Abstract Mutations in isocitrate dehydrogenase (IDH) identified across cancer types lead to global changes to the epigenome that drive tumorigenesis. Yet, effectiveness of targeted therapies against mutant IDH remains unclear. Here we demonstrate that IDH-mutant glioma and cholangiocarcinoma patient specimens display elevated overall DNA damage responses. With tissue culture and multiple preclinical animal models of glioma and cholangiocarcinoma, we report that the reduced efficiency of DNA damage repair conferred by mutant IDH can be exploited by PARP inhibitors. Moreover, pharmacological effects of PARP inhibitors are dramatically enhanced by introducing concurrent, local ionizing radiation treatment to the animals. Thus, our study characterized the synergy of PARPi and radiation specifically towards IDH-mutant tumors, pointing out that in addition to ongoing trials using PARPi as mono agent, clinical trials that combine PARPi and radiation should be specifically considered. Furthermore, PARPi + RT may represent a readily translatable approach that is selective for tumor cells, transcends histologic origin, and has potential to improve outcomes in multiple diseases.
Recent genomic studies have identified recurrent ATRX mutations in lower grade gliomas (LGGs), especially WHO grade II and III astrocytomas. As a chromatin remodelling protein, ATRX is thought to guard against genomic instability in part by regulating the formation of deleterious secondary structures in DNA known as G-quadruplexs (G4s). In the cell, G4s represent a source of stress for DNA replication by inducing stalled replication forks. In this study, we found by immunostaining in isogenic astrocyte models that ATRX deficiency increased nuclear G4 formation. Moreover, genomic pull-down with a G4-specific antibody showed enrichment in ATRX-deficient astrocytes, which was associated with increased nuclear gamma-H2AX and upregulated ATR pathway signaling. No immediate effects on proliferation, cell cycle progression, or apoptosis were observed, the latter most likely due to coincident TP53 loss in our cell line models. We are currently investigating the precise genomic consequences of increased G4s in the ATRX-deficient setting, particularly with regard to oncogenic copy number alterations that may accumulate over time. We also demonstrated that increased G4s may be therapeutically targetable by G4-stabilizing reagents. One of these compounds, Quarfloxin (CX3543), selectively inhibits cell growth in ATRX-deficient astrocytes at concentrations between 25-300nM. In so doing, Quarfloxin also upregulates DNA damage responses (gamma-H2AX) and apoptotic (Annexin-V) markers in ATRX-deficient astrocytes to a significantly greater extent than in wild type counterparts. Notably, the degree of cell cycle arrest induced by Quarfloxin, did not vary with ATRX status. Accordingly, preferential growth inhibition, induced by Quarfloxin in the ATRX-deficient setting, is likely due to increased apoptosis rather than cell cycle arrest. We are continuing to evaluate the therapeutic potential of Quarfloxin in disease-relevant model systems. Such synthetic lethality represents a promising strategy to effectively target ATRX-deficient tumors.
Abstract Background : Fall dormancy of alfalfa is significantly associated with its cold tolerance, while root, the main body of alfalfa for overwintering, is critical for the cold resistance of alfalfa. The effect of low temperature on mitochondrial ultrastructure and respiratory metabolism of alfalfa seedling root with different fall dormancy was examined, to study the root cold resistance mechanism by which fall dormancy affects alfalfa cold tolerance. Results : Low temperature induced mitochondrial swelling, and the decline of ATP and accumulation of H 2 O 2 in alfalfa seedling root. Both the Cytochrome pathway (CP) and Alternative pathway (AP) respiratory rate were restrained and mETC complex I, II, III and IV activities were inhibited directly by low temperature in both kinds of alfalfa seedling root, while the decline of mETC complex II and III activities were more serious in Gannong No. 5. These results indicated that the damage of mitochondrial structure and the inhibition of mETC complex I , II, III and IV activities directly by low temperature declined the ATP synthesis and aggravated the ROS accumulation, which inhibit the growth of alfalfa seedling root. Moreover, the lower damage on mitochondrial structure and mETC complex II, III activities and higher the percent of AP to total respiratory rate lead to the lower ATP lack and H 2 O 2 accumulation, which contributed to the root growth of Xinmu No.4 seedling. Conclusions : Low sensitivity of mitochondrial structural stability and mETC complex II, III and Alternative respiration to low temperature contributed to the root cold resistance of alfalfa with low fall dormancy grade.
Mutational inactivation of ATRX (α-thalassemia mental retardation X-linked) represents a defining molecular alteration in large subsets of malignant glioma. Yet the pathogenic consequences of ATRX deficiency remain unclear, as do tractable mechanisms for its therapeutic targeting. Here we report that ATRX loss in isogenic glioma model systems induces replication stress and DNA damage by way of G-quadruplex (G4) DNA secondary structure. Moreover, these effects are associated with the acquisition of disease-relevant copy number alterations over time. We then demonstrate, both in vitro and in vivo, that ATRX deficiency selectively enhances DNA damage and cell death following chemical G4 stabilization. Finally, we show that G4 stabilization synergizes with other DNA-damaging therapies, including ionizing radiation, in the ATRX-deficient context. Our findings reveal novel pathogenic mechanisms driven by ATRX deficiency in glioma, while also pointing to tangible strategies for drug development.
Objective Probiotics are beneficial to the intestinal barrier, but few studies have investigated probiotics from giant pandas. This study aims to explore the preventive effects of giant panda-derived Clostridium butyricum on dextran sodium sulfate (DSS)-induced colitis in mice. Methods Clostridium butyricum was administered to mice 14 days before administering DSS treatment to induce enteritis. Results Clostridium butyricum B14 could more effectively prevent colitis in mice than C. butyricum B13. C. butyricum B14 protected the mouse colon by decreasing the histology index and serum interleukin-6 (IL-6) and tumor necrosis factor alpha (TNF-α) levels, which improved intestinal inflammation-related symptoms. In addition, the treatment led to the regulation of the expression of Tifa, Igkv12-89, and Nr1d1 , which in turn inhibited immune pathways. The expression of Muc4 , Lama3, Cldn4, Cldn3 , Ocln , Zo1, Zo2 , and Snai is related the intestinal mucosal barrier. 16S sequencing shows that the C. butyricum B14 significantly increased the abundance of certain intestinal probiotics. Overall, C. butyricum B14 exerted a preventive effect on colitis in mice by inhibiting immune responses, enhancing the intestinal barrier and increasing the abundance of probiotic species. Thus, C. butyricum B14 administration helps regulate the balance of the intestinal microecology. It can suppress immune pathways and enhance barrier-protective proteins.
Mutational inactivation of the SWI/SNF chromatin regulator ATRX occurs frequently in gliomas, the most common primary brain tumors. Whether and how ATRX deficiency promotes oncogenesis by epigenomic dysregulation remains unclear, despite its recent implication in both genomic instability and telomere dysfunction. Here we report that Atrx loss recapitulates characteristic disease phenotypes and molecular features in putative glioma cells of origin, inducing cellular motility although also shifting differentiation state and potential toward an astrocytic rather than neuronal histiogenic profile. Moreover, Atrx deficiency drives widespread shifts in chromatin accessibility, histone composition, and transcription in a distribution almost entirely restricted to genomic sites normally bound by the protein. Finally, direct gene targets of Atrx that mediate specific Atrx-deficient phenotypes in vitro exhibit similarly selective misexpression in ATRX-mutant human gliomas. These findings demonstrate that ATRX deficiency and its epigenomic sequelae are sufficient to induce disease-defining oncogenic phenotypes in appropriate cellular and molecular contexts.
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