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PDF file - 1.2MB, This file contains additional data on tumor responses to olaparib treatment (Fig. S1 and S2), pH2AX stainings on treated and untreated tumors (Fig. S3), analysis of mutations in 53BP1 (Fig. S4 and S7B), characterization of cell lines (Fig. S5), RAD51 and 53BP1 IRIFs in tumors and cell lines (Fig. S6 and S7), 53BP1 in topotecan-resistant tumors (Fig. S8) and tumor responses to AZD2461 treatment (Fig. S9 and S10).

Effects of AZD6738 on DNA damage repair capacity

Supplementary Information

U87/Centrin2-EGFP/H2B-mCherry/puro cells were seeded on dishes with cover slip bottoms, treated with AZ32 (3 uM), and irradiated (5 Gy). Time-lapse videos were recorded intermittently (every 7 min) over 16 hrs. Treatment results in 11% aberrant mitoses (see Fig. 3F).

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Supplementary Figure Legends

AZD6738 and gemcitabine synergistically inhibit cell growth in a panel of PDAC cell lines

U87/shp53/Centrin2-EGFP/H2B-mCherry/shp53 cells were seeded on dishes with cover slip bottoms and irradiated (5 Gy). Time-lapse videos were recorded intermittently (every 7 min) over 16 hrs. Treatment results in 12% aberrant mitoses (see Fig. 3F).

Pancreatic ductal adenocarcinoma (PDAC) is among the deadliest cancers, and overall survival rates have barely improved over the past five decades. The antimetabolite gemcitabine remains part of the standard of care but shows very limited antitumor efficacy. Ataxia telangiectasia and Rad3-related protein (ATR), the apical kinase of the intra–S-phase DNA damage response, plays a central role in safeguarding cells from replication stress and can therefore limit the efficacy of antimetabolite drug therapies. We investigated the ability of the ATR inhibitor, AZD6738, to prevent the gemcitabine-induced intra–S-phase checkpoint activation and evaluated the antitumor potential of this combination in vitro and in vivo. In PDAC cell lines, AZD6738 inhibited gemcitabine-induced Chk1 activation, prevented cell-cycle arrest, and restrained RRM2 accumulation, leading to the strong induction of replication stress markers only with the combination. Moreover, synergistic growth inhibition was identified in a panel of 5 mouse and 7 human PDAC cell lines using both Bliss Independence and Loewe models. In clonogenic assays, the combination abrogated survival at concentrations for which single agents had minor effects. In vivo, AZD6738 in combination with gemcitabine was well tolerated and induced tumor regression in a subcutaneous allograft model of a KrasG12D; Trp53R172H; Pdx-Cre (KPC) mouse cancer cell line, significantly extending survival. Remarkably, the combination also induced regression of a subgroup of KPC autochthonous tumors, which generally do not respond well to conventional chemotherapy. Altogether, our data suggest that AZD6738 in combination with gemcitabine merits evaluation in a clinical trial in patients with PDAC. Mol Cancer Ther; 17(8); 1670–82. ©2018 AACR.

Inhibition of PARP is a promising therapeutic strategy for homologous recombination–deficient tumors, such as BRCA1-associated cancers. We previously reported that BRCA1-deficient mouse mammary tumors may acquire resistance to the clinical PARP inhibitor (PARPi) olaparib through activation of the P-glycoprotein drug efflux transporter. Here, we show that tumor-specific genetic inactivation of P-glycoprotein increases the long-term response of BRCA1-deficient mouse mammary tumors to olaparib, but these tumors eventually developed PARPi resistance. In a fraction of cases, this resistance is caused by partial restoration of homologous recombination due to somatic loss of 53BP1. Importantly, PARPi resistance was minimized by long-term treatment with the novel PARP inhibitor AZD2461, which is a poor P-glycoprotein substrate. Together, our data suggest that restoration of homologous recombination is an important mechanism for PARPi resistance in BRCA1-deficient mammary tumors and that the risk of relapse of BRCA1-deficient tumors can be effectively minimized by using optimized PARP inhibitors.Significance: In this study, we show that loss of 53BP1 causes resistance to PARP inhibition in mouse mammary tumors that are deficient in BRCA1. We hypothesize that low expression or absence of 53BP1 also reduces the response of patients with BRCA1-deficient tumors to PARP inhibitors. Cancer Discov; 3(1); 68–81. ©2012 AACR.See related commentary by Fojo and Bates, p. 20This article is highlighted in the In This Issue feature, p. 1

