Targeting ALK in pediatric RMS does not induce antitumor activity in vivo.

Purpose: The anaplastic lymphoma kinase (ALK) has been demonstrated to be a valid clinical target in diseases such as anaplastic large cell lymphoma and non-small cell lung cancer. Recent studies have indicated that ALK is overexpressed in pediatric rhabdomyosarcoma (RMS) and hence we hypothesized that this kinase may be a suitable candidate for therapeutic intervention in this tumor.

Methods: We evaluated the expression of ALK in a panel of pediatric RMS cell lines and patient-derived xenografts (PDX), and sensitivity to ALK inhibitors was assessed both in vitro and in vivo.

Tumour-selective targeting of drug metabolizing enzymes to treat metastatic cancer.

Carboxylesterases (CEs) are ubiquitous enzymes responsible for the detoxification of ester-containing xenobiotics. This hydrolysis reaction results in the formation of the corresponding carboxylic acid and alcohol. Due to their highly plastic active site, CEs can hydrolyze structurally very distinct and complex molecules.

Targeting oxidative stress in embryonal rhabdomyosarcoma.

Rhabdomyosarcoma is a soft-tissue sarcoma with molecular and cellular features of developing skeletal muscle. Rhabdomyosarcoma has two major histologic subtypes, embryonal and alveolar, each with distinct clinical, molecular, and genetic features. Genomic analysis shows that embryonal tumors have more structural and copy number variations than alveolar tumors.

Global and local molecular dynamics of a bacterial carboxylesterase provide insight into its catalytic mechanism.

Carboxylesterases (CEs) are ubiquitous enzymes responsible for the detoxification of xenobiotics. In humans, substrates for these enzymes are far-ranging, and include the street drug heroin and the anticancer agent irinotecan. Hence, their ability to bind and metabolize substrates is of broad interest to biomedical science.

Human carboxylesterase 1 stereoselectively binds the nerve agent cyclosarin and spontaneously hydrolyzes the nerve agent sarin.

Organophosphorus (OP) nerve agents are potent toxins that inhibit cholinesterases and produce a rapid and lethal cholinergic crisis. Development of protein-based therapeutics is being pursued with the goal of preventing nerve agent toxicity and protecting against the long-term side effects of these agents. The drug-metabolizing enzyme human carboxylesterase 1 (hCE1) is a candidate protein-based therapeutic because of its similarity in structure and function to the cholinesterase targets of nerve agent poisoning.

Modifications of human carboxylesterase for improved prodrug activation.

Background: Carboxylesterases (CEs) are ubiquitous enzymes responsible for the hydrolysis of numerous clinically useful drugs. As ester moieties are frequently included in molecules to improve their water solubility and bioavailability, de facto they become substrates for CEs.

Objective: In this review, we describe the properties of human CEs with regard to their ability to activate anticancer prodrugs and demonstrate how structure-based design can be used to modulate substrate specificity and to increase efficiency of hydrolysis.

Evaluation of the 'side door' in carboxylesterase-mediated catalysis and inhibition.

Abstract Structures of mammalian carboxylesterases (CEs) reveal the presence of a 'side door' that is proposed to act as an alternative pore for the trafficking of substrates and products. p-Nitrobenzyl esterase (pnb CE) from Bacillus subtilis exhibits close structural homology and a similar side-door domain as mammalian CEs. We investigated the role of a specific 'gate' residue at the side door (i.

Analysis of the inhibition of mammalian carboxylesterases by novel fluorobenzoins and fluorobenzils.

We have synthesized and assessed the ability of symmetrical fluorobenzoins and fluorobenzils to inhibit mammalian carboxylesterases (CE). The majority of the latter were excellent inhibitors of CEs however unexpectedly, the fluorobenzoins were very good enzyme inhibitors. Positive correlations were seen with the charge on the hydroxyl carbon atom, the carbonyl oxygen, and the Hammett constants for the derived K(i) values with the fluorobenzoins.

Selective inhibition of carboxylesterases by isatins, indole-2,3-diones.

Carboxylesterases (CE) are ubiquitous enzymes thought to be responsible for the metabolism and detoxification of xenobiotics. Numerous clinically used drugs including Demerol, lidocaine, capecitabine, and CPT-11 are hydrolyzed by these enzymes. Hence, the identification and application of selective CE inhibitors may prove useful in modulating the metabolism of esterified drugs in vivo.

