The development of site-specific dual-payload antibody-drug conjugates (ADCs) represents a potential advancement in targeted cancer therapy, enabling the simultaneous delivery of two distinct drugs into the same cancer cells to overcome payload resistance and enhance therapeutic efficacy. Here, we examine various methodologies for achieving site-specific dual-payload conjugation, including the use of multi-functional linkers, canonical amino acids, non-canonical amino acids, and enzyme-mediated methods, all of which facilitate precise control over payload attachment while ensuring homogeneity. We explore the implications of different conjugation techniques on drug-to-antibody ratios and the ratios of the two payloads, as well as their impact on process complexity and manufacturability. Additionally, we address the potential advantages of dual-payload ADCs compared to ADCs combined with traditional chemotherapy or single-payload ADC/ADC combinations. By evaluating these innovative methods, we aim to provide a comprehensive understanding of the current landscape in dual-payload ADC development and outline emerging directions necessary for further advancement of this promising therapeutic strategy.

Multiple myeloma (MM) is a common yet incurable hematological malignancy characterized by bone marrow infiltration. A major clinical challenge is the resistance to chemotherapy, highlighting the urgent need to better understand the molecular mechanisms underlying chemotherapeutic resistance to available drugs. Recent studies have emphasized the role of micropeptides in solid tumors and leukemia, but their functions in MM remain unclear. In this study, we identified a novel micropeptide, altKLF4, derived from the transcription factor KLF4, which is highly expressed in newly diagnosed myeloma patient samples. We found that ectopic expression of altKLF4 interfered with chemotherapy sensitivity induced by proteasome inhibitors in myeloma cells. Additionally, confocal microscopy and transcriptome sequencing revealed that altKLF4 co-localizes with the mitochondrial inner marker TOMM20 and participates in mitochondria-related biological processes, suggesting that altKLF4 partially localizes to the mitochondria. Mitochondria may also play a role in regulating ferroptosis. Our results further demonstrated that altKLF4 inhibited drug sensitivity and ferroptosis induced by the GPX4 inhibitor RSL3 in multiple myeloma cells through a direct interaction with GPX4. In vivo experiments showed that RSL3 significantly suppressed primary myeloma growth, which could be rescued by the micropeptide altKLF4. Taken together, our study identifies altKLF4 as a novel micropeptide that serves as a potential biomarker for chemotherapeutic resistance in multiple myeloma, offering insights for diagnosis and management of drug-resistant MM.

The PARP-1/2 inhibitors have been approved for the treatment of cancers by modulating the enzymatic activity and/or the trapping ability for damaged DNA of PARP-1 and/or PARP-2, and the selective PARP-1 inhibitors are now attracting considerable attention with an aim to search for drug candidates with an improved safety. Exploring the structural basis of the selectivity and trapping capability of known PARP-1/2 inhibitors would be beneficial for the discovery of the improved inhibitors. Herein, a mutated PARP-2 catalytic domain, designated as catPARP-2SE, was engineered. It could be expressed in an elevated level and had capability to crystalize at 25 °C, which greatly facilitated obtaining PARP-2 crystals. Consequently, the complex structures of Fluzoparib, Pamiparib, Rucaparib, and Niraparib within PARP-2 were achieved. Taking advantage of these complexed structures, the detailed and quantitative analyses of protein-ligand and intra-protein interactions (αB-αF, αJ-αB, αJ-αF, ASL-αD and ASL-αF interfaces) were conducted with quantum chemistry methods (GFN2-xTB and IGMH). It suggested that the residues adjacent to Asp766 in the HD and ASL domains and the αJ-αF and ASL-αD interfaces were closely related to the selectivity and trapping mechanism. These results would provide some insights for the design and development of novel PARP-1/2 inhibitors with improved pharmacodynamic properties.

Poly (ADP-ribose) polymerase (PARP) inhibitors have revolutionized the treatment of many cancers. Metastatic castration-resistant prostate cancer (mCRPC) is an area where PARP inhibitors are intensively studied; the efficacy with PARP inhibitor monotherapy in patients with homologous recombination repair mutations following novel hormonal therapy have prompted the investigation of combination therapy, with adding an androgen receptor pathway inhibitor (ARPI) being one focus of research. Data on PARP inhibitor monotherapy and combination therapy for mCRPC are accumulating, and it is important to navigate through the complex data to inform treatment decision. Here we review the mechanisms of action of PARP inhibitors, their pharmacological properties, the synergistic activity of PARP inhibitors plus other drug classes, and the clinical evidence on monotherapy and combination therapy in patients with mCRPC. We propose key considerations in the selection of agents and treatment sequence for mCRPC, such as efficacy, toxicity profiles, biomarkers, and interactions with concomitant medications.

Gene duplication is the primary source of new genes, resulting in most genes having identifiable paralogs. Over time, paralog pairs may diverge in some respects but many retain the ability to perform the same functional role. Protein sequence identity is often used as a proxy for functional similarity and can predict shared functions between paralogs as revealed by synthetic lethal experiments. However, the advent of alternative protein representations, including embeddings from protein language models (PLMs) and predicted structures from AlphaFold, raises the possibility that alternative similarity metrics could better capture functional similarity between paralogs. Here, using two species (budding yeast and human) and two different definitions of shared functionality (shared protein-protein interactions and synthetic lethality), we evaluated a variety of alternative similarity metrics. For some tasks, predicted structural similarity or PLM similarity outperform sequence identity, but more importantly these similarity metrics are not redundant with sequence identity, i.e. combining them with sequence identity leads to improved predictions of shared functionality. By adding contextual features, representing similarity to homologous proteins within and across species, we can significantly enhance our predictions of shared paralog functionality. Overall, our results suggest that alternative similarity metrics capture complementary aspects of functional similarity beyond sequence identity alone.