PDF file - 28K, Information on all antibodies and primers that were used in this study

U87/Centrin2-EGFP/H2B-mCherry/puro cells were seeded on dishes with cover slip bottoms and irradiated (5 Gy). Time-lapse videos were recorded intermittently (every 7 min) over 16 hrs. Treatment results in 2.7% aberrant mitoses (see Fig. 3F).

Anti-proliferative effects of AZD6738 on gastric cancer cell lines

Genetic alterations likely to sensitize to ATR inhibition in the human PDAC cell lines

Inhibition of ataxia-telangiectasia mutated (ATM) during radiotherapy of glioblastoma multiforme (GBM) may improve tumor control by short-circuiting the response to radiation-induced DNA damage. A major impediment for clinical implementation is that current inhibitors have limited central nervous system (CNS) bioavailability; thus, the goal was to identify ATM inhibitors (ATMi) with improved CNS penetration. Drug screens and refinement of lead compounds identified AZ31 and AZ32. The compounds were then tested in vivo for efficacy and impact on tumor and healthy brain. Both AZ31 and AZ32 blocked the DNA damage response and radiosensitized GBM cells in vitro. AZ32, with enhanced blood–brain barrier (BBB) penetration, was highly efficient in vivo as radiosensitizer in syngeneic and human, orthotopic mouse glioma model compared with AZ31. Furthermore, human glioma cell lines expressing mutant p53 or having checkpoint-defective mutations were particularly sensitive to ATMi radiosensitization. The mechanism for this p53 effect involves a propensity to undergo mitotic catastrophe relative to cells with wild-type p53. In vivo, apoptosis was >6-fold higher in tumor relative to healthy brain after exposure to AZ32 and low-dose radiation. AZ32 is the first ATMi with oral bioavailability shown to radiosensitize glioma and improve survival in orthotopic mouse models. These findings support the development of a clinical-grade, BBB-penetrating ATMi for the treatment of GBM. Importantly, because many GBMs have defective p53 signaling, the use of an ATMi concurrent with standard radiotherapy is expected to be cancer-specific, increase the therapeutic ratio, and maintain full therapeutic effect at lower radiation doses. Mol Cancer Ther; 17(8); 1637–47. ©2018 AACR.

Ataxia telangiectasia and Rad3-related (ATR) can be considered an attractive target for cancer treatment due to its deleterious effect on cancer cells harboring a homologous recombination defect. The aim of this study was to investigate the potential use of the ATR inhibitor, AZD6738, to treat gastric cancer.In SNU-601 cells with dysfunctional ATM, AZD6738 treatment led to an accumulation of DNA damage due to dysfunctional RAD51 foci formation, S phase arrest, and caspase 3–dependent apoptosis. In contrast, SNU-484 cells with functional ATM were not sensitive to AZD6738. Inhibition of ATM in SNU-484 cells enhanced AZD6738 sensitivity to a level comparable with that observed in SNU-601 cells, showing that activation of the ATM-Chk2 signaling pathway attenuates AZD6738 sensitivity. In addition, decreased HDAC1 expression was found to be associated with ATM inactivation in SNU-601 cells, demonstrating the interaction between HDAC1 and ATM can affect sensitivity to AZD6738. Furthermore, in an in vivo tumor xenograft mouse model, AZD6738 significantly suppressed tumor growth and increased apoptosis.These findings suggest synthetic lethality between ATR inhibition and ATM deficiency in gastric cancer cells. Further clinical studies on the interaction between AZD 6738 and ATM deficiency are warranted to develop novel treatment strategies for gastric cancer. Mol Cancer Ther; 16(4); 566–77. ©2017 AACR.

