PARP Inhibitors Research Articles

The radiosensitivity of niraparib tosylate to esophageal squamous cell carcinoma is stronger under hypoxia and higher-pressure conditions

Background: Radiotherapy is an effective method for esophageal squamous cell carcinoma (ESCC) treatment show reduced effectiveness in long-term due to reduced sensitivity of cancer cells to radiotherapy. Niraparib tosylate, a poly ADP-ribose polymerase (PARP) inhibitor may enhance the radiosensitivity of these cells. Hence, the present study was aimed to study the effects of niraparib tosylate on ESCC proliferation, apoptosis and cell cycle along with radiosensitivity enhancement efficiency. Materials and methods: ESCC cell lines, KYSE-30 were subjected to niraparib tosylate or irradiation treatments or combination of both. CCK8 and colony formation assays were performed to monitor cell growth status. Cell cycle and apoptosis level were investigated through flow cytometry. The expressions of targeted genes were detected at protein levels by western blot. Besides, xenografts were successfully established in immunocompromised mice. Student’s t-test was used to compare data and P < 0.05 was considered statistically significant. Results: Treatment with niraparib tosylate showed G2/M cycle arrest and apoptosis in KYSE-30 cells and the rate was observed to be more significant with combination therapy. These effects were further strengthened when cells were cultured under hypoxia and high atmospheric pressure. An enhanced susceptibility to radiotherapy was observed with niraparib tosylate combination. The homologous recombination related regulator, Rad51, showed remarkable upregulation in cancer cells exposed to combination of drug-radiation treatment. The tumor burden was also relieved in xenograft mouse models with combination of drug-radiation treatment, indicating the potential of niraparib tosylate use clinical cancer therapy. Conclusion: From the results, a novel function of niraparib tosylate can be established, impairing DNA damage repair efficiency to increase the susceptibility of ESCC to radiotherapy, resulting in cell apoptosis and G2/M cycle arrest in vitro and in vivo.

Retraction: Combining PARP-1 Inhibition and Radiation in Ewing Sarcoma Results in Lethal DNA Damage.

Retraction: Combining PARP-1 Inhibition and Radiation in Ewing Sarcoma Results in Lethal DNA Damage.

Resveratrol Inhibits Nucleosome Binding and Catalytic Activity of PARP1

The natural polyphenol resveratrol is a biologically active compound that interacts with DNA and affects the activity of some nuclear enzymes. Its effect on the interaction between nucleosomes and poly(ADP-ribose) polymerase-1 (PARP1) and on the catalytic activity of PARP1 was studied using Western blotting, spectrophotometry, electrophoretic mobility shift assay, and single particle Förster resonance energy transfer microscopy. Resveratrol inhibited PARP1 activity at micro- and sub-micromolar concentrations, but the inhibitory effect decreased at higher concentrations due to the aggregation of the polyphenol. The inhibition of PARP1 by resveratrol was accompanied by its binding to the enzyme catalytic center and a subsequent decrease in PARP1 affinity to nucleosomal DNA. Concurrent binding of talazoparib to the substrate binding pocket of PARP1, which occurs in the presence of resveratrol, restores the interaction of PARP1 with nucleosomes, suggesting that the binding sites of resveratrol and talazoparib overlap. The data suggest that resveratrol can be classified as a natural inhibitor of PARP1.

A Gene Expression Signature that Predicts Gastric Cancer Sensitivity to PARP Inhibitor Therapy.

Biomarkers indicating sensitivity to poly ADP-ribose polymerase (PARP) inhibitors have not yet been identified in gastric cancer. PARP inhibitors target homologous recombination deficiency (HRD); however, homologous recombination (HR) induces complex changes in gene expression, which makes it difficult to identify reliable biomarkers. In this study, we identified a multi-gene expression signature as a marker of PARP inhibitor sensitivity in gastric cancer. Seven gastric cancer cell lines were evaluated for susceptibility to PARP inhibitors using a growth inhibition assay. Gene expression profiling (GEP) was used to identify differentially expressed genes between PARP inhibitor-sensitive and -resistant cell lines. The resulting gene set was subjected to cluster analysis using tumor samples from 250 patients who underwent gastrectomy for primary gastroesophageal junction and gastric adenocarcinoma. HRD was defined as a truncating mutation in one or more of 22 HR-related genes and HRD scores were calculated using whole-exome sequencing data. In the growth inhibition assays, the HGC27 and HSC39 cell lines were sensitive to the PARP inhibitors, olaparib, and rucaparib, and were significantly correlated with the GEP results. Seven (2.8%) patients harbored truncating mutations in HR-related genes. A gene expression signature based on the top 100 high and low differentially expressed genes between sensitive and resistant cell lines revealed a patient cluster with a high prevalence of HR-related gene mutations and high HRD scores. The 100-gene expression signature identified in this study may serve as a valuable predictive biomarker for PARP inhibitor sensitivity in gastric cancer.

