The potential of PARP inhibitors in targeted cancer therapy and immunotherapy

Parps in immune response: Potential targets for cancer immunotherapy

Immunotherapy in clinical application faces numerous challenges pertaining to both effectiveness and safety. Poly(ADP-ribose) polymerases (PARPs) exhibit multifunctional characteristics by transferring ADP-ribose units to target proteins or nucleic acids. In recent years, more and more attention has been paid to the biological function of PARPs in immune response. This article reviews the relationship between PARP family members and immune response. PARP1 and PARP2 inhibit anti-tumor immune activity by regulating immune checkpoint expression and the cGAS/STING signaling pathway. PARP7 and PARP11 play an important role in promoting immunosuppressive tumor microenvironment. PARP9 promotes the production of Type I interferon and the infiltration of macrophages. PARP13 is a key tumor suppressor that promotes anti-tumor immune response. PARP14 plays a crucial role in promoting the differentiation of macrophages towards the M2 pro-tumor phenotype. Summarizing the molecular mechanisms of PARP7, PARP9, PARP11, PARP13 and PARP14 in regulating immune response is helpful to deepen our comprehension of the role of PARPs in immune function regulation. This provides a reference and basis for targeted PARP-based cancer treatment strategies and drug development. PARP1, PARP7 inhibitors or other PARP inhibitors in combination with immune checkpoint inhibitors or other immunotherapy strategies may be a more effective cancer therapy.

Pretargeted alpha therapy in MUC16-positive high-grade serous ovarian cancer

BACKGROUND

Peritoneal metastasis with micrometastatic cell clusters is a common feature of advanced ovarian cancer. Targeted alpha therapy (TAT) is an attractive approach for treating micrometastatic diseases as alpha particles release enormous amounts of energy within a short distance. A pretargeting approach - leveraging the inverse-electron-demand Diels-Alder reaction between tetrazines (Tz) and trans-cyclooctene (TCO) - can minimize off-target toxicity related to TAT, often associated with full-length antibodies. We hypothesized that a pretargeting strategy could effectively treat high-grade serous (HGS) ovarian tumors while minimizing toxicity.

METHODS

We utilized the humanized antibody, AR9.6, labeled with actinium-225 (225Ac). AR9.6 targets fully glycosylated and hypoglycosylated isoforms of MUC16. For biodistribution and radioimmunotherapy studies, AR9.6-TCO was injected into OVCAR3-bearing mice 72 h before administering [225Ac]Ac-mcp-PEG8-Tz, e.g. using a 1,2,4,5-tetrazine conjugated to the macropa chelator via a polyethylene glycol (PEG) linker.

RESULTS

Biodistribution data revealed that the pretargeting approach achieved substantial tumor uptake. Cerenkov luminescence imaging confirmed successful in vivo pretargeting during TAT studies. Compared to the control groups, TAT with AR9.6-TCO and [225Ac]Ac-mcp-PEG8-Tz significantly suppressed tumor growth and improved overall survival in OVCAR3 tumor-bearing mice. Renal and ovarian pathology compatible with toxicity was observed in mice in addition to transient hematologic toxicity.

CONCLUSION

We confirmed that pretargeting with AR9.6-TCO and [225Ac]Ac-mcp-PEG8-Tz has durable antitumor effects in high MUC16-expressing tumors. These findings demonstrate great potential for using pretargeting in combination with TAT for the treatment of ovarian cancer.

CLASSIFICATION

Biological Sciences; Applied Biological Sciences.

PARP-1 Inhibition Increases Oxidative Stress in Ets-1-Expressing MDA-MB-231 Breast Cancer Cells

BACKGROUND

The Ets-1 transcription factor plays a primordial role in regulating the expression of numerous genes implicated in cancer progression. In a previous study, we revealed that poly(ADP-ribose) polymerase-1 (PARP-1) inhibition by PJ-34 results in Ets-1 level increase in cells, which is related with cell death of Ets-1-expressing cancer cells.

AIMS

The mechanism of the antitumor effect of PARP-1 inhibition was investigated in the Ets-1-expressing MDA-MB-231 breast cancer cells.

