Tumor suppressor p53 stole the AKT in hypoxia

Deferoxamine mesylate improves splicing and GAA activity of the common c.-32-13T>G allele in late-onset PD patient fibroblasts

Pompe disease (PD) is an autosomal recessive lysosomal storage disorder due to deficient activity of the acid alpha glucosidase enzyme (GAA). As a consequence of the enzymatic defect, undigested glycogen accumulates within lysosomes. Most patients affected by the late-onset (LO) phenotype carry in at least one allele the c.-32-13T>G variant, which leads to exon 2 exclusion from the pre-mRNA. These patients display a variable and suboptimal response to enzyme replacement therapy. To identify novel therapeutic approaches, we developed a fluorescent GAA exon 2 splicing assay and screened a library of US Food and Drug Administration (FDA)-approved compounds. This led to the identification of several drugs able to restore normal splicing. Among these, we further validated the effects of the iron chelator deferoxamine (Defe) in c.-32-13T>G fibroblasts. Defe treatment resulted in a 2-fold increase of GAA exon 2 inclusion and a 40% increase in enzymatic activity. Preliminary results suggest that this effect is mediated by the regulation of iron availability, at least partially. RNA-seq experiments also showed that Defe might shift the balance of splicing factor levels toward a profile promoting GAA exon 2 inclusion. This work provides the basis for drug repurposing and development of new chemically modified molecules aimed at improving the clinical outcome in LO-PD patients.

Oxygen-releasing manganese clay hybrid complex triggers p53-mediated cancer cell death in hypoxia

Hypoxia in tumor microenvironment is responsible for resistance to conventional modes of cancer therapeutics. A manganese-clay hybrid compound MHC was shown to generate molecular oxygen in aqueous solution. In this study we have shown that MHC, in hypoxia, causes cancer cell death, through release of molecular oxygen and via p53-dependent apoptosis. MHC treatment of cells results in depletion of mitochondrial membrane potential and inhibition of ROS production, in a cell-specific manner. In hypoxia, the oxygen from MHC releases cells from S-phase arrest thus causing p53-dependent apoptosis. The induction of apoptosis by MHC is higher in p53 Wt/Wt cells when it is compared with p53 Mt/Mt cells. The released oxygen from MHC triggers apoptosis via p53 activation through its enhanced homo-oligomerization, post-translational modifications and nuclear localization. Thus MHC as a cellular oxygen-releasing compound has high potential as a drug for hypoxic tumor regression.

Hypoxia-induced release, nuclear translocation, and signaling activity of a DLK1 intracellular fragment in glioma

Glioblastoma multiforme is characterized in part by severe hypoxia associated with tumor necrosis. The cellular response to hypoxia can influence several properties of tumor cells associated with aggressive tumor growth, including metabolic adaptations and tumor cell migration and invasion. Here, we found that Delta Like Non-Canonical Notch Ligand 1 (DLK1) expression was elevated as compared with normal brain in a genetically engineered mouse model of glioma, and that DLK1 expression increased with tumor grade in human glioma samples. DLK1 expression was highest in hypoxic and perivascular tumor areas, and we found that hypoxia induced the release and nuclear translocation of an intracellular fragment of DLK1 in murine glioma as well as in human glioma cultures. Release of the intracellular fragment was dependent on ADAM17 and Hypoxia-inducible Factor 1alpha and 2alpha (HIF-1alpha/HIF-2alpha), as ADAM17 inhibitors and HIF1A/HIF2A siRNA blocked DLK1 cleavage. Expression of a cleavable form of DLK1 amplified several hypoxia-induced traits of glioma cells such as colony formation, stem cell marker gene expression, a PI3K-pathway-mediated metabolic shift, and enhanced invasiveness. Effects of DLK1 were dependent on DLK1-cleavage by ADAM17, as expression of non-cleavable DLK1 could not replicate the DLK1-induced hypoxic phenotype. Finally, forced expression of DLK1 resulted in more invasive tumor growth in a PDGFB-induced glioma mouse model without affecting overall survival. Together, our findings suggest a previously undescribed role for DLK1 as an intracellular signaling molecule.

Alpha lipoic acid attenuates radiation-induced oral mucositis in rats

Purpose

Radiotherapy is currently one of the main treatment modalities for head and neck cancer; however, it also results in severe toxicity to the normal tissue, to the detriment of patients. This study aimed to investigate whether alpha lipoic acid (ALA) could protect against radiation-induced oral mucositis in a rat model.

Results

On post-irradiation days 4 and 7, the epithelial layer on oral mucosa showed pronounced injury (shortening of the layer) and it is diminished by ALA pretreatment before radiation. Hif-1a expression was significantly induced in the radiation group on days 4, 7, and 28. GLUT1 expression was also induced by radiation at all time points, and the expression levels peaked on day 28. Phosphorylated p53 level was significantly higher in the radiation group on days 4 and 7, and Bax protein expression was significantly higher in the same group on day 4 than ALA-pretreated radiation group. TUNEL-positive staining was significantly lower in the ALA-pretreated radiation group.

Materials and methods

Rats were assigned to one of the following four groups: control, ALA only (100 mg/kg, i.p.), irradiated, and ALA administered 24 h and 30 min prior to irradiation, with the neck area including the oral mucosa evenly irradiated with 2 Gy per minute (total dose, 18 Gy) using a photon 6-MV linear accelerator. Rats were sacrificed 4, 7, 28, or 56 days after radiation.

Conclusions

The results show that ALA can be used to ameliorate radiation-induced oral mucositis with head and neck cancer.