Image based pathway analysis of FOXO regulation leads to the discovery of therapeutic targets and small molecule inhibitors for anticancer therapy


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Wolfgang Link, Amancio Carnero, Fabian Zanells

Spanish National Cancer Centre (CNIO), Madrid, Spain

Abstract

FOXO transcription factors are evolutionarily conserved proteins that orchestrate programs of gene expression known to control a variety of cellular processes such as cell cycle, apoptosis, DNA repair and protection from oxidative stress. Since the abrogation of FOXO function is a key feature of many tumour cells, regulation of the FOXO factors is receiving increasing attention in cancer research. In order to identify potential molecular targets or compounds with therapeutic potential we developed a high-throughput cellular imaging assay that follows the intracellular location of the FoxO3a protein in tumour cells. Using this assay we screened 21000 shRNAs and a collection of approximately 35,000 small molecules.

We discovered previously unrecognized FOXO-repressor functions of several human genes. We will present data that show the essential role of one of these genes in the maintenance of the oncogenic properties of malignant melanoma suggesting it as a potential therapeutic target for cancer treatment. Furthermore, we identified chemical agents capable of inducing the translocation of a FOXO reporter protein from the cytoplasm to the nucleus. The implementation of a hierarchical network of screens and counter-screens allowed us to pinpoint the molecular targets for many novel small molecule inhibitors. 222 compounds were found that selectively induced the nuclear translocation of GFP-FOXO yet did not affect general nuclear export, 54 were found to inhibit PI3Kα directly. Stucture activity relationship (SAR) and virtual docking studies lead to the synthesis of ETP-45658, a pyrazolo pyrimidine that inhibits PI3Kα with an IC50 value of 22 nanomolar.