Supplementary Data from Identification of a Molecularly-Defined Subset of Breast and Ovarian Cancer Models that Respond to WEE1 or ATR Inhibition, Overcoming PARP Inhibitor Resistance

Supplementary Figure from Identification of a Molecularly-Defined Subset of Breast and Ovarian Cancer Models that Respond to WEE1 or ATR Inhibition, Overcoming PARP Inhibitor Resistance

Purpose:PARP inhibitors (PARPi) induce synthetic lethality in homologous recombination repair (HRR)-deficient tumors and are used to treat breast, ovarian, pancreatic, and prostate cancers. Multiple PARPi resistance mechanisms exist, most resulting in restoration of HRR and protection of stalled replication forks. ATR inhibition was highlighted as a unique approach to reverse both aspects of resistance. Recently, however, a PARPi/WEE1 inhibitor (WEE1i) combination demonstrated enhanced antitumor activity associated with the induction of replication stress, suggesting another approach to tackling PARPi resistance.Experimental Design:We analyzed breast and ovarian patient-derived xenoimplant models resistant to PARPi to quantify WEE1i and ATR inhibitor (ATRi) responses as single agents and in combination with PARPi. Biomarker analysis was conducted at the genetic and protein level. Metabolite analysis by mass spectrometry and nucleoside rescue experiments ex vivo were also conducted in patient-derived models.Results:Although WEE1i response was linked to markers of replication stress, including STK11/RB1 and phospho-RPA, ATRi response associated with ATM mutation. When combined with olaparib, WEE1i could be differentiated from the ATRi/olaparib combination, providing distinct therapeutic strategies to overcome PARPi resistance by targeting the replication stress response. Mechanistically, WEE1i sensitivity was associated with shortage of the dNTP pool and a concomitant increase in replication stress.Conclusions:Targeting the replication stress response is a valid therapeutic option to overcome PARPi resistance including tumors without an underlying HRR deficiency. These preclinical insights are now being tested in several clinical trials where the PARPi is administered with either the WEE1i or the ATRi.

The PARP inhibitor AZD2461 was developed as a next-generation agent following olaparib, the first PARP inhibitor approved for cancer therapy. In BRCA1-deficient mouse models, olaparib resistance predominantly involves overexpression of P-glycoprotein, so AZD2461 was developed as a poor substrate for drug transporters. Here we demonstrate the efficacy of this compound against olaparib-resistant tumors that overexpress P-glycoprotein. In addition, AZD2461 was better tolerated in combination with chemotherapy than olaparib in mice, which suggests that AZD2461 could have significant advantages over olaparib in the clinic. However, this superior toxicity profile did not extend to rats. Investigations of this difference revealed a differential PARP3 inhibitory activity for each compound and a higher level of PARP3 expression in bone marrow cells from mice as compared with rats and humans. Our findings have implications for the use of mouse models to assess bone marrow toxicity for DNA-damaging agents and inhibitors of the DNA damage response. Finally, structural modeling of the PARP3-active site with different PARP inhibitors also highlights the potential to develop compounds with different PARP family member specificity profiles for optimal antitumor activity and tolerability. Cancer Res; 76(20); 6084–94. ©2016 AACR.