Use of DNA methyltransferase inhibitor and poly(adenosine diphosphate ribose) polymerase inhibitor (PARPi) in the treatment of PARPi-resistant, high-grade serous ovarian cancer

Use of DNA methyltransferase inhibitor and poly(adenosine diphosphate ribose) polymerase inhibitor (PARPi) in the treatment of PARPi-resistant, high-grade serous ovarian cancer

Efficacy of subsequent therapies in patients with advanced ovarian cancer who relapse after first-line olaparib maintenance: results of the PAOLA-1/ENGOT-ov25 trial

BackgroundUse of first-line PARP inhibitor maintenance therapy is increasing in advanced ovarian cancer. Understanding the efficacy of first subsequent therapy (FST) in patients experiencing disease progression in the first-line setting is important to optimize post-progression treatments. We evaluated the efficacy of FST in patients from PAOLA-1/ENGOT-ov25 (NCT02477644) who received first-line olaparib maintenance. Patients and methodsThis post hoc analysis evaluated the efficacy of subsequent chemotherapy following disease progression by assessing time from FST to second subsequent therapy (SST) according to whether progression occurred during versus after first-line olaparib maintenance and FST type. A multivariate Cox model was used in the olaparib plus bevacizumab arm to identify prognostic factors influencing the efficacy of subsequent chemotherapy. ResultsOf 806 randomized patients, 544 (67.5%) progressed and received subsequent chemotherapy. The median time from FST to SST was shorter in patients in the olaparib plus bevacizumab arm who progressed during first-line olaparib maintenance (6.1 months) than in those who progressed after first-line olaparib maintenance (11.4 months). Multivariate analysis indicated that progression after (versus during) first-line olaparib maintenance influenced time from FST to SST (hazard ratio 0.65, 95% CI 0.50-0.84; P=0.0011) independently of platinum-free interval or clinical risk. Among patients who progressed and received platinum-based chemotherapy with a PARP inhibitor as FST, the efficacy of subsequent therapies was also dependent upon whether progression occurred during versus after first-line olaparib maintenance. ConclusionsThese results suggest that the timing of disease progression relative to first-line olaparib maintenance may impact the efficacy of subsequent platinum-based chemotherapy. Although results should be interpreted with caution, across all subgroups, including patients who received platinum-based chemotherapy with PARP inhibitor rechallenge as FST, the median time from FST to SST was longer if progression occurred after versus during first-line olaparib maintenance.

Potential Transcriptomic Biomarkers for Predicting Platinum-based Chemotherapy Resistance in Patients With High-grade Serous Ovarian Cancer.

Due to the absence of screening protocols, high-grade serous ovarian cancer (HGSOC) patients are frequently diagnosed at an advanced stage, which significantly reduces the survival rate. Moreover, relapse occurs in approximately 70% of HGSOC patients after primary treatment. Predicting resistance to primary chemotherapy remains a challenge. In the research setting, transcriptomic analyses have emerged as powerful tools for predicting which HGSOC patients are likely to benefit from primary treatment. The aim of this review was to investigate the literature demonstrating the potential of transcriptomic signatures as biomarkers for assessing the risk of resistance to platinum-based chemotherapy. We conducted a three-step search process on PubMed to systematically review English-language articles published between 2020 and 2024. From the 123 articles retrieved, we included 11 articles that investigated transcriptomic signatures by RNA sequencing in tissues from chemo-sensitive and -resistant HGSOC patients. We report the clinicopathological data of 727 patients in the experimental cohorts, transcriptomic signatures, and technical aspects. Finally, the review lists 15 publicly available datasets used in the included studies. Furthermore, we investigated the overlap of 167 differentially expressed genes retrieved across the various articles. We believe this review might offer valuable insights for further studies focusing on predicting platinum resistance and personalized treatments. In addition to discussing the latest findings and potential candidates, we highlight the challenges of validating biomarkers across studies and publicly available datasets. Transcriptomic signatures represent a potential tool for patient stratification, prognosis, and the potential adoption of long-term therapies, such as poly (ADP-ribose) polymerase inhibitors (PARPis).

Phase II randomized study of maintenance atezolizumab (A) versus atezolizumab + talazoparib (AT) in patients with SLFN11 positive extensive stage small cell lung cancer. S1929

To evaluate whether the addition of a poly (ADP-ribose) polymerase inhibitor (PARPi) talazoparib to maintenance immune checkpoint inhibitor (ICI) atezolizumab following frontline chemoimmunotherapy improved outcomes in patients with Schlafen 11 (SLFN11)-positive extensive stage small cell lung cancer (ES-SCLC). Patients with newly diagnosed SLFN11 expressing (H-score ≥ 1, evaluated centrally) ES-SCLC were randomized to maintenance atezolizumab (A) versus atezolizumab plus talazoparib (AT) following frontline chemotherapy plus atezolizumab. The primary objective was to compare progression-free survival (PFS) using a 1-sided 10% level stratified log-rank test. Secondary endpoints included objective response rate (ORR), overall survival (OS), and toxicity. Target sample size was 84 eligible patients. From June 15, 2020 to December 15, 2022, 106 eligible patients were randomized (54 to AT and 52 to A). PFS was improved with AT versus A (hazard ratio [HR], 0.66; 80% confidence interval [CI]: 0.50-0.86; 1-sided P = 0.019) with a median PFS of 2.9 and 2.4 months; OS was not different between groups (HR, 0.98; 80% CI: 0.71-1.36; 1-sided P = 0.47). Grade ≥ 3 non-hematologic treatment-related adverse events (TRAEs) occurred in 17% of patients with AT and 14% of patients with A. Grade ≥ 3 hematological TRAEs were more common in AT (50%) than in A (4%) (P < 0.001). Maintenance AT improved PFS in patients with SLFN11-positive ES-SCLC that did not progress following initial chemo-immunotherapy. Hematologic toxicity, primarily grade 3 anemia, was increased with AT, as expected. Prospective biomarker-selection was demonstrated, paving the way for future evaluation of novel therapies in molecularly defined SCLC populations.

Trends in estimated percentage of patients with epithelial ovarian cancer eligible for and benefiting from PARP inhibitors over time

Trends in estimated percentage of patients with epithelial ovarian cancer eligible for and benefiting from PARP inhibitors over time

Discovery of KPT-6566 as STAG1/2 Inhibitor sensitizing PARP and NHEJ Inhibitors to suppress tumor cells growth in vitro

Stromal antigen 1 and 2 (STAG1 and STAG2) are two mutually exclusive components of the cohesin complex that is crucial for centromeric and telomeric cohesion. Beyond its structural role, STAG2 also plays a pivotal role in homologous recombination (HR) repair and has emerged as a promising therapeutic target in cancer treatment. Here, we employed a fluorescence polarization (FP)-based high-throughput screening and identified KPT-6566 as a dual inhibitor of STAG1 and STAG2. Biochemical and biophysical analyses demonstrated that KPT-6566 directly binds to STAG1 and STAG2, disrupting their interactions with SCC1 and double-stranded DNA. A metaphase chromosome spread assay showed that KPT-6566 causes premature chromosome separation and induces chromosome damages in HeLa cells. Furthermore, KPT-6566 also impairs DNA damage repair, leading to the accumulation of double-strand breaks and cell apoptosis. Finally, KPT-6566 can sensitize HeLa and HepG2 cells to PARP inhibitor Olaparib and the NHEJ inhibitor UMI-77, exhibiting a synergistic effect in suppressing cell proliferation. Our findings highlight the potential of STAG1/2 as promising therapeutic targets in cancer treatment, particularly when they are targeted in combination with other DNA damage response inhibitors.

COPANIRA: Phase Ib trial of copanlisib (PI3K inhibitor) and niraparib (PARP inhibitor) in recurrent ovarian and endometrial cancer

COPANIRA: Phase Ib trial of copanlisib (PI3K inhibitor) and niraparib (PARP inhibitor) in recurrent ovarian and endometrial cancer

Pan-cancer Analysis of Homologous Recombination Deficiency in Cell Lines.

Homologous Recombination Deficiency (HRD) drives genomic instability in multiple cancer types and renders tumors vulnerable to certain DNA damaging agents such as PARP inhibitors. Thus, HRD is emerging as an attractive biomarker in oncology. A variety of in silico methods are available for predicting HRD; however, few of these methods have been applied to cell lines in a comprehensive manner. Here we utilized two of these methods, "CHORD" and "HRDsum" scores, to predict HRD for 1,332 cancer cell lines and 84 non-cancerous cell lines. Cell lines with biallelic mutations in BRCA1 or BRCA2, which encode key components of the homologous recombination pathway, showed the strongest HRD predictions, validating the two methods in cell lines. A small subset of BRCA1/2-wildtype cell lines were also classified as HRD, several of which showed evidence of epigenetic BRCA1 silencing. Similar to HRD in patient samples, HRD in cell lines was associated with p53 loss, was mutually exclusive with microsatellite instability and occurred most frequently in breast and ovarian cancer types. In addition to validating previously identified associations with HRD, we leveraged cell line-specific datasets to gain new insights into HRD and its relation to various genetic dependency and drug sensitivity profiles. We found that in cell lines, HRD was associated with sensitivity to PARP inhibition in breast cancer, but not at a pan-cancer level. By generating large-scale, pan-cancer datasets on HRD predictions in cell lines, we aim to facilitate efforts to improve our understanding of HRD and its utility as a biomarker.

PARP inhibitors and maintenance treatment decision-making in advanced ovarian cancer: Patient and clinician perspectives

PARP inhibitors and maintenance treatment decision-making in advanced ovarian cancer: Patient and clinician perspectives

Homologous recombination deficiency score is an independent prognostic factor in esophageal squamous cell carcinoma.

Homologous recombination deficiency (HRD) represents an impairment in the homologous recombination repair (HRR) pathway, crucial for repairing DNA double-strand breaks and contributing to genomic instability in cancer. The HRD score may be a more reliable biomarker than HRR-related gene mutations for identifying patients sensitive to poly(ADP-ribose) polymerase inhibitors. Despite its relevance in various cancers, the HRD score remains underexplored in esophageal squamous cell carcinoma (ESCC). We retrospectively analyzed HRD scores in 96 ESCC patients, examining correlations with clinical characteristics and survival outcomes, and validated our findings using the TCGA dataset. Genomic sequencing utilized a custom superHRD next-generation sequencing panel, and HRD scores were calculated from 54,000 single-nucleotide polymorphisms using Kruskal-Wallis rank-sum tests and two cut-off points for analysis. Higher HRD scores correlated with advanced tumor stages, recurrence, and mutations in TP53 and ABCB1, while APC mutations were linked to lower HRD scores. Patients with high HRD scores had significantly shorter disease-free survival (p = 0.013) and a trend toward shorter overall survival (OS) (p = 0.005), particularly those not receiving adjuvant therapy. Conversely, HRD-high patients undergoing adjuvant therapy showed a trend toward longer OS (p = 0.015). Multivariate analysis identified HRD as an independent prognostic factor (hazard ratio = 2.814 for recurrence, p = 0.015). Validation with the TCGA dataset supported these findings. This study highlights the associations between HRD scores, clinical characteristics, and genomic mutations in ESCC, suggesting HRD as a potential prognostic biomarker. HRD assessment may aid in patient stratification and personalized treatment strategies, warranting further investigation to validate the therapeutic implications of HRD scores in ESCC.

