Purine anabolism creates therapeutic vulnerability in hepatocellular carcinoma through m 6 A-mediated epitranscriptomic regulation.

BACKGROUND AND AIMS: Purines are building blocks for the cellular genome, and excessive purine nucleotides are seen in tumors. However, how purine metabolism is dysregulated in tumors, and impacting tumorigenesis remains elusive. APPROACH AND RESULTS: Transcriptomic and metabolomic analyses of purine biosynthesis and purine degradation pathways were performed in the tumor and associated nontumor liver tissues obtained from 62 patients with HCC, one of the most lethal cancers worldwide. We found that most genes in purine synthesis are upregulated, while genes in purine degradation are inhibited in HCC tumors. High purine anabolism is associated with unique somatic mutational signatures linked to patient prognosis. Mechanistically, we discover that increasing purine anabolism promotes epitranscriptomic dysregulation of DNA damage repairing (DDR) machinery through upregulating RNA N6-methyladenosine (m 6 A) modification. High purine anabolic HCC is sensitive to DDR-targeting agents but not to standard HCC treatments, correlating with the clinical outcomes in 5 independent HCC cohorts containing 724 patients. We further showed that high purine anabolism determines the sensitivity to DDR-targeting agents in 5 HCC cell lines in vitro and in vivo . CONCLUSIONS: Our results reveal a central role of purine anabolism in regulating DDR, which could be therapeutically exploited in HCC.

Structural elucidation of two novel degradants of lurasidone and their formation mechanisms under free radical-mediated oxidative and photolytic conditions via liquid chromatography-photodiode array/ultraviolet-tandem mass spectrometry and one-dimensional/two-dimensional nuclear magnetic resonance spectroscopy.

Lurasidone is an antipsychotic drug clinically used for the treatment of schizophrenia and bipolar disorder. During a mechanism-based forced degradation study of lurasidone, two novel degradation products were observed under free radical-mediated oxidative (via AIBN) and solution photolytic conditions. The structures of the two novel degradants were identified through an approach combining HPLC, LC-MSn (n = 1, 2), preparative HPLC purification and NMR spectroscopy. The degradant formed under the free radical-mediated condition is an oxidative degradant with half of the piperazine ring cleaved to form two formamides; a mechanism is proposed for the formation of the novel N,N'-diformyl degradant, which should be readily applicable to other drugs that contain a piperazine moiety that is widely present in drug molecules. The degradant observed under the solution photolytic condition is identified as the photo-induced isomer of lurasidone with the benzisothiazole ring altered into a benzothiazole ring.

Directed evolution of adeno-associated virus 5 capsid enables specific liver tropism.

Impressive achievements in clinical trials to treat hemophilia establish a milestone in the development of gene therapy. It highlights the significance of AAV-mediated gene delivery to liver. AAV5 is a unique serotype featured by low neutralizing antibody prevalence. Nevertheless, its liver infectivity is relatively weak. Consequently, it is vital to exploit novel AAV5 capsid mutants with robust liver tropism. To this aim, we performed AAV5-NNK library and barcode screening in mice, from which we identified one capsid variant, called AAVzk2. AAVzk2 displayed a similar yield but divergent post-translational modification sites compared with wild-type serotypes. Mice intravenously injected with AAVzk2 demonstrated a stronger liver transduction than AAV5, roughly comparable with AAV8 and AAV9, with undetectable transduction of other tissues or organs such as heart, lung, spleen, kidney, brain, and skeletal muscle, indicating a liver-specific tropism. Further studies showed a superior human hepatocellular transduction of AAVzk2 to AAV5, AAV8 and AAV9, whereas the seroreactivity of AAVzk2 was as low as AAV5. Overall, we provide a novel AAV serotype that facilitates a robust and specific liver gene delivery to a large population, especially those unable to be treated by AAV8 and AAV9.