Ovarian cancer is a highly lethal disease with poor prognosis and especially in high-grade tumor. Emerging evidence has reported that aberrant upregulation and activation of GRB7, ERK as well as FOXM1 are closely associated with aggresivenesss of human cancers. However, the interplay between these factors in the pathogenesis of human cancers still remains unclear. In this study, we found that GRB7 (P<0.0001), ERK phosphorylation (P<0.0001) and FOXM1 (P = 0.001) were frequently increased and associated with high-grade tumors, as well as a high tendency in association with advanced stage ovarian cancer by immunohistochemical analysis. Intriguingly, the expressions of GRB7 (P<0.0001), ERK phosphorylation (P<0.001) and FOXM1 (P<0.001) showed a significant stepwise increase pattern along Grade 1 to Grade 3 ovarian cancers. Biochemical studies using western blot analysis demonstrated that enforced expression or knockdown of GRB7 showed GRB7 could elevate the levels of ERK phosphorylation and FOXM1, whereas enforced expression of FOXM1 could not alter levels of GRB7 and ERK phosphorylation. But inhibition of ERK signaling by U0126 or PD98059 could reduce the level of FOXM1 in GRB7-overexpressing ovarian cancer cells, suggesting that GRB7, ERK and FOXM1 are regulated orderly. Moreover, inhibition of ERK activity by U0126 or PD98059, or decreased FOXM1 expression by Thiostrepton significantly inhibited cell migration/invasion, tumor growth in vitro and in vivo. Collectively, our findings confer that targeting GRB7/ERK/FOXM1 signaling cascade may be a promising molecular therapeutic choice in combating ovarian cancer.
Extracellular Signal-Regulated MAP Kinases/antagonists & inhibitors , Forkhead Transcription Factors/antagonists & inhibitors , GRB7 Adaptor Protein/metabolism , Molecular Targeted Therapy , Ovarian Neoplasms/enzymology , Ovarian Neoplasms/pathology , Signal Transduction , Animals , Cell Line, Tumor , Cell Movement , Cell Proliferation , Extracellular Signal-Regulated MAP Kinases/metabolism , Female , Forkhead Box Protein M1 , Forkhead Transcription Factors/metabolism , Humans , Mice , Mice, Inbred BALB C , Neoplasm Invasiveness , Phosphorylation , Xenograft Model Antitumor Assays
Forkhead box M1 (FOXM1) is a proliferation-associated transcription factor essential for cell cycle progression. Numerous studies have documented that FOXM1 has multiple functions in tumorigenesis and its elevated levels are frequently associated with cancer progression. Here, we characterized the role of ERK/FOXM1 signaling in mediating the metastatic potential of ovarian cancer cells. Immunohistochemical (IHC), immunoblotting and semi-quantitative RT-PCR analyses found that both phospho-ERK and FOXM1 were frequently upregulated in ovarian cancers. Intriguingly, the overexpressed phospho-ERK (p<0.001) and FOXM1 (p<0.001) were significantly correlated to high-grade ovarian tumors with aggressive behavior such as metastasized lymph node (5 out of 6). Moreover, the expressions of phospho-ERK and FOXM1 had significantly positive correlation (p<0.001). Functionally, ectopic expression of FOXM1B remarkably enhanced cell migration/invasion, while FOXM1C not only increased cell proliferation but also promoted cell migration/invasion. Conversely, inhibition of FOXM1 expression by either thiostrepton or U0126 could significantly impair FOXM1 mediated oncogenic capacities. However, the down-regulation of FOXM1 by either thiostrepton or U0126 required the presence of p53 in ovarian cancer cells. Collectively, our data suggest that over-expression of FOXM1 might stem from the constitutively active ERK which confers the metastatic capabilities to ovarian cancer cells. The impairment of metastatic potential of cancer cells by FOXM1 inhibitors underscores its therapeutic value in advanced ovarian tumors.
Cell Movement , Extracellular Signal-Regulated MAP Kinases/metabolism , Forkhead Transcription Factors/metabolism , Signal Transduction , Blotting, Western , Butadienes/pharmacology , Cell Line , Cell Line, Tumor , Cell Proliferation/drug effects , Dose-Response Relationship, Drug , Enzyme Inhibitors/pharmacology , Extracellular Signal-Regulated MAP Kinases/genetics , Female , Forkhead Box Protein M1 , Forkhead Transcription Factors/genetics , Gene Expression Regulation, Neoplastic/drug effects , Humans , Immunohistochemistry , Matrix Metalloproteinase 9/genetics , Matrix Metalloproteinase 9/metabolism , Neoplasm Invasiveness , Nitriles/pharmacology , Ovarian Neoplasms/genetics , Ovarian Neoplasms/metabolism , Ovarian Neoplasms/pathology , Phosphoproteins/genetics , Phosphoproteins/metabolism , Protein Isoforms/genetics , Protein Isoforms/metabolism , Receptors, Urokinase Plasminogen Activator/genetics , Receptors, Urokinase Plasminogen Activator/metabolism , Reverse Transcriptase Polymerase Chain Reaction , Thiostrepton/pharmacology , Tumor Suppressor Protein p53/genetics , Tumor Suppressor Protein p53/metabolism
