Gossypol and an HMT G9a inhibitor act in synergy to induce cell death in pancreatic cancer cells

The histone methyltransferase G9a is overexpressed in a variety of cancer types, including pancreatic adenocarcinoma, and promotes tumor invasiveness and metastasis. We recently reported the discovery of BRD4770, a small-molecule inhibitor of G9a that induces senescence in PANC-1 cells. We observed that the cytotoxic effects of BRD4770 were dependent on genetic background, with cell lines lacking functional p53 being relatively resistant to compound treatment. To understand the mechanism of genetic selectivity, we used two complementary screening approaches to identify enhancers of BRD4770. The natural product and putative BH3 mimetic gossypol enhanced the cytotoxicity of BRD4770 in a synergistic manner in p53-mutant PANC-1 cells but not in immortalized non-tumorigenic pancreatic cells. The combination of gossypol and BRD4770 increased LC3-II levels and the autophagosome number in PANC-1 cells, and the compound combination appears to act in a BNIP3 (B-cell lymphoma 2 19-kDa interacting protein)-dependent manner, suggesting that these compounds act together to induce autophagy-related cell death in pancreatic cancer cells.     

Tryptase Promotes Atherosclerotic Plaque Haemorrhage in ApoE-/- Mice

Tryptase, the most abundant mast cell (MC) granule protein, plays an important role in atherosclerosis plaque development. To test the hypothesis that tryptase participates directly in atherosclerosis plaque haemorrhage, the gene sequence and siRNA for tryptase were cloned into a lentivirus carrier and atherosclerosis plaque haemorrhage models in ApoE-/- mice were constructed. After a cuffing-cervical artery operation, the mice were randomly divided into 6 groups. Hematoxylin and eosin(HE) staining showed that the cervical artery plaque area was much larger in the tryptase overexpression group compared to the other groups, and there was greater artery stenosis. The artery stenosis from the cuff-side in all groups was more than 90%, except the siRNA group. Tryptase promotes plaque haemorrhage distinctively because 50% of the mice in the tryptase overexpression group had plaque haemorrhage, while only 10% in the siRNA group did. The immunohistochemistry of the cervical artery plaque showed that plasminogen activator inhibitor-1 (PAI-1) expression was the lowest while tissue plasminogen activator (tPA), CD31, CD34 and VEGF was the highest in the tryptase overexpression groups. This observation was completely contrary to what was observed in the siRNA group. Tryptase promoted bEnd.3 cell growth, migration and capillary-like tube formation, which suggests that tryptase can promote microvessel angiogenesis. PAI-1 expression was inhibited, while tPA expression was increased by tryptase in bEnd.3 cells. Our in vivo and in vitro studies suggest that trypase can promote atherosclerotic plaque haemorrhage by promoting angiogenesis and regulating the balance of PAI-1 and tPA. Thus, regulating tryptase expression in MCs may provide a potential target for atherosclerosis treatment.     

Inducible Arginase 1 Deficiency in Mice Leads to Hyperargininemia and Altered Amino Acid Metabolism

Arginase deficiency is a rare autosomal recessive disorder resulting from a loss of the liver arginase isoform, arginase 1 (ARG1), which is the final step in the urea cycle for detoxifying ammonia. ARG1 deficiency leads to hyperargininemia, characterized by progressive neurological impairment, persistent growth retardation and infrequent episodes of hyperammonemia. Using the Cre/loxP-directed conditional gene knockout system, we generated an inducible Arg1-deficient mouse model by crossing “floxed” Arg1 mice with CreER^T2 mice. The resulting mice (Arg-Cre) die about two weeks after tamoxifen administration regardless of the starting age of inducing the knockout. These treated mice were nearly devoid of Arg1 mRNA, protein and liver arginase activity, and exhibited symptoms of hyperammonemia. Plasma amino acid analysis revealed pronounced hyperargininemia and significant alterations in amino acid and guanidino compound metabolism, including increased citrulline and guanidinoacetic acid. Despite no alteration in ornithine levels, concentrations of other amino acids such as proline and the branched-chain amino acids were reduced. In summary, we have generated and characterized an inducible Arg1-deficient mouse model exhibiting several pathologic manifestations of hyperargininemia. This model should prove useful for exploring potential treatment options of ARG1 deficiency.     

In Vivo Validation of Simultaneous Non-Contrast Angiography and intraPlaque Hemorrhage (SNAP) Magnetic Resonance Angiography: An Intracranial Artery Study

Objectives

Simultaneous Non-contrast Angiography and intraPlaque hemorrhage (SNAP) technique was recently proposed for joint MRA and intraplaque hemorrhage (IPH) imaging. The purpose of this study is to validate SNAP’s MRA performance in patients with suspected intracranial artery disease.

Methods

SNAP and time-of-flight (TOF) techniques with matched field of view and resolution were applied on 15 patients with suspected intracranial artery disease. Both techniques were evaluated based on their detection of luminal stenosis of bilateral middle cerebral arteries (MCA) and the delineation of smallest visible branches (SVB) of the MCA. Statistical analysis was conducted on the artery level.

Results

The SNAP MRA was found to provide similar stenosis detection performance when compared with TOF (Cohen’s κ 0.79; 95% Confidence Interval: 0.56–0.99). For the SVB comparison, SNAP was found to provide significantly better small artery delineation than TOF (p = 0.017). Inter-reader reproducibility for both measurements on SNAP was over 0.7. SNAP also detected IPH lesions on 13% of the patients.

Conclusions

The SNAP technique’s MRA performance was optimized and compared against TOF for intracranial artery atherosclerosis imaging and was found to provide comparable stenosis detection accuracy. Along with its IPH detection capability, SNAP holds the potential to become a first-line screening tool for high risk intracranial atherosclerosis disease evaluation.