2303

FOXC2

The epithelial-mesenchymal transition (EMT) bestows cancer cells with increased stem cell properties and metastatic potential. To date, multiple extracellular stimuli and transcription factors have been shown to regulate EMT. Many of them are not druggable and therefore it is necessary to identify targets, which can be inhibited using small molecules to prevent metastasis. Recently, we identified the ganglioside GD2 as a novel breast cancer stem cell marker. Moreover, we found that GD3 synthase (GD3S)--an enzyme involved in GD2 biosynthesis--is critical for GD2 production and could serve as a potential druggable target for inhibiting tumor initiation and metastasis. Indeed, there is a small molecule known as triptolide that has been shown to inhibit GD3S function. Accordingly, in this manuscript, we demonstrate that the inhibition of GD3S using small hairpin RNA or triptolide compromises the initiation and maintenance of EMT instigated by various signaling pathways, including Snail, Twist and transforming growth factor-beta1 as well as the mesenchymal characteristics of claudin-low breast cancer cell lines (SUM159 and MDA-MB-231). Moreover, GD3S is necessary for wound healing, migration, invasion and stem cell properties in vitro. Most importantly, inhibition of GD3S in vivo prevents metastasis in experimental as well as in spontaneous syngeneic wild-type mouse models. We also demonstrate that the transcription factor FOXC2, a central downstream effector of several EMT pathways, directly regulates GD3S expression by binding to its promoter. In clinical specimens, the expression of GD3S correlates with poor prognosis in triple-negative human breast tumors. Moreover, GD3S expression correlates with activation of the c-Met signaling pathway leading to increased stem cell properties and metastatic competence. Collectively, these findings suggest that the GD3S-c-Met axis could serve as an effective target for the treatment of metastatic breast cancers.

BACKGROUND: FoxC2 is an epithelial-mesenchymal transition (EMT) regulator which induces metastasis. The purpose of this study is to assess the prognostic value of FoxC2 expression in non-small cell lung cancer (NSCLC), alone or in combination with E-cadherin expression. METHODS: A retrospective study was conducted using immunohistochemistry to investigate FoxC2 and E-cadherin expression in a cohort of 309 patients with surgically resected NSCLCs. The prognostic value of FoxC2 and E-cadherin on overall survival (OS) and recurrence-free survival (RFS) was determined by Kaplan-Meier analysis and Cox proportional hazard models. RESULTS: High FoxC2 expression was detected in 26.5% of tumors, and significantly correlated with tobacco use (p = 0.047), adenocarcinoma (p = 0.008) and nodal involvement (p < 0.001). Univariate analysis revealed its association with OS (p = 0.036) and RFS (p = 0.011). By multivariate analysis, high FoxC2 expression lost its significance as an independent predictor of recurrence (p = 0.077), while TNM stage, nodal status and the presence of high FoxC2 and impaired E-cadherin expression retained independent prognostic significance in relation to both OS and RFS. Subset analyses indicated that high FoxC2 expression was significantly associated with disease outcome in node-positive, but not in node-negative patients. CONCLUSION: Evaluation of FoxC2 expression, alone or in combination with E-cadherin expression, may help to stratify NSCLC patients for risk of disease progression, pointing to this EMT regulator as a potential prognostic marker.

Metastatic competence is contingent upon the aberrant activation of a latent embryonic program, known as the epithelial-mesenchymal transition (EMT), which bestows stem cell properties as well as migratory and invasive capabilities upon differentiated tumor cells. We recently identified the transcription factor FOXC2 as a downstream effector of multiple EMT programs, independent of the EMT-inducing stimulus, and as a key player linking EMT, stem cell traits and metastatic competence in breast cancer. As such, FOXC2 could serve as a potential therapeutic target to attenuate metastasis. However, as FOXC2 is a transcription factor, it is difficult to target by conventional means such as small-molecule inhibitors. Herein, we identify the serine/threonine-specific kinase p38 as a druggable upstream regulator of FOXC2 stability and function that elicits phosphorylation of FOXC2 at serine 367 (S367). Using an orthotopic syngeneic mouse tumor model, we make the striking observation that inhibition of p38-FOXC2 signaling selectively attenuates metastasis without impacting primary tumor growth. In this model, circulating tumor cell numbers are significantly reduced in mice treated with the p38 inhibitor SB203580, relative to vehicle-treated counterparts. Accordingly, genetic or pharmacological inhibition of p38 decreases FOXC2 protein levels, reverts the EMT phenotype and compromises stem cell attributes in vitro. We also identify the EMT-regulator ZEB1-known to directly repress E-cadherin/CDH1-as a downstream target of FOXC2, critically dependent on its activation by p38. Consistent with the notion that activation of the p38-FOXC2 signaling axis represents a critical juncture in the acquisition of metastatic competence, the phosphomimetic FOXC2(S367E) mutant is refractory to p38 inhibition both in vitro and in vivo, whereas the non-phosphorylatable FOXC2(S367A) mutant fails to elicit EMT and upregulate ZEB1. Collectively, our data demonstrate that FOXC2 regulates EMT, stem cell traits, ZEB1 expression and metastasis in a p38-dependent manner, and attest to the potential utility of p38 inhibitors as antimetastatic agents.