Until recently, the treatment of metastatic castration-resistant prostate cancer (mCRPC) relied exclusively on hormonal therapies and taxane chemotherapy. The advent of modern molecular profiling methods applied in the clinic, namely, next-generation sequencing and advanced positron emission tomography (PET) imaging, has allowed for the development of biomarker-driven therapeutics including anti-PD-L1 therapy for microsatellite instability-high or tumor mutation burden-high disease, poly(ADP-ribose) polymerase (PARP) inhibitors for patients with DNA damage repair mutations, and lutetium 177 vipivotide tetraxetan (177Lu-PSMA-617) for patients with prostate-specific membrane antigen (PSMA) PET-avid disease. While these targeted therapies have improved outcomes, there is an opportunity to refine biomarkers to optimize patient selection, understand resistance, and develop novel combination strategies. In addition, studies in the laboratory and in patient-derived samples have shown that a subset of mCRPC tumors lose expression of common prostate cancer markers such as prostate-specific antigen and PSMA because of lineage plasticity and the development of non-androgen receptor (AR)-driven disease. Non-AR-driven prostate cancer has been associated with aggressive behavior and poor prognosis, including in some cases histologic transformation to a poorly differentiated neuroendocrine prostate cancer (NEPC). The clinical management of NEPC typically follows the treatment paradigm for small cell lung cancer and increasingly relies on genomic and phenotypic characterization of disease, including loss of tumor suppressors and expression of cell surface markers such as DLL3. Therefore, both genomic subtyping and phenotypic subtyping are important to consider and can guide the clinical management of patients with advanced prostate cancer.

Synthetic lethality represents a promising therapeutic approach in precision oncology, yet systematic identification of clinically relevant synthetic lethal interactions remains challenging. Here, we present SLAYER (Synthetic Lethality AnalYsis for Enhanced taRgeted therapy), a computational framework that integrates cancer genomic data and genome-wide CRISPR knockout screens to identify potential synthetic lethal interactions. SLAYER employs parallel analytical approaches examining both direct mutation-dependency associations and pathway-mediated relationships across 1080 cancer cell lines. Our integrative method identified 682 putative interactions, which were refined to 148 high-confidence candidates through stringent filtering for effect size, druggability, and clinical prevalence. Systematic validation against protein interaction databases revealed an ∼14-fold enrichment of known associations among SLAYER predictions compared with random gene pairs. Through pathway-level analysis, we identified inhibition of the aryl hydrocarbon receptor (AhR) as potentially synthetically lethal with RB1 mutations in bladder cancer. Experimental studies demonstrated selective sensitivity to AhR inhibition in RB1-mutant versus wild-type bladder cancer cells, which probably operates through indirect pathway-mediated mechanisms rather than direct genetic interaction. In summary, by integrating mutation profiles, gene dependencies, and pathway relationships, our approach provides a resource for investigating genetic vulnerabilities across cancer types.

PRKDC is a key factor involved in the ligation step of the non-homologous end joining pathway. Its dysfunction has proven to be a biomarker for radiosensitivity of cancer cells. However, the prognostic value of PRKDC and its underlying mechanisms have not been clarified yet. In this study, we found that PRKDC overexpressed in lung adenocarcinoma (LUAD) and is significantly related to unfavorable survival, while downregulation of PRKDC is link to inflamed tumor immune signature. Our further in vitro results also showed a potent antitumor efficacy of PRKDC inhibitors alone or combined with cisplatin in human lung cancer cells. This study demonstrated that PRKDC is a potential prognostic biomarker, immunotherapy target, and promising combination candidate for chemotherapy for lung cancer, and highlighted the potential of PRKDC-targeted inhibitors for the treatment of lung cancer.

To evaluate the treatment pattern, outcomes, safety and identify patient populations benefiting from PARP inhibitor (PARPi) rechallenge for recurrent ovarian cancer.

A multicentre, retrospective, real-world study.

Twelve hospitals in China.

Seventy patients with recurrent ovarian cancer underwent PARPi rechallenge between 1 June 2019 and 10 March 2023.

Data, including demographic, clinical characteristics and treatment-related information, were retrospectively collected from electronic health records.

The primary outcome was progression-free survival (PFS) of PARPi rechallenge (PARPi2) as maintenance therapy. We also conducted exploratory analysis to identify factors influencing PFS and characteristics associated with favourable outcomes.

Of the 70 patients, 37.1% had BRCA1/2 mutations. PARPi2 was used as a maintenance therapy in 81.4% of patients, with a median PFS of 8.6 months (95% confidence interval [CI]: 6.0-13.5). PFS did not significantly differ by BRCA status (hazard ratio = 1.25 [95% CI: 0.60-2.60], p = 0.55). Achieving complete response (CR) to the last chemotherapy was a significant predictor for receiving PARPi2 for ≥ 6 months (vs. partial response, odds ratio = 4.25 [95% CI: 1.21-14.9], p = 0.02). Patients receiving combination therapies (33.3%) had longer median PFS than those receiving monotherapy (11.0 [95% CI: 5.2-15.3] vs. 7.7 [95% CI: 5.0-13.5] months). Overall, 2.9% of patients discontinued PARPi2 due to adverse events.

