PARP Inhibitors: Clinical Relevance, Mechanisms of Action and Tumor Resistance

Ophthalmologic toxicities of antineoplastic agents in genitourinary cancers: Mechanisms, management, and clinical implications

Genitourinary cancers affect over 480,000 patients in the United States annually. While promising therapeutic modalities continue to emerge, notably immune checkpoint inhibitors, molecular targeted therapies, antibody-drug conjugates, and radioligand therapies, these treatments are associated with a spectrum of adverse side-effects, including ophthalmologic toxicities. In this review, we cover the most commonly used antineoplastic agents for the kidneys, bladder, urinary tracts, prostate, testis, and penis, detailing mechanism, indication, and recent trials supporting their use. For each category of antineoplastic therapy, we describe the epidemiology, management, and clinical presentation, of common ophthalmologic toxicities stemming from these agents. This review serves to augment awareness and recognition of possible ophthalmologic manifestations resulting from the use of antineoplastic agents in genitourinary malignancy. Early identification of these side effects can hasten ophthalmology referral and ultimately improve visual outcomes in patients experiencing medication-induced ocular toxicities.

Cardio-oncology Drug Interactions: A Primer for Clinicians on Select Cardiotoxic Oncologic Therapies

Cardio-oncology is an emerging multidisciplinary field intended to mitigate and manage cardiovascular side effects and risks associated with cancer therapies. Clinician awareness of drug interaction management among cancer treatments, cardiovascular medications, and supportive care agents is important for optimizing efficacy and safety. Historically, chemotherapies have been associated with pharmacodynamic interactions with few, but important, pharmacokinetic interactions. The advent of oral targeted inhibitors has introduced more complex pharmacokinetic interactions, especially via cytochrome P450 pathways. Given the accelerated development of oncology therapies, clinicians need to be familiar with reviewing multiple sources for interaction information as well as adjusting and monitoring regimens when contending with drug interaction challenges.

Low dose DNA methyltransferase inhibitors potentiate PARP inhibitors in homologous recombination repair deficient tumors

BACKGROUND

Poly (ADP-Ribose) polymerase inhibitors are approved for treatment of tumors with BRCA1/2 and other homologous recombination repair (HRR) mutations. However, clinical responses are often not durable and treatment may be detrimental in advanced cancer due to excessive toxicities. Thus we are seeking alternative therapeutics to enhance PARP-directed outcomes. In an effort to expand the clinical use of PARP inhibitors to HRR proficient tumors, several groups have tested combinations of DNA methyltransferase inhibitors and PARP inhibitors. While this approach attenuated tumor cell proliferation in preclinical studies, subsequent clinical trials revealed little benefit. We hypothesized that benefit for this drug combination would only be specific to HRR deficient tumors, due to their inability to enact high fidelity DNA repair with subsequent cell death.

METHODS

We generated hypomorphic BRCA1 and BRCA2 variants of the HRR proficient triple negative breast cancer cell line MDA-MB-231. We compared therapeutic response features such as RAD51 focus formation, cell cycle fraction alterations, DNA damage accumulation, colony formation, and cell death of these and other cell lines with and without intrinsic BRCA1/2 mutations. Results were confirmed in BRCA1/2 intact and deficient xenografts and PDX.

RESULTS

Our targeted variants and cells with intrinsic BRCA1/2 mutations responded to low dose combination therapeutic treatment by G2M stalling, compounded DNA damage, severely attenuated colony formation, and importantly, increased cell death. In contrast, the parental MDA-MB-231 cells and other HRR proficient cell lines produced smaller cell populations with short term treatment, but with much less cumulative DNA damage, and minimal cell death. In animal studies, our BRCA-engineered hypomorphs and several independent PDX models with clinically relevant BRCA mutations were acutely more vulnerable to this drug combination.

CONCLUSIONS

We conclude that low dose DNA methyltransferase inhibition can cooperate with low dose PARP inhibition to increase DNA damage predominantly in cells with HRR deficiencies, ultimately producing more cell death than in HRR proficient tumors. We predict that clinical benefit will more likely be apparent in patients with DNA repair defective tumors and are focusing clinical exploration of this drug combination in these patients, with the goals of enhancing tumor cell death at minimal toxicities.

Transition State Analogs of Human DNPH1 Reveal Two Electrophile Migration Mechanisms

DNPH1 is responsible for eliminating the epigenetically modified nucleotide, 5-hydroxymethyl-2'-deoxyuridine 5'-monophosphate (hmdUMP), preventing formation of hmdUTP, a mutation-inducing nucleotide. Loss of DNPH1 activity sensitizes PARP inhibition-resistant BRCA-deficient cancers by causing incorporation of hmdUTP into DNA. Hydrolysis of hmdUMP by DNPH1 proceeds through a covalent intermediate between Glu104 and 2-deoxyribose 5-phosphate, followed by hydrolysis, a reaction cycle with two transition states. We describe synthesis and characterization of transition state mimics for both transition states of DNPH1. Both transition states prefer inhibitors with cationic charge at the anomeric center and provide a foundation for inhibitor design. Ground-state complexes show reaction coordinate nucleophiles poised 3.3-3.7 Å from the anomeric carbon while transition state analogs tighten the reaction coordinate to place the nucleophiles 2.7-2.8 Å from the anomeric carbon. Crystal structures of DNPH1 with transition state analogs reveal transition states where the electrophilic ribocation migrates between the leaving groups and attacking nucleophiles.

Targeting the 8-oxodG Base Excision Repair Pathway for Cancer Therapy

Genomic integrity is critical for cellular homeostasis, preventing the accumulation of mutations that can drive diseases such as cancer. Among the mechanisms safeguarding genomic stability, the Base Excision Repair (BER) pathway plays a pivotal role in counteracting oxidative DNA damage caused by reactive oxygen species. Central to this pathway are enzymes like 8-oxoguanine glycosylase 1 (OGG1), which recognize and excise 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG) lesions, thereby initiating a series of repair processes that restore DNA integrity. BER inhibitors have recently been identified as a promising approach in cancer therapy, increasing the sensitivity of cancer cells to radiotherapy and chemotherapy. By exploiting tumor-specific DNA repair dependencies and synthetic lethal interactions, these inhibitors could be used to selectively target cancer cells while sparing normal cells. This review provides a robust reference for scientific researchers, offering an updated perspective on small-molecule inhibitors targeting the 8-oxodG-BER pathway and highlighting their potential role in expanding cancer treatment strategies.

Opportunities for predictive proteogenomic biomarkers of drug treatment sensitivity in epithelial ovarian cancer

Genomic analysis has played a significant role in the identification of driver mutations that are linked to disease progression and response to drug treatment in ovarian cancer. A prominent example is the stratification of epithelial ovarian cancer (EOC) patients with homologous recombination deficiency (HRD) characterized by mutations in DNA damage repair genes such as BRCA1/2 for treatment with PARP inhibitors. However, recent studies have shown that some epithelial ovarian tumors respond to PARP inhibitors irrespective of their HRD or BRCA mutation status. An exclusive focus on the genome overlooks the significant insight that can be gained from other biological analytes, including proteins, which carry out cellular functions. Proteogenomics is the integration of genomics, transcriptomics, epigenomics and proteomics data. This review paper provides novel insight into the role of proteogenomics as an analytical approach to identify predictive biomarkers of drug treatment response in epithelial ovarian cancer. Proteogenomic analysis can facilitate the identification of predictive biomarkers of drug treatment response, consequently greatly improving the stratification of patients with EOC for treatment towards a goal of personalized medicine.

Downregulation and inhibition of TRPM2 calcium channel prevent oxidative stress-induced endothelial dysfunction in the EA.hy926 endothelial cells model - Preliminary studies

PURPOSE

Proper functioning of the endothelial barrier is crucial for cardiovascular system homeostasis. Oxidative stress can lead to endothelial dysfunction (ED), damaging lipids, proteins, and DNA. Reactive oxygen species also increase cytoplasmic Ca2+ levels, activating transient receptor potential melastatin 2 (TRPM2), a membrane non-selective calcium channel. The study aimed to assess TRPM2's significance in vascular endothelial cells' response to oxidative stress and the potential use of TRPM2 direct and indirect inhibitors in the prevention of oxidative stress-induced ED.

