Unravelling the molecular basis of PARP inhibitor resistance in prostate cancer with homologous recombination repair deficiency.

Prostate cancer is a disease with heterogeneous characteristics, making its treatability and curability dependent on the cancer's stage. While prostate cancer is often indolent, some cases can be aggressive and evolve into metastatic castration-resistant prostate cancer (mCRPC), which is lethal. A significant subset of individuals with mCRPC exhibit germline and somatic variants in components of the DNA damage repair (DDR) pathway. Recently, PARP inhibitors (PARPi) have shown promise in treating mCRPC patients who carry deleterious alterations in BRCA2 and 13 other DDR genes that are important for the homologous recombination repair (HRR) pathway. These inhibitors function by trapping PARP, resulting in impaired PARP activity and increased DNA damage, ultimately leading to cell death through synthetic lethality. However, the response to these inhibitors only lasts for 3-4 months, after which the cancer becomes PARPi resistant. Cancer cells can develop resistance to PARPi through numerous mechanisms, such as secondary reversion mutations in DNA repair pathway genes, heightened drug efflux, loss of PARP expression, HRR reactivation, replication fork stability, and upregulation of Wnt/Catenin and ABCB1 pathways. Overcoming PARPi resistance is a critical and complex process, and there are two possible ways to sensitize the resistance. The first approach is to potentiate the PARPi agents through chemo/radiotherapy and combination therapy, while the second approach entails targeting different signaling pathways. This review article highlights the latest evidence on the resistance mechanism of PARPi in lethal prostate cancer and discusses additional therapeutic opportunities available for prostate cancer patients with DDR gene alterations who do not respond to PARPi.

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.

Combination of the PARPi and ARSi in advanced castration resistant prostate cancer: a review of the recent phase III trials.

Tumors with an impaired ability to repair DNA double-strand breaks by homologous recombination, including those with alterations in breast cancer 1 and 2 (BRCA1 and BRCA2) genes, are very sensitive to blocking DNA single-strand repair by inhibition of the poly (ADP-ribose) polymerase (PARP) enzyme. This provides the basis for a synthetic deadly strategy in the treatment of different types of cancer, such as prostate cancer (PCa). The phase 3 PROfound study was the first to lead to olaparib approval in patients with metastatic castration resistant PCa (mCRPC) and BRCA genes mutations. In recent years, the benefit of combination therapy consisted of a PARP inhibitor (PARPi) plus an androgen receptor signalling inhibitor (ARSi), was evaluated as first-line treatment of mCRPC, regardless of the mutational state of genes, participating in the homologous recombination repair (HRR). This review explores the role of PARPi in PCa and analyses the data of latest clinical trials exploring the PARPi-ARSi combinations, and how these results could change our clinical practice.

Claudin-4 remodeling of nucleus-cell cycle crosstalk maintains ovarian tumor genome stability and drives resistance to genomic instability-inducing agents.

During cancer development, the interplay between the nucleus and the cell cycle leads to a state of genomic instability, often accompanied by observable morphological aberrations. These aberrations can be controlled by tumor cells to evade cell death, either by preventing or eliminating genomic instability. In epithelial ovarian cancer (EOC), overexpression of the multifunctional protein claudin-4 is a key contributor to therapy resistance through mechanisms associated with genomic instability. However, the molecular mechanisms underlying claudin-4 overexpression in EOC remain poorly understood. Here, we altered claudin-4 expression and employed a unique claudin-4 targeting peptide (CMP) to manipulate the function of claudin-4. We found that claudin-4 facilitates genome maintenance by linking the nuclear envelope and cytoskeleton dynamics with cell cycle progression. Claudin-4 caused nuclei constriction by excluding lamin B1 and promoting perinuclear F-actin accumulation, associated with remodeling nuclear architecture, thus altering nuclear envelope dynamics. Consequently, cell cycle modifications due to claudin-4 overexpression resulted in fewer cells entering the S-phase and reduced genomic instability. Importantly, disrupting biological interactions of claudin-4 using CMP and forskolin altered oxidative stress cellular response and increased the efficacy of PARP inhibitor treatment. Our data indicate that claudin-4 protects tumor genome integrity by remodeling the crosstalk between the nuclei and the cell cycle, leading to resistance to genomic instability formation and the effects of genomic instability-inducing agents.

