PARPi Triggers the STING-Dependent Immune Response and Enhances the Therapeutic Efficacy of Immune Checkpoint Blockade Independent of BRCAness

Dual-responsive nanoscale ultrasound contrast agent as an oxidative stress amplifier for enhanced DNA damage in BRCA-proficient ovarian cancer

PARP inhibitor (PARPi)-based synthetic lethal therapies have displayed limited benefits in BRCA-proficient ovarian cancer. To potentiate the application of PARPi, an ultrasound contrast agent OLA-NDs for delivery of the PARPi olaparib (OLA) was established for enhancing DNA damage by blocking DNA repair. OLA-NDs were endowed with endogenous pH- and exogenous ultrasound (US)-responsiveness to target tumors, as well as contrast-enhanced US imaging for diagnostic and therapeutic integration. OLA-NDs could upregulate NOX4 to induce oxidative stress and sensitize BRCA wild-type A2780 cells to DNA oxidative damage through the utilization of ultrasound-targeted microbubble destruction (UTMD). In addition, the strategy further increased ROS production by interfering with mitochondrial function, thereby exacerbating DNA double-strand breaks (DSBs) and inducing mitochondria-mediated apoptosis. As a consequence, the combined application of UTMD and OLA-NDs demonstrated significant antitumor effects in vitro and in vivo. This combined strategy of amplifying oxidative damage improved lethality by promoting DNA DSBs and apoptosis with reduced adverse side effects, which would provide new insight for the clinical application of PARPi in BRCA-proficient ovarian cancer.

Deciphering cGAS-STING signaling: implications for tumor immunity and hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is the most prevalent form of primary liver cancer and poses a significant global health challenge due to its rising incidence and associated mortality. Recent advancements in understanding the cytosolic DNA sensing, the cyclic GMP-AMP synthase-stimulator of interferon genes (cGAS-STING) pathway have illuminated its critical role in the immune response to HCC. This narrative review deciphers the multifaceted involvement of cGAS-STING in HCC, mainly its function in detecting cytosolic DNA and initiating type I interferon (IFN-I) responses, which are pivotal for antitumor immunity. This immune response is crucial for combating pathogens and can play a role in tumor surveillance. In the context of HCC, the tumor microenvironment (TME) can exhibit immune resistance, which complicates the effectiveness of therapies like immune checkpoint blockade. However, activation of the cGAS-STING pathway has been shown to stimulate antitumor immune responses, enhancing the activity of dendritic cells and cytotoxic T lymphocytes. There is ongoing research into STING agonists as a treatment strategy for HCC, with some studies indicating promising results in prolonging survival and enhancing the immune response against tumors. By summarizing current knowledge and identifying research gaps, this review aims to provide a comprehensive overview of cGAS-STING signaling in HCC and its future directions, emphasizing its potential as a therapeutic target in the fight against HCC. Understanding these mechanisms could pave the way for innovative immunotherapeutic approaches that enhance the efficacy of existing treatments and improve patient prognosis.

Mitigating T cell DNA damage during PARP inhibitor treatment enhances antitumor efficacy

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.

Reciprocal Modulation of Tumour and Immune Cell Motility: Uncovering Dynamic Interplays and Therapeutic Approaches

Dysregulated cell movement is a hallmark of cancer progression and metastasis, the leading cause of cancer-related mortality. The metastatic cascade involves tumour cell migration, invasion, intravasation, dissemination, and colonisation of distant organs. These processes are influenced by reciprocal interactions between cancer cells and the tumour microenvironment (TME), including immune cells, stromal components, and extracellular matrix proteins. The epithelial-mesenchymal transition (EMT) plays a crucial role in providing cancer cells with invasive and stem-like properties, promoting dissemination and resistance to apoptosis. Conversely, the mesenchymal-epithelial transition (MET) facilitates metastatic colonisation and tumour re-initiation. Immune cells within the TME contribute to either anti-tumour response or immune evasion. These cells secrete cytokines, chemokines, and growth factors that shape the immune landscape and influence responses to immunotherapy. Notably, immune checkpoint blockade (ICB) has transformed cancer treatment, yet its efficacy is often dictated by the immune composition of the tumour site. Elucidating the molecular cross-talk between immune and cancer cells, identifying predictive biomarkers for ICB response, and developing strategies to convert cold tumours into immune-active environments is critical to overcoming resistance to immunotherapy and improving patient survival.

Inflammation and tumor immune escape in response to DNA damage

Senescent and cancer cells share common inflammatory characteristics, including factors of the senescence-associated secretory phenotype (SASP) and the cyclic GMP-AMP synthase (cGAS)-stimulator of interferon genes (STING) pathway. Inflammation in the tumor microenvironment not only provides an opportunity for immune cells to attack cancer cells, but also promotes cancer invasion and metastasis. Immune checkpoint molecule PD-L1 is transcriptionally induced by inflammation, and the immunological state of PD-L1-positive tumors influences the efficacy of Immune checkpoint inhibitors (ICIs). ICIs are effective against the PD-L1-positive "hot" tumors; however, the non-immunoactive "cold" tumors that express PD-L1 rarely respond to ICIs, suggesting that converting PD-L1-positive "cold" tumors into "hot" tumors would improve the efficacy of ICIs. To eliminate cancer via the innate immune system, a therapeutic strategy for manipulating inflammatory responses must be established. To date, the molecular mechanisms of inflammation-induced tumorigenesis are not yet fully understood. However, it is becoming clear that the regulatory mechanisms of inflammation in cancer via the cGAS-STING pathway play an important role in both cancer and sensescent cells. In this review, we focus on inflammation and immune escape triggered by DNA damage in cancer and senescent cells.

Selective BCL-2 inhibitor triggers STING-dependent antitumor immunity via inducing mtDNA release

BACKGROUND

The stimulator of interferon genes (STING) signaling pathway has been demonstrated to propagate the cancer-immunity cycle and remodel the tumor microenvironment and has emerged as an appealing target for cancer immunotherapy. Interest in STING agonist development has increased, and the candidates hold significant promise; however, most are still in the early stages of human clinical trials. We found that ABT-199 activated the STING pathway to enhance the immunotherapeutic effect, and provided a ready-to-use small molecule drug for STING signaling activation.

METHODS

Phosphorylation of STING, TBK1, and IRF3, as well as activation of the interferon-I (IFN-I) signaling pathway, were detected following ABT-199 treatment in various colorectal cancer cells. C57BL/6J and BALB/c mice with subcutaneous tumors were employed to evaluate the in vivo therapeutic effects of the ABT-199 and anti-PD-L1 combination. Flow cytometry and ELISA were employed to analyze the level and activity of tumor-infiltrating T lymphocytes. Immunofluorescence and quantitative real-time PCR were conducted to assess the source and accumulation of double stranded DNA (dsDNA) in the cytoplasm. Chemical cross-linking assay, co-immunoprecipitation, and CRISPR/Cas9-mediated knockout were performed to investigate the molecular mechanism underlying ABT-199-induced voltage-dependent anion channel protein 1 (VDAC1) oligomerization and mitochondrial DNA (mtDNA) release.

RESULTS

ABT-199 significantly activated the STING signaling pathway in various colorectal cancer cells, which was evidenced by increased phosphorylation of TBK1 and IRF3, and upregulation of C-C motif chemokine ligand 5 (CCL5), C-X-C motif chemokine ligand 10 (CXCL10), and interferon beta transcription. By promoting chemokine expression and cytotoxic T-cell infiltration, ABT-199 promoted antitumor immunity and synergized with anti-PD-L1 therapy to improve antitumor efficacy. ABT-199 induced mtDNA accumulation in the cytoplasm and triggered STING signaling via the canonical pathway. cGAS or STING-KO models significantly abolished both STING signaling activation and the antitumor efficacy of ABT-199. Mechanically, ABT-199 promoted VDAC1 oligomerization by disturbing the binding between BCL-2 and VDAC1, thereby facilitating mtDNA release into the cytoplasm. ABT-199-triggered STING signaling was attenuated when VADC1 was knocked out. Consistently, the antitumor effect of ABT-199 in vivo was abolished in the absence of VDAC1.

