EXPRESSION OF P43 ASSOCIATED PLACENTAL ISOFERRITIN (PLF) CORRELATES INVERSELY WITH CELL-GROWTH IN BREAST-CANCER CELL-LINES MCF-7 AND T47-D

We have previously demonstrated that the expression of the recently de scribed immunosuppressive antigen p43 in breast cancer patients correl ates with early stages of the disease and a low degree of proliferatio n of the tumors. Attempts were made to evaluate the expression of p43 in two breast cancer cell lines (MCF-7 and T47-D) stimulated to prolif eration by 17-beta estradiol and fetal bovine serum (FBS). p43 express ion was determined by RIA technique using the new monoclonal antibody CM-H-9, the rate of proliferation was assessed by [H-3]thymidine Incor poration during 72 hours Of incubation. Induction of proliferation by addition of 17-beta estradiol and FBS to serum-free tissue culture med ium correlated with a decrease of p43 synthesis in both cell lines. Th e level of p43 expression in nonstimulated cells was low in comparison to that in cells cultivated routinely (15% FBS, no estrogen). However , the drop of p43 synthesis was significantly stronger in cell lines w ith estrogen stimulated proliferation. Our In vitro results confirmed previous clinical observations describing an inverse correlation betwe en p43 synthesis and degree of proliferation and differentiation in br east cancer for the first time. However, the pathologic mechanisms lea ding to this phenomenon need to be elucidated.