RELATIONSHIP BETWEEN QUANTITY OF SILVER-STAINED NUCLEOLAR ORGANIZER REGION ASSOCIATED PROTEINS (AG-NORS) AND GROWTH-RATE SUPPRESSION OF BREAST-CANCER CELL-LINES AFTER INTERFERON-GAMMA AND 4-HYDROXY-TAMOXIFEN TREATMENT

The correlation between the silver-stained nucleolar organizer region associated proteins (Ag-NORs) and the growth rate suppression (GRS) of ten established breast cancer cell lines which were treated with 4-hy droxy-tamoxifen (OHT) and interferon-gamma (g-IFN), respectively, was investigated by means of automated image analysis. Previous studies ha ve shown a statistically significant relationship between the Ag-NOR q uantity and the population doubling time (PDT) of these cell clones. T he results of the present study showed a highly significant correlatio n between the GRS and the Ag-NOR quantity in estrogen receptor (ER) po sitive tumour cell lines after OHT treatment (P < 0.001) whereas no st rict correlation of these parameters could be demonstrated after g-IFN treatment in both ER positive and negative cell lines. Our results su ggest a different behaviour of NOR-proteins in breast cancer cell line s if treated either with g-IFN or OHT, probably reflecting the differe nt mechanism of cell suppression mediated by OHT and g-IFN. It is conc luded that quantitative assessment of Ag-NORs is not as suitable for t he determination of the GRS as it is for the determination of cell dup lication rates obtained on untreated tumour cell lines.