Combining targeted DNA repair inhibition and immune-oncology approaches for enhanced tumor control

Progesterone Enhances Niraparib Efficacy in Ovarian Cancer by Promoting Palmitoleic-Acid-Mediated Ferroptosis

Poly (adenosine 5'-diphosphate-ribose) polymerase inhibitors (PARPi) are increasingly important in the treatment of ovarian cancer. However, more than 40% of BRCA1/2-deficient patients do not respond to PARPi, and BRCA wild-type cases do not show obvious benefit. In this study, we demonstrated that progesterone acted synergistically with niraparib in ovarian cancer cells by enhancing niraparib-mediated DNA damage and death regardless of BRCA status. This synergy was validated in an ovarian cancer organoid model and in vivo experiments. Furthermore, we found that progesterone enhances the activity of niraparib in ovarian cancer through inducing ferroptosis by up-regulating palmitoleic acid and causing mitochondrial damage. In clinical cohort, it was observed that progesterone prolonged the survival of patients with ovarian cancer receiving PARPi as second-line maintenance therapy, and high progesterone receptor expression combined with low glutathione peroxidase 4 (GPX4) expression predicted better efficacy of PARPi in patients with ovarian cancer. These findings not only offer new therapeutic strategies for PARPi poor response ovarian cancer but also provide potential molecular markers for predicting the PARPi efficacy.

Radiotherapy-sensitized cancer immunotherapy via cGAS-STING immune pathway by activatable nanocascade reaction

Radiotherapy-induced immune activation holds great promise for optimizing cancer treatment efficacy. Here, we describe a clinically used radiosensitizer hafnium oxide (HfO2) that was core coated with a MnO2 shell followed by a glucose oxidase (GOx) doping nanoplatform (HfO2@MnO2@GOx, HMG) to trigger ferroptosis adjuvant effects by glutathione depletion and reactive oxygen species production. This ferroptosis cascade potentiation further sensitized radiotherapy by enhancing DNA damage in 4T1 breast cancer tumor cells. The combination of HMG nanoparticles and radiotherapy effectively activated the damaged DNA and Mn2+-mediated cGAS-STING immune pathway in vitro and in vivo. This process had significant inhibitory effects on cancer progression and initiating an anticancer systemic immune response to prevent distant tumor recurrence and achieve long-lasting tumor suppression of both primary and distant tumors. Furthermore, the as-prepared HMG nanoparticles "turned on" spectral computed tomography (CT)/magnetic resonance dual-modality imaging signals, and demonstrated favorable contrast enhancement capabilities activated by under the GSH tumor microenvironment. This result highlighted the potential of nanoparticles as a theranostic nanoplatform for achieving molecular imaging guided tumor radiotherapy sensitization induced by synergistic immunotherapy.

PBMCs as Tool for Identification of Novel Immunotherapy Biomarkers in Lung Cancer

BACKGROUND

Lung cancer (LC), including both non-small (NSCLC) and small (SCLC) subtypes, is currently treated with a combination of chemo- and immunotherapy. However, predictive biomarkers to identify high-risk patients are needed. Here, we explore the role of peripheral blood mononuclear cells (PBMCs) as a tool for novel biomarkers searching.

METHODS

We analyzed the expression of the cGAS-STING pathway, a key DNA sensor that activates during chemotherapy, in PBMCs from LC patients divided into best responders (BR), responders (R) and non-responders (NR). The PBMCs were whole exome sequenced (WES).

RESULTS

PBMCs from BR and R patients of LC cohorts showed the highest levels of STING (p < 0.0001) and CXCL10 (p < 0.0001). From WES, each subject had at least 1 germline/somatic alteration in a DDR gene and the presence of more DDR gene mutations correlated with clinical responses, suggesting novel biomarker implications. Thus, we tested the effect of the pharmacological DDR inhibitor (DDRi) in PBMCs and in three-dimensional spheroid co-culture of PBMCs and LC cell lines; we found that DDRi strongly increased cGAS-STING expression and tumor infiltration ability of immune cells in NR and R patients. Furthermore, we performed FACS analysis of PBMCs derived from LC patients from the BR, R and NR cohorts and we found that cytotoxic T cell subpopulations displayed the highest STING expression.

CONCLUSIONS

cGAS-STING signaling activation in PBMCs may be a novel potential predictive biomarker for the response to immunotherapy and high levels are correlated with a better response to treatment along with an overall increased antitumor immune injury.

DNA repair deficiency and the immune microenvironment: A pathways perspective

Timely and accurate repair of DNA damage is required for genomic stability, but DNA repair pathways are often lost or altered in tumors. In addition to directly impacting tumor cell response to DNA damage, DNA repair deficiency can also alter the immune microenvironment via changes in innate and adaptive immune signaling. In some settings, these changes can lead to increased sensitivity to immune checkpoint inhibitors (ICIs). In this review, we discuss the impact of specific DNA repair pathway dysfunction on immune contexture and ICI response in solid tumors.

