SMYD3-PARP16 axis accelerates unfolded protein response and mediates neointima formation.

Neointimal hyperplasia after vascular injury is a representative complication of restenosis. Endoplasmic reticulum (ER) stress-induced unfolded protein response (UPR) is involved in the pathogenesis of vascular intimal hyperplasia. PARP16, a member of the poly(ADP-ribose) polymerases family, is correlated with the nuclear envelope and the ER. Here, we found that PERK and IRE1α are ADP-ribosylated by PARP16, and this might promote proliferation and migration of smooth muscle cells (SMCs) during the platelet-derived growth factor (PDGF)-BB stimulating. Using chromatin immunoprecipitation coupled with deep sequencing (ChIP-seq) analysis, PARP16 was identified as a novel target gene for histone H3 lysine 4 (H3K4) methyltransferase SMYD3, and SMYD3 could bind to the promoter of Parp16 and increased H3K4me3 level to activate its host gene's transcription, which causes UPR activation and SMC proliferation. Moreover, knockdown either of PARP16 or SMYD3 impeded the ER stress and SMC proliferation. On the contrary, overexpression of PARP16 induced ER stress and SMC proliferation and migration. In vivo depletion of PARP16 attenuated injury-induced neointimal hyperplasia by mediating UPR activation and neointimal SMC proliferation. This study identified SMYD3-PARP16 is a novel signal axis in regulating UPR and neointimal hyperplasia, and targeting this axis has implications in preventing neointimal hyperplasia related diseases.

Tumor suppressive miRNA-34a suppresses cell proliferation and tumor growth of glioma stem cells by targeting Akt and Wnt signaling pathways.

MiRNA-34a is considered as a potential prognostic marker for glioma, as studies suggest that its expression negatively correlates with patient survival in grade III and IV glial tumors. Here, we show that expression of miR-34a was decreased in a graded manner in glioma and glioma stem cell-lines as compared to normal brain tissues. Ectopic expression of miR-34a in glioma stem cell-lines HNGC-2 and NSG-K16 decreased the proliferative and migratory potential of these cells, induced cell cycle arrest and caused apoptosis. Notably, the miR-34a glioma cells formed significantly smaller xenografts in immuno-deficient mice as compared with control glioma stem cell-lines. Here, using a bioinformatics approach and various biological assays, we identify Rictor, as a novel target for miR-34a in glioma stem cells. Rictor, a defining component of mTORC2 complex, is involved in cell survival signaling. mTORC2 lays downstream of Akt, and thus is a direct activator of Akt. Our earlier studies have elaborated on role of Rictor in glioma invasion (Das et al., 2011). Here, we demonstrate that miR34a over-expression in glioma stem cells profoundly decreased levels of p-AKT (Ser473), increased GSK-3ß levels and targeted for degradation ß-catenin, an important mediator of Wnt signaling pathway. This led to diminished levels of the Wnt effectors cyclin D1 and c-myc. Collectively, we show that the tumor suppressive function of miR-34a in glioblastoma is mediated via Rictor, which through its effects on AKT/mTOR pathway and Wnt signaling causes pronounced effects on glioma malignancy.

Dihydroartemisinin induces autophagy and inhibits the growth of iron-loaded human myeloid leukemia K562 cells via ROS toxicity.

Dihydroartemisinin (DHA), an active metabolite of artemisinin derivatives, is the most remarkable anti-malarial drug and has little toxicity to humans. Recent studies have shown that DHA effectively inhibits the growth of cancer cells. In the present study, we intended to elucidate the mechanisms underlying the inhibition of growth of iron-loaded human myeloid leukemia K562 cells by DHA. Mitochondria are important regulators of both autophagy and apoptosis, and one of the triggers for mitochondrial dysfunction is the generation of reactive oxygen species (ROS). We found that the DHA-induced autophagy of leukemia K562 cells, whose intracellular organelles are primarily mitochondria, was ROS dependent. The autophagy of these cells was followed by LC3-II protein expression and caspase-3 activation. In addition, we demonstrated that inhibition of the proliferation of leukemia K562 cells by DHA is also dependent upon iron. This inhibition includes the down-regulation of TfR expression and the induction of K562 cell growth arrest in the G2/M phase.