| Telomere's shorting and activation of telomerase play an important role in cell's senescence> immortalization and rumorigenesis. Telomerase activation is thought to be the molecular basis of unlimited proliferation of malignant tumors. It has been improved that almost all the malignant tumors and tumor cell lines had telomerase activity while normal somatic cells didn't have,except germ cells ^ hemopoietic stem cell and other high proliferative tissues.Telomerase is a specialized ribonucleoprotein polymerase including it's template RNA and reverse transcriptase. It can catalyes the synthesis of telomere DNA with it's own template in order to compensate for the cell death because of telomere shorting and chromsome unstability. So telomerase is a ideal target of tumor therapy. There are several strategys targeting at hTR, among them, antisense hTR can inhibits the template region 5'-CUAACCCUAAC-3' of hTR complementary to human telomere sequence (TTAGGG)n, ultimately suppress telomerase activity,start apoptotic mechanism and induce cell cycle arrest.Oral squamous cell carcinoma(OSCC) and adenoid cystic carcinoma of Salivary gland(SACC) are most common malignant rumors in stomatology. SACC is characterized by it's high recurrence and distant metastasis. In situhybridization (ISH) was employed to detect the hTR and hTRT expression in these two tumor tissues. It's observed that hTR expression was significantly increased in SACC compared with normal parotide glands(P<0.001).hTR positive signal was stronger in tubular type and solide type, statistics showed some correlations between hTR level and SACC's phenotypes(P<0.05).It's also observed that hTR expression were related to cell proliferation. hTRT positive rate in OSCC, metaplasia and normal mucosa were 82.7%,41.7% and 20% respectively,hTRT level had no statistical relations with histological grades of OSCC(P>0.05). The correlation between telomerase and PCNA showed telomerase positive cells were most in proliferating stage, and it suggested that telomerase might have some relevance with cell cycle and cell cycle regulators. Telomerase activition in OSCC and SACC made it possible for their telomerase inhibition therapy.In this study, the telomerase activity in Sacc83 cell line and Tca8113 cell line was examined by TRAP-PCR-ELISA. Via the mediation of lipofectamine, the eukaryotic expression vector PBBS212-ahTR expressing antisense hTR under the control of the MPSV promoter was transfected into the two cell lines. We recognized the ahTR specific product with DIG-labeled ahTR oligonucleotide only in the ahTR transfected cells, but not in parental and the empty vector transfected cells. Hygromycin was used to select the antibiotics resistant clones for 10 days, ahTR transfected Sacc83 cells maintained about anther 20 days and their proliferation ability were greatly decreased. After approxmately 5-7 population doubling time, they all died. Apoptosis of these cells was testified by TUNEL method and transmission electron microscopy, hTR and PCNA expression decreased. To estimate the in vitro feasibility of this study, a humancancer-nude mouse model was established. Mixture of lipofectamine and PBBS212-ahTR was injected into Sacc83 transplanted tumors in nude mice, after 12 days, the injection site and it's adjacent tissue collapes without observed side-effect. Large amount of apoptotic cells were found in HE staining of these tumors. Growth of ahTR transfected TcaSl13 cells greatly reduced but still can be passaged on. Flow cytometer detection found that compared with it's parental cells and control group, TcaS113-ahTR had an increased Go/Gj phase cells and decreased S phase cells, PI lowered down accompanied with occurrence of an apoptotic peak, which suggested the apoptotic effect and GI arrest of antisense hTR transfection. TcaS 113-ahTR cells presented an reduced telomerase activity(A450-A690)from 2.012 to 1.535 while p21(CDKI,the maim Gi/S check point inhibitor) activity increased. Antisense hTR may serve as "gene seal", thus inhibite telomerase activi...
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