CONCLUSIONS

Our results identify a ready-to-use small molecule compound for STING activation, reveal the underlying molecular mechanism through which ABT-199 activates the STING signaling pathway, and provide a theoretical basis for the use of ABT-199 in cancer immunotherapy.

PARP inhibition elicits NK cell-associated immune evasion via potentiating HLA-G expression in tumor

Resistance to poly(ADP-ribose) polymerase inhibitors (PARPi) poses a significant challenge to enhancing the efficacy of cancer treatments. Beyond the cellular mechanisms intrinsic to tumor cells, the modulation of the tumor immune microenvironment is crucial in dictating the responsiveness to pharmacological interventions. Thus, there is a pressing need to elucidate the intricate interplay between PARPi and antitumor immune responses and to develop an optimized combinatorial therapeutic approach. In this study, using matched tumor samples before and after neoadjuvant monotherapy with the PARPi niraparib in a prospective clinical trial (NCT04507841), we observed a significant increase in natural killer (NK) cell infiltration post-treatment. However, this was not accompanied by the expected enhancement in their cytotoxic functions. This observation underscores the necessity to optimize the antitumor potential of NK cells by enhancing their cytotoxic capabilities. Upon exposure to niraparib, tumor cells, particularly those with wild-type EGFR, exhibited a pronounced upregulation of human leukocyte antigen G (HLA-G), an immune checkpoint impeding NK cell functions. Niraparib promotes EGFR internalization, which in turn diminishes AKT/mTOR signaling, leading to the increased transcriptional activity of the transcription factor EB (TFEB) and subsequent enhancement of HLA-G expression. The combination of niraparib with HLA-G blockade not only augmented NK cell-mediated tumor lysis in vitro but also synergistically inhibited tumor growth in humanized patient-derived xenograft models. Collectively, our results shed light on a previously unrecognized immune evasion mechanism and offer a compelling argument for the integration of HLA-G blockade with PARPi in cancer therapy.

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.

Deciphering the mechanisms of PARP inhibitor resistance in prostate cancer: Implications for precision medicine

Prostate cancer is a leading malignancy among men. While early-stage prostate cancer can be effectively managed, metastatic prostate cancer remains incurable, with a median survival of 3-5 years. The primary treatment for advanced prostate cancer is androgen deprivation therapy (ADT), but resistance to ADT often leads to castrationresistant prostate cancer (CRPC), presenting a significant therapeutic challenge. The advent of precision medicine has introduced promising new treatments, including PARP inhibitors (PARPi), which target defects in DNA repair mechanisms in cancer cells. PARPi have shown efficacy in treating advanced prostate cancer, especially in patients with metastatic CRPC (mCRPC) harboring homologous recombination (HR)-associated gene mutations. Despite these advancements, resistance to PARPi remains a critical issue. Here, we explored the primary mechanisms of PARPi resistance in prostate cancer. Key resistance mechanisms include homologous recombination recovery through reverse mutations in BRCA genes, BRCA promoter demethylation, and non-degradation of mutated BRCA proteins. The tumor microenvironment and overactivation of the base excision repair pathway also play significant roles in bypassing PARPi-induced synthetic lethality. In addition, we explored the clinical implications and therapeutic strategies to overcome resistance,emphasizing the need for precision medicine approaches. Our findings highlight the need for comprehensive strategies to improve PARPi sensitivity and effectiveness,ultimately aiming to extend patient survival and improve the quality of life for those with advanced prostate cancer. As our understanding of PARPi resistance evolves, more diverse and effective individualized treatment regimens will emerge.

Acid-Responsive Biocompatible Hydrogel Modulating Tumor DNA Self-Repair Collaborated with Chemotherapy for Boosting STING Pathway-Associated Immunotherapy

In this study, an acid-responsive hydrogel (ODCM@AZD) encapsulating doxorubicin (DOX), Mn2+, and AZD2281 is rationally engineered for synergistic chemo-immunotherapy. Notably, ODCM@AZD can be specifically degraded within the tumor microenvironment to release the loaded therapeutic agents. Specifically, the released DOX kills tumor cells to produce abundant cytoplasmic DNA, while the freed AZD2281 inhibits the DNA repair pathway of tumor cells to enhance the chemotherapeutic effect and promote the accumulation of damaged DNA, which is further aggravated by reactive oxygen species (ROS) generated from the Mn2+-mediated Fenton-like reaction. Not only that, Mn2+ simultaneously increases the sensitivity of cGAS to cytoplasmic DNA to stimulate the cGAS-STING pathway and synergizes with DOX-mediated immunogenic cell death (ICD) to initiate powerful antitumor immune responses. More importantly, the combination of ODCM@AZD with immune checkpoint blockade (ICB) significantly improves systemic tumoricidal immunity and potentiates therapeutic effects on distant and recurrent tumor models, providing a new idea for antitumor chemo-immunotherapy.

PARP inhibitor radiosensitization enhances anti-PD-L1 immunotherapy through stabilizing chemokine mRNA in small cell lung cancer

Immunotherapy (IO) is an effective treatment for various cancers; however, the benefits are modest for small cell lung cancer (SCLC). The poor response of SCLC to anti-PD-1/PD-L1 IO is due in part to the lack of cytotoxic T cells because of limited chemokine expression from SCLC tumors. Immunogenic radiosensitizers that enhance chemokine expression may be a promising strategy forward. Here, we show that the PARP inhibitors (PARPi), including olaparib, talazoparib and veliparib, in combination with radiotherapy (RT) enhance the immune activation and anti-tumor efficacy in SCLC cell lines, patient-derived xenograft (PDX) and syngeneic mouse models. The effect is further enhanced by continued delivery of adjuvant PARPi. The combination treatment (PARPi with RT) activates the cGAS-STING pathway and increases the mRNA levels of the T cell chemo-attractants CCL5 and CXCL10. In addition to upregulation of transcription, the combination treatment increases chemokine CXCL10 protein levels via stabilization of CXCL10 mRNA in an EIF4E2-dependent manner. The incorporation of anti-PD-L1 IO into the PARPi with RT combination therapy further improves the anti-tumor efficacy by increasing T cell infiltration and function. This study thus provides a proof of principle for the combination of PARP inhibitors, RT and anti-PD-L1 IO as a treatment strategy for SCLC.

Thirty Years of BRCA1: Mechanistic Insights and Their Impact on Mutation Carriers

SIGNIFICANCE

Here, we explore the impact of three decades of BRCA1 research on the lives of mutation carriers and propose strategies to improve the prevention and treatment of BRCA1-associated cancer.

Efficacy comparison of PD-1/PD-L1 inhibitor monotherapy and combination with PARPis or antiangiogenic agents in advanced or recurrent endometrial cancer: a systematic review and network meta-analysis

PURPOSE

The network meta-analysis (NMA) was aimed to compare and assess the effectiveness of programmed cell death 1 (PD-1)/ programmed cell death ligand 1 (PD-L1) inhibitor monotherapy or combination therapy with other agents for individuals with advanced or recurrent endometrial cancer (EC).

METHODS

The NMA was registered on the PROSPERO website (ID: CRD42024545968) and multiple databases were queried to retrieve the articles. It assessed the progression-free survival (PFS) and overall survival (OS) of persons with advanced or recurrent EC, as well as those with deficient mismatch repair (dMMR) and proficient mismatch repair (pMMR) in terms of PFS.

RESULTS

The NMA included 12 studies involving a total of 4,515 patients. Compared to chemotherapy, the PD-1/PD-L1 inhibitor monotherapy (hazard ratio [HR], 0.59; 95% confidence interval [CI]: 0.44-0.78) in PFS, combination therapy with poly (ADP-ribose) polymerase inhibitors (PARPis) (HR, 0.53; 95% CI: 0.32-0.89) or with antiangiogenic agents (HR, 0.48; 95% CI: 0.25-0.83) all showed significant improvements in PFS. PD-1/PD-L1 inhibitor monotherapy resulted in a significantly higher OS (HR, 0.61; 95% CI: 0.37-0.97) compared to chemotherapy. Combination therapy with antiangiogenic agents demonstrated the highest efficacy in extending PFS, while the combination with PARPis had the best performance in extending OS. Patients with dMMR and pMMR subtypes derive greater benefits from PD-1/ PD-L1 inhibitor monotherapy and PD-1/PD-L1 inhibitors combined with PARPis respectively.