METHODS AND RESULTS

We tested the effects of four PARP inhibitors (PARPi) (PJ-34, Veliparib, Olaparib, and Rucaparib). We first demonstrated that PARPi reduced cells growth through G2/M cell cycle arrest. Next, we evaluated PARP-1 inhibition effect on oxidative DNA damage in Ets-1-overexpressing and Ets-1-non-expressing breast cancer cells and we showed that PARPi led only Ets-1-overexpressing cells to accumulate it, which triggers the DNA damage response as revealed by the increase in the level of a panel of DNA damage-related proteins. Importantly, we demonstrated that PARPi increased reactive oxygen species (ROS), only in Ets-1-overexpressing cells and this is accompanied by upregulation of p47phox expression, a subunit of the NAPDH oxidase (NOX).

CONCLUSION

These preliminary findings correlate PARPi-induced oxidative DNA damage/oxidative stress to Ets-1 expression in breast cancer cells.

Advancing personalized medicine: Integrating statistical algorithms with omics and nano-omics for enhanced diagnostic accuracy and treatment efficacy

Medical laboratory services enable precise measurement of thousands of biomolecules and have become an inseparable part of high-quality healthcare services, exerting a profound influence on global health outcomes. The integration of omics technologies into laboratory medicine has transformed healthcare, enabling personalized treatments and interventions based on individuals' distinct genetic and metabolic profiles. Interpreting laboratory data relies on reliable reference values. Presently, population-derived references are used for individuals, risking misinterpretation due to population heterogeneity, and leading to medical errors. Thus, personalized references are crucial for precise interpretation of individual laboratory results, and the interpretation of omics data should be based on individualized reference values. We reviewed recent advancements in personalized laboratory medicine, focusing on personalized omics, and discussed strategies for implementing personalized statistical approaches in omics technologies to improve global health and concluded that personalized statistical algorithms for interpretation of omics data have great potential to enhance global health. Finally, we demonstrated that the convergence of nanotechnology and omics sciences is transforming personalized laboratory medicine by providing unparalleled diagnostic precision and innovative therapeutic strategies.

PARP inhibitor resistance mechanisms and PARP inhibitor derived imaging probes

INTRODUCTION

Poly(ADP-ribose) polymerase 1 (PARP1) inhibition has become a major target in anticancer therapy. While PARP inhibitors (PARPi) are approved for homologous recombination (HR) deficient cancers, therapeutic resistance is a challenge and PARPi are now being investigated in cancers lacking HR deficiencies. This creates a need to develop molecular and imaging biomarkers of PARPi response to improve patient selection and circumvent therapeutic resistance.

AREAS COVERED

PubMed and clinicaltrials.gov were queried for studies on PARPi resistance and imaging. This review summarizes established and emerging resistance mechanisms to PARPi, and the current state of imaging and theragnostic probes for PARPi, including fluorescently labeled and radiolabeled probes.

EXPERT OPINION

While progress has been made in understanding PARPi therapeutic resistance, clinical evidence remains lacking and relatively little is known regarding PARPi response outside of HR deficiencies. Continued research will clarify the importance of known biomarkers and resistance mechanisms in patient cohorts and the broader utility of PARPi. Progress has also been made in PARPi imaging, particularly with radiolabeled probes, and both imaging and theragnostic probes have now reached clinical validation. Reducing abdominal background signal from probe clearance will broaden their applicability, and improvements to molecular synthesis and radiation delivery will increase their utility.

DNA damage response in breast cancer and its significant role in guiding novel precise therapies

DNA damage response (DDR) deficiency has been one of the emerging targets in treating breast cancer in recent years. On the one hand, DDR coordinates cell cycle and signal transduction, whose dysfunction may lead to cell apoptosis, genomic instability, and tumor development. Conversely, DDR deficiency is an intrinsic feature of tumors that underlies their response to treatments that inflict DNA damage. In this review, we systematically explore various mechanisms of DDR, the rationale and research advances in DDR-targeted drugs in breast cancer, and discuss the challenges in its clinical applications. Notably, poly (ADP-ribose) polymerase (PARP) inhibitors have demonstrated favorable efficacy and safety in breast cancer with high homogenous recombination deficiency (HRD) status in a series of clinical trials. Moreover, several studies on novel DDR-related molecules are actively exploring to target tumors that become resistant to PARP inhibition. Before further clinical application of new regimens or drugs, novel and standardized biomarkers are needed to develop for accurately characterizing the benefit population and predicting efficacy. Despite the promising efficacy of DDR-related treatments, challenges of off-target toxicity and drug resistance need to be addressed. Strategies to overcome drug resistance await further exploration on DDR mechanisms, and combined targeted drugs or immunotherapy will hopefully provide more precise or combined strategies and expand potential responsive populations.

