Target identification for small-molecule discovery in the FOXO3a tumor-suppressor pathway using a biodiverse peptide library.

Genetic screening technologies to identify and validate macromolecular interactions (MMIs) essential for complex pathways remain an important unmet need for systems biology and therapeutics development. Here, we use a library of peptides from diverse prokaryal genomes to screen MMIs promoting the nuclear relocalization of Forkhead Box O3 (FOXO3a), a tumor suppressor more frequently inactivated by post-translational modification than mutation. A hit peptide engages the 14-3-3 family of signal regulators through a phosphorylation-dependent interaction, modulates FOXO3a-mediated transcription, and suppresses cancer cell growth.

Correction: Correction: CDK1 Is a Synthetic Lethal Target for KRAS Mutant Tumours.

[This corrects the article DOI: 10.1371/journal.pone.

Modulating Protein-Protein Interactions of the Mitotic Polo-like Kinases to Target Mutant KRAS.

Mutations activating KRAS underlie many forms of cancer, but are refractory to therapeutic targeting. Here, we develop Poloppin, an inhibitor of protein-protein interactions via the Polo-box domain (PBD) of the mitotic Polo-like kinases (PLKs), in monotherapeutic and combination strategies to target mutant KRAS. Poloppin engages its targets in biochemical and cellular assays, triggering mitotic arrest with defective chromosome congression.

A 'synthetic-sickness' screen for senescence re-engagement targets in mutant cancer backgrounds.

Senescence is a universal barrier to immortalisation and tumorigenesis. As such, interest in the use of senescence-induction in a therapeutic context has been gaining momentum in the past few years; however, senescence and immortalisation remain underserved areas for drug discovery owing to a lack of robust senescence inducing agents and an incomplete understanding of the signalling events underlying this complex process. In order to address this issue we undertook a large-scale morphological siRNA screen for inducers of senescence phenotypes in the human melanoma cell line A375P.

Correction: CDK1 Is a Synthetic Lethal Target for KRAS Mutant Tumours.

[This corrects the article DOI: 10.1371/journal.pone.

CDK1 Is a Synthetic Lethal Target for KRAS Mutant Tumours.

Activating KRAS mutations are found in approximately 20% of human cancers but no RAS-directed therapies are currently available. Here we describe a novel, robust, KRAS synthetic lethal interaction with the cyclin dependent kinase, CDK1. This was discovered using parallel siRNA screens in KRAS mutant and wild type colorectal isogenic tumour cells and subsequently validated in a genetically diverse panel of 26 colorectal and pancreatic tumour cell models.

Cell-based screen for altered nuclear phenotypes reveals senescence progression in polyploid cells after Aurora kinase B inhibition.

Cellular senescence is a widespread stress response and is widely considered to be an alternative cancer therapeutic goal. Unlike apoptosis, senescence is composed of a diverse set of subphenotypes, depending on which of its associated effector programs are engaged. Here we establish a simple and sensitive cell-based prosenescence screen with detailed validation assays.

Activity of EGFR, mTOR and PI3K inhibitors in an isogenic breast cell line model.

Background: The epidermal growth factor receptor family is expressed in breast cancer, and agents targeting this pathway have single agent effects (e.g. traztuzumab).

Active PI3K pathway causes an invasive phenotype which can be reversed or promoted by blocking the pathway at divergent nodes.

The PTEN/PI3K pathway is commonly mutated in cancer and therefore represents an attractive target for therapeutic intervention. To investigate the primary phenotypes mediated by increased pathway signaling in a clean, patient-relevant context, an activating PIK3CA mutation (H1047R) was knocked-in to an endogenous allele of the MCF10A non-tumorigenic human breast epithelial cell line. Introduction of an endogenously mutated PIK3CA allele resulted in a marked epithelial-mesenchymal transition (EMT) and invasive phenotype, compared to isogenic wild-type cells.

Cancer cell senescence: a new frontier in drug development.

Senescence forms a universal block to tumorigenesis which impacts on all hallmarks of cancer, making it an attractive target for drug discovery. Therefore a strategy must be devised to focus this broad potential into a manageable drug discovery programme. Several issues remain to be addressed including the lack of robust senescence-inducing compounds and causally related biomarkers to measure cellular response.

Discovery of a potent CDK2 inhibitor with a novel binding mode, using virtual screening and initial, structure-guided lead scoping.

Virtual screening against a pCDK2/cyclin A crystal structure led to the identification of a potent and novel CDK2 inhibitor, which exhibited an unusual mode of interaction with the kinase binding motif. With the aid of X-ray crystallography and modelling, a medicinal chemistry strategy was implemented to probe the interactions seen in the crystal structure and to establish SAR. A fragment-based approach was also considered but a different, more conventional, binding mode was observed.

Triazolo[1,5-a]pyrimidines as novel CDK2 inhibitors: protein structure-guided design and SAR.

Crystallographic and modelling data, in conjunction with a medicinal chemistry template-hopping approach, led to the identification of a series of novel and potent inhibitors of human cyclin-dependent kinase 2 (CDK2), with selectivity over glycogen synthase kinase-3beta (GSK-3beta). One example had a CDK2 IC(50) of 120 nM and showed selectivity over GSK-3beta of 167-fold.

Structure-guided design of pyrazolo[1,5-a]pyrimidines as inhibitors of human cyclin-dependent kinase 2.

The protein structure guided design of a series of pyrazolo[1,5-a]pyrimidines with high potency for human cyclin-dependent kinase 2 (CDK2) is described. Some examples were shown to inhibit the growth of human colon tumour cells, were equipotent for CDK1 and were selective against GSK-3beta and other kinases.

DEC1 is a downstream target of TGF-beta with sequence-specific transcriptional repressor activities.

To identify genes that mediate transforming growth factor-beta (TGF-beta) signaling, a colorectal cancer cell line that was sensitive to the growth inhibitory effects of this cytokine was created. We then determined the global gene expression profiles of these cells, and those of HaCaT human keratinocytes, in the presence and absence of TGF-beta. Of the several genes identified in this screen, DEC1 was of particular note in light of the rapidity and consistency of its induction and its potential biochemical activities.