Does a truncated form of the transcription factor Ets1 exist in breast cancer cells?

Transcription factor Ets1 cooperates with estrogen receptor α to stimulate estradiol-dependent growth in breast cancer cells and tumors

The purpose of this study was to explore the role of transcription factor Ets1 in estrogen receptor α (ERα)-positive breast cancer progression. We expressed human Ets1 or empty vector in four human ERα-positive breast cancer cell lines and observed increased colony formation. Further examination of cellular responses in stable Ets1-expressing MCF7 clones displayed increased proliferation, migration, and invasion. Ets1-expressing MCF7 tumors grown in the mammary fat pads of nude mice exhibited increased rates of tumor growth (7.36±2.47 mm(3)/day) compared to control MCF7 tumors (2.52±1.70 mm(3)/day), but maintained their dependence on estradiol for tumor growth. Proliferation marker Ki-67 staining was not different between control and Ets1-expressing tumors, but Ets1-expressing tumors exhibited large necrotic centers and elevated apoptotic staining. Ets1 was shown to cooperate with ERα and the p160 nuclear receptor coactivator (NCOA/SRC) family to increase activation of a consensus estrogen response element luciferase reporter construct. Ets1-expressing MCF7 cells also exhibited elevated expression of the ERα target genes, progesterone receptor and trefoil factor 1. Using GST-pulldown assays, Ets1 formed stable complexes containing both ERα and p160 nuclear receptor coactivators. Taken together, these data suggest that the Ets1-dependent estradiol sensitization of breast cancer cells and tumors may be partially due to the ability of Ets1 to cooperate with ERα and nuclear receptor coactivators to stimulate transcriptional activity of estrogen-dependent genes.

Overexpression of ETS-1 is associated with malignant biological features of prostate cancer

E26 transformation-specific-1 (ETS-1), an ETS family transcription factor, has been reported to play an important role in a variety of physiological and pathological processes, but clinical implications of ETS-1 expression in prostate cancer (PCa), particularly high-risk cases, including response to androgen-deprivation therapy (ADT) have yet to be elucidated. We examined the expression of ETS-1 using immunohistochemical staining of paraffin-embedded prostate carcinoma tissue obtained by needle biopsy from 69 mostly advanced PCa patients. ETS-1 expression was compared with the clinicopathological characteristics of the 69 patients, including 25 who underwent ADT as a primary treatment. As a result, PCa patients with higher expression of ETS-1 were significantly more likely to be of high stage and high Gleason score (P<0.05). There was no significant association between ETS-1 expression and the initial prostate-specific antigen (PSA) level. In the 25 patients treated by ADT, the staining score for ETS-1 was significantly associated with rapid development of castration-resistant disease within 24 months (P<0.05), whereas the Gleason score and PSA level were not. In conclusion, increased ETS-1 expression was associated with a higher stage, higher Gleason score and shorter time to castration-resistant progression. These data suggest that immunostaining for ETS-1 could be a molecular marker for predicting a poor clinical outcome for PCa patients, particularly those with high-risk disease.