Molecular mechanisms of sensitivity and resistance to radiotherapy

The molecular mechanisms underlying sensitivity and resistance to radiotherapy is an area of active investigation and discovery as its clinical applications have the potential to improve cancer patients' outcomes. In addition to the traditional pathways of radiation biology, our knowledge now includes molecular pathways of radiation sensitivity and resistance which have provided insights into potential targets for enhancing radiotherapy efficacy. Sensitivity to radiotherapy is influenced by the intricate interplay of various molecular mechanisms involved in DNA damage repair, apoptosis, cellular senescence, and epigenetics. Translationally, there have been several successful applications of this new knowledge into the clinic, such as biomarkers for improved response to chemo-radiation. New therapies to modify radiation response, such as the poly (ADP-ribose) polymerase (PARP) inhibitors, derived from research on DNA repair pathways leading to radiotherapy resistance, are being used clinically. In addition, p53-mediated pathways are critical for DNA damage related apoptosis, cellular senescence, and cell cycle arrest. As the understanding of genetic markers, molecular profiling, molecular imaging, and functional assays improve, these advances once translated clinically, will help propel modern radiation therapy towards more precise and individualized practices.

Progression of monoclonal gammopathy of undetermined significance to multiple myeloma is associated with enhanced translational quality control and overall loss of surface antigens

BACKGROUND

Despite significant advancements in treatment strategies, multiple myeloma remains incurable. Additionally, there is a distinct lack of reliable biomarkers that can guide initial treatment decisions and help determine suitable replacement or adjuvant therapies when relapse ensues due to acquired drug resistance.

METHODS

To define specific proteins and pathways involved in the progression of monoclonal gammopathy of undetermined significance (MGUS) to multiple myeloma (MM), we have applied super-SILAC quantitative proteomic analysis to CD138 + plasma cells from 9 individuals with MGUS and 37 with MM.

RESULTS

Unsupervised hierarchical clustering defined three groups: MGUS, MM, and MM with an MGUS-like proteome profile (ML) that may represent a group that has recently transformed to MM. Statistical analysis identified 866 differentially expressed proteins between MM and MGUS, and 189 between MM and ML, 177 of which were common between MGUS and ML. Progression from MGUS to MM is accompanied by upregulated EIF2 signaling, DNA repair, and proteins involved in translational quality control, whereas integrin- and actin cytoskeletal signaling and cell surface markers are downregulated.

CONCLUSION

Compared to the premalignant plasma cells in MGUS, malignant MM cells apparently have mobilized several pathways that collectively contribute to ensure translational fidelity and to avoid proteotoxic stress, especially in the ER. The overall reduced expression of immunoglobulins and surface antigens contribute to this and may additionally mediate evasion from recognition by the immune apparatus. Our analyses identified a range of novel biomarkers with potential prognostic and therapeutic value, which will undergo further evaluation to determine their clinical significance.

Personalized treatment with PARP inhibitors in advanced urothelial carcinoma: a case report and literature review

Bladder cancer (BC) poses a significant health challenge, particularly in metastatic cases, where the prognosis is unfavorable and therapeutic options are limited. Poly ADP-ribose polymerase (PARP) inhibitors have gained approval for use in various cancer types, but their application in BC remains controversial, despite the notable prevalence of DNA damage response alterations in advanced or metastatic urothelial carcinomas. In this report, we describe a 66-year-old heavy-smoking female diagnosed with muscle-invasive BC. She underwent multiple rounds of chemotherapy and radiation, yet her disease remained poorly controlled, leading to metastasis in the left obturator internus muscle. Comprehensive genomic profiling through FoundationOne® Liquid CDx, examining a 324-gene panel using circulating tumor DNA from blood samples, revealed a pathogenic ATM gene alteration (p.Q654fs*10, c.1960delC), suggesting potential eligibility for PARP inhibitor therapy. Remarkably, the patient achieved a complete response to talazoparib, prompting an optimal investigation into BC candidates for this promising therapy.

