Dr. Pommier received his M.D.and Ph.D.degrees from the University of Paris, France, and has been at the National Institutes of Health since 1981. He received an NIH Merit Award for his role in elucidating the function of topoisomerase enzymes as targets for anticancer drugs and Federal Technology Transfer Awards for studies on HIV-1 integrase and DNA topoisomerase inhibitors. Dr. Pommier is a Program Committee Member of the American Association for Cancer Research, and Associate Editor for Cancer Research, Molecular Pharmacology, Leukemia, The Journal of Experimental Therapeutics and Oncology, The International Journal of Oncology, and Drug Resistance Updates. Dr. Pommier holds several patents for inhibitors of DNA topoisomerases I and II and HIV-1 integrase inhibitors.
DNA, Topoisomerases & HIV Integrase Molecular Pharmacology
DNA topoisomerases are essential for all DNA transactions. Topoisomerase I (top1) and topoisomerase II (top2) are targets for the most potent anticancer drugs to date. Top2 inhibitors include the widely used anticancer agents, VP-16 and adriamycin. Camptothecin is a specific top1 inhibitor, and several camptothecin derivatives have recently been introduced in the clinic with promising results in solid tumors including colon and ovarian carcinomas. We study the molecular interactions between drugs, DNA and the enzyme-DNA complexes, and the cellular determinants of cytotoxicity. Evidence has been obtained that topoisomerase inhibitors block the religation of cleavage complexes. Cleavage complexes are enzyme-linked DNA breaks that correspond to topoisomerase catalytic intermediates. Using a camptothecin derivative with an alkylating group and DNA oligonucleotides, we have shown that camptothecins bind at the enzyme-DNA interface. We have sequenced top1 point mutations that render the enzyme resistant to camptothecins. Constructs are being made to further elucidate the structure of the top1-DNA-camptothecin ternary complex. We have recently found that top1-mediated DNA damage can be elicited by commonly occurring endogenous DNA modifications (mismatches, abasic sites, 8-oxoguanine, DNA breaks), as well as by carcinogenic polycyclic aromatic adducts (ethenoadenine, benzo[a]pyrene diol epoxide adducts #Pommier/2000/1#Pommier/2000/2 ). These observations suggest that frequently occurring DNA modifications can lead to the formation of top1 cleavage complexes. We are investigating the mechanisms of damage and repair in several ways: 1/ characterization of the cellular lesions induced by top1 cleavage complexes in cancer cells (replication-mediated DNA double-strand breaks #Strumberg); 2/ elucidation of the cellular responses/pathways elicited in response to such lesions (activation of DNA-PK, RPA phosphorylation #Shao, activation of histone phosphorylation [gamma-H2AX], transcriptional responses); 3/ analysis of the effects of camptothecins in mammalian cells with known genetic defects (Werner syndrome and cells deficient in PARP, beta-polymerase, XRCC1, etc…); and 4/ investigation of the biochemical processing of top1 cleavage complexes in vitro using oligonucleotides and purified repair factors (such as TDP & PNKP). To understand how the genetic make-up of human cells influences their cellular response to anticancer agents and the rationale for the selectivity of topoisomerase inhibitors toward cancer cells, we are studying cell lines from the NCI Anticancer Drug Screen and cell lines with selected gene disruptions.
Ecteinascidin 743 (Et743) is a natural product (from a Caribbean marine tunicate) remarkably active against sarcomas and presently in phase I/II clinical trials. Because of its unique activity profile, we have been interested in elucidating its mechanism of action. We recently demonstrated that Et743 alkylates guanine N2 at selective sites in the DNA minor groove #Pommier/1996. This observation sets Et743 apart from the DNA alkylating agents currently in clinical use. We recently generated Et743-resistant cells, and these cells are deficient in nucleotide excision repair (NER). Thus, Et743 is not just a top1 #Takebayashi and a transcription inhibitor, but its anti-proliferative activity appears NER-dependent. To our knowledge, Et743 is the first drug with such a mechanism of action.
Our laboratory has pioneered the HIV integrase inhibitor research since 1993. The molecular interactions of drugs with retroviral integrases are investigated using recombinant integrases in biochemical assays and by exploring different steps of the integration reaction. The rationale for searching HIV integrase inhibitors #Pommier/2000/3 is that: 1) viruses with mutant integrase cannot replicate, and 2) integrase is one of the three retroviral enzymes (with reverse transcriptase and protease) with no cellular equivalent. Our goals are to discover new antiviral agents, evaluate which steps of the integration reactions are affected by drugs #Wang, and determine the drug binding site in the HIV-1 integrase-DNA complex. Discovery and studies of HIV integrase inhibitors will provide new strategies for anti-AIDS therapy.
Keywords: chemotherapy, DNA damage, DNA repair, cell cycle checkpoints, HIV, DNA binding proteins, pharmacology.
Selected recent publications: