Downregulation of TNFR2 decreases survival gene expression, promotes apoptosis and affects the cell cycle of gastric cancer cells.

BACKGROUND: Chronic inflammation due to Helicobacter pylori (H. pylori) infection promotes gastric carcinogenesis. Tumour necrosis factor-α (TNF-α), a key mediator of inflammation, induces cell survival or apoptosis by binding to two receptors (TNFR1 and TNFR2). TNFR1 can induce both survival and apoptosis, while TNFR2 results only in cell survival. The dysregulation of these processes may contribute to carcinogenesis. AIM: To evaluate the effects of TNFR1 and TNFR2 downregulation in AGS cells treated with H. pylori extract on the TNF-α pathway. METHODS: AGS cell lines containing TNFR1 and TNFR2 receptors downregulated by specific shRNAs and nonsilenced AGS cells were treated with H. pylori extract for 6 h. Subsequently, quantitative polymerase chain reaction with TaqMan® assays was used for the relative quantification of the mRNAs (TNFA, TNFR1, TNFR2, TRADD, TRAF2, CFLIP, NFKB1, NFKB2, CASP8, CASP3) and miRNAs (miR-19a, miR-34a, miR-103a, miR-130a, miR-181c) related to the TNF-α signalling pathway. Flow cytometry was employed for cell cycle analysis and apoptosis assays. RESULTS: In nonsilenced AGS cells, H. pylori extract treatment increased the expression of genes involved in cell survival and inhibited both apoptosis (NFKB1, NFKB2 and CFLIP) and the TNFR1 receptor. TNFR1 downregulation significantly decreased the expression of the TRADD and CFLIP genes, although no change was observed in the cellular process or miRNA expression. In contrast, TNFR2 downregulation decreased the expression of the TRADD and TRAF2 genes, which are both important downstream mediators of the TNFR1-mediated pathway, as well as that of the NFKB1 and CFLIP genes, while upregulating the expression of miR-19a and miR-34a. Consequently, a reduction in the number of cells in the G0/G1 phase and an increase in the number of cells in the S phase were observed, as well as the promotion of early apoptosis. CONCLUSION: Our findings mainly highlight the important role of TNFR2 in the TNF-α pathway in gastric cancer, indicating that silencing it can reduce the expression of survival and anti-apoptotic genes.

Condemned or Not to Die? Gene Polymorphisms Associated With Cell Death in Pemphigus Foliaceus.

Pemphigus foliaceus (PF) is an autoimmune blistering skin disease that occurs sporadically across the globe and is endemic in Brazil. Keratinocyte adhesion loss (acantholysis) is associated with high levels of anti-desmoglein 1 IgG autoantibodies, but the role of cell death is poorly understood in PF. Current evidence disqualifies apoptosis as the major cell death mechanism and no other process has yet been investigated. To approach the role of variation in genes responsible for cell death pathways in pemphigus susceptibility, we systematically investigated the frequencies of 1,167 polymorphisms from genes encoding products of all 12 well-established cell death cascades (intrinsic and extrinsic apoptosis, necrosis, necroptosis, ferroptosis, pyroptosis, parthanatos, entotic, NETotic, lysosome-dependent, autophagy-dependent, and immunogenic). By multivariate logistic regression, we compared allelic and genotypic frequencies of 227 PF patients and 194 controls obtained by microarray hybridization. We found 10 variants associated with PF (p < 0.005), belonging to six cell death pathways: apoptosis (TNF, TRAF2, CD36, and PAK2), immunogenic cell death (EIF2AK3, CD47, and SIRPA), necroptosis (TNF and TRAF2), necrosis (RAPGEF3), parthanatos (HK1), and pyroptosis (PRKN). Five polymorphisms were associated with susceptibility: TNF rs1800630*A (OR = 1.9, p = 0.0003), CD36 rs4112274*T (OR = 2.14, p = 0.0015), CD47 rs12695175*G (OR = 1.77, p = 0.0043), SIRPA rs6075340*A/A (OR = 2.75, p = 0.0009), and HK1 rs7072268*T (OR = 1.48, p = 0.0045). Other five variants were associated with protection: TRAF2 rs10781522*G (OR = 0.64, p = 0.0014), PAK2 rs9325377*A/A (OR = 0.48, p = 0.0023), EIF2AK3 rs10167879*T (OR = 0.48, p = 0.0007), RAPGEF3 rs10747521*A/A (OR = 0.42, p = 0.0040), and PRKN rs9355950*C (OR = 0.57, p = 0.0004). Through functional annotation, we found that all associated alleles, with the exception of PRKN rs9355950*C, were previously associated with differential gene expression levels in healthy individuals (mostly in skin and peripheral blood). Further functional validation of these genetic associations may contribute to the understanding of PF etiology and to the development of new drugs and therapeutic regimens for the disease.

Experimental intestinal endometriosis is characterized by increased levels of soluble TNFRSF1B and downregulation of Tnfrsf1a and Tnfrsf1b gene expression.

Endometriosis is commonly associated with symptoms similar to those of gastrointestinal diseases, such as inflammatory bowel disease (IBD), leading to erroneous diagnosis and inappropriate management. The role of tumor necrosis factor alpha (TNF) in IBD is well established, but its role in endometriosis--also characterized by the activation of inflammatory mechanisms--is still under study. Furthermore, little is known about the involvement of TNF receptors. Intestinal endometriosis was surgically induced in female Sprague-Dawley rats (n = 10). Control rats (n = 10) received sutures with no implants. Samples of tissue and fluids were collected 60 days after surgery. Endometriotic implants were classified in grades, and the gastrointestinal tract was examined for damage. A significant increase was observed in protein levels of TNF and soluble TNFRSF1B in the peritoneal fluid of experimental rats compared to controls. Expression of Tnf mRNA was significantly increased both in peritoneal leukocytes and in intestinal segments associated with implants in experimental animals. Bioactivity of TNF in tissues was confirmed by overexpression of Icam1, Sele, Vegfa, Flt1 and Kdr. Gene expression of Tnfrsf1a and Tnfrsf1b was downregulated in colon and small intestine of experimental animals, possibly as a mechanism of protection against TNF cytotoxicity. Significant overexpression of genes encoding TNF receptor-associated factors that have been linked to activation of antiapoptotic pathways also was observed. Overexpression of TNF and target genes, underexpression of TNF-receptor genes, and increased shedding of TNFRSF1B in this animal model provide further evidence for involvement of the TNF system in the pathogenesis of endometriosis.