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Onconase and amphinase, the antitumor ribonucleases from Rana pipiens oocytes.

ABSTRACT: Rana pipiens oocytes contain two homologues of pancreatic ribonuclease A that are cytostatic and cytotoxic to human cancer cells. Extensively studied Onconase is in advanced Phase IIIb clinical trials against malignant mesothelioma, while Amphinase is a novel enzyme in pre-clinical development. Onconase is the smallest (104 amino acid residues) member of the ribonuclease A superfamily while Amphinase (114 residues) is the largest among amphibian ribonucleases. Both enzymes share the characteristic frog ribonucleases C-terminal disulfide bond but another signature of this group, the N-terminal pyroglutamate, an integral part of Onconase active site is not conserved in Amphinase. Although Onconase and Amphinase are weak catalysts their enzymatic activities are required for cytostatic and cytotoxic activity. While it was postulated that tRNA is the primary substrate of Onconase in vivo there is also extensive indirect evidence that suggests other RNA species, in particular micro RNAs, may actually be the critical target of these ribonucleases. The cytostatic effects of Onconase and Amphinase are manifested as cell arrest in the G(1) cell cycle phase. Apoptosis then follows involving activation of endonucleases(s), caspases, serine proteases and transglutaminase. Onconase was shown to be strongly synergistic when combined with numerous other antitumor modalities. Onconase and Amphinase are highly cationic molecules and their preferential toxicity towards cancer cells (having distinctly higher negative charge compared to normal cells) may depend on increased binding efficiency to the cell surface by electrostatic interactions.

SUBMITTER: Ardelt W

PROVIDER: S-EPMC2586917 | biostudies-literature | 2008 Jun

REPOSITORIES: biostudies-literature

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Onconase and amphinase, the antitumor ribonucleases from Rana pipiens oocytes.

Ardelt W W Shogen K K Darzynkiewicz Z Z

Current pharmaceutical biotechnology 20080601 3

Rana pipiens oocytes contain two homologues of pancreatic ribonuclease A that are cytostatic and cytotoxic to human cancer cells. Extensively studied Onconase is in advanced Phase IIIb clinical trials against malignant mesothelioma, while Amphinase is a novel enzyme in pre-clinical development. Onconase is the smallest (104 amino acid residues) member of the ribonuclease A superfamily while Amphinase (114 residues) is the largest among amphibian ribonucleases. Both enzymes share the characterist ...[more]

PMID: 18673287

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Project description:Abstract: Natural communities of microbes inhabiting amphibian skin, the skin microbiome, are critical to supporting amphibian health and disease resistance. To enable the pro-active health assessment and management of amphibians on Army installations and beyond, we investigated the effects of acute (96h) munitions exposures to Rana pipiens (leopard frog) tadpoles and the associated skin microbiome, integrated with RNAseq-based transcriptomic responses in the tadpole host. Tadpoles were exposed to the legacy munition 2,4,6-trinitrotoluene (TNT), the new insensitive munition (IM) formulation, IMX-101, and the IM constituents nitroguinidine (NQ) and 1-methyl-3-nitroguanidine (MeNQ). The 96h LC50 values and 95% confidence intervals were 2.6 (2.4, 2.8) for ΣTNT and 68.2 (62.9, 73.9) for IMX-101, respectively. The NQ and MeNQ exposures caused no significant impacts on survival in 96h exposures even at maximum exposure levels of 3,560 and 5,285 mg/L, respectively. However, NQ and MeNQ, as well as TNT and IMX-101 exposures, all elicited changes in the tadpole skin microbiome profile, as evidenced by significantly increased relative proportions of the Proteobacteria with increasing exposure concentrations, and significantly decreased alpha-diversity in the NQ exposure. The potential for direct and indirect effects of munitions exposures on the skin microbiome were observed. A direct effect of munitions on microbial flora included the observation of increased relative abundance of the munitions-tolerant, Aeromonadaceae and Pseudomonadaceae, in the NQ exposure. Potential indirect effects on the tadpole skin microbiome resulting from tadpole-host responses to munitions included transcriptional responses indicative of potential changes in skin mucus-layer properties as well as altered production of antimicrobial peptides and innate immune factors. Additional insights into the tadpole host’s transcriptional response to munitions exposures indicated that TNT and IMX-101 exposures each elicited significant enrichment of pathways involved in type-I and type-II xenobiotic metabolism mechanisms where dose-responsive increases in expression were observed. Significant enrichment and increased transcriptional expression of heme and iron binding functions in the TNT exposures was likely connected with known mechanisms of TNT toxicity including hemolytic anemia and methemoglobinemia. The significant enrichment and dose-responsive decrease in transcriptional expression of cell cycle pathways in the IMX-101 exposures was consistent with previous observations in fish, while significant enrichment of immune-related function in response to NQ exposure indicated potential immune suppression at the highest NQ exposure concentration. Finally, the MeNQ exposures elicited significantly decreased transcriptional expression of keratin 16, type I, a gene likely involved in keratinization processes in amphibian skin. Overall, munitions showed the potential to alter tadpole skin microbiome composition and affect transcriptional profiles in the amphibian host, some indicative of potentially impacted host health and immune status, each of which suggest potential implications for munitions exposure on disease susceptibility.

Dataset Information

Onconase and amphinase, the antitumor ribonucleases from Rana pipiens oocytes.

Publications

Onconase and amphinase, the antitumor ribonucleases from Rana pipiens oocytes.

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