PARP inhibitors and epithelial ovarian cancer: Molecular mechanisms, clinical development and future prospective

Poly (ADP-ribose) polymerase (PARP) inhibitors as anticancer agents: An outlook on clinical progress, synthetic strategies, biological activity, and structure-activity relationship

Poly (ADP-ribose) polymerase (PARP) is considered an essential component in case of DNA (Deoxyribonucleic acid) damage, response by sensing DNA damage and engaging DNA repair proteins. Those proteins repair the damaged DNA via an aspect of posttranslational modification, known as poly (ADP-Ribosyl)ation (PARylation). Specifically, PARP inhibitors (PARPi) have shown better results when administered alone in a variety of cancer types with BRCA (Breast Cancer gene) mutation. The clinical therapeutic benefits of PARP inhibitors have been diminished by their cytotoxicity, progression of drug resistance, and limitation of indication, regardless of their tremendous clinical effectiveness. A growing number of PARP-1 inhibitors, particularly those associated with BRCA-1/2 mutations, have been identified as potential cancer treatments. Recently, several researchers have identified various promising scaffolds, which have resulted in the resuscitation of the faith in PARP inhibitors as cancer therapies. This review provided a comprehensive update on the anatomy and physiology of the PARP enzyme, the profile of FDA (Food and Drug Administration) and CFDA (China Food and Drug Administration)-approved drugs, and small-molecule inhibitors of PARP, including their synthetic routes, biological evaluation, selectivity, and structure-activity relationship.

Targeted inhibition of the ATR/CHK1 pathway overcomes resistance to olaparib and dysregulates DNA damage response protein expression in BRCA2MUT ovarian cancer cells

Olaparib is a PARP inhibitor (PARPi) approved for targeted treatment of ovarian cancer (OC). However, its efficacy is impeded by the inevitable occurrence of resistance. Here, we investigated whether the cytotoxic activity of olaparib could be synergistically enhanced in olaparib-resistant OC cells with BRCA2 reversion mutation by the addition of inhibitors of the ATR/CHK1 pathway. Moreover, we provide insights into alterations in the DNA damage response (DDR) pathway induced by combination treatments. Antitumor activity of olaparib alone or combined with an ATR inhibitor (ATRi, ceralasertib) or CHK1 inhibitor (CHK1i, MK-8776) was evaluated in OC cell lines sensitive (PEO1, PEO4) and resistant (PEO1-OR) to olaparib. Antibody microarrays were used to explore changes in expression of 27 DDR-related proteins. Olaparib in combination with ATR/CHK1 inhibitors synergistically induced a decrease in viability and clonogenic survival and an increase in apoptosis mediated by caspase-3/7 in all OC cells. Combination treatments induced cumulative alterations in expression of DDR-related proteins mediating distinct DNA repair pathways and cell cycle control. In the presence of ATRi and CHK1i, olaparib-induced upregulation of proteins determining cell fate after DNA damage (PARP1, CHK1, c-Abl, Ku70, Ku80, MDM2, and p21) was abrogated in PEO1-OR cells. Overall, the addition of ATRi or CHK1i to olaparib effectively overcomes resistance to PARPi exerting anti-proliferative effect in BRCA2MUT olaparib-resistant OC cells and alters expression of DDR-related proteins. These new molecular insights into cellular response to olaparib combined with ATR/CHK1 inhibitors might help improve targeted therapies for olaparib-resistant OC.

Machine Learning Quantification of Intraepithelial Tumor-Infiltrating Lymphocytes as a Significant Prognostic Factor in High-Grade Serous Ovarian Carcinomas

The prognostic and predictive role of tumor-infiltrating lymphocytes (TILs) has been demonstrated in various neoplasms. The few publications that have addressed this topic in high-grade serous ovarian carcinoma (HGSOC) have approached TIL quantification from a semiquantitative standpoint. Clinical correlation studies, therefore, need to be conducted based on more accurate TIL quantification. We created a machine learning system based on H&E-stained sections using 76 molecularly and clinically well-characterized advanced HGSOC. This system enabled immune cell classification. These immune parameters were subsequently correlated with overall survival (OS) and progression-free survival (PFI). An intense colonization of the tumor cords by TILs was associated with a better prognosis. Moreover, the multivariate analysis showed that the intraephitelial (ie) TILs concentration was an independent and favorable prognostic factor both for OS (p = 0.02) and PFI (p = 0.001). A synergistic effect between complete surgical cytoreduction and high levels of ieTILs was evidenced, both in terms of OS (p = 0.0005) and PFI (p = 0.0008). We consider that digital analysis with machine learning provided a more accurate TIL quantification in HGSOC. It has been demonstrated that ieTILs quantification in H&E-stained slides is an independent prognostic parameter. It is possible that intraepithelial TIL quantification could help identify candidate patients for immunotherapy.

