In collaboration with Prof. Robert Newbold, we have continued our studies on the regulation of the hTERT gene. We are focusing our efforts on the mapping of a gene on chromosome 3 that shuts off telomerase expression in the breast cancer derived cell line 21NT. We have also identified DNaseI hypersensitive sites in the second intron of telomerase expressing cells, which become extinguished in response to the putative repressor on chromosome 3. It remains to be seen whether these sites are the primary targets of regulators of telomerase expression or whether these chromatin alterations are the downstream consequence of the activity of cis-acting elements elsewhere in the gene.
In collaboration with Boehringer-Ingelheim we have started to characterize a small molecule inhibitor (BIBR1532) that inhibits human telomerase in vitro and in vivo. Treatment of cancer cells leads to progressive telomere shortening with no acute cytotoxicity but a proliferation arrest after a characteristic lag period with hallmarks of senescence. The inhibitor also shows efficacy using an in vivo mouse xenograph model. BIBR1532 also inhibits recombinant human telomerase and kinetic experiments indicate that it BIBR1532 is a mixed type noncompetitive inhibitor that binds telomerase in a site different from the binding sites for deoxyribonucleotides and the DNA primer, respectively. BIBR1532 belongs to a new category of telomerase inhibitors with mechanistic similarities to non-nucleosidic inhibitors of HIV1 reverse transcriptase.
Publications:
Szutorisz, H., Palmquist, R., Roos, G., Stenling, R., Schorderet, D., Reddel, R., Lingner, J., and Nabholz, M. Rearrangements of minisatellites in the human telomerase reverse transcriptase gene are not correlated with its expression in colon carcinomas. Oncogene 20, 2600-2665 (2001).
Wenz, C., Enenkel, B., Amacker, M., Kelleher, C., Damm, K., and Lingner, J. Human telomerase contains two cooperating telomerase RNA molecules. EMBO J. 20, 3526-3534 (2001).
Ducrest, A.-L., Amacker, M., Matthieu, Y., Cuthbert, A. P., Trott, D. A., Newbold, R. F., Nabholz, M., and Lingner, J. Regulation of human telomerase activity: repression by normal chromosome 3 abolishes nuclear telomerase reverse transcriptase transcripts but does not affect c-Myc activity. Cancer Res. 61, 7594-7602 (2001).
Damm, K., Hemmann, U., Garin-Chesa, P., Hauel, N., Kauffmann, I., Priepke, H., Niestroj, C., Daiber, C., Enenkel, B., Guillard, B., Lauritsch, I., Müller, E., Pascolo, E., Sauter, G., Pantic, M., Martens, U. M., Wenz, C., Lingner, J., Kraut, N., Rettig, W. J., and Schnapp, A. A highly selective telomerase inhibitor limiting human cancer cell proliferation. EMBO J. 20, 6958-6968 (2001).
Pascolo E., Wenz C., Lingner J., Hauel N., Priepke H., Kauffmann I., Garin-Chesa P., Rettig W. J., Damm K., Schnapp A.. Mechanism of human telomerase inhibition by BIBR1532, a synthetic, non-nucleosidic drug candidate. J. Biol. Chem. in press.
Lingner, J., and Wenz, C. The makings of telomerases. In Human Cancer and the Biology of Telomeres and Telomerases, edited by Guido Krupp (Landes Bioscience).
http://www.eurekah.com/reports/geneexpression/krupp/16/lingner16.html.Ducrest, A.-L., Szutorsiz, H., Lingner, J., and Nabholz, M. Regulation of the human telomerase reverse transcriptase gene. Oncogene 21, 541-552 (2002).