CONCLUSION

Monotherapy with PD-1/PD-L1 inhibitors and combination therapies with PARPis or antiangiogenic agents demonstrate significant potential for individuals with advanced or recurrent EC.

Cancer brain metastasis: molecular mechanisms and therapeutic strategies

Brain metastases (BMs) are the most common intracranial tumors in adults and the major cause of cancer-related morbidity and mortality. The occurrence of BMs varies according to the type of primary tumors with most frequence in lung cancer, melanoma and breast cancer. Among of them, lung cancer has been reported to have a higher risk of BMs than other types of cancers with 40 ~ 50% of such patients will develop BMs during the course of disease. BMs lead to many neurological complications and result in a poor quality of life and short life span. Although the treatment strategies were improved for brain tumors in the past decades, the prognosis of BMs patients is grim. Poorly understanding of the molecular and cellular characteristics of BMs and the complicated interaction with brain microenvironment are the major reasons for the dismal prognosis of BM patients. Recent studies have enhanced understanding of the mechanisms of BMs. The newly identified potential therapeutic targets and the advanced therapeutic strategies have brought light for a better cure of BMs. In this review, we summarized the mechanisms of BMs during the metastatic course, the molecular and cellular landscapes of BMs, and the advances of novel drug delivery systems for overcoming the obstruction of blood-brain barrier (BBB). We further discussed the challenges of the emerging therapeutic strategies, such as synergistic approach of combining targeted therapy with immunotherapy, which will provide vital clues for realizing the precise and personalized medicine for BM patients in the future.

Exploring the Therapeutic Potential of BRCA1 and BRCA2 as Targets in Canine Oncology: A Comprehensive Review of Their Role in Cancer Development and Treatment

Tumor diseases represent a significant global health challenge, impacting both humans and companion animals, notably dogs. The parallels observed in the pathophysiology of cancer between humans and dogs underscore the importance of advancing comparative oncology and translational research methodologies. Furthermore, dogs serve as valuable models for human cancer research due to shared environments, genetics, and treatment responses. In particular, breast cancer gene 1 (BRCA1) and breast cancer gene 2 (BRCA2), which are critical in human cancer, also influence the development and progression of canine tumors. The role of BRCA1 and BRCA2 in canine cancers remains underexplored, but its potential significance as therapeutic targets is strongly considered. This systematic review aims to broaden the discussion of BRCA1 and BRCA2 beyond mammary tumors, exploring their implications in various canine cancers. By emphasizing the shared genetic underpinnings between species and advocating for a comparative approach, the review indicates the potential of BRCA genes as targets for innovative cancer therapies in dogs, contributing to advances in human and veterinary oncology.

Disulfiram/copper triggers cGAS-STING innate immunity pathway via ROS-induced DNA damage that potentiates antitumor response to PD-1 checkpoint blockade

Immune checkpoint blockades (ICBs) have emerged as the leading strategy for treating advanced malignancies; however, their clinical efficacy is frequently constrained by primary or acquired resistance. Harnessing innate immune signaling to increase lymphocyte infiltration into tumors has been recognized a promising approach to augment the anti-cancer immune response to ICBs. Disulfiram (DSF), an FDA-approved drug for chronic alcoholism, has shown potent anti-tumor effect, particularly when used in combination with copper (Cu). Here, we demonstrated a combination treatment of DSF and Cu (DSF/Cu) robustly activated cancer cell-intrinsic cGAS-STING-dependent innate immune signaling pathway. Further studies revealed that DSF/Cu caused mitochondrial and nuclear DNA damage and the release of cytosolic dsDNA by inducing excessive reactive oxygen species (ROS) generation, thereby triggering innate immunity and enhancing anti-tumor effects. Moreover, DSF/Cu significantly increased the intratumoral infiltration of CD8+ cytotoxic lymphocytes and natural killer (NK) cells, and potentiated the therapeutic efficacy of PD-1 checkpoint blockade in murine tumor models. Overall, our findings provide a rationale underlying the anti-cancer and immunomodulatory function of DSF/Cu and highlight the potential of repurposing DSF to improve responses to ICBs in cancer patients.

Poly (ADP-Ribose) Polymerase 1 Induces Cyclic GMP-AMP Synthase-stimulator of Interferon Genes Pathway Dysregulation to Promote Immune Escape of Colorectal Cancer Cells

Colorectal cancer (CRC) ranks third globally in cancer incidence and mortality, posing a significant human concern. Recent advancements in immunotherapy are noteworthy. This study explores immune modulation for CRC treatment. Initially targeting poly (ADP-ribose) polymerase 1 (PARP-1), a gene overexpressed in CRC tissues per The Cancer Genome Atlas, we examined its correlation with immune cell infiltration using the Tumor Immune Estimation Resource tool. Quantitative reverse transcription polymerase chain reaction assessed PARP-1 mRNA and inflammation-related gene expression in tumor tissues and cells. Assessing CD8 + T-cell proliferation and cytotoxicity towards HCT116 cells involved carboxyfluorescein diacetate succinimidyl ester and lactate dehydrogenase kits. Chemotaxis was gauged using a Transwell system in a CD8 + T-cell coculture setup, with immunofluorescence revealing cyclic GMP-AMP synthase (cGAS) and stimulator of interferon genes (STING) levels in HCT116 cells. Enzyme-linked immunosorbent assay kits measured CD8 + T-cell cytokine secretion. The findings suggested that PARP-1 was overexpressed in CRC tissues and cells and this overexpression was positively correlated with Treg cell infiltration. Overexpression of PARP-1 could significantly reduce the proportion of cGAS and STING-positive cells in HCT116 cells, dampen the proliferation, tumor-killing capacity, and chemotaxis of CD8 + T cells, and inhibit the secretion of related cytokines. The introduction of STING agonists could reverse the effects caused by overexpressed PARP-1. In vivo experiments affirmed the independent anti-tumor effects of PARP-1 inhibitors and STING agonists, synergistically inhibiting tumor growth. Silencing PARP-1 in HCT116 cells potentially boosts CD8 + T-cell activity against these cells through the cGAS-STING pathway.

PARP Inhibitors Differentially Regulate Immune Responses in Distinct Genetic Backgrounds of High-Grade Serous Tubo-Ovarian Carcinoma

SIGNIFICANCE

This work highlights how different PARPis, especially talazoparib, modulate immune-related gene expression in ovarian cancer cells, independent of the cGAS-STING pathway. These findings may improve our understanding of how different PARPis affect the immune system in various genetic backgrounds.

The Phase 3 KEYLYNK-006 Study of Pembrolizumab Plus Olaparib Versus Pembrolizumab Plus Pemetrexed as Maintenance Therapy for Metastatic Nonsquamous NSCLC

INTRODUCTION

Poly (adenosine diphosphate-ribose) inhibitors, including olaparib, upregulate programmed cell death ligand 1, which may increase the efficacy of anti-programmed cell death protein 1 and anti-programmed cell death ligand 1 therapies.

METHODS

In the phase 3 KEYLYNK-006 trial (NCT03976323), eligible adults with previously untreated metastatic nonsquamous NSCLC without targetable genetic alterations who had complete response, partial response, or stable disease after induction therapy with four cycles of pembrolizumab 200 mg every three weeks, pemetrexed 500 mg/m2, and carboplatin area under the concentration-time curve 5 mg/mL/min or cisplatin 75 mg/m2 were randomized in a one-to-one ratio to olaparib 300 mg orally twice daily or pemetrexed every three weeks, both given with up to 31 cycles of pembrolizumab every three weeks. Dual primary endpoints were progression-free survival (PFS) and overall survival (OS). Progression-free survival was tested at interim analysis 2 (i.e., final PFS analysis) and OS at final analysis (FA).

