NUCLEAR ESTROGEN-RECEPTOR AND NONHISTONE CHROMOSOMAL-PROTEINS IN HORMONAL INDEPENDENCY OF MURINE BREAST CANCERS

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  • 1 January 1984
    • journal article
    • research article
    • Vol. 44  (9) , 4118-4123
Abstract
The capability of nuclear binding of cytosol estrogen receptors (ERc) was studied in GR mouse mammary tumors during their alteration of hormonal dependency through serial transplantations. Nuclei from GR mouse mammary tumors were incubated with uterine cytosol receptor complexes labeled with 125I-estradiol and the amount of receptor binding in the 0.4 M KCI nuclear extracts was determined. The originally ERc-positive-hormone-dependent (type I) tumors were capable of nuclear receptor binding, while this function was markedly reduced in the evolved hormone-independent (type II) tumors, although the ERc content in the latter was still positive. The originally hormone-independent (ERc-negative, type III) tumors, however, retained the nuclear binding capability. The hormonal independency in type III tumors appears to be due to a lack of ER, while in type II tumors it may be attributed to the loss of nuclear binding capability for receptor complexes. Nonhistone chromosomal proteins (NHCP) were analyzed by the 2-dimensional gel electrophoretic technique. A MW NHCP was present in 11 of 12 type I and 4 of 4 type III tumors. Following serial transplantation of the type I tumors, this NHCP was either markedly diminished or not observed in all 14 type II tumors examined. Although it coincides with the capability of nuclear receptor binding, the biological function of this NHCP is still undefined and warrants further investigation.