Purpose: In the current study, we examined the in vivo effects of AZD1152, a novel and specific inhibitor of Aurora kinase activity (with selectivity for Aurora B). Experimental Design: The pharmacodynamic effects and efficacy of AZD1152 were determined in a panel of human tumor xenograft models. AZD1152 was dosed via several parenteral (s.c. osmotic mini-pump, i.p., and i.v.) routes. Results: AZD1152 potently inhibited the growth of human colon, lung, and hematologic tumor xenografts (mean tumor growth inhibition range, 55% to z100%; P < 0.05) in immunodeficient mice. Detailed pharmacodynamic analysis in colorectal SW620 tumor-bearing athymic rats treated i.v. with AZD1152 revealed a temporal sequence of phenotypic events in tumors: transient suppression of histone H3 phosphorylation followed by accumulation of 4N DNA in cells (2.4-fold higher compared with controls) and then an increased proportion of polyploid cells (>4N DNA, 2.3-fold higher compared with controls). Histologic analysis showed aberrant cell division that was concurrent with an increase in apoptosis in AZD1152-treated tumors. Bone marrow analyses revealed transient myelosuppression with the drug that was fully reversible following cessation of AZD1152 treatment. Conclusions: These data suggest that selective targeting of Aurora B kinase may be a promising therapeutic approach for the treatment of a range of malignancies. In addition to the suppression of histone H3 phosphorylation, determination of tumor cell polyploidy and apoptosis may be useful biomarkers for this class of therapeutic agent. AZD1152 is currently in phase I trials.
Cellular transforming genes can be detected in human tumours by DNA-mediated transfection into NIH 3T3 mouse fibroblasts. The activated transforming genes have been, in most cases, members of the ras gene family, of which the most frequently found is the c-Ki-ras oncogene and least frequently the c-Ha-ras gene. An increasing number of studies has identified the presence of activated N-ras (which has no known viral homologue) in human tumour cell lines. Furthermore, other transforming genes, distinct from the ras gene family, have been reported in B-and T-cell lymphomas. The activation of c-Ha-ras and N-ras has been described in some cell lines derived from cases of human malignant melanoma. Here we describe the presence of transforming activity in the DNA from a human melanoma cell line which shows weak homology with members of the ras oncogene family.
The presence of activated transforming genes was investigated in four primary aflatoxin-induced rat liver tumors in male Fischer rats, in two cell lines generated from such tumors, in an epithelial liver-derived nontransformed cell line, and in the latter cell line after transformation by aflatoxin B1 in vitro. When DNA extracted from these sources was transfected into NIH 3T3 cells, negative results were obtained from focus assays. Cotransfection of these DNA samples with a gene for resistance to G418, followed by selection for resistance to that antibiotic, and tumorigenicity testing in nude mice demonstrated DNA-mediated transfer of the neoplastic phenotype in all cases except for DNA from the nontransformed cell line. DNA extracted from these primary nude mouse tumors used in a secondary round of transfection with NIH 3T3 cells gave positive results in focus assays, which were conserved through succeeding rounds of transfection. By use of appropriate radiolabeled probes, activated ras oncogenes were detected in all samples. N-ras activation was detected in three of the primary rat liver tumors and both hepatoma cell lines. Ki-ras activation was detected in one primary rat liver tumor, and Ha-ras activation was detected in the cell line transformed in vitro with activated aflatoxin B1. The activated Ki-ras oncogene was further characterized by use of synthetic oligonucleotide probes and was shown to contain a G -* A transition at the second nucleotide in codon 12.There is strong epidemiological evidence for involvement of aflatoxins in the high incidence of hepatoma in certain third world areas (1), especially in synergism with hepatitis B virus (2) and alcohol (3). Within the same country, highly significant correlations with aflatoxin ingestion have been obtained for incidences of primary hepatoma in different areas (1, 4). Aflatoxin B1 (AFB,)-induced rat liver cancer has been extensively studied to gain insight into the mode of toxin action and the process of neoplastic induction (5). AFB1 is metabolized into its active form, AFB1-8,9-epoxide (6), which forms bulky adducts with DNA. In vivo, binding of AFB1 appears to be exclusively to guanine residues (7). On a molar basis, activated AFB1 is one of the most potent mutagens (8) so far studied, a property that correlates well with carcinogenicity (9). In foodstuffs naturally contaminated with aflatoxins (as in the peanut meal used in the present study) smaller amounts of aflatoxin G1 (AFG1) are frequently found, but the predominant aflatoxin present is AFB1. AFG, is hepatocarcinogenic in the rat but is less potent than AFB1 (10). The mechanism of activation of AFG1 and its binding to guanine bases in the DNA are similar to that of AFB1 (11).Activation of cellular oncogenes has been shown in many human and experimental tumors. Although 10-15% of all human tumors show activated oncogenes, mainly ras genes (12), some well-defined and controlled experimental carcinogenesis systems show a higher incidence of detectable transforming genes (13-18). In this...
DNA isolated from cell line Mel Swift, a human melanoma cell line, transforms NIH3T3 cells. Southern blot analysis of DNA from secondary foci revealed conserved 8.8- and 7.8-kilobase EcoRI fragments which hybridized with a human repetitive sequence clone, blur 8. The activated transforming gene was identified as N-ras, and the 8.8-kilobase EcoRI fragment from a secondary transformant was cloned. Synthetic 17-mer oligonucleotides which spanned either the normal codon 61 (CAA) or a mutant codon 61 (AAA) were used for hybridization. Cloned N-ras from melanoma cell line Mel Swift hybridized to the mutant (AAA) oligonucleotide. From this we predicted a glutamine-to-lysine substitution in amino acid 61, a change confirmed by conventional sequencing of the first and second exons of N-ras from cell line Mel Swift. Transfection experiments showed that only those recombinant clones with the mutation in position 61 were biologically active.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.