Inhibition of ATM promotes PD-L1 expression by activating JNK/c-Jun/TNF-α signaling axis in triple-negative breast cancer

Triple-negative breast cancer (TNBC) is a heterogeneous subtype of breast cancer. Anti-PD-1/PD-L1 treatment for advanced TNBC is still limited to PD-L1-positive patients. Ataxia telangiectasia mutated (ATM) is a switch molecule for homologous recombination and repair. In this study, we found a significant negative correlation between ATM and PD-L1 in 4 TNBC clinical specimens by single-cell RNA sequencing (scRNA-seq), which was confirmed by immunochemical staining in 86 TNBC specimens. We then established ATM knockdown TNBC stable cell lines to perform in vitro studies and animal experiments, proving the negative regulation of PD-L1 by ATM via suppression of tumor necrosis factor-alpha (TNF-α), which was confirmed by cytokine array analysis of TNBC cell line and analysis of clinical specimens. We further found that ATM inhibits TNF-α via inactivating JNK/c-Jun by scRNA-seq, Western blot and luciferase reporter assays. Finally, we identified a negative correlation between changes in phospho-ATMS1981 and PD-L1 levels in TNBC post- and pre-neoadjuvant therapy. This study reveals a novel mechanism by which ATM negatively regulates PD-L1 by downregulating JNK/c-Jun/TNF-α in TNBC, shedding light on the wide application of immune checkpoint blockade therapy for treating multi-line-resistant TNBC.

Investigating Protein Binding with the Isothermal Ligand-induced Resolubilization Assay

Target engagement assays typically detect and quantify the direct physical interaction of a protein of interest and its ligand through stability changes upon ligand binding. Commonly used target engagement methods detect ligand-induced stability by subjecting samples to thermal or proteolytic stress. Here we describe a new variation to these approaches called Isothermal Ligand-induced Resolubilization Assay (ILIRA), which utilizes lyotropic solubility stress to measure ligand binding through changes in target protein solubility. We identified distinct buffer systems and salt concentrations that compromised protein solubility for four diverse proteins: dihydrofolate reductase (DHFR), nucleoside diphosphate-linked moiety X motif 5 (NUDT5), poly [ADP-ribose] polymerase 1 (PARP1), and protein arginine N-methyltransferase 1 (PRMT1). Ligand-induced solubility rescue was demonstrated for these proteins, suggesting that ILIRA can be used as an additional target engagement technique. Differences in ligand-induced protein solubility were assessed by Coomassie blue staining for SDS-PAGE and dot blot, as well as by NanoOrange, Thioflavin T, and Proteostat fluorescence, thus offering flexibility for readout and assay throughput.

Comparison of mutation landscapes of pretreatment versus recurrent squamous cell carcinoma of the oral cavity: The possible mechanism of resistance to standard treatment

BACKGROUND

A high recurrent rate of oral squamous cell carcinoma (OSCC) is a major concern in head and neck cancer treatment. The study of the genetic mutation landscape in recurrent OSCC may provide information on certain mutations associated with the pathobiology and treatment response of the OSCC.

AIM

We investigated the mutation landscape of matched pretreatment and recurrent tumors to understand the influence of genetic mutations on the pathobiology and clinical outcomes in OSCC.

METHODS AND RESULTS

We sequenced 33 formalin-fixed paraffin-embedded (FFPE) recurrent tumors, primary tumors, and primary tumors before recurrence that matched the recurrent tumors collected from Rajavithi Hospital during 2019-2021. We identified recurrent mutations from these samples by the Oncomine Ion Torrent-based next-generation sequencing on the 517 cancer-associated gene panel. From the results, we found that the most commonly mutated gene in the cohort is a histone methyltransferase KMT2D (54.55%), implicating that aberrance in epigenetic regulation may play a role in oral cancer tumorigenesis. Functional protein association network analysis of the gene frequently mutated in the recurrent tumors showed enrichment of genes that regulate the cancer cell cycle, that is, MRE11A, CDKN2A, and CYLD. This finding was confirmed in the primary-recurring matched pair. We found that recurrent tumors possess a small but recurring group of genes, with presumably the subclonal mutations driving the recurrence of the tumor, suggesting that the recurrent disease originated from a small fraction of the cancer cell that survives standard treatment. These genes were absent in the primary tumor with a good response to the standard treatment. On the other hand, we found an enrichment of DNA repair genes, namely ATR, BRCA1, BRCA2, RAD50, and MUTYH, in nonrecurrent tumors suggesting that the mutations in the DNA repair pathway may at least partially explain the different response to the standard treatment.

