WNT4 mediates estrogen receptor signaling and endocrine resistance in invasive lobular carcinoma cell lines

Abstract

BackgroundInvasive lobular carcinoma (ILC) of the breast typically presents with clinical biomarkers consistent with a favorable response to endocrine therapies, and over 90 % of ILC cases express the estrogen receptor (ER). However, a subset of ILC cases may be resistant to endocrine therapies, suggesting that ER biology is unique in ILC. Using ILC cell lines, we previously demonstrated that ER regulates a distinct gene expression program in ILC cells, and we hypothesized that these ER-driven pathways modulate the endocrine response in ILC. One potential novel pathway is via the Wnt ligand WNT4, a critical signaling molecule in mammary gland development regulated by the progesterone receptor.MethodsThe ILC cell lines MDA-MB-134-VI, SUM44PE, and BCK4 were used to assess WNT4 gene expression and regulation, as well as the role of WNT4 in estrogen-regulated proliferation. To assess these mechanisms in the context of endocrine resistance, we developed novel ILC endocrine-resistant long-term estrogen-deprived (ILC-LTED) models. ILC and ILC-LTED cell lines were used to identify upstream regulators and downstream signaling effectors of WNT4 signaling.ResultsILC cells co-opted WNT4 signaling by placing it under direct ER control. We observed that ER regulation of WNT4 correlated with use of an ER binding site at the WNT4 locus, specifically in ILC cells. Further, WNT4 was required for endocrine response in ILC cells, as WNT4 knockdown blocked estrogen-induced proliferation. ILC-LTED cells remained dependent on WNT4 for proliferation, by either maintaining ER function and WNT4 regulation or uncoupling WNT4 from ER and upregulating WNT4 expression. In the latter case, WNT4 expression was driven by activated nuclear factor kappa-B signaling in ILC-LTED cells. In ILC and ILC-LTED cells, WNT4 led to suppression of CDKN1A/p21, which is critical for ILC cell proliferation. CDKN1A knockdown partially reversed the effects of WNT4 knockdown.ConclusionsWNT4 drives a novel signaling pathway in ILC cells, with a critical role in estrogen-induced growth that may also mediate endocrine resistance. WNT4 signaling may represent a novel target to modulate endocrine response specifically for patients with ILC.Electronic supplementary materialThe online version of this article (doi:10.1186/s13058-016-0748-7) contains supplementary material, which is available to authorized users.

Decreased Wnt4 expression inhibits thymoma development through downregulation of FoxN1

“…Weissferdt characterized FoxN1 protein expression in 65 cases of thymic carcinoma and obtained similar results, with the rate of FoxN1 positivity being 68% (13). Wnt4 has also been reported to play a role in the pathogenesis of breast cancer and hepatocellular carcinoma (14,15), but its expression in thymoma has seldom been reported.…”

Estrogen controls mTOR signaling and mitochondrial function via WNT4 in lobular carcinoma cells

“…WNT4overexpressing models were previously described [16], and cultured in the same conditions as parental cell lines. Long-term estrogen deprived (LTED) model establishment and culture conditions were previously described [15]. All lines were incubated at 37°C in 5% CO 2 .…”

“…These unique targets mediate ILC-specific signaling pathways driven by ER that are critical for endocrine response and resistance, eg. estrogen-driven atypical Wnt signaling via WNT4 [15,16]. However, our understanding of ER-driven signaling at the protein level in ILC cells remains limited, as studies to date either cannot define dynamic changes caused by ER activation (ie.…”

“…In the normal mammary gland, WNT4 is induced by progesterone in progesterone receptor (PR)-positive luminal epithelial cells, then secreted to act in a paracrine manner to activate canonical β-catenin-dependent signaling in neighboring myoepithelial cells [17][18][19][20]. In contrast, WNT4 is under direct control of ER, not PR, in ILC cell lines [13,15].…”

“…Canonical Wnt signaling is also dysfunctional in ILC cells; hallmark genetic loss of E-cadherin (CDH1) causes catenin protein dysfunction including destabilization and loss of β-catenin protein in both cell lines and tumors [4,15]. Further, we recently reported that WNT4 secreted from ILC cells (and other cancer models) is dysfunctional for paracrine activity, but instead activates signaling by a cellautonomous, intracellular mechanism (ie.…”