Transcriptional regulation of hTREX84 in human cancer cells

Andrographolide suppresses the malignancy of triple-negative breast cancer by reducing THOC1-promoted cancer stem cell characteristics

Triple-negative breast cancers (TNBCs) are difficult to cure and currently lack of effective treatment strategies. Cancer stem cells (CSCs) are highly associated with the poor clinical outcome of TNBCs. Thoc1 is a core component of the THO complex (THOC) that regulates the elongation, processing and nuclear export of mRNA. The function of thoc1 in TNBC and whether Thoc1 serves as a drug target are poorly understood. In this study, we demonstrated that thoc1 expression is elevated in TNBC cell lines and human TNBC patient tissues. Knockdown of thoc1 decreased cancer stem cell populations, reduced mammosphere formation, impaired THOC function, and downregulated the expression of stemness-related proteins. Moreover, the thoc1-knockdown 4T1 cells showed less lung metastasis in an orthotopic breast cancer mouse model. Overexpression of Thoc1 promoted TNBC malignancy and the mRNA export of stemness-related genes. Furthermore, treatment of TNBC cells with the natural compound andrographolide reduced the expression of Thoc1 expression, impaired homeostasis of THOC, suppressed CSC properties, and delayed tumor growth in a 4T1-implanted orthotopic mouse model. Andrographolide also reduced the activity of NF-κB, an upstream transcriptional regulator of Thoc1. Notably, thoc1 overexpression attenuates andrographolide-suppressed cellular proliferation. Altogether, our results demonstrate that THOC1 promotes cancer stem cell characteristics of TNBC, and andrographolide is a potential natural compound for eliminating CSCs of TNBCs by downregulating the NF-κB-thoc1 axis.

The role of TREX in gene expression and disease

TRanscription and EXport (TREX) is a conserved multisubunit complex essential for embryogenesis, organogenesis and cellular differentiation throughout life. By linking transcription, mRNA processing and export together, it exerts a physiologically vital role in the gene expression pathway. In addition, this complex prevents DNA damage and regulates the cell cycle by ensuring optimal gene expression. As the extent of TREX activity in viral infections, amyotrophic lateral sclerosis and cancer emerges, the need for a greater understanding of TREX function becomes evident. A complete elucidation of the composition, function and interactions of the complex will provide the framework for understanding the molecular basis for a variety of diseases. This review details the known composition of TREX, how it is regulated and its cellular functions with an emphasis on mammalian systems.

TRPM7 channels regulate glioma stem cell through STAT3 and Notch signaling pathways

Glioblastoma multiforme (GBM) is the most common and aggressive primary brain tumor in adults with median survival time of 14.6 months. A small fraction of cancer stem cells (CSC) initiate and maintain tumors thus driving glioma tumorigenesis and being responsible for resistance to classical chemo- and radio-therapies. It is desirable to identify signaling pathways related to CSC to develop novel therapies to selectively target them. Transient receptor potential cation channel, subfamily M, member 7, also known as TRPM7 is a ubiquitous, Ca(2+) and Mg(2+) permeable ion channels that are special in being both an ion channel and a serine/threonine kinase. In studies of glioma cells silenced for TRPM7, we demonstrated that Notch (Notch1, JAG1, Hey2, and Survivin) and STAT3 pathways are down regulated in glioma cells grown in monolayer. Furthermore, phospho-STAT3, Notch target genes and CSC markers (ALDH1 and CD133) were significantly higher in spheroid glioma CSCs when compared with monolayer cultures. The results further show that tyrosine-phosphorylated STAT3 binds and activates the ALDH1 promoters in glioma cells. We found that TRMP7-induced upregulation of ALDH1 expression is associated with increases in ALDH1 activity and is detectable in stem-like cells when expanded as spheroid CSCs. Finally, TRPM7 promotes proliferation, migration and invasion of glioma cells. These demonstrate that TRPM7 activates JAK2/STAT3 and/or Notch signaling pathways and leads to increased cell proliferation and migration. These findings for the first time demonstrates that TRPM7 (1) activates a previously unrecognized STAT3→ALDH1 pathway, and (2) promotes the induction of ALDH1 activity in glioma cells.

STAT3 regulates MMP3 in heme-induced endothelial cell apoptosis

BACKGROUND

We have previously reported that free Heme generated during experimental cerebral malaria (ECM) in mice, is central to the pathogenesis of fatal ECM. Heme-induced up-regulation of STAT3 and CXCL10 promotes whereas up-regulation of HO-1 prevents brain tissue damage in ECM. We have previously demonstrated that Heme is involved in the induction of apoptosis in vascular endothelial cells. In the present study, we further tested the hypothesis that Heme reduces blood-brain barrier integrity during ECM by induction of apoptosis of brain vascular endothelial cells through STAT3 and its target gene matrix metalloproteinase three (MMP3) signaling.

METHODS

Genes associated with the JAK/STAT3 signaling pathway induced upon stimulation by Heme treatment, were assessed using real time RT(2) Profile PCR arrays. A human MMP3 promoter was cloned into a luciferase reporter plasmid, pMMP3, and its activity was examined following exposure to Heme treatment by a luciferase reporter gene assay. In order to determine whether activated nuclear protein STAT3 binds to the MMP3 promoter and regulates MMP3 gene, we conducted a ChIP analysis using Heme-treated and untreated human brain microvascular endothelial cells (HBVEC), and determined mRNA and protein expression levels of MMP3 using qRT-PCR and Western blot. Apoptosis in HBVEC treated with Heme was evaluated by MTT and TUNEL assay.

RESULTS

The results show that (1) Heme activates a variety of JAK/STAT3 downstream pathways in HBVEC. STAT3 targeted genes such as MMP3 and C/EBPb (Apoptosis-related genes), are up regulated in HBVEC treated with Heme. (2) Heme-induced HBVEC apoptosis via activation of STAT3 as well as its downstream signaling molecule MMP3 and upregulation of CXCL10 and HO-1 expressions. (3) Phosphorylated STAT3 binds to the MMP3 promoter in HBVEC cells, STAT3 transcribed MMP3 and induced MMP3 protein expression in HBVEC cells.

CONCLUSIONS

Activated STAT3 binds to the MMP3 promoter region and regulates MMP3 in Heme-induced endothelial cell apoptosis.