Combining radiation and the ATR inhibitor berzosertib activates STING signaling and enhances immunotherapy via inhibiting SHP1 function in colorectal cancer

Mapping the intellectual structure and landscape of colorectal cancer immunotherapy: A bibliometric analysis

Immunotherapy, particularly immune checkpoint inhibitor (ICIs) therapy, stands as an innovative therapeutic approach currently garnering substantial attention in cancer treatment. It has become a focal point of numerous studies, showcasing significant potential in treating malignancies, including lung cancer and melanoma. The objective of this research is to analyze publications regarding immunotherapy for colorectal cancer (CRC), investigating their attributes and identifying the current areas of interest and cutting-edge advancements. We took into account the publications from 2002 to 2022 included in the Web of Science Core Collection. Bibliometric analysis and visualization were conducted using CiteSpace, VOSviewer, R-bibliometrix, and Microsoft Excel. The quantity of publications associated with this domain has been steadily rising over the years, encompassing 3753 articles and 1498 reviews originating from 573 countries and regions, involving 19,166 institutions, 1011 journals, and 32,301 authors. In this field, China, the United States, and Italy are the main countries that come forward for publishing. The journal with the greatest impact factor is CA-A Cancer Journal for Clinicians. Romain Cohen leads in the number of publications, while Le Dt stands out as the most influential author. The immune microenvironment and immune infiltration are emerging as key hotspots and future research directions in this domain. This research carries out an extensive bibliometric examination of immunotherapy for colorectal cancer, aiding researchers in understanding current focal points, investigating possible avenues for research, and recognizing forthcoming development trends.

Gut microbiota affects the activation of STING pathway and thus participates in the progression of colorectal cancer

BACKGROUND

More and more studies showed that gut microbiota was closely related to the development of colorectal cancer (CRC). However, the specific pathway of gut microbiota regulating CRC development is still unknown.

METHODS

We collected fecal samples from 14 CRC patients and 20 normal volunteers for 16 S sequencing analysis. At the same time, 14 CRC patients' tumors and their adjacent tissues were collected for the detection of STING pathway related protein level. Mice were injected with azoxymethane (AOM) to establish an animal model of CRC, and antibiotics were given at the same time to evaluate the influence of gut microbiota on STING pathway and whether it was involved in regulating the tumor development of CRC mice.

RESULTS

The sequencing results showed that compared with the normal group, the gut microbiota gut microbiota of CRC patients changed significantly at different species classification levels. At the level of genus, Akkermansia, Ligilactobacillus and Subdoligranulum increased the most in CRC patients, while Bacteroides and Dialister decreased sharply. The expression of STING-related protein was significantly down-regulated in CRC tumor tissues. Antibiotic treatment of CRC mice can promote the development of tumor and inhibit the activation of STING pathway.

CONCLUSION

Gut microbiota participates in CRC progress by mediating STING pathway activation.

KDM3A Ablation Activates Endogenous Retrovirus Expression to Stimulate Antitumor Immunity in Gastric Cancer

The success of immunotherapy for cancer treatment is limited by the presence of an immunosuppressive tumor microenvironment (TME); Therefore, identifying novel targets to that can reverse this immunosuppressive TME and enhance immunotherapy efficacy is essential. In this study, enrichment analysis based on publicly available single-cell and bulk RNA sequencing data from gastric cancer patients are conducted, and found that tumor-intrinsic interferon (IFN) plays a central role in TME regulation. The results shows that KDM3A over-expression suppresses the tumor-intrinsic IFN response and inhibits KDM3A, either genomically or pharmacologically, which effectively promotes IFN responses by activating endogenous retroviruses (ERVs). KDM3A ablation reconfigures the dsRNA-MAVS-IFN axis by modulating H3K4me2, enhancing the infiltration and function of CD8 T cells, and simultaneously reducing the presence of regulatory T cells, resulting in a reshaped TME in vivo. In addition, combining anti-PD1 therapy with KDM3A inhibition effectively inhibited tumor growth. In conclusions, this study highlights KDM3A as a potential target for TME remodeling and the enhancement of antitumor immunity in gastric cancer through the regulation of the ERV-MAVS-IFN axis.

