Co-Inhibition of the DNA Damage Response and CHK1 Enhances Apoptosis of Neuroblastoma Cells

DNA damage response deficiency enhances neuroblastoma progression and sensitivity to combination PARP and ATR inhibition

Sequencing of neuroblastoma (NB) tumors has revealed genetic alterations in genes involved in DNA damage response (DDR) pathways. However, roles for specific alterations of DDR genes in pediatric solid tumors remain poorly understood. To address this, mutations in the DDR pathway including Brca2, Atm, and Palb2 were incorporated into an established zebrafish MYCN transgenic model (Tg(dbh:EGFP-MYCN)). These mutations enhance NB formation and metastasis and result in upregulation of cell-cycle checkpoint and DNA damage repair signatures, revealing molecular vulnerabilities in DDR-deficient NB. DDR gene knockdown in zebrafish and human NB cells increases sensitivity to the poly(ADP-ribose) polymerase (PARP) inhibitor olaparib, and this effect is enhanced by inhibition of the ataxia telangiectasia and rad3-related (ATR) kinase. This work provides in vivo evidence demonstrating that alterations in certain DDR-pathway genes promote aggressive NB and supports combination PARP + ATR inhibitor therapy for NB patients with tumors harboring specific genetic alterations in DDR.

Differential roles of IL-17B and IL-17RB in colorectal cancer: Correlation with immune infiltration and prognosis

BACKGROUND

The aim of the research is to investigate correlation of immune infiltration between IL-17B and IL-17RB in colorectal cancer (CRC), then provide an experimental basis for clinical diagnostic marker screening of CRC.

METHODS

Gene expression levels were assessed via TIMER and GEPIA databases, protein expression through the Human Protein Atlas (HPA), clinicopathological correlations and prognosis via UALCAN and KM-Plotter, respectively. Mutation analysis was conducted using cBioPortal, immune cell infiltration via TIMER, and hub genes were identified through protein-protein interaction (PPI) networks. Biological functions and pathways were elucidated with Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis. Finally, the expression of IL-17B, IL-17RB, and associated inflammatory cells in CRC were analyzed using immunohistochemical staining and special staining technique.

RESULTS

Bioinformatics analysis showed that IL-17B gene and protein expression levels decreased, while IL-17RB expression increased in CRC. IL-17B expression was affected by gender, body weight, histology, lymph node status, and tumour grade. Overexpression of IL-17B was negatively correlated with progression-free survival in CRC. IL-17B is involved in phosphatidylinositol 3-kinase/AKT signaling, vascular development, and other processes. IL-17B is associated with mitochondrial gene expression, regulation of mRNA metabolism, amino acid metabolism and other processes, as well as phosphatidylinositol-binding and liganding. Inositol 3-kinase/AKT signalling and vascular development. IL-17B was negatively correlated with mitochondrial gene expression, regulation of mRNA metabolism, amino acid metabolism and other processes as well as with molecular functions such as phosphatidylinositol binding and ligase activity. IL-17RB expression was correlated with the clinicopathological features described above and decreased with tumour progression. High levels of IL-17RB were associated with improved overall survival and immune cell infiltration. The key genes of IL-17RB are mainly involved in DNA damage, metabolism, checkpoint signaling and regulation of replication. Immunohistochemical staining results showed that the expression of IL-17B and IL-17RB reduced in CRC, compared to normal colon tissue (p < 0.05). IL-17B was positively correlated with CD4+ T lymphocyte and mast cell infiltration. IL-17RB was positively correlated with CD4+ T lymphocyte infiltration and negatively correlated with CD20+ B lymphocyte infiltration.

CONCLUSION

The expression of IL-17RB in CRC decreased with increasing tumour stage, and high levels of IL-17RB predicted a better prognosis, suggesting that its decreased expression was associated with disease progression. Therefore, IL-17RB may be a biomarker for assessing the prognosis of CRC. Meanwhile, IL-17B was positively correlated with CD4+ T lymphocyte and mast cell infiltration, and its overexpression was negatively correlated with recurrence-free survival, IL-17B and IL-17RB may affect CRC through different pathway mechanisms.