Genetic landscape of homologous recombination repair and practical outcomes of PARPi therapy in ovarian cancer management.

Background: Genetic studies of ovarian cancer (OC) have historically focused on BRCA1/2 mutations, lacking other studies of homologous recombination repair (HRR). Poly (ADP-ribose) polymerase inhibitors (PARPi) exploit synthetic lethality to significantly improve OC treatment outcomes, especially in BRCA1/2 deficiency patients. Objectives: Our study aims to construct a mutation map of HRR genes in OC and identify factors influencing the efficacy of PARPi. Design: A retrospective observational analysis of HRR gene variation data from 695 OC patients from March 2019 to February 2022 was performed. Methods: The HRR gene variation data of 695 OC patients who underwent next-generation sequencing (NGS) in the First Affiliated Hospital of Zhengzhou University were retrospectively collected. Clinical data on the use of PARPi in these patients were also gathered to identify factors that may interfere with the efficacy of PARPi. Results: Out of 127 pathogenic variants in the BRCA1/2 genes, 104 (81.9%) were BRCA1 mutations, and 23 (18.1%) were BRCA2 mutations. Among the 59 variants of uncertain significance (VUS), 20 (33.9%) were BRCA1, while 39 (66.1%) were BRCA2 mutations. In addition to BRCA1/2, HRR gene results showed that 9 (69%) of 13 were HRR pathway pathogenic variants; and 16 (1.7%) of 116 VUS were Food and Drug Administration (FDA)-approved mutated HRR genes. Notably, the treatment regimen significantly influenced the effectiveness of PARPi, especially when using first-line maintenance therapy, leading to enhanced progression-free survival (PFS) compared to alternative protocols. Conclusion: Focusing on HRR gene mutations and supporting clinical research about PARPi in OC patients is crucial for developing precision treatment strategies and enhancing prognosis.

Clinicopathological and molecular features of tubo-ovarian carcinosarcomas: a series of 51 cases.

Objective: Tubo-ovarian carcinosarcomas are rare, extremely aggressive malignant tumors that contain both carcinomatous and sarcomatous components. Due to the disease's rarity, developing an effective treatment strategy for ovarian carcinosarcomas has been challenging. A study was conducted to investigate the clinicopathologic and molecular features of this rare disease. Methods: We enrolled all patients diagnosed with tubo-ovarian carcinosarcomas from January 2007 to December 2022. The clinical and pathological data were gathered from medical records. Kaplan-Meier curves were plotted to calculate OS and PFS. The Log-rank test and Cox regression model were utilized to explore the relationship between clinicopathological parameters and survival. Patients with cancer tissues available had sequencing with a 242-gene panel done to investigate the mutational landscape and signature of the disease. Results: In total, 65% of the patients were diagnosed with advanced-stage cancer. The median PFS and OS of this cohort were 27 and 40 months, respectively, and there was no significant difference in survival between the homologous and heterologous components of sarcoma. Unexpectedly, staging did not have effects on prognosis. All patients had surgical attempts, and suboptimal debulking status was correlated with poorer PFS and OS. MSI was identified in 0% with low Tumor mutation burden (TMB) indicating a poor response to immunotherapy. Low HER2 expression is controversial, according to previous reports, and gives us limited choices with this rare and aggressive disease. We surprisingly found the homologous recombination deficiency (HRD)-positive status was identified in 64% of OCS, which is significantly higher than UCS and other types of epithelial ovarian cancer. The fact that all patients in our cohort who received olaparib as maintenance therapy had survived over 30 months and two had no evidence of recurrence at the latest follow-up might further validate the role of poly (ADP-ribose) polymerase inhibitors (PARPi) in the management of OCS. Conclusion: OCS patients seemed to respond to carboplatin/paclitaxel with optimal PFS and OS. Cytoreduction with no residuals proved to be the sole independent prognostic factor. WES should be done to assess the prognosis and assist with the targeted therapy, especially the HRD test, which might help select potential patients who benefit from PARPi.

