Characterization of HCI-EC-23 a novel estrogen- and progesterone-responsive endometrial cancer cell line.

Most endometrial cancers express the hormone receptor estrogen receptor alpha (ER) and are driven by excess estrogen signaling. However, evaluation of the estrogen response in endometrial cancer cells has been limited by the availability of hormonally responsive in vitro models, with one cell line, Ishikawa, being used in most studies. Here, we describe a novel, adherent endometrioid endometrial cancer (EEC) cell line model, HCI-EC-23. We show that HCI-EC-23 retains ER expression and that ER functionally responds to estrogen induction over a range of passages. We also demonstrate that this cell line retains paradoxical activation of ER by tamoxifen, which is also observed in Ishikawa and is consistent with clinical data. The mutational landscape shows that HCI-EC-23 is mutated at many of the commonly altered genes in EEC, has relatively few copy-number alterations, and is microsatellite instable high (MSI-high). In vitro proliferation of HCI-EC-23 is strongly reduced upon combination estrogen and progesterone treatment. HCI-EC-23 exhibits strong estrogen dependence for tumor growth in vivo and tumor size is reduced by combination estrogen and progesterone treatment. Molecular characterization of estrogen induction in HCI-EC-23 revealed hundreds of estrogen-responsive genes that significantly overlapped with those regulated in Ishikawa. Analysis of ER genome binding identified similar patterns in HCI-EC-23 and Ishikawa, although ER exhibited more bound sites in Ishikawa. This study demonstrates that HCI-EC-23 is an estrogen- and progesterone-responsive cell line model that can be used to study the hormonal aspects of endometrial cancer.

Are the curli proteins CsgE and CsgF intrinsically disordered?

Curli are a type of proteinaceous cell surface filament produced by enteric bacteria such as Escherichia and Salmonella that facilitate cell adhesion and invasion, bio-film formation, and environmental persistence. Curli assembly involves 6 proteins encoded by the curli specific genes A, B, C, E, F, and G. Although CsgA is the major structural component of curli, CsgE, and CsgF, are thought to play important chaperone like functions in the assembly of CsgA into curli. Given that some proteins with chaperone like function have been observed to contain disordered regions, sequence analysis and circular dichroism spectroscopy was used to investigate the possibility that structures of CsgE and CsgF were also disordered. Sequence analysis based on charge and hydrophobicity, as well as using the disorder prediction software PONDR, indicates that both proteins have significant regions of disorder. The secondary structure and unfolding, of CsgE and CsgF, analyzed using circular dichroism spectroscopy suggests that both proteins lack a well defined and stable structure. These observations support the hypothesis that the curli assembly proteins CsgE and CsgF are disordered proteins containing intrinsically disordered regions.