Defining Anti-Tumorigenic and Anti-Inflammatory Effects Mediated By Estrogen Receptor Beta In Colon Epithelial Cells

Despite its slow development and our capacity for early detection using endoscopy, colorectal cancer remains the second leading cause of cancer death in the United States. Epidemiological studies indicate a role for estrogen in protecting against colorectal cancer. Estrogen receptor β (ERβ) has been found to be the main ER in the colon. Cell line studies have implicated that ERβ has anti-tumorigenic and anti-proliferative effects on colon cancer cells lines while human epidemiological data suggest that polymorphisms in the ERβ gene are associated with greater cancer risk and lower survival.

Overexpression of ERβ changes the miRnome. Here we show that ERβ can alleviate the progression of colon cancer by inhibiting proliferation through decreasing MYC transcription and therefore decreasing levels of miR-17-92 (OncomiR-1). This is reflected in a decrease in cell number, decrease in migration, and increase in apoptosis. Furthermore, addition of miR-17 using miRNA mimics reverses the effects of ERβ. This demonstrates that ERβ influences not only the transcriptome, but also the miRnome and that the miRnome can be potential targets for novel treatment approaches.

ERβ upregulates miR-205 and downregulates PROX1. This study uncovers the pathway in which ERβ downregulates the transcription factor PROX1 by upregulating miR-205 directly. MiR-205 then targets PROX1 mRNA for degradation. This results in the cells adopting a more adhesive phenotype and reduces the metastatic potential. This study uncovers the potential for ERβ to be anti-metastatic in addition to being anti-proliferative and anti-inflammatory.

ERβ modulates the NFkB inflammatory cascade. One of ERβ’s attributes is that it has anti-inflammatory capabilities. Using a whole genome approach, this study reveals that ERβ can modulate the NFkB inflammatory network. In SW480 cells, ERβ downregulates NFkB transcription factors and induces apoptosis. In HT29 cells, ERβ prevents p65 subunit of NFkB from translocating to the nucleus. Overall, ERβ attenuates the NFkB signaling cascade by attenuating genes related to inflammation while enhancing genes related to apoptosis and cellular defenses. This makes ERβ a useful target for anti-inflammatory drug treatments for patients suffering from chronic inflammatory diseases.