Modulation of NFκB Activity and E-cadherin by the Type III Transforming Growth Factor β Receptor Regulates Cell Growth and Motility

Abstract

Transforming growth factor ␤ is growth-inhibitory in nontransformed epithelial cells but becomes growth-promoting during tumorigenesis. The role of the type I and II receptors in tumorigenesis has been extensively studied, but the role of the ubiquitously expressed type III receptor (T␤RIII) remains elusive. We developed short hairpin RNAs directed against T␤RIII to investigate the role of this receptor in breast cancer tumorigenesis. Nontumorigenic NMuMG mouse cells stably expressing short hairpin RNA specific to mouse T␤RIII (NM-kd) demonstrated increased cell growth, motility, and invasion as compared with control cells expressing shRNA to human T␤RIII (NM-con). Reconstitution of T␤RIII expression with rat T␤RIII abrogated the increased growth and motility seen in the NM-kd cells. In addition, the NM-kd cells exhibited marked reduction in the expression of the adherens junction protein, E-cadherin. This loss of E-cadherin was due to increased NFB activity that, in turn, resulted in increased expression of the transcriptional repressors of E-cadherin such as Snail, Slug, Twist, and Sip1. Finally, NMuMG cells in which T␤RIII had been knocked down formed invasive tumors in athymic nude mice, whereas the control cells did not. These data indicate that T␤RIII acts as a tumor suppressor in nontumorigenic mammary epithelial cells at least in part by inhibiting NFB-mediated repression of E-cadherin. The transforming growth factor (TGF)3 ␤s belong to a family of pleitropic cytokines that are involved in cell growth and proliferation, differentiation, deposition of extracellular matrix, and motility (1). The three TGF␤ isoforms (␤1, ␤2, and ␤3) bind to transmembrane receptor serine/threonine kinases. TGF␤1 and TGF␤3 can bind with high affinity to the TGF␤ type II receptor, resulting in activation of Smad 2/3 and downstream target genes. In contrast, TGF␤2 binds with low affinity to the type II receptor. The type III receptor (T␤RIII), or betaglycan, binds with high affinity to all three TGF␤ isoforms and is required for presenting TGF␤2 to the type II receptor (2).T␤RIII has been shown to play an essential role in the formation of the atrioventricular cushion in the development of the heart (3). Consistent with this observation, the T␤RIII null mouse is embryonically lethal because of heart and liver defects (4). The role for T␤RIII in cancer is less clear. Increased expression of TGF␤1 and all three TGF␤ receptors was found in higher grade lymphomas (5). Conversely, reduced expression of T␤RIII was found associated with advanced stage neuroblastomas and ovarian carcinomas (6, 7). Similarly, a recent report using cDNA microarrays demonstrated that low T␤RIII expression correlates with higher grade among a cohort of breast cancers (8). Additionally, overexpression of T␤RIII in MDA-231 human breast cancer cells and DU145 prostate cancer cells resulted in decreased tumor invasion in vitro and in vivo (9, 10). The reasons for this apparent contradictory role for T␤RIII in these different tumor types have not been elucidate...

Requirement of the Akt/β-Catenin Pathway for Uterine Carcinosarcoma Genesis, Modulating E-Cadherin Expression Through the Transactivation of Slug

“…In addition, although induction of myr-Akt was also found to activate p65-dependent transcription, probably through repression of IB␣ expression, 33 we failed to confirm such an association in tumor tissues, suggesting that the in vivo pp65 status may be affected not only by pAkt but also by other factors, such as transforming growth factor-␤ and tumor necrosis factor-␣. 34,35 In our results, expression of Slug, rather than Snail, appeared to be closely associated with the mesenchymal phenotype in UCSs, despite both being capable of repressing E-cadherin expression. 12,13 A similar finding has also been reported for basal-like breast carcinomas.…”

Knockdown of the Transforming Growth Factor-β Type III Receptor Impairs Motility and Invasion of Metastatic Cancer Cells

“…Additionally, a recent report using cDNA microarrays showed that decreased ThRIII expression correlated with higher tumor grade in a cohort of breast cancers (4). Our laboratory has recently published data supporting a tumor suppressor role for ThRIII in nontumorigenic NMuMG mammary epithelial cells that is dependent on the ability of ThRIII to modulate nuclear factor-nB (NF-nB) signaling (6). In contrast, an oncogenic role for ThRIII was suggested by studies in lymphoma, B-chronic lymphocytic leukemia, and certain ovarian tumors (7)(8)(9).…”

“…All cells were maintained in a humidified 5% CO 2 incubator at 37jC. Retroviruses expressing shRNAs specific to mouse or human ThRIII were generated as previously described (6). Retrovirus containing mouse or human sh-RIII were used to infect MDA-231 and PMTLuc cells in the presence of 4 Ag/mL polybrene.…”

“…Electrophoretic mobility shift assays (EMSA) were performed using the Promega Gel Shift Assay kit (Promega) according to the manufacturer's protocol, as previously described (6). Nuclear extracts were harvested, as described previously (24).…”

Decreased expression of the type III TGF-β receptor enhances metastasis and invasion in hepatocellullar carcinoma progression

“…TβRIII has been shown to have effects on both the Smad and non-Smad signaling pathways in a liganddependent or -independent manner, including the Smad, NF-κB and p38 signaling pathways (33)(34)(35). In mouse lung fibroblasts, the expression of TβRIII was found to reduce the phosphorylation of Smad2, Smad3 and Akt (36).…”