Purpose: Most patients with ovarian carcinomas succumb to their disease and there is a critical need for improved therapeutic approaches. Carcinomas arising in BRCA mutation carriers display defective DNA double-strand break repair that can be therapeutically exploited by inhibition of PARP-1, a key enzyme in the repair of DNA single-strand breaks, creating synthetic lethality in tumor cells.Experimental Design: To investigate synthetic lethality in vivo, we established a BRCA2 germline-mutated xenograft model that was developed directly from human ovarian cancer tissue, treated with the PARP inhibitor olaparib (AZD2281) alone and in combination with carboplatin.Results: We show that olaparib alone and in combination with carboplatin greatly inhibit growth in BRCA2-mutated ovarian serous carcinoma. This effect was not observed in a serous carcinoma with normal BRCA function, showing a specific antitumor effect of olaparib in mutation carriers. Immunohistochemistry (cleaved caspase-3 and Ki-67 stains) of remnant tissue after olaparib treatment revealed significantly decreased proliferation and increased apoptotic indices in these tumors compared with untreated controls. Furthermore, olaparib-treated tumors showed highly reduced PARP-1 activity that correlated with olaparib levels.Conclusions: We established a BRCA2-mutated human ovarian cancer xenograft model suitable for experimental drug testing. The demonstrated in vivo efficacy of olaparib extends on the preclinical rationale for further clinical trials targeting ovarian cancer patients with BRCA mutations. Clin Cancer Res; 17(4); 783–91. ©2010 AACR.

PDF file - 53K, Preparation of brain slices.

PDF file - 58K, Concentrations of KU-60019 in mouse brain after CED.

Supplementary Figure S1.

PDF File - 571K, Human U1242 glioma cells form highly invasive and aggressive orthotopic tumors in mice.

PDF file - 159K, U1242 tumors with 'forced' expression of mutant p53 are more sensitive to KU-60019.

PDF File - 49K, Imaging of tumors that were apparently cured.

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PDF file - 80K, Imaging of U87/luc-DsRed (p53-281G) bearing mice.

Supplementary materials and methods. Suppl Table 1. MMS combination PF50 cell line assays. Concentration-dependent potentiation of MMS (PF50 ratios). Suppl Table 2. Permeability of AZD2461 and olaparib were assessed. Suppl Table 3. Activity of olaparib and AZD2461 alone or in combination with the P-gp inhibitor verapamil in the colorectal cancer cell line HCT-15, which expresses high levels of P-gp. Suppl Fig. 1. Immunofluorescence for poly(ADP-ribose) in human A549 cells. Suppl Fig. 2. Analysis of both in vivo pharmacokinetics (PK) and pharmacodynamics (PD) in tumors taken from SW620 (human colon carcinoma) xenograft-bearing mice. Suppl Fig. 3. Colony formation (clonogenic) assays in the intrinsically high P-gp-expressing MRE11-deficient HCT-15 human colorectal cell line. Suppl. Fig. 4. Combination efficacy studies. Suppl Fig. 5. Relative body weight changes in mice following treatment with 10 mg/kg AZD2461 and olaparib in combination with temozolomide. Suppl. Fig. 6. A serial dilution of RNA concentration was used to establish a standard curve for determining the reaction efficiency of PARP1, PARP2, PARP3, and housekeeper gene (PPIA: cyclophilin A) TaqMan RT-PCR assays in both rat and mouse species; Determination of optimal reference gene for rat-mouse data normalization. Suppl Fig. 7.A. A serial dilution of reference RNA (Qiagen) concentration was used to establish a standard curve for determining the reaction efficiency of PARP3 and housekeeper genes (PPIA: cyclophilin and YWHAZ: tyrosine 3-monooxygenase/tryptohpan 5-monooxygenase activation protein, zeta polypeptide) SybrGreen RT-PCR assays in both rat and human species; Determination of optimal reference gene for rat-human data normalization. Suppl Fig. 8. Relative body weight changes in rat following treatment with 10 mg/kg AZD2461 and olaparib in combination with temozolomide; Relative body weight changes in rat following treatment with 20 mg/kg AZD2461 and olaparib in combination with temozolomide.

