We analyzed molecular data on 2,579 tumors from The Cancer Genome Atlas (TCGA) of four gynecological types plus breast. Our aims were to identify shared and unique molecular features, clinically significant subtypes, and potential therapeutic targets. We found 61 somatic copy-number alterations (SCNAs) and 46 significantly mutated genes (SMGs). Eleven SCNAs and 11 SMGs had not been identified in previous TCGA studies of the individual tumor types. We found functionally significant estrogen receptor-regulated long non-coding RNAs (lncRNAs) and gene/lncRNA interaction networks. Pathway analysis identified subtypes with high leukocyte infiltration, raising potential implications for immunotherapy. Using 16 key molecular features, we identified five prognostic subtypes and developed a decision tree that classified patients into the subtypes based on just six features that are assessable in clinical laboratories.

The discovery of oestrogen receptor β (ERβ/ESR2) was a landmark discovery. Its reported expression and homology with breast cancer pharmacological target ERα (ESR1) raised hopes for improved endocrine therapies. After 20 years of intense research, this has not materialized. We here perform a rigorous validation of 13 anti-ERβ antibodies, using well-characterized controls and a panel of validation methods. We conclude that only one antibody, the rarely used monoclonal PPZ0506, specifically targets ERβ in immunohistochemistry. Applying this antibody for protein expression profiling in 44 normal and 21 malignant human tissues, we detect ERβ protein in testis, ovary, lymphoid cells, granulosa cell tumours, and a subset of malignant melanoma and thyroid cancers. We do not find evidence of expression in normal or cancerous human breast. This expression pattern aligns well with RNA-seq data, but contradicts a multitude of studies. Our study highlights how inadequately validated antibodies can lead an exciting field astray.

Estrogen receptor β (ERβ) is the predominant ER in the colorectal epithelium. Compared with normal colon tissue, ERβ expression is reduced in colorectal cancer. Our hypothesis is that ERβ inhibits proliferation of colon cancer cells. Hence, the aim of this study has been to investigate the molecular function of ERβ in colon cancer cells, focusing on cell cycle regulation. SW480 colon cancer cells have been lentivirus transduced with ERβ expression construct with or without mutated DNA-binding domain or an empty control vector. Expression of ERβ resulted in inhibition of proliferation and G₁ phase cell cycle arrest and this effect was dependent on a functional DNA-binding region. c-Myc is overexpressed in an overwhelming majority of colorectal tumors. By Western blot and real-time PCR, we found c-Myc to be down-regulated in the ERβ-expressing cells. Furthermore, the c-Myc target gene p21^(Waf1/Cip1) was induced and Cdc25A was reduced by ERβ at the transcriptional level. The second cdk2-inhibitor, p27^Kip1, was induced by ERβ, but this regulation occurred at the posttranscriptional level, probably through ERβ-mediated repression of the F-box protein p45^Skp2. Expression of the ERβ-variant with mutated DNA binding domain resulted in completely different cell cycle gene regulation. We performed in vivo studies with SW480 cells ± ERβ transplanted into severe combined immunodeficient/beige mice; after three weeks of ERβ-expression, a 70% reduction of tumor volume was seen. Our results show that ERβ inhibits proliferation as well as colon cancer xenograft growth, probably as a consequence of ERβ-mediated inhibition of cell-cycle pathways. Furthermore, this ERβ-mediated cell cycle repression is dependent on functional ERE binding. [Cancer Res 2009;69(15):6100–6]