PARPi rechallenge as maintenance therapy may be feasible and tolerable. Achieving CR after the last chemotherapy is associated with longer PFS and combined therapies may improve outcomes, indicating potential to overcome PARPi resistance.

Human exonuclease 1 (EXO1), a member of the structure-specific nuclease family, plays a critical role in maintaining genome stability by processing DNA double-strand breaks (DSBs), nicks, and replication intermediates during DNA replication and repair. As its exonuclease activity is essential for homologous recombination (HR) and replication fork processing, EXO1 has emerged as a compelling therapeutic target, especially in cancers marked by heightened DNA damage and replication stress. Through high-throughput screening of 45,000 compounds, we identified seven distinct chemical scaffolds that demonstrated effective and selective inhibition of EXO1. Representative compounds from two of the most potent scaffolds, C200 and F684, underwent a comprehensive docking analysis and subsequent site-directed mutagenesis studies to evaluate their binding mechanisms. Biochemical assays further validated their potent and selective inhibition of the EXO1 nuclease activity. Tumor cell profiling experiments revealed that these inhibitors exploit synthetic lethality in BRCA1-deficient cells, emphasizing their specificity and therapeutic potential for targeting genetically HR-deficient (HRD) cancers driven by deleterious mutations in HR genes like BRCA1/2. Mechanistically, EXO1 inhibition suppressed DNA end resection, stimulated the accumulation of DNA double-strand breaks, and triggered S-phase PARylation, effectively disrupting DNA repair pathways that are essential for cancer cell survival. These findings establish EXO1 inhibitors as promising candidates for the treatment of HRD cancers and lay the groundwork for the further optimization and development of these compounds as targeted therapeutics.

Olaparib-induced interstitial lung disease (OILD) is a rare but potentially serious adverse event, and its imaging characteristics and clinical course remain unclear. Ishimoto et al. previously reported three cases of OILD, but further characterisation is needed. We present three additional cases, all presenting with fever and bilateral ground-glass opacities (GGO) and fine reticulonodular opacities on computed tomography (CT). Bronchoalveolar lavage fluid (BALF) analysis showed marked lymphocytosis (>75 %). Prednisolone (0.5-1 mg/kg/day) was effective without fibrosis. BALF lymphocytosis may aid in the diagnosis of OILD. OILD should be considered in febrile patients receiving olaparib.

Cells with defective homologous recombination (HR) are highly sensitive to poly(ADP-ribose) polymerase (PARP) inhibition. Current therapeutic approaches leverage this vulnerability by using PARP inhibitors in cells with genetically compromised HR. However, if HR factors in cancer cells could be inhibited or degraded pharmacologically, it might reveal other opportunities for synergistic combinations. In this study, we developed a model system that recapitulates PARP/HR synthetic lethality by integrating a small-molecule responsive zinc-finger degron into the HR factor Partner and Localizer of BRCA2 (PALB2). We further tested a series of peptide ligands for PALB2 based on its natural binding partners, which led to the discovery of a high affinity peptide that will support future work on PALB2 and HR. Together, our findings validate PALB2 as a promising drug target and provide the tools and starting points for developing molecules with therapeutic applications.

Breast cancers with BRCA1 or BRCA2 mutations are defective in repair of DNA double-strand breaks by homologous recombination, resulting in compensatory error-prone repair that causes genomic instability. Poly(ADP-ribose) polymerase inhibitors (PARPi) are FDA-approved to treat homologous recombination-defective cancers, inducing therapy responses by synthetic lethality. PARPis increase micronuclei formation and cytosolic double-stranded DNA accumulation, activating stimulator of interferon genes (STING). Activation of STING can mediate anticancer innate immune responses by increasing T-cell infiltration into the tumor microenvironment. However, PARPi responses are not durable, and therapy resistance ensues with limited therapeutic options available for these patients. Using PARPi-sensitive and -resistant patient-derived xenografts and mouse-derived allografts, Pedretti and colleagues show in this issue of Cancer Research that the PARPi olaparib in combination with the next-generation STING agonist diABZI can overcome PARPi resistance in a manner dependent on NK cell function in the tumor microenvironment. Their study highlights a novel component of the STING-dependent innate immune response repertoire required for fighting PARPi-resistant cancer. Potent and specific next-generation STING agonists are being tested in the clinic in solid and liquid tumors, indicating a resurgence of these drugs after a long period of modest clinical activity, with a special focus on combination therapy strategies to fight therapy-resistant cancer. See related article by Pedretti et al., p. 1888.

Herein, an approach to a wide range of chiral 3-substituted δ-lactams from reductive coupling of Csp2-hybridized organohalides and 3-chloro-δ-lactams was described, and the products are versatile precursors for accessing enantioenriched 3-substituted piperidines. The utility of the reaction was highlighted by the economic synthesis of the chiral precursors of Preclamol and Niraparib. Notably, the modified chiral Bilm ligands were found to be the key factor for the reactivity and enantioselectivity.

