Expression of the Transforming Growth Factor-α/Epidermal Growth Factor Receptor Pathway in Normal Human Breast Epithelial Cells

Abstract

To better understand the possible roles and interactions of transforming growth factor-alpha (TGF alpha) and its receptor, the epidermal growth factor (EGF) receptor in human breast epithelium, we have studied the expression of TGF alpha and the EGF receptor in a series of normal human mammary epithelial cells derived from reduction mammoplasty before in vitro propagation, during short term proliferation in vitro, and after immortalization. Increased TGF alpha mRNA expression coincided with conversion of the cells to a proliferative state in vitro. After establishment, propagation, and proliferation in vitro, the cells expressed high levels of both TGF alpha and EGF receptor mRNAs. Addition of diverse growth inhibitory agents, including 12-O-tetradecanoylphorbol-13-acetate (TPA), TGF beta, and sodium butyrate, to one of these rapidly proliferating cell populations (no. 184) failed to reduce the expression of either TGF alpha or the EGF receptor. Likewise, cessation of growth associated with both senescence and confluence of the 184 cells did not result in reduced expression. However, regulation of TGF alpha mRNA could be demonstrated by withdrawal of EGF from the medium or by antibody-mediated blockade of the EGF receptor in 184 cells. Antibody-mediated EGF receptor blockade also results in inhibition of growth and [3H]thymidine labeling. An autoregulatory autocrine loop appears operant in proliferating breast epithelial cells. Both growth and levels of TGF alpha mRNA expression are controlled by binding of ligand to the EGF receptor. These studies suggest a role for the TGF alpha/EGF receptor pathway in normal breast cell physiology.

Hypoxia induced by benign intestinal epithelial cells is associated with cyclooxygenase-2 expression in stromal cells through AP-1-dependent pathway

“…Identification of humoral factors secreted from benign (Intestine-407) and malignant (DLD-1) epithelial cells that may promote COX-2 induction in fibroblasts It is widely accepted that COX-2 expression is induced by various growth factors and proinflammatory cytokines (Bates et al, 1990;Salomon et al, 1995;Oshima et al, 1996;Smith et al, 2000;Yarden and Sliwkowski, 2001;Ricci et al, 2003;Li et al, 2004;Montano and Djamgoz, 2004). Since there was no direct contact between epithelial cells and fibroblasts in our co-culture system, it is reasonable to speculate that the increase in COX-2 expression in NIH3T3 fibroblasts observed Figure 1 In vitro co-culture models simulating colorectal tumorigenesis.…”

“…COX-1 is constitutively expressed in various normal tissues and exerts a variety of physiological functions, whereas COX-2 is rapidly induced in response to a number of stimuli, including growth factors and cytokines (Smith et al, 2000;Gupta and Dubois, 2001;Ricci et al, 2003;Oshima et al, 2005). Since many cancer tissues, including colorectal cancer tissues, produce various growth factors and cytokines (Bates et al, 1990;Salomon et al, 1995;Yarden and Sliwkowski, 2001;Tamura et al, 2002;Li et al, 2004;Montano and Djamgoz, 2004), COX-2 derived from advanced colorectal cancer cells seems to be induced by various growth factors and cytokines within the tumors (Bates et al, 1990;Eberhart et al, 1994;Salomon et al, 1995;Gupta and Dubois, 2001;Yarden and Sliwkowski, 2001;Tamura et al, 2002;Ricci et al, 2003;Li et al, 2004;Montano and Djamgoz, 2004). However, we and others have shown that in the earlier (premalignant) stage of colorectal tumorigenesis, that is, adenoma, COX-2 is expressed exclusively in polyp stromal cells, including macrophages, endothelial cells and fibroblasts (Eberhart et al, 1994;Gupta and Dubois, 2001;Seno et al, 2002;Ricci et al, 2003).…”

The PTEN/MMAC1/TEP tumor suppressor gene decreases cell growth and induces apoptosis and anoikis in breast cancer cells

“…To con®rm that the high basal and prolonged duration of AKT phosphorylation in MDA-MB-468 cells was due to mutations in PTEN and not due to overexpression of the EGFR (Bates et al, 1990), wildtype PTEN was reintroduced into these cells and its e ects on AKT phosphorylation was examined. As indicated in Figure 2B, introduction of wild-type PTEN resulted in a marked decrease in basal phosphorylation and in the duration of ligand-induced phosphorylation of co-transfected AKT.…”

An in vitro Human Mammary Epithelial Model System for Studies of Differentiation and Carcinogenesis

“…However, growth in mass culture proceeds without additional of exogenous EGF due to the significant level of endogenous production of TGFa (14). Addition of monoclonal antibody 225 IgG to the EGF receptor (MAb 225) prevents HMEC growth (15). Recent experiments have shown that MAb 225 produces a rapid, efficient, and reversible growth arrest in a Go or early G 1 phase of the cell cycle.…”