RESULTS

Of 1003 patients who received induction therapy, 672 (67.0%) were randomized to pembrolizumab plus olaparib (n = 337) or pembrolizumab plus pemetrexed (n = 335) in the intention-to-treat population. Median follow-up at FA was 39.9 (range: 28.1-51.5) months. At interim analysis 2, the median (95% confidence interval [CI]) PFS was 7.1 (5.6-8.7) months versus 8.3 (6.9-11.5) months in the olaparib versus pemetrexed groups (hazard ratio = 1.12, 95% CI: 0.92-1.36, p = 0.87). At FA, the median (95% CI) OS was 20.7 (18.0-24.8) months versus 23.0 (19.0-26.4) months (hazard ratio = 1.04, 95% CI: 0.87-1.25, p = 0.6649). Grade 3 to 5 maintenance treatment-related adverse events occurred in 26.1% versus 30.1% of patients, respectively.

CONCLUSION

Pembrolizumab plus maintenance olaparib did not improve PFS or OS versus pembrolizumab plus pemetrexed in previously untreated metastatic nonsquamous NSCLC without targetable genetic alterations.

Riluzole Enhancing Anti-PD-1 Efficacy by Activating cGAS/STING Signaling in Colorectal Cancer

Colorectal cancer is the second leading cause of cancer mortality in the United States. Although immune checkpoint blockade therapies including anti-PD-1/PD-L1 have been successful in treating a subset of patients with colorectal cancer, the response rates remain low. We have found that riluzole, a well-tolerated FDA-approved oral medicine for treating amyotrophic lateral sclerosis, increased intratumoral CD8+ T cells and suppressed tumor growth of colon cancer cells in syngeneic immune-competent mice. Riluzole-mediated tumor suppression was dependent on the presence of CD8+ T cells. Riluzole activates the cytosolic DNA sensing cyclic GMP-AMP synthase (cGAS)/stimulator of interferon genes (STING) pathway in colon cancer cells, resulting in increased expression of IFNβ and IFNβ-regulated genes including CXCL10. Inhibition of ataxia telangiectasia mutated (ATM), but not ATM-related, resulted in a synergistic increase in IFNβ expression, suggesting that riluzole induces ATM-mediated damage response that contributes to cGAS/STING activation. Depletion of cGAS or STING significantly attenuated riluzole-induced expression of IFNβ and CXCL10 as well as increase of intratumoral CD8+ T cells and suppression of tumor growth. These results indicate that riluzole-mediated tumor infiltration of CD8+ T cells and attenuation of tumor growth is dependent on tumor cell-intrinsic STING activation. To determine whether riluzole treatment primes the tumor microenvironment for immune checkpoint modulation, riluzole was combined with anti-PD-1 treatment. This combination showed greater efficacy than either single agent and strongly suppressed tumor growth in vivo. Taken together, our studies indicate that riluzole activates cGAS/STING-mediated innate immune responses, which might be exploited to sensitize colorectal tumors to anti-PD-1/PD-L1 therapies.

Claudin-4 Stabilizes the Genome via Nuclear and Cell-Cycle Remodeling to Support Ovarian Cancer Cell Survival

SIGNIFICANCE

High-grade serous ovarian carcinoma is marked by chromosomal instability, which can serve to promote disease progression and allow cancer to evade therapeutic insults. The report highlights the role of claudin-4 in regulating genomic instability and proposes a novel therapeutic approach to exploit claudin-4-mediated regulation.

Pembrolizumab and olaparib in a cisplatin-refractory testicular cancer patient with a high TMB: first case report

Germ cell tumors (GCTs) represent about 5% of urological cancers affecting mostly younger males with increasing incidence in the last decades. GCTs are very sensitive to cisplatin-based therapy and are highly curable regardless of metastatic stage, likely based on having inherited unique mechanisms of sensitivity to DNA damage and other stressors to prevent germline mutations. Here, we present the first case of a 60-year Caucasian male with a heavily pretreated, cisplatin-refractory extragonadal non-seminomatous GCT (choriocarcinoma) treated with pembrolizumab and olaparib based on high programmed death-ligand 1 expression (tumor proportion score 50% and a combined positive score 55%) high tumor mutational burden, borderline genomic loss of heterozygosity, and a heterozygous variant of uncertain significance in the DNA repair gene ATM, as confirmed by next-generation sequencing (NGS) analysis. Despite a notable decrease in b-hCG within 4 weeks after starting pembrolizumab and olaparib, b-hCG increased steadily again afterward. In addition, the patient developed an immune-related pneumonitis with a fatal outcome 3 months later. NGS with subsequent targeted treatment possibilities might present a helpful step toward precision medicine in GCT patients who have exhausted all other conventional treatment options, and genetic testing should therefore be offered to patients prior to progression.

Tumor immunology and immunotherapy for endometrial cancer

INTRODUCTION

Recent clinical trials show the efficacy of immune checkpoint inhibitors (ICIs) or a combination of ICI and poly (ADP-ribose) polymerase (PARP) inhibitors for advanced or recurrent endometrial cancer. However, the basis for such treatment effects remains unclear, hindering the advancement of personalized therapy.

AREAS COVERED

This review includes a detailed interpretation of subgroup analysis data from phase III clinical trials for endometrial cancer evaluating the efficacy of chemotherapy plus ICIs (NRG-GY018, RUBY, AtTEnd, KEYNOTE-B21) or chemotherapy plus ICI with/without olaparib (DUO-E). We focused on the relationship between obesity, the effect of PARP inhibitors, and tumor immunity in endometrial cancer, searched for relevant literature published from 2000 to 2024 in PubMed, and conducted a narrative review.

EXPERT OPINION

Chemotherapy plus ICI is appropriate for dMMR. Chemotherapy plus ICI and PARP inhibitor may be appropriate for TP53abn type or serous carcinoma because PARP inhibitor enhances the efficacy of ICI by activating the cyclic guanosine monophosphate-adenosine monophosphate synthase (cGAS)-stimulator of interferon genes (STING) pathway. Obese patients may benefit more from ICIs, and this appears to cause the variation in efficacy between regions/countries. Administration for measurable disease appears important to increase the effect of ICIs. Diet and exercise may also be important factors.

Recent and Future Developments in the Use of Poly (ADP-ribose) Polymerase Inhibitors for Prostate Cancer

BACKGROUND AND OBJECTIVE

Advanced prostate cancer (PCa) is enriched for alterations in DNA damage repair genes; poly (ADP-ribose) polymerase (PARP) inhibitors (PARPi) are a class of drugs that have demonstrated effectiveness in PCa, particularly in tumors with alterations in BRCA1/2 and other homologous recombination repair (HRR) genes, acting through a synthetic lethal mechanism. To prevent or delay drug resistance, and to expand the patient population that can benefit from this class of drug, combination treatment strategies have been developed in preclinical and clinical studies.

METHODS

This review examines the latest developments in clinical trials testing PARPi for advanced PCa and their emerging role in earlier disease settings. Furthermore, it discusses the critical role of careful patient selection and identification of additional biomarkers to enhance treatment efficacy.

KEY FINDINGS AND LIMITATIONS

Two PARPi (olaparib and rucaparib) have been approved as monotherapy in metastatic castration-resistant PCa, thereby establishing the first biomarker-guided drug indications in PCa. Several combinations of PARPi with androgen receptor pathway inhibitors have now also been approved. Anemia and fatigue are the main adverse events associated with this drug class in clinical trials; gastrointestinal toxicities are common but usually manageble.

CONCLUSIONS AND CLINICAL IMPLICATIONS

PARPi are active against PCa with HRR mutations, especially in those with germline or somatic BRCA1/2 mutations.  There is still a need to further optimize patient stratification strategies, particularly for combination approaches. Future research should focus on refining predictive biomarkers, improving treatment delivery strategies, and exploring the potential benefits of PARPi in earlier stages of the disease.

PATIENT SUMMARY

Here, we summarize the results from clinical trials testing different poly (ADP-ribose) polymerase inhibitors (PARPi), a novel targeted drug class, in prostate cancer. Overall, the data from these trials confirm the efficacy of this drug class in those metastatic prostate cancers that show specific gene alterations, such as mutations in the BRCA1/2 genes. Several studies combining PARPi with other standard drugs for prostate cancer suggest that there may be efficacy in larger patient populations, but some of these data still need validation in longer follow-up analyses.

