Expression Of POKemon And P14ARF In Colorectal Carcinoma Cells And Tissues

POKemon, a POK erythroid myeloid ontogenic factor, is a member of thePOK protein family which is coded by zbtb7 gene locating the chromosome19p13.3 and is originally identified as a protein that binds specifically to a HIV typepromoter element. The common character of POK family is that it consists of aPOZ/BTB domain of NH₂-terminal and mediate homodimerization ofCOOH-terminal. The zinc finger of COOH-terminal mediates specific DNArecognition and binding. Maeda's report has revealed that POKemon is a key factor inMEFs tumor transformation and proliferation, in another word, the POK proteins playessential roles in development and differentiation and oncogenisis of cancer.Moreover, POKemon directly binds with p19ARF promoter and represses itstranscription.p14ARF is the alterative reading frame gene of INK4a which represses thefunction of the cell cyclin dependent kinase 4(CDK4).It locates in chromosome9p21,containing 3 extrons (the Extronl Extron2 Extron3) and 2 introns. The proteinnamed p14ARF which is 14 Kd is coded by 3 extrons(in small rat the homologousprotein is p19ARF), consisting of 133 amino acids, p14ARF binds with mdm2 andobstructs its shuttle from nuclear to cytoplasm,thus recovering and protecting thestability of p53 level, strengthening the restrict order of p53 in the G1-S and G2-Mby preventing cell cyclin in the process from G1 to G2.To study the expression and correlation of POKemon and p14ARF in thecolorectal carcinoma cells, mRNA and protein was detected respectively by RT-PCRand immumocytchemistry. The results indicated that in 5 colorectal carcinoma cell lines, POKemon was positively transcripted in SW620,SW480,SW480/M5,LOVO,whileit was negatively transcripted in HCT116. The expression of protein was similar tomRNA. Thus it was concluded that POKemon and p14ARF was positive in colorectalcarcinoma cell lines and the function of the two genes was negative correlation.For the further study, expression of Pokemon and p14ARF was detected innormal tissue and carcinoma tissue obtained from colorectal carcinoma patients byimmumohischemistry.The results indicated that POKemon was highly expressed incarcinlma tissue than that in normal epithelium(x²=47.143, P=0.000) and is associatedwith differention (R=0.360,P=0.007). p14ARF was lower expressed incarcinoma tissue than normal epithelium (x²=10.555, P=0.001) and is associatedwith differention.Morover,in normal epithelium it was negative correlation betweenPOKemon and p14ARF (r=-0.289,P=0.033,),in adenocarcinoma tissues it is negativecorrelation between POKemon and p14ARF (r=-0.981,P=0.000). By contrast, therewas no relation of the function of POKemon and p14ARF in carcinoma tissues. It ispossible that up-stream or down-stream gene controlls and infers their facility.Furtherstudies will be necessary to precisely determine how POKemon and p14ARFexpression is regulated both in normal and cancerous tissues.In closing,our findings demonstrate that the expression of POKemon andp14ARF highly relates with malignant transformation and development of colorectalcarcinoma. POKemon and p14ARF may be an attractive therapeutic target forcolorectal carcinomar therapy in view of their essential roles in oncogenictransformation.