Developing a machine learning-based prognosis and immunotherapeutic response signature in colorectal cancer: insights from ferroptosis, fatty acid dynamics, and the tumor microenvironment

Instruction

Colorectal cancer (CRC) poses a challenge to public health and is characterized by a high incidence rate. This study explored the relationship between ferroptosis and fatty acid metabolism in the tumor microenvironment (TME) of patients with CRC to identify how these interactions impact the prognosis and effectiveness of immunotherapy, focusing on patient outcomes and the potential for predicting treatment response.

Methods

Using datasets from multiple cohorts, including The Cancer Genome Atlas (TCGA) and Gene Expression Omnibus (GEO), we conducted an in-depth multi-omics study to uncover the relationship between ferroptosis regulators and fatty acid metabolism in CRC. Through unsupervised clustering, we discovered unique patterns that link ferroptosis and fatty acid metabolism, and further investigated them in the context of immune cell infiltration and pathway analysis. We developed the FeFAMscore, a prognostic model created using a combination of machine learning algorithms, and assessed its predictive power for patient outcomes and responsiveness to treatment. The FeFAMscore signature expression level was confirmed using RT-PCR, and ACAA2 progression in cancer was further verified.

Results

This study revealed significant correlations between ferroptosis regulators and fatty acid metabolism-related genes with respect to tumor progression. Three distinct patient clusters with varied prognoses and immune cell infiltration were identified. The FeFAMscore demonstrated superior prognostic accuracy over existing models, with a C-index of 0.689 in the training cohort and values ranging from 0.648 to 0.720 in four independent validation cohorts. It also responses to immunotherapy and chemotherapy, indicating a sensitive response of special therapies (e.g., anti-PD-1, anti-CTLA4, osimertinib) in high FeFAMscore patients.

Conclusion

Ferroptosis regulators and fatty acid metabolism-related genes not only enhance immune activation, but also contribute to immune escape. Thus, the FeFAMscore, a novel prognostic tool, is promising for predicting both the prognosis and efficacy of immunotherapeutic strategies in patients with CRC.

The Novel ATR Inhibitor M1774 Induces Replication Protein Overexpression and Broad Synergy with DNA-targeted Anticancer Drugs

Ataxia telangiectasia and Rad3-related (ATR) checkpoint kinase inhibitors are in clinical trials. Here we explored the molecular pharmacology and therapeutic combination strategies of the oral ATR inhibitor M1774 (Tuvusertib) with DNA-damaging agents (DDA). As single agent, M1774 suppressed cancer cell viability at nanomolar concentrations, showing greater activity than ceralasertib and berzosertib, but less potency than gartisertib and elimusertib in the small cell lung cancer H146, H82, and DMS114 cell lines. M1774 also efficiently blocked the activation of the ATR-CHK1 checkpoint pathway caused by replication stress induced by TOP1 inhibitors. Combination with non-toxic dose of M1774 enhanced TOP1 inhibitor-induced cancer cell death by enabling unscheduled replication upon replicative damage, thereby increasing genome instability. Tandem mass tag-based quantitative proteomics uncovered that M1774, in the presence of DDA, forces the expression of proteins activating replication (CDC45) and G2-M progression (PLK1 and CCNB1). In particular, the fork protection complex proteins (TIMELESS and TIPIN) were enriched. Low dose of M1774 was found highly synergistic with a broad spectrum of clinical DDAs including TOP1 inhibitors (SN-38/irinotecan, topotecan, exatecan, and exatecan), the TOP2 inhibitor etoposide, cisplatin, the RNA polymerase II inhibitor lurbinectedin, and the PARP inhibitor talazoparib in various models including cancer cell lines, patient-derived organoids, and mouse xenograft models. Furthermore, we demonstrate that M1774 reverses chemoresistance to anticancer DDAs in cancer cells lacking SLFN11 expression, suggesting that SLFN11 can be utilized for patient selection in upcoming clinical trials.