CDC7 Inhibition Potentiates Antitumor Efficacy of PARP Inhibitor in Advanced Ovarian Cancer

Poly (ADP-ribose) Polymerase inhibitors (PARPi) have demonstrated remarkable clinical efficacy in treating ovarian cancer (OV) with BRCA1/2 mutations. However, drug resistance inevitably limits their clinical applications and there is an urgent need for improved therapeutic strategies to enhance the clinical utility of PARPi, such as Olaparib. Here, compelling evidence indicates that sensitivity of PARPi is associated with cell cycle dysfunction. Through high-throughput drug screening with a cell cycle kinase inhibitor library, XL413, a potent cell division cycle 7 (CDC7) inhibitor, is identified which can synergistically enhance the anti-tumor efficacy of Olaparib. Mechanistically, the combined administration of XL413 and Olaparib demonstrates considerable DNA damage and DNA replication stress, leading to increased sensitivity to Olaparib. Additionally, a robust type-I interferon response is triggered through the induction of the cGAS/STING signaling pathway. Using murine syngeneic tumor models, the combination treatment further demonstrates enhanced antitumor immunity, resulting in tumor regression. Collectively, this study presents an effective treatment strategy for patients with advanced OV by combining CDC7 inhibitors (CDC7i) and PARPi, offering a promising therapeutic approach for patients with limited response to PARPi.

A STAT3-STING-IFN axis controls the metastatic spread of small cell lung cancer

Small cell lung cancer (SCLC) is an aggressive neuroendocrine tumor characterized by a high metastatic potential with an overall survival rate of ~5%. The transcription factor signal transducer and activator of transcription 3 (STAT3) is overexpressed by >50% of tumors, including SCLC, but its role in SCLC development and metastasis is unclear. Here, we show that, while STAT3 deletion restricts primary tumor growth, it paradoxically enhances metastatic spread by promoting immune evasion. This occurs because STAT3 is crucial for maintaining the immune sensor stimulator of interferon (IFN) genes (STING). Without STAT3, the cyclic adenosine monophosphate-guanosine monophosphate synthase-STING pathway is inactive, resulting in decreased type I IFN secretion and an IFN gene signature. Importantly, restoration of IFN signaling through re-expression of endogenous STING, enforced expression of IFN response factor 7 or administration of recombinant type I IFN re-established antitumor immunity, inhibiting metastatic SCLC in vivo. These data show the potential of augmenting the innate immune response to block metastatic SCLC.

Degradation of PARP1 by MARCHF3 in tumor cells triggers cCAS-STING activation in dendritic cells to regulate antitumor immunity in hepatocellular carcinoma

BACKGROUND

Resistance to immune checkpoint inhibitors (ICIs) significantly limits the efficacy of immunotherapy in patients with hepatocellular carcinoma (HCC). However, the mechanisms underlying immunotherapy resistance remain poorly understood. Our aim was to clarify the role of membrane-associated ring-CH-type finger 3 (MARCHF3) in HCC within the framework of anti-programmed cell death protein-1 (PD-1) therapy.

METHODS

MARCHF3 was identified in the transcriptomic profiles of HCC tumors exhibiting different responses to ICIs. In humans, the correlation between MARCHF3 expression and the tumor microenvironment (TME) was assessed via multiplex immunohistochemistry. In addition, MARCHF3 expression in tumor cells and immune cell infiltration were assessed by flow cytometry.

RESULTS

MARCHF3 was significantly upregulated in tumors from patients who responded to ICIs. Increased MARCHF3 expression in HCC cells promoted dendritic cell (DC) maturation and stimulated CD8+ T-cell activation, thereby augmenting tumor control. Mechanistically, we identified MARCHF3 as a pivotal regulator of the DNA damage response. It directly interacted with Poly(ADP-Ribose) Polymerase 1 (PARP1) via K48-linked ubiquitination, leading to PARP1 degradation. This process promoted the release of double-strand DNA and activated cCAS-STING in DCs, thereby initiating DC-mediated antigen cross-presentation and CD8+ T-cell activation. Additionally, ATF4 transcriptionally regulated MARCHF3 expression. Notably, the PARP1 inhibitor olaparib augmented the efficacy of anti-PD-1 immunotherapy in both subcutaneous and orthotopic HCC mouse models.

CONCLUSIONS

MARCHF3 has emerged as a pivotal regulator of the immune landscape in the HCC TME and is a potent predictive biomarker for HCC. Combining interventions targeting the DNA damage response with ICIs is a promising treatment strategy for HCC.

Targeting YES1 Disrupts Mitotic Fidelity and Potentiates the Response to Taxanes in Triple-Negative Breast Cancer

Clinical trials examining broad-spectrum Src family kinase (SFK) inhibitors revealed significant dose-limiting toxicities, preventing advancement for solid tumors. SFKs are functionally heterogeneous, thus targeting individual members is a potential strategy to elicit antitumor efficacy while avoiding toxicity. Here, we identified that YES1 is the most highly overexpressed SFK in triple-negative breast cancer (TNBC) and is associated with poor patient outcomes. Disrupting YES1, genetically or pharmacologically, induced aberrant mitosis, centrosome amplification, multipolar spindles, and chromosomal instability. Mechanistically, YES1 sustained FOXM1 protein levels and elevated expression of FOXM1 target genes that control centrosome function and are essential for effective and accurate mitotic progression. In both in vitro and in vivo TNBC models, YES1 suppression potentiated the efficacy of taxanes, cornerstone drugs for TNBC that require elevated chromosomal instability for efficacy. Clinically, elevated expression of YES1 was associated with worse overall survival of patients with TNBC treated with taxane and anthracycline combination regimens. Together, this study demonstrates that YES1 is an essential regulator of genome stability in TNBC that can be leveraged to improve taxane efficacy.  Significance: YES1 is a sentinel regulator of genomic maintenance that controls centrosome homeostasis and chromosome stability through FOXM1, revealing this pathway as a therapeutic vulnerability for enhancing taxane efficacy in triple-negative breast cancer.

Immunotherapy for ovarian cancer: towards a tailored immunophenotype-based approach

Despite documented evidence that ovarian cancer cells express immune-checkpoint molecules, such as PD-1 and PD-L1, and of a positive correlation between the presence of tumour-infiltrating lymphocytes and favourable overall survival outcomes in patients with this tumour type, the results of trials testing immune-checkpoint inhibitors (ICIs) in these patients thus far have been disappointing. The lack of response to ICIs can be attributed to tumour heterogeneity as well as inherent or acquired resistance associated with the tumour microenvironment (TME). Understanding tumour immunobiology, discovering biomarkers for patient selection and establishing optimal treatment combinations remains the hope but also a key challenge for the future application of immunotherapy in ovarian cancer. In this Review, we summarize results from trials testing ICIs in patients with ovarian cancer. We propose the implementation of a systematic CD8+ T cell-based immunophenotypic classification of this malignancy, followed by discussions of the preclinical data providing the basis to treat such immunophenotypes with combination immunotherapies. We posit that the integration of an accurate TME immunophenotype characterization with genetic data can enable the design of tailored therapeutic approaches and improve patient recruitment in clinical trials. Lastly, we propose a roadmap incorporating tissue-based profiling to guide future trials testing adoptive cell therapy approaches and assess novel immunotherapy combinations while promoting collaborative research.

DNA repair-dependent immunogenic liabilities in colorectal cancer: opportunities from errors

Colorectal cancer (CRC) remains one of the major causes of cancer death worldwide. Chemotherapy continues to serve as the primary treatment modality, while immunotherapy is largely ineffective for the majority of CRC patients. Seminal discoveries have emphasized that modifying DNA damage response (DDR) mechanisms confers both cell-autonomous and immune-related vulnerabilities across various cancers. In CRC, approximately 15% of tumours exhibit alterations in the mismatch repair (MMR) machinery, resulting in a high number of neoantigens and the activation of the type I interferon response. These factors, in conjunction with immune checkpoint blockades, collectively stimulate anticancer immunity. Furthermore, although less frequently, somatic alterations in the homologous recombination (HR) pathway are observed in CRC; these defects lead to genome instability and telomere alterations, supporting the use of poly (ADP-ribose) polymerase (PARP) inhibitors in HR-deficient CRC patients. Additionally, other DDR inhibitors, such as Ataxia Telangiectasia and Rad3-related protein (ATR) inhibitors, have shown some efficacy both in preclinical models and in the clinical setting, irrespective of MMR proficiency. The aim of this review is to elucidate how preexisting or induced vulnerabilities in DNA repair pathways represent an opportunity to increase tumour sensitivity to immune-based therapies in CRC.

