Cytarabine (Ara-C) is the first-line drug for the treatment of acute myelogenous leukemia (AML). However, resistance eventually develops, decreasing the efficacy of Ara-C in AML patients. The expression of SAMHD1, a deoxynucleoside triphosphate (dNTP) triphosphohydrolase, has been reported to be elevated in Ara-C-resistant AML patients and to play a crucial role in mediating Ara-C resistance in AML. However, the mechanism by which SAMHD1 is upregulated in resistant AML remains unknown. In this study, NONO interacted with and stabilized SAMHD1 by inhibiting DCAF1-mediated ubiquitination/degradation of SAMHD1. Overexpression of NONO increased SAMHD1 expression and reduced the sensitivity of AML cells to Ara-C, and downregulation of NONO had the opposite effects. In addition, the DNA-damaging agents DDP and adriamycin (ADM) reduced NONO/SAMHD1 expression and sensitized AML cells to Ara-C. More importantly, NONO was upregulated in Ara-C-resistant AML cells, resulting in increased SAMHD1 expression in resistant AML cells, and DDP and ADM treatment resensitized resistant AML cells to Ara-C. This study revealed the mechanism by which SAMHD1 is upregulated in Ara-C-resistant AML cells and provided novel therapeutic strategies for Ara-C-resistant AML.

In this study, a simple and sensitive LC-MS/MS method was developed and validated for simultaneous determination of icotinib and its four circulating metabolites in human plasma. The analytes were extracted with acetonitrile and separated on a C column using 2 mm ammonium acetate containing 0.2% formic acid and acetonitrile as mobile phase. The analytes were introduced into the mass spectrometer via an electrospray ionization source operated in positive ion mode. Precursor-to-product transitions were optimized to be m/z 392.2 → 304.1 for icotinib, m/z 424.1 → 278.2 for M1 and M2, m/z 408.2 → 320.1 for M3, m/z 410.2 → 322.1 for M4 and m/z 394.4 → 278.1 for IS. The assay showed good linearity over the concentration ranges of 0.1-600 ng/mL for icotinib and 0.1-200 ng/mL for metabolites, with correlation coefficients >0.994 (r > 0.994). The LLOQ was 0.1 ng/mL for each analyte. The intra- and inter-day precisions (RSD) were ≤12.98% while the accuracy (RE) ranged from -8.76 to 12.01%. No significant matrix effect was observed. The validated method was successfully applied for the pharmacokinetic study of icotinib and its four circulating metabolites in human plasma after oral administration of icotinib at a single dose of 125 mg.

Acute myeloid leukemia (AML) is a highly heterogeneous hematopoietic malignant tumor, accompanied by the abnormal cloning of myeloid hematopoietic stem cells, little is known about its etiological role and pathogenesis. We aimed to explore the effect and regulatory mechanism of LINC00504 on the malignant phenotypes of AML cells. In this study, LINC00504 levels in AML tissues or cells were ascertained by PCR. RNA pull-down and RIP assays were conduct to verify the combination of LINC00504 and MDM2. Cell proliferation was detected by CCK-8 and BrdU assays, apoptosis was checked by flow cytometry, and glycolytic metabolism levels were detected by ELISA analysis. The expressions of MDM2, Ki-67, HK2, cleaved caspase-3 and p53 were detected by western blotting and immunohistochemistry. Xenograft tumor model was used to detect the role of LINC00504 in vivo. Results showed that LINC00504 was highly expressed in AML and its high expression was related with clinicopathological features in AML patients. LINC00504 knockdown significantly inhibited the proliferation and glycolysis, while induced apoptosis of AML cells. Meanwhile, LINC00504 downregulation also exerted a significant alleviating effect on AML cell growth in vivo. In addition, LINC00504 could bind to MDM2 protein and positively regulate its expression. Overexpression of LINC00504 promoted the malignant phenotypes of AML cells and partially reversed the inhibitory effects of LINC00504 knockdown on AML progression. In conclusion, LINC00504 facilitated AML cell proliferation and suppressed apoptosis through upregulating MDM2 expression, suggesting that LINC00504 may serve as a prognostic marker and therapeutic target in patients with AML.