MATERIALS AND METHODS

EA.hy926 endothelial cells were exposed to hydrogen peroxide for 24 ​h to mimic oxidative stress conditions. To assess the significance of TRPM2 in the response of EA.hy926 ​cells to hydrogen peroxide TRPM2 siRNA as well as direct (N-(p-Amylcinnamoyl)anthranilic acid, flufenamic acid) and indirect (3-aminobenzamide, 3,4-dihydro-5[4-(1-piperidinyl)butyl]-1(2H)-isoquinolinone) TRPM2 inhibitors were tested.

RESULTS

Results showed that hydrogen peroxide-induced ED is alleviated by TRPM2 downregulation. Moreover, preincubation of cells with both direct and indirect TRPM2 inhibitors for 30 ​min before hydrogen peroxide treatment reduces its negative effects on cell viability, cell migration, and junctional proteins.

CONCLUSIONS

The obtained results suggest that TRPM2 channel may be a potential target in therapy and prevention of cardiovascular diseases connected with oxidative stress-induced ED. However, further research is needed for clinical applications of direct and indirect TRPM2 inhibitors.

Efficacy and safety of PARP inhibitors in prostate cancer: An umbrella review of systematic reviews and meta-analyses

Prostate cancer is a significant cause of cancer-related deaths in men. Poly (ADP-ribose) polymerase inhibitors (PARPi) have been shown to improve progression-free survival, especially in patients with BRCA1/2 mutations and deficiencies in homologous recombination repair (HRR). We conducted systematic reviews and meta-analyses and found that PARPi, combined with androgen receptor inhibitors, significantly improved overall survival (OS) and progression-free survival (PFS) in BRCA1/2-mutant and HRR-deficient patients. PARPi therapies increased the incidence of adverse events (AEs), including fatigue, nausea, anemia, neutropenia, and thrombocytopenia. Among different PARP inhibitors, Olaparib, Talazoparib, and Rucaparib demonstrated the strongest efficacy in improving OS and PFS but were also linked to higher rates of AEs. Combination therapies with PARPi and hormonal treatments proved more effective than monotherapy, especially in genetically targeted subgroups like BRCA1/2-mutant patients. This umbrella review demonstrates that PARPi treatment significantly improves clinical outcomes, particularly in BRCA1/2-mutant and HRR-deficient mCRPC patients.

Claudin-4 Stabilizes the Genome via Nuclear and Cell-Cycle Remodeling to Support Ovarian Cancer Cell Survival

SIGNIFICANCE

High-grade serous ovarian carcinoma is marked by chromosomal instability, which can serve to promote disease progression and allow cancer to evade therapeutic insults. The report highlights the role of claudin-4 in regulating genomic instability and proposes a novel therapeutic approach to exploit claudin-4-mediated regulation.

Interaction of RECQL4 with poly(ADP-ribose) is critical for the DNA double-strand break response in human cells

To overcome genotoxicity, cells have evolved powerful and effective mechanisms to detect and respond to DNA lesions. RecQ Like Helicase-4 (RECQL4) plays a vital role in DNA damage responses. RECQL4 is recruited to DNA double-strand break (DSB) sites in a poly(ADP-ribosyl)ation (PARylation)-dependent manner, but the mechanism and significance of this process remain unclear. Here, we showed that the domain of RECQL4 recruited to DSBs in a PARylation-dependent manner directly interacts with poly(ADP-ribose) (PAR) and contains a PAR-binding motif (PBM). By replacing this PBM with a PBM of hnRNPA2 or its mutated form, we demonstrated that the PBM in RECQL4 is required for PARylation-dependent recruitment and the roles of RECQL4 in the DSB response. These results suggest that the direct interaction of RECQL4 with PAR is critical for proper cellular response to DSBs and provide insights to understand PARylation-dependent control of the DSB response and cancer therapeutics using PARylation inhibitors.

NSC-3852 synergistically enhances the cytotoxicity of olaparib in oral squamous cell carcinoma

The PARP inhibitor olaparib is an anti-cancer agent based on synthetic lethality that targets poly (ADP-ribose) polymerases. It is used as a therapeutic agent for breast, ovarian, pancreatic, and prostate cancers carrying BRCA1/2 mutations that cause deficiency in homologous recombination. In recent years, acquired resistance to PARP inhibitors has become a clinical problem in PARP inhibitor-treated patients. Meanwhile, the development of molecular targeted drugs for highly malignant oral cancers has not progressed, and effective treatment strategies are needed. In this study, we identified the histone deacetylase inhibitor NSC-3852 as a compound that synergistically enhances the effects of olaparib in oral squamous cell carcinoma cell lines. N-Acetyl-l-cysteine treatment partially recovered cell survival after co-treatment with olaparib and NSC-3852. Moreover, the combination of olaparib and NSC-3852 rapidly upregulated γH2AX at 2 h after treatment, and induced S-phase arrest and apoptosis at 24 h after treatment, suggesting that this combination induced apoptosis through accumulation of massive DNA damage. Taken together, these findings demonstrate that NSC-3852 is a sensitizer of olaparib and suggest that the combination of NSC-3852 and olaparib may be a useful therapeutic strategy for homologous recombination-proficient cancers, including cancers with acquired resistance to olaparib and high-grade oral squamous cell carcinoma.

Novel inhibitors of PARP1 and PARP14: design, synthesis, and potentiation of cisplatin efficacy in cancer

BACKGROUND

Poly(ADP-ribose) polymerase (PARP) is a superfamily of enzymes involved in cell survival. Both PARP1 and PARP14 are overexpressed in malignancies. No clinically approved PARP14 inhibitors are available, and PARP1 inhibitors are generally nonspecific, resulting in a need for a more diverse library of selective PARP1 and PARP14 inhibitors.

MATERIALS AND METHODS

Based on the previous lead compounds 1 and 2, 26 novel compounds were designed, synthesized, and screened against PARP1 and PARP14. Compounds with the best in vitro inhibitory results were further screened against PARP2, PARP3, PARP5a, PARP7, and PARP15.

RESULTS AND CONCLUSION

The 26 novel compounds demonstrated a lesser inhibitory effect than the lead compounds. Compounds 1 and 2 were further investigated using in vitro cell viability assays, which revealed that cells treated with either lead PARP inhibitor and cisplatin in combination had significantly lower survival rates than those treated with cisplatin alone. At 10 µM, the combination showed more significant cell survival reduction, suggesting greater inhibition of PARP increases lethality, particularly in HeLa and PC-3 cell lines at 96 h and beyond.

[Metastatic castration-resistant prostate cancer and PARP inhibitors: From tumor genomics to new therapeutic combinations]

Castration-resistant metastatic prostate cancer remains lethal and a therapeutic challenge. Current strategies are geared towards the personalization of treatments based on the identification of relevant molecular targets, including genomic alterations involved in tumoral processes. Among these novel targeted therapies, poly-ADP-ribose polymerase inhibitors (PARPi), by blocking the action of enzymes involved in deoxyribonucleic acid (DNA) repair, induce the destruction of cells carrying defects in homologous recombination repair, often associated with alterations in genes involved in this mechanism. Thus, determining the presence of a molecular anomaly, particularly alterations in the BRCA1/2 genes, is a prerequisite for initiating PARPi monotherapy. In patients with metastatic castration-resistant prostate cancer , around 20-30 % carry this type of mutation. In this population, single-agent studies have demonstrated PARPi ability to prolong overall survival, and to improve symptom control, including pain. Other studies are underway to assess their effectiveness in combination with other therapies, and it already appears that association with new-generation hormone therapy can further prolong radiological progression-free survival, regardless of the mutation status of the genes involved in DNA repair, indicating a synergistic action between PARPi and new-generation hormone therapy.

Evaluation of the Oncomine Comprehensive Assay Plus NGS Panel and the OncoScan CNV Assay for Homologous Recombination Deficiency Detection

INTRODUCTION

Testing for homologous recombination deficiency (HRD) as a biomarker in relation to poly (ADP-ribose) polymerase inhibitor (PARPi) treatment in ovarian cancer is done by sequencing of the BRCA1/2 genes and/or by assessing a genomic instability signature. Here we present data obtained with two different methods for genomic instability testing: the Oncomine™ Comprehensive Assay Plus (OCA Plus) NGS panel and the OncoScan CNV assay.