PF-477736 modulates vascular smooth muscle cells phenotypic transition through Chk1/p53/CD44 pathway

INTRODUCTION

The phenotypic transition of vascular smooth muscle cells (VSMCs) from a quiescent, contractile type to a secretory phenotype with high proliferation and mobility is a key event in vascular remodeling. PF-477736 is an ATP-competitive inhibitor of Chk1 which induces the accumulation of DNA damage by increasing the level of replicative stress, and ultimately inhibiting cell proliferation or causing cell death. Although this compound has been utilized as an anti-tumor drug, its role in vascular remodeling remains unclear.

METHODS

In vitro, Human aortic smooth muscle cell line (HAVSMC) and primary rat aortic smooth muscle cells were used to establish phenotype transformation model with PDGF-bb; Western blot was used to detect the expression of VSMCs phenotype marker α-SMA, Vimentin; MTT and EdU assays were used to evaluate the proliferation ability of VSMCs; wound healing assay was used to evaluate the migration ability of VSMCs. In vivo, we established ballon injury of carotid artery in rats, and the function of the PF-477736 was evaluated by several histological stainings.

RESULTS

The results exhibit that PF-477736 effectively inhibited VSMCs phenotypic transition, resulting in G1/S phase arrest and decreased proliferation and migration ability of VSMCs. Furthermore, while PDGF-bb down-regulated p53 protein and up-regulated CD44 expression, PF-477736 significantly countered these effects. Pretreatment of VSMCs with p53 siRNA blocked the effect of PF-477736, up-regulated the expression of CD44, and promoted VSMCs' proliferation and migration. Conversely, CD44 silencing through siRNA mitigated the phenotypic transition of VSMCs. In addition, the H&E, Masson' staining and the immunohistochemistry of PCNA, p53 and CD44 showed that PF-477736 substantially inhibits vascular remodeling in the balloon injury model.

CONCLUSION

Our findings show that PF-477736 exerts anti-vascular remodeling effect by inhibiting phenotypic transition through the Chk1/p53/CD44 pathway in VSMCs, providing novel therapeutic strategies for preventing and treating vascular remodeling.

RBM17 Promotes the Chemoresistance of Oral Squamous Cancer Cells Through Checkpoint Kinase 1

Oral squamous cell carcinoma (OSCC) is one of the most common types of cancer in the head and neck region. In advanced stages of OSCC, chemotherapy is commonly used for treatment, despite some cancer cells having low sensitivity to anticancer drugs. We focused on RBM17/SPF45 as an essential drug-sensitizing factor in the context of malignant cells acquiring chemoresistance. Here, we demonstrate how RBM17 affects anticancer drug resistance in OSCC and we suggest the possible mechanism underlying its effects. After exposing oral cancer cell lines to fluorouracil (5-FU) and cisplatin, but not paclitaxel, the gene and protein expression of RBM17 increased. We found that siRNA-mediated RBM17-knockdown of the cell lines gained a significantly higher sensitivity to 5-FU, which was remarkably followed by a decrease in the expression of checkpoint kinase 1 (CHEK1) protein, whereas treatment with a CHEK1 inhibitor did not affect RBM17 protein expression in the oral cancer cell lines. These results indicate that RBM17 is a factor involved in the development of resistance to cytotoxic chemotherapy. We propose the underlying mechanism that RBM17 promotes CHEK1 protein expression in the ATM/ATR pathway, triggering the development of chemoresistance in cancer cells.

Comparative effects of arsenic trioxide and chemotherapy on Chk1 and CDC25 gene expression in gastric cancer cells AGS and MKN45: a potential therapeutic strategy

BACKGROUND

Gastric cancer (GC) remains a significant global health burden, particularly in East Asia, where it is a leading cause of cancer-related morbidity and mortality. Despite advancements in chemotherapy, the development of chemoresistance continues to undermine the efficacy of standard treatments such as Docetaxel and Oxaliplatin. Arsenic trioxide (ATO) has emerged as a potential therapeutic agent capable of overcoming resistance by targeting DNA repair mechanisms, particularly through the downregulation of Checkpoint Kinase 1 (Chk1). This study investigates the cytotoxic effects of ATO and its capacity to enhance chemotherapy efficacy in GC cells.

