DNA double-strand breaks: signaling, repair and the cancer connection

The role of RNF138 in DNA end resection is regulated by ubiquitylation and CDK phosphorylation

Double-strand breaks (DSBs) are DNA lesions that pose a significant threat to genomic stability. The repair of DSBs by the homologous recombination (HR) pathway is preceded by DNA end resection, the 5' to 3' nucleolytic degradation of DNA away from the DSB. We and others previously identified a role for RNF138, a really interesting new gene finger E3 ubiquitin ligase, in stimulating DNA end resection and HR. Yet, little is known about how RNF138's function is regulated in the context of DSB repair. Here, we show that RNF138 is phosphorylated at residue T27 by cyclin-dependent kinase (CDK) activity during the S and G2 phases of the cell cycle. We also observe that RNF138 is ubiquitylated constitutively, with ubiquitylation occurring in part on residue K158 and rising during the S/G2 phases. Interestingly, RNF138 ubiquitylation decreases upon genotoxic stress. By mutating RNF138 at residues T27, K158, and the previously identified S124 ataxia telangiectasia mutated phosphorylation site (Han et al., 2016, ref. 22), we find that post-translational modifications at all three positions mediate DSB repair. Cells expressing the T27A, K158R, and S124A variants of RNF138 are impaired in DNA end resection, HR activity, and are more sensitive to ionizing radiation compared to those expressing wildtype RNF138. Our findings shed more light on how RNF138 activity is controlled by the cell during HR.

The analyses of human MCPH1 DNA repair machinery and genetic variations

Causal mutations in the MCPH1 gene have been associated with disorders like microcephaly, and recently congenital hearing impairment. This study examined the MCPH1 DNA repair machinery and identified genetic variations of interest in gnomAD database to discuss the biological roles and effects of rare variants in MCPH1-related diseases. Notably, MCPH1 coordinates two of the seven known mechanisms of DNA repair which confirmed its roles in neurogenesis and chromatin condensation. A pathogenic missense variant in MCPH1 p.Gly753Arg, and two pathogenic frameshifts MCPH1 p.Asn189LysfsTer15 and p.Cys624Ter identified in this study, already had entries in ClinVar and were associated with microcephaly. A pathogenic frameshift in MCPH1 p.Val10SerfsTer5 with a loss-of-function flag and a pathogenic stop gained p.Ser571Ter variants with ultra-rare allele frequency (MAF ≤ 0.001) were identified but have not been linked to any phenotype. The predicted pathogenic ultra-rare variants identified in this study, warranty phenotypic discovery, and also positioned these variants or nearby deleterious variants candidate for screening in MCPH1-associated rare diseases.

Meiotic protein SYCP2 confers resistance to DNA-damaging agents through R-loop-mediated DNA repair

Drugs targeting the DNA damage response (DDR) are widely used in cancer therapy, but resistance to these drugs remains a major clinical challenge. Here, we show that SYCP2, a meiotic protein in the synaptonemal complex, is aberrantly and commonly expressed in breast and ovarian cancers and associated with broad resistance to DDR drugs. Mechanistically, SYCP2 enhances the repair of DNA double-strand breaks (DSBs) through transcription-coupled homologous recombination (TC-HR). SYCP2 promotes R-loop formation at DSBs and facilitates RAD51 recruitment independently of BRCA1. SYCP2 loss impairs RAD51 localization, reduces TC-HR, and renders tumors sensitive to PARP and topoisomerase I (TOP1) inhibitors. Furthermore, our studies of two clinical cohorts find that SYCP2 overexpression correlates with breast cancer resistance to antibody-conjugated TOP1 inhibitor and ovarian cancer resistance to platinum treatment. Collectively, our data suggest that SYCP2 confers cancer cell resistance to DNA-damaging agents by stimulating R-loop-mediated DSB repair, offering opportunities to improve DDR therapy.