CONCLUSIONS

Our pilot study identified pathways of carcinogenesis in oral cancer and specific gene sets that indicate treatment responses and prognoses in this group of patients.

Long non-coding RNA TINCR suppresses growth and epithelial-mesenchymal transition by inhibiting Wnt/β-catenin signaling pathway in human pancreatic cancer PANC-1 cells: Insights from in vitro and in vivo studies

There is increasing evidence that long non-coding RNAs (lncRNAs) play a crucial role in the development and progression of malignant tumors, particularly pancreatic cancer. In this study, the influence of the lncRNA TINCR on the behavior of human pancreatic cancer cells was investigated with the aim of deciphering its role in growth, migration, and invasion. Quantitative real-time polymerase chain reaction (qRT-PCR) was used to investigate TINCR expression in pancreatic cancer cells. Ectopic expression of TINCR in PANC-1 cells was induced to evaluate the effects on cell viability and apoptosis, examining the apoptotic genes Bax and Bcl-2. Migration and invasion assays were used to measure the impact of TINCR on these cellular processes. In vivo studies using a xenograft mouse model examined the effects of TINCR on tumor growth, epithelial-to-mesenchymal transition (EMT) markers, and the Wnt/β-catenin signaling pathway. PANC-1 cells showed strikingly low TINCR expression compared to other pancreatic cancer cell lines. Ectopic TINCR expression reduced the viability of PANC-1 cells primarily by inducing apoptosis, as evidenced by increased Bax and decreased Bcl-2 expression. Overexpression of TINCR significantly increased the percentage of apoptotic cells. It also decreased the migration and invasion ability of PANC-1 cells, as demonstrated in wound healing and transwell assays. In addition, overexpression of TINCR-suppressed proteins is associated with the Wnt/β-catenin signaling pathway in PANC-1 cells. In the xenograft mouse model, overexpression of TINCR inhibited tumor growth, EMT markers, and proteins associated with the Wnt/β-catenin pathway. This study sheds light on the tumour-suppressive role of TINCR in PANC-1 cells and suggests its potential as a therapeutic target. These results shed light on the molecular mechanisms underlying the impact of TINCR on pancreatic cancer and offer promising opportunities for innovative therapeutic strategies to improve outcomes in this serious malignancy.

The Sensitization of Triple-Negative Breast Cancers to Poly ADP Ribose Polymerase Inhibition Independent of BRCA1/2 Mutation Status by Chemically Modified microRNA-489

Chemoresistance and inefficient therapeutic efficacies in triple-negative breast cancers (TNBCs) are among the major clinical problems in breast cancers. A potential new method to sensitize these tumors to current treatment options is, therefore, urgent and necessary. Our previous studies demonstrated that miR-489 serves as one of the top tumor-suppressing miRs and features downregulated expression in metastatic TNBCs and that the restoration of miR-489 expression in TNBCs effectively inhibits the metastatic potentials of TNBCs both in vitro and in vivo. The chemical modification of miR-489 (CMM489) through the replacement of uracil with 5-FU further enhances the therapeutic potential of miR-489. In the present study, we tested the effects of CMM489 in synergizing DNA damage response (DDR) inhibitors such as PARP inhibitors. CMM489 is particularly effective in sensitizing TNBC cell lines with inherent resistance to PARP inhibitors regardless of BRCA mutation status. One of the anti-cancer mechanisms through which CMM489 synergizes with PARP inhibitors is the blockade of homologous recombination (HR) in TNBC cells upon DNA damage. The results of this study highlight the potential use of CMM489 in combination treatments with PARP inhibitors in TNBCs.

Towards Improving the Efficacy of PSMA-Targeting Radionuclide Therapy for Late-Stage Prostate Cancer-Combination Strategies

PURPOSE OF REVIEW

[177Lu]Lu-PSMA-617 is a radiopharmaceutical that emits beta-minus radiation and targets prostate-specific membrane antigen (PSMA)-positive prostate cancer. Despite its clinical success, there are still patients not showing sufficient response rates. This review compiles latest studies aiming at therapy improvement in [177Lu]Lu-PSMA-617-naïve and -resistant patients by alternative or combination treatments.