METHODS

The retrospective analytical study included 80 ovarian cancer samples of patients previously referred to clinical Myriad testing (reference cohort), and 50 ovarian cancer samples from patients collected as part of the Pelvic Mass study. OCA Plus NGS libraries were sequenced with the Ion S5™XL Sequencer and analyzed with the Ion Reporter™ Software v5.20 for calculation of the genomic instability metric (GIM). In addition, all samples were tested with the OncoScan CNV FFPE Assay and analyzed with a previously published R-algorithm for generation of an in-house genomic instability score (in-house GIS).

RESULTS

The OCA Plus assay had a concordance to the reference of 89% on samples with a tumor fraction ≥ 30% (auto-calculated or via molecular estimation). A total of 15 samples in the reference cohort had a calculated tumor fraction < 30% in the OCA Plus assay. In these, the concordance to reference was only 60%. For the OncoScan CNV in-house GIS a local cutoff point of ≥ 50 was calculated. This gave a concordance to the reference of 85%, with 91% of the samples in the reference cohort passing quality control (QC) on tumor fraction. Both assays had a high sensitivity for the detection of genomic instability in samples with pathogenic or likely pathogenic BRCA1/2 mutations, with 12/13 being GIM positive (OCA Plus assay) and 13/13 being in-house GIS positive (OncoScan CNV assay).

CONCLUSIONS

The OCA Plus assay and the OncoScan CNV assay show a high but not complete concordance to reference standard homologous recombination deficiency (HRD) detection. The main reason for QC failure or non-concordance in our study was a low tumor fraction estimated in the assay, despite the selection of material by a pathologist with an inclusion criterion of > 30% tumor. QC steps should include careful tumor content evaluation, and results on samples with < 30% tumor should not be reported.

A multiparametric screen uncovers FDA-approved small molecules that potentiate the nuclear mechano-dysfunctions in ATR-defective cells

Targeting nuclear mechanics is emerging as a promising therapeutic strategy for sensitizing cancer cells to immunotherapy. Inhibition of the mechano-sensory kinase ATR leads to mechanical vulnerability of cancer cells, causing nuclear envelope softness and collapse and activation of the cGAS-STING-mediated innate immune response. Finding novel compounds that interfere with the non-canonical role of ATR in controlling nuclear mechanics presents an intriguing therapeutic opportunity. We carried out a multiparametric high-content screen to identify small molecules that affect nuclear envelope shape and to uncover novel players that could either ameliorate or further compromise the nuclear mechanical abnormalities of ATR-defective cells. The screen was performed in HeLa cells genetically depleted for ATR. Candidate hits were also tested in combination with the chemical inhibition of ATR by AZD6738, and their efficacy was further validated in the triple-negative breast cancer cell lines BT549 and HCC1937. We show that those compounds enhancing the abnormal nuclear shape of ATR-defective cells also synergize with AZD6738 to boost the expression of interferon-stimulated genes, highlighting the power of multiparametric screens to identify novel combined therapeutic interventions targeting nuclear mechanics for cancer immunotherapy.

Cost-Effectiveness of PARP Inhibitors for Patients with BRCA1/2-Positive Metastatic Castration-Resistant Prostate Cancer-The Canadian Perspective

BACKGROUND/OBJECTIVES

Through phase III clinical trials, PARP inhibitors have demonstrated outcome improvements in mCRPC patients with alterations in BRCA1/2 genes who have progressed on a second-generation androgen receptor pathway inhibitor (ARPI). While improving outcomes, PARP inhibitors contribute to the ever-growing economic burden of PCa. The objective of this project is to evaluate the cost-effectiveness of PARP inhibitors (olaparib, rucaparib, or talazoparib) versus the SOC (docetaxel or androgen receptor pathway inhibitors (ARPI)) for previously progressed mCRPC patients with BRCA1/2 mutations from the Canadian healthcare system perspective.

METHODS

Partitioned survival models were created to represent mCRPC disease after progression until death. Survival inputs for BRCA1/2-mutated patients were extracted from the PROfound, TRITON3, and TALAPRO-1 clinical trials, while Canadian-specific costs are presented in 2023 dollars. Upon progression, patients were treated with chemotherapy. The considered time horizon was 5 years and outcomes were discounted at 1.5% per year.

RESULTS

PARP inhibitors provide an additional survival of 0.19 quality-adjusted life years (QALY) when compared to the current standard of care, with additional costs of CAD 101,679 resulting in an incremental cost-utility ratio (ICUR) of CAD 565,383/QALY. The results were most sensitive to PARP inhibitors' acquisition costs and health-state utilities. PARP inhibitors required price reductions of up to 83% to meet the CAD 50,000/QALY willingness-to-pay threshold (WTP).

CONCLUSIONS

While providing survival benefits to previously progressed mCRPC patients presenting deleterious BRCA1/2 gene mutations, PARP inhibitors are not cost-effective and require major price reductions to reach local WTP thresholds.

Hematopoietic adverse events associated with PARP inhibitors: A FAERS database study

OBJECTIVES

Analyze hematopoietic ADR signals of PARP inhibitors (Olaparib, Niraparib, Rucaparib, Talazoparib) using FAERS data to inform clinical practice.

METHODS

Extracted ASCII data for these drugs from Q1 2019 to Q2 2024. Employed SMQ and PT for standardization. Screened ADR signals via ROR, PRR, and MHRA method, comparing SMQ ratios.

RESULTS

Hematopoietic ADRs peaked within 30 days post-treatment, with cytopenia and leukopenia most prevalent. Niraparib showed the highest adverse event count and signal intensity. Olaparib and Talazoparib also indicated strong hematotoxicity.

CONCLUSION

PARP inhibitors vary in ADR incidence and duration, necessitating personalized treatment plans for optimized safety and rational use.

Patient Selection for the Use of Niraparib in Advanced Ovarian Cancer: A Review

The advent of poly(ADP-ribose) polymerase (PARP) inhibitors has resulted in a significant paradigm shift in ovarian cancer treatment. Niraparib, a potent PARP inhibitor, has demonstrated substantial efficacy in both first-line and recurrent disease settings. By targeting homologous recombination DNA repair, a pathway frequently disrupted in ovarian cancer, particularly in the context of BRCA mutations, niraparib induces synthetic lethality. Pivotal clinical trials, including PRIMA, ENGOT-OV16/NOVA, and QUADRA, have solidified niraparib's role in the treatment paradigm. While sharing a common mechanism of action with other PARP inhibitors, niraparib exhibits a distinct toxicity profile. Notably, hematologic toxicities, particularly thrombocytopenia, and hypertension have been observed at Grade 3-4 levels. A comprehensive understanding of niraparib's efficacy and safety is essential for optimal patient selection and management.

Drug repurposing screen targeting PARP identifies cytotoxic activity of efavirenz in high-grade serous ovarian cancer

Drug repurposing has potential to improve outcomes for high-grade serous ovarian cancer (HGSOC). Repurposing drugs with PARP family binding activity may produce cytotoxic effects through the multiple mechanisms of PARP including DNA repair, cell-cycle regulation, and apoptosis. The aim of this study was to determine existing drugs that have PARP family binding activity and can be repurposed for treatment of HGSOC. In silico ligand-based virtual screening (BLAZE) was used to identify drugs with potential PARP-binding activity. The list was refined by dosing, known cytotoxicity, lipophilicity, teratogenicity, and side effects. The highest ranked drug, efavirenz, progressed to in vitro testing. Molecularly characterized HGSOC cell lines, 3D hydrogel-encapsulated models, and patient-derived organoid models were used to determine the IC50 for efavirenz, cell death, apoptosis, PARP1 enzyme expression, and activity in intact cancer cells following efavirenz treatment. The IC50 for efavirenz was 26.43-45.85 μM for cells in two dimensions; 27.81 μM-54.98 μM in three dimensions, and 14.52 μM-42.27 μM in HGSOC patient-derived organoids. Efavirenz decreased cell viability via inhibition of PARP; increased CHK2 and phosphor-RB; increased cell-cycle arrest via decreased CDK2; increased γH2AX, DNA damage, and apoptosis. The results of this study suggest that efavirenz may be a viable treatment for HGSOC.