Synergistic cytotoxicity of irinotecan combined with polysaccharide-based nanoparticles for colorectal carcinoma

Functional polymeric nanoparticles (NPs) with antitumor potential were combined with the topoisomerase I inhibitor, irinotecan (IRT), to enhance cytotoxicity against colorectal cancers. The negatively charged γ-polyglutamic acid (γ-PGA) or fucoidan (FCD) was complexed with the positively charged chitosan (CS) to encapsulate IRT. The size of the γ-PGA/CS/IRT NPs and FCD/CS/IRT NPs were 146.0 ± 8.0 nm and 230.8 ± 2.5 nm, respectively, with polydispersity index ≤0.3. The cellular uptake ability of FCD/CS-FITC NPs was better than that of γ-PGA/CS-FITC NPs, especially in p-selectin positive HCT116 colorectal cancer cells (4.8 ± 0.8 μg/mL vs 11.4 ± 2.2 μg/mL). The IC50 of FCD/CS/IRT NPs was 2.4 times lower than that of γ-PGA/CS/IRT NPs in HCT116 cells (4.8 ± 0.8 μg/mL vs 11.4 ± 2.2 μg/mL), indicating its superior antitumor potential. The combination of irinotecan and fucoidan-based NPs exhibited a synergistic effect (CI <1), resulting in better anticancer activity of FCD/CS/IRT NPs than irinotecan alone. The apoptosis-related proteins, caspase 3, caspase 9, and poly(ADP-ribose) polymerase (PARP), were prominently increased in FCD/CS/IRT NPs-treated HCT116 cells by 2.3 folds, 3.5 folds, and 6.3 folds, respectively. All results support that fucoidan-based irinotecan-loaded nanoparticles possess the ability to effectively enhance cellular uptake and induce synergistic apoptosis of colorectal cancer cells.

Small-Molecule-Mediated Stabilization of PP2A Modulates the Homologous Recombination Pathway and Potentiates DNA Damage-Induced Cell Death

High-grade serous carcinoma (HGSC) is the most common and lethal ovarian cancer subtype. PARP inhibitors (PARPi) have become the mainstay of HGSC-targeted therapy, given that these tumors are driven by a high degree of genomic instability (GI) and homologous recombination (HR) defects. Nonetheless, approximately 30% of patients initially respond to treatment, ultimately relapsing with resistant disease. Thus, despite recent advances in drug development and an increased understanding of genetic alterations driving HGSC progression, mortality has not declined, highlighting the need for novel therapies. Using a small-molecule activator of protein phosphatase 2A (PP2A; SMAP-061), we investigated the mechanism by which PP2A stabilization induces apoptosis in patient-derived HGSC cells and xenograft (PDX) models alone or in combination with PARPi. We uncovered that PP2A genes essential for cellular transformation (B56α, B56γ, and PR72) and basal phosphatase activity (PP2A-A and -C) are heterozygously lost in the majority of HGSC. Moreover, loss of these PP2A genes correlates with worse overall patient survival. We show that SMAP-061-induced stabilization of PP2A inhibits the HR output by targeting RAD51, leading to chronic accumulation of DNA damage and ultimately apoptosis. Furthermore, combination of SMAP-061 and PARPi leads to enhanced apoptosis in both HR-proficient and HR-deficient HGSC cells and PDX models. Our studies identify PP2A as a novel regulator of HR and indicate PP2A modulators as a therapeutic therapy for HGSC. In summary, our findings further emphasize the potential of PP2A modulators to overcome PARPi insensitivity, given that targeting RAD51 presents benefits in overcoming PARPi resistance driven by BRCA1/2 mutation reversions.