Lipoprotein(a) is associated with DNA damage in patients with heterozygous familial hypercholesterolemia

Heterozygous familial hypercholesterolemia (HeFH) is a common autosomal-dominant inherited disorder associated with atherosclerotic cardiovascular disease (ASCVD). HeFH subjects have a higher lipoprotein(a), i.e. Lp(a), concentration than the general population. Patients with FH are exposed to elevated levels of LDL from birth and ox-LDL may induce other oxidation pathways. The aim of the study was to determine the levels of markers of oxidative stress and DNA damage in patients with HeFH and describe the effect of Lp(a) on the resulting damage. Higher DNA damage was identified in patients with HeFH compared to the normolipidemic ones, and ASCVD was associated with greater damage. Oxidative stress markers were elevated in HeFH patients; however, only ox-LDL was higher in the ASCVD group and its level correlated with DNA damage. A positive correlation was found between DNA damage and Lp(a) concentration in the HeFH patients. Higher levels of Lp(a) were associated with greater DNA damage, especially in patients with HeFH and ASCVD. In HeFH patients, the optimal Lp(a) cut-off point associated with ASCVD is > 23.45 nmol/L, i.e. much lower than for the general population; however this cut-off point needs validation in a larger group of HeFH patients.

Long-term outcomes of young, node-negative, chemotherapy-naïve, triple-negative breast cancer patients according to BRCA1 status

BACKGROUND

Due to the abundant usage of chemotherapy in young triple-negative breast cancer (TNBC) patients, the unbiased prognostic value of BRCA1-related biomarkers in this population remains unclear. In addition, whether BRCA1-related biomarkers modify the well-established prognostic value of stromal tumor-infiltrating lymphocytes (sTILs) is unknown. This study aimed to compare the outcomes of young, node-negative, chemotherapy-naïve TNBC patients according to BRCA1 status, taking sTILs into account.

METHODS

We included 485 Dutch women diagnosed with node-negative TNBC under age 40 between 1989 and 2000. During this period, these women were considered low-risk and did not receive chemotherapy. BRCA1 status, including pathogenic germline BRCA1 mutation (gBRCA1m), somatic BRCA1 mutation (sBRCA1m), and tumor BRCA1 promoter methylation (BRCA1-PM), was assessed using DNA from formalin-fixed paraffin-embedded tissue. sTILs were assessed according to the international guideline. Patients' outcomes were compared using Cox regression and competing risk models.

RESULTS

Among the 399 patients with BRCA1 status, 26.3% had a gBRCA1m, 5.3% had a sBRCA1m, 36.6% had tumor BRCA1-PM, and 31.8% had BRCA1-non-altered tumors. Compared to BRCA1-non-alteration, gBRCA1m was associated with worse overall survival (OS) from the fourth year after diagnosis (adjusted HR, 2.11; 95% CI, 1.18-3.75), and this association attenuated after adjustment for second primary tumors. Every 10% sTIL increment was associated with 16% higher OS (adjusted HR, 0.84; 95% CI, 0.78-0.90) in gBRCA1m, sBRCA1m, or BRCA1-non-altered patients and 31% higher OS in tumor BRCA1-PM patients. Among the 66 patients with tumor BRCA1-PM and ≥ 50% sTILs, we observed excellent 15-year OS (97.0%; 95% CI, 92.9-100%). Conversely, among the 61 patients with gBRCA1m and < 50% sTILs, we observed poor 15-year OS (50.8%; 95% CI, 39.7-65.0%). Furthermore, gBRCA1m was associated with higher (adjusted subdistribution HR, 4.04; 95% CI, 2.29-7.13) and tumor BRCA1-PM with lower (adjusted subdistribution HR, 0.42; 95% CI, 0.19-0.95) incidence of second primary tumors, compared to BRCA1-non-alteration.

CONCLUSIONS

Although both gBRCA1m and tumor BRCA1-PM alter BRCA1 gene transcription, they are associated with different outcomes in young, node-negative, chemotherapy-naïve TNBC patients. By combining sTILs and BRCA1 status for risk classification, we were able to identify potential subgroups in this population to intensify and optimize adjuvant treatment.