UBA1 inhibition sensitizes cancer cells to PARP inhibitors

Therapeutic strategies targeting the DNA damage response, such as poly (ADP-ribose) polymerase (PARP) inhibitors (PARPi), have revolutionized cancer treatment in tumors deficient in homologous recombination (HR). However, overcoming innate and acquired resistance to PARPi remains a significant challenge. Here, we employ a genome-wide CRISPR knockout screen and discover that the depletion of ubiquitin-activating enzyme E1 (UBA1) enhances sensitivity to PARPi in HR-proficient ovarian cancer cells. We show that silencing or pharmacological inhibition of UBA1 sensitizes multiple cell lines and organoid models to PARPi. Mechanistic studies uncover that UBA1 inhibition not only impedes HR repair to sensitize cells to PARP inhibition but also increases PARylation, which may subsequently be targeted by PARP inhibition. In vivo experiments using patient-derived xenografts demonstrate that combining PARP and UBA1 inhibition provided significant survival benefit compared to individual therapies with no detectable signs of toxicity, establishing this combination approach as a promising strategy to extend PARPi benefit.

Endothelial Dysfunction Markers in Ovarian Cancer: VTE Risk and Tumour Prognostic Outcomes

Ovarian cancer (OC) presents daunting lethality rates worldwide, with frequent late-stage diagnosis and chemoresistance, highlighting the need for improved prognostic approaches. Venous thromboembolism (VTE), a major cancer mortality factor, is partially driven by endothelial dysfunction (ED). ED's pro-inflammatory state fosters tumour progression, suggesting a VTE-independent link between ED and cancer. Given this triad's interplay, ED markers may influence OC behaviour and patients' prognosis. Thus, the impact of ED-related genes and single-nucleotide polymorphisms (SNPs) on OC-related VTE and patient thrombogenesis-independent prognosis was investigated. NOS3 upregulation was linked to lower VTE incidence (χ2, p = 0.013), while SELP upregulation was associated with shorter overall survival (log-rank test, p = 0.048). Dismissing patients with VTE before OC diagnosis, SELP rs6136 T allele carriers presented lower progression-free survival (log-rank test, p = 0.038). Nevertheless, due to the SNP minor allele underrepresentation, further investigation is required. Taken together, ED markers seem to exhibit roles that depend on the clinical context, such as tumour-related thrombogenesis or cancer prognosis. Validation with larger cohorts and more in-depth functional studies are needed for data clarification and potential therapeutic strategies exploitation to tackle cancer progression and thrombosis in OC patients.

Isoxazole compounds: Unveiling the synthetic strategy, in-silico SAR & toxicity studies and future perspective as PARP inhibitor in cancer therapy

Latest developments in cancer treatment have shed a light on the crucial role of PARP inhibitors that enhance the treatment effectiveness by modifying abnormal repair pathways. PARP inhibitors, such as Olaparib, Rucaparib, Niraparib, and Talazoparib have been approved in a number of cancers including BRCA 1/BRCA2 associated malignancies although there are many difficulties as therapeutical resistance. Besides the conventional synthetic drugs, natural compounds such as flavones and flavonoids have been found to be PARP inhibitors but only in preclinical studies. Isoxazole is very important class of potential candidates for medicinal chemistry with anti-cancer and other pharmacological activities. At present, there are no approved PARP inhibitors of isoxazole origin but their ability to hit many pathways inside the cancer cells points out on its importance for future treatments design. In drug development, isoxazoles are helpful because of the molecular design flexibility that may be enhanced using various synthetic approaches. This review highlights the molecular mechanisms of PARP inhibition, importance of isoxazole compounds and present advances in their synthetic strategies that demonstrate promise for these agents as new anticancer drugs. It emphasizes that isoxazole-based PARP inhibitors compounds could be novel anti-cancer drugs. Through this review, we hope to grow a curiosity in additional explorations of isoxazole-based PARP inhibitors and their applications in the trends of novel insights towards precision cancer therapy.

Kinetic Analysis and Metabolism of Poly(Adenosine Diphosphate-Ribose) Polymerase-1-Targeted 18F-Fluorthanatrace PET in Breast Cancer

The poly(adenosine diphosphate-ribose) polymerase inhibitors (PARPi) have demonstrated efficacy in ovarian, breast, and prostate cancers, but current biomarkers do not consistently predict clinical benefit. 18F-fluorthanatrace (18F-FTT) is an analog to rucaparib, a clinically approved PARPi, and is a candidate biomarker for PARPi response. This study intends to characterize 18F-FTT pharmacokinetics in breast cancer and optimize image timing for clinical trials. A secondary aim is to determine whether 18F-FTT uptake in breast cancer correlates with matched frozen surgical specimens as a reference standard for PARP-1 protein. Methods: Thirty prospectively enrolled women with a new diagnosis of breast cancer were injected with 18F-FTT and imaged dynamically 0-60 min after injection over the chest, with an optional static scan over multiple bed positions starting around 70 min. Kinetic analysis of lesion uptake was performed using blood-pool activity with population radiometabolite corrections. Normal breast and normal muscle reference tissue models were compared with PARP-1 protein expression in 10 patients with available tissue. Plasma radiometabolite concentrations and uptake in tumor and normal muscle were investigated in mouse xenografts. Results: Pharmacokinetics of 18F-FTT were well fit by Logan plot reference region models of reversible binding. However, fits of 2-tissue compartment models assuming negligible metabolite uptake were unstable. Rapid metabolism of 18F-FTT was demonstrated in mice, and similar uptake of radiometabolites was found in tumor xenografts and normal muscle. Tumor 18F-FTT distribution volume ratios relative to normal muscle reference tissue correlated with tissue PARP-1 expression (P < 0.02, n = 10). The tumor-to-normal muscle ratio from a 5-min frame between 50 and 60 min after injection, a potential static scan protocol, closely corresponded to the distribution volume ratio relative to normal muscle and correlated to PARP-1 expression (P < 0.02, n = 10). Conclusion: This study of PARPi analog 18F-FTT showed that uptake kinetics in vivo corresponded to expression of PARP-1 and that 18F-FTT quantitation is influenced by radiometabolites that are increasingly present late after injection. Radiometabolites can be controlled by using optimal image acquisition timing or normal muscle reference tissue modeling in dynamic imaging or a tumor-to-normal muscle ratio. Optimal image timing for tumor-to-normal muscle quantification in humans appears to be between 50 and 60 min after injection. Therefore, a clinically practical static imaging protocol commencing 45-55 min after injection may sufficiently balance 18F-FTT uptake with background clearance and radiometabolite interference for quantitative interpretation of PARP-1 expression in vivo.

The complex universe of inactive PARP1

Poly(ADP-ribose) polymerase 1 (PARP1) is a crucial member of the PARP family, which modifies targets through ADP-ribosylation and plays key roles in a variety of biological processes. PARP inhibitors (PARPis) hinder ADP-ribosylation and lead to the retention of PARP1 at the DNA lesion (also known as trapping), which underlies their toxicity. However, inhibitors and mutations that make PARP1 inactive do not necessarily correlate with trapping potency, challenging the current understanding of inactivation-caused trapping. Recent studies on mouse models indicate that both trapping and non-trapping inactivating mutations of PARP1 lead to embryonic lethality, suggesting the unexpected toxicity of the current inhibition strategy. The allosteric model, complicated automodification, and various biological functions of PARP1 all contribute to the complexity of PARP1 inactivation.

Alterations in the expression of homologous recombination repair (HRR) genes in breast cancer tissues considering germline BRCA1/2 mutation status

INTRODUCTION

Homologous recombination (HR) is a crucial DNA-repair mechanism, and its disruption can lead to the accumulation of mutations that initiate and promote cancer formation. The key HR genes, BRCA1 and BRCA2, are particularly significant as their germline pathogenic variants are associated with a hereditary predisposition to breast and/or ovarian cancer.

MATERIALS AND METHODS

The study was performed on 45 FFPE breast cancer tissues obtained from 24 and 21 patients, with and without the germline BRCA1/2 mutation, respectively. The expression of 11 genes: BRCA1, BRCA2, ATM, BARD1, FANCA, FANCB, FANCI, RAD50, RAD51D, BRIP1, and CHEK2 was assessed using Custom RT2 PCR Array (Qiagen), and results were analysed using R.

RESULTS

Cancer tissues from patients with BRCA1 or BRCA2 germline mutations displayed no significant differences in the expression of the selected HR genes compared to BRCA1 or BRCA2 wild-type cancer tissues. In BRCA1mut cancer tissues, BRCA1 expression was significantly higher than in BRCA2mut and BRCA wild-type cancer tissues.

CONCLUSIONS

In cancer tissues harbouring either BRCA1 or BRCA2 germline mutations, no significant differences in expression were observed at the mRNA level of any tested HR genes, except BRCA1. However, the significant differences observed in BRCA1 expression between germline BRCA1mut, germline BRCA2mut and BRCA1/2wt tissues may indicate a compensatory mechanism at the mRNA level to mitigate the loss of BRCA1 function in the cells.