METHODS

AGS and MKN-45 gastric cancer cell lines were exposed to ATO, Docetaxel, Oxaliplatin, and their combinations. Cell viability was assessed via the MTT assay, while Chk1 and CDC25 expressions at the mRNA and protein levels was analyzed using real-time PCR and Western blotting. Statistical analyses were performed using ANOVA and Tukey's post hoc test.

RESULTS

The MTT assay revealed significant dose- and time-dependent reductions in cell viability, with combination treatments achieving the most pronounced effects. The greatest cytotoxicity was observed with 4 µM ATO combined with 2500 µM Docetaxel or 100 µM Oxaliplatin, showing a high level of statistical significance (p < 0.0001). Additionally, ATO monotherapy significantly downregulated Chk1 and CDC25 expressions (p < 0.05), while its combination with chemotherapeutic agents further enhanced Chk1 and CDC25 suppressions, with ATO-Docetaxel demonstrating the most pronounced effect (p < 0.01).

CONCLUSIONS

These findings highlight ATO's potential to sensitize GC cells to chemotherapy by impairing DNA repair mechanisms and inducing synergistic cytotoxicity. ATO holds promise as an adjuvant therapeutic agent for overcoming chemoresistance in gastric cancer.

Correlation Between the Expression of DNA Damage Repair Protein OGG1 and Ubiquitination Pathway Protein STUB1 in Pediatric Neuroblastoma

BACKGROUND

Neuroblastoma, a pediatric malignancy, is significantly influenced by genetic factors. Prior research indicates that the OGG1 rs1052133 G > C polymorphism correlates with a decreased risk of neuroblastoma.

METHODS

We analyzed 57 neuroblastoma and 21 adrenal samples, using immunohistochemistry to measure OGG1 and STUB1 expression levels. We conducted a survival analysis to explore relationship between the expressions and neuroblastoma prognosis.

RESULTS

Notably higher OGG1 expression and significantly lower STUB1 expression in neuroblastoma. OGG1 levels were significantly correlated with patient age, tumor location, histological grade, Shimada classification, INSS stage, and risk category. A negative association was observed between OGG1 and STUB1 expressions. Higher OGG1 expression was linked to reduced PFS and OS. Lower STUB1 expression was associated with unfavorable PFS. Additionally, OGG1 expression and risk category emerged as independent predictors of prognosis.

CONCLUSION

OGG1 potentially functions as an oncogene in NB, with its activity possibly modulated by STUB1 through the ubiquitination pathway.

Enhancing Standard of Care Chemotherapy Efficacy Using DNA-Dependent Protein Kinase (DNA-PK) Inhibition in Preclinical Models of Ewing Sarcoma

Disruption of DNA damage repair via impaired homologous recombination is characteristic of Ewing sarcoma (EWS) cells. We hypothesize that this disruption results in increased reliance on nonhomologous end joining to repair DNA damage. In this study, we investigated if pharmacologic inhibition of the enzyme responsible for nonhomologous end joining, the DNA-PK holoenzyme, alters the response of EWS cells to genotoxic standard of care chemotherapy. We used analyses of cell viability and proliferation to investigate the effects of clinical DNA-PK inhibitors (DNA-PKi) in combination with six therapeutic or experimental agents for EWS. We performed calculations of synergy using the Loewe additivity model. Immunoblotting evaluated treatment effects on DNA-PK, DNA damage, and apoptosis. Flow cytometric analyses evaluated effects on cell cycle and fate. We used orthotopic xenograft models to interrogate tolerability, drug mechanism, and efficacy in vivo. DNA-PKi demonstrated on-target activity, reducing phosphorylated DNA-PK levels in EWS cells. DNA-PKi sensitized EWS cell lines to agents that function as topoisomerase 2 (TOP2) poisons and enhanced the DNA damage induced by TOP2 poisons. Nanomolar concentrations of single-agent TOP2 poisons induced G2M arrest and little apoptotic response while adding DNA-PKi-mediated apoptosis. In vivo, the combination of AZD7648 and etoposide had limited tolerability but resulted in enhanced DNA damage, apoptosis, and EWS tumor shrinkage. The combination of DNA-PKi with standard of care TOP2 poisons in EWS models is synergistic, enhances DNA damage and cell death, and may form the basis of a promising future therapeutic strategy for EWS.

