Telomeres and telomerase in T cells of tumor immunity

Telomeres are specific nucleoprotein structures at the end of a eukaryotic chromosomes characterized by repeats of the sequence TTAGGG and regulated by the enzyme telomerase which prevents their degradation, loss, rearrangement and end-to-end fusion. During activation, T lymphocytes actively divide, albeit through only a finite number of cell divisions due to shortening of telomeres. However, studies have demonstrated that human telomerase reverse transcriptase (hTERT), thought to be the major component regulating telomerase activity, can enhance the proliferation of T cells when overexpressed. There are many treatments for cancers, most of which are targeting the telomere and telomerase of tumor cells. However, the hTERT-transduced T cells improve their potential for proliferation, making them an appropriate cell resource for tumor adoptive immunotherapy, a procedure whereby T cells are isolated from patients, expanded ex vivo and eventually delivered back into the patients, provides a new approach for tumor therapy through improved overall survival rates in cancer patients. In this review, we will focus on the telomerase activity in T cells, the regulation of telomerase activity, and hTERT-transduced T cells used in adoptive immunotherapy for cancer.