Marine alkaloid rigidin analogues as potential selective inhibitors of SHP1, a new strategy for cancer immunotherapeutics

SHP1 is a protein tyrosine phosphatase playing a central role in immunity, cell growth, development, and survival. The inhibition of SHP1 can help in better prognosis in various disorders like breast and ovarian cancer, melanoma, atherosclerosis, hypoxia, hypoactive immune response, and familial dysautonomia. The currently available inhibitors of SHP1 have the side effect of inhibiting the activity of SHP2, which shares >60% sequence similarity with SHP1 but has distinct biological functions. Thus, there is a need to search for novel specific inhibitors of SHP1. The current study uses a combination of virtual screening and molecular dynamic simulations, followed by PCA and MM-GBSA analysis, to screen about 35000 compounds; to predict that two rigidin analogues can potentially selectively inhibit SHP1 but not SHP2. Our studies demonstrate that these rigidin analogues are more potent at inhibiting SHP1 than the commercially available inhibitor NSC-87877. Further, cross-binding studies with SHP2 exhibited poor binding efficiency and lower stability of the complex, thus indicating a specificity of the rigidin analogues for SHP1, which is crucial in preventing side effects due to the diverse physiological functions of SHP2 in cellular signaling, proliferation, and hematopoiesis. Additionally, SHP1 is essential in mediating the inhibitory signaling in antitumor immune cells like NK and T cells. Hence, the rigidin analogues that inhibit SHP1 will potentiate the anti-tumor immune response by the release of inhibitory function of NK cells, thus driving NK activating response, in addition to their intrinsic anti-tumor function. Thus, SHP1 inhibition is a novel double-blade approach towards anti-cancer immunotherapeutics.Communicated by Ramaswamy H. Sarma.

Treatment strategies and molecular mechanism of radiotherapy combined with immunotherapy in colorectal cancer

Radiotherapy (RT) remodels the tumor immune microenvironment (TIME) and modulates the immune response to indirectly destroy tumor cells, in addition to directly killing tumor cells. RT combined with immunotherapy may significantly enhance the efficacy of RT in colorectal cancer by modulating the microenvironment. However, the molecular mechanisms by which RT acts as an immunomodulator to modulate the immune microenvironment remain unclear. Further, the optimal modalities of RT combined with immunotherapy for the treatment of colorectal cancer, such as the time point of combining RT and immunization, the fractionation pattern and dosage of radiotherapy, and other methods to improve the efficacy, are also being explored parallelly. To address these aspects, in this review, we summarized the mechanisms by which RT modulates TIME and concluded the progress of RT combined with immunization in preclinical and clinical trials. Finally, we discussed heavy ion radiation therapy and the efficacy of prediction markers and other immune combination therapies. Overall, combining RT with immunotherapy to enhance antitumor effects will have a significant clinical implication and will help to facilitate individualized treatment modalities.

Enhancing immunotherapy outcomes by targeted remodeling of the tumor microenvironment via combined cGAS-STING pathway strategies

Immune checkpoint inhibitors (ICIs) represent a groundbreaking advance in the treatment of malignancies such as melanoma and non-small cell lung cancer, showcasing substantial therapeutic benefits. Nonetheless, the efficacy of ICIs is limited to a small subset of patients, primarily benefiting those with "hot" tumors characterized by significant immune infiltration. The challenge of converting "cold" tumors, which exhibit minimal immune activity, into "hot" tumors to enhance their responsiveness to ICIs is a critical and complex area of current research. Central to this endeavor is the activation of the cGAS-STING pathway, a pivotal nexus between innate and adaptive immunity. This pathway's activation promotes the production of type I interferon (IFN) and the recruitment of CD8+ T cells, thereby transforming the tumor microenvironment (TME) from "cold" to "hot". This review comprehensively explores the cGAS-STING pathway's role in reconditioning the TME, detailing the underlying mechanisms of innate and adaptive immunity and highlighting the contributions of various immune cells to tumor immunity. Furthermore, we delve into the latest clinical research on STING agonists and their potential in combination therapies, targeting this pathway. The discussion concludes with an examination of the challenges facing the advancement of promising STING agonists in clinical trials and the pressing issues within the cGAS-STING signaling pathway research.

PREX2 contributes to radiation resistance by inhibiting radiotherapy-induced tumor immunogenicity via cGAS/STING/IFNs pathway in colorectal cancer

BACKGROUND

Colorectal cancer (CRC) lacks established biomarkers or molecular targets for predicting or enhancing radiation response. Phosphatidylinositol-3,4,5-triphosphate-dependent Rac exchange factor 2 (PREX2) exhibits intricate implications in tumorigenesis and progression. Nevertheless, the precise role and underlying mechanisms of PREX2 in CRC radioresistance remain unclear.

