Tumor necrosis alpha induces proliferation and increases responsiveness to progestin in mammary tumor cells.

SCHILLACI R ; RIVAS MA ; ROSEMBLIT C ; CARNEVALE R ; SALATINO M ; PROIETTI CJ ; CHARREAU EH ; ELIZALDE PV

Orlando

Congreso; AACR Annual Meeting; 2004

American Associatiom of Cancer Research (AACR)

Tumor necrosis factor alpha (TNF-a) has been found to exert cytostatic and cytotoxic activities in several breast cancer cell lines. However, these effects can be modulated by hormonal environment. While TNF-a has been found to antagonize estradiol stimulation of cell growth in a dose-dependent manner, the presence of interactions between TNF-a and progestin remains less characterized. The purpose of the present study was to investigate TNF-a effect on proliferation in an experimental model of hormonal carcinogenesis in which the synthetic progestin medroxyprogesterone acetate (MPA) induced mammary adenocarcinomas in female Balb/c mice. TNF-a was able to induce proliferation of primary cultures of C4HD epithelial cells, from the MPA-induced mammary tumor model, in a dose-dependent fashion.  To identify molecular mechanisms required for TNF-a-induced  C4HD cell proliferation, we studied p42/p44 mitogen-activated protein kinase (MAPK), p-38 MAPK and  phosphatidylinositol 3-kinase (PI3-K)/Akt signaling pathways. TNF-a induced a strong degree of  p42/p44 MAPK and Akt phosphorylation in C4HD cells. On the other hand, TNF-a had no effect on  p-38 MAPK phosphorylation. While inhibition of p42/p44 MAPK with the selective MEK1 inhibitor PD98059 resulted in significant reduction of TNF-a proliferative effects, PI-3K/Akt blockage with wortmannin completely abolished TNF-a-mediated proliferation of C4HD cells. In order to explore the existence of  interactions between TNF-a and progestin effects, MPA and TNF-a were added simultaneously to primary culture of  C4HD cells and proliferation was measured. In order to explore the existence of  interactions between TNF-a and progestin effects, primary culture of  C4HD cells were treated with MPA together with TNF-a and proliferation was measured. Although MPA acted as a very potent mitogen in C4HD cells, TNF-a significantly enhanced MPA stimulatory effects. To investigate TNF-a´s ability to increase sensitivity to progestin action in C4HD cells, we determined its effect on  progesterone receptors (PR) expression. TNF-a  treatment of C4HD for 48 h induced a 2-3-fold increase in PR number, as measured by a binding assay with 3H R5020. These results demonstrate that p42/44 MAPK and PI-3K/Akt pathways are involved in TNF-a proliferative effect in C4HD breast tumor cells. We also have provided the first demonstration that TNF-a enhances progestin-mediated proliferation of breast cancer cells through the up-regulation of PR expression.