@article {Barnes790, author = {Betsy J. Barnes and Robert A. Izydore and Ann E. Eakin and Iris H. Hall}, title = {Induction of Tmolt4 Leukemia Cell Death by 3,3-Disubstituted-6,6-pentamethylene-1,5-diazabicyclo[3.1.0]hexane-2,4-diones: Specificity for Type II Inosine 5'-Monophosphate Dehydrogenase}, volume = {298}, number = {2}, pages = {790--796}, year = {2001}, publisher = {American Society for Pharmacology and Experimental Therapeutics}, abstract = {Inosine 5'-monophosphate dehydrogenase (IMPDH), the rate-limiting enzyme in the de novo pathway for synthesis of guanine nucleotides, is essential for normal cell proliferation and function. New derivatives of the 1,5-diazabicyclo[3.1.0]hexane-2,4-diones were synthesized and examined for antiproliferative effects and selective inhibition of human IMPDH type II activity. The 3,3-disubstituted-6,6-pentamethylene-1,5-diazabicyclo[3.1.0]hexane-2,4-diones proved to be effective antiproliferative agents in tumor cell lines derived from murine and human leukemias, lymphomas, uterine carcinoma, glioma, and breast effusion with ED50 values (concentration of compound that inhibits 50\% of cell growth) ranging from 3.3 to 16 μM. The agents acted as antimetabolites suppressing de novo purine biosynthesis at the key regulatory enzyme IMPDH, resulting in the specific suppression of dGTP pool levels by 19 to 64\% and DNA synthesis by 39 to 68\%. The derivatives were specific inhibitors of IMPDH type II activity as opposed to type I, acting in a competitive manner with respect to inosine 5'-monophosphate,Ki values of 44.2 to 62 μM. In addition, effects of agents on Tmolt4 cell growth and DNA synthesis could be reversed by coincubation with guanosine. Unlike mycophenolic acid and tiazofurin, the 6,6-pentamethylene-1,5-diazabicyclo[3.1.0]hexane-2,4-diones specifically targeted type II IMPDH, where activity is increased in replicating or neoplastic cells, and did not suppress type I activity, where expression is relatively unaffected by cell proliferation or transformation. Agents were not inhibitors of normal human lung fibroblast cell growth, WI-38, most likely due to the observed isoform selectivity. The American Society for Pharmacology and Experimental Therapeutics}, issn = {0022-3565}, URL = {https://jpet.aspetjournals.org/content/298/2/790}, eprint = {https://jpet.aspetjournals.org/content/298/2/790.full.pdf}, journal = {Journal of Pharmacology and Experimental Therapeutics} }