Assessment of nipple discharge

Telomerase as tumor marker

Telomerase, a critical enzyme responsible for continuous cell growth, is repressed in most somatic cells except proliferating progenitor cells and activated lymphocytes, and activated in approximately 85% of human cancer tissues. Telomerase activity is a useful cancer-cell detecting marker in some types of cancers in which almost all cases show telomerase activation. In other types in which telomerase becomes upregulated according to tumor progression, it is a useful prognostic indicator. Detection of human telomerase reverse transcriptase (hTERT) mRNA or protein in various clinical samples is also applicable. However, careful attention should be paid to the false negative results due to the instability of this enzyme or hTERT mRNA and the existence of polymerase chain reaction inhibitors as well as the false-positive results due to the contamination by normal cells with telomerase activity. If these pitfalls are avoided, in situ detection of hTERT mRNA or protein will facilitate the reliability of telomerase as a tumor marker.

Clinical utility of telomerase in cancer

This review will focus on the clinical utilities of telomerase for human cancer diagnosis. Much attention has been focused on detection of telomerase activity and its essential components (hTR and hTERT) in cancer and noncancerous tissues. Expression of hTR and hTERT is upregulated in almost all human malignant tumors but not in benign or normal tissues with the exception of germline cells, proliferative stem cells, activated lymphocytes, and certain benign tumors. Thus, telomerase is a useful marker for cancer diagnosis and in some instance as a prognostic indicator of outcome. Telomerase detection in cells derived from breast fine needle aspirates, bronchial washes, and pancreatic juices show high sensitivity and specificity for cancer detection. In tissue samples, the level of telomerase activity is a useful prognostic indicator in certain adult cancers such as gastric and colon cancers and in neuroblastomas. Immunohistochemical detection of hTERT will facilitate exact diagnosis of the telomerase positive cells and expand the application of telomerase in cancer diagnosis.