Inhibition of DNA-PK potentiates the synergistic effect of NK314 and etoposide combination on human glioblastoma cells

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.

DNA Double-Strand Break Repair Inhibitors: YU238259, A12B4C3 and DDRI-18 Overcome the Cisplatin Resistance in Human Ovarian Cancer Cells, but Not under Hypoxia Conditions

Cisplatin (CDDP) is the cornerstone of standard treatment for ovarian cancer. However, the resistance of ovarian cancer cells to CDDP leads to an inevitable recurrence. One of the strategies to overcome resistance to CDDP is the combined treatment of ovarian cancer with CDDP and etoposide (VP-16), although this strategy is not always effective. This article presents a new approach to sensitize CDDP-resistant human ovarian carcinoma cells to combined treatment with CDDP and VP-16. To replicate the tumor conditions of cancers, we performed analysis under hypoxia conditions. Since CDDP and VP-16 induce DNA double-strand breaks (DSB), we introduce DSB repair inhibitors to the treatment scheme. We used novel HRR and NHEJ inhibitors: YU238259 inhibits the HRR pathway, and DDRI-18 and A12B4C3 act as NHEJ inhibitors. All inhibitors enhanced the therapeutic effect of the CDDP/VP-16 treatment scheme and allowed a decrease in the effective dose of CDDP/VP16. Inhibition of HRR or NHEJ decreased survival and increased DNA damage level, increased the amount of γ-H2AX foci, and caused an increase in apoptotic fraction after treatment with CDDP/VP16. Furthermore, delayed repair of DSBs was detected in HRR- or NHEJ-inhibited cells. This favorable outcome was altered under hypoxia, during which alternation at the transcriptome level of the transcriptome in cells cultured under hypoxia compared to aerobic conditions. These changes suggest that it is likely that other than classical DSB repair systems are activated in cancer cells during hypoxia. Our study suggests that the introduction of DSB inhibitors may improve the effectiveness of commonly used ovarian cancer treatment, and HRR, as well as NHEJ, is an attractive therapeutic target for overcoming the resistance to CDDP resistance of ovarian cancer cells. However, a hypoxia-mediated decrease in response to our scheme of treatment was observed.

The anterior gradient homologue 2 (AGR2) co-localises with the glucose-regulated protein 78 (GRP78) in cancer stem cells, and is critical for the survival and drug resistance of recurrent glioblastoma: in situ and in vitro analyses

BACKGROUND

Glioblastomas (GBs) are characterised as one of the most aggressive primary central nervous system tumours (CNSTs). Single-cell sequencing analysis identified the presence of a highly heterogeneous population of cancer stem cells (CSCs). The proteins anterior gradient homologue 2 (AGR2) and glucose-regulated protein 78 (GRP78) are known to play critical roles in regulating unfolded protein response (UPR) machinery. The UPR machinery influences cell survival, migration, invasion and drug resistance. Hence, we investigated the role of AGR2 in drug-resistant recurrent glioblastoma cells.

METHODS

Immunofluorescence, biological assessments and whole exome sequencing analyses were completed under in situ and in vitro conditions. Cells were treated with CNSTs clinical/preclinical drugs taxol, cisplatin, irinotecan, MCK8866, etoposide, and temozolomide, then resistant cells were analysed for the expression of AGR2. AGR2 was repressed using single and double siRNA transfections and combined with either temozolomide or irinotecan.

RESULTS

Genomic and biological characterisations of the AGR2-expressed Jed66_GB and Jed41_GB recurrent glioblastoma tissues and cell lines showed features consistent with glioblastoma. Immunofluorescence data indicated that AGR2 co-localised with the UPR marker GRP78 in both the tissue and their corresponding primary cell lines. AGR2 and GRP78 were highly expressed in glioblastoma CSCs. Following treatment with the aforementioned drugs, all drug-surviving cells showed high expression of AGR2. Prolonged siRNA repression of a particular region in AGR2 exon 2 reduced AGR2 protein expression and led to lower cell densities in both cell lines. Co-treatments using AGR2 exon 2B siRNA in conjunction with temozolomide or irinotecan had partially synergistic effects. The slight reduction of AGR2 expression increased nuclear Caspase-3 activation in both cell lines and caused multinucleation in the Jed66_GB cell line.

CONCLUSIONS

AGR2 is highly expressed in UPR-active CSCs and drug-resistant GB cells, and its repression leads to apoptosis, via multiple pathways.

