For the
cancer cells which have overcome the second mitotic clock (M2), activated
telomerase is essential and used as another marker of immortality. Many trials had been initiated to target
telomerase, which is known to be specific to
tumors. To determine the best in vitro cell system for testing the efficacy of
telomerase inhibitors, we evaluated the
telomerase activity of various
cancer cell lines and measured their telomere lengths. We also treated some
cancer cell lines with
adriamycin and measured the changes of
telomerase activity.
Telomerase activity was evaluated in various cell lines with the TRAP (telomeric repeat amplification protocol) assay.
Telomerase activity was calculated and translated into arbitrary units by computer-assisted densitometry with the control of
telomerase activity in the 293 control cell line. Also, terminal restriction fragment lengths were measured using Southern blotting. We also measured
telomerase activity and telomere lengths in 11 benign
breast tumor tissues and 19 paired
stomach cancer and normal tissues.
Cancer cell lines treated with
adriamycin we evaluated for changes of
telomerase activity and the cell proliferation by MTT assay and
dye exclusion test.
Telomerase activity of cell lines was 95.3 24.1 unit with a range of 27.6-129.6 unit, while the telomere lengths of those cell lines were variable from 5.0 to 10.4 kbp with a median of 6 kbp. In 11
cancer cell lines which were not yet firmly established, we could not detect any
telomerase activity. Low
telomerase activity was detected in only 2 benign
tumor tissues of breast with a median telomere length of 8.8 (7-10.5) kbp. Among paired 19
gastric cancer and normal tissues, only 7
cancer tissues showed weak
telomerase activity. After
adriamycin treatment,
telomerase activity in YCC-S-1, YCC-S-3, MCF-7 and MCF-7/ADR was decreased in accordance with the changes of the cell numbers.
Telomerase is specific to
cancer tissues and is expressed differently from organ to organ.
Telomerase activity by TRAP assay could be used as a chemosensitivity assay.