Use of exogenous hTERT to immortalize primary human cells

Abstract

A major obstacle to the immortalization of primary human cells and the establishment of human cell lines is telomere-controlled senescence. Telomere-controlled senescence is caused by the shortening of telomeres that occurs each time somatic human cells divide. The enzyme telomerase can prevent the erosion of telomeres and block the onset of telomere-controlled senescence, but its expression is restricted to the early stages of embryonic development, and in the adult, to rare cells of the blood, skin and digestive track. However, we and others have shown that the transfer of an exogenous hTERT cDNA, encoding the catalytic subunit of human telomerase, can be used to prevent telomere shortening, overcome telomerecontrolled senescence, and immortalize primary human cells. Most importantly, hTERT alone can immortalize cells without causing cancer-associated changes or altering phenotypic properties. Primary human cells that have so far been established by the forced expression of hTERT alone include fibroblasts, retinal pigmented epithelial cells, endothelial cells, oesophageal squamous cells, mammary epithelial cells, keratinocytes, osteoblasts, and Nestin-positive cells of the pancreas. In this article, we discuss the use of hTERT to immortalize of human cells, the properties of hTERT-immortalized cells, and their applications to cancer research and tissue engineering.Abbreviations: hTERT -human Telomerase Reverse Transcriptase; hTR -human Telomerase RNA.

Epigenetic Dysregulation in Virus-Associated Neoplasms

“…This may contribute to the activation of hTERT transcription by E6 in early passage human keratinocytes. hTERT expression plays an important role in the immortalization of human cells by preventing the shortening of telomeres and blocking the onset of telomere-controlled senescence (Lee et al 2004 ).…”

Harvesting the Benefits of Understanding Cancer with the Use of ?Shuttle? Era Technology- Cellular Survival Strategies and Tissue Engineering Via Grafting of Genetically Immortalized Autologous Cells

“…Another investigation [25] has outlined that exogenously stably transfected hTERT used to prevent telomere shorterning in fact can immortalize primary human cells without showing cancerous phenotypic properties. In another example, immortalization of pleomorphic adenoma has been obtained via stable hTERT transfection [26].…”

“…In the above section 'the immortality principle' I outline the situation whereby cells may be immortalized without necessarily causing their malignant transformation -even cells whose origin is that of a benign neoplasm [24][25][26].…”

Telomerase immortalization of principal cells from mouse collecting duct

“…In addition, mouse (m)TERT levels also appear to diminish over time in primary cell cultures, in part, leading to cell senescence and cell death (1,6,10,14,18). Work with human primary cell lines has shown that ectopic expression of human TERT (hTERT) can lead to continued cell replication and hence, immortalization (21,31,37,39). More importantly, recent reports have shown immortalized hTERT cells remain differentiated, thus preserving the phenotypic properties that closely resemble in vivo characteristics (37,39).…”