Classification of anticancer drugs: an update with FDA- and EMA-approved drugs

Anticancer systemic therapy comprises a complex and growing group of drugs. Some of the new agents with novel mechanisms of action that have appeared are difficult to fit in the groups of classical chemotherapy, hormones, tyrosine-kinase inhibitors, and monoclonal antibodies. We propose a classification based on two levels of information: the site of action and the mechanism of action. Regarding the former, drugs can exert their action in the tumor cell, the tumor vasculature, the immune system, or the endocrine system. The mechanism of action refers to the molecular target.

Role of BRCA1 in glioblastoma etiology

BRCA1 (Breast Cancer 1) is a tumor suppressor gene with a role in DNA repair by Homologous Recombination (HR), and maintenance of genomic stability that is frequently investigated in breast, prostate, and ovarian cancers. BRCA1 mutations or dysregulation in glioblastoma can lead to impaired DNA repair mechanisms, resulting in tumor progression and resistance to standard therapies. Several studies have shown that BRCA1 expression is altered, albeit rarely, in glioblastoma, leading to poor prognosis and increased tumor aggressiveness. In addition, the communication of BRCA1 with other molecular pathways such as p53 and PTEN further complicates its role in glioblastoma pathogenesis. Targeting BRCA1-related pathways in these cases has shown the potential to improve the efficacy of standard treatments, including radiotherapy and chemotherapy. The development of (Poly (ADP-ribose) Polymerase) PARP inhibitors that exploit the lack of HR also offers a therapeutic approach to glioblastoma patients with BRCA1 mutations. Despite these advances, the heterogeneity of glioblastoma and its complex tumor microenvironment make the translation of such approaches into clinical practice still challenging, and there is an "unmet need". This review discusses the current mechanisms of etiology and potential treatment of BRCA1-related glioblastoma.

PARP inhibitors in testicular germ cell tumors: what we know and what we are looking for

Testicular germ cell tumors (TGCTs), the most common malignancies affecting young men, are characterized by high sensitivity to cisplatin-based chemotherapy, which leads to high cure rates even in metastatic disease. However, approximately 30% of patients with metastatic TGCTs relapse after first-line treatment and those who can be defined as platinum-refractory patients face a very dismal prognosis with only limited chemotherapy-based treatment options and an overall survival of few months. Hence, to understand the mechanisms underlying cisplatin resistance is crucial for developing new treatment strategies. This narrative review explores the potential role of PARP inhibitors (PARPis) in overcoming cisplatin resistance in TGCTs, starting from the rationale of their ability to induce DNA damage in cells with homologous recombination repair (HRR). Thus far, PARPis have failed to show meaningful clinical activity in platinum-refractory TGCT patients, either alone or in combination with chemotherapy. However, few responses to PARPis in TGCTs have been detected in patients with BRCA1/2, ATM or CHEK2 mutations, reinforcing the idea that patients should be optimally selected for tailored treatments in the era of personalized medicine. Future preclinical and clinical research is needed to further investigate the molecular mechanisms of cisplatin resistance and to identify novel therapeutic strategies in resistant/refractory TGCTs patients.

Mathematical modeling framework enhances clinical trial design for maintenance treatment in oncology

Clinical trials are costly and time-intensive endeavors, with a high rate of drug candidate failures. Moreover, the standard approaches often evaluate drugs under a limited number of protocols. In oncology, where multiple treatment protocols can yield divergent outcomes, addressing this issue is crucial. Here, we present a computational framework that simulates clinical trials through a combination of mathematical and statistical models. This approach offers a means to explore diverse treatment protocols efficiently and identify optimal strategies for oncological drug administration. We developed a computational framework with a stochastic mathematical model as its core, capable of simulating virtual clinical trials closely recapitulating the clinical scenarios. Testing our framework on the landmark SOLO-1 clinical trial investigating Poly-ADP-Ribose Polymerase maintenance treatment in high-grade serous ovarian cancer, we demonstrate that managing toxicity through treatment interruptions or dose reductions does not compromise treatment's clinical benefits. Additionally, we provide evidence suggesting that further reduction of hematological toxicity could significantly improve the clinical outcomes. The value of this computational framework lies in its ability to expedite the exploration of new treatment protocols, delivering critical insights pivotal to shaping the landscape of upcoming clinical trials.

Angiopoietin-like protein 8 directs DNA damage responses towards apoptosis by stabilizing PARP1-DNA condensates

Upon genotoxic stresses, cells employ various DNA damage responses (DDRs), including DNA damage repair or apoptosis, to safeguard genome integrity. However, the determinants among different DDRs choices are largely unknown. Here, we report angiopoietin-like protein 8 (ANGPTL8), a secreted regulator of lipid metabolism, localizes to the nucleus and acts as a dynamic switch that directs DDRs towards apoptosis rather than DNA repair after genotoxin exposure. ANGPTL8 deficiency alleviates DNA damage and apoptosis in cells exposed to genotoxins, as well as in the liver or kidney of mice injured by hepatic ischemia/reperfusion or cisplatin treatment. Mechanistically, ANGPTL8 physically interacts with Poly (ADP-ribose) polymerase 1 (PARP1), in a PARylation-independent manner, and reduces the fluidity of PARP1-DNA condensates, thereby enhancing the pro-apoptotic accumulation of PARP1 and PAR chains on DNA lesions. However, the transcription of ANGPTL8 is gradually decreased following genotoxin treatment, partly due to downregulation of CCAAT enhancer binding protein alpha (CEBPA), presumably to avoid further cytotoxicity. Together, we provide new insights by which genotoxic stress induced DDRs are channeled to suicidal apoptosis to safeguard genome integrity.

Poly (ADP-ribose) polymerase inhibitor sensitized DNA damage caused by an alkylating pyrrole-imidazole polyamide targeting MYCN in neuroblastoma cells

MYCN amplification (MYCN-amp) is a significant prognostic factor and early genetic marker of high-risk neuroblastoma (NB). MYCN induces the DNA damage response (DDR) and modulates the insensitivity of NB cells to Poly (ADP-ribose) polymerase (PARP) inhibitors. We previously reported that CCC-002, a DNA-alkylating agent conjugated with pyrrole-imidazole polyamide targeting MYCN, inhibits NB cell proliferation and induces DNA damage signaling. In this study, we investigated the synergistic effects of CCC-002 and PARP inhibitors on MYCN-amp NB cells. Combination treatment with PARP inhibitors significantly enhanced the sensitivity of MYCN-amp NB cells to CCC-002. DNA damage signals, such as phosphorylation of H2AX and RPA32 elicited after CCC-002 treatment, were further enhanced by PARP inhibitors, as detected through western blotting and immunofluorescence analyses. The potent cytotoxicity of this combination treatment was confirmed by the significant increase in the subG0-G1 phase. Although MYCN knockdown showed no synergistic effect with PARP inhibitors, fluorescence in situ hybridization and quantitative PCR analyses indicated that PARP inhibitors enhanced the effect of CCC-002 to reduce MYCN copy number and suppress its expression. Overall, our study provides novel insights into a therapeutic approach that combines CCC-002 and PARP inhibition to effectively induce DNA damage and apoptosis in MYCN-amp NB cells.

Aminomethylmorpholino Nucleosides as Novel Inhibitors of PARP1 and PARP2: Experimental and Molecular Modeling Analyses of Their Selectivity and Mechanism of Action

Poly(ADP-ribose) polymerases 1 and 2 (PARP1 and PARP2) play a key role in DNA repair. As major sensors of DNA damage, they are activated to produce poly(ADP-ribose). PARP1/PARP2 inhibitors have emerged as effective drugs for the treatment of cancers with BRCA deficiencies. Here, we explored aminomethylmorpholino and aminomethylmorpholino glycine nucleosides as inhibitors of PARP1 and PARP2, using different enzymatic assays. The compounds bearing thymine or 5-Br(I)-uracil bases displayed the highest inhibition potency, with all of them being more selective toward PARP1. Interaction of the inhibitors with the NAD+ binding cavity of PARP1 (PARP2) suggested by the mixed-type inhibition was demonstrated by molecular docking and the RoseTTAFold All-Atom AI-model. The best PARP1 inhibitors characterized by the inhibition constants in the range of 12-15 µM potentiate the cytotoxicity of hydrogen peroxide by displaying strong synergism. The inhibitors revealed no impact on PARP1/PARP2 affinity for DNA, while they reduced the dissociation rate of the enzyme-DNA complex upon the autopoly(ADP-ribosyl)ation reaction, thus providing evidence that their mechanism of action for PARP trapping is due primarily to catalytic inhibition. The most active compounds were shown to retain selectivity toward PARP1, despite the reduced inhibition potency in the presence of histone PARylation factor 1 (HPF1) capable of regulating PARP1/PARP2 catalytic activity and ADP-ribosylation reaction specificity. The inhibitors obtained seem to be promising for further research as potential drugs.