BACKGROUND/AIMS: Forkhead Box Protein C2 (FOXC2) has been reported to be overexpressed in a variety of human cancers. However, it is unclear whether FOXC2 regulates epithelial-mesenchymal transition (EMT) in CDDP-resistant ovarian cancer cells. The aim of this study is to investigate the effects of FOXC2 on EMT and invasive characteristics of CDDP-resistant ovarian cancer cells and the underlying molecular mechanism. METHODS: MTT, Western blot, scratch wound healing, matrigel transwell invasion, attachment and detachment assays were performed to detect half maximal inhibitory concentration (IC50) of CDDP, expression of EMT-related proteins and invasive characteristics in CDDP-resistant ovarian cancer cell line (SKOV3/CDDP) and its parental cell line (SKOV3). Small hairpin RNA (shRNA) was used to knockdown FOXC2 and analyze the effect of FOXC2 knockdown on EMT and invasive characteristics of SKOV3/CDDP cells. Also, the effect of FOXC2 upregulation on EMT and invasive characteristics of SKOV3 cells was analyzed. Furthermore, the molecular mechanism underlying FOXC2-regulating EMT in ovarian cancer cells was determined. RESULTS: Compared with parental SKOV3 cell line, SKOV3/CDDP showed higher IC50 of CDDP (43.26muM) (P<0.01) and acquired EMT phenotype and invasive characteristics. Gain- and loss-of-function assays indicated that shRNA-mediated FOXC2 knockdown could reverse EMT and reduce the capacity of migration, invasion, attachment and detachment in SKOV3/CDDP cell line and upregulation of FOXC2 could induce the reverse effects in parental SKOV3 cell line. Furthermore, it was found that activation of ERK or AKT/GSK-3beta signaling pathways was involved in FOXC2-promoting EMT in CDDP-resistant ovarian cancer cells. CONCLUSIONS: Taken together, these data demonstrate that FOXC2 may be a promoter of EMT phenotype in CDDP-resistant ovarian cancer cells and a potential therapeutic target for the treatment of advanced ovarian cancer.CI - (c) 2016 The Author(s) Published by S. Karger AG, Basel.

Embryonic development depends on the normal invasion of trophoblast cells. Forkhead box C2 (FOXC2) is a member of Forkhead box family, which is involved in the tumor cells invasion. The aim of this study was to explore the roles of FOXC2 on the invasion of human trophoblast cells, and further study its molecular mechanism. The mRNA and protein levels of FOXC2 in human normal trophoblast and choriocarcinoma cell lines were analyzed by quantitative real-time PCR (qRT-PCR) and Western blot assays, respectively. Methylthiazolyldiphenyl-tetrazo lium bromide (MTT) and transwell assays were separately performed to detect the adhesion and invasion of normal trophoblast cells treated with exogenous FOXC2 and FOXC2 siRNA. QRT-PCR and Western blot assays were used to test levels of the epithelial-mesenchymal transition (EMT)-related and Hedgehog (Hh) signaling pathway-related factors, respectively. Herein, our results found that the expression levels of FOXC2 in normal trophoblast cells were lower than choriocarcinoma cells. FOXC2 over-expression remarkably strengthened the adhesion and invasion abilities of normal trophoblast cells. Moreover, over-expression of FOXC2 significantly promoted the expression of human leukocyte antigen-G (HLA-G), matrix metalloproteinase-2 (MMP-2), Vimentin, sonic hedgehog (Shh), Glioma-associated oncogene homolog 1 (Gli1), and Snail, and inhibited E-cadherin expression. However, it showed the opposite tendency in FOXC2 siRNA group. In addition, there was no significant change in the expression of MMP9 among different groups. Above results illustrated that FOXC2 could promote the invasion ability of normal trophoblast cells by EMT-mediated Hh pathway.CI - (c) 2018 International Federation for Cell Biology.