that it does not involve the inactivation of tumor suppressor gene, which might lead to cancer formation. Enhancement Over-expression of hTERT in stem cells changes the properties of the cells. hTERT over-expression increases the stem cell properties of human mesenchymal stem cells. The expression profile of mesenchymal stem cells converges towards embryonic stem cells, suggesting that these cells may have embryonic stem cell-like properties. However, it has been observed that mesenchymal stem cells undergo decreased levels of spontaneous differentiation. This suggests that the differentiation capacity of adult stem cells may be dependent on telomerase activities. Therefore, over-expression of hTERT, which is akin to increasing telomerase activities, may create adult stem cells with a larger capacity for differentiation and hence, a larger capacity for treatment. Increasing the telomerase activities in stem cells gives different effects depending on the intrinsic nature of the different types of stem cells. Hence, not all stem cells will have increased stem-cell properties. For example, research has shown that telomerase can be upregulated in CD34+ Umbilical Cord Blood Cells through hTERT over-expression. The survival of these stem cells was enhanced, although there was no increase in the amount of population doubling. Clinical significance Deregulation of telomerase expression in somatic cells may be involved in oncogenesis. Genome-wide association studies suggest TERT is a susceptibility gene for development of many cancers, including lung cancer. Role in cancer Telomerase activity is associated with the number of times a cell can divide playing an important role in the immortality of cell lines, such as cancer cells. The enzyme complex acts through the addition of telomeric repeats to the ends of chromosomal DNA. This generates immortal cancer cells. In fact, there is a strong correlation between telomerase activity and malignant tumors or cancerous cell lines. Not all types of human cancer have increased telomerase activity. 90% of cancers are characterized by increased telomerase activity. Lung cancer is the most well characterized type of cancer associated with telomerase. There is a lack of substantial telomerase activity in some cell types such as primary human fibroblasts, which become senescent after about 30–50 population doublings. There is also evidence that telomerase activity is increased in tissues, such as germ cell lines, that are self-renewing. Normal somatic cells, on the other hand, do not have detectable telomerase activity. Since the catalytic component of telomerase is its reverse transcriptase, hTERT, and the RNA component hTERC, hTERT is