Efficacy of chemotherapy after progression during or following PARPi exposure in ovarian cancer.

BACKGROUND: Poly(ADP-ribose) polymerase inhibitors (PARPis) improved advanced ovarian cancer treatment. Most patients progress during or following PARPi exposure, however, with concerns about sensitivity of subsequent chemotherapy. PATIENTS AND METHODS: In this international cohort study, we evaluated the efficacy of a subsequent chemotherapy following PARPi exposure in high-grade ovarian carcinoma patients. Endpoints included progression-free survival (PFS), overall survival and a multivariable Cox model was built to identify factors influencing PFS. RESULTS: We included 291 patients from four international centers treated between January 2002 and December 2021. The median number of previous chemotherapy was 1 (1.0-7.0), the median duration of PARPi exposure was 6.5 months (0.2-54.3 months). PARPi was used in first line in 14.1% patients. Most progressions occurred under PARPi exposure (89.1%). A BRCA pathogenic variant was identified in 130 patients (44.7%), absent in 157 patients (54.0%), and undocumented in 4 patients (1.4%). Platinum-based CT (PBC) and non-PBC were administered as subsequent treatments in, respectively, 182 patients (62.5%) and 109 patients (37.5%). Multivariable analyses showed that platinum-free interval (PFI) >6 months [adjusted hazards ratio (HR), 0.52; 95% confidence interval (CI) 0.39-0.70] and type of initial surgery (adjusted HR, 1.41; 95% CI 1.07-1.87; interval or closing surgery versus primary surgery) were associated with PFS, independent of BRCA status or line of therapy (≥2 versus 1). In patients with a PFI >6 months, PBC was numerically associated with the best PFS (adjusted HR, 0.68; 95% CI 0.46-1.01). CONCLUSION: This is the largest real-world study assessing the efficacy of subsequent chemotherapy in patients progressing during PARPi exposure. The patients have poor outcomes. PBC is the best option in patients progressing on PARPi and eligible for PBC rechallenge (PFI >6 months).

Durable benefit from poly(ADP-ribose) polymerase inhibitors in metastatic prostate cancer in routine practice: biomarker associations and implications for optimal clinical next-generation sequencing testing.

BACKGROUND: Controlled trials have consistently demonstrated the efficacy of poly(ADP-ribose) polymerase inhibitors (PARPis) in patients with metastatic castration-resistant prostate cancer (mCRPC) and BRCA1 or BRCA2 alterations (BRCAalt). However, the reported efficacy of PARPi for alterations in other homologous recombination repair (HRR) genes is less consistent. We sought to evaluate the routine practice effectiveness of PARPi between and within these groups. DESIGN: Patient-level data from a deidentified nationwide (USA-based) cancer clinico-genomic database between January 2011 and September 2023 were extracted. Patients with mCRPC and comprehensive genomic profiling by liquid biopsy [circulating tumor DNA (ctDNA)] or tissue (tumor) biopsy and who received single-agent PARPi were included and grouped by BRCAalt, ATMalt, other HRR, or no HRR. We further subcategorized BRCAalt into homozygous loss (BRCAloss) and all other deleterious BRCAalt (otherBRCAalt). RESULTS: A total of 445 patients met inclusion criteria: 214 with tumor and 231 with ctDNA. BRCAalt had more favorable outcomes to PARPi compared with ATM, other HRR, and no HRR groups. Within the BRCAalt subgroup, compared with other BRCAalt, BRCAloss had a more favorable time to next treatment (median 9 versus 19.4 months, P = 0.005), time to treatment discontinuation (median 8 versus 14 months, P = 0.006), and routine practice overall survival (median 14.7 versus 19.4 months, P = 0.016). Tumor BRCAloss prevalence (3.1%) was similar to ctDNA prevalence in liquid biopsy specimens with high tumor fraction (>20%). BRCAloss was not detected in orthogonal germline testing. CONCLUSIONS: PARPi routine practice effectiveness between groups mirrors prospective trials. Within the BRCAalt group, BRCAloss had the best outcomes. Unless the ctDNA tumor fraction is very high, somatic tissue testing (archival or metastatic) should be prioritized to identify patients who may benefit most from PARPi. When tissue testing is not clinically feasible, sufficient ctDNA tumor fraction levels for detection are enriched at clinical timepoints associated with tumor progression.

