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  • β-catenin knockdown promotes NHERF1-mediated survival of colorectal cancer cells: implications for a double-targeted therapy.

β-catenin knockdown promotes NHERF1-mediated survival of colorectal cancer cells: implications for a double-targeted therapy.

Oncogene (2018-03-20)
Concetta Saponaro, Sara Sergio, Antonio Coluccia, Maria De Luca, Giuseppe La Regina, Luca Mologni, Valeria Famiglini, Valentina Naccarato, Daniela Bonetti, Candice Gautier, Stefano Gianni, Daniele Vergara, Michel Salzet, Isabelle Fournier, Cecilia Bucci, Romano Silvestri, Carlo Gambacorti Passerini, Michele Maffia, Addolorata Maria Luce Coluccia
要旨

Nuclear activated β-catenin plays a causative role in colorectal cancers (CRC) but remains an elusive therapeutic target. Using human CRC cells harboring different Wnt/β-catenin pathway mutations in APC/KRAS or β-catenin/KRAS genes, and both genetic and pharmacological knockdown approaches, we show that oncogenic β-catenin signaling negatively regulates the expression of NHERF1 (Na+/H+ exchanger 3 regulating factor 1), a PDZ-adaptor protein that is usually lost or downregulated in early dysplastic adenomas to exacerbate nuclear β-catenin activity. Chromatin immunoprecipitation (ChIP) assays demonstrated that β-catenin represses NHERF1 via TCF4 directly, while the association between TCF1 and the Nherf1 promoter increased upon β-catenin knockdown. To note, the occurrence of a cytostatic survival response in settings of single β-catenin-depleted CRC cells was abrogated by combining NHERF1 inhibition via small hairpin RNA (shRNA) or RS5517, a novel PDZ1-domain ligand of NHERF1 that prevented its ectopic nuclear entry. Mechanistically, dual NHERF1/β-catenin targeting promoted an autophagy-to-apoptosis switch consistent with the activation of Caspase-3, the cleavage of PARP and reduced levels of phospho-ERK1/2, Beclin-1, and Rab7 autophagic proteins compared with β-catenin knockdown alone. Collectively, our data unveil novel β-catenin/TCF-dependent mechanisms of CRC carcinogenesis, also offering preclinical proof of concept for combining β-catenin and NHERF1 pharmacological inhibitors as a mechanism-based strategy to augment apoptotic death of CRC cells refractory to current Wnt/β-catenin-targeted therapeutics.

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Sigma-Aldrich
ChIPAb+ TCF-4 - ChIP Validated Antibody and Primer Set, from mouse