AbstractΔ24-RGD is an infectivity-augmented, conditionally replicative oncolytic adenovirus with significant antiglioma effects. Although intratumoral delivery of Δ24-RGD may be effective, intravascular delivery would improve successful application in humans. Due to their tumor tropic properties, we hypothesized that human mesenchymal stem cells (hMSC) could be harnessed as intravascular delivery vehicles of Δ24-RGD to human gliomas. To assess cellular events, green fluorescent protein-labeled hMSCs carrying Δ24-RGD (hMSC-Δ24) were injected into the carotid artery of mice harboring orthotopic U87MG or U251-V121 xenografts and brain sections were analyzed by immunofluorescence for green fluorescent protein and viral proteins (E1A and hexon) at increasing times. hMSC-Δ24 selectively localized to glioma xenografts and released Δ24-RGD, which subsequently infected glioma cells. To determine efficacy, mice were implanted with luciferaselabeled glioma xenografts, treated with hMSC-Δ24 or controls, and imaged weekly by bioluminescence imaging. Analysis of tumor size by bioluminescence imaging showed inhibition of glioma growth and eradication of tumors in hMSC-Δ24-treated animals compared with controls (P < 0.0001). There was an increase in median survival from 42 days in controls to 75.5 days in hMSC-Δ24-treated animals (P < 0.0001) and an increase in survival beyond 80 days from 0% to 37.5%, respectively. We conclude that intra-arterially delivered hMSC-Δ24 selectively localize to human gliomas and are capable of delivering and releasing Δ24-RGD into the tumor, resulting in improved survival and tumor eradication in subsets of mice.
The discovery of N
6
-methyldeoxyadenine (6mA) across eukaryotes led to a search for additional epigenetic mechanisms. However, some studies have highlighted confounding factors that challenge the prevalence of 6mA in eukaryotes. We developed a metagenomic method to quantitatively deconvolve 6mA events from a genomic DNA sample into species of interest, genomic regions, and sources of contamination. Applying this method, we observed high-resolution 6mA deposition in two protozoa. We found that commensal or soil bacteria explained the vast majority of 6mA in insect and plant samples. We found no evidence of high abundance of 6mA in
Drosophila
,
Arabidopsis
, or humans. Plasmids used for genetic manipulation, even those from Dam methyltransferase mutant
Escherichia coli
, could carry abundant 6mA, confounding the evaluation of candidate 6mA methyltransferases and demethylases. On the basis of this work, we advocate for a reassessment of 6mA in eukaryotes.
Metabolic changes induced by oncogenic drivers of cancer contribute to tumor growth and are attractive targets for cancer treatment. Here, we found that increased growth of PTEN mutant cells was dependent on glutamine flux through the de novo pyrimidine synthesis pathway, which created sensitivity to inhibition of dihydroorotate dehydrogenase, a rate limiting enzyme for pyrimidine ring synthesis. S-phase PTEN mutant cells showed increased numbers of replication forks, and inhibitors of dihydroorotate dehydrogenase led to chromosome breaks and cell death due to inadequate ATR activation and DNA damage at replication forks. Our findings indicate that enhanced glutamine flux generates vulnerability to dihydroorotate dehydrogenase inhibition, which then causes synthetic lethality in PTEN deficient cells due to inherent defects in ATR activation. Inhibition of dihydroorotate dehydrogenase could thus be a promising therapy for patients with PTEN mutant cancers.
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