{'fraction_non_alphanumeric': 0.0296220633299285, 'fraction_numerical': 0.018386108273748723, 'mean_word_length': 4.764705882352941, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Selective regulation of steroid receptor expression in MCF-7 breast cancer cells by a novel member of the heregulin family.

A 52 kDa heregulin secreted by estrogen receptor (ER)-negative human breast cancer cells induced rapid growth of ER-positive MCF-7 breast cancer cells with a stimulatory effect observed at 10(-11)M. This heregulin down-regulated the message for ER in MCF-7 cells within 24 hours after stimulation. Similarly the ER protein was down-regulated within 24 to 48 hours after stimulation of cells. However, this down-regulation occurred without activation of the ER, since the progesterone receptor (PR) level of cells stimulated with the 52 kDa heregulin did not increase over the time period measured. As a control, estradiol down-regulated and activated ER as shown by a pronounced increase in PR content of MCF-7 cells. This finding indicates an important role of this heregulin in the down-regulation of ER in estrogen-dependent human breast cancer cells.