TMPRSS2:ERG Gene Fusion Might Predict Resistance to PARP Inhibitors in Metastatic Castration-resistant Prostate Cancer.

BACKGROUND/AIM: The emergence of novel DNA damage repair (DDR) pathways in molecular-target therapy drugs (MTTD) has shown promising outcomes in treating patients with metastatic castration-resistant prostate cancer (mCRPC). About 25% of mCRPC patients have actionable deleterious aberrations in DDR genes, primarily in the homologous recombination (HR) pathway. However, the response rate in patients with BRCA1/2 or mutations in HRR-related genes is only 45%-55%, when exposed to poly ADP ribose polymerase (PARP) inhibitor-based therapy (PARPi). A frequent characteristic feature of prostate cancer (PC) is the occurrence of genomic rearrangement that affects the transmembrane protease serine 2 (TMPRSS2) and E26 transformation-specific (ETS)- transcription factor-related gene (ERG). MATERIALS AND METHODS: In this study, a total of 114 patients with mCRPC had their RNA and DNA sequenced using next-generation sequencing. RESULTS: Based on their genetic profile of deleterious gene alterations of BRCA1/2 or ATM, six patients were selected for PARPi. Patients with TMPRSS2:ERG gene fusion and homozygous alteration in ATM or BRCA2 (n=2) or heterozygous alterations (BRCA1 or BRCA2) and lack of TMPRSS2:ERG gene fusion (n=2) did not show clinical benefit from PARPi (treatment duration <16 weeks). In contrast, patients (n=2) without TMPRSS2:ERG gene fusion and homozygous deleterious alterations in ATM or BRCA2 all had clinical benefit from PARPi (treatment duration ≥16 weeks). CONCLUSION: The TMPRSS2:ERG transcript product might be used as a PARPi resistance biomarker.

Clinical and radiological pattern of olaparib-induced interstitial lung disease.

BACKGROUND: PARP inhibitors (PARPi) are used in the treatment of ovarian, breast, pancreatic, and prostate cancers. Pneumonitis has been identified as a potential side effect, with a higher meta-analysis-assessed risk for olaparib versus other PARPi. Olaparib-induced interstitial lung disease (O-ILD) was first described within the Japanese population, with few information available for Caucasian patients. METHODS: We performed a retrospective study by pooling data from the French and Belgian pharmacovigilance databases from 2018 to 2022. Patients with O-ILD were included following a central review by: 1) pharmacologists using the French drug causality assessment method; 2) senior pneumologists or radiologists, using the Fleischner Society's recommendations. RESULTS: Five patients were identified and analysed. All were females, with ovarian or breast cancer. Median age at O-ILD diagnosis was 71 (38-72) years old, with no smoking history. Median delay between treatment initiation and symptom occurrence was 12 (6-33) weeks. Pneumonitis severity assessed using the Common Terminology Criteria for Adverse Events V5 was Grade 3 (n = 4) or 2 (n = 1). CT-scan review (n = 3) described hypersensitivity pneumonitis reaction as a common pattern. Bronchioalveolar lavage (n = 4) revealed lymphocytic alveolitis. Treatments relied on olaparib discontinuation (n = 5) and glucocorticoid intake (n = 4), with no fatal issue. Safe re-challenge with PARPi occurred in two patients. Forty additional O-ILD cases were identified in the WHO VigiBase database, including one fatal case. CONCLUSIONS: PARPi-ILD is a rare but potentially life-threatening disease, presenting as a hypersensitivity pneumonitis pattern within 3 months of PARPi initiation. Treatment primarily relies on medication discontinuation. Re-challenging with another PARPi could be considered. CLINICAL TRIAL NUMBER: CEPRO #2023-010.