Molecular Mechanisms Determining Mammalian Oocyte Quality with the Treatment of Cancer Therapy

Cancer is a global public health issue and remains one of the leading causes of death in the United States (Siegel et al. CA Cancer J Clin. 72:7-33, 2022). It is estimated in the US in 2022, about 935,000 new cases of cancer will be diagnosed in women, and the probability of developing invasive cancer is 5.8% for females younger than 50 years old (Siegel et al. CA Cancer J Clin. 72:7-33, 2022). However, advances in screening programs, diagnostic methods, and therapeutic options have greatly increased the five-year survival rate in reproductive-age women with a variety of cancers. Given the clinical consequences of gonadotoxic cancer therapies, young, female cancer survivors may face compromised fertility, premature ovarian insufficiency, early-onset menopause, and endocrine dysregulation (Bedoschi et al. Future Oncol. 12:2333-44, 2016). Gonadotoxic side effects may include decreased oocyte quality within surviving follicles, loss of ovarian follicles, and impaired ovarian function. In reproductive-age women, oocyte quality is an important element for successful clinical pregnancies and healthy offspring as poor-quality oocytes may be a cause of infertility (McClam et al. Biol Reprod. 106:328-37, 2022; Marteil et al. Reprod Biol. 9:203-24, 2009; Krisher. J Anim Sci. 82: E14-E23, 2004). Thus, it is critical to determine the quantity and quality of surviving follicles in the ovary after cancer treatment and to assess oocyte quality within those surviving follicles as these are markers for determining the capacity for ovarian function restoration and future fertility, especially for young cancer survivors (Xu et al. Nat Med. 17:1562-3, 2011). The long-term effects of cancer therapeutics on oocyte quality are influenced by factors including, but not limited to, individual patient characteristics (e.g. age, health history, comorbidities, etc.), disease type, or treatment regimen (Marci et al. Reprod Biol Endocrinol. 16:1-112, 2018). These effects may translate clinically into an impaired production of viable oocytes and compromised fertility (Garutti et al. ESMO Open. 6:100276, 2021).

Prediction of CHO cell line stability using expression of DNA repair genes

Chinese hamster ovary (CHO) cells are essential to biopharmaceutical manufacturing and production instability, the loss of productivity over time, is a long-standing challenge in the industry. Accurate prediction of cell line stability could enable efficient screening to identify clones suitable for manufacturing saving significant time and costs. DNA repair genes may offer biomarkers to address this need. In this study, over 40 cell lines representing various host lineages from three companies/organizations were evaluated for expression of five DNA repair genes (Fam35a, Lig4, Palb2, Pari, and Xrcc6). Expression measured in cells with less than 30 population doubling levels (PDLs) was correlated to stability profiles at 60+ PDL. Principal component analysis identified markers which separate stable and unstable CHO-DG44 cell lines. Notably, two genes, Lig4 and Xrcc6, showed higher expression in unstable CHO-DG44 cell lines with copy number loss identified as the mechanism of production instability. Expression levels across all cell ages showed lower DNA repair gene expression was associated with increased cell age. Collectively, DNA repair genes provide critical insight into long-term behavior of CHO cells and their expression levels have potential to predict cell line stability in certain cases.

Real-time single-molecule visualization using DNA curtains reveals the molecular mechanisms underlying DNA repair pathways

The demand for direct observation of biomolecular interactions provides new insights into the molecular mechanisms underlying many biological processes. Single-molecule imaging techniques enable real-time visualization of individual biomolecules, providing direct observations of protein machines. Various single-molecule imaging techniques have been developed and have contributed to breakthroughs in biological research. One such technique is the DNA curtain, a novel, high-throughput, single-molecule platform that integrates lipid fluidity, nano-fabrication, microfluidics, and fluorescence imaging. Many DNA metabolic reactions, such as replication, transcription, and chromatin dynamics, have been studied using DNA curtains. In particular, the DNA curtain platform has been intensively applied in investigating the molecular details of DNA repair processes. This article reviews DNA curtain techniques and their applications for imaging DNA repair proteins.

Emerging evidence on the role of breast microbiota on the development of breast cancer in high-risk patients

Cancer is a multi-factorial disease, and the etiology of breast cancer (BC) is due to a combination of both genetic and environmental factors. Breast tissue shows a unique microbiota, Proteobacteria and Firmicutes are the most abundant bacteria in breast tissue, and several studies have shown that the microbiota of healthy breast differs from that of BC. Breast microbiota appears to be correlated with different characteristics of the tumor, and prognostic clinicopathologic features. It also appears that there are subtle differences between the microbial profiles of the healthy control and high-risk patients. Genetic predisposition is an extremely important risk factor for BC. BRCA1/2 germline mutations and Li-Fraumeni syndrome are DNA repair deficiency syndromes inherited as autosomal dominant characters that substantially increase the risk of BC. These syndromes exhibit incomplete penetrance of BC expression in carrier subjects. The action of breast microbiota on carcinogenesis might explain why women with a mutation develop cancer and others do not. Among the potential biological pathways through which the breast microbiota may affect tumorigenesis, the most relevant appear to be DNA damage caused by colibactin and other bacterial-derived genotoxins, β-glucuronidase-mediated estrogen deconjugation and reactivation, and HPV-mediated cancer susceptibility. In conclusion, in patients with a genetic predisposition, an unfavorable breast microbiota may be co-responsible for the onset of BC. Prospectively, the ability to modulate the microbiota may have an impact on disease onset and progression in patients at high risk for BC.

