Anti-Cancer drugs - Telomeres and Cell Senescence

1. Anti-Cancer drugs -Telomeres and Cell Senescence • Chromosomes within animal and human cells have a group of guanine groups (telomeres) at their 3’termini. • These form a 4-membered structure or G-tetrads. Upon cell division a number of these guanine groups are lost and typically not replaced. Eventually the number of Guanine groups is reduced to the point that other cell-defence mechanisms destroy the cell (apoptosis) to reduce the risk of mutation of the gene sequence which may lead to disease, including certain cancers.

2. G-Quadruplex Ligands • The natural shortening of telomeres in eukaryotic cells has been implicated in senescence and subsequent apoptosis. • The competing action of telomerase is restricted to certain tumor and early stem cells. • The genetic coding for the telomerase enzyme and the potential inhibition of telomerase expression are considered important areas of research, not merely from the perspective of understanding the genetic dependency but, via a new fundamental maxim, will provide insight into prospective treatments.

3. Telomerase and telomere extension • Tumor cells are the exception to this rule, in that an enzyme called Telomerase is produced and goes about replacing the G-quadruplex structure on the ends of the chromosomes making them theoretically immortal. • A way of stopping the replenishment of the guanine groups would be to formulate a chemical that would adhere to the G-quadruplex in such a way as to prevent this telomeric elongation. • This would cause cancer cells to lose their telomeres as a normal healthy cell does. The fact that cancer cells replicate faster than normal healthy cells (whose telomeres are longer anyway) would serve to selectively diminish the length of telomeres on chromosones in cancerous cells and result in them dying (via apoptosis) faster than healthy cells.

4. Current thinking • Antisense oligonucleotides • Telomerase antagonists • Oligopeptide vaccines • G-Quadruplex Ligands • Braco19 (Antisoma) • Xenograft tumour models clinical trials

6. Biomimetics • One of the strategies would be to design a molecule capable of mimicking the G-quadruplex structure. • High throughput screening using for example DOSY NMR would allow the formation of both static and dynamic combinatorial libraries of small organic species ultimately capable of stabilising the biological equivalent. • Significant research could be carried out in the mode of drug action and the actions of the potential inhibitor within living systems. • The investigation of potential G-quadruplex liganding agents would also involve consideration of physicochemical aspects of both the ligand library and the biological systems affected, inculding thermodynamics and chemical kinetics.

7. Research Calix[4]arenes in host-guest chemistry On the scope and limitations of the Heck reaction of upper rim tetraiodocalix[4]arenes J. Chem. Soc. Perkin Trans. 1, 2001, 24, 3393-3398,Kuhnert N and Le Gresley A

8. Capusle formation and binding to Pesticide 13.1 Å fungicide tetramethyl-thiuram-disulfide Further corroborated by the ESI-MS showing a signal at m/z 2898 Synthesis and capsule formation of upper rim substituted tetra acrylamido calix[4]arenes Organic and Biomolecular Chemistry, 2005, 11, 2175- 2182 N. Kuhnert and A. Le Gresley

9. Dynamic combinatorial libraries using calix[4]arenes • The synthesis of static and dynamic combinatorial libraries using deep cavity tetra-formyl calix[4]arenes N. Kuhnert and A. Le-Gresley, Tetrahedron Lett. 2005,46, 2059-2062.

10. Heck Methodology

11. Reversible Reactions Kuhnert, N and Le-Gresley, A. Synthesis of upper rim calix[4]arene carcerands. Tetrahedron Letters, 98, 1274-1276. 2008

12. Combinatorial Library Le Gresley, A The design and synthesis of deep cavity calix[4]arenes in the development of static and dynamic macrocyclic libraries. European Journal of Organic Chemistry, in press. 2009

13. Anthracene Diacrylamides

14. HETCOR & Activity C5 C2 C1 C4 C6 C3 Manuscript in preparation

15. G-Quadruplex Formation Increase in G-quadruplex formation with time • TTGGGGT forms parallel strand G – quadruplex • Potassium ion stable • Presence of anthracene acrylamide increases G-quadruplex component • DOSY studies underway Zhou, Q.; Lin, L.; Xiang, J.; Sun, H.; Tang, Y.; Fast screening and structural elucidation of G-quadruplex ligands from a mixture via G-quadruplex recognition and NMR methods. Biochimie, 2008, 1-5.

16. Acknowledgements • Prof Nikolai Kuhnert, Jacobs Bremen • Dr Jean-Marie Peron, Kingston • Judith Peters, Surrey • RSC • Invitrogen

17. Compelling • It has been approximately 15 years since telomerase was described as an almost universal marker for human cancer. • Shortened telomeres undergo replicative senescence • TRAP Assay inappropriate for G-Quadruplex ligand activity measurement Paper – De Clan et al. PNAS, 2008 • Grant applications currently pending, • Cancer Research UK • Royal Society

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