Internal Overview of Prostatic Cancer Cases and Quality of BRCA1 and BRCA2 NGS Data from the FFPE Tissue.

Background: Comprehensive genomic profiling (CGP) has gained an important role in patients with advanced prostate cancer following the introduction of PARP inhibitors in daily clinical practice. Here, we report an overview of CGP results, specifically of BRCA1 and BRCA2 HRD-repair system genes, from patients with prostate cancer analyzed in our institution, and we compare our results with those available from more recent scientific literature. Methods: The study cohort consisted of 70 patients. Somatic DNA was extracted from Formalin-Fixed Paraffin-Embedded (FFPE) tissue using a MagCore Genomic DNA FFPE One-Step Kit for MagCore System. The DNA was quantified by EasyPGX® Real-Time qPCR and EasyPGX® Analysis Software (version 4.0.13). Tissue somatic DNA libraries were prepared with Myriapod® NGS BRCA1-2 panel-NG035 and sequenced in a Mi-Seq® System. The sequence alignment in hg19 and the variant calling were performed using Myriapod® NGS Data Analysis Software version 5.0.8 NG900-SW 5.0.8 with a software detection limit (LoD) of 95%. Variants with a coverage of 500 and VAF% ≥ 5 were evaluated. Results: Tumor tissue NGS was unsuccessful in 46/70 patients (66%). Mutations of the BRCA2 gene were detected in 4 of the samples: (1) BRCA2 ex10 c.1244A>G p.His415Arg VAF = 51.03%; (2) BRCA2 ex11 c.5946delT p.Ser1982fs VAF = 72.1%; (3) BRCA2 ex11 c.3302A>G p.His1101Arg VAF = 52.9%; and (4) BRCA2 ex11 c.3195_3198delTAAT p.Asn1066fs VAF = 51.1%. Conclusions: The results from our internal overview seem to support the data and to confirm the performance of the technical issues reported in the literature. Considering the advanced age of our patients, with 84% of men over the age of 65, the application of alternative and less invasive procedures such as liquid biopsy, could be a more suitable solution for some cases.

Ovarian carcinosarcomas: p53 status defines two distinct patterns of oncogenesis and outcomes.

Objectives: Ovarian carcinosarcoma (OCS) is a rare and lethal type of ovarian cancer. Despite its incredibly poor prognosis, it has received little research attention. In this study, we aim to evaluate the molecular features of OCS and elucidate their clinical significance. Study methods: We examined 30 OCS by immunohistochemistry (IHC) and targeted panel sequencing collected from a single institution (2003-2013) as the initial molecularly characterized cohort (Cohort A). From November 2016 to April 2023, we collected an additional 67 OCS cases from three institutions across British Columbia and Alberta as the contemporary cohort (Cohort B) for clinical correlation. The Kaplan-Meier method was used to estimate overall and progression-free survival, and differences in survival rates were compared using the log-rank test. All tests were two-sided. A p-value of less than 0.05 was considered statistically significant. Results: The majority of OCS (82%) in the initial Cohort A were p53-mutated, and the carcinomatous component displayed the histological and molecular features of a high-grade tubo-ovarian serous carcinoma (HGSC-like). In a minority of OCS, the epithelial components were characteristics of endometrioid or clear cell carcinomas, and IHC staining was wild type for p53. In the contemporary Cohort B, we observed the same histological findings related to the p53 IHC staining pattern. The median overall survival of the p53-mutated HGSC-like OCS (47 patients) was significantly higher (43.5 months) compared with that of the p53 wild-type OCS (10 patients, 8.8 months; P < 0.01). Pathogenic BRCA1/2 germline/somatic mutations were observed in 7 patients (17.5%) of HGSC-like OCS, and all these patients were alive at 3 years from diagnosis compared to a 51% 3-year survival among the patients with BRCA1/2 wild-type HGSC-like OCS (33 patients) (p = 0.022). Majority of patients (6/7) with BRCA1/2-mutated OCS received poly (ADP-ribose) polymerase inhibitor as maintenance therapy in this cohort. Conclusions: Most OCSs have a morphologic and molecular profile resembling HGSC; however, some OCSs display a molecular profile that suggests origin through non-serous oncogenic pathways. This molecular distinction has both prognostic and treatment (predictive) implications. These findings underscore the importance of routine p53 IHC testing on all OCS and BRCA1/2 testing on p53-mutated OCS.