METHODS

RNA-seq was employed to identify differentially expressed genes between radioresistant CRC cell lines and their parental counterparts. PREX2 expression was scrutinized using Western blotting, real-time PCR, and immunohistochemistry. The radioresistant role of PREX2 was assessed through in vitro colony formation assay, apoptosis assay, comet assay, and in vivo xenograft tumor models. The mechanism of PREX2 was elucidated using RNA-seq and Western blotting. Finally, a PREX2 small-molecule inhibitor, designated PREX-in1, was utilized to enhance the efficacy of ionizing radiation (IR) therapy in CRC mouse models.

RESULTS

PREX2 emerged as the most significantly upregulated gene in radioresistant CRC cells. It augmented the radioresistant capacity of CRC cells and demonstrated potential as a marker for predicting radioresistance efficacy. Mechanistically, PREX2 facilitated DNA repair by upregulating DNA-PKcs, suppressing radiation-induced immunogenic cell death, and impeding CD8+ T cell infiltration through the cGAS/STING/IFNs pathway. In vivo, the blockade of PREX2 heightened the efficacy of IR therapy.

CONCLUSIONS

PREX2 assumes a pivotal role in CRC radiation resistance by inhibiting the cGAS/STING/IFNs pathway, presenting itself as a potential radioresistant biomarker and therapeutic target for effectively overcoming radioresistance in CRC.

Harnessing the cGAS-STING pathway to potentiate radiation therapy: current approaches and future directions

In this review, we cover the current understanding of how radiation therapy, which uses ionizing radiation to kill cancer cells, mediates an anti-tumor immune response through the cGAS-STING pathway, and how STING agonists might potentiate this. We examine how cGAS-STING signaling mediates the release of inflammatory cytokines in response to nuclear and mitochondrial DNA entering the cytoplasm. The significance of this in the context of cancer is explored, such as in response to cell-damaging therapies and genomic instability. The contribution of the immune and non-immune cells in the tumor microenvironment is considered. This review also discusses the burgeoning understanding of STING signaling that is independent of inflammatory cytokine release and the various mechanisms by which cancer cells can evade STING signaling. We review the available data on how ionizing radiation stimulates cGAS-STING signaling as well as how STING agonists may potentiate the anti-tumor immune response induced by ionizing radiation. There is also discussion of how novel radiation modalities may affect cGAS-STING signaling. We conclude with a discussion of ongoing and planned clinical trials combining radiation therapy with STING agonists, and provide insights to consider when planning future clinical trials combining these treatments.

The ATR inhibition by Elimusertib enhances the radiosensitivity of MDA-MB-231 triple negative breast cancer in vitro

PURPOSE

DNA damage response (DDR) is the principal mechanism regulating genomic stability and cell cycle checkpoint activation by coordinating DNA repair and apoptotic pathways. Ataxia telangiectasia and Rad3-related protein (ATR) play a significant role in the DDR due to its capability to detect a wide spectrum of DNA damage. Therefore, targeting DDR, specifically ATR, is a promising therapeutic strategy in cancer treatment. Furthermore, the inhibition of ATR sensitizes cancer cells to radiotherapy (RT). Herein, we, for the first time, investigated the synergistic effects of Elimusertib (BAY-1895344) as a highly potent selective ATR inhibitor with RT combination in triple-negative breast cancer (TNBC), in vitro.

METHODS

MDA-MB-231 TNBC cells were firstly treated with different concentrations of Elimusertib for 24 h and then exposed to 4 and 8 Gy of X-ray irradiation. After post-irradiation for 72 h, WST-1, Annexin V, cell cycle, acridine orange/propidium iodide, mitochondria staining and western blot analysis were conducted.

RESULTS

Our findings showed that 4 Gy irradiation and lower doses (especially 2 and 4 nM) of Elimusertib combination exerted a considerable anticancer activity at 72 h post-irradiation through apoptotic cell death, marked nuclear and mitochondrial damages and the suppression of ATR-Chk1 based DDR mechanism.

CONCLUSION

ATR inhibition by Elimusertib in combination with RT may be a promising new treatment strategy in the treatment of TNBC. However, further experiments should be performed to elucidate the underlying molecular mechanisms of the therapeutic efficacy of this combination treatment and its association with DNS repair mechanisms in TNBC, in vitro and in vivo.

