Eya2 is required to mediate the pro-metastatic functions of Six1 via the induction of TGF-β signaling, epithelial–mesenchymal transition, and cancer stem cell properties

Abstract

Six1 is a critical regulator of embryonic development that requires interaction with the Eya family of proteins (Eya1-4) to activate the transcription of genes involved in neurogenesis, myogenesis, and nephrogenesis. While expression of Six1 and Eya family members is predominantly observed in development, their overexpression is observed in numerous cancers. Importantly, both Six1 and Eya have independently been shown to mediate breast cancer metastasis, but whether they functionally interact during tumor progression has not been explored. Herein we demonstrate that knockdown of Eya2 in MCF7 mammary carcinoma cells reverses the ability of Six1 to induce TGF-β signaling, as well as to induce characteristics associated with epithelial-mesenchymal transition (EMT) and cancer stem cells (CSCs), suggesting that Six1 is dependent on Eya2 to mediate numerous pro-metastatic characteristics. The importance of the Six1/Eya interaction in human breast cancer is underscored by the finding that high levels of Six1 correlate with shortened time to relapse and metastasis as well as decreased survival only when co-expressed with high levels of Eya2. Overall, these data implicate Eya2 as a necessary cofactor for many of the metastasis promoting functions of Six1, suggesting that targeting the Six1/Eya interaction may inhibit breast cancer progression. Since Six1 and Eya2 are not highly expressed in most adult tissues, the Six1-Eya interaction may be a valuable future therapeutic target whose inhibition would be expected to impair breast cancer progression while conferring limited side effects.

A phosphotyrosine switch determines the antitumor activity of ERβ

“…Next, we sought to validate the relevance of EYA2 and c-ABL to the antitumor activity of ERβ. Consistent with the previous reports of the oncogenic activity of EYA2 (22,23) in breast cancer, ectopic expression of EYA2 promoted breast cancer cell growth in vitro and in vivo (Supplemental Figure 6, C and D). Using the same systems, we found that knockdown of c-ABL led to accelerated tumor cell growth (Supplemental Figure 6, E and F).…”

“…The phosphatase activity of EYA is important for its roles in transcriptional regulation (14,16), cytoplasmic signaling (17), innate immune response (18), and DNA damage-induced apoptosis (19,20). The oncogenic activity of EYA proteins has been demonstrated in ovarian (21) and breast cancers (22,23). In particular, EYA2 was shown to promote proliferation, migration, and invasion of breast cancer cells, but its direct target(s) in tumor promotion is unclear.…”

Upregulation of Notch2 and Six1 Is Associated with Progression of Early-Stage Lung Adenocarcinoma and a More Aggressive Phenotype at Advanced Stages

“…Six1 is a homeodomain transcription factor (37) and a putative downstream target of Notch2 (24,25). Interestingly, Ford and colleagues showed that Six1 stimulates the malignant transformation of mammary epithelial cells through transactivating cyclin A1 (38,39) and induces EMT in mammary cancer cells through the induction of TGF-b signaling (27,40). These findings suggested that Notch2 and Six1 play coordinate roles during the early-stage lung adenocarcinoma progression.…”

The Canonical Wnt Signal Restricts the Glycogen Synthase Kinase 3/Fbw7-Dependent Ubiquitination and Degradation of Eya1 Phosphatase

“…A further reduction to 38% results in renal hypoplasia, and 14% of the normal Eya1 level is incompatible with kidney formation in mouse mutants (14). On the other hand, abnormally high levels of human EYA1 are linked to breast cancer progression and poor prognosis (7). These observations suggest that cell typespecific Eya1 function may in part depend on its protein levels.…”