Inhibition of Protein Disulfide Isomerase (PDIA1) Leads to Proteasome-Mediated Degradation of Ubiquitin-like PHD and RING Finger Domain-Containing Protein 1 (UHRF1) and Increased Sensitivity of Glioblastoma Cells to Topoisomerase II Inhibitors

Glioblastoma (GBM) is the most aggressive brain tumor, and the prognosis remains poor with current available treatments. PDIA1 is considered a promising therapeutic target in GBM. In this study, we demonstrate that targeting PDIA1 results in increased GBM cell death by topoisomerase II (Top-II) inhibitors resulting in proteasome-mediated degradation of the oncogenic protein UHRF1. Combination of the PDIA1 inhibitor, bepristat-2a, produces strong synergy with doxorubicin, etoposide, and mitoxantrone in GBM and other cancer cell lines. Our bioinformatics analysis of multiple datasets revealed downregulation of UHRF1, upon PDIA1 inhibition. In addition, PDIA1 inhibition results in proteasome-mediated degradation of UHRF1 protein. Interestingly, treatment of GBM cells with bepristat-2a results in increased apoptosis and resistance to ferroptosis. Our findings emphasize the importance of PDIA1 as a therapeutic target in GBM and present a promising new therapeutic approach using Top-II inhibitors for GBM treatment.

Perspective on the Use of DNA Repair Inhibitors as a Tool for Imaging and Radionuclide Therapy of Glioblastoma

Simple Summary

The current routine treatment for glioblastoma (GB), the most lethal high-grade brain tumor in adults, aims to induce DNA damage in the tumor. However, the tumor cells might be able to repair that damage, which leads to therapy resistance. Fortunately, DNA repair defects are common in GB cells, and their survival is often based on a sole backup repair pathway. Hence, targeted drugs inhibiting essential proteins of the DNA damage response have gained momentum and are being introduced in the clinic. This review gives a perspective on the use of radiopharmaceuticals targeting DDR kinases for imaging in order to determine the DNA repair phenotype of GB, as well as for effective radionuclide therapy. Finally, four new promising radiopharmaceuticals are suggested with the potential to lead to a more personalized GB therapy.

Abstract

Despite numerous innovative treatment strategies, the treatment of glioblastoma (GB) remains challenging. With the current state-of-the-art therapy, most GB patients succumb after about a year. In the evolution of personalized medicine, targeted radionuclide therapy (TRT) is gaining momentum, for example, to stratify patients based on specific biomarkers. One of these biomarkers is deficiencies in DNA damage repair (DDR), which give rise to genomic instability and cancer initiation. However, these deficiencies also provide targets to specifically kill cancer cells following the synthetic lethality principle. This led to the increased interest in targeted drugs that inhibit essential DDR kinases (DDRi), of which multiple are undergoing clinical validation. In this review, the current status of DDRi for the treatment of GB is given for selected targets: ATM/ATR, CHK1/2, DNA-PK, and PARP. Furthermore, this review provides a perspective on the use of radiopharmaceuticals targeting these DDR kinases to (1) evaluate the DNA repair phenotype of GB before treatment decisions are made and (2) induce DNA damage via TRT. Finally, by applying in-house selection criteria and analyzing the structural characteristics of the DDRi, four drugs with the potential to become new therapeutic GB radiopharmaceuticals are suggested.

DNA-PKcs: A Targetable Protumorigenic Protein Kinase

DNA-dependent protein kinase catalytic subunit (DNA-PKcs) is a pleiotropic protein kinase that plays critical roles in cellular processes fundamental to cancer. DNA-PKcs expression and activity are frequently deregulated in multiple hematologic and solid tumors and have been tightly linked to poor outcome. Given the potentially influential role of DNA-PKcs in cancer development and progression, therapeutic targeting of this kinase is being tested in preclinical and clinical settings. This review summarizes the latest advances in the field, providing a comprehensive discussion of DNA-PKcs functions in cancer and an update on the clinical assessment of DNA-PK inhibitors in cancer therapy.

DNA damage repair in glioblastoma: current perspectives on its role in tumour progression, treatment resistance and PIKKing potential therapeutic targets

BACKGROUND

The aggressive, invasive and treatment resistant nature of glioblastoma makes it one of the most lethal cancers in humans. Total surgical resection is difficult, and a combination of radiation and chemotherapy is used to treat the remaining invasive cells beyond the tumour border by inducing DNA damage and activating cell death pathways in glioblastoma cells. Unfortunately, recurrence is common and a major hurdle in treatment, often met with a more aggressive and treatment resistant tumour. A mechanism of resistance is the response of DNA repair pathways upon treatment-induced DNA damage, which enact cell-cycle arrest and repair of DNA damage that would otherwise cause cell death in tumour cells.

CONCLUSIONS

In this review, we discuss the significance of DNA repair mechanisms in tumour formation, aggression and treatment resistance. We identify an underlying trend in the literature, wherein alterations in DNA repair pathways facilitate glioma progression, while established high-grade gliomas benefit from constitutively active DNA repair pathways in the repair of treatment-induced DNA damage. We also consider the clinical feasibility of inhibiting DNA repair in glioblastoma and current strategies of using DNA repair inhibitors as agents in combination with chemotherapy, radiation or immunotherapy. Finally, the importance of blood-brain barrier penetrance when designing novel small-molecule inhibitors is discussed.

