Expression of p43 associated placental isoferritin (PLF) correlates inversely with cell growth in breast cancer cells lines MCF-7 and T47-D

We have previously demonstrated that the expression of the recently described immunosuppressive antigen p43 in breast cancer patients correlates with early stages of the disease and a low degree of proliferation of the tumor. Attempts were made to evaluate the expression of p43 in two breast cancer cell lines (MCF-7 and T47-D) stimulated to proliferation by 17-beta estradiol and fetal bovine serum (FBS). p43 expression was determined by RIA technique using the new monoclonal antibody CM-H-9, the rate of proliferation was was assessed by [3H]thymidine incorporation during 72 hours of incubation. Induction of proliferation by addition of 17-beta-estradiol and FBS to serum-free tissue culture medium correlated with a decrease of p43 synthesis of both cell lines. The level of p43 expression in non-stimulated cells was low in comparison to that in cells cultivated routinely (15% FBS, no estrogen). However, the drop of p43 was significantly stronger in cell lines with estrogen stimulated proliferation. Our in vitro results confirmed previous clinical observations describing an inverse correlation between p43 synthesis and degree of proliferation and differentiation in breast cancer for the first time. However, the pathologic mechanisms leading to this phenomenon need to be elucidated. (author)