High expression of ABCG2 induced by EZH2 disruption has pivotal roles in MDS pathogenesis

Both proto-oncogenic and tumor-suppressive functions have been reported for enhancer of zeste homolog 2 (EZH2). To investigate the effects of its inactivation, a mutant EZH2 lacking its catalytic domain was prepared (EZH2-dSET). In a mouse bone marrow transplant model, EZH2-dSET expression in bone marrow cells induced a myelodysplastic syndrome (MDS)-like disease in transplanted mice. Analysis of these mice identified Abcg2 as a direct target of EZH2. Intriguingly, Abcg2 expression alone induced the same disease in the transplanted mice, where stemness genes were enriched. Interestingly, ABCG2 expression is specifically high in MDS patients. The present results indicate that ABCG2 de-repression induced by EZH2 mutations have crucial roles in MDS pathogenesis.

SETBP1 mutations drive leukemic transformation in ASXL1-mutated MDS

Mutations in ASXL1 are frequent in patients with myelodysplastic syndrome (MDS) and associated with adverse survival yet the molecular pathogenesis of ASXL1 mutations are not fully understood. Recently it has been found that deletion of Asxl1 or expression of C-terminal-truncating ASXL1 mutations (ASXL1-MT) inhibit myeloid differentiation and induce MDS-like disease in mice. Here, we find that SETBP1 mutations (SETBP1-MT) are enriched among patients with ASXL1-mutated MDS patients and associated with increased incidence of leukemic transformation as well as shorter survival, suggesting SETBP1-MT play a critical role in leukemic transformation of MDS. We identify that SETBP1-MT inhibit ubiquitination and subsequent degradation of SETBP1, resulting in increased expression. Expression of SETBP1-MT, in turn, inhibited Pp2a activity, leading to Akt activation and enhanced expression of posterior Hoxa genes in ASXL1 mutant cells. Biologically, SETBP1-MT augmented ASXL1-MT-induced differentiation block, inhibited apoptosis, and enhanced myeloid colony output. SETBP1-MT collaborated with ASXL1-MT in inducing AML in vivo. The combination of ASXL1-MT and SETBP1-MT activated a stem cell signature and repressed the TGF-β signaling pathway, in contrast to the ASXL1-MT-induced MDS model. These data reveal that SETBP1-MT are critical drivers of ASXL1-mutated MDS and identify several deregulated pathways as potential therapeutic targets in high-risk MDS.

Erythromycin ameliorates renal injury via anti-inflammatory effects in experimental diabetic rats

AIMS/HYPOTHESIS

Recent studies have shown that the inflammatory process is involved in the pathogenesis of diabetic nephropathy. Fourteen-membered ring macrolides, including erythromycin, have anti-inflammatory, as well as antibacterial effects. The aim of this study was to investigate the renoprotective effects of erythromycin in streptozotocin (STZ)-induced diabetic rats.

METHODS

STZ-induced diabetic rats were treated orally with erythromycin (5 mg/kg body weight) or vehicle every day for 8 weeks. To evaluate the effect of erythromycin treatment, we measured urinary albumin excretion, and examined the following in the kidney: histological changes, the expression of intercellular adhesion molecule-1 (ICAM-1), macrophage infiltration, and nuclear factor-kappa B (NF-kappaB) activity.

RESULTS

Erythromycin significantly reduced urinary albumin excretion without affecting blood glucose levels and blood pressure. Erythromycin also attenuated glomerular hypertrophy, mesangial expansion, macrophage infiltration and ICAM-1 expression in renal tissues. The expression of the gene encoding TGFB1 (also known as TGF-beta1), type IV collagen protein production and NF-kappaB activity in renal tissues were increased in diabetic rats and reduced by erythromycin treatment.

CONCLUSIONS/INTERPRETATION

Erythromycin prevented renal injuries without changes of blood glucose levels and blood pressure in experimental diabetic rats. These results suggest that the renoprotective effects of erythromycin are based on its anti-inflammatory effect via suppression of NF-kappaB activation. Modulation of microinflammation with erythromycin may provide a new approach for diabetic nephropathy.

Connection mechanism of physical-contact optical fiber connectors with spherical convex polished ends

We present an experimental and analytical investigation of the connection mechanism of physical-contact optical-fiber connectors with spherical convex polished ends and confirm that reducing the curvature radius of the spherical convex ferrule end face is effective for establishing a stable connection with slight axial compressive force on the ferrules.