Poly (ADP-ribose) Polymerase Inhibitors in Patients with Metastatic Castration-Resistant Prostate Cancer: A Meta-Analysis of Randomized Controlled Trials

Context: Several recent randomized controlled trials (RCTs) have reported on the survival benefits of poly (ADP-ribose) polymerase inhibitors (PARPi) compared to standard-of-care (SOC) treatment (enzalutamide, abiraterone, or docetaxel) in patients with metastatic castration-resistant prostate cancer (mCRPC). However, there is a limited integrated analysis of high-quality evidence comparing the efficacy and safety of PARPi and SOC treatments in this context. Objective: This study aims to comprehensively analyze the survival benefits and adverse events associated with PARPi and SOC treatments through a head-to-head meta-analysis in mCRPC. Evidence acquisition: A systematic review search was conducted in PubMed, Embase, Clinical trials, and the Central Cochrane Registry in July 2023. RCTs were assessed following the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) guidelines. The systematic review was prospectively registered on PROSPERO (CRD42023441034). Evidence synthesis: A total of 8 studies, encompassing 2341 cases in the PARPi treatment arm and 1810 cases in the controlled arm, were included in the qualitative synthesis. The hazard ratio (HR) for radiographic progression-free survival (rPFS) and overall survival (OS) were 0.74 (95% CI, 0.61-0.90) and 0.89 (95% CI, 0.80-0.99), respectively, in the intention-to-treatment patients. For subgroup analysis, HRs for rPFS and OS in the BRCA-mutated subgroup were 0.39 (95% CI, 0.28-0.55) and 0.62 (95% CI, 0.38-0.99), while in the HRR-mutated subgroup, HR for rPFS was 0.57 (95% CI, 0.48-0.69) and for OS was 0.77 (95% CI, 0.64-0.93). The odds ratio (OR) for all grades of adverse events (AEs) and AEs with severity of at least grade 3 were 3.86 (95% CI, 2.53-5.90) and 2.30 (95% CI, 1.63-3.26), respectively. Conclusions: PARP inhibitors demonstrate greater effectiveness than SOC treatments in HRR/BRCA-positive patients with mCRPC. Further research is required to explore ways to reduce adverse event rates and investigate the efficacy of HRR/BRCA-negative patients.

DNA as the main target in radiotherapy-a historical overview from first isolation to anti-tumour immune response

DNA damage is one of the foremost mechanisms of irradiation at the biological level. After the first isolation of DNA by Friedrich Miescher in the 19th century, the structure of DNA was described by Watson and Crick. Several Nobel Prizes have been awarded for DNA-related discoveries. This review aims to describe the historical perspective of DNA in radiation biology. Over the decades, DNA damage has been identified and quantified after irradiation. Depending on the type of sensing, different proteins are involved in sensing DNA damage and repairing the damage, if possible. For double-strand breaks, the main repair mechanisms are non-homologous end joining and homologous recombination. Additional mechanisms are the Fanconi anaemia pathway and base excision repair. Different methods have been developed for the detection of DNA double-strand breaks. Several drugs have been developed that interfere with different DNA repair mechanisms, e.g., PARP inhibitors. These drugs have been established in the standard treatment of different tumour entities and are being applied in several clinical trials in combination with radiotherapy. Over the past decades, it has become apparent that DNA damage mechanisms are also directly linked to the immune response in tumours. For example, cytosolic DNA fragments activate the innate immune system via the cGAS STING pathway.

Prognostic analysis of patients with breast cancer based on tumor mutational burden and DNA damage repair genes

Background

Breast cancer has a high tumor-specific death rate and poor prognosis. In this study, we aimed to provide a basis for the prognostic risk in patients with breast cancer using significant gene sets selected by analyzing tumor mutational burden (TMB) and DNA damage repair (DDR).

Methods

Breast cancer genomic and transcriptomic data were obtained from The Cancer Genome Atlas (TCGA). Breast cancer samples were dichotomized into high- and low-TMB groups according to TMB values. Differentially expressed DDR genes between high- and low-TMB groups were incorporated into univariate and multivariate cox regression model to build prognosis model. Performance of the prognosis model was validated in an independently new GEO dataset and evaluated by time-dependent ROC curves.

Results

Between high- and low-TMB groups, there were 6,424 differentially expressed genes, including 67 DDR genes. Ten genes associated with prognosis were selected by univariate cox regression analysis, among which seven genes constituted a panel to predict breast cancer prognosis. The seven-gene prognostic model, as well as the gene copy numbers are closely associated with tumor-infiltrating immune cells.

Conclusion

We established a seven-gene prognostic model comprising MDC1, PARP3, PSMB1, PSMB9, PSMD2, PSMD7, and PSMD14 genes, which provides a basis for further exploration of a population-based prediction of prognosis and immunotherapy response in patients with breast cancer.