Cold and hot tumors: from molecular mechanisms to targeted therapy

Immunotherapy has made significant strides in cancer treatment, particularly through immune checkpoint blockade (ICB), which has shown notable clinical benefits across various tumor types. Despite the transformative impact of ICB treatment in cancer therapy, only a minority of patients exhibit a positive response to it. In patients with solid tumors, those who respond well to ICB treatment typically demonstrate an active immune profile referred to as the "hot" (immune-inflamed) phenotype. On the other hand, non-responsive patients may exhibit a distinct "cold" (immune-desert) phenotype, differing from the features of "hot" tumors. Additionally, there is a more nuanced "excluded" immune phenotype, positioned between the "cold" and "hot" categories, known as the immune "excluded" type. Effective differentiation between "cold" and "hot" tumors, and understanding tumor intrinsic factors, immune characteristics, TME, and external factors are critical for predicting tumor response and treatment results. It is widely accepted that ICB therapy exerts a more profound effect on "hot" tumors, with limited efficacy against "cold" or "altered" tumors, necessitating combinations with other therapeutic modalities to enhance immune cell infiltration into tumor tissue and convert "cold" or "altered" tumors into "hot" ones. Therefore, aligning with the traits of "cold" and "hot" tumors, this review systematically delineates the respective immune characteristics, influencing factors, and extensively discusses varied treatment approaches and drug targets based on "cold" and "hot" tumors to assess clinical efficacy.

Unlocking the potential of immunotherapy in platinum-resistant ovarian cancer: rationale, challenges, and novel strategies

Ovarian cancer is a significant global health challenge, with cytoreductive surgery and platinum-based chemotherapy serving as established primary treatments. Unfortunately, most patients relapse and ultimately become platinum-resistant, at which point there are limited effective treatment options. Given the success of immunotherapy in inducing durable treatment responses in several other cancers, its potential in platinum-resistant ovarian cancer (PROC) is currently being investigated. However, in unselected advanced ovarian cancer populations, researchers have reported low response rates to immune checkpoint inhibition, and thus far, no validated biomarkers are predictive of response. Understanding the intricate interplay between platinum resistance, immune recognition, and the tumour microenvironment (TME) is crucial. In this review, we examine the research challenges encountered thus far, the biological rationale for immunotherapy, the underlying mechanisms of immune resistance, and new strategies to overcome resistance.

Consensus, debate, and prospective on pancreatic cancer treatments

Pancreatic cancer remains one of the most aggressive solid tumors. As a systemic disease, despite the improvement of multi-modality treatment strategies, the prognosis of pancreatic cancer was not improved dramatically. For resectable or borderline resectable patients, the surgical strategy centered on improving R0 resection rate is consensus; however, the role of neoadjuvant therapy in resectable patients and the optimal neoadjuvant therapy of chemotherapy with or without radiotherapy in borderline resectable patients were debated. Postoperative adjuvant chemotherapy of gemcitabine/capecitabine or mFOLFIRINOX is recommended regardless of the margin status. Chemotherapy as the first-line treatment strategy for advanced or metastatic patients included FOLFIRINOX, gemcitabine/nab-paclitaxel, or NALIRIFOX regimens whereas 5-FU plus liposomal irinotecan was the only standard of care second-line therapy. Immunotherapy is an innovative therapy although anti-PD-1 antibody is currently the only agent approved by for MSI-H, dMMR, or TMB-high solid tumors, which represent a very small subset of pancreatic cancers. Combination strategies to increase the immunogenicity and to overcome the immunosuppressive tumor microenvironment may sensitize pancreatic cancer to immunotherapy. Targeted therapies represented by PARP and KRAS inhibitors are also under investigation, showing benefits in improving progression-free survival and objective response rate. This review discusses the current treatment modalities and highlights innovative therapies for pancreatic cancer.

STING Agonist Delivered by Neutrophil Membrane-Coated Gold Nanoparticles Exerts Synergistic Tumor Inhibition with Radiotherapy

Radiotherapy (RT) is one of the major treatments for cancers and a promising initiator of immune response. Gold nanoparticles are a promising radiosensitizer. In this study, we sought to optimize the drug delivery efficiency of gold nanoparticles and explore their function in delivering stimulator of interferon genes (STING) agonists with or without RT. Gold nanoparticles covalent to MSA-2 (MSA-Au) were mixed with cRGD-modified neutrophil membranes to obtain M-Au@RGD-NM. We explored the treatment efficiency of M-Au@RGD-NM combined with RT. Immune cell regulation and STING pathway activation were detected. We successfully prepared M-Au@RGD-NM with significant tumor suppression by induction of ROS and the resulting DNA damage. In vivo dynamic imaging showed that M-Au@RGD-NM was mainly targeted to radiated tumors. Tumor-bearing mice showed significant tumor inhibition following a combination therapy. M-Au@RGD-NM significantly activated the STING pathway and regulated the whole-body immune response. Locally radiated tumors showed dendritic cells mature, CD8+ T cells upregulation, and M1 polarization, with systematic immune response demonstrated by CD8+ T cell infiltration in abscopal tumors. In this study, we synthesized M-Au@RGD-NM loading MSA-2. Following characterization, we found that RT-based M-Au@RGD-NM treatment achieved good antitumor effects, tumor RT enhancement, and induction of an immune response via STING activation.

PARP inhibitors enhance antitumor immune responses by triggering pyroptosis via TNF-caspase 8-GSDMD/E axis in ovarian cancer

BACKGROUND

In addition to their established action of synthetic lethality in tumor cells, poly(ADP-ribose) polymerase inhibitors (PARPis) also orchestrate tumor immune microenvironment (TIME) that contributes to suppressing tumor growth. However, it remains not fully understood whether and how PARPis trigger tumor-targeting immune responses.

METHODS

To decode the immune responses reshaped by PARPis, we conducted T-cell receptor (TCR) sequencing and immunohistochemical (IHC) analyses of paired clinical specimens before and after niraparib monotherapy obtained from a prospective study, as well as ID8 mouse ovarian tumors. To validate the induction of immunogenic cell death (ICD) by PARPis, we performed immunofluorescence/IHC staining with homologous recombination deficiency tumor cells and patient-derived xenograft tumor tissues, respectively. To substantiate that PARPis elicited tumor cell pyroptosis, we undertook comprehensive assessments of the cellular morphological features, cleavage of gasdermin (GSDM) proteins, and activation of TNF-caspase signaling pathways through genetic downregulation/depletion and selective inhibition. We also evaluated the critical role of pyroptosis in tumor suppression and immune activation following niraparib treatment using a syngeneic mouse model with implanting CRISPR/Cas9 edited Gsdme-/ - ID8 tumor cells into C57BL/6 mice.

RESULTS

Our findings revealed that PARPis augmented the proportion of neoantigen-recognized TCR clones and TCR clonal expansion, and induced an inflamed TIME characterized by increased infiltration of both innate and adaptive immune cells. This PARPis-strengthened immune response was associated with the induction of ICD, specifically identified as pyroptosis, which possessed distinctive morphological features and GSDMD/E cleavage. It was validated that the cleavage of GSDMD/E was due to elevated caspase 8 activity downstream of the TNFR1, rather than FAS and TRAIL-R. On PARP inhibition, the NF-κB signaling pathway was activated, leading to increased secretion of TNF-α and subsequent initiation of the TNFR1-caspase 8 cascade. Impeding pyroptosis through the depletion of Gsdme significantly compromised the tumor-suppressing effects of PARP inhibition and undermined the anti-immune response in the syngeneic ID8 mouse model.