SART1 modulates poly-(ADP-ribose) chain accumulation and PARP1 chromatin localization

PARP1 inhibitors (PARPis) are used for treatment of cancers with mutations in BRCA1 or BRCA2 that are deficient in homologous recombination. The identification of modulators of PARP1 activity is critical to understand and overcome resistance to PARPis. We integrated data from three omics-scale screens to discover new regulators of PARP1 activity. We identified SART1 and show that its silencing leads to an increase in poly-ADP ribosylation and chromatin-bound PARP1. SART1 is recruited to chromatin following DNA damage and limits PARP1 chromatin retention and activity. The SART1 N-terminus is sufficient to regulate the accumulation of PAR chains and PARP1 on chromatin, an activity dependent on the RGG/RG box. Silencing of SART1 leads to an increased sensitivity of cells to DNA damage induced by IR, irrespective of BRCA1 status and to PARPis only in absence of BRCA1. These results suggest that SART1 could be clinically utilized to improve PARPi efficacy.

Screening and design of PARP12 inhibitors from traditional Chinese medicine small molecules using computational modeling and simulation

The poly (ADP-ribose) polymerase (PARP) family of enzymes plays a pivotal role in orchestrating a multitude of cellular processes, including DNA repair mechanisms, transcriptional regulation, and modulation of immune responses. Within this family, PARP12 emerges as a noteworthy candidate for targeted cancer therapeutics. Consequently, this investigation endeavors to screen and design potential PARP12 inhibitors derived from traditional Chinese medicinal compounds by employing sophisticated molecular modeling and computational medicinal chemistry approaches. The compound RBN2397 is utilized as a benchmark, and the binding efficacies of the newly identified small molecules are assessed against a spectrum of criteria, encompassing molecular interactions, binding free energy, and extensive post-simulation analyses. The outcomes demonstrated that the identified small molecules, specifically tcm8650 and its derivative XC-1, possess remarkable binding affinities and exhibit reduced binding free energies compared to RBN2397. The molecular docking and interaction profiles of these compounds were also comprehensively scrutinized. Moreover, ADMET profiling meticulously evaluated the pharmacokinetic profiles and physicochemical characteristics of these promising molecules and their projected human physiological impact. These computational studies indicated their potential therapeutic applicability and predicted acceptable safety profile, advocating their further exploration as viable candidates in cancer treatment.

SMAD4 Limits PARP1 dependent DNA Repair to Render Pancreatic Cancer Cells Sensitive to Radiotherapy

Dysregulation of SMAD4 (i.e. somatic mutation) is strongly associated with poor pancreatic ductal adenocarcinoma (PDAC) prognosis, yet the molecular mechanisms remain underlying this relationship obscure. Previously, we discovered that SMAD4 mutation renders pancreatic cancer resistant to radiotherapy via promotion of autophagy. In the current work, we observed a downregulation of the protein level of SMAD4 in PDAC as compared with adjacent normal tissue, and that such SMAD4low PDAC failed to benefit from chemotherapy. Furthermore, we observed that SMAD4 depletion dramatically enhanced DNA repair capacity in response to irradiation (IR) or a radiomimetic chemical. Interestingly, we found the radiomimetic chemical having induced a robust translocation of SMAD4 into the nucleus, where a direct interaction was shown to occur between the MH1 domain of SMAD4 and the DBD domain of PARP1. Functionally, the SMAD4-PARP1 interaction was found to perturb the recruitment of PARP1 to DNA damage sites. Accordingly, the combination of olaparib and radiotherapy was indicated in vivo and in vitro to specifically reduce the growth of SMAD4-deficient PDAC by attenuating PARP1 activity. Collectively, our results revealed a novel molecular mechanism for the involvement of the SMAD4-PARP1 interaction in DNA repair with a vital role in radiotherapy response in PDAC. Based on our set of findings, our findings offer a new combined therapeutic strategy for SMAD4 deficient PDAC that can significantly reduce pancreatic cancer radiotherapy resistance.

Exploring the impact of BRCA1 and BRCA2 mutation type and location on Olaparib maintenance therapy in platinum-sensitive relapsed ovarian Cancer patients: A single center report

OBJECTIVE

In patients with platinum-sensitive relapsed ovarian cancer (PSROC) harboring pathogenic/likely pathogenic variants (PV) in BRCA1 and BRCA2 genes, olaparib maintenance monotherapy (OMT) is a viable option. Our study aimed to evaluate the impact of different BRCA1/2 PV in survival outcomes and safety of OMT in BRCA1/2-mutated PSROC patients, focusing on the type and location of PV.

METHODS

We assessed the outcomes of 100 BRCA1/2-mutated PSROC patients treated at our institute, analyzing progression-free survival (PFS) and overall survival (OS). Germline and tumor BRCA1/2 genotyping was conducted using Illumina's next-generation sequencing (NGS).

RESULTS

PFS and OS were significantly shorter in PSROC patients with PV in BRCA1 compared to those with PV in BRCA2 (PFS:14.0 vs. 38.8 months, p = 0.007, OS: 21.8 vs. 62.0 months, p = 0.011). Notably, there was a significant difference in PFS based on the intragenic location of BRCA1 PV, with shorter PFS in patients with 1st/2nd relapse, harboring PV in BRCA1 RING domain compared to those with PV in the DNA binding domain (DBD) and BRCT domains (12.4 vs. 23.0 months, p = 0.046). No differences in PFS and OS were observed between patients with germline versus somatic BRCA1/2 PV (PFS:14.9 vs.19.3, p = 0.316, OS: not reached vs. 25.8 months; p = 0.224). However, there were significant differences in the reasons for OMT discontinuation between patients with germline and somatic BRCA1/2 PV, primarily due to adverse side effects.

CONCLUSIONS

In summary, the type and location of BRCA1 and BRCA2 PV provide additional insight into the expected survival outcomes of olaparib MT in PSROC patients.

TRIAL REGISTRATION NUMBER

ISRCTN42408038, Name of registry: ISRCTN registry, Date of registration: 24/11/2015.

Poly (adenosine diphosphate-ribose) polymerase inhibitors in the treatment of triple-negative breast cancer with homologous repair deficiency

Breast cancer (BC) is a highly heterogeneous disease, and the presence of germline breast cancer gene mutation (gBRCAm) is associated with a poor prognosis. Triple-negative breast cancer (TNBC) is a BC subtype, characterized by the absence of hormone and growth factor receptor expression, making therapeutic decisions difficult. Defects in the DNA damage response pathway due to mutation in breast cancer genes (BRCA 1/2) lead to homologous recombination deficiency (HRD). However, in HRD conditions, poly (adenosine diphosphate-ribose) polymerase (PARP) proteins repair DNA damage and lead to tumor cell survival. Biological understanding of HRD leads to the development of PARP inhibitors (PARPi), which trap PARP proteins and cause genomic instability and tumor cell lysis. HRD assessment can be an important biomarker in identifying gBRCAm patients with BC who could benefit from PARPi therapy. HRD can be identified by homologous recombination repair (HRR) gene-based assays, genomic-scarring assays and mutational signatures, transcription and protein expression profiles, and functional assays. However, gold standard methodologies that are robust and reliable to assess HRD are not available currently. Hence, there is a pressing need to develop accurate biomarkers identifying HRD tumors to guide targeted therapies such as PARPi in patients with BC. HRD assessment has shown fruitful outcomes in chemotherapy studies and preliminary evidence on PARPi intervention as monotherapy and combination therapy in HRD-stratified patients. Furthermore, ongoing trials are exploring the potential of PARPi in BC and clinically complex TNBC settings, where HRD testing is used as an adjunct to stratify patients based on BRCA mutations.