Targeting ATR Pathway in Solid Tumors: Evidence of Improving Therapeutic Outcomes

The DNA damage response (DDR) system is a complicated network of signaling pathways that detects and repairs DNA damage or induces apoptosis. Critical regulators of the DDR network include the DNA damage kinases ataxia telangiectasia mutated Rad3-related kinase (ATR) and ataxia-telangiectasia mutated (ATM). The ATR pathway coordinates processes such as replication stress response, stabilization of replication forks, cell cycle arrest, and DNA repair. ATR inhibition disrupts these functions, causing a reduction of DNA repair, accumulation of DNA damage, replication fork collapse, inappropriate mitotic entry, and mitotic catastrophe. Recent data have shown that the inhibition of ATR can lead to synthetic lethality in ATM-deficient malignancies. In addition, ATR inhibition plays a significant role in the activation of the immune system by increasing the tumor mutational burden and neoantigen load as well as by triggering the accumulation of cytosolic DNA and subsequently inducing the cGAS-STING pathway and the type I IFN response. Taken together, we review stimulating data showing that ATR kinase inhibition can alter the DDR network, the immune system, and their interplay and, therefore, potentially provide a novel strategy to improve the efficacy of antitumor therapy, using ATR inhibitors as monotherapy or in combination with genotoxic drugs and/or immunomodulators.

The ATR inhibitor berzosertib acts as a radio- and chemosensitizer in head and neck squamous cell carcinoma cell lines

Alterations in the DNA damage response play a crucial role in radio- and chemoresistance of neoplastic cells. Activation of the Ataxia telangiectasia and Rad3-related (ATR) pathway is an important DNA damage response mechanism in head and neck squamous cell carcinoma (HNSCC). Berzosertib, a selective ATR inhibitor, shows promising radio- and chemosensitizing effects in preclinical studies and is well tolerated in clinical studies. The aim of this study was to elucidate the effect of berzosertib treatment in combination with radiation and cisplatin in HNSCC. The HNSCC cell lines Cal-27 and FaDu were treated with berzosertib alone and in combination with radiation or cisplatin. Cell viability and clonogenic survival were evaluated. The effect of combination treatment was evaluated with the SynergyFinder or combination index. Apoptosis was assessed via measurement of caspase 3/7 activation and migration was evaluated using a wound healing assay. Berzosertib treatment decreased cell viability in a dose-dependent manner and increased apoptosis. The IC50 of berzosertib treatment after 72 h was 0.25-0.29 µM. Combination with irradiation treatment led to a synergistic increase in radiosensitivity and a synergistic or additive decrease in colony formation. The combination of berzosertib and cisplatin decreased cell viability in a synergistic manner. Additionally, berzosertib inhibited migration at high doses. Berzosertib displays a cytotoxic effect in HNSCC at clinically relevant doses. Further evaluation of combination treatment with irradiation and cisplatin is strongly recommended in HNSCC patients as it may hold the potential to overcome treatment resistance, reduce treatment doses and thus mitigate adverse events.

Efficacy and safety of subsequent radiotherapy in patients with advanced-stage hepatocellular carcinoma treated with immune checkpoint inhibitors

Background

The development of immunotherapy resistance is associated with a poor prognosis in patients diagnosed with hepatocellular carcinoma (HCC) who are undergoing treatment with immune checkpoint inhibitors (ICI). This study aimed to evaluate the efficacy and safety of subsequent radiotherapy (RT) for patients with advanced-stage HCC who had lesion enlargement or new lesions (NLs) during ICI therapy.

Methods

This retrospective observational study enrolled 36 patients with advanced-stage HCC who underwent subsequent RT for lesion enlargement or NLs during ICI therapy from two centers. The primary endpoints were progression-free survival (PFS) and overall survival (OS). The secondary endpoints included objective response rate (ORR), disease control rate (DCR), 1- and 2-year local control (LC) rates, in-field PFS (IFPFS), out-field PFS (OFPFS), and safety.