Niraparib plays synergistic antitumor effects with NRT in a mouse ovarian cancer model with HRP.

OBJECTIVE: PARPi offers less clinical benefit for HRP patients compared to HRD patients. PARPi has an immunomodulatory function. NRT therapy targets tumor neoantigens without off-target immune toxicity. We explored the synergy between Niraparib and NRT in enhancing antitumor activity in an HRP ovarian cancer mouse model. METHODS: In the C57BL/6 mouse ID8 ovarian cancer model, the effect of Niraparib on reshaping TIME was evaluated by immune cell infiltration analysis of transcriptomic data. The antitumor effects of Niraparib, NRT, and their combined use were systematically evaluated. To corroborate alterations in TILs, TAMs, and chemokine profiles within the TIME, we employed immunofluorescence imaging and transcriptome sequencing analysis. RESULTS: Niraparib increased the M1-TAMs and activated CD8+ T cells in tumor tissues of C57BL/6 mice with ID8 ovarian cancer. GSEA showed that gene set associated with immature DC and INFα, cytokines and chemokines were significantly enriched in immune feature, KEGG and GO gene sets, meanwhile CCL5, CXCL9 and CXCL10 play dominant roles together. In the animal trials, combined group had a tumor growth delay compared with Niraparib group (P < 0.01) and control group (P < 0.001), and longer survival compared with the single agent group (P<0.01) . CONCLUSIONS: Niraparib could exert immune-reshaping effects, then acts synergistic antitumor effects with NRT in HRP ovarian cancer model. Our findings provide new ideas and rationale for combined immunotherapy in HRP ovarian cancer.

Role of poly-ADP-ribose polymerase inhibitors after brain progression in platinum-sensitive ovarian cancer: a case report and review of the literature.

Introduction: The incidence of brain metastases in ovarian cancer is quite rare, being approximately 1%-2%. According to retrospective studies, patients with BRCA 1/2 mutations present a higher risk. The trimodal approach based on surgery, radiotherapy, and chemotherapy presents better outcomes, but the prognosis remains poor with overall survival since the brain progression is around 1 year. Poly-ADP-ribose polymerase inhibitors (PARPi) have provided a new alternative for the management of advanced ovarian cancer. The SOLO2, NOVA, and ARIEL3 clinical trials do not refer data on patients with brain metastases, and the published evidence for PARPi in this setting comes only from case reports and retrospective studies. Case report: We present the case of a 54-year-old woman with stage IV ovarian high-grade serous papillary carcinoma who, after 37 months of treatment with olaparib, presented a single brain lesion. After radical treatment with surgery and adjuvant whole-brain radiotherapy, she resumed olaparib with no evidence of disease during 15 months. After a second single brain relapse treated with stereotactic radiosurgery, the patient continued olaparib beyond the brain progression with no evidence of extracranial disease. Despite that there were no changes in size or number of brain lesions, the neurological situation progressively worsened and the patient died 8 months after the second progression. Discussion: The higher incidence of brain metastases of ovarian cancer points out a possible tropism for the CNS in BRCA-mutated patients. In preclinical studies, PARPi has shown to cross the blood-brain barrier, with possible antitumor activity in the central nervous system (CNS) while maintaining control of extracranial disease. The best survival data are obtained with a trimodal approach, and adding a PARPi could improve the survival outcomes in the context of platinum-sensitivity disease. Targeted therapies combined with local treatments are also used in other malignancies, suggesting potential effectiveness due to tumor heterogeneity. PARPi before brain metastasis may delay its diagnosis, and using iPARP after brain metastases could improve the outcome of this population. Conclusion: The role that PARPi may have in the treatment of brain metastases of ovarian cancer requires more studies. In the context of radical treatment of brain metastasis (surgery and/or RT), with no evidence of extracranial disease, maintaining treatment with PARPi beyond the brain progression should be considered.

