ABSTRACT
Lung cancer is the most common cause of cancer-related mortality worldwide. Here, we report elevated expression of tribbles homolog 2 (TRIB2) in primary human lung tumors and in non-small cell lung cancer cells that express low levels of differentiation-inducing transcription factor CCAAT/enhancer-binding protein alpha (C/EBPα). In approximately 10-20% of cases, elevated TRIB2 expression resulted from gene amplification. TRIB2 knockdown was found to inhibit cell proliferation and in vivo tumor growth. In addition, TRIB2 knockdown led to morphological changes similar to C/EBPα overexpression and correlated with increased expression and activity of C/EBPα. TRIB2-mediated regulation of C/EBPα was found to occur through the association of TRIB2 with the E3 ligase TRIM21. Together, these data identify TRIB2 as a potential driver of lung tumorigenesis through a mechanism that involves downregulation of C/EBPα.
Subject(s)
CCAAT-Enhancer-Binding Protein-alpha/metabolism , Down-Regulation , Gene Expression Regulation, Neoplastic , Intracellular Signaling Peptides and Proteins/metabolism , Lung Neoplasms/genetics , Lung Neoplasms/pathology , Animals , Calcium-Calmodulin-Dependent Protein Kinases , Cell Line, Tumor , Cell Proliferation , Cell Transformation, Neoplastic , Gene Knockdown Techniques , Humans , Intracellular Signaling Peptides and Proteins/deficiency , Intracellular Signaling Peptides and Proteins/genetics , Lung Neoplasms/metabolism , Mice , RNA, Small Interfering/genetics , Ribonucleoproteins/metabolismABSTRACT
The estrogen receptor-alpha gene (ESR1) was previously identified as a direct target of the homeobox transcription factor BARX2 in MCF7 cells. Here, we show that BARX2 and ESR1 proteins bind to different ESR1 gene promoters and regulate the expression of alternatively spliced mRNAs that encode 66 and 46 kDa ESR1 protein isoforms. BARX2 increases the expression of both ESR1 isoforms; however, it has a greater effect on the 46 kDa isoform, leading to an increased ratio between the 46 and 66 kDa proteins. BARX2 also influences estrogen-dependent processes such as anchorage-independent growth and modulates the expression of the estrogen-responsive genes SOX5, RBM15, Dynein and Mortalin. In addition, BARX2 expression promotes cellular invasion and increases the expression of active matrix metalloproteinase-9 (MMP9). BARX2 also increases the expression of the tissue inhibitor of metalloproteinase (TIMP) genes, TIMP1 and TIMP3, in cooperation with estrogen signaling. Overall, these data indicate that BARX2 and ESR1 may coordinately regulate cell growth, survival and invasion pathways that are critical to breast cancer progression.
Subject(s)
Estrogen Receptor alpha/physiology , Homeodomain Proteins/physiology , Alternative Splicing , Base Sequence , Breast Neoplasms/pathology , Cell Division , Cell Line, Tumor , Chromatin/physiology , DNA Primers , Estrogen Receptor alpha/genetics , Gene Expression Regulation, Neoplastic , Homeodomain Proteins/genetics , Humans , Matrix Metalloproteinases/genetics , Neoplasm Invasiveness , Protein Isoforms/genetics , RNA, Neoplasm/genetics , RNA, Neoplasm/isolation & purification , Tissue Inhibitor of Metalloproteinases/geneticsABSTRACT
We investigated the impact of maternal and fetal variables on cord blood (CB) haemopoietic stem/progenitor cell content. These included maternal age, ethnic origin, parity, ABO and Rhesus D blood group, antenatal haemoglobin, alcohol and cigarette consumption at time of registration, mode of delivery, duration of the first and second stages of labour, gestational age, birth weight, cord pH and cord erythrocyte mean cell volume (MCV). Cord volumes and total nucleated cellularities (TNC) were recorded, the colony assay for granulocyte-macrophage colony-forming-cells (CFU-GM) was used to quantify the progenitor cells and the potential of CFU-GM to produce secondary colonies on replating was used as a measure of progenitor cell quality. We found: (1) significantly greater (P=0.04) volumes were collected from babies who weighed > or = 2.5kg versus babies with a birth weight <2.5kg; (2) significantly greater numbers of mononuclear cells (MNC) from mothers who drank 0-3 units versus those who drank > or = 4 units of alcohol weekly (P=0.03), and in babies with a cord pH < or = 7.1 v > 7.1 (P=0.02); (3) Significantly greater numbers of cord CFU-GM in mothers who drank 0-3 v > or = 4 units weekly (P=0.004) and smokers of > or = 10 v 0-9 cigarettes daily (P=0.02) and in spontaneous vaginal deliveries than assisted vaginal and caesarean deliveries (P=0.04), and (4) the potential of CFU-GM to produce secondary colonies was significantly greater in CB derived from Caucasians than from non-Caucasians ( P=0.02); in assisted vaginal delivery v spontaneous vaginal (P=0.02) and in deliveries with prolonged first stage of labour v short first stage of labour (P=0.04). We conclude that antenatal and perinatal variables may influence the CB stem/progenitor cell yield available for transplantation.