Identification of Genomic Instability in Cows Infected with BVD Virus

An important factor for dairy cattle farmers is the profitability of cattle rearing, which is influenced by the animals' health and reproductive parameters, as well as their genomic stability and integrity. Bovine viral diarrhea (BVD) negatively affects the health of dairy cattle and causes reproductive problems. The aim of the study was to identify genomic instability in cows with reproductive disorders following infection with the BVD virus. The material for analysis was peripheral blood from Holstein-Friesian cows with reproductive problems, which had tested positive for BVD, and from healthy cows with no reproductive problems, which had tested negative for BVD. Three cytogenetic tests were used: the sister chromatid exchange assay, fragile sites assay, and comet assay. Statistically significant differences were noted between the groups and between the individual cows in the average frequency of damage. The assays were good biomarkers of genomic stability and enabled the identification of individuals with an increased frequency of damage to genetic material that posed a negative impact on their health. The assays can be used to prevent disease during its course and evaluate the genetic resistance of animals. This is especially important for the breeder, both for economic and breeding reasons. Of the three assays, the comet assay proved to be the most sensitive for identifying DNA damage in the animals.

Topology of Ubiquitin Chains in the Chromatosomal Environment of the E3 Ubiquitin Ligase RNF168

Genome stability is critical for normal functioning of cells, it depends on accuracy of DNA replication, chromosome segregation, and DNA repair. Cellular defense mechanisms against DNA damage are important for preventing cancer development and aging. The E3 ubiquitin ligase RNF168 of the RING superfamily is an essential component of the complex responsible for ubiquitination of the H2A/H2A.X histones near DNA double-strand breaks, which is a key step in attracting repair factors to the damage site. In this study, we unequivocally showed that RNF168 does not have the ability to directly distinguish architecture of polyubiquitin chains, except for the tropism of its two ubiquitin-binding domains UDM1/2 to K63 ubiquitin chains. Analysis of intracellular chromatosomal environment of the full-length RNF168 and its domains using the ligand-induced bioluminescence resonance energy transfer (BRET) revealed that the C-terminal part of UDM1 is associated with the K63 ubiquitin chains; RING and the N-terminal part of UDM2 are sterically close to the K63- and K48-ubiquitin chains, while the C-terminal part of UDM1 is co-localized with all possible ubiquitin variants. Our observations together with the available structural data suggest that the C-terminal part of UDM1 binds the K63 polyubiquitin chains on the linker histone H1; RING and the N-terminal part of UDM2 are located in the central part of nucleosome and sterically close to H1 and K48-ubiquitinated alternative substrates of RNF168, such as JMJD2A/B demethylases, while the C-terminal part of UDM1 is in the region of activated ubiquitin residue associated with E2 ubiquitin ligase, engaged by RNF168.

Targeting the COMMD4-H2B protein complex in lung cancer

BACKGROUND

Lung cancer is the biggest cause of cancer-related deaths worldwide. Non-small cell lung cancer (NSCLC) accounts for 85-90% of all lung cancers. Identification of novel therapeutic targets are required as drug resistance impairs chemotherapy effectiveness. COMMD4 is a potential NSCLC therapeutic target. The aims of this study were to investigate the COMMD4-H2B binding pose and develop a short H2B peptide that disrupts the COMMD4-H2B interaction and mimics COMMD4 siRNA depletion.

METHODS

Molecular modelling, in vitro binding and site-directed mutagenesis were used to identify the COMMD4-H2B binding pose and develop a H2B peptide to inhibit the COMMD4-H2B interaction. Cell viability, DNA repair and mitotic catastrophe assays were performed to determine whether this peptide can specially kill NSCLC cells.