Poly (ADP-ribose) polymerase inhibitors (PARPi) exploit DNA repair deficiency in germline BRCA1 and BRCA2 pathogenic variant (gBRCAm) cancers. Haematological toxicity limits chemotherapy-PARPi treatment combinations. In preclinical models we identified a schedule combining olaparib and carboplatin that avoids enhanced toxicity but maintains anti-tumour activity. We investigated this schedule in a neoadjuvant, phase II-III, randomised controlled trial for gBRCAm breast cancers (ClinicalTrials.gov ID:NCT03150576; PARTNER). The research arm included carboplatin (Area Under the Curve 5, 3-weekly); paclitaxel (80 mg/m2, weekly) day 1, plus olaparib (150 mg twice daily) day 3-14 (4 cycles), followed by anthracycline-containing chemotherapy (3 cycles); control arm gave chemotherapy alone. The primary endpoint, pathological complete response rate, showed no statistical difference between research 64.1% (25/39); control 69.8% (30/43) (p = 0.59). However, estimated survival outcomes at 36-months demonstrated improved event-free survival: research 96.4%, control 80.1% (p = 0.04); overall survival: research 100%, control 88.2% (p = 0.04) and breast cancer specific survival: research 100%, control 88.2% (p = 0.04). There were no statistical differences in relapse-free survival and distant disease-free survival, both were: research 96.4%, control 87.9% (p = 0.20). Similarly, local recurrence-free survival and time to second cancer were both: research 96.4%, control 87.8% (p = 0.20). The PARTNER trial identified a safe, tolerable schedule combining neoadjuvant chemotherapy with olaparib. This combination demonstrated schedule-dependent overall survival benefit in early-stage gBRCAm breast cancer. This result needs confirmation in larger trials.

Homologous recombination (HR) and mismatch repair (MMR) act as guardians of the human genome, and defects in HR or MMR are causative in at least a quarter of all malignant tumors. Although these DNA repair-deficient tumors are eligible for effective targeted therapies, fully reliable diagnostic strategies based on functional assay have yet to be established, potentially limiting safe and proper application of the molecular targeted drugs. Here we show that transient transfection of artificial DNA substrates enables ultrarapid detection of HR and MMR. This finding led us to develop a diagnostic strategy that can determine the cellular HR/MMR status within one day without the need for control cells or tissues. Notably, the accuracy of this method allowed the discovery of a pathogenic RAD51D mutation, which was missed by existing companion diagnostic tests. Our methods, termed HR eye and MMR eye, are applicable to frozen tumor tissues and roughly predict the response to therapy. Overall, the findings presented here could pave the way for accurately assessing malignant tumors with functional defects in HR or MMR, a step forward in accelerating precision medicine.

The burden of dengue on human health has dramatically increased in recent years, underscoring the urgent need for effective therapeutic interventions. Despite decades of research since the discovery of the dengue virus, no specific antiviral treatments are available and strategies to reliably prevent severe disease remain limited. Direct-acting antivirals against dengue are under active investigation but have shown limited efficacy to date. An underappreciated Achille's heal of the virus is its dependence on host factors for infection and pathogenesis, each of which presents a potential avenue for therapeutic intervention. We and others have demonstrated that dengue virus relies on multiple host kinases, some of which are already targeted by clinically approved inhibitors. These offer drug repurposing opportunities for host-directed dengue treatment. Here, we summarize findings on the role of kinases in dengue infection and disease and highlight potential kinase targets for the development of innovative host-directed therapeutics.

Inhibitors of poly(ADP-ribose) polymerases (PARPs) have revolutionized the treatment of cancers with DNA repair deficiencies. Here we describe the structure-based discovery and synthesis of 6-6-5-5-6-fused pentacyclic scaffolds 5 and cis-(±)-6 as a novel class of PARP1 inhibitors. Chiral supercritical fluid chromatographic separation of cis-(±)-6 afforded inactive ent-6_P1 and active ent-6_P2. Compound 5 (P-gp ER = 0.9) and ent-6_P2 (P-gp ER = 1.1) demonstrated good Caco-2 permeability and are not actively effluxed by ABC transporters. In vitro analysis in HEK293T cells found that 5, cis-(±)-6, and ent-6_P2 showed near complete inhibition of PARP1 activity at 10 μM. Furthermore, compounds 5, cis-(±)-6, and ent-6_P2 displayed selective cytotoxic activity in BRCA mutant cancer cells but not isogenic BRCA-proficient cells. Taken together, 5 and ent-6_P2 define a novel class of lead PARP inhibitors for further development.

