Mammalian target of rapamycin inhibitor abrogates abnormal osteoclastogenesis in neurofibromatosis type 1 / 中华医学杂志(英文版)

<p><b>BACKGROUND</b>Neurofibromatosis type 1 (NF1) is the most common genetic syndrome predisposing patients to various tumors due to dysregulation of the Ras signaling pathway. Recent research has shown NF1 patients also suffer a spectrum of bone pathologies. The pathogenesis of NF1 bone diseases is largely unknown. There is no current treatment. By Nf1 heterozygote (Nf1+/-) mice and Nf1 conditional knockout mice, we and other groups demonstrated abnormal osteoblast and osteoclast function due to dysregulation of Ras signaling. However, the specific downstream effector pathways linked to NF1 abnormal osteoblastogenesis and osteoclastogenesis have not been defined. In this study, we investigated the Ras downstream effector related with NF1 bone disease.</p><p><b>METHODS</b>We used Nf1+/+ and Nf1+/- mice as normal and NF1 models. Bone stromal cells extracted from Nf1+/+ and Nf1+/- mice were induced osteoclasts. The osteoclast cell was stained by tartrate resistant acid phosphatase staining. The osteoclast cell number was counted and the surface area of osteoclast cells was calculated under the microscope. The mRNA of mammalian target of rapamycin (mTOR) was determined by quantitative reverse-transcription-polymerase chain reaction. The presence of ribosomal protein S6 kinase was determined by Western blotting.</p><p><b>RESULTS</b>Compared with Nf1+/+ mice, Nf1+/- mice had about 20% more of osteoclast cells. These osteoclast cells were larger in size with more nuclei. Hyperactive mTOR was detected in Nf1+/- osteoclast cells. Inhibition of mTOR signaling by rapamycin in Nf1+/- osteoclasts abrogated abnormalities in cellular size and number.</p><p><b>CONCLUSION</b>mTOR pathway inhibition may represent a viable therapy for NF1 bone diseases.</p>

Histone deacetylase inhibitors inducing human cervical cancer cell apoptosis by decreasing DNA-methyltransferase 3B / 中华医学杂志(英文版)

<p><b>BACKGROUND</b>Histone deacetylase (HDAC) inhibitors are a group of small chemical molecules that inhibit histone deacetylase. At cell level, HDAC inhibitors have multiple biological effects such as cell cycle arrest, apoptosis, cell differentiation and auotophagy. At molecular level, HDAC inhibitors cause histone and nonhistone acetylation and induce gene expression. HDAC inhibitors are widely used in cancer therapy because of its function of inducing apoptosis. However, the mechanisms of apoptosis effect are not fully understood. TSA is a classical HDAC inhibitor and widely used in epigenetic and anti-cancer research. In this study, we selected Trichostatin A (TSA) to investigate the mechanisms of HDAC inhibitors apoptotic effect on cancer cells.</p><p><b>METHODS</b>Cervical cancer cell lines such as Hela, Caski and normal human keratinocyte line HaCaT were treated with various concentrations of TSA. Crystal violent assay and 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay were performed to determine cell number. PARP cleavage and FITC-AnexinV were performed to determine apoptosis. DNA-methyltransferase (DNMT)1, DNMT3A and DNMT3B were determined by regular PCR, qPCR and Western Blotting. Small interfering RNA (SiRNAi) was used to knock down DNMT3B.</p><p><b>RESULTS</b>HDAC inhibitors only induce cervical cancer cell apoptosis. At 1 µmol/L of TSA, 86% of Hela cell and 76% of Caski went apoptosis. For normal cells, HDAC inhibitors have no cytotoxic effect at therapeutic dosage, (90.0 ± 8.4)% of normal cell survive after treated with 1 µmol/L of TSA. We compared 1 µmol/L group with untreated control with t-test. There was no significance between 1 µmol/L group and untreated control for normal cell (P > 0.05). HDAC inhibitors decreased DNMT3B in cancer cell but not in normal cell. Manually knock-down of DNMT3B induced Hela and Caski cell apoptosis. More than 99% of Hela and Caski cell went apoptosis after deprived of DNMT3B.</p><p><b>CONCLUSIONS</b>DNMT3B was essential to cervical cancer cell survival. Down-regulated DNMT3B by HDAC inhibitors may play an important role in the toxicity of HDAC inhibitors on cervical cancer cells.</p>