Correlations Among Expression Levels Of FBX4, CCND1 And HTERT In Non-small Cell Lung Cancer Tissue

Background:Lung cancer is the most leading cause of cancer deaths and the highest incidence rate in worldwide.Recent studies revealed that abnormality of Ubiquitin-Proteasome pathway is one of reasons that cells obtain infinite proliferation ability and immortality in malignant tumor.The ubiquitin -proteasome system to which was recently paid close attention plays a pivotal role in protein homeostasis.The capital role of the system is to degrade some regulatory proteins with short half-life and mis-folded,damaged,or mutant proteins with abnormal conformations in cells.Commonly,the target proteins is polyubiquitinated by means of multiubiquitination,and the polyubiquitinated proteins are degraded by the 26S proteasome.Ubiquitin is a polypeptide comprised of 76 amino acids that can be covalently attached to target proteins through an enzymatic cascade that includes three enzymes:E1,E2 and E3.the ubiquitin-activating enzyme,E1,utilizes the energy of ATP to activate ubiquitin and passes ubiquitin to the ubiquitin-conjugating enzyme,E2.The E2 together with the E3,or ubiquitin ligase,attaches ubiquitin molecules to substrates. SCF^{Fb×4/αB-crystallin} is one of E3 ligases,for the SCF^{Fb×4/αB-crystallin}(Skp1/Cull/F-box protein/αβ-crystallin) ligase,the FBX4 protein acts as a substrate-specific receptor while the remaining components of the ligase(Skp1/Cull/Rbxl) are common for various substrates.Recent studies revealed that Overexpression of FBX4 triggered cyclin D1 ubiquitination and increased cyclin D1 turnover.Impairment of SCF^{Fbx4/αB-crystallin}) function attenuated cyclin D1 ubiquitination,promoting cyclin D1 overexpression and accelerated cell cycle progression.Consistent with a putative role for a cyclin D1 E3 ligase in tumorigenesis,FBX4 expression was reduced in tumor-derived cell lines and a subset of primary human cancers including including prostate,thyroid and breast adenocarcinomas andlymphoma,in which cyclin D1 is overexpression. Cyclin D1,one of oncogenes,is the most important member of G1 Cyclin Family.It is overexpressed frequently in a wide range of human cancers such as those originating from the esophagus,head and neck,and breast,and overexpression is considered an early,causative event in some of these cancers.Human telomerase reverse transcriptase (hTERT) is one of Core Components of telomerase,which plays a pivotal role in occurrence and progression of tumor.Although data regarding cyclin D1 expression,hTERT expression and correlation with essential clinicopathologic parameters have been reported in non-small cell lung cancer(NSCLC),there is no report about association of fbx4 with clinicopathologic factors,CCND1 mRNA expression and hTERTmRNA expression and the relationship between CCND1 mRNA expression and hTERTmRNA expression.This question, which is the mian purpose of present experiment,attracted our interest.Objectives:This present study was carried out to provide data to reveal the possible mechanisms of Fbx4 in non-small cell lung cancer.Methods:Forty pairs of lung cancer tissues and corresponding adjacent normal lung tissues were obtained from patients in Department of Chest Surgery,First Affiliated Hospital, Zhejiang University School of Medicine from 2007 to 2008.The quantity of fbx4 and CCND1 gene mRNA expression was detected by real-time PCR with ABI 7300 Sequence Detection System.PCR was carried out to determine the mRNA level of the hTERT gene.All the detection items in this study were repeated at least 3 times.Statistical analysis was done using SPSS software(SPSS 16.0).The data was expressed as mean±SD and the statistical significance of the differences between control and target genes was determined by t test.The Chisquared test or Fisher's exact test were used appropriately to assess association within and between molecular indices and the pathological or clinical factors.P-value＜0.05 was considered as significant.Results:PCR assay indicated that expression of hTERT in lung cancer tissues is significant higher than corresponding adjacent normal lung tissues(p＜0.01).Real-time PCR assay indicated that Fbx4 mRNA levels and CCND1 mRNA levels were low in tumors examined as compared to corresponding normal controls,but there isn't statistical significance.And our data suggest fbx4 mRNA expression isn't associated with CCND1 mRNA expression,hTERT mRNA expression and clinicopathologic factors in NSCLC. Conclusions:In this study,the Correlations among expression levels of FBX4,CCND1 and hTERT in non-small cell lung cancer tissue was analyzed.Our data suggests that hTERT plays a pivotal role in occurrence and progression of tumor,and CCND1 and hTERT mightn't be degraded by Ubiquitin-Proteasome pathway that is mediated by Fbx4.The experimental results could provide some theoretical support for taking the research of NSCLC further.