RECENT FINDINGS

A variety of agents to combine with [177Lu]Lu-PSMA-617 are currently under investigation including alpha radiation-emitting pharmaceuticals, radiosensitizers, taxane chemotherapeutics, androgen receptor pathway inhibitors, immune checkpoint inhibitors, and external beam radiation. Actinium-225 (225Ac)-labeled PSMA-targeting inhibitors are the most studied pharmaceuticals for combination therapy or as an alternative for treatment after progression under [177Lu]Lu-PSMA-617 therapy. Alpha emitters seem to have a potential of achieving a response to PSMA-targeting radionuclide therapy in both initial non-responders or responders to [177Lu]Lu-PSMA-617 later developing treatment resistance. Emerging evidence for immunostimulatory effects of radiopharmaceuticals and first prospective studies support the combination of [177Lu]Lu-PSMA-617 and immune checkpoint inhibition for late-stage prostate cancer.

Discovery of novel 2,3,4,5-tetrahydrospiro[benzo[c]azepine-1,1'-cyclohexan]-5-ol derivatives as PARP-1 inhibitors

As an essential marker of cancer treatment, PARP-1 inhibitors could effectively kill tumor cells through a mechanism known as synthetic lethality and are used to treat a variety of cancers. In order to explore novel PARP-1 inhibitors, a series of 22 novel erythrina derivatives were reported and preliminarily explored their mechanism of action. The antitumor activities against four human cancer cell lines including A549, OVCAR-3, HCT-116, and MCF-7 were evaluated, and the preliminary SARs were summarized. Among them, compound 11b exhibited better anti-proliferative effects against A549 cells (IC50 = 1.95 µM). The SI results showed that compound 11b had low toxicity. Moreover, compound 11b displayed excellent PARP-1 inhibitory activities with IC50 values of 19.24 nM. In addition, molecular docking studies provided the rational binding modes of compound 11b in complexes with PARP-1. The flow cytometry assays revealed that compound 11b could induce apoptosis of A549 cells (P < 0.001). Simultaneously, compound 11b could effectively reduce the formation of PAR (P < 0.001). The ADMET prediction results indicated compound 11b had similar properties to rucaparib. Collectively, compound 11b has potential research value for further investigation.

Prognostic Impact of CD38- and IgκC-Positive Tumor-Infiltrating Plasma Cells in Triple-Negative Breast Cancer

Due to a higher mutational load, triple-negative breast cancer (TNBC) is characterized by a higher immunogenicity compared to other subtypes. In this context, we analyzed the prognostic significance of tumor-infiltrating plasma cells in a cohort of 107 triple-negative breast cancer patients. Tumor-infiltrating plasma cells were analyzed via immunohistochemistry using the plasma cell markers CD38 and IgκC. The prognostic impact of the CD38 and IgκC expression was evaluated using the Kaplan-Meier plots and Cox regression analyses. A Spearman-Rho correlation coefficient was used to evaluate a possible association between plasma cell infiltration and the BRCA mutation status. The study cohort consisted of 107 patients with early-stage TNBC, who were treated between 2009 and 2016 at the Department of Gynecology and Obstetrics, University Medical Center Mainz, Germany. The median follow-up was five years. The Kaplan-Meier survival analysis showed that higher tumor infiltration with CD38-positive plasma cells was associated with significantly longer metastasis-free survival (MFS) (p = 0.039 Log Rank). In the multivariate Cox regression analysis for metastasis-free survival, in which additional clinicopathological factors (age, tumor size, nodal status, and grading) were considered, CD38 was identified as an independent prognostic factor within the analyzed cohort (HR 0.438, 95% CI 0.195-0.983; p = 0.045). In addition to the CD38 expression, the nodal status was also identified as an independent prognostic factor in multivariate Cox regression. Regarding the IgκC expression, a higher IgκC expression was shown to be associated with a better outcome, although this effect was not statistically significant. Furthermore, we were able to show a significant correlation between plasma cell infiltration and the BRCA mutation status. A favorable prognostic significance of tumor-infiltrating plasma cells could be demonstrated in triple-negative breast cancer immunohistochemically analyzed for the CD38 and IgκC expression. CD38 was identified as an independent prognostic factor via multivariate Cox regression.