The natural killer cell immunotherapy platform: an overview of the landscape of clinical trials in liquid and solid tumors

The translation of natural killer (NK) cells to the treatment of malignant disease has made significant progress in the last few decades. With a variety of available sources and improvements in both in vitro and in vivo NK cell expansion, the NK cell immunotherapy platform has come into its own. The enormous effort continues to further optimize this platform, including ways to enhance NK cell persistence, trafficking to the tumor microenvironment, and cytotoxicity. As this effort bears fruit, it is translated into a plethora of clinical trials in patients with advanced malignancies. The adoptive transfer of NK cells, either as a standalone therapy or in combination with other immunotherapies, has been applied for the treatment of both liquid and solid tumors, with numerous early-phase trials showing promising results. This review aims to summarize the key advantages of NK cell immunotherapy, highlight several of the current approaches being taken for its optimization, and give an overview of the landscape of clinical trials translating this platform into clinic.

The Molecular Mechanisms of Actions, Effects, and Clinical Implications of PARP Inhibitors in Epithelial Ovarian Cancers: A Systematic Review

Ovarian cancer is the most lethal gynecologic malignancy in the United States. Some patients affected by ovarian cancers often present genome instability with one or more of the defects in DNA repair pathways, particularly in homologous recombination (HR), which is strictly linked to mutations in breast cancer susceptibility gene 1 (BRCA 1) or breast cancer susceptibility gene 2 (BRCA 2). The treatment of ovarian cancer remains a challenge, and the majority of patients with advanced-stage ovarian cancers experience relapse and require additional treatment despite initial therapy, including optimal cytoreductive surgery (CRS) and platinum-based chemotherapy. Targeted therapy at DNA repair genes has become a unique strategy to combat homologous recombination-deficient (HRD) cancers in recent years. Poly (ADP-ribose) polymerase (PARP), a family of proteins, plays an important role in DNA damage repair, genome stability, and apoptosis of cancer cells, especially in HRD cancers. PARP inhibitors (PARPi) have been reported to be highly effective and low-toxicity drugs that will tremendously benefit patients with HRD (i.e., BRCA 1/2 mutated) epithelial ovarian cancer (EOC) by blocking the DNA repair pathways and inducing apoptosis of cancer cells. PARP inhibitors compete with NAD⁺ at the catalytic domain (CAT) of PARP to block PARP catalytic activity and the formation of PAR polymers. These effects compromise the cellular ability to overcome DNA SSB damage. The process of HR, an essential error-free pathway to repair DNA DSBs during cell replication, will be blocked in the condition of BRCA 1/2 mutations. The PARP-associated HR pathway can also be partially interrupted by using PARP inhibitors. Grossly, PARP inhibitors have demonstrated some therapeutic benefits in many randomized phase II and III trials when combined with the standard CRS for advanced EOCs. However, similar to other chemotherapy agents, PARP inhibitors have different clinical indications and toxicity profiles and also face drug resistance, which has become a major challenge. In high-grade epithelial ovarian cancers, the cancer cells under hypoxia- or drug-induced stress have the capacity to become polyploidy giant cancer cells (PGCCs), which can survive the attack of chemotherapeutic agents and start endoreplication. These stem-like, self-renewing PGCCs generate mutations to alter the expression/function of kinases, p53, and stem cell markers, and diploid daughter cells can exhibit drug resistance and facilitate tumor growth and metastasis. In this review, we discuss the underlying molecular mechanisms of PARP inhibitors and the results from the clinical studies that investigated the effects of the FDA-approved PARP inhibitors olaparib, rucaparib, and niraparib. We also review the current research progress on PARP inhibitors, their safety, and their combined usage with antiangiogenic agents. Nevertheless, many unknown aspects of PARP inhibitors, including detailed mechanisms of actions, along with the effectiveness and safety of the treatment of EOCs, warrant further investigation.

Niraparib treatment for patients with BRCA-mutated ovarian cancer: review of clinical data and therapeutic context

We reviewed clinical data for niraparib monotherapy in BRCA-mutated (BRCAm) epithelial ovarian cancer (OC), contextualizing results with data from other poly(ADP-ribose) polymerase inhibitors (PARPis). Niraparib reduced the likelihood of progression or death by 60% as first-line maintenance therapy and by 73-78% in recurrent disease. In heavily pretreated OC, efficacy was greater in the BRCAm versus non-BRCAm cohort. Quality-of-life (QoL) was maintained throughout treatment. Adverse events were consistent with the known niraparib safety profile. Cumulative efficacy, safety and QoL evidence demonstrate niraparib maintenance monotherapy has a positive benefit:risk ratio in BRCAm OC. Niraparib significantly improved progression-free survival as first-line maintenance therapy in all patients with OC (i.e., of any biomarker status).

