TNFα induces NFκB/p50 in association with the growth and morphogenesis of normal and transformed rat mammary epithelial cells

Abstract

In contrast to the cytotoxic or cytostatic effect of TNFalpha on many breast cancer cell lines, TNFalpha stimulates growth and morphogenesis of normal rat mammary epithelial cells (MEC). The present studies were carried out to determine whether there are intrinsic differences between normal and malignant MEC which may explain the differing responsiveness to TNFalpha. Freshly isolated rat MEC organoids from normal mammary gland or 1-methyl-1-nitrosourea-induced mammary tumors were treated with TNFalpha for 21 days. Unexpectedly, TNFalpha stimulated growth and morphogenesis of both normal and transformed MEC in primary culture, although in transformed cells its effects were delayed and the majority of the colonies were histologically abnormal, with multiple cell layers and no lumen. Since NFkappaB is a key mediator of TNFalpha action and has been implicated in carcinogenesis, the expression of the p50, p52, p65, and c-rel NFkappaB proteins in normal and transformed MEC was determined. Expression of p52 was significantly reduced in tumor cells, and p50 was absent, although its putative precursor, p105 was abundant. There were no changes in the levels of p65 or c-rel. TNFalpha induced a pronounced and sustained increase of a p50 homodimeric NFkappaB/DNA complex in both normal and transformed MEC. However, in transformed MEC, NFkappaB binding was initially undetectable but then increased in response to TNFalpha. Thus, NFkappaB expression and DNA binding activity are altered during mammary carcinogenesis. In addition, the significant increase in NFkappaB/p50 DNA-binding was temporally coincident with TNFalpha-induced growth and morphogenesis, suggesting that it may play a significant role in both normal development and carcinogenesis.

Tumor necrosis factor deficiency inhibits mammary tumorigenesis and a tumor necrosis factor neutralizing antibody decreases mammary tumor growth in neu/erbB2 transgenic mice

“…Moreover, treatment of mammary tumor-bearing mice with an antibody that neutralizes TNF inhibited tumor growth. Although these studies were conducted using the neu/ erbB2 transgenic mouse model, based on our previous data demonstrating that TNF increases the proliferation of primary malignant mammary cells from NMU-induced rat mammary tumors, as well as normal rat and mouse mammary epithelial cells (1,5,13,24), we believe that the observed effects are more general in nature, and are not limited to neu/erbB2-overexpressing breast cancers.…”

“…These effects appear to be physiologically relevant because expression of TNF and its two receptors is regulated throughout normal mammary gland development (1). Furthermore, TNF also stimulated the growth and morphogenesis of organoids derived from 1-methyl-1-nitrosourea-induced rat mammary tumors (13), demonstrating the potential for TNF-induced growth of mammary tumors in vivo. TNF may also play a role in metastasis, as it stimulates matrix metalloproteinase-9 secretion from mammary epithelial cells (10,11) as well as the surrounding stroma (14).…”

“…We previously showed that TNF stimulated the growth of normal rat and mouse mammary epithelial cells, as well as 1-methyl-1-nitrosourea-induced rat mammary tumor cells, in a three-dimensional primary culture model (1,5,13,24). These observations suggested that TNF might stimulate mammary tumorigenesis in vivo.…”

Induced Autocrine Signaling through the Epidermal Growth Factor Receptor Contributes to the Response of Mammary Epithelial Cells to Tumor Necrosis Factor α

“…In particular, normal mammary epithelial cells (MECs) are relatively resistant to TNF cytotoxicity as compared with mammary cancer cells (4,5), and some reports suggest TNF plays a physiological role as both a survival factor and mitogen in normal mammary epithelium (6 -8). For example, in primary rat MECs, TNF stimulates proliferation and up-regulates matrix metalloproteases necessary for cell motility and branching morphogenesis (6,7). MEC proliferation and branching during puberty is also delayed in TNF null mice (9).…”

The molecular contribution of TNF-α in the link between obesity and breast cancer

“…These differences may contribute to the different effect of TNF-· on these cells, which may also apply to the other differences observed. In MCF-10A breast epithelial cells, treatment with 10 ng/ml TNF-· increased cell proliferation after 24 and 48 h. In rat breast epithelial cells TNF-· treatment similarly increased proliferation (33,34). Our results indicate that TNF-· treatment has a substantial and sustained effect on promoting cell proliferation in MCF-10A cells.…”