DNA Ligase 4 Contributes to Cell Proliferation against DNA-PK Inhibition in MYCN-Amplified Neuroblastoma IMR32 Cells

Identifying the vulnerability of altered DNA repair machinery that displays synthetic lethality with MYCN amplification is a therapeutic rationale in unfavourable neuroblastoma. However, none of the inhibitors for DNA repair proteins are established as standard therapy in neuroblastoma. Here, we investigated whether DNA-PK inhibitor (DNA-PKi) could inhibit the proliferation of spheroids derived from neuroblastomas of MYCN transgenic mice and MYCN-amplified neuroblastoma cell lines. DNA-PKi exhibited an inhibitory effect on the proliferation of MYCN-driven neuroblastoma spheroids, whereas variable sensitivity was observed in those cell lines. Among them, the accelerated proliferation of IMR32 cells was dependent on DNA ligase 4 (LIG4), which comprises the canonical non-homologous end-joining pathway of DNA repair. Notably, LIG4 was identified as one of the worst prognostic factors in patients with MYCN-amplified neuroblastomas. It may play complementary roles in DNA-PK deficiency, suggesting the therapeutic potential of LIG4 inhibition in combination with DNA-PKi for MYCN-amplified neuroblastomas to overcome resistance to multimodal therapy.

Dual inhibition of CHK1/FLT3 enhances cytotoxicity and overcomes adaptive and acquired resistance in FLT3-ITD acute myeloid leukemia

FLT3 inhibitors (FLT3i) are widely used for the treatment of acute myeloid leukemia (AML), but adaptive and acquired resistance remains a primary challenge. Inhibitors simultaneously blocking adaptive and acquired resistance are highly demanded. Here, we observed the potential of CHK1 inhibitors to synergistically improve the therapeutic effect of FLT3i in FLT3-mutated AML cells. Notably, the combination overcame adaptive resistance. The simultaneous targeting of FLT3 and CHK1 kinases may overcome acquired and adaptive resistance. A dual FLT3/CHK1 inhibitor 30 with a good oral PK profile was identified. Mechanistic studies indicated that 30 inhibited FLT3 and CHK1, downregulated the c-Myc pathway and further activated the p53 pathway. Functional studies showed that 30 was more selective against cells with various FLT3 mutants, overcame adaptive resistance in vitro, and effectively inhibited resistant FLT3-ITD AML in vivo. Moreover, 30 showed favorable druggability without significant blood toxicity or myelosuppression and exhibited a good oral PK profile with a T_1/2 over 12 h in beagles. These findings support the targeting of FLT3 and CHK1 as a novel strategy for overcoming adaptive and acquired resistance to FLT3i therapy in AML and suggest 30 as a potential clinical candidate.

The Combination of ATM and Chk1 Inhibitors Induces Synthetic Lethality in Colorectal Cancer Cells

Genetic abnormalities induce the DNA damage response (DDR), which enables DNA repair at cell cycle checkpoints. Although the DDR is thought to function in preventing the onset and progression of cancer, DDR-related proteins are also thought to contribute to tumorigenesis, tumor progression, and drug resistance by preventing irreparable genomic abnormalities from inducing cell death. In the present study, the combination of ataxia telangiectasia-mutated serine/threonine kinase (ATM) and checkpoint kinase 1 (Chk1) inhibition exhibited synergistic antitumor effects and induced synergistic lethality in colorectal cancer cells at a low dose. The ATM and Chk1 inhibitors synergistically promoted the activation of cyclin-dependent kinase 1 by decreasing the phosphorylation levels of T14 and Y15. Furthermore, the combined treatment increased the number of sub-G1-stage cells, phospho-histone H2A.X-positive cells, and TdT-mediated dUTP nick-end labeling-positive cells among colon cancer cells, suggesting that the therapy induces apoptosis. Finally, the combined treatment exhibited a robust antitumor activity in syngeneic tumor model mice. These findings should contribute to the development of new treatments for colorectal cancer that directly exploit the genomic instability of cancer cells.

