The androgen receptor (AR), as a classic steroid receptor, generally mediates biologic responses to androgens. In bone tissue, both AR and the estrogen receptor (ER) are expressed in a variety of cell types. Because androgens can be converted into estrogen via aromatase activity, the specific role of the AR in maintenance of skeletal homoeostasis remains controversial. The goal of this study was to use skeletally targeted overexpression of AR as a means of elucidating the specific role(s) for AR transactivation in bone homeostasis. Rat AR cDNA was cloned downstream of a 3.6-kb alpha1(I)-collagen promoter fragment and used to create AR-transgenic mice. AR-transgenic males gain less weight and body and femur length is shorter than wild-type controls, whereas females are not different. AR-transgenic males also demonstrate thickened calvaria and increased periosteal but reduced endosteal labeling by fluorescent labeling and reduced osteocalcin levels. High-resolution micro-computed tomography shows normal mineral content in both male and female AR-transgenic mice, but male AR-transgenics reveal a reduction in cortical area and moment of inertia. Male AR-transgenics also demonstrate an altered trabecular morphology with bulging at the metaphysis. Histomorphometric analysis of trabecular bone parameters confirmed the increased bone volume comprised of more trabeculae that are closer together but not thicker. Biomechanical analysis of the skeletal phenotype demonstrate reduced stiffness, maximum load, post-yield deflection, and work-to-failure in male AR-transgenic mice. Steady-state levels of selected osteoblastic and osteoclastic genes are reduced in tibia from both male and female transgenics, with the exception of increased osteoprotegerin expression in male AR-transgenic mice. These results indicate that AR action is important in the development of a sexually dimorphic skeleton and argue for a direct role for androgen transactivation of AR in osteoblasts in modulating skeletal development and homeostasis.

Arsenic is highly effective for treating acute promyelocytic leukemia (APL) and has shown significant promise against many other tumors. However, although its mechanistic effects in APL are established, its broader anticancer mode of action is not understood. In this study, using a human proteome microarray, we identified 360 proteins that specifically bind arsenic. Among the most highly enriched proteins in this set are those in the glycolysis pathway, including the rate-limiting enzyme in glycolysis, hexokinase-1. Detailed biochemical and metabolomics analyses of the highly homologous hexokinase-2 (HK2), which is overexpressed in many cancers, revealed significant inhibition by arsenic. Furthermore, overexpression of HK2 rescued cells from arsenic-induced apoptosis. Our results thus strongly implicate glycolysis, and HK2 in particular, as a key target of arsenic. Moreover, the arsenic-binding proteins identified in this work are expected to serve as a valuable resource for the development of synergistic antitumor therapeutic strategies.arsenic trioxide | human proteome microarray | glycolysis | hexokinase-2IA rsenic and its derivatives have been applied as therapy for a variety of diseases for more than 2,200 y (1). To date, the disease most successfully treated with these types of compounds is acute promyelocytic leukemia (APL). Administration of arsenic trioxide (ATO) combined with all-trans retinoic acid has demonstrated a remarkable 5-y overall survival rate of 85-90% as a consequence of the dramatic down-regulation of the key protein driving APL tumorigenicity, promyelocytic leukemia-retinoic acid receptor α (PML-RARα) (2). However, ATO also has been found to be effective against many other hematologic malignancies and solid tumors. For example, together with imatinib it is a promising treatment for chronic myelocytic leukemia (3), and it has been used alone with some success to treat multiple myeloma (4), myelodysplasia syndrome (5), and non-Hodgkin lymphoma (6). ATO also is under clinical investigation as a possible medication for lung cancer, hepatocellular carcinoma, melanoma, renal cell carcinoma, and colorectal cancer (https://www.clinicaltrials.gov/). At the cellular level, ATO has been shown to inhibit significantly the growth of almost all the cell lines (59 of 60) in the US National Cancer Institute anticancer drug screen that spans nine different tumor types (7). Thus ATO is one of the most promising broadly effective medications against cancer.Although its mode of action in APL is well established, the underlying mechanisms by which ATO acts in other types of cancers remain poorly understood. A variety of systematic studies, including studies that provided transcriptomic, chemogenomic, or proteomic characterizations (8, 9), have been performed to gain a better understanding of this broader anticancer activity of ATO. However, these studies examined only the cellular consequences of treatment with ATO without identifying the primary proteins directly bound and modulated by ATO. Knowledge of ATO...

BackgroundChromobox protein homolog 7 (CBX7), a member of the polycomb group (PcG) family of proteins, is involved in the regulation of cell proliferation and cancer progression. PcG family members, such as BMI, Mel-18, and EZH2, are integral constituents of the polycomb repressive complexes (PRCs) and have been known to regulate cancer stem cell (CSC) phenotype. However, the role of other PRCs’ constituents such as CBX7 in the regulation of CSC phenotype remains largely elusive. This study was to investigate the role of CBX7 in regulating stem cell-like properties of gastric cancer and the underlying mechanisms.MethodsFirstly, the role of CBX7 in regulating stem cell-like properties of gastric cancer was investigated using sphere formation, Western blot, and xenograft tumor assays. Next, RNA interference and ectopic CBX7 expression were employed to determine the impact of CBX7 on the expression of CSC marker proteins and CSC characteristics. The expression of CBX7, its downstream targets, and stem cell markers were analyzed in gastric stem cell spheres, common cancer cells, and gastric cancer tissues. Finally, the pathways by which CBX7 regulates stem cell-like properties of gastric cancer were explored.ResultsWe found that CBX7, a constituent of the polycomb repressive complex 1 (PRC1), plays an important role in maintaining stem cell-like characteristics of gastric cancer cells via the activation of AKT pathway and the downregulation of p16. Spearman rank correlation analysis showed positive correlations among the expression of CBX7 and phospho-AKT (pAKT), stem cell markers OCT-4, and CD133 in gastric cancer tissues. In addition, CBX7 was found to upregulate microRNA-21 (miR-21) via the activation of AKT-NF-κB pathway, and miR-21 contributes to CBX7-mediated CSC characteristics.ConclusionsCBX7 positively regulates stem cell-like characteristics of gastric cancer cells by inhibiting p16 and activating AKT-NF-κB-miR-21 pathway.Electronic supplementary materialThe online version of this article (10.1186/s13045-018-0562-z) contains supplementary material, which is available to authorized users.