DNA damage checkpoint kinases ATR and WEE1 are among key regulators of DNA damage response pathways protecting cells from replication stress, a hallmark of cancer that has potential to be exploited for therapeutic use. ATR and WEE1 inhibitors are in early clinical trials and success will require greater understanding of both their mechanism of action and biomarkers for patient selection. Here, we report selective antitumor activity of ATR and WEE1 inhibitors in a subset of non-germinal center B-cell (GCB) diffuse large B-cell lymphoma (DLBCL) cell lines, characterized by high MYC protein expression and CDKN2A/B deletion. Activity correlated with the induction of replication stress, indicated by increased origin firing and retardation of replication fork progression. However, ATR and WEE1 inhibitors caused different amounts of DNA damage and cell death in distinct phases of the cell cycle, underlying the increased potency observed with WEE1 inhibition. ATR inhibition caused DNA damage to manifest as 53BP1 nuclear bodies in daughter G1 cells leading to G1 arrest, whereas WEE1 inhibition caused DNA damage and arrest in S phase, leading to earlier onset apoptosis. In vivo xenograft DLBCL models confirmed differences in single-agent antitumor activity, but also showed potential for effective ATR inhibitor combinations. Importantly, insights into the different inhibitor mechanisms may guide differentiated clinical development strategies aimed at exploiting specific vulnerabilities of tumor cells while maximizing therapeutic index. Our data therefore highlight clinical development opportunities for both ATR and WEE1 inhibitors in non-GCB DLBCL subtypes that represent an area of unmet clinical need.Significance:ATR and WEE1 inhibitors demonstrate effective antitumor activity in preclinical models of DLBCL associated with replication stress, but new mechanistic insights and biomarkers of response support a differentiated clinical development strategy.

PDF File - 80K, KU-60019 administered by CED radiosensitizes U1242 tumors.

PDF File - 578K, Human U1242/luc-GFP gliomas show dose-dependent increases in p-(S824)-KAP1 foci formation after radiation which can be inhibited by KU-60019.

Methods Table: Antibodies

PDF file - 45K, Preparation of calibration and QC solutions.

This file contains all supplementary figures. Figure 1-7 provide additional analysis of genetic and cell features associated with AZD6738 and AZD1775 activity in DLBCL cell lines, including immunochemistry, immunoblots, immunofluorescence and flow cytometry data to further support the conclusions made from data presented in the main manuscript. Fig 8 provides tumour volume and body weight measurements for individual animals used in the in vivo studies.

Supplementary Data from ATR Inhibitor AZD6738 (Ceralasertib) Exerts Antitumor Activity as a Monotherapy and in Combination with Chemotherapy and the PARP Inhibitor Olaparib

PDF file - 53K, Preparation of calibration and QC tissue matrix.

This file contains Supplementary Tables 1-6. Table S1 lists the growth inhibitory values of AZD6738 and cell doubling rates in DLBCL cell lines used in the study. Table S2 details the median replication fork velocities of DLBCL cell lines treated with DMSO and AZD6738 in Figure 3. Table S3 lists the statistical significance for DNA fibre analysis in Figure 3. Tables S4-S6 summarise the in vivo experiment groups used in the manuscript, including animal numbers in study, efficacy and body weight loss.

Supplementary Table 2 from Poly(ADP-Ribose) Polymerase-1 Inhibitor Treatment Regresses Autochthonous Brca2/p53-Mutant Mammary Tumors In vivo and Delays Tumor Relapse in Combination with Carboplatin

Supplementary Figure 1 from Poly(ADP-Ribose) Polymerase-1 Inhibitor Treatment Regresses Autochthonous Brca2/p53-Mutant Mammary Tumors In vivo and Delays Tumor Relapse in Combination with Carboplatin

Supplementary Figure 2 from Poly(ADP-Ribose) Polymerase-1 Inhibitor Treatment Regresses Autochthonous Brca2/p53-Mutant Mammary Tumors In vivo and Delays Tumor Relapse in Combination with Carboplatin