Patients with acute myeloid leukemia (AML) frequently relapse after chemotherapy, yet the mechanism by which AML reemerges is not fully understood. Herein, we show that primary AML cells enter a senescence-like phenotype following chemotherapy in vitro and in vivo. This is accompanied by induction of senescence/inflammatory and embryonic diapause transcriptional programs, with downregulation of MYC and leukemia stem cell genes. Single-cell RNA sequencing suggested depletion of leukemia stem cells in vitro and in vivo, and enrichment for subpopulations with distinct senescence-like cells. This senescence effect was transient and conferred superior colony-forming and engraftment potential. Entry into this senescence-like phenotype was dependent on ATR, and persistence of AML cells was severely impaired by ATR inhibitors. Altogether, we propose that AML relapse is facilitated by a senescence-like resilience phenotype that occurs regardless of their stem cell status. Upon recovery, these post-senescence AML cells give rise to relapsed AMLs with increased stem cell potential. SIGNIFICANCE: Despite entering complete remission after chemotherapy, relapse occurs in many patients with AML. Thus, there is an urgent need to understand the relapse mechanism in AML and the development of targeted treatments to improve outcome. Here, we identified a senescence-like resilience phenotype through which AML cells can survive and repopulate leukemia.This article is highlighted in the In This Issue feature, p. 1307.

/pdf/chemotherapy-induces-senescence-like-resilient-cells-capable-3pni7drg7k.pdf

Chemotherapy Induces Senescence-Like Resilient Cells Capable of Initiating AML Recurrence.

https://spiral.imperial.ac.uk/bitstream/10044/1/84869/4/ATM%20Supplementary%20final%2007Oct2020.pdf

Advanced Prostate Cancer with ATM Loss: PARP and ATR Inhibitors

Synthetic lethality (SL) provides a conceptual framework for tackling targets that are not classically "druggable," including loss-of-function mutations in tumor suppressor genes required for carcinogenesis Recent technological advances have led to an inflection point in our understanding of genetic interaction networks and ability to identify a wide array of novel SL drug targets Here, we review concepts and lessons emerging from first-generation trials aimed at testing SL drugs, discuss how the nature of the targeted lesion can influence therapeutic outcomes, and highlight the need to develop clinical biomarkers distinct from those based on the paradigms developed to target activated oncogenes SIGNIFICANCE: SL offers an approach for the targeting of loss of function of tumor suppressor and DNA repair genes, as well as of amplification and/or overexpression of genes that cannot be targeted directly A next generation of tumor-specific alterations targetable through SL has emerged from high-throughput CRISPR technology, heralding not only new opportunities for drug development, but also important challenges in the development of optimal predictive biomarkers

Synthetic Lethality in Cancer Therapeutics: The Next Generation.

Targeting DNA damage response pathways in cancer

Despite advances in the screening and treatment of prostate cancer, the therapy options available, particularly for later stages of the disease, remain limited, and the treatment-resistant setting represents a serious unmet medical need. Moreover, disease heterogeneity and disparities in patient access to medical advances result in considerable variability in outcomes across patients. Disease classification based on genomic sequencing is a promising approach for identifying patients whose tumors exhibit actionable targets and for making more informed treatment decisions. Here we discuss how precision oncology can be accelerated to inform broader genomically driven clinical decisions for men with advanced prostate cancer, to inform drug development and, ultimately, to contribute to new treatment paradigms. Beltran and colleagues discuss the challenges in treating metastatic prostate cancer and strategies to accelerate precision oncology and improve therapy and clinical decisions in this setting.

Accelerating precision medicine in metastatic prostate cancer.

Targeting the ataxia telangiectasia and RAD3-related (ATR) enzyme represents a promising anticancer strategy for tumors with DNA damage response (DDR) defects and replication stress, including inactivation of ataxia telangiectasia mutated (ATM) signaling. We report the dose-escalation portion of the phase I first-in-human trial of oral ATR inhibitor BAY 1895344 intermittently dosed 5 to 80 mg twice daily in 21 patients with advanced solid tumors. The MTD was 40 mg twice daily 3 days on/4 days off. Most common adverse events were manageable and reversible hematologic toxicities. Partial responses were achieved in 4 patients and stable disease in 8 patients. Median duration of response was 315.5 days. Responders had ATM protein loss and/or deleterious ATM mutations and received doses ≥40 mg twice daily. Overall, BAY 1895344 is well tolerated, with antitumor activity against cancers with certain DDR defects, including ATM loss. An expansion phase continues in patients with DDR deficiency. SIGNIFICANCE: Oral BAY 1895344 was tolerable, with antitumor activity in heavily pretreated patients with various advanced solid tumors, particularly those with ATM deleterious mutations and/or loss of ATM protein; pharmacodynamic results supported a mechanism of action of increased DNA damage. Further study is warranted in this patient population.See related commentary by Italiano, p. 14.This article is highlighted in the In This Issue feature, p. 1.

/pdf/first-in-human-trial-of-the-oral-ataxia-telangiectasia-and-1opn7bs53p.pdf

Matthias Ludwig

Papers

First-in-Human Trial of the Oral Ataxia Telangiectasia and RAD3-Related (ATR) Inhibitor BAY 1895344 in Patients with Advanced Solid Tumors.