Correlation between real-world progression-free survival and other outcomes among patients with ovarian cancer who received poly(ADP-ribose) polymerase inhibitors in the first-line maintenance setting

Correlation between real-world progression-free survival and other outcomes among patients with ovarian cancer who received poly(ADP-ribose) polymerase inhibitors in the first-line maintenance setting

Combinatorial PARP and HDAC inhibition synergistically promotes cell death and overcomes cisplatin treatment tolerance in cervical cancer cell lines

Combinatorial PARP and HDAC inhibition synergistically promotes cell death and overcomes cisplatin treatment tolerance in cervical cancer cell lines

Adavosertib in Combination with Olaparib in Patients with Refractory Solid Tumors: An Open-Label, Dose-Finding, and Dose-Expansion Phase Ib Trial.

Adavosertib is a first-in-class, selective small-molecule inhibitor of Wee1. Olaparib is an inhibitor of poly(ADP-ribose) polymerase (PARP). Preclinical data suggest that adavosertib enhances the antitumor effect of PARP inhibitors. The safety, tolerability, and efficacy of adavosertib plus olaparib were evaluated in patients with refractory solid tumors to define the maximum tolerated dose (MTD) and recommended phase II dose (RP2D). Eligible patients in part A (dose finding) had a refractory solid tumor for which there is no established treatment and had received ≥ 1 prior course of systemic therapy; in part B (dose expansion), patients had platinum-sensitive extensive-stage or relapsed small-cell lung cancer (SCLC). Patients received adavosertib [once (qd) or twice daily (bid)] for 3 consecutive days with 4 days off treatment (3/4), or 5 consecutive days with 2 days off (5/2), plus olaparib (bid) for 14 or 21 days of a 21-day cycle. A total of 130 patients were enrolled in the study, 120 in part A and 10 in part B. The MTD for adavosertib bid was 175 mg (days 1-3, 8-10/21-day cycle) plus continuous olaparib 200 mg bid; the once-daily MTD (and RP2D) was adavosertib 200 mg (days 1-3, 8-10/21-day cycle) plus continuous olaparib 200 mg bid. In the MTD/RP2D cohort, one patient (7%) experienced a dose-limiting toxicity (DLT) of thrombocytopenia. The most common treatment-related adverse events (TRAEs) in the cohorts in which MTD/RP2D for bid dosing and RP2D for qd dosing were determined were fatigue (64.3% and 15.4%, respectively), diarrhea (42.9% and 30.8%), decreased appetite (35.7% and 23.1%), nausea (35.7% and 15.4%), and anemia (35.7% and 38.5%). In the SCLC dose-expansion cohort, TRAEs occurred in eight patients (88.9%), including thrombocytopenia (66.7%) and anemia (55.6%). In part A, objective response rate (ORR) was 14.8% [95% confidence interval (CI) 8.7-22.9] overall; for the cohorts in which MTD/RP2D for bid dosing and RP2D for qd dosing were determined, ORR was 30.8% (9.1-61.4) and 9.1% (0.2-41.3), respectively. ORR was 11.1% [95% CI 0.3-48.2; one partial response (PR)], disease control rate was 22.2% (2.8-60.0; one PR, one stable disease), and median progression-free survival was 1.5 months (1.3-4.2) in the SCLC dose-expansion cohort. Adverse events and DLTs observed in the bid MTD and once-daily MTD/RP2D dosing schedules were manageable and consistent with known adavosertib and olaparib safety profiles. Limited antitumor activity was observed with adavosertib plus olaparib combination therapy. ClinicalTrials.gov, NCT02511795 (registration: 28 July 2015).

Ovarian cancer biomarker testing over time in the era of PARP inhibitors

Ovarian cancer biomarker testing over time in the era of PARP inhibitors

Real-world BRCA1/2 and homologous recombination deficiency testing dynamics and time to treatment discontinuation on PARP inhibitor first-line maintenance among patients with epithelial ovarian cancer

Real-world BRCA1/2 and homologous recombination deficiency testing dynamics and time to treatment discontinuation on PARP inhibitor first-line maintenance among patients with epithelial ovarian cancer

P099 Effect of the PARP inhibitor talazoparib in combination with radiation and enzalutamide in prostate cancer cell models

P099 Effect of the PARP inhibitor talazoparib in combination with radiation and enzalutamide in prostate cancer cell models