Identification and evaluation of a novel PARP1 inhibitor for the treatment of triple-negative breast cancer

Triple-negative breast cancer (TNBC) is a particularly invasive subtype of breast cancer and usually has a poor prognosis due to the lack of effective therapeutic targets. Approximately 25% of TNBC patients carry a breast cancer susceptibility gene1/2 (BRCA1/2) mutation. Clinically, PARP1 inhibitors have been approved for the treatment of patients with BRCA1/2-mutated breast cancer through the mechanism of synthetic lethality. In this study, we identified compound 6 {systematic name: 2-[2-(4-Hydroxy-phenyl)-vinyl]-3H-quinazolin-4-one} as a novel PARP1 inhibitor from established virtual screening methods. Compound 6 exerted stronger PARP1 inhibitory activity and anti-cancer activity as compared to olaparib in BRCA1-mutated TNBC cells and TNBC patient-derived organoids. Unexpectedly, we found that compound 6 also significantly inhibited cell viability, proliferation, and induced cell apoptosis in BRCA wild-type TNBC cells. To further elucidate the underlying molecular mechanism, we found that tankyrase (TNKS), a vital promoter of homologous-recombination repair, was a potential target of compound 6 by cheminformatics analysis. Compound 6 not only decreased the expression of PAR, but also down-regulated the expression of TNKS, thus resulting in significant DNA single-strand and double-strand breaks in BRCA wild-type TNBC cells. In addition, we demonstrated that compound 6 enhanced the sensitivity of BRCA1-mutated and wild-type TNBC cells to chemotherapy including paclitaxel and cisplatin. Collectively, our study identified a novel PARP1 inhibitor, providing a therapeutic candidate for the treatment of TNBC.

Role of LRRN4 in promoting malignant behavior in a p53- and Rb-defective human fallopian tube epithelial cell line

This study explored the role of leucine-rich repeat neuronal 4 (LRRN4) in ovarian carcinogenesis using the p53- and Rb-defective human fallopian tube epithelial cell line FE25. We evaluated the expression of LRRN4 in FE25 cells with and without LRRN4 knockdown by short hairpin RNA (shRNA) and studied its effects on cell proliferation, cell cycle, migration, invasion, chemotherapeutic sensitivity, apoptosis, and xenograft formation. The results showed that FE25 shRNA-LRRN4 cells exhibited more aggressive malignant behaviors than FE25 cells, including faster proliferation and increased cell distribution in the G2/M phase, Akt pathway activation, cell migration, and cell invasion, as well as decreased sensitivity to chemotherapeutic drugs. FE25 shRNA-LRRN4 cells exhibited reduced levels of apoptosis and decreased expression of cleaved caspase 3, 7, 8, and 9, indicating reduced apoptotic activity. Additionally, FE25 shRNA-LRRN4 cells showed decreased LRRN4 and CK7 expression and increased WT1 expression, suggesting a potential role for LRRN4 in ovarian carcinogenesis. FE25 shRNA-LRRN4 generated a xenograft in mice with increased levels of WT1 and TP53 expression compared to their levels in cells. Overall, this study suggests that LRRN4 may play a role in ovarian carcinogenesis by promoting aggressive malignant behavior in FE25 cells through the activation of the Akt pathway. These findings provide insights into the potential molecular mechanisms underlying ovarian cancer and may have implications for the development of new therapeutic targets for this disease.

Peripheral Neuropathy Potentially Associated to Poly (ADP-Ribose) Polymerase Inhibitors: An Analysis of the Eudravigilance Database

Poly (ADP-Ribose) polymerase inhibitors (PARPi) have emerged as a targeted therapy in cancer treatment with promising results in various types of cancer. This work aims to investigate the profile of adverse drug reactions (ADRs) associated with PARPi through the reports provided by the Eudravigilance (EV) database. We also intend to analyze the potential association of peripheral neuropathy to PARPi. Data on individual case safety reports (ICSRs) were obtained by accessing the European spontaneous reporting system via the EV website. A total of 12,762 ICSRs were collected from the EV database. Serious cases of nervous system disorders were analyzed providing strong evidence that peripheral neuropathy was reported in a higher frequency in patients treated with niraparib. Most cases reported a not recovered/not resolved outcome and involved drug withdrawal. However, several studies suggest that PARPi attenuate chemotherapy-induced painful neuropathy. Unexpected ADRs such as peripheral neuropathy may also occur, mostly in patients taking niraparib. Further pharmacovigilance studies should be conducted in this area to clarify with more precision the toxicity profile of these drugs.