J. Holm et al., FOLATE RECEPTOR OF HUMAN MAMMARY ADENOCARCINOMA, APMIS. Acta pathologica, microbiologica et immunologica Scandinavica, 102(6), 1994, pp. 413-419
Binding of H-3-folate to human mammary tumor homogenate was of a high-
affinity type (K=10(10) M(-1)) and displayed apparent positive coopera
tivity. Radioligand dissociation was slow at pH 7.4, but rapid at pH 3
.5. As compared to methotrexate, 5-formyltetrahydrofolate acted as a s
trong inhibitor of radioligand binding. Gel chromatography of radiolig
and-labeled homogenate of tumor tissue revealed three peaks: a small g
reater than or equal to 110 kDa peak and two major peaks of folate-bin
ding activity (M(r) similar to 25 kDa and M(r) similar to 100 kDa). Ma
mmary tumor tissue showed immunostaining with rabbit antibodies agains
t human milk folate binder. A parallel elevation in the concentrations
of folate-binding protein and triglyceride in tumor tissue as compare
d to normal tissue adjacent to the tumor was compatible with the local
ization of folate-binding protein in the triglyceride-rich fraction of
mammary gland homogenate.