Results

The median follow-up time was 15.3 months. The median PFS was 7.4 months [95% confidence interval (CI): 3.1-11.7 months], and the median OS was 18.8 months (95% CI: 17.1-20.5 months). ORR and DCR were 38.9% and 72.2%, respectively. In addition, the median IFPFS was 17.8 months (95% CI: 11.5-24.2 months), median OFPFS was 7.9 months (95% CI: 3.4-12.5 months), and estimated 1- and 2-year LC rates were 67.1% and 31.9%, respectively. The most common treatment-related adverse events (all grades) were diarrhea (33.3%), rash (30.6%), and malaise (27.8%); a total of 14 (38.9%) patients developed grade 3-4 AEs.

Conclusions

Subsequent RT showed reliable antitumor effects and an acceptable safety profile in patients with advanced-stage HCC who had unsatisfactory response to ICI therapy; therefore, it could serve as an optional salvage strategy.

Inhibitors of phosphoinositide 3-kinase (PI3K) and phosphoinositide 3-kinase-related protein kinase family (PIKK)

Phosphoinositide 3-kinases (PI3K) and phosphoinositide 3-kinase-related protein kinases (PIKK) are two structurally related families of kinases that play vital roles in cell growth and DNA damage repair. Dysfunction of PIKK members and aberrant stimulation of the PI3K/AKT/mTOR signalling pathway are linked to a plethora of diseases including cancer. In recent decades, numerous inhibitors related to the PI3K/AKT/mTOR signalling have made great strides in cancer treatment, like copanlisib and sirolimus. Notably, most of the PIKK inhibitors (such as VX-970 and M3814) related to DNA damage response have also shown good efficacy in clinical trials. However, these drugs still require a suitable combination therapy to overcome drug resistance or improve antitumor activity. Based on the aforementioned facts, we summarised the efficacy of PIKK, PI3K, and AKT inhibitors in the therapy of human malignancies and the resistance mechanisms of targeted therapy, in order to provide deeper insights into cancer treatment.

Role of non-canonical post-translational modifications in gastrointestinal tumors

Post-translational modifications (PTMs) of proteins contribute to the occurrence and development of tumors. Previous studies have suggested that canonical PTMs such as ubiquitination, glycosylation, and phosphorylation are closely implicated in different aspects of gastrointestinal tumors. Recently, emerging evidence showed that non-canonical PTMs play an essential role in the carcinogenesis, metastasis and treatment of gastrointestinal tumors. Therefore, we summarized recent advances in sumoylation, neddylation, isoprenylation, succinylation and other non-canonical PTMs in gastrointestinal tumors, which comprehensively describe the mechanisms and functions of non-classical PTMs in gastrointestinal tumors. It is anticipated that targeting specific PTMs could benefit the treatment as well as improve the prognosis of gastrointestinal tumors.

The emerging roles of SUMOylation in the tumor microenvironment and therapeutic implications

Tumor initiation, progression, and response to therapies depend to a great extent on interactions between malignant cells and the tumor microenvironment (TME), which denotes the cancerous/non-cancerous cells, cytokines, chemokines, and various other factors around tumors. Cancer cells as well as stroma cells can not only obtain adaption to the TME but also sculpt their microenvironment through a series of signaling pathways. The post-translational modification (PTM) of eukaryotic cells by small ubiquitin-related modifier (SUMO) proteins is now recognized as a key flexible pathway. Proteins involved in tumorigenesis guiding several biological processes including chromatin organization, DNA repair, transcription, protein trafficking, and signal conduction rely on SUMOylation. The purpose of this review is to explore the role that SUMOylation plays in the TME formation and reprogramming, emphasize the importance of targeting SUMOylation to intervene in the TME and discuss the potential of SUMOylation inhibitors (SUMOi) in ameliorating tumor prognosis.

Immunogenic cell death after combined treatment with radiation and ATR inhibitors is dually regulated by apoptotic caspases

Introduction

Inhibitors of the ATR kinase act as radiosensitizers through abrogating the G2 checkpoint and reducing DNA repair. Recent studies suggest that ATR inhibitors can also increase radiation-induced antitumor immunity, but the underlying immunomodulating mechanisms remain poorly understood. Moreover, it is poorly known how such immune effects relate to different death pathways such as caspase-dependent apoptosis. Here we address whether ATR inhibition in combination with irradiation may increase the presentation of hallmark factors of immunogenic cell death (ICD), and to what extent caspase activation regulates this response.

