RESUMO
The protein tyrosine kinase Ephrin type-B receptor 3 (EPHB3) counteracts tumor-cell dissemination by regulating intercellular adhesion and repulsion and acts as tumor/invasion suppressor in colorectal cancer. This protective mechanism frequently collapses at the adenoma-carcinoma transition due to EPHB3 transcriptional silencing. Here, we identify a transcriptional enhancer at the EPHB3 gene that integrates input from the intestinal stem-cell regulator achaete-scute family basic helix-loop-helix transcription factor 2 (ASCL2), Wnt/ß-catenin, MAP kinase, and Notch signaling. EPHB3 enhancer activity is highly variable in colorectal carcinoma cells and precisely reflects EPHB3 expression states, suggesting that enhancer dysfunction underlies EPHB3 silencing. Interestingly, low Notch activity parallels reduced EPHB3 expression in colorectal carcinoma cell lines and poorly differentiated tumor-tissue specimens. Restoring Notch activity reestablished enhancer function and EPHB3 expression. Although essential for intestinal stem-cell maintenance and adenoma formation, Notch activity seems dispensable in colorectal carcinomas. Notch activation even promoted growth arrest and apoptosis of colorectal carcinoma cells, attenuated their self-renewal capacity in vitro, and blocked tumor growth in vivo. Higher levels of Notch activity also correlated with longer disease-free survival of colorectal cancer patients. In summary, our results uncover enhancer decommissioning as a mechanism for transcriptional silencing of the EPHB3 tumor suppressor and argue for an antitumorigenic function of Notch signaling in advanced colorectal cancer.
Assuntos
Neoplasias Colorretais/genética , Elementos Facilitadores Genéticos/genética , Inativação Gênica , Receptor EphB3/genética , Transcrição Gênica , Animais , Apoptose/genética , Fatores de Transcrição Hélice-Alça-Hélice Básicos/metabolismo , Pontos de Checagem do Ciclo Celular/genética , Diferenciação Celular/genética , Neoplasias Colorretais/enzimologia , Neoplasias Colorretais/patologia , Regulação Neoplásica da Expressão Gênica , Células HT29 , Humanos , Sistema de Sinalização das MAP Quinases/genética , Camundongos , Células-Tronco Neoplásicas/metabolismo , Células-Tronco Neoplásicas/patologia , Receptor EphB3/metabolismo , Receptores Notch/metabolismo , Transdução de Sinais/genética , Proteínas Wnt/metabolismo , beta Catenina/metabolismoRESUMO
Metastatic ovarian cancer has a dismal prognosis and current chemotherapeutic approaches have very limited success. Metadherin (MTDH) is expressed in human ovarian cancer tissue and its expression inversely correlates with patients overall survival. Consistent with these studies, we observed MTDH expression in tissue specimens of FIGO Stage III ovarian carcinomas (72/83 cases). However, we also observed this in normal human ovarian epithelial (OE) cells, which raised the question of whether MTDH-variants with functional differences exist. We identified a novel MTDH exon 11 skipping variant (MTDHdel) which was seen at higher levels in ovarian cancer compared to benign OE cells. We analyzed MTDH-binding partner interactions and found that 12 members of the small ribosomal subunit and several mRNA binding proteins bound stronger to MTDHdel than to wildtype MTDH which indicates differential effects on gene translation. Knockdown of MTDH in ovarian cancer cells reduced the amount of distant metastases and improved the survival of ovarian cancer-bearing mice. Selective overexpression of the MTDHdel enhanced murine and human ovarian cancer progression and caused a malignant phenotype in originally benign human OE cells. MTDHdel was detectable in microdissected ovarian cancer cells of some human tissue specimens of ovarian carcinomas. In summary, we have identified a novel MTDH exon 11 skipping variant that shows enhanced binding to small ribosomal subunit members and that caused reduced overall survival of ovarian cancer bearing mice. Based on the findings in the murine system and in human tissues, MTDHdel must be considered a major promalignant factor for ovarian cancer.
Assuntos
Moléculas de Adesão Celular/genética , Proteínas de Membrana/genética , Neoplasias Ovarianas/genética , Neoplasias Ovarianas/patologia , Deleção de Sequência , Animais , Moléculas de Adesão Celular/metabolismo , Linhagem Celular Tumoral , Éxons , Feminino , Técnicas de Silenciamento de Genes , Humanos , Proteínas de Membrana/metabolismo , Camundongos , Camundongos Endogâmicos C57BL , Metástase Neoplásica , Transplante de Neoplasias , Proteínas de Ligação a RNARESUMO
Traditional treatments for breast cancer fail to address therapy-resistant cancer stem-like cells that have been characterized by changes in epigenetic regulators such as the lysine demethylase KDM4. Here, we describe an orally available, selective and potent KDM4 inhibitor (QC6352) with unique preclinical characteristics. To assess the antitumor properties of QC6352, we established a method to isolate and propagate breast cancer stem-like cells (BCSC) from individual triple-negative tumors resected from patients after neoadjuvant chemotherapy. Limiting-dilution orthotopic xenografts of these BCSCs regenerated original patient tumor histology and gene expression. QC6352 blocked BCSC proliferation, sphere formation, and xenograft tumor formation. QC6352 also abrogated expression of EGFR, which drives the growth of therapy-resistant triple-negative breast cancer cells. Our findings validate a unique BCSC culture system for drug screening and offer preclinical proof of concept for KDM4 inhibition as a new strategy to treat triple-negative breast cancer. Cancer Res; 77(21); 5900-12. ©2017 AACR.