Cox-2 inactivates Smad signaling and enhances EMT stimulated by TGF-  through a PGE2-dependent mechanisms

Abstract

Although it is well established that mammary tumorigenesis converts transforming growth factor-beta (TGF-beta) from a tumor suppressor to a tumor promoter, the molecular, cellular and microenvironmental mechanisms underlying the dichotomous nature of TGF-beta in mammary epithelial cells (MECs) remains to be determined definitively. Aberrant upregulation of the inducible cyclooxygenase, Cox-2, occurs frequently in breast cancers and is associated with increasing disease severity and the acquisition of metastasis; however, the impact of Cox-2 expression on normal and malignant MEC response to TGF-beta remains unknown. We show here that TGF-beta induced Cox-2 expression in normal MECs during their acquisition of an epithelial-mesenchymal transition (EMT) phenotype. Moreover, stable Cox-2 expression in normal MECs stimulated their invasion, EMT and anchorage-independent growth and inhibited their activation of Smad2/3 by TGF-beta. Conversely, antagonizing TGF-beta signaling in malignant, metastatic MECs significantly reduced their expression of Cox-2 as well as enhanced their activation of Smad2/3 by TGF-beta. Along these lines, elevated Cox-2 expression elicited prostaglandin E(2) (PGE(2)) production and the autocrine activation of EP receptors, which antagonized Smad2/3 signaling in normal and malignant MECs. Importantly, rendering normal and malignant MECs Cox-2 deficient inhibited their production of PGE(2) and acquisition of an EMT morphology as well as potentiated their nuclear accumulation of Smad2/3 and transcription of plasminogen activator inhibitor-1 and p15 messenger RNA. Collectively, our findings establish Cox-2 as a novel antagonist of Smad2/3 signaling in normal and malignant MECs; they also suggest that chemotherapeutic targeting of Cox-2 may offer new inroads in restoring the tumor-suppressing activities of TGF-beta in malignant, metastatic breast cancers.

Intratumoral forkhead box P3‐positive regulatory T cells predict poor survival in cyclooxygenase‐2–positive uveal melanoma

“…3 In addition, TGF-b and COX-2 have synergistic effects within the process of carcinogenesis. 36 For future studies, it will be of interest to evaluate the association between TGF-b in combination with COX-2/ PGE 2 and Tregs, especially with regard to its prognostic value in UM.…”

Type I collagen inhibits differentiation and promotes a stem cell-like phenotype in human colorectal carcinoma cells

“…ZEB1 represses differentiation and cell -cell adhesion in human colorectal carcinoma cells (Aigner et al, 2007). In addition, a stable COX-2 expression in breast epithelial cells enhances EMT (Neil et al, 2008). Therefore, it seems likely that the elevated levels of COX-2 in Colony 29 cells (Chinery et al, 1999) are involved in enhancing the response of these cells to type I collagen.…”

p130Cas Is Required for Mammary Tumor Growth and Transforming Growth Factor-β-mediated Metastasis through Regulation of Smad2/3 Activity

“…non-silencing shRNA) or murine-directed p130Cas shRNA (pLKO.1; Thermo Scientific, Huntsville, AL). The production of pLKO.1 lentiviral particles and their transduction into target cells was accomplished as described previously (23). In addition, NMuMG and 4T1 cells also were transduced with murine ecotropic retroviral particles that encoded for full-length p130Cas (pMSCV-Cas-FL), the carboxyl terminus of p130Cas (amino acids 544 -874) (pMSCV-Cas-CT), or T␤R-II (pMSCV-T␤R-II), and the resulting polyclonal populations were selected by yellow fluorescence protein, or hygromycin resistance (200 g/ml).…”

“…Afterward, the resulting whole cell extracts were clarified by microcentrifugation prior to being immunoblotted with the following primary antibodies Real-time PCR Analyses-Quiescent 4T1 cells were stimulated with TGF-␤1 (5 ng/ml) for 24 h in the absence or presence of the p38 MAPK inhibitor SB208530 (10 M) and total RNA was isolated using the RNeasy Plus Kit (Qiagen, Valen-cia, CA). Afterward, total RNA was reverse transcribed using the iScript cDNA Synthesis System (Bio-Rad) and semiquantitative real-time PCR was conducted for PAI-1 using iQ SYBR Green (Bio-Rad) according to the manufacturer's recommendations and as described previously (23). Differences in RNA concentrations were controlled by normalizing individual gene signals to their corresponding glyceraldehyde-3-phosphate dehydrogenase signal.…”