Targeting DNA damage response in pancreatic ductal adenocarcinoma: A review of preclinical and clinical evidence

Pancreatic ductal adenocarcinoma (PDAC) is associated with one of the most unfavorable prognoses across all malignancies. In this review, we investigate the role of inhibitors targeting crucial regulators of DNA damage response (DDR) pathways, either as single treatments or in combination with chemotherapeutic agents and targeted therapies in PDAC. The most prominent clinical benefit of PARP inhibitors' monotherapy is related to the principle of synthetic lethality in individuals harboring BRCA1/2 and other DDR gene mutations as predictive biomarkers. Moreover, induction of BRCAness with inhibitors of RTKs, including VEGFR and c-MET and their downstream signaling pathways, RAS/RAF/MEK/ERK and PI3K/AKT/mTOR in order to expand the application of PARP inhibitors in patients without DDR mutations, has also been addressed. Other DDR-targeting agents beyond PARP inhibitors, including inhibitors of ATM, ATR, CHEK1/2, and WEE1 have also demonstrated their potential in preclinical models of PDAC and may hold promise in future studies.

PARP inhibitor-related acute renal failure: a real-world study based on the FDA adverse event reporting system database

BACKGROUND

Current clinical trial data on PARP inhibitors (PARPis)-related acute renal failure (ARF) are not entirely representative of real-world situations. Therefore, in this study, the US Food and Drug Administration Adverse Event Reporting System (FAERS) was used to evaluate PARPis-related ARF.

RESEARCH DESIGN AND METHODS

Data were obtained from 1 January 2015, to 30 September 2023. ARF event reports were analyzed based on four algorithms. The time-to-onset (TTO) and clinical outcomes of PARPis-associated ARF were assessed.

RESULTS

The total included cases were 2726. Significant signals were observed for olaparib, niraparib, and rucaparib (reporting odds ratio (ROR): 1.62, 95% confidence interval (CI): 1.49-1.78, 1.25, 95% CI: 1.19-1.32 and 1.59, 95% CI: 1.47-1.72 respectively). The median TTO of ARF onset was 57, 36, and 85 days for olaparib, niraparib, and rucaparib, respectively. The proportion of deaths with olaparib (9.88%) was significantly higher than for niraparib (2.52%) and rucaparib (2.94%) (p < 0.005). The proportion of life-threatening adverse events associated with niraparib (4.89%) was significantly higher than for rucaparib (0.98%) (p < 0.005).

CONCLUSIONS

ARF and PARPi were related, with the exception of talazoparib. More emphasis should be given to PARPis-related ARF due to the high proportion of serious AEs and delayed adverse reactions.

Positioning loss of PARP1 activity as the central toxic event in BRCA-deficient cancer

The mechanisms by which poly(ADP-ribose) polymerase 1 (PARP1) inhibitors (PARPi)s inflict replication stress and/or DNA damage are potentially numerous. PARPi toxicity could derive from loss of its catalytic activity and/or its physical trapping of PARP1 onto DNA that perturbs not only PARP1 function in DNA repair and DNA replication, but also obstructs compensating pathways. The combined disruption of PARP1 with either of the hereditary breast and ovarian cancer genes, BRCA1 or BRCA2 (BRCA), results in synthetic lethality. This has driven the development of PARP inhibitors as therapies for BRCA-mutant cancers. In this review, we focus on recent findings that highlight loss of PARP1 catalytic activity, rather than PARPi-induced allosteric trapping, as central to PARPi efficacy in BRCA deficient cells. However, we also review findings that PARP-trapping is an effective strategy in other genetic deficiencies. Together, we conclude that the mechanism-of-action of PARP inhibitors is not unilateral; with loss of activity or enhanced trapping differentially killing depending on the genetic context. Therefore, effectively targeting cancer cells requires an intricate understanding of their key underlying vulnerabilities.

The Role of Tumor Biomarkers in Tailoring the Approach to Advanced Ovarian Cancer

Growing evidence has demonstrated the role of mutations of tumor biomarkers in diagnosing and treating epithelial ovarian cancer. This review aims to analyze recent literature on the correlation between tumor biomarkers and chemotherapy in nonmucinous ovarian cancer, providing suggestions for personalized treatment approaches. An extensive literature search was conducted to identify relevant studies and trials. BRCA1/2 mutations are central in homologous recombination repair deficiency (HRD) in ovarian cancer, but several other genetic mutations also contribute to varying cancer risks. While the role of MMR testing in ovarian cancer is debated, it is more commonly linked to non-serous ovarian cancer, often associated with Lynch syndrome. A significant proportion of ovarian cancer patients have HRD, affecting treatment decisions in both first-line (especially in advanced stages) and second-line therapy due to HRD's connection with platinum-based therapy and PARP inhibitors' response. However, validated genetic tests to identify HRD have not yet been universally implemented. There is no definitive therapeutic algorithm for advanced ovarian cancer, despite ongoing efforts and multiple proposed tools. Future research should focus on expanding the utility of biomarkers, reducing resistance, and increasing the actionable biomarker pool.

Emerging Nanomedicine Approaches in Targeted Lung Cancer Treatment

Lung cancer, the leading cause of cancer-related deaths worldwide, is characterized by its aggressive nature and poor prognosis. As traditional chemotherapy has the disadvantage of non-specificity, nanomedicine offers innovative approaches for targeted therapy, particularly through the development of nanoparticles that can deliver therapeutic agents directly to cancer cells, minimizing systemic toxicity and enhancing treatment efficacy. VEGF and VEGFR are shown to be responsible for activating different signaling cascades, which will ultimately enhance tumor development, angiogenesis, and metastasis. By inhibiting VEGF and VEGFR signaling pathways, these nanotherapeutics can effectively disrupt tumor angiogenesis and proliferation. This review highlights recent advancements in nanoparticle design, including lipid-based, polymeric, and inorganic nanoparticles, and their clinical implications in improving lung cancer outcomes, exploring the role of nanomedicine in lung cancer diagnoses and treatment.

Targeting PARP-1 and DNA Damage Response Defects in Colorectal Cancer Chemotherapy with Established and Novel PARP Inhibitors

The DNA repair protein PARP-1 emerged as a valuable target in the treatment of tumor entities with deficiencies of BRCA1/2, such as breast cancer. More recently, the application of PARP inhibitors (PARPi) such as olaparib has been expanded to other cancer entities including colorectal cancer (CRC). We previously demonstrated that PARP-1 is overexpressed in human CRC and promotes CRC progression in a mouse model. However, acquired resistance to PARPi and cytotoxicity-mediated adverse effects limit their clinical applicability. Here, we detailed the role of PARP-1 as a therapeutic target in CRC and studied the efficacy of novel PARPi compounds in wildtype (WT) and DNA repair-deficient CRC cell lines together with the chemotherapeutics irinotecan (IT), 5-fluorouracil (5-FU), and oxaliplatin (OXA). Based on the ComPlat molecule archive, we identified novel PARPi candidates by molecular docking experiments in silico, which were then confirmed by in vitro PARP activity measurements. Two promising candidates (X17613 and X17618) also showed potent PARP-1 inhibition in a CRC cell-based assay. In contrast to olaparib, the PARPi candidates caused no PARP-1 trapping and, consistently, were not or only weakly cytotoxic in WT CRC cells and their BRCA2- or ATR-deficient counterparts. Importantly, both PARPi candidates did not affect the viability of nonmalignant human colonic epithelial cells. While both olaparib and veliparib increased the sensitivity of WT CRC cells towards IT, no synergism was observed for X17613 and X17618. Finally, we provided evidence that all PARPi (olaparib > veliparib > X17613 > X17618) synergize with chemotherapeutic drugs (IT > OXA) in a BRCA2-dependent manner in CRC cells, whereas ATR deficiency had only a minor impact. Collectively, our study identified novel lead structures with potent PARP-1 inhibitory activity in CRC cells but low cytotoxicity due to the lack of PARP-1 trapping, which synergized with IT in homologous recombination deficiency.

