**On the Far Side of Telomeres: The Many Roles of Telomerase in the Acquisition and Retention of Cancer Stemness**

Kerem Teralı and Açelya Yilmazer

Additional information is available at the end of the chapter

http://dx.doi.org/10.5772/65762

#### **Abstract**

It is well recognised that upregulation/reactivation of telomerase, the telomere-lengthen‐ ing enzyme, is the *sine qua non* of cellular immortalisation and malignant transformation. But there is also convincing evidence that telomerase stands at a crossroads where several developmental signalling pathways meet and that its upregulation/reactivation has ef‐ fects beyond maintaining telomere length, such as altering energy metabolism and mod‐ ulating gene expression. We believe that it is important to realise that, in a pathological context, such extratelomeric effects of telomerase are related to the emergence and persis‐ tence of the cancer stem cell (CSC) phenotype. Given the common conception of cancer stemness as a major contributor to therapy resistance and tumour relapse, a more com‐ plete annotation of biological mechanisms for its regulation by telomerase will provide the opportunity to develop telomerase-targeted anticancer therapies which kill or differ‐ entiate CSCs effectively.

**Keywords:** telomeres, telomerase, TERT, cancer stemness, CSCs, targeted anticancer ther‐ apy