CONCLUSIONS

PARPis induce a specific type of ICD called pyroptosis via TNF-caspase 8-GSDMD/E axis, resulting in an inflamed TIME and augmentation of tumor-targeting immune responses. These findings deepen our understanding of PARPis activities and point toward a promising avenue for synergizing PARPis with immunotherapeutic interventions.

TRIAL REGISTRATION NUMBER

NCT04507841.

Neuroendocrine transdifferentiation in human cancer: molecular mechanisms and therapeutic targets

Neuroendocrine transdifferentiation (NEtD), also commonly referred to as lineage plasticity, emerges as an acquired resistance mechanism to molecular targeted therapies in multiple cancer types, predominately occurs in metastatic epidermal growth factor receptor (EGFR)-mutant non-small cell lung cancer treated with EGFR tyrosine kinase inhibitors and metastatic castration-resistant prostate cancer treated with androgen receptor targeting therapies. NEtD tumors are the lethal cancer histologic subtype with unfavorable prognosis and limited treatment. A comprehensive understanding of molecular mechanism underlying targeted-induced plasticity could greatly facilitate the development of novel therapies. In the past few years, increasingly elegant studies indicated that NEtD tumors share key the convergent genomic and phenotypic characteristics irrespective of their site of origin, but also embrace distinct change and function of molecular mechanisms. In this review, we provide a comprehensive overview of the current understanding of molecular mechanism in regulating the NEtD, including genetic alterations, DNA methylation, histone modifications, dysregulated noncoding RNA, lineage-specific transcription factors regulation, and other proteomic alterations. We also provide the current management of targeted therapies in clinical and preclinical practice.

Strategies for the prevention or reversal of PARP inhibitor resistance

INTRODUCTION

Advances in our understanding of tumor biology shed light on hallmarks of cancer development and progression that include dysregulated DNA damage repair (DDR) machinery. Leveraging the underlying tumor genomic instability and tumor-specific defects in DDR, Poly (ADP-ribose) polymerase (PARP) inhibitors (PARPi) induced DNA damage emerges as a novel non-chemotherapy therapeutic opportunity. PARPis are currently approved in multiple tumor types, with the largest benefit seen in tumors with homologous recombination repair (HRR) deficiency, including germline and somatic mutations in BRCA1/2 genes (BRCA) and other pathway members such as PALB2 and Rad51c.

AREAS COVERED

This review article summarizes the current approval landscape and known and proposed mechanisms of resistance to PARPi. Further, therapeutic strategies to overcome PARPi resistance are discussed, including ongoing clinical trials.

EXPERT OPINION

PARPi have proven to be a safe and effective therapy and represents a cornerstone treatment across multiple solid tumor types. Elucidating innate and acquired mechanisms of resistance, coupled with the emergence of novel therapeutic options to capitalize on the activity of PARPi and prevent or reverse the acquisition of resistance, provides an opportunity to further expand the role of PARPi in cancer therapy.

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

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

Ovarian cancer: Diagnosis and treatment strategies (Review)

Ovarian cancer is a malignant tumor that seriously endangers health. Early ovarian cancer symptoms are frequently challenging to detect, resulting in a large proportion of patients reaching an advanced stage when diagnosed. Conventional diagnosis relies heavily on serum biomarkers and pathological examination, but their sensitivity and specificity require improvement. Targeted therapy inhibits tumor growth by targeting certain characteristics of tumor cells, such as signaling pathways and gene mutations. However, the effectiveness of targeted therapy varies among individuals due to differences in their unique biological characteristics and requires individualized strategies. Immunotherapy is a promising treatment for ovarian cancer due to its long-lasting antitumor effect. Nevertheless, issues such as variable efficacy, immune-associated adverse effects and drug resistance remain to be resolved. The present review discusses the diagnostic strategies, rationale, treatment strategies and prospects of targeted therapy and immunotherapy for ovarian cancer.

PARP inhibition with rucaparib alone followed by combination with atezolizumab: Phase Ib COUPLET clinical study in advanced gynaecological and triple-negative breast cancers

BACKGROUND

Combining PARP inhibitors (PARPis) with immune checkpoint inhibitors may improve clinical outcomes in selected cancers. We evaluated rucaparib and atezolizumab in advanced gynaecological or triple-negative breast cancer (TNBC).

METHODS

After identifying the recommended dose, patients with PARPi-naive BRCA-mutated or homologous recombination-deficient/loss-of-heterozygosity-high platinum-sensitive ovarian cancer or TNBC received rucaparib plus atezolizumab. Tumour biopsies were collected pre-treatment, during single-agent rucaparib run-in, and after starting combination therapy.

RESULTS

The most common adverse events with rucaparib 600 mg twice daily and atezolizumab 1200 mg on Day 1 every 3 weeks were gastrointestinal effects, fatigue, liver enzyme elevations, and anaemia. Responding patients typically had BRCA-mutated tumours and higher pre-treatment tumour levels of PD-L1 and CD8 + T cells. Markers of DNA damage repair decreased during rucaparib run-in and combination treatment in responders, but typically increased in non-responders. Apoptosis signature expression showed the reverse. CD8 + T-cell activity and STING pathway activation increased during rucaparib run-in, increasing further with atezolizumab.

CONCLUSIONS

In this small study, rucaparib plus atezolizumab demonstrated acceptable safety and activity in BRCA-mutated tumours. Increasing anti-tumour immunity and inflammation might be a key mechanism of action for clinical benefit from the combination, potentially guiding more targeted development of such regimens.

CLINICAL TRIAL REGISTRATION

ClinicalTrials.gov (NCT03101280).

Targeting DNA Damage Response Deficiency in Thoracic Cancers

Thoracic cancers comprise non-small cell lung cancers (NSCLCs), small cell lung cancers (SCLCs) and malignant pleural mesotheliomas (MPM). Collectively, they account for the highest rate of death from malignancy worldwide. Genomic instability is a universal feature of cancer, which fuels mutations and tumour evolution. Deficiencies in DNA damage response (DDR) genes amplify genomic instability. Homologous recombination deficiency (HRD), resulting from BRCA1/BRCA2 inactivation, is exploited for therapeutic synthetic lethality with poly-ADP ribose polymerase (PARP) inhibitors in breast and ovarian cancers, as well as in prostate and pancreatic cancers. However, DDR deficiency and its therapeutic implications are less well established in thoracic cancers. Emerging evidence suggests that a subset of thoracic cancers may harbour DDR deficiency and may, thus, be effectively targeted with DDR agents. Here, we review the current evidence surrounding DDR in thoracic cancers and discuss the challenges and promise for achieving clinical benefit with such therapeutics.

Application of PARP inhibitors combined with immune checkpoint inhibitors in ovarian cancer

The advent of polyadenosine diphosphate ribose polymerase inhibitors (PARPi) has brought about significant changes in the field of ovarian cancer treatment. However, in 2022, Rucaparib, Olaparib, and Niraparib, had their marketing approval revoked for third-line and subsequent therapies due to an increased potential for adverse events. Consequently, the exploration of new treatment modalities remains imperative. Recently, the integration of PARPi with immune checkpoint inhibitors (ICIs) has emerged as a potential remedy option within the context of ovarian cancer. This article offers a comprehensive examination of the mechanisms and applications of PARPi and ICIs in the treatment of ovarian cancer. It synthesizes the existing evidence supporting their combined use and discusses key considerations that merit attention in ongoing development efforts.

DNA damage response in brain tumors: A Society for Neuro-Oncology consensus review on mechanisms and translational efforts in neuro-oncology

DNA damage response (DDR) mechanisms are critical to maintenance of overall genomic stability, and their dysfunction can contribute to oncogenesis. Significant advances in our understanding of DDR pathways have raised the possibility of developing therapies that exploit these processes. In this expert-driven consensus review, we examine mechanisms of response to DNA damage, progress in development of DDR inhibitors in IDH-wild-type glioblastoma and IDH-mutant gliomas, and other important considerations such as biomarker development, preclinical models, combination therapies, mechanisms of resistance and clinical trial design considerations.