Poly(ADP-ribose) polymerase inhibitors (PARPis) are a class of agents targeting DNA damage repair that have become standard therapy for epithelial ovarian cancer (EOC) and multiple other solid tumors. In addition to targeting DNA damage repair, PARPis actively modulate antitumor immune responses, with efficacy being partially dependent on T cell activity. Here, we found that patient T cells sustain DNA damage during PARPi treatment, which reduces treatment efficacy. Leveraging paired pre- and posttreatment tumor samples from a clinical trial of patients with EOC treated with neoadjuvant niraparib as monotherapy, we showed that the PARPi caused DNA damage, slowed proliferation, and increased apoptosis in T cells, which we validated both in vitro and in mouse models. A genome-wide CRISPR (clustered regularly interspaced short palindromic repeats) knockout screen in primary human T cells identified PARP1 as the principal mediator of PARPi-induced T cell death. T cell-specific deletion of PARP1 or mutating Parp1 at its binding sites in transgenic mice led to reduced T cell DNA damage during PARPi treatment, resulting in improved efficacy of PARPis, alone or in combination with immune checkpoint inhibition. We then engineered PARPi-tolerant CAR T cells using cytosine base editing, which decreased PARPi-induced PARP1 trapping and led to reduced PARPi-induced DNA damage, resulting in superior antitumor efficacy in xenograft models compared with parental CAR T cells. This study highlights the relevance of PARPi-induced DNA damage to T cells and suggests opportunities to improve the efficacy of PARPis as monotherapy or in combination with immunotherapy.

ATPase family AAA domain-containing protein 2, or ATAD2, is a novel carcinogen, essential for cancer development, chromatin remodeling, and transcriptional control. It contains a bromodomain, which binds to acetylated histones to control gene expression. It also impacts pathways that regulate the cell cycle, DNA replication, and hormone signalling. ATAD2 is overexpressed in several malignancies, including colorectal, lung, ovarian, and breast cancers, and cancer metastasis. Investigations into the function of ATAD2 in oncogenesis and its interactions may offer fresh approaches to creating cancer treatment plans. Although preclinical research is very encouraging, many unresolved aspects regarding therapeutic development remain, including toxicity being explored concurrently. Investigations into the function of ATAD2 in oncogenesis may offer fresh approaches to developing chemotherapy strategies. Most of ATAD2's molecular mechanisms behind carcinogenesis and functions are discussed here. Additionally, we included progress, including potential monoclonal antibodies, RNA-based therapies, and small chemical inhibitors, in the review. Therefore, we guarantee this study will provide researchers with new opportunities and directions for cancer therapeutics.

Inhibition of the deubiquitinating enzyme USP1 can induce synthetic lethality in tumors characterized by homologous recombination deficiency (HRD) and represents a novel therapeutic strategy for the treatment of BRCA1/2-mutant cancers, potentially including patients whose tumors have primary or acquired resistance to PARP inhibitors (PARPi). In this study, we present a comprehensive characterization of TNG348, an allosteric, selective, and reversible inhibitor of USP1. TNG348 induces dose-dependent accumulation of ubiquitinated protein substrates both in vitro and in vivo. CRISPR screens show that TNG348 exerts its antitumor effect by disrupting the translesion synthesis pathway of DNA damage tolerance through RAD18-dependent ubiquitinated PCNA. Although TNG348 and PARPi share the ability to selectively kill HRD tumor cells, CRISPR screens reveal that TNG348 and PARPi do so through discrete mechanisms. Particularly, knocking out PARP1 causes resistance to PARPi but sensitizes cells to TNG348 treatment. Consistent with these findings, combination of TNG348 with PARPi leads to synergistic antitumor effects in HRD tumors, resulting in tumor growth inhibition and regression in multiple mouse xenograft tumor models. Importantly, our data on human cancer models further show that the addition of TNG348 to PARPi treatment can overcome acquired PARPi resistance in vivo. Although the clinical development of TNG348 has been discontinued because of unexpected liver toxicity in patients (NCT06065059), the present data provide preclinical and mechanistic support for the continued exploration of USP1 as a drug target for the treatment of patients with BRCA1/2-mutant or HRD cancers.

Poly (ADP-ribose) polymerase inhibitors (PARPi) have revolutionized the treatment landscape for patients suffering from BRCA1-mutated breast and ovarian cancers. However, responses are not durable. We demonstrate that treatment with PARPi, niraparib, increases programmed death-ligand 1 (PD-L1) expression in BRCA1-deficient cancer cells, contributing to immune evasion. To circumvent this, we developed P-selectin-targeted poly (lactic-co-glycolic) acid (PLGA)-poly (ethylene glycol) (PEG)-based nanoparticles (NPs) encapsulating PARP and PD-L1 inhibitors at a synergistic ratio. To further enhance tumor targeting, we leveraged radiation-induced P-selectin upregulation in BRCA1-deficient cancer cells and their associated angiogenic endothelial cells, improving NP accumulation in the primary tumors and hard-to-target metastatic sites, including brain metastasis. Using a combination of traditional 2-dimensional (2D) cell cultures, advanced 3-dimensional (3D) spheroids, tumor-on-a-chip platforms, and in vivo models, we demonstrate the enhanced accumulation and efficacy of the radiation-guided P-selectin-targeted NPs in primary and brain-metastatic BRCA1-deficient tumors.

