Jetze J. Tepe

FR900482 class of anti-tumor drugs cross-links oncoprotein HMG I/Y to DNA in vivo

BACKGROUND Overexpression of the high-mobility group, HMG I/Y, family of chromatin oncoproteins has been implicated as a clinical diagnostic marker for both neoplastic cellular transformation and increased metastatic potential of several human cancers. These minor groove DNA-binding oncoproteins are thus an attractive target for anti-tumor chemotherapy. FR900482 represents a new class of anti-tumor agents that bind to the minor groove of DNA and exhibit greatly reduced host toxicity compared to the structurally related mitomycin C class of anti-tumor drugs. We report covalent cross-linking of DNA to HMG I/Y by FR900482 in vivo which represents the first example of a covalent DNA-drug-protein cross-link with a minor groove-binding oncoprotein and a potential novel mechanism through which these compounds exert their anti-tumor activity. RESULTS Using a modified chromatin immunoprecipitation procedure, fragments of DNA that have been covalently cross-linked by FR900482 to HMG I/Y proteins in vivo were polymerase chain reaction-amplified, isolated and characterized. The nuclear samples from control cells were devoid of DNA fragments whereas the nuclear samples from cells treated with FR900482 contained DNA fragments which were cross-linked by the drug to the minor groove-binding HMG I/Y proteins in vivo. Additional control experiments established that the drug also cross-linked other non-oncogenic minor groove-binding proteins (HMG-1 and HMG-2) but did not cross-link major groove-binding proteins (Elf-1 and NFkappaB) in vivo. Our results are the first demonstration that FR900482 cross-links a number of minor groove-binding proteins in vivo and suggests that the cross-linking of the HMG I/Y oncoproteins may participate in the mode of efficacy as a chemotherapeutic agent. CONCLUSIONS We have illustrated that the FR class of anti-tumor antibiotics, represented in this study by FR900482, is able to produce covalent cross-links between the HMG I/Y oncoproteins and DNA in vivo. The ability of this class of compounds to cross-link the HMG I/Y proteins in the minor groove of DNA represents the first demonstration of drug-induced cross-linking of a specific cancer-related protein to DNA in living cells. We have also demonstrated that FR900482 cross-links other minor groove-binding proteins (HMG-1 and HMG-2 in the present study) in vivo; however, since HMG I/Y is the only minor groove-binding oncoprotein presently known, it is possible that these non-histone chromatin proteins are among the important in vivo targets of this family of drugs. These compounds have already been assessed as representing a compelling clinical replacement for mitomycin C due to their greatly reduced host toxicity and superior DNA interstrand cross-linking efficacy. The capacity of FR900482 to cross-link the HMG I/Y oncoprotein with nuclear DNA in vivo potentially represents a significant elucidation of the anti-tumor efficacy of this family of anticancer agents.

Preparation of hymenialdisine, analogues and their evaluation as kinase inhibitors

The natural product hymenialdisine was first isolated in 1980 from the marine sponges of the genera Hymeniacidon, Acanthella, Axinella and Pseudaxinyssa. The structure was elucidated on the basis of X-ray crystallography demonstrating a structurally interesting pyrrole-azepin-8-one ring system bonded to a glycocyamidine ring. Great interest has been taken in synthesizing this type of scaffold due to its potent activity in competitive kinase inhibition. In addition, several patents have claimed pharmacological use of these compounds for prevention and treatment of different diseases. The challenging syntheses of hymenialdisine and its analogues are described in this review as well as their evaluation as kinase inhibitors.

Trifluoromethanesulfonic acid catalyzed Friedel–Crafts acylation of aromatics with β-lactams

Abstract N-Protected and unprotected 2-azetidinones, protolytically activated by superacidic trifluoromethanesulfonic acid, react with aromatic compounds to give β-amino aromatic ketones in good to excellent yields (65–98%). Non-benzenoid aromatics (pyrrole and ferrocene) produced good yield (64–89%) of the corresponding ketones.

