Ataxia-Telangiectasia Mutated Loss-of-Function Displays Variant and Tissue-Specific Differences across Tumor Types.

PURPOSE: Mutations in the ATM gene are common in multiple cancers, but clinical studies of therapies targeting ATM-aberrant cancers have yielded mixed results. Refinement of ATM loss of function (LOF) as a predictive biomarker of response is urgently needed. EXPERIMENTAL DESIGN: We present the first disclosure and preclinical development of a novel, selective ATR inhibitor, ART0380, and test its antitumor activity in multiple preclinical cancer models. To refine ATM LOF as a predictive biomarker, we performed a comprehensive pan-cancer analysis of ATM variants in patient tumors and then assessed the ATM variant-to-protein relationship. Finally, we assessed a novel ATM LOF biomarker approach in retrospective clinical data sets of patients treated with platinum-based chemotherapy or ATR inhibition. RESULTS: ART0380 had potent, selective antitumor activity in a range of preclinical cancer models with differing degrees of ATM LOF. Pan-cancer analysis identified 10,609 ATM variants in 8,587 patient tumors. Cancer lineage-specific differences were seen in the prevalence of deleterious (Tier 1) versus unknown/benign (Tier 2) variants, selective pressure for loss of heterozygosity, and concordance between a deleterious variant and ATM loss of protein (LOP). A novel ATM LOF biomarker approach that accounts for variant classification, relationship to ATM LOP, and tissue-specific penetrance significantly enriched for patients who benefited from platinum-based chemotherapy or ATR inhibition. CONCLUSIONS: These data help to better define ATM LOF across tumor types in order to optimize patient selection and improve molecularly targeted therapeutic approaches for patients with ATM LOF cancers.

Small-Molecule Polθ Inhibitors Provide Safe and Effective Tumor Radiosensitization in Preclinical Models.

PURPOSE: DNA polymerase theta (Polθ, encoded by the POLQ gene) is a DNA repair enzyme critical for microhomology mediated end joining (MMEJ). Polθ has limited expression in normal tissues but is frequently overexpressed in cancer cells and, therefore, represents an ideal target for tumor-specific radiosensitization. In this study we evaluate whether targeting Polθ with novel small-molecule inhibitors is a feasible strategy to improve the efficacy of radiotherapy. EXPERIMENTAL DESIGN: We characterized the response to Polθ inhibition in combination with ionizing radiation in different cancer cell models in vitro and in vivo. RESULTS: Here, we show that ART558 and ART899, two novel and specific allosteric inhibitors of the Polθ DNA polymerase domain, potently radiosensitize tumor cells, particularly when combined with fractionated radiation. Importantly, noncancerous cells were not radiosensitized by Polθ inhibition. Mechanistically, we show that the radiosensitization caused by Polθ inhibition is most effective in replicating cells and is due to impaired DNA damage repair. We also show that radiosensitization is still effective under hypoxia, suggesting that these inhibitors may help overcome hypoxia-induced radioresistance. In addition, we describe for the first time ART899 and characterize it as a potent and specific Polθ inhibitor with improved metabolic stability. In vivo, the combination of Polθ inhibition using ART899 with fractionated radiation is well tolerated and results in a significant reduction in tumor growth compared with radiation alone. CONCLUSIONS: These results pave the way for future clinical trials of Polθ inhibitors in combination with radiotherapy.

Polθ inhibitors elicit BRCA-gene synthetic lethality and target PARP inhibitor resistance.

To identify approaches to target DNA repair vulnerabilities in cancer, we discovered nanomolar potent, selective, low molecular weight (MW), allosteric inhibitors of the polymerase function of DNA polymerase Polθ, including ART558. ART558 inhibits the major Polθ-mediated DNA repair process, Theta-Mediated End Joining, without targeting Non-Homologous End Joining. In addition, ART558 elicits DNA damage and synthetic lethality in BRCA1- or BRCA2-mutant tumour cells and enhances the effects of a PARP inhibitor. Genetic perturbation screening revealed that defects in the 53BP1/Shieldin complex, which cause PARP inhibitor resistance, result in in vitro and in vivo sensitivity to small molecule Polθ polymerase inhibitors. Mechanistically, ART558 increases biomarkers of single-stranded DNA and synthetic lethality in 53BP1-defective cells whilst the inhibition of DNA nucleases that promote end-resection reversed these effects, implicating these in the synthetic lethal mechanism-of-action. Taken together, these observations describe a drug class that elicits BRCA-gene synthetic lethality and PARP inhibitor synergy, as well as targeting a biomarker-defined mechanism of PARPi-resistance.

Working conditions and psychosocial risk factors of employees in French electricity and gas company customer support departments.

OBJECTIVE: Little is known about the real impact of working conditions on the health of call center employees. The aim of this article is to describe the working conditions of French electricity and gas company customer service teams, especially those spending more than 75% of their working time handling calls in order to determine their subjective experience of their work and identify situations at risk of psychosocial constraints. METHODS: A cross-sectional study using a self-completion questionnaire was conducted on a representative sample of 2,000 employees working in customer service centers. The questions focused on the variety of tasks performed, the organization of working time, the physical environment of the workstation, violent situations and psychosocial factors (Job Content Questionnaire). Multivariate statistical analyses were performed to identify factors associated with the wish to leave the sector and with a high level of psychosocial constraints. RESULTS: Women made up 66% of the sample. Despite a high educational level, the average socio-professional level of the employees was relatively low. Although the vast majority of employees had chosen this career (74%), just over half would like to leave. The main factors associated with iso-strain were inadequate breaks (odds ratio (OR) = 2.0), low perceived quality of work (OR = 2.4), high proportion of working time spent handling calls (≥75% of working time: OR = 5.9, between 50 and <75%: OR = 5.2), exposure to violence either internally (often or very often: OR = 3.1) or from customers (often or very often: OR = 1.8) and an unsatisfactory workplace (OR = 2.0). CONCLUSIONS: Employees who spend more than 75% of their working time on the phone cumulate every factor linked with a high level of constraints, but all employees of the EDF and Gaz de France customer service centers are concerned. These workers share many characteristics with other call centers: predominantly female workforce; high educational level; wish to leave this sector despite the initial choice; high level of psychosocial risk factors.