Advances in the Application of Radionuclide-Labeled HER2 Affibody for the Diagnosis and Treatment of Ovarian Cancer

Human epidermal growth factor receptor 2 (HER2) is a highly expressed tumor marker in epithelial ovarian cancer, and its overexpression is considered to be a potential factor of poor prognosis. Therefore, monitoring the expression of HER2 receptor in tumor tissue provides favorable conditions for accurate localization, diagnosis, targeted therapy, and prognosis evaluation of cancer foci. Affibody has the advantages of high affinity, small molecular weight, and stable biochemical properties. The molecular probes of radionuclide-labeled HER2 affibody have recently shown broad application prospects in the diagnosis and treatment of ovarian cancer; the aim is to introduce radionuclides into the cancer foci, display systemic lesions, and kill tumor cells through the radioactivity of the radionuclides. This process seamlessly integrates the diagnosis and treatment of ovarian cancer. Current research and development of new molecular probes of radionuclide-labeled HER2 affibody should focus on overcoming the deficiencies of non-specific uptake in the kidney, bone marrow, liver, and gastrointestinal tract, and on reducing the background of the image to improve image quality. By modifying the amino acid sequence; changing the hydrophilicity, surface charge, and lipid solubility of the affibody molecule; and using different radionuclides, chelating agents, and labeling conditions to optimize the labeling method of molecular probes, the specific uptake of molecular probes at tumor sites will be improved, while reducing radioactive retention in non-target organs and obtaining the best target/non-target value. These measures will enable the clinical use of radionuclide-labeled HER2 affibody molecular probes as soon as possible, providing a new clinical path for tumor-specific diagnosis, targeted therapy, and efficacy evaluation. The purpose of this review is to describe the application of radionuclide-labeled HER2 affibody in the imaging and treatment of ovarian cancer, including its potential clinical value and dilemmas.

SIK2 inhibition enhances PARP inhibitor activity synergistically in ovarian and triple-negative breast cancers

Poly(ADP-ribose) polymerase inhibitors (PARP inhibitors) have had an increasing role in the treatment of ovarian and breast cancers. PARP inhibitors are selectively active in cells with homologous recombination DNA repair deficiency caused by mutations in BRCA1/2 and other DNA repair pathway genes. Cancers with homologous recombination DNA repair proficiency respond poorly to PARP inhibitors. Cancers that initially respond to PARP inhibitors eventually develop drug resistance. We have identified salt-inducible kinase 2 (SIK2) inhibitors, ARN3236 and ARN3261, which decreased DNA double-strand break (DSB) repair functions and produced synthetic lethality with multiple PARP inhibitors in both homologous recombination DNA repair deficiency and proficiency cancer cells. SIK2 is required for centrosome splitting and PI3K activation and regulates cancer cell proliferation, metastasis, and sensitivity to chemotherapy. Here, we showed that SIK2 inhibitors sensitized ovarian and triple-negative breast cancer (TNBC) cells and xenografts to PARP inhibitors. SIK2 inhibitors decreased PARP enzyme activity and phosphorylation of class-IIa histone deacetylases (HDAC4/5/7). Furthermore, SIK2 inhibitors abolished class-IIa HDAC4/5/7-associated transcriptional activity of myocyte enhancer factor-2D (MEF2D), decreasing MEF2D binding to regulatory regions with high chromatin accessibility in FANCD2, EXO1, and XRCC4 genes, resulting in repression of their functions in the DNA DSB repair pathway. The combination of PARP inhibitors and SIK2 inhibitors provides a therapeutic strategy to enhance PARP inhibitor sensitivity for ovarian cancer and TNBC.

Prevalence of Clinically Relevant Germline BRCA Variants in a Large Unselected South African Breast and Ovarian Cancer Cohort: A Public Sector Experience

