Lactate dehydrogenase in estrogen-responsive human breast cancer cells.

Lactate dehydrogenase activity (LDH) was measured in the MCF-7 human breast cancer cell line derived at the Michigan Cancer Foundation from a patient with metastatic breast adenocarcinoma. LDH was found in the 46,000 X g supernatant of cell lysates, but not in the culture medium. Only the fifth isozyme (LDH-5) could be demonstrated by cellulose acetate electrophoresis and relative heat inactivation studies. When endogenous steroids were removed from the medium, addition of estrogen to the growth medium for several days elevated LDH 2-fold above controls; LDH was not altered when MCF-7 cells were treated with progesterone, hydrocortisone, prolactin, insulin, or triiodothyronine. A physiological concentration (0.1 nM) of 17beta-estradiol was sufficient to produce a maximal LDH increase. There were no qualitative isozyme changes in response to estrogen. LDH activity may therefore be a useful marker protein for studying hormone action in the MCF-7 human breast cancer cell line.