Poly (ADP-ribose) polymerase (PARP) inhibitors have improved the prognosis of homologous recombination deficient (HRD) ovarian cancer (OC), while effective therapeutic strategies for HR-proficient (HRP) OC still need to be established. This study investigates senescence-mediated inflammation as a novel mechanism of action for PARP inhibitors in HRP cancers. Transcriptome analyses were performed in olaparib-treated HeLa cells as a HRP model. Interferon regulatory factor-Lucia luciferase (IRF-Luc) reporter activity was assessed. The effects of PARP inhibitors on senescence-like phenotypes were assessed in seven HRP cancer cell lines, based on morphological changes, senescence-associated β-galactosidase (SA-β-GAL) activity, cellular granularity, and senescence-associated secretory phenotype (SASP)-related gene expression. Peripheral blood mononuclear cell (PBMC) migration assays were also performed with the conditioned medium in treatment with the PARP inhibitor. Transcriptome analyses revealed numbers of inflammatory cytokine- and chemokine-related pathways were significantly upregulated in olaparib-treated HeLa cells, which were confirmed by IRF-Luc reporter assays. The PARP inhibitors induced senescent phenotypes in HRP cancer cell lines: flattened and enlarged morphology, increased SA-β-GAL activity, elevated cellular granularity, and upregulated expressions of SASP-related genes (e.g., IL1B, IL6, and CXCL10). Furthermore, in vitro migration assays revealed that PARP inhibitor-treated HRP cancer cells attracted PBMCs more abundantly, suggesting the potential for recruiting immune cells to HRP cancer cells through senescence-mediated immunological activation. Our findings suggest that PARP inhibitors recruit immune cells to HRP cancer cells, potentially activating immune responses in the tumor microenvironment, providing new insights into the clinical benefits of PARP inhibitors in immunotherapy for patients with HRP OC.

Resistance to poly-(ADP)-ribose polymerase inhibitors (PARPi) remains a significant challenge in clinical practice, leading to treatment failure in many patients. It is crucial to better understand the molecular mechanisms that underlie PARPi resistance. In this study, utilizing a genome-wide CRISPR activation screen with olaparib, we identified ARL11 as a potential modulator of PARPi treatment response in BRCA-wild-type MDA-MB-231 cells. Mechanistically, ARL11 interacts with STING to enhance innate immunity and forms positive feedback with type I interferon (IFN) induction, which induces ARL11 up-regulation and contributes to resistance to PARPi therapy. Additionally, we observed that ARL11 interacts with the RUVBL1 and RUVBL2 (RUVBL1/2) complex, the key DNA double-strand repair proteins, facilitating DNA homologous recombination (HR) repair and significantly reducing PARPi-induced DNA double-strand damages. Clinical sample analysis reveals that the expression levels of ARL11 and RUVBL1/2 are significantly elevated in breast cancer patients compared to healthy controls. Collectively, our findings suggested that ARL11 and RUVBL1/2 may be promising therapeutic targets to sensitize breast cancer cells to PARPi therapy.

Colorectal cancer (CRC) is one of the leading causes of cancer-related deaths in the United States. A key driver of CRC development is microsatellite instability (MSI), which is caused by DNA mismatch repair deficiency and characterized by hypermutability of short-tandem repeat sequences. A significant portion of MSI CRCs do not respond to checkpoint immunotherapy treatments, highlighting an unmet need for improved therapies. Recent studies have revealed that MSI cancer cells require Werner (WRN), a RecQ family DNA helicase, for survival. Inhibiting WRN has emerged as a promising approach for targeting MSI CRCs that are insensitive to standard therapies. Several highly potent small-molecule WRN inhibitors have been developed and exhibited striking in vitro and in vivo activities against MSI cancers. Two of these WRN inhibitors, HRO761 and VVD-133214, have recently entered clinical trials. In this review, we summarize recent studies on WRN as a synthetic lethal target in MSI CRC and the development of WRN inhibitors as a new class of anticancer agents.

DNA damage occurs from both endogenous and exogenous sources and DNA damaging agents are a mainstay in cancer therapeutics. DNA damage sensors (DDS) are proteins that recognize and bind to unique DNA structures that arise from direct DNA damage or replication stress and are the first step in the DNA damage response (DDR). DNA damage sensors are responsible for recruiting transducer proteins that signal downstream DNA repair pathways. As the initiating proteins, DDS are excellent candidates for anti-cancer drug targeting to limit DDR activation. Here, we review four major DDS: PARP1, RPA, Ku, and the MRN complex. We briefly describe the cellular DDS functions before analyzing the structural mechanisms of DNA damage sensing. Lastly, we examine the current state of the field towards inhibiting each DDS for anti-cancer therapeutics and broadly discuss the therapeutic potential for DDS targeting.

Neoadjuvant treatment of bladder cancer is evolving, with immunotherapy demonstrating promising activity. PARP inhibition combined with immune activation has been proposed as a synergistic strategy. We conducted a comprehensive molecular characterization of tumors treated with this combination in the neoadjuvant setting to provide crucial results for rational development.

A phase II clinical trial was designed to evaluate the combination of anti-PDL1 inhibitor durvalumab and PARP inhibitor olaparib, focusing on biomarker dynamics in both pre- and post-treatment settings. A total of 29 patients were enrolled. Genomic and transcriptomic profiling, as well as analyses of immune cell populations, was conducted at baseline and at the time of cystectomy.

Of the 29 patients treated, a pathologic complete response was observed in 13 cases (44.8%). No major safety concerns were associated with the treatment, and 26 patients (90%) underwent cystectomy. Mutational patterns, tumor mutation burden, and homologous recombination deficiency remained stable throughout treatment and were not predictive of outcomes. However, a shift toward stromal phenotypes and increased expression of epithelial-mesenchymal transition signatures were observed following therapy, particularly in resistant tumors. Moreover, an increase in circulating CD4+ CD27- CD28- T cells was noted among responders.