Combined strategies with PARP inhibitors for the treatment of BRCA wide type cancer.

Genomic instability stands out as a pivotal hallmark of cancer, and PARP inhibitors (PARPi) emerging as a groundbreaking class of targeted therapy drugs meticulously crafted to inhibit the repair of DNA single-strand breaks(SSB) in tumor cells. Currently, PARPi have been approved for the treatment of ovarian cancer, pancreatic cancer, breast cancer, and prostate cancer characterized by homologous recombination(HR) repair deficiencies due to mutations in BRCA1/2 or other DNA repair associated genes and acquiring the designation of breakthrough therapy. Nonetheless, PARPi exhibit limited efficacy in the majority of HR-proficient BRCA1/2 wild-type cancers. At present, the synergistic approach of combining PARPi with agents that induce HR defects, or with chemotherapy and radiotherapy to induce substantial DNA damage, significantly enhances the efficacy of PARPi in BRCA wild-type or HR-proficient patients, supporting extension the use of PARPi in HR proficient patients. Therefore, we have summarized the effects and mechanisms of the combined use of drugs with PARPi, including the combination of PARPi with HR defect-inducing drugs such as ATRi, CHKi, HR indirectly inducing drugs like VEGFRi, CDKi, immune checkpoint inhibitors and drugs instigating DNA damage such as chemotherapy or radiotherapy. In addition, this review discusses several ongoing clinical trials aimed at analyzing the clinical application potential of these combined treatment strategies.

Limitations of homologous recombination status testing and poly (ADP-ribose) polymerase inhibitor treatment in the current management of ovarian cancer.

Homologous recombination (HR) is a highly conserved DNA repair system, in which aberrations can lead to the accumulation of DNA damage and genomic scars known as homologous recombination deficiency (HRD). The identification of mutations in key genes (i.e., BRCA1, and BRCA2 (BRCA)) and the quantification of large-scale structural variants (e.g., loss of heterozygosity) are indicators of the HRD phenotype. HRD is a stable biomarker and remains unchanged during recurrence, but fails to reveal the molecular profile of tumor progression. Moreover, interpretation of the current HRD score lacks comprehensiveness, especially for the HR-proficient group. Poly (ADP-ribose) polymerase (PARP) enzymes play an important role in the repair of DNA single-strand breaks, the blockage of which using PARP inhibitors (PARPi) can generate synthetic lethality in cancer cells with HRD. Although numerous studies have demonstrated that the benefit of PARPi is substantial in ovarian cancer (OC) patients, the efficacy is limited by the development of resistance, and seems to be irrespective of HR and/or BRCA mutation status. Moreover, in addition to improving progression-free survival, long-term benefit as overall survival brought by PARPi for advanced, recurrent and refractory OC patients remains unclear. Therefore, further investigations are needed to uncover the role of HR genes beyond BRCA and their interactions with other oncogenic pathways, to determine the value of HRD in the recurrent setting, and to identify alternative strategies for the precise management of advanced, refractory OC patients.

Targeted Nanocarrier-Based Drug Delivery Strategies for Improving the Therapeutic Efficacy of PARP Inhibitors against Ovarian Cancer.

