Antitumor effect of COOH-terminal polypeptide of human TERT is associated with the declined expression of hTERT and NF-κB�p65 in HeLa�cells

Abstract

Abstract. Human telomerase reverse transcriptase (hTERT) plays an important role in the development of tumors and has been investigated as a potent target for anticancer therapy. In the present study, we constructed a recombinant adenovirus, Ad-EGFP-C197 which was capable of expressing COOH-terminal polypeptide of hTERT (amino acid 936-1,132, termed as C197 for the reason that it contains 197 amino acids). Infection of HeLa cells with Ad-EGFP-C197 suppressed the activity of telomerase, decreased the expression of hTERT and NF-κB p65, and induced rapid growth delay and apoptosis of HeLa cells in vitro. In nude mice xenografted with HeLa tumors, injection of Ad-EGFP-C197 into the tumor nodule significantly slowed tumor growth and promoted tumor cell apoptosis, as well as reduced the expression of NF-κB p65 in tumor tissues. In the present study, we suggest that the antitumor effect of C197 is associated with the declined expression of hTERT and NF-κB p65. Our results highlight the potential of C197 in tumor therapy. IntroductionTelomeres are the ends of linear chromosomes in eukaryotic cells and are characterized by the TTAGGG repeats (1) that are bound by the shelterin complex (2). Telomeric DNA shrinks with each cellular division due to incomplete replication of TTAGGG repeats, which eventually results in DNA damage and replicative senescence (3). Telomerase is a particular ribonucleoprotein complex which specifically adds TTAGGG repeats to the ends of eukaryotic chromosomes, thus counteracts the shortening of telomeric DNA during cell division. The activity of telomerase is not detected in most human somatic cells (4). However, telomerase is reactivated in vast majority of human cancer cells (5) and plays a critical role in the progression of human cancer (6). Recently telomerase has been found to exert extra-telomeric effects via the modulation of NF-κB (7,8) and Wnt/β-catenin signaling pathways (9,10). These non-canonical functions are associated with the development and progression of human cancer. In fact, telomerase has been investigated as a potent target for anticancer therapy (11).The major components of human telomerase are tolemerase RNA (hTR) and telomerase reverse transcriptase (hTERT). While hTR subunit serves as a template, hTERT subunit catalyzes the elongation of telomeric DNA. Three main structural domains of hTERT have been identified: NH 2 terminus that binds DNA and RNA, central catalytic RT region and a short COOH terminus (12). Although the function of COOH terminus is the least-characterized, it has been found to mediate the nuclear translocation of telomerase (13) and is essential for the in vivo activity of human telomerase (14). Recent studies showed that ectopic expression of C27 (amino acid 882-1,132 of hTERT) reduces the growth and tumorigenicity of tumor cells (15-19) and sensitizes tumor cells to 5-fluorouracil-induced growth inhibition and apoptosis (20). C27 does not affect telomerase activity. The unclearly illustrated mechanisms include the induction of telomere dysfunction (1...

Oncolytic Adenoviruses: Strategies for Improved Targeting and Specificity

“…Promoter-based CRAd Lung, prostate, ovarian, pancreatic cancer, adult T cell Leukemia/Lymphoma, glioma, meduloblastoma, sarcomas [69,[209][210][211][212][213][214][215][216][217][218][219][220][221][222] CRAds based on Interaction of essential viral genes withTumor-specific proteins colon, breast, non-small cell lung, head and neck, and pancreatic tumors, cervical carcinoma, glioblastoma, cancers with disturbed Rb pathway [172,[223][224][225][226][227][228] As with genes, several endogenous miRNAs and other lncRNAs can be targeted to enhance the detargeting and retargeting ability of OAdVs [229]. For instance, liver, where most of the OAdV sequestration is observed, overexpresses miRNA122 and miR145.…”

“…The most prominent examples include Cox2 in gastric cancer and pancreatic cancer [ 69 , 209 , 210 , 211 ] and survivin in adult T cell leukemia or lymphoma [ 212 , 213 , 214 , 215 ] and lung, ovarian, and pancreatic cancers. The HIF-responsive promoter in gliomas and meduloblastomas [ 216 , 217 ]; and hTERT (human telomerase reverse transcriptase) in bone and soft tissue sarcomas, as well as prostate, ovarian, esophageal, and GI cancers [ 218 , 219 , 220 , 221 , 222 , 260 , 261 ], among many others.…”