Pan-cancer transcriptional signatures predictive of oncogenic mutations reveal that Fbw7 regulates cancer cell oxidative metabolism.

The Fbw7 (F-box/WD repeat-containing protein 7) ubiquitin ligase targets multiple oncoproteins for degradation and is commonly mutated in cancers. Like other pleiotropic tumor suppressors, Fbw7's complex biology has impeded our understanding of how Fbw7 mutations promote tumorigenesis and hindered the development of targeted therapies. To address these needs, we employed a transfer learning approach to derive gene-expression signatures from The Cancer Gene Atlas datasets that predict Fbw7 mutational status across tumor types and identified the pathways enriched within these signatures. Genes involved in mitochondrial function were highly enriched in pan-cancer signatures that predict Fbw7 mutations. Studies in isogenic colorectal cancer cell lines that differed in Fbw7 mutational status confirmed that Fbw7 mutations increase mitochondrial gene expression. Surprisingly, Fbw7 mutations shifted cellular metabolism toward oxidative phosphorylation and caused context-specific metabolic vulnerabilities. Our approach revealed unexpected metabolic reprogramming and possible therapeutic targets in Fbw7-mutant cancers and provides a framework to study other complex, oncogenic mutations.

A small-molecule inhibitor of Tcf/beta-catenin signaling down-regulates PPARgamma and PPARdelta activities.

Activation of the Wnt/beta-catenin signaling pathway occurs in several types of cancers and thus it is an attractive target for anticancer drug development. To identify compounds that inhibit this pathway, we screened a chemical library using a cell-based beta-catenin/Tcf-responsive reporter. We identified FH535, a compound that suppresses both Wnt/beta-catenin and peroxisome proliferator-activated receptor (PPAR) signaling. FH535 antagonizes both PPARgamma and PPARdelta ligand-dependent activation and shows structural similarity to GW9662, a known PPARgamma antagonist. The effect of FH535 on beta-catenin/Tcf activity is reduced in cells carrying a deletion of the PPARdelta gene, as well as by the PPARgamma agonist lysophosphatidic acid. Mechanistically, FH535 inhibits recruitment of the coactivators beta-catenin and GRIP1 but not the corepressors NCoR and SMRT. Its repression of beta-catenin recruitment, in comparison with GW9662, is linked to FH535's unique capability to inhibit the Wnt/beta-catenin signaling pathway. The antiproliferation effect of the compound observed on some transformed colon lung and liver cell lines is suggestive of its potential therapeutic value in the treatment of cancer.