Senataxin and R-loops homeostasis: multifaced implications in carcinogenesis

R-loops are inherent byproducts of transcription consisting of an RNA:DNA hybrid and a displaced single-stranded DNA. These structures are of key importance in controlling numerous physiological processes and their homeostasis is tightly controlled by the activities of several enzymes deputed to process R-loops and prevent their unproper accumulation. Senataxin (SETX) is an RNA/DNA helicase which catalyzes the unwinding of RNA:DNA hybrid portion of the R-loops, promoting thus their resolution. The key importance of SETX in R-loops homeostasis and its relevance with pathophysiological events is highlighted by the evidence that gain or loss of function SETX mutations underlie the pathogenesis of two distinct neurological disorders. Here, we aim to describe the potential impact of SETX on tumor onset and progression, trying to emphasize how dysregulation of this enzyme observed in human tumors might impact tumorigenesis. To this aim, we will describe the functional relevance of SETX in regulating gene expression, genome integrity, and inflammation response and discuss how cancer-associated SETX mutations might affect these pathways, contributing thus to tumor development.

Relationship between homologous recombination deficiency and clinical features of breast cancer based on genomic scar score

BACKGROUND

Homologous recombination deficiency (HRD) phenotype will sensitize tumors to poly (ADP-ribose) polymerases inhibitors and platinum. However, previous studies did not focus on the prevalence of HRD among Chinese breast cancer (BC) patients.

METHODS

One hundred and forty-seven BC patients were included in this study. Their HRD status was assessed by Genomic Scar Score (GSS), which was determined according to the length, site, and type of copy number. HRD was defined as positive when a harmful BRCA1/2 mutation was detected or GSS ≥50.

RESULTS

Our data revealed that 9.5% of the 147 patients tested positive for BRCA1/2 mutation, while approximately 34.7% were HRD-positive. For triple negative BC (TNBC), HRD positivity rate (60.5%) was higher than Luminal A (5.3%), Luminal B (HER2-) (28.8%), and Luminal B (HER2+) (31.6%) subgroups. HRD-positive tumors were more likely to be ER/PR-negative and exhibited higher Ki-67 expression. 50.0% of the HRD-positive patients achieved pathologic complete remission (pCR) after neoadjuvant therapy. HRD-positive patients tended to have a higher risk for cancer recurrence or metastasis compared to HRD-negative patients (29.4% vs. 13.5%).

CONCLUSION

We investigated the HRD status among Chinese BC patients using an HRD detection tool developed based on the Chinese population. The clinical characteristics, pathological profile, family history pattern, neoadjuvant efficacy, and disease progression events of HRD-positive and negative patients were described and compared. Thus, our data provided an evidence-based basis for applying the original HRD assay in Chinese BC.

Combining PARP Inhibition and Immunotherapy in BRCA-Associated Cancers

Poly (ADP-ribose) polymerase (PARP) inhibitors have significantly improved treatment outcomes of homologous recombination (HR) repair-deficient cancers. While the activity of these agents is largely linked to multiple mechanisms underlying the synthetic lethality of PARP inhibition and HR deficiency, emerging data suggest that their efficacy is also tied to their effects on the immune microenvironment and dependent upon cytotoxic T-cell activation. Effects observed in preclinical models are currently being validated in on-treatment biopsy samples procured from patients enrolled in clinical trials. Although this work has stimulated the development of combinations of PARP inhibitors with immunomodulatory agents, results to date have not demonstrated the superiority of combined PARP inhibition and immune checkpoint blockade compared with PARP inhibition alone. These results have stimulated a more comprehensive assessment of the immunosuppressive components of the tumor microenvironment that must be addressed so that the efficacy of PARP inhibitor agents can be maximized.

Targeting the BRCA1/2 deficient cancer with PARP inhibitors: Clinical outcomes and mechanistic insights

BRCA1 and BRCA2 play a critical role in a variety of molecular processes related to DNA metabolism, including homologous recombination and mediating the replication stress response. Individuals with mutations in the BRCA1 and BRCA2 (BRCA1/2) genes have a significantly higher risk of developing various types of cancers, especially cancers of the breast, ovary, pancreas, and prostate. Currently, the Food and Drug Administration (FDA) has approved four PARP inhibitors (PARPi) to treat cancers with BRCA1/2 mutations. In this review, we will first summarize the clinical outcomes of the four FDA-approved PARPi in treating BRCA1/2 deficient cancers. We will then discuss evidence supporting the hypothesis that the cytotoxic effect of PARPi is likely due to inducing excessive replication stress at the difficult-to-replicate (DTR) genomic regions in BRCA1/2 mutated tumors. Finally, we will discuss the ongoing preclinical and clinical studies on how to combine the PARPi with immuno-oncology drugs to further improve clinical outcomes.