Methods

Human lung cancer and osteosarcoma cell lines (SW900, H1975, H460, U2OS) were treated with X-rays and ATR inhibitors (VE822; AZD6738) in the absence and presence of a pan-caspase inhibitor. The ICD hallmarks HMGB1 release, ATP secretion and calreticulin surface-presentation were assessed by immunoblotting of growth medium, the CellTiter-Glo assay and an optimized live-cell flow cytometry assay, respectively. To obtain accurate measurement of small differences in the calreticulin signal by flow cytometry, we included normalization to a barcoded control sample.

Results

Extracellular release of HMGB1 was increased in all the cell lines at 72 hours after the combined treatment with radiation and ATR inhibitors, relative to mock treatment or cells treated with radiation alone. The HMGB1 release correlated largely - but not strictly - with loss of plasma membrane integrity, and was suppressed by addition of the caspase inhibitor. However, one cell line showed HMGB1 release despite caspase inhibition, and in this cell line caspase inhibition induced pMLKL, a marker for necroptosis. ATP secretion occurred already at 48 hours after the co-treatment and did clearly not correlate with loss of plasma membrane integrity. Addition of pan-caspase inhibition further increased the ATP secretion. Surface-presentation of calreticulin was increased at 24-72 hours after irradiation, but not further increased by either ATR or caspase inhibition.

Conclusion

These results show that ATR inhibition can increase the presentation of two out of three ICD hallmark factors from irradiated human cancer cells. Moreover, caspase activation distinctly affects each of the hallmark factors, and therefore likely plays a dual role in tumor immunogenicity by promoting both immunostimulatory and -suppressive effects.

The mechanism and clinical application of DNA damage repair inhibitors combined with immune checkpoint inhibitors in the treatment of urologic cancer

Urologic cancers such as kidney, bladder, prostate, and uroepithelial cancers have recently become a considerable global health burden, and the response to immunotherapy is limited due to immune escape and immune resistance. Therefore, it is crucial to find appropriate and effective combination therapies to improve the sensitivity of patients to immunotherapy. DNA damage repair inhibitors can enhance the immunogenicity of tumor cells by increasing tumor mutational burden and neoantigen expression, activating immune-related signaling pathways, regulating PD-L1 expression, and reversing the immunosuppressive tumor microenvironment to activate the immune system and enhance the efficacy of immunotherapy. Based on promising experimental results from preclinical studies, many clinical trials combining DNA damage repair inhibitors (e.g., PARP inhibitors and ATR inhibitors) with immune checkpoint inhibitors (e.g., PD-1/PD-L1 inhibitors) are underway in patients with urologic cancers. Results from several clinical trials have shown that the combination of DNA damage repair inhibitors with immune checkpoint inhibitors can improve objective rates, progression-free survival, and overall survival (OS) in patients with urologic tumors, especially in patients with defective DNA damage repair genes or a high mutational load. In this review, we present the results of preclinical and clinical trials of different DNA damage repair inhibitors in combination with immune checkpoint inhibitors in urologic cancers and summarize the potential mechanism of action of the combination therapy. Finally, we also discuss the challenges of dose toxicity, biomarker selection, drug tolerance, drug interactions in the treatment of urologic tumors with this combination therapy and look into the future direction of this combination therapy.

Redox Signaling Modulates Activity of Immune Checkpoint Inhibitors in Cancer Patients

Although immunotherapy is already a staple of cancer care, many patients may not benefit from these cutting-edge treatments. A crucial field of research now focuses on figuring out how to improve treatment efficacy and assess the resistance mechanisms underlying this uneven response. For a good response, immune-based treatments, in particular immune checkpoint inhibitors, rely on a strong infiltration of T cells into the tumour microenvironment. The severe metabolic environment that immune cells must endure can drastically reduce effector activity. These immune dysregulation-related tumour-mediated perturbations include oxidative stress, which can encourage lipid peroxidation, ER stress, and T regulatory cells dysfunction. In this review, we have made an effort to characterize the status of immunological checkpoints, the degree of oxidative stress, and the part that latter plays in determining the therapeutic impact of immunological check point inhibitors in different neoplastic diseases. In the second section of the review, we will make an effort to assess new therapeutic possibilities that, by affecting redox signalling, may modify the effectiveness of immunological treatment.