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

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

Role of interferon dependent and independent signaling pathways: Implications in cancer

Interferons (IFNs) are a class of cytokines with potent antiviral and immunomodulatory properties that regulate the immune system through multiple signaling pathways. In cancer, IFNs are vital to both tumor-intrinsic and extrinsic mechanisms that affect the quality of antitumor immunity as well as response to cancer treatments, including immunotherapy. However, there is a need for a deeper and better understanding of the mechanisms by which IFNs elicit immune signalling in cancerous cells. In this review, we focus on the IFN- dependent and independent axes in cancer as targetable hubs for new immunotherapeutic approaches to boost the treatment efficacy and to circumvent cancer resistance leading to improved clinical outcomes.

FLT1 activation in cancer cells promotes PARP-inhibitor resistance in breast cancer

Acquired resistance to PARP inhibitors (PARPi) remains a treatment challenge for BRCA1/2-mutant breast cancer that drastically shortens patient survival. Although several resistance mechanisms have been identified, none have been successfully targeted in the clinic. Using new PARPi-resistance models of Brca1- and Bard1-mutant breast cancer generated in-vivo, we identified FLT1 (VEGFR1) as a driver of resistance. Unlike the known role of VEGF signaling in angiogenesis, we demonstrate a novel, non-canonical role for FLT1 signaling that protects cancer cells from PARPi in-vivo through a combination of cell-intrinsic and cell-extrinsic pathways. We demonstrate that FLT1 blockade suppresses AKT activation, increases tumor infiltration of CD8+ T cells, and causes dramatic regression of PARPi-resistant breast tumors in a T-cell-dependent manner. Moreover, PARPi-resistant tumor cells can be readily re-sensitized to PARPi by targeting Flt1 either genetically (Flt1-suppression) or pharmacologically (axitinib). Importantly, a retrospective series of breast cancer patients treated with PARPi demonstrated shorter progression-free survival in cases with FLT1 activation at pre-treatment. Our study therefore identifies FLT1 as a potential therapeutic target in PARPi-resistant, BRCA1/2-mutant breast cancer.

Injectable Nanocomposite Hydrogels Improve Intraperitoneal Co-delivery of Chemotherapeutics and Immune Checkpoint Inhibitors for Enhanced Peritoneal Metastasis Therapy

Intraperitoneal co-delivery of chemotherapeutic drugs (CDs) and immune checkpoint inhibitors (ICIs) brings hope to improve treatment outcomes in patients with peritoneal metastasis from ovarian cancer (OC). However, current intraperitoneal drug delivery systems face issues such as rapid drug clearance from lymphatic drainage, heterogeneous drug distribution, and uncontrolled release of therapeutic agents into the peritoneal cavity. Herein, we developed an injectable nanohydrogel by combining carboxymethyl chitosan (CMCS) with bioadhesive nanoparticles (BNPs) based on polylactic acid-hyperbranched polyglycerol. This system enables the codelivery of CD and ICI into the intraperitoneal space to extend drug retention. The nanohydrogel is formed by cross-linking of aldehyde groups on BNPs with amine groups on CMCS via reversible Schiff base bonds, with CD and ICI loaded separately into BNPs and CMCS network. BNP/CMCS nanohydrogel maintained the activity of the biomolecules and released drugs in a sustained manner over a 7 day period. The adhesive property, through the formation of Schiff bases with peritoneal tissues, confers BNPs with an extended residence time in the peritoneal cavity after being released from the nanohydrogel. In a mouse model, BNP/CMCS nanohydrogel loaded with paclitaxel (PTX) and anti-PD-1 antibodies (αPD-1) significantly suppressed peritoneal metastasis of OC compared to all other tested groups. In addition, no systemic toxicity of nanohydrogel-loaded PTX and αPD-1 was observed during the treatment, which supports potential translational applications of this delivery system.

Novel Bifunctional Conjugates Targeting PD-L1/PARP7 as Dual Immunotherapy for Potential Cancer Treatment

Bifunctional conjugates targeting PD-L1/PARP7 were designed, synthesized, and evaluated for the first time. Compounds B3 and C6 showed potent activity against PD-1/PD-L1 interaction (IC50 = 0.426 and 0.342 μM, respectively) and PARP7 (IC50 = 2.50 and 7.05 nM, respectively). They also displayed excellent binding affinity with hPD-L1, approximately 100-200-fold better than that of hPD-1. Both compounds restored T-cell function, leading to the increase of IFN-γ secretion. In the coculture assay, B3 and C6 enhanced the killing activity of MDA-MB-231 cells by Jurkat T cells in a concentration-dependent manner. Furthermore, B3 and C6 displayed significant in vivo antitumor efficacy in a melanoma B16-F10 tumor mouse model, more than 5.3-fold better than BMS-1 (a PD-L1 inhibitor) and RBN-2397 (a PARP7i clinical candidate) at the dose of 25 mg/kg, without observable side effects. These results provide valuable insight and understanding for developing bifunctional conjugates for potential anticancer therapy.

Androgen receptor, PARP signaling, and tumor microenvironment: the 'perfect triad' in prostate cancer?

Aberrations in the homologous recombination repair (HRR) pathway in prostate cancer (PCa) provide a unique opportunity to develop therapeutic strategies that take advantage of the reduced tumor ability to repair DNA damage. Poly-ADP-ribose polymerase (PARP) inhibitors (PARPi) have been shown to prolong the survival of PCa patients with HRR defects, particularly in those with Breast Cancer type 1 susceptibility protein/Breast Cancer type 2 susceptibility protein alterations. To expand the benefit of PARPi to patients without detectable HRR alterations, multiple preclinical and clinical studies are addressing potential synergies between PARPi and androgen receptor signaling inhibitors, and these strategies are also being evaluated in combination with other drugs such as immune checkpoint inhibitors. However, the effectiveness of these combining therapies could be hindered by multiple mechanisms of resistance, including also the role played by the immunosuppressive tumor microenvironment. In this review, we summarize the use of PARPi in PCa and the potential synergies with different molecular pathways. However, numerous unanswered questions remain, including the identification of the patient population that could benefit most from PARPi, determining whether to use PARPi as monotherapy or in combination, and finding the optimal timing of PARPi, expanding the use of genomic tests, and optimizing combination therapies.

Niraparib enhances antitumor immunity and contributes to the efficacy of PD-L1 blockade in cervical cancer

PURPOSE

With the development of immunotherapy research, the role of immune checkpoint blockade (ICB) in the treatment of cervical cancer has been emphasized, but many patients still can't receive long-term benefits from ICB. Poly ADP ribose polymerase inhibitor (PARPi) has been proved to exert significant antitumor effects in multiple solid tumors. Whether cervical cancer patients obtain better benefits from the treatment regimen of PARPi combined with ICB remains unclear.

METHODS

The alteration of PD-L1 expression induced by niraparib in cervical cancer cells and its underlying mechanism were assessed by western blot and immunofluorescence and quantitative real-time polymerase chain reaction (qRT-PCR).The regulation of PTEN by KDM5A was confirmed using Chromatin immunoprecipitation (ChIP) assay and RNA interference. Analyzing the relationship between PD-L1 and immune effector molecules through searching online databases. Therapeutic efficacy of niraparib, PD-L1 blockade or combination was assessed in syngeneic tumor model. The changes of immune cells and cytokines in vivo was detected by immunohistochemistry (IHC) and qRT-PCR.

RESULTS

We found that niraparib upregulated PD-L1 expression and potentiated the antitumor effects of PD-L1 blockade in a murine cervical cancer model. Niraparib inhibited the Pten expression by increasing the abundance of KDM5A, which expanded PD-L1 abundance through activating the PI3K-AKT-S6K1 pathway. PD-L1 was positively correlated with immune effector molecules including TNF-α, IFN-γ, granzyme A and granzyme B based on biological information analysis. Niraparib increased the infiltration of CD8+ T cells and the level of IFN-γ, granzyme B in vivo.

CONCLUSION

Our findings demonstrates the regulation of niraparib on local immune microenvironment of cervical cancer, and provides theoretical basis for supporting the combination of PARPi and PD-L1 blockade as a potential treatment for cervical cancer.