Total Synthesis of the Natural Product (±)-Dibromophakellin and Analogues

(±)-Dibromophakellin has been synthesized in two steps from a known alkene intermediate. The key step in the synthesis is the NBS olefin activation to facilitate the addition of a guanidine molecule across the double bond.

Nuclear Factor-κB Mediated Inhibition of Cytokine Production by Imidazoline Scaffolds

The mammalian nuclear transcription factor NF-kappaB is responsible for the transcription of multiple cytokines, including the pro-inflammatory cytokines tumor necrosis factor alpha (TNF-alpha) and interleukin 6 (IL-6). Elevated levels of pro-inflammatory cytokines play an important role in the pathogenesis of inflammatory disorders such as rheumatoid arthritis (RA). Inhibition of the pro-inflammatory transcription factor NF-kappaB has therefore been identified as a possible therapeutic treatment for RA. We describe herein the synthesis and biological activity of a series of imidazoline-based scaffolds as potent inhibitors of NF-kappaB mediated gene transcription in cell culture as well as inhibitors of TNF-alpha and IL-6 production in interleukin 1 beta (IL-1beta) stimulated human blood.

Structural–activity relationship study of highly-functionalized imidazolines as potent inhibitors of nuclear transcription factor-κB mediated IL-6 production

We herein describe the synthesis and anti-inflammatory properties of a small library of imidazoline-based NF-kappaB inhibitors. The structure-activity relationship of various substituents on an imidazoline core structure was evaluated for the ability to inhibit NF-kappaB mediated IL-6 production. Optimization of the scaffolds was pursued by correlating luciferase-based NF-kappaB reporter assays with inhibition of IL-6 production in IL-1beta stimulated human blood. Several derivatives were found to inhibit NF-kappaB mediated IL-6 production in the nanomolar range in IL-1beta stimulated human blood.

Inhibition of the human proteasome by imidazoline scaffolds

The proteasome has emerged as the primary target for the treatment of multiple myeloma. Unfortunately, nearly all patients develop resistance to competitive-type proteasome inhibitors such as bortezomib. Herein, we describe the optimization of noncompetitive proteasome inhibitors to yield derivatives that exhibit nanomolar potency (compound 49, IC50 130 nM) toward proteasome inhibition and overcome bortezomib resistance. These studies illustrate the feasibility of the development of noncompetitive proteasome inhibitors as additives and/or alternatives to competitive proteasome inhibitors.

Synthesis of 1,2,4-Triazolines and triazoles utilizing oxazolones

We describe herein a convenient method for the synthesis of 1,2,4-triazolines using oxazolones and azodicarboxylates. Subsequent treatment of these 1,2,4-triazolines with NaOH provides efficient access to the corresponding triazoles.

Synthesis of tert-alkyl amino hydroxy carboxylic esters via an intermolecular ene-type reaction of oxazolones and enol ethers.

tert-Alkyl amino hydroxy carboxylic acids are abundantly present within the structure of many biologically active natural products. We describe herein the synthesis of these substrates using an oxazolone-mediated ene-type reaction with enol ethers followed by NaBH4 reduction of the intermediate oxazolone.

Enhancement of Chemotherapeutic Efficacy by Small Molecule Inhibition of NF-κ B and Checkpoint Kinases

Apoptosis or programmed cell death is a cellular mechanism used to regulate cell number and eliminate damaged or mutated cells. Many chemotherapeutic agents and ionizing radiation induce not only apoptotic signaling pathways, but also survival responses such as DNA damage responses and cell cycle arrest, which allow for DNA repair. These survival responses determine the toxicity as well as the efficacy of the cancer treatment. Two main DNA damage responses include the activation of the anti-apoptotic transcription factor NF-kappaB and the activation of cell cycle checkpoint kinases. Strategies of combining chemotherapeutics with (a) inhibitors of NF-kappaB or (b) inhibitors of checkpoint kinases, may therefore enhance the efficacy of current cancer therapies. This review will be focused on recent progress made in combining traditional chemotherapeutic drugs with small molecule inhibitors of NF-kappaB and the checkpoint kinases, Chk1 and Chk2.