Studies on human alpha-lactalbumin: radioimmunoassay measurements in normal human breast and breast cancer.

A sensitive and specific radioimmunoassay for human alpha-lactalbumin, a milk protein, has been developed in order to examine the effect of prolactin on the human breast in normal and diseased states. Samples of milk from nursing mothers and from men and women with galactorrhea were found to contain milligram concentrations of this protein. In serum, 8 of 25 normal men and 18 of 44 normal women had detectable concentrations of alpha-lactalbumin. Significantly higher levels of alpha-lactalbumin were found in 17 of 19 women during pregnancy who were not actively lactating. All nursing mothers were found to have distinctly elevated serum alpha-lactalbumin concentrations. In a group of 17 female patients with phenothiazine induced prolactin elevations (mean 29.4 ng/ml), the mean serum alpha-lactalbumin of 17.3 ng/ml was significantly higher than in normal female volunteers. Patients with gynecomastia were not noted to have elevated alpha-lactalbumin. In vitro, homogenates of normal breast and carcinoma tissue from the same individuals revealed that in 9 of 17 patients alpha-lactalbumin was present in higher concentrations in normal than in cancerous tissue. Overall, alpha-lactalbumin was found in 48.5% of homogenates and 41% of organ cultures of normal breast tissue from cancer patients. In contrast, it was present in only 19% of homogenates and 21% of cultures of carcinoma tissue, indicating that the cancer tissue may lose its ability to produce alpha-lactalbumin. Differences in biologic behavior were found in some tumors. In 2 cases homogenates of breast cancer tissue had much higher concentrations of alpha-lactalbumin than the normal tissue, and in 3 of 33 tumors studied in organ culture prolactin increased alpha-lactalbumin output.