The binding capacities of estrogen receptors in nuclear matrix

nuclei and cytosol of human breast cancer tissue （EmR

EnR

EcR） were estimated with radioligand binding assay of receptors.The average Bmax values of these components in 21 breast cancer specimens are 417.54±170.95

147.75±98.32

7.34±5.33 fmol/mg protein

andthose in 10 normal breast tissue specimens are 42.33±8.49

25.05±7.81

5.91±2.28 fmol/mg protein. Comparing the cancer and normal breast tissues

there is significant difference in Bmax values of EmR and EnR（P<0.01）

and no difference in Bmax values of EcR （P>0.10）. The EmR/EnR value of 21 breast cancer tissue is 0.65±0.10

and that of 10 normal breast tissue is 0.42±0.04. There is statistical difference between the cancer and normal. 10 of 13（77%） patients

who are EcR-positive

have higher EmR/EnR values （≥0.50）. The results suggest that estrogen receptors are mainly located at the nuclear matrix

ER levels in nucleus

especially in nuclear matrix of breast cancer tissue are valuable parameters and may be useful for predicting whetner the patient will be responsible to endocrine therapy.