Tumor-targeted enzyme/prodrug therapy mediates long-term disease-free survival of mice bearing disseminated neuroblastoma.

Neural stem cells and progenitor cells migrate selectively to tumor loci in vivo. We exploited the tumor-tropic properties of HB1.F3.

Intracellular inhibition of carboxylesterases by benzil: modulation of CPT-11 cytotoxicity.

Carboxylesterases are ubiquitous proteins responsible for the detoxification of xenobiotics. However, these enzymes also activate prodrugs, such as the anticancer agents capecitabine and CPT-11. As a consequence, overexpression of carboxylesterases within tumor cells sensitizes these cells to CPT-11.

Inhibition of carboxylesterases by benzil (diphenylethane-1,2-dione) and heterocyclic analogues is dependent upon the aromaticity of the ring and the flexibility of the dione moiety.

Benzil has been identified as a potent selective inhibitor of carboxylesterases (CEs). Essential components of the molecule required for inhibitory activity include the dione moiety and the benzene rings, and substitution within the rings affords increased selectivity toward CEs from different species. Replacement of the benzene rings with heterocyclic substituents increased the K(i) values for the compounds toward three mammalian CEs when using o-nitrophenyl acetate as a substrate.

Update on gene therapy approaches for cancer.

The goal of cancer gene therapy is the selective and efficient eradication of tumor cells without significant systemic toxicity. Although several different gene therapy approaches have been developed and tested both in preclinical and clinical trials, none of these methods are suitable for the safe and efficient treatment of cancer. Recent advances in tumor cell biology have accelerated the identification of novel proteins as targets for gene transfer strategies.

Identification and characterization of novel benzil (diphenylethane-1,2-dione) analogues as inhibitors of mammalian carboxylesterases.

Carboxylesterases (CE) are ubiquitous enzymes responsible for the metabolism of xenobiotics. Because the structural and amino acid homology among esterases of different classes, the identification of selective inhibitors of these proteins has proved problematic. Using Telik's target-related affinity profiling (TRAP) technology, we have identified a class of compounds based on benzil (1,2-diphenylethane-1,2-dione) that are potent CE inhibitors, with K(i) values in the low nanomolar range.

Molecular modeling of CPT-11 metabolism by carboxylesterases (CEs): use of pnb CE as a model.

CPT-11 is a prodrug that is converted in vivo to the topoisomerase I poison SN-38 by carboxylesterases (CEs). Among the CEs studied thus far, a rabbit liver CE (rCE) converts CPT-11 to SN-38 most efficiently. Despite extensive sequence homology, however, the human homologues of this protein, hCE1 and hiCE, metabolize CPT-11 with significantly lower efficiencies.

Carboxylesterase-mediated sensitization of human tumor cells to CPT-11 cannot override ABCG2-mediated drug resistance.

The recently introduced camptothecin-derived chemotherapeutic agents have demonstrated remarkable promise in cancer therapy and as such have been approved for use in humans for the treatment of ovarian, lung, and colon cancer. CPT-11 is a prodrug that is activated by esterases to yield the potent topoisomerase I inhibitor, SN-38. Considerable success has been achieved in the treatment of both naïve and drug-resistant colon cancer with CPT-11.

p53-mediated regulation of expression of a rabbit liver carboxylesterase confers sensitivity to 7-ethyl-10-[4-(1-piperidino)-1-piperidino]carbonyloxycamptothecin (CPT-11).

We have exploited the ability of wild-type (wt) p53 to repress gene expression and produce tumor-selective cytotoxicity using viral-directed enzyme prodrug therapy. Vectors containing either the cytomegalovirus or Rous sarcoma virus promoter regulating transcription of a rabbit liver carboxylesterase (CE) have been constructed. Upon transfection of these plasmids into cells expressing either wt or mutant p53, differential expression of the CE has been observed, resulting in sensitization of the cells expressing the latter protein to the anticancer prodrug irinotecan, 7-ethyl-10-[4-(1-piperidino)-1-piperidino] carb- onyloxycamptothecin (CPT-11).