Poly(ADP-Ribose) Polymerase (PARP) Inhibitors for Cancer Therapy: Advances, Challenges, and Future Directions

Poly(ADP-ribose) polymerases (PARPs) are crucial nuclear proteins that play important roles in various cellular processes, including DNA repair, gene transcription, and cell death. Among the 17 identified PARP family members, PARP1 is the most abundant enzyme, with approximately 1-2 million molecules per cell, acting primarily as a DNA damage sensor. It has become a promising biological target for anticancer drug studies. Enhanced PARP expression is present in several types of tumors, such as melanomas, lung cancers, and breast tumors, correlating with low survival outcomes and resistance to treatment. PARP inhibitors, especially newly developed third-generation inhibitors currently undergoing Phase II clinical trials, have shown efficacy as anticancer agents both as single drugs and as sensitizers for chemo- and radiotherapy. This review explores the properties, characteristics, and challenges of PARP inhibitors, discussing their development from first-generation to third-generation compounds, more sustainable synthesis methods for discovery of new anti-cancer agents, their mechanisms of therapeutic action, and their potential for targeting additional biological targets beyond the catalytic active site of PARP proteins. Perspectives on green chemistry methods in the synthesis of new anticancer agents are also discussed.

Prediction of homologous recombination deficiency from routine histology with attention-based multiple instance learning in nine different tumor types

BACKGROUND

Homologous recombination deficiency (HRD) is recognized as a pan-cancer predictive biomarker that potentially indicates who could benefit from treatment with PARP inhibitors (PARPi). Despite its clinical significance, HRD testing is highly complex. Here, we investigated in a proof-of-concept study whether Deep Learning (DL) can predict HRD status solely based on routine hematoxylin & eosin (H&E) histology images across nine different cancer types.

METHODS

We developed a deep learning pipeline with attention-weighted multiple instance learning (attMIL) to predict HRD status from histology images. As part of our approach, we calculated a genomic scar HRD score by combining loss of heterozygosity (LOH), telomeric allelic imbalance (TAI), and large-scale state transitions (LST) from whole genome sequencing (WGS) data of n = 5209 patients across two independent cohorts. The model's effectiveness was evaluated using the area under the receiver operating characteristic curve (AUROC), focusing on its accuracy in predicting genomic HRD against a clinically recognized cutoff value.

RESULTS

Our study demonstrated the predictability of genomic HRD status in endometrial, pancreatic, and lung cancers reaching cross-validated AUROCs of 0.79, 0.58, and 0.66, respectively. These predictions generalized well to an external cohort, with AUROCs of 0.93, 0.81, and 0.73. Moreover, a breast cancer-trained image-based HRD classifier yielded an AUROC of 0.78 in the internal validation cohort and was able to predict HRD in endometrial, prostate, and pancreatic cancer with AUROCs of 0.87, 0.84, and 0.67, indicating that a shared HRD-like phenotype occurs across these tumor entities.

CONCLUSIONS

This study establishes that HRD can be directly predicted from H&E slides using attMIL, demonstrating its applicability across nine different tumor types.

FL118 Enhances Therapeutic Efficacy in Colorectal Cancer by Inhibiting the Homologous Recombination Repair Pathway through Survivin-RAD51 Downregulation

Background/Objectives: Irinotecan, a camptothecin (CPT) derivative, is commonly used as a first-line therapy for colorectal cancer (CRC), but resistance remains a significant challenge. This study aims to explore the therapeutic potential of FL118, another CPT derivative, with a focus on overcoming resistance to irinotecan. Methods: The effects of FL118 on CRC cells were evaluated, and bioinformatics analysis was performed on RNA-seq data. Transfection was conducted to observe the knockdown effect of survivin, and the in vivo efficacy of FL118 was assessed using a xenograft model. Results: FL118 induces apoptosis, G2/M arrest, and DNA damage. A notable mechanism of action of FL118 is a reduction in survivin levels, which downregulates the expression of RAD51, a key marker of homologous recombination, and attenuates DNA repair processes. Given that SN38 is the active metabolite of irinotecan, FL118 reduces cell viability and RAD51 in SN38-resistant LOVO cells. Conclusions: Our findings provide effective insights into the antitumor activity of FL118 and its potential as a therapeutic agent for overcoming irinotecan resistance in CRC.

Recent Developments and Evolving Therapeutic Strategies in KMT2A-Rearranged Acute Leukemia

BACKGROUND

Rearrangements of the histone-lysine-N-methyltransferase (KMT2A), previously referred to as mixed-lineage leukemia (MLL), are among the most common chromosomal abnormalities in patients with acute myeloid leukemia (AML) and acute lymphoblastic leukemia (ALL), involving numerous different fusion partners. KMT2A-rearranged (KMT2A-r) leukemia is characterized by a rapid onset, aggressive progression, and significantly worse prognosis compared to non-KMT2A-r leukemias. Even with contemporary chemotherapeutic treatments and hematopoietic stem cell transplantations (HSCT), patients with KMT2A-r leukemia typically experience poor outcomes and limited responses to these therapies.

OBJECTIVES

This review aims to consolidate recent studies on the general gene characteristics and associated mechanisms of KMT2A-r acute leukemia, as well as the cytogenetics, immunophenotype, clinical presentation, and risk stratification of both KMT2A-r-AML and KMT2A-r-ALL. Particularly, the treatment targets in KMT2A-r acute leukemia are examined.

METHODS

A comprehensive review was carried out by systematically synthesizing existing literature on PubMed, using the combination of the keywords 'KMT2A-rearranged acute leukemia', 'lymphoblastic leukemia', 'myeloid leukemia', and 'therapy'. The available studies were screened for selection based on quality and relevance.

CONCLUSIONS

Studies indicate that KMT2A rearrangements are present in over 70% of infant leukemia cases, approximately 10% of adult AML cases, and numerous instances of secondary acute leukemias, making it a disease of critical concern to clinicians and researchers alike. The future of KMT2A-r acute leukemia research is characterized by an expanding knowledge of the disease's biology, with an emphasis on personalized therapies, immunotherapies, genomic advancements, and innovative therapeutic combinations. The overarching aim is to enhance patient outcomes, lessen the disease burden, and elevate the quality of life for those affected. Ongoing research and clinical trials in this area continue to offer promising opportunities for refining treatment strategies and improving patient prognosis.

Review of Novel Surgical, Radiation, and Systemic Therapies and Clinical Trials in Glioblastoma

Glioblastoma (GBM) is the most common malignant primary brain tumor in adults. Despite an established standard of care including surgical resection, radiation therapy, and chemotherapy, GBM unfortunately is associated with a dismal prognosis. Therefore, researchers are extensively evaluating avenues to expand GBM therapy and improve outcomes in patients with GBM. In this review, we provide a broad overview of novel GBM therapies that have recently completed or are actively undergoing study in clinical trials. These therapies expand across medical, surgical, and radiation clinical trials. We additionally review methods for improving clinical trial design in GBM.

BUB1 Inhibition Overcomes Radio- and Chemoradiation Resistance in Lung Cancer

Background: Despite advances in targeted therapies and immunotherapies, traditional treatments like microtubule stabilizers (paclitaxel, docetaxel), DNA-intercalating platinum drugs (cisplatin), and radiation therapy remain essential for managing locally advanced and metastatic lung cancer. Identifying novel molecular targets could enhance the efficacy of these treatments. Hypothesis: We hypothesize that BUB1 (Ser/Thr kinase) is overexpressed in lung cancers and its inhibition will sensitize lung cancers to chemoradiation. Methods: BUB1 inhibitor (BAY1816032) was combined with cisplatin, paclitaxel, a PARP inhibitor olaparib, and radiation in cell proliferation and radiation-sensitization assays. Biochemical and molecular assays evaluated the impact on DNA damage signaling and cell death. Results: Immunostaining of lung tumor microarrays (TMAs) confirmed higher BUB1 expression in non-small cell lung cancer (NSCLC) and small cell lung cancer (SCLC) compared to normal tissues. In NSCLC, BUB1 overexpression correlated directly with the expression of TP53 mutations and poorer overall survival in NSCLC and SCLC patients. BAY1816032 synergistically sensitized lung cancer cell lines to paclitaxel and olaparib and enhanced cell killing by radiation in both NSCLC and SCLC. Molecular analysis indicated a shift towards pro-apoptotic and anti-proliferative states, evidenced by altered BAX, BCL2, PCNA, and Caspases-9 and -3 expressions. Conclusions: Elevated BUB1 expression is associated with poorer survival in lung cancer. Inhibiting BUB1 sensitizes NSCLC and SCLC to chemotherapies (cisplatin, paclitaxel), targeted therapy (olaparib), and radiation. Furthermore, we present the novel finding that BUB1 inhibition sensitized both NSCLC and SCLC to radiotherapy and chemoradiation. Our results demonstrate BUB1 inhibition as a promising strategy to sensitize lung cancers to radiation and chemoradiation therapies.