carcinoma and breast carcinoma. Although much work has been done on the relationships between PTEN gene and some other tumors, there are few reports on the relationship between PTEN mutation and NSCLC. And so far, to our knowledge there is no unified view on PTEN protein expression during the occurrence and development ofNSCLC.MethodsIn the study, we collected 61 NSCLC samples with complete follow-up data and 20 cases near cancer tissue as control. At first, we extracted 30 cases of NSCLC tissue s DNA, then designed primers of PTEN 3.5.7,8 exons.consequently got the amplification production by PCR and identified by agarose gel electrophoresis.The next step, we sended the ones which have amplification productions to the detecting company, then we could obtain the sequence result. We also used immunohistochemistry to detect PTEN,PI3K and P-Akt protein expression in all samples. At last, we usedχ2 test to analyze the mutation and protein expression outcomes and analyzed survival aspects by single factor Kaplan-Meier assay and Cox-Model.ResultsIt was shown that two kinds of novel point mutations and one case of PTEN EXON5,7 and 8 loss of homozygosity in NSCLC samples used were identified by PCR and DNA sequencing methods. Among them, one case of base substitutions was found in 7-intron region(46bp of downstream of exon73'-flanking region,116033 G→A), while other 1 case of point mutation localized in 7-intron region(between 2 bp and 3 bp of upstream of exon85-flanking region insert a T,11859-11860).By immunohistochemistry, the expression level of PTEN protein in NSCLC were significantly lower than in tumor-sorrounding lung tissues(P<0.05). Besides the low expression level of PTEN protein was significantly associated with squamous cancer, late clinical stage,lymphangitic metastases and short survival time after operation(P< 0.05). However no significant relationship was found with age and histological grading(P>0.05).Spearman correlation test showed that the expression level of PTEN protein was signicantly positive correlation with PI3K and Akt protein expression. Now, it demonstrated the negative regulation between PTEN and PI3K/Akt signal pathway.Cox multiple factor proportion risk model showed that among many factors, only smoking and loss expression of PTEN were risk factors of patients survival time after operation.Conclusions Our results suggest that mutation,loss expression of PTEN gene and the disbalance between PTEN and PI3K/Akt signal pathway may be involved in the occurrence and development of NSCLC. which sustained the malignant phenotype of tumor and facilitated tumor development. Then we believe that PTEN may be implicated in the genetherapy of NSCLC.