The current focus of ovarian cancer (OC) research is the improvement of treatment options through maximising drug effectiveness. OC remains the fifth leading cause of cancer-induced mortality in women worldwide. In recent years, nanotechnology has revolutionised drug delivery systems. Nanoparticles may be utilised as carriers in gene therapy or to overcome the problem of drug resistance in tumours by limiting the number of free drugs in circulation and thereby minimising undesired adverse effects. Cell surface receptors, such as human epidermal growth factor 2 (HER2), folic acid (FA) receptors, CD44 (also referred to as homing cell adhesion molecule, HCAM), and vascular endothelial growth factor (VEGF) are highly expressed in ovarian cancer cells. Generation of active targeting nanoparticles involves modification with ligands that recognise cell surface receptors and thereby promote internalisation by cancer cells. Several poly(ADP-ribose) polymerase (PARP) inhibitors (PARPi) are currently used for the treatment of high-grade serous ovarian carcinomas (HGSOC) or platinum-sensitive relapsed OC. However, PARP resistance and poor drug bioavailability are common challenges, highlighting the urgent need to develop novel, effective strategies for ovarian cancer treatment. This review evaluates the utility of nanoparticles in ovarian cancer therapy, with a specific focus on targeted approaches and the use of PARPi nanocarriers to optimise treatment outcomes.

CHD1L Regulates Cell Survival in Breast Cancer and Its Inhibition by OTI-611 Impedes the DNA Damage Response and Induces PARthanatos.

The Chromodomain helicase DNA-binding protein 1-like (CHD1L) is a nucleosome remodeling enzyme, which plays a key role in chromatin relaxation during the DNA damage response. Genome editing has shown that deletion of CHD1L sensitizes cells to PARPi, but the effect of its pharmacological inhibition has not been defined. Triple-negative breast cancer SUM149PT, HCC1937, and MDA-MB-231 cells were used to assess the mechanism of action of the CHD1Li OTI-611. Cytotoxicity as a single agent or in combination with standard-of-care treatments was assessed in tumor organoids. Immunofluorescence was used to assess the translocation of PAR and AIF to the cytoplasm or the nucleus and to study markers of DNA damage or apoptosis. Trapping of PARP1/2 or CHD1L onto chromatin was also assessed by in situ subcellular fractionation and immunofluorescence and validated by Western blot. We show that the inhibition of CHD1L's ATPase activity by OTI-611 is cytotoxic to triple-negative breast cancer tumor organoids and synergizes with PARPi and chemotherapy independently of the BRCA mutation status. The inhibition of the remodeling function blocks the phosphorylation of H2AX, traps CHD1L on chromatin, and leaves PAR chains on PARP1/2 open for hydrolysis. PAR hydrolysis traps PARP1/2 at DNA damage sites and mediates PAR translocation to the cytoplasm, release of AIF from the mitochondria, and induction of PARthanatos. The targeted inhibition of CHD1L's oncogenic function by OTI-611 signifies an innovative therapeutic strategy for breast cancer and other cancers. This approach capitalizes on CHD1L-mediated DNA repair and cell survival vulnerabilities, thereby creating synergy with standard-of-care therapies.

Real-world data on the prevalence of BRCA1/2 and HRR gene mutations in patients with primary and metastatic castration resistant prostate cancer.

PURPOSE: This study seeks to contribute real-world data on the prevalence of BRCA1/2 and HRR gene mutations in prostate cancer. METHODS: We compiled sequencing data of 197 cases of primary and metastatic prostate cancer, in which HRR mutation analysis was performed upon clinical request within the last 5 years. All cases were analyzed using a targeted NGS BRCAness multigene panel, including 8 HRR genes (ATM, BRCA1, BRCA2, CDK12, CHEK2, FANCA, HDAC2, PALB2). RESULTS: Our findings reveal a prevalence of potentially targetable mutations based on FDA criteria of 20.8%, which is comparable to the literature. However, the frequency of targetable BRCA2 mutations within our cohort was lower than reported for mCRPC and ATM and CHEK2 mutations were more prevalent instead. Thus, while 20.8% (n = 38) of the cases meet the criteria for olaparib treatment per FDA approval, only 4.9% (n = 9) align with the eligibility criteria according to the EMA approval. CONCLUSION: This study offers valuable real-world insights into the landscape of BRCA1/2 and HRR gene mutations and the practical clinical management of HRR gene testing in prostate cancer, contributing to a better understanding of patient eligibility for PARPi treatment.