Effects of ectopic expression of human telomerase reverse transcriptase on immortalization of feather keratinocyte stem cells

Telomerase activation in the treatment of aging or degenerative diseases: a systematic review

Telomeres are protective structures that are shortened during the lifetime, resulting in aging and degenerative diseases. Subjects experiencing aging and degenerative disorders present smaller telomeres than young and healthy ones. The size of these structures can be stabilized by telomerase, an enzyme which is inactive in adult tissues but functional in fetal and newborn tissues and adult testes and ovaries. The aim of this study was to perform a systematic review to evaluate the effect of telomerase activation in the treatment of degenerative and aging disorders. We accomplished the search using the Pubmed interface for papers published from September 1985 to April 16th, 2020. We found twenty one studies that matched our eligibility criteria. I concluded that telomerase is probably a potential and safe treatment for aging and degenerative diseases, demonstrating neither side effects nor risk of cancer in the selected studies. Further studies in humans are needed to confirm safety and efficiency of this treatment.

Immortalization of chicken preadipocytes by retroviral transduction of chicken TERT and TR

The chicken is an important agricultural animal and model for developmental biology, immunology and virology. Excess fat accumulation continues to be a serious problem for the chicken industry. However, chicken adipogenesis and obesity have not been well investigated, because no chicken preadipocyte cell lines have been generated thus far. Here, we successfully generated two immortalized chicken preadipocyte cell lines through transduction of either chicken telomerase reverse transcriptase (chTERT) alone or in combination with chicken telomerase RNA (chTR). Both of these cell lines have survived >100 population doublings in vitro, display high telomerase activity and have no sign of replicative senescence. Similar to primary chicken preadipocytes, these two cell lines display a fibroblast-like morphology, retain the capacity to differentiate into adipocytes, and do not display any signs of malignant transformation. Isoenzyme analysis and PCR-based analysis confirmed that these two cell lines are of chicken origin and are free from inter-species contamination. To our knowledge, this is the first report demonstrating the generation of immortal chicken cells by introduction of chTERT and chTR. Our established chicken preadipocyte cell lines show great promise as an in vitro model for the investigation of chicken adipogenesis, lipid metabolism, and obesity and its related diseases, and our results also provide clues for immortalizing other avian cell types.

Involvement of transcription repressor Snail in the regulation of human telomerase reverse transcriptase (hTERT) by transforming growth factor-β

Human telomerase reverse transcriptase (hTERT), a catalytic subunit of telomerase, is the primary determinant for telomerase enzyme activity, which has been associated with cellular immortality. Expression of the hTERT gene is regulated by various extracellular (external) stimuli and is aberrantly up-regulated in more than 90% of cancers. Here we show that hTERT gene expression was repressed in response to transforming growth factor-β (TGF-β) by a mechanism dependent on transcription factors Snail and c-Myc. TGF-β activated Snail and down-regulated c-Myc gene expression. In addition, ectopic expression of Snail strongly inhibited hTERT promoter activity, although co-expression of c-Myc abrogated this effect. Chromatin immunoprecipitation (ChIP) analysis revealed that TGF-β decreased c-Myc occupancy and dramatically increased recruitment of Snail to the E-box motifs of the hTERT promoter, thereby repressing hTERT expression. Our findings suggest a dynamic alteration in hTERT promoter occupancy by Snail and c-Myc is the mechanistic basis for TGF-β-mediated regulation of hTERT.

Circulating cell-free human telomerase reverse transcriptase mRNA in plasma and its potential diagnostic and prognostic value for gastric cancer

BACKGROUND

Our aims were to detect circulating cell-free human telomerase reverse transcriptase (hTERT) mRNA in the plasma of gastric cancer patients and evaluate its potential diagnostic and prognostic value.

METHODS

Real-time quantitative reverse transcription-polymerase chain reaction was employed to detect circulating cell-free hTERT mRNA from 118 gastric cancer patients, 40 chronic atrophic gastritis (CAG) patients, and 58 healthy controls.

RESULTS

Circulating cell-free hTERT mRNA was detected in all gastric cancer patients, 39 (97.5 %) CAG patients and 56 (96.6 %) healthy control individuals, respectively. However, it was higher in gastric cancer than in CAG and healthy controls (all at P < 0.05). Moreover, its high level was significantly correlated with clinical stages (P < 0.001) and lymph nodes metastasis (P < 0.001). There was no difference between circulating cell-free mRNA and other parameters. The area under the receiver operating characteristic (ROC) curve was 0.891, and the optimal cut-off point was 0.18, providing a sensitivity of 66 % and a specificity of 87 %. The ROC analysis showed that the diagnosis capability of circulating cell-free mRNA was statistically significantly higher than that of carcinoembryonic antigen (CEA) and cancer antigen 19-9 (CA19-9), alone [CEA (0.656); CA19-9 (0.722)] or in combination (0.756). Kaplan-Meier analysis demonstrated a correlation between increased circulating cell-free hTERT mRNA and reduced disease-free survival (P < 0.001) and overall survival (P < 0.001). Cox analysis indicated that it was an independent prognostic factor for disease-free survival and overall survival.

CONCLUSIONS

We concluded that circulating cell-free hTERT mRNA might serve as a potential and useful noninvasive tumor marker for gastric cancer.