Study Of Gene Expression Profile Changes In Non-Small Cell Lung Cancer Using Subtractive Hybridization Method And Study Of Biological Functions Of TIG2 Gene

The studies on functional genome become one of directions with the complement of human genome sequence. Our focus on screening related functional genes to lung carcinogenesis progression using subtractive hybridization method. We have constructed differentially expressed cDNA libraries by gene expression profile changes in clinical lung tumor tissue compared with its parental normal lung tissue. We have screened a group of genes proofed by DNA sequencing and RT - PCR, which is the most important contributes to lung tu-morigenesis. We selected TIG2 ( Tazarotene - induced gene 2 ) from screened genes to further insight into the effect on lung tumorigenesis.We found that TIG2 mRNA is downregulated or silenced in lung cancer cells ,but constitutively expressed in normal lung cells by RT - PCR. TIG2 cDNA was cloned from normal lung cell(WI -38) , and mammalian recombinant expression plasmids containing TIG2, named pFLAG - CMV/HG2, pCI - neo/ HG2, respectively, then lung cancer cells ( A2,LH7 ) were transfected with these recombinant plasmids. The encoded product of TIG2 was located cytoplasm and secreted by immunofluorescence assay. TIG2 gene was still silenced in lung cancer cells during treatment with variant concentration of retinoic acid, so the cultured lung cancer cells is refractory cells. Interestingly, TIG2 gene was re -expressed after treatment with demethylating reagent (5 - Aza - CdR) , so our inference is that the silence of TIG2 gene in lung cancer was associated with DNA methylation. The promoter region of TIG2 gene existed CpG islands predicted with MethPrimer software, combined with retinoic acid receptor β( RARβ ) usually being methylation and silence in lung cancer,so the silence of TIG2 gene in lung cancer cells was related to the DNA methylation of TIG2 and/or retionic...