Synthetic Heterocyclic Derivatives as Kinase Inhibitors Tested for the Treatment of Neuroblastoma

In the last few years, small molecules endowed with different heterocyclic scaffolds have been developed as kinase inhibitors. Some of them are being tested at preclinical or clinical levels for the potential treatment of neuroblastoma (NB). This disease is the most common extracranial solid tumor in childhood and is responsible for 10% to 15% of pediatric cancer deaths. Despite the availability of some treatments, including the use of very toxic cytotoxic chemotherapeutic agents, high-risk (HR)-NB patients still have a poor prognosis and a survival rate below 50%. For these reasons, new pharmacological options are urgently needed. This review focuses on synthetic heterocyclic compounds published in the last five years, which showed at least some activity on this severe disease and act as kinase inhibitors. The specific mechanism of action, selectivity, and biological activity of these drug candidates are described, when established. Moreover, the most remarkable clinical trials are reported. Importantly, kinase inhibitors approved for other diseases have shown to be active and endowed with lower toxicity compared to conventional cytotoxic agents. The data collected in this article can be particularly useful for the researchers working in this area.

FGFR2 loss sensitizes MYCN-amplified neuroblastoma CHP134 cells to CHK1 inhibitor-induced apoptosis

Checkpoint kinase 1 (CHK1) plays a key role in genome surveillance and integrity throughout the cell cycle. Selective inhibitors of CHK1 (CHK1i) are undergoing clinical evaluation for various human malignancies, including neuroblastoma. In this study, one CHK1i‐sensitive neuroblastoma cell line, CHP134, was investigated, which characteristically carries MYCN amplification and a chromosome deletion within the 10q region. Among several cancer‐related genes in the chromosome 10q region, mRNA expression of fibroblast growth factor receptor 2 (FGFR2) was altered in CHP134 cells and associated with an unfavorable prognosis of patients with neuroblastoma. Induced expression of FGFR2 in CHP134 cells reactivated downstream MEK/ERK signaling and resulted in cells resistant to CHK1i‐mediated cell growth inhibition. Consistently, the MEK1/2 inhibitor, trametinib, potentiated CHK1 inhibitor–mediated cell death in these cells. These results suggested that FGFR2 loss might be prone to highly effective CHK1i treatment. In conclusion, extreme cellular dependency of ERK activation may imply a possible application for the MEK1/2 inhibitor, either as a single inhibitor or in combination with CHK1i in MYCN‐amplified neuroblastomas.

Acceleration or Brakes: Which Is Rational for Cell Cycle-Targeting Neuroblastoma Therapy?

Unrestrained proliferation is a common feature of malignant neoplasms. Targeting the cell cycle is a therapeutic strategy to prevent unlimited cell division. Recently developed rationales for these selective inhibitors can be subdivided into two categories with antithetical functionality. One applies a “brake” to the cell cycle to halt cell proliferation, such as with inhibitors of cell cycle kinases. The other “accelerates” the cell cycle to initiate replication/mitotic catastrophe, such as with inhibitors of cell cycle checkpoint kinases. The fate of cell cycle progression or arrest is tightly regulated by the presence of tolerable or excessive DNA damage, respectively. This suggests that there is compatibility between inhibitors of DNA repair kinases, such as PARP inhibitors, and inhibitors of cell cycle checkpoint kinases. In the present review, we explore alterations to the cell cycle that are concomitant with altered DNA damage repair machinery in unfavorable neuroblastomas, with respect to their unique genomic and molecular features. We highlight the vulnerabilities of these alterations that are attributable to the features of each. Based on the assessment, we offer possible therapeutic approaches for personalized medicine, which are seemingly antithetical, but both are promising strategies for targeting the altered cell cycle in unfavorable neuroblastomas.