The combination of neoadjuvant durvalumab and olaparib shows therapeutic activity in bladder cancer. Resistance mechanisms seem to be driven by transcriptional adaptations rather than the emergence of new mutations.

Poly (ADP-ribose) polymerases (PARPs) are enzymes essential for detecting and repairing DNA damage through poly-ADP-ribosylation. In cancer, cells with deficiencies in homologous recombination repair mechanisms often become more dependent on PARP-mediated repair mechanisms to effectively repair dsDNA breaks. As such, PARP inhibitors (PARPis) were introduced into clinical practice, serving as a key targeted therapy option through synthetic lethality in the treatment of cancers with homologous recombination repair deficiency (HRD). Though PARPis are currently approved in the adjuvant setting for several cancer types such as ovarian, breast, prostate and pancreatic cancer, their potential role in the neoadjuvant setting remains under investigation. This review outlines the rationale for using PARPi in the neoadjuvant setting and evaluates findings from early and ongoing clinical trials.

Our analysis indicates that numerous studies have explored PARPi as a neoadjuvant treatment for HRD-related cancers. The majority of neoadjuvant PARPi trials have been performed in breast and ovarian cancer, while phase II/III evidence supporting efficacy in prostate and pancreatic cancers remains limited. Studies are investigating PARPi in the neoadjuvant setting of HRD-related cancers. Future research should prioritize combination strategies with immune checkpoint inhibitors and expand outcome measures to include patient satisfaction and quality-of-life metrics.

Synthetic lethality in homologous recombination (HR)-deficient cancers caused by Poly (ADP-ribose) polymerase inhibitors (PARPi) has been classically attributed to its role in DNA repair. The mode of action of PARPi and resistance thereof are now believed to be predominantly replication associated. Therefore, effective combinatorial approaches of targeting replication fork processing along with HR-downregulation to target HR-proficient and possibly PARPi-resistant tumors are warranted. Stilbenes are a privileged class of molecules, which include resveratrol, pterostilbene, piceatannol, etc, that modulate both replication processes and RAD51-expression. In this investigation, by screening a small library of stilbenes, including in-house synthesized molecules, trans-4,4'-dihydroxystilbene (DHS) was discovered as a potent natural agent, which downregulates RAD51 expression and HR repair (GFP-reporter assay). DHS induces extensive synergistic cell death in ovarian cancers when combined with talazoparib (PARPi). Mechanistically, DHS elicits replication-stress through severely impeding replication fork progress, speed, and inducing fork-asymmetry. This leads to robust induction of single stranded DNA (ssDNA) gaps and poly-ADP-ribosylation (PARylation) in S-phase cells, signifying issues related to lagging (Okazaki) strand synthesis. PARPi, which abrogates PARylation, potentiates DHS induced ssDNA gaps, and their conversion into lethal double strand breaks through MRE11 action. Furthermore, the combination is highly effective in mitigating ovarian tumor xenograft growth in SCID mice and exhibited a good therapeutic-index with no/minimal tissue-toxicity.

The joining of DNA single- and double-strand breaks (SSB and DSB) is essential for maintaining genome stability and integrity. While this is ultimately accomplished in human cells by the DNA ligases encoded by the LIG1, LIG3 and LIG4 genes, these enzymes are recruited to DNA breaks through specific interactions with proteins involved in break sensing and recognition and/or break processing. In this review, we focus on the interplay between the DNA break-activated poly (ADP-ribose) polymerases, PARP1 and PARP2, poly (ADP-ribose) (PAR) and the DNA ligases in DNA replication and repair. The most extensively studied example of this interplay is the recruitment of DNA ligase IIIα (LigIIIα) and other repair proteins to SSBs through an interaction between XRCC1, a scaffold protein and partner protein of nuclear LigIIIα, and PAR synthesized by PARP1 and to a lesser extent PARP2. Recently, these proteins have been implicated in a back-up pathway for joining Okazaki fragments that appears to have a critical function even in cells with no defect in the major LigI-dependent pathway. Finally, we discuss the effects of FDA-approved PARP1/2 inhibitors on DNA replication and repair in cancer and non-malignant cells and the potential utility of DNA ligase inhibitors as cancer therapeutics.

Cells deficient in DNA repair factors breast cancer susceptibility 1/2 (BRCA1/2) or ataxia-telangiectasia mutated (ATM) are sensitive to poly-ADP ribose polymerase (PARP) inhibitors. Building on our previous findings, we asked how the lysine methyltransferase SETD1A contributed to PARP inhibitor-mediated cell death in these contexts and determined the mechanisms responsible.

We used cervical, breast, lung and ovarian cancer cells bearing mutations in BRCA1 or ATM and depleted SETD1A using siRNA or CRISPR/Cas9. We assessed the effects of the PARPi Olaparib on cell viability, homologous recombination, and DNA repair. We assessed underlying transcriptional perturbations using RNAseq. We used The Cancer Genomics Atlas (TCGA) and DepMap to investigate patient survival and cancer cell characteristics.

Loss of SETD1A from both BRCA1-deficient and ATM-deficient cancer cells was associated with resistance to Olaparib, explained by partial restoration of homologous recombination. Mechanistically, SETD1A-dependent transcription of the crossover junction endonuclease EME1 correlated with sensitivity to Olaparib in these cells. Accordingly, when SETD1A or EME1 was lost, BRCA1 or ATM-mutated cells became resistant to Olaparib, and homologous recombination was partially restored.

