You will be shown an abstract from a biomedical research paper. Given this abstract, your task is to extract all unique entities of the following types: ["Chemical"].

Please return the output as a JSON object of the format: {"Chemical": ["Arsenic", ...]}. The keys should be entity types and values should be lists of extracted entities belonging to the corresponding type. If you cannot find entities belonging to a specific type, the value should be [].

Only output the JSON object and do not include any additional text.

Abstract:

Differential gene expression in ERα-positive and ERα-negative breast cancer cells upon leptin stimulation. In postmenopausal women, adipositas represents a serious risk factor for cancer development and progression. White adipose tissue secretes the 16 kDa hormone leptin which plays a key role in the regulation of appetite and metabolism. An increasing number of reports indicate that leptin also interferes with signal transduction pathways implicated in the development of breast cancer. In our previous study, we identified the estrogen receptor alpha (ERα) as a relevant enhancer of leptin-induced signal transduction leading to transactivation of signal transducer and activator of transcription 3 (Stat3). The purpose of this study is the investigation of specific target gene expression in response to leptin-mediated Stat3 signaling. We performed a comprehensive microarray analysis of ERα-positive and ERα-negative MDA-MB-231 cells upon leptin treatment and identified 49 genes which showed a significant ERα-dependent regulation in leptin-treated MDA-MB-231 cells. There was no intersection with genes which were merely up- or downregulated by ERα expression and only 9 and 11 genes overlapping targets which were regulated by leptin stimulation either in ERα-expressing or ERα-negative MDA-MB-231 cells, respectively. To demonstrate the specificity, expression of three target genes was validated by quantitative real-time PCR. In conclusion, these data imply that leptin can induce a different set of target genes dependent on ERα expression, which might contribute to the development and progression of cancer diseases.
{"Chemical": ["estrogen"]}