Heterogeneities in Cell Cycle Checkpoint Activation Following Doxorubicin Treatment Reveal Targetable Vulnerabilities in TP53 Mutated Ultra High-Risk Neuroblastoma Cell Lines

Most chemotherapeutics target DNA integrity and thereby trigger tumour cell death through activation of DNA damage responses that are tightly coupled to the cell cycle. Disturbances in cell cycle regulation can therefore lead to treatment resistance. Here, a comprehensive analysis of cell cycle checkpoint activation following doxorubicin (doxo) treatment was performed using flow cytometry, immunofluorescence and live-cell imaging in a panel of TP53 mutated ultra high-risk neuroblastoma (NB) cell lines, SK-N-DZ, Kelly, SK-N-AS, SK-N-FI, and BE(2)-C. Following treatment, a dose-dependent accumulation in either S- and/or G2/M-phase was observed. This coincided with a heterogeneous increase of cell cycle checkpoint proteins, i.e., phos-ATM, phos-CHK1, phos-CHK2, Wee1, p21^Cip1/Waf1, and p27^Kip among the cell lines. Combination treatment with doxo and a small-molecule inhibitor of ATM showed a delay in regrowth in SK-N-DZ, of CHK1 in BE(2)-C, of Wee1 in SK-N-FI and BE(2)-C, and of p21 in Kelly and BE(2)-C. Further investigation revealed, in all tested cell lines, a subset of cells arrested in mitosis, indicating independence on the intra-S- and/or G2/M-checkpoints. Taken together, we mapped distinct cell cycle checkpoints in ultra high-risk NB cell lines and identified checkpoint dependent and independent druggable targets.

Diarylheptanoid analogues from the rhizomes of Zingiber officinale and their anti-tumour activity

Diarylheptanoid analogues from the rhizomes of Zingiber officinale and their anti-tumour activity.

CEP131 Abrogates CHK1 Inhibitor-Induced Replication Defects and Is Associated with Unfavorable Outcome in Neuroblastoma

Checkpoint kinase 1 (CHK1) plays a key role in genome surveillance and integrity throughout the cell cycle. Selective inhibitors of CHK1 (CHK1i) are undergoing clinical evaluation for various human malignancies, including neuroblastoma. Recently, we reported that CHK1i, PF-477736, induced a p53-mediated DNA damage response. As a result, the cancer cells were able to repair DNA damage and became less sensitive to CHK1i. In this study, we discovered that PF-477736 increased expression of MDM2 oncogene along with CHK1i-induced replication defects in neuroblastoma NB-39-nu cells. A mass spectrometry analysis of protein binding to MDM2 in the presence of CHK1i identified the centrosome-associated family protein 131 (CEP131), which was correlated with unfavorable prognosis of neuroblastoma patients. We revealed that MDM2 was associated with CEP131 protein degradation, whereas overexpression of CEP131 accelerated neuroblastoma cell growth and exhibited resistance to CHK1i-induced replication defects. Thus, these findings may provide a future therapeutic strategy against centrosome-associated oncogenes involving CEP131 as a target in neuroblastoma.

Hypoxia Predicts Poor Prognosis in Neuroblastoma Patients and Associates with Biological Mechanisms Involved in Telomerase Activation and Tumor Microenvironment Reprogramming

The biological and clinical heterogeneity of neuroblastoma (NB) demands novel biomarkers and therapeutic targets in order to drive the most appropriate treatment for each patient. Hypoxia is a condition of low-oxygen tension occurring in poorly vascularized tumor tissues. In this study, we aimed to assess the role of hypoxia in the pathogenesis of NB and at developing a new clinically relevant hypoxia-based predictor of outcome. We analyzed the gene expression profiles of 1882 untreated NB primary tumors collected at diagnosis and belonging to four existing data sets. Analyses took advantage of machine learning methods. We identified NB-hop, a seven-gene hypoxia biomarker, as a predictor of NB patient prognosis, which is able to discriminate between two populations of patients with unfavorable or favorable outcome on a molecular basis. NB-hop retained its prognostic value in a multivariate model adjusted for established risk factors and was able to additionally stratify clinically relevant groups of patients. Tumors with an unfavorable NB-hop expression showed a significant association with telomerase activation and a hypoxic, immunosuppressive, poorly differentiated, and apoptosis-resistant tumor microenvironment. NB-hop defines a new population of NB patients with hypoxic tumors and unfavorable prognosis and it represents a critical factor for the stratification and treatment of NB patients.