Preclinical data highlight AZD1390 as a potentially powerful new therapy to enhance brain tumor patient responses to radiotherapy.

Tumour-derived mutant p53 proteins promote invasion, in part, by enhancing Rab coupling protein (RCP)-dependent receptor recycling. Here we identified MET as an RCP-binding protein and showed that mutant p53 promoted MET recycling. Mutant p53-expressing cells were more sensitive to hepatocyte growth factor, the ligand for MET, leading to enhanced MET signalling, invasion and cell scattering that was dependent on both MET and RCP. In cells expressing the p53 family member TAp63, inhibition of TAp63 also lead to cell scattering and MET-dependent invasion. However, in cells that express very low levels of TAp63, the ability of mutant p53 to promote MET-dependent cell scattering was independent of TAp63. Taken together, our data show that mutant p53 can enhance MET signalling to promote cell scattering and invasion through both TAp63-dependent and -independent mechanisms. MET has a predominant role in metastatic progression and the identification of mechanisms through which mutations in p53 can drive MET signalling may help to identify and direct therapy.

Summaryp53 is a transcription factor that mediates tumor suppressor responses. Correct folding of the p53 protein is essential for these activities, and point mutations that induce conformational instability of p53 are frequently found in cancers. These mutant p53s not only lose wild-type activity but can also acquire the ability to promote invasion and metastasis. We show that folding of wild-type p53 is promoted by an interaction with the chaperonin CCT. Depletion of this chaperone in cells results in the accumulation of misfolded p53, leading to a reduction in p53-dependent gene expression. Intriguingly, p53 proteins mutated to prevent the interaction with CCT show conformational instability and acquire an ability to promote invasion and random motility that is similar to the activity of tumor-derived p53 mutants. Our data therefore suggest that both growth suppression and cell invasion may be differentially regulated functions of wild-type p53.

AZD0156 is a potent and selective, bioavailable inhibitor of ataxia-telangiectasia mutated (ATM) protein, a signaling kinase involved in the DNA damage response. We present preclinical data demonstrating abrogation of irradiation-induced ATM signaling by low doses of AZD0156, as measured by phosphorylation of ATM substrates. AZD0156 is a strong radiosensitizer in vitro, and using a lung xenograft model, we show that systemic delivery of AZD0156 enhances the tumor growth inhibitory effects of radiation treatment in vivo. Because ATM deficiency contributes to PARP inhibitor sensitivity, preclinically, we evaluated the effect of combining AZD0156 with the PARP inhibitor olaparib. Using ATM isogenic FaDu cells, we demonstrate that AZD0156 impedes the repair of olaparib-induced DNA damage, resulting in elevated DNA double-strand break signaling, cellcycle arrest, and apoptosis. Preclinically, AZD0156 potentiated the effects of olaparib across a panel of lung, gastric, and breast cancer cell lines in vitro, and improved the efficacy of olaparib in two patient-derived triple-negative breast cancer xenograft models. AZD0156 is currently being evaluated in phase I studies (NCT02588105).

The BTB (bric-a-brac, tramtrak and broad complex) ⁄ POZ (poxvirus zinc finger) domain is a proteinprotein interaction domain first described in several proteins of Drosophila melanogaster and poxvirus [1,2]. BTB ⁄ POZ domain-containing proteins constitute a diverse group of proteins involved in transcriptional repression, cytoskeletal regulation, and ion channel function [3]. More recently, some BTB proteins have been characterized as substrate-specific adaptors for cullin(CUL)3-based E3 ligases [4][5][6][7]. The BTB domain of these substrate-specific adaptors binds to CUL3, whereas additional domains in these polypeptides, such as zinc fingers, meprin and traf homology (MATH) domain, and Kelch repeats, work as substrate recognition domains. The first protein shown to be regulated by a CUL3 ligase was MEI-1 in Caenorhaditis elegans. This protein is part of the katanin-like microtubule severing complex [5,6] Potassium channel tetramerization domain (KCTD) proteins contain a bric-a-brac, tramtrak and broad complex (BTB) domain that is most similar to the tetramerization domain (T1) of voltage-gated potassium channels. Some BTB-domain-containing proteins have been shown recently to participate as substrate-specific adaptors in multimeric cullin E3 ligase reactions by recruiting proteins for ubiquitination and subsequent degradation by the proteasome. Twenty-two KCTD proteins have been found in the human genome, but their functions are largely unknown. In this study, we have characterized KCTD5, a new KCTD protein found in the cytosol of cultured cell lines. The expression of KCTD5 was upregulated post-transcriptionally in peripheral blood lymphocytes stimulated through the T-cell receptor. KCTD5 interacted specifically with cullin3, bound ubiquitinated proteins, and formed oligomers through its BTB domain. Analysis of the interaction with cullin3 showed that, in addition to the BTB domain, some amino acids in the N-terminus of KCTD5 are required for binding to cullin3. These findings suggest that KCTD5 is a substrate-specific adaptor for cullin3-based E3 ligases.Abbreviations AU, arbitrary unit; BTB, bric-a-brac, tramtrak and broad complex; CT, cycle threshold; CUL, cullin; GFP, green fluorescent protein; GST, glutathione S-transferase; HA, hemagglutinin; IL-2, interleukin-2; KCTD, potassium channel tetramerization domain; MATH, meprin and traf homology; PBL, peripheral blood lymphocyte; PHA, phytohemagglutinin; PMA, 4b-phorbol 12-myristate 13-acetate; POZ, poxvirus zinc finger; Ub, ubiquitin.