The Application of Chemometrics for Efficiency Enhancement and Toxicity Reduction in Cancer Treatment with Combined Therapy

Chemometrics is an important emerging discipline with unique charm formed by the intersection of mathematics, statistics, chemistry and computer science. The application of chemometrics in the field of pharmacy has injected fresh blood into the scientific research and clinical practice of medicine and has provided a sufficient scientific basis for drug analysis and content determination to solve the problem of cancer treatment with combined therapy in different ranges. This paper introduces the basic principles, advantages and disadvantages of several commonly used pattern recognition and multidimensional correction methods of chemometrics, reviews the application of chemometrics for efficiency enhancement and toxicity reduction in cancer treatment with combined therapy and summarizes its development and prospects in the future.

Novel Concepts of Glioblastoma Therapy Concerning Its Heterogeneity

Although treatment outcomes of glioblastoma, the most malignant central nervous system (CNS) tumor, has improved in the past decades, it is still incurable, and survival has only slightly improved. Advances in molecular biology and genetics have completely transformed our understanding of glioblastoma. Multiple classifications and different diagnostic methods were made according to novel molecular markers. Discovering tumor heterogeneity only partially explains the ineffectiveness of current anti-proliferative therapies. Dynamic heterogeneity secures resistance to combined oncotherapy. As tumor growth proceeds, new therapy-resistant sub clones emerge. Liquid biopsy is a new and promising diagnostic tool that can step up with the dynamic genetic change. Getting a 'real-time' picture of a specific tumor, anti-invasion and multi-target treatment can be designed. During invasion to the peri-tumoral brain tissue, glioma cells interact with the extracellular matrix components. The expressional levels of these matrix molecules give a characteristic pattern, the invasion spectrum, which possess vast diagnostical, predictive and prognostic information. It is a huge leap forward combating tumor heterogeneity and searching for novel therapies. Using the invasion spectrum of a tumor sample is a novel tool to distinguish between histological subtypes, specifying the tumor grades or different prognostic groups. Moreover, new therapeutic methods and their combinations are under trial. These are crucial steps towards personalized oncotherapy.

DNA double-strand breaks repair inhibitors potentiates the combined effect of VP-16 and CDDP in human colorectal adenocarcinoma (LoVo) cells

I.

BACKGROUND

A combination of etoposide (VP-16) and cisplatin (CDDP) is the standard treatment for certain colon cancers. These drugs promote the death of cancer cells via direct and indirect induction of the most lethal DNA lesions - DNA double-stand breaks. However, cancer cells can reverse the DNA damaging effect of anticancer drugs by triggering DNA repair processes. In eukaryotic cells, the main DNA repair pathway responsible for DNA double-stand breaks repair is non-homologous end-joining (NHEJ). Inhibitors of DNA repair are of special interest in cancer research as they could break the cellular resistance to DNA-damaging agents and increase the efficiency of standard cancer treatments. In this study, we investigated the effect of two NHEJ inhibitors, SCR7 and NU7441, on the cytotoxic mechanism of VP-16/CDDP in a LoVo human colorectal adenocarcinoma cell line. SCR7 blocks Ligase IV-mediated joining by interfering with its DNA binding, whereas NU7441 is a highly potent and selective DNA-PK inhibitor.II.

METHODS AND RESULTS

Both inhibitors synergistically increased the cytotoxicity of CDDP and VP-16 when combined, but the effect of SCR7 was more pronounced. SCR7 and NU7441 also significantly increased VP-16; CDDP induced DNA double-stand breaks level and delayed drug-induced DSB repair, as seen on the comet assay and measured using H2AX foci. We also observed changes in cell cycle distribution and enhanced apoptosis ratio in colorectal adenocarcinoma cells treated with DNA repair inhibitors and VP-16/CDDP.III.

CONCLUSIONS

Our data support the hypothesis that NHEJ inhibitors could be used in conjunction with standard therapy to provide effective clinical improvement and allow reduction in drug doses.

Beyond DNA Repair: DNA-PKcs in Tumor Metastasis, Metabolism and Immunity

The DNA-dependent protein kinase catalytic subunit (DNA-PKcs) is a key component of the DNA-PK complex that has a well-characterized function in the non-homologous end-joining repair of DNA double-strand breaks. Since its identification, a large body of evidence has demonstrated that DNA-PKcs is frequently overexpressed in cancer, plays a critical role in tumor development and progression, and is associated with poor prognosis of cancer patients. Intriguingly, recent studies have suggested novel functions beyond the canonical role of DNA-PKcs, which has transformed the paradigm of DNA-PKcs in tumorigenesis and has reinvigorated the interest to target DNA-PKcs for cancer treatment. In this review, we update recent advances in DNA-PKcs, in particular the emerging roles in tumor metastasis, metabolic dysregulation, and immune escape. We further discuss the possible molecular basis that underpins the pleiotropism of DNA-PKcs in cancer. Finally, we outline the biomarkers that may predict the therapeutic response to DNA-PKcs inhibitor therapy. Understanding the functional repertoire of DNA-PKcs will provide mechanistic insights of DNA-PKcs in malignancy and, more importantly, may revolutionize the design and utility of DNA-PKcs-based precision cancer therapy.