Loss of SETD1A or EME1 drives cellular resistance to Olaparib in certain genetic contexts and may help explain why patients develop resistance to PARP inhibitors in the clinic.

Current treatments for advanced prostate cancer (PCa) primarily target the androgen receptor (AR) pathway. However, the emergence of castration-resistant prostate cancer (CRPC) and resistance to AR pathway inhibitors (APPIs) remains ongoing challenges. Here, we present BSJ-5-63, a proteolysis-targeting chimera (PROTAC) targeting cyclin-dependent kinases (CDKs) CDK12, CDK7, and CDK9, offering a multipronged approach to CRPC therapy. BSJ-5-63 degrades CDK12, diminishing BRCA1 and BRCA2 expression and inducing a sustained "BRCAness" state. This sensitizes cancer cells to PARP inhibitors (PARPis) regardless of their homologous recombination repair (HRR) status. Furthermore, CDK7 and CDK9 degradation attenuates AR signaling, enhancing its therapeutic efficacy. Preclinical studies, including both in vitro and in vivo CRPC models, demonstrate that BSJ-5-63 exerts potent antitumor activity in both AR-positive and AR-negative setting. This study introduces BSJ-5-63 as a promising therapeutic agent that addresses both DNA repair and AR signaling mechanisms, with potential benefits for a board patient population.

Although macrophages and lipid metabolism significantly influence the progression of various cancers, their precise roles in pancreatic cancer (PC) remain unclear. This study focuses on identifying and validating biomarkers associated with macrophage-related genes (MRGs) and lipid metabolism-related genes (LMRGs), providing new targets and strategies for therapeutic intervention. This research utilized datasets from TCGA-PAAD, GSE62452, and GSE57495. Candidate genes were identified by overlapping differentially expressed genes with MRGs from WGCNA and LMRGs. Regression analyses were performed to pinpoint potential biomarkers and construct a risk model, which underwent evaluation. A nomogram was subsequently developed and validated. Additional analyses, including functional enrichment, somatic mutation profiling, immune landscape assessment, and RT-qPCR, were performed to investigate the underlying biological mechanisms in PC. The study identified ADH1A, ACACB, CD36, CERS4, PDE3B, ALOX5, and CRAT as biomarkers for PC. RT-qPCR results revealed reduced expression of ADH1A, ACACB, CD36, CERS4, PDE3B, and CRAT in tumor samples compared to adjacent tissues, whereas ALOX5 expression was significantly elevated in tumor samples. A risk model utilizing these biomarkers classified PC patients into high- and low-risk cohorts, with high-risk patients showing lower survival probabilities. Subsequently, risk score and N stage were identified as independent prognostic factors, leading to the development of a nomogram. Notably, both risk cohorts showed significant enrichment in the "cell cycle" pathway. Furthermore, TP53 mutations were prevalent in both high-risk (76%) and low-risk (50%) cohorts. Correlation analysis indicated that PVRL2 (an immunosuppressive factor), CD276 (an immunoactivator), and CCL20 (a chemotactic factor) had the highest positive correlation with the risk score. In this study, ADH1A, ACACB, CD36, CERS4, PDE3B, ALOX5, and CRAT were identified as biomarkers for PC, with their expression levels validated in clinical samples. These findings offered a potential theoretical foundation for developing targeted treatments for PC.

Pathogenic variants (PVs) in ATM, BRCA1, BRCA2, CHEK2, and PALB2 are associated with increased breast cancer risk. However, it is unknown whether this risk differs by PV type or location in carriers ascertained from the general population.

To evaluate breast cancer risks associated with PV type and location in ATM, BRCA1, BRCA2, CHEK2, and PALB2, we performed age adjusted case-control association analysis in 32,247 women with and 32,544 age-matched women without breast cancer from the CARRIERS Consortium. PVs were grouped by type and location within genes and assessed for risks of breast cancer (odds ratios (OR), 95% confidence intervals (CI), and P-values) using logistic regression.

Compared to women carrying BRCA2 exon 11 protein truncating variants (PTVs) in the CARRIERS population-based study, women with BRCA2 ex1-10 PTVs (OR=13.5, 95%CI 6.0-38.7, P<0.001) and ex13-27 PTVs (OR=9.0, 95%CI 4.9-18.5, P<0.001) had higher breast cancer risks, lower rates of ER-negative breast cancer (ex13-27 OR=0.5, 95%CI 0.2-0.9, P=0.035; ex1-10 OR=0.5, 95%CI 0.1-1.0, P=0.065), and earlier age at breast cancer diagnosis (ex13-27 5.5 years, P<0.001; ex1-10 2.4 years, P=0.169). These associations with ER-negative breast cancer and age replicated in a high-risk clinical cohort from Ambry Genetics and the population-based UK Biobank cohort. No differences in risk by gene region were observed for PTVs in other predisposition genes.

Population-based and clinical high-risk cohorts establish that PTVs in exon 11 of BRCA2 are associated with reduced breast cancer risk, later age at diagnosis, and greater risk of ER-negative disease. These differential risks may improve individualized risk prediction and clinical management for women carrying BRCA2 PTVs.