Breast cancer is a multifaceted disease that currently represents a leading cause of death in women worldwide. Over the past two decades (1998–2020), the National Health Laboratory Service’s Human Genetics Laboratory in central South Africa screened more than 2,974 breast and/or ovarian cancer patients for abnormalities characteristic of the widely known familial breast cancer genes, Breast Cancer gene 1 (BRCA1) and Breast Cancer gene 2 (BRCA2). Patients were stratified according to the presence of family history, age at onset, stage of the disease, ethnicity and mutation status relative to BRCA1/2. Collectively, 481 actionable (likely-to pathogenic) variants were detected in this cohort among the different ethnic/racial groups. A combination of old (pre-2014) and new (post-2014) laboratory techniques was used to identify these variants. Additionally, targeted genotyping was performed as translational research revealed the first three recurrent South African pathogenic variants, namely BRCA1 c.1374del (legacy name 1493delC), BRCA1 c.2641G&gt;T (legacy name E881X) and BRCA2 c.7934del (legacy name 8162delG). This initial flagship study resulted in a cost-effective diagnostic test that enabled screening of a particular ethnic group for these variants. Since then, various non-Afrikaner frequent variants were identified that were proven to represent recurrent variants. These include BRCA2 c.5771_5774del (legacy name 5999del4) and BRCA2 c.582G&gt;A, both Black African founder mutations. By performing innovative translational research, medical science in South Africa can adopt first-world technologies into its healthcare context as a developing country. Over the past two decades, the progress made in the public sector enabled a pivotal shift away from population-directed genetic testing to the screening of potentially all breast and ovarian cancer patients, irrespective of ethnicity, family history or immunohistochemical status. The modifications over the years complied with international standards and guidelines aimed at universal healthcare for all. This article shares all the cohort stratifications and the likely-to pathogenic variants detected.

Homologous Recombination Deficiencies and Hereditary Tumors

Homologous recombination (HR) is a vital process for repairing DNA double-strand breaks. Germline variants in the HR pathway, comprising at least 10 genes, such as BRCA1, BRCA2, ATM, BARD1, BRIP1, CHEK2, NBS1(NBN), PALB2, RAD51C, and RAD51D, lead to inherited susceptibility to specific types of cancers, including those of the breast, ovaries, prostate, and pancreas. The penetrance of germline pathogenic variants of each gene varies, whereas all their associated protein products are indispensable for maintaining a high-fidelity DNA repair system by HR. The present review summarizes the basic molecular mechanisms and components that collectively play a role in maintaining genomic integrity against DNA double-strand damage and their clinical implications on each type of hereditary tumor.

Peripheral Neuropathy under Oncologic Therapies: A Literature Review on Pathogenetic Mechanisms

Peripheral neurologic complications are frequent adverse events during oncologic treatments and often lead to dose reduction, administration delays with time elongation of the therapeutic plan and, not least, worsening of patients’ quality of life. Experience skills are required to recognize symptoms and clinical evidences and the collaboration between different health professionals, in particular oncologists and hospital pharmacists, grants a correct management of this undesirable occurrence. Some classes of drugs (platinates, vinca alkaloids, taxanes) typically develop this kind of side effect, but the genesis of chemotherapy-induced peripheral neuropathy is not linked to a single mechanism. This paper aims from one side at summarizing and explaining all the scattering mechanisms of chemotherapy-induced peripheral neuropathy through a detailed literature revision, on the other side at finding new approaches to possible treatments, in order to facilitate the collaboration between oncologists, hematologists and hospital pharmacists.

Expression of PAWR predicts prognosis of ovarian cancer

Background

Ovarian cancer greatly threatens the general health of women worldwide. Implementation of predictive prognostic biomarkers aids in ovarian cancer management.

Methods

Using online databases, the general expression profile, target-disease associations, and interaction network of PAWR were explored. To identify the role of PAWR in ovarian cancer, gene correlation analysis, survival analysis, and combined analysis of drug responsiveness and PAWR expression were performed. The predictive prognostic value of PAWR was further validated in clinical samples.

Results

PAWR was widely expressed in normal and cancer tissues, with decreased expression in ovarian cancer tissues compared with normal tissues. PAWR was associated with various cancers including ovarian cancer. PAWR formed a regulatory network with a group of proteins and correlated with several genes, which were both implicated in ovarian cancer and drug responsiveness. High PAWR expression denoted better survival in ovarian cancer patients (OS: HR = 0.84, P = 0.0077; PFS, HR = 0.86, P = 0.049). Expression of PAWR could predict platinum responsiveness in ovarian cancer and there was a positive correlation between PAWR gene effect and paclitaxel sensitivity. In 12 paired clinical samples, the cancerous tissues exhibited significantly lower PAWR expression than matched normal fallopian tubes. The predictive prognostic value of PAWR was maintained in a cohort of 50 ovarian cancer patients.

Conclusions

High PAWR expression indicated better survival and higher drug responsiveness in ovarian cancer patients. PAWR could be exploited as a predictive prognostic biomarker in ovarian cancer.