RESULTS

Based on the COMMD4-H2B binding pose, we have identified a H2B peptide that inhibits COMMD4-H2B by directly binding to COMMD4 on its H2B binding binding site, both in vitro and in vivo. Treatment of NSCLC cell lines with this peptide resulted in increased sensitivity to ionising radiation, increased DNA double-strand breaks and induction of mitotic catastrophe in NSCLC cell lines.

CONCLUSIONS

Our data shows that COMMD4-H2B represents a novel potential NSCLC therapeutic target.

Haberlea rhodopensis Extract Tunes the Cellular Response to Stress by Modulating DNA Damage, Redox Components, and Gene Expression

Ionizing radiation (IR) and reactive oxygen species (ROS)-induced oxidative stress can cause damage to cellular biomolecules, including DNA, proteins, and lipids. These harmful effects can compromise essential cellular functions and significantly raise the risk of metabolic dysfunction, accumulation of harmful mutations, genome instability, cancer, accelerated cellular senescence, and even death. Here, we present an investigation of HeLa cancer cells' early response to gamma IR (γ-IR) and oxidative stress after preincubation of the cells with natural extracts of the resurrection plant Haberlea rhodopensis. In light of the superior protection offered by plant extracts against radiation and oxidative stress, we investigated the cellular defence mechanisms involved in such protection. Specifically, we sought to evaluate the molecular effects of H. rhodopensis extract (HRE) on cells subjected to genotoxic stress by examining the components of the redox pathway and quantifying the transcription levels of several critical genes associated with DNA repair, cell cycle regulation, and apoptosis. The influence of HRE on genome integrity and the cell cycle was also studied via comet assay and flow cytometry. Our findings demonstrate that HREs can effectively modulate the cellular response to genotoxic and oxidative stress within the first two hours following exposure, thereby reducing the severity of such stress. Furthermore, we observed the specificity of genoprotective HRE doses depending on the source of the applied genotoxic stress.

Selenium protection from DNA damage and regulation of apoptosis signaling following cyclophosphamide induced cardiotoxicity in rats

We investigated the mechanism of the cardioprotective effect of selenium (Se) against cyclophosphamide (CPA) induced cardiotoxicity in rats. We divided 24 female Wistar albino rats into four groups. The control group was injected intraperitoneally (i.p.) with normal saline. The CPA group was injected i.p. with 200 mg/kg CPA. The Se group was injected i.p. with 1 mg/kg Se. The CPA + Se group was injected i.p. with 200 mg/kg CPA and 1 mg/kg Se. Rats were euthanized 24 h after injection and heart tissues were harvested. Histopathological examination revealed reduced severity of myocardial lesions in the CPA + Se group compared to CPA induced cardiotoxicity of the CPA group; this finding was confirmed by increased immunoreactivity of cardiac troponin-I (cTn-I) in the CPA + Se group compared to decreased cTn-I immunoreactivity in the CPA group. Administration of CPA increased the immunoreactivity of phosphorylated histone-2AX (γH2AX). Se reduced the CPA induced increase in γH2AX immunoreactivity. Se administration reversed the CPA induced increase of Bax and decrease of Bcl2 gene expressions. Our findings suggest that Se is cardioprotective by reducing DNA damage and regulating the genes responsible for apoptosis caused by CPA in rats.

Deficiency of ligase IV leads to reduced NHEJ, accumulation of DNA damage, and can sensitize cells to cancer therapeutics

Ligase IV is a key enzyme involved during DNA double-strand breaks (DSBs) repair through nonhomologous end joining (NHEJ). However, in contrast to Ligase IV deficient mouse cells, which are embryonic lethal, Ligase IV deficient human cells, including pre-B cells, are viable. Using CRISPR-Cas9 mediated genome editing, we have generated six different LIG4 mutants in cervical cancer and normal kidney epithelial cell lines. While the LIG4 mutant cells showed a significant reduction in NHEJ, joining mediated through microhomology-mediated end joining (MMEJ) and homologous recombination (HR) were significantly high. The reduced NHEJ joining activity was restored by adding purified Ligase IV/XRCC4. Accumulation of DSBs and reduced cell viability were observed in LIG4 mutant cells. LIG4 mutant cells exhibited enhanced sensitivity towards DSB-inducing agents such as ionizing radiation (IR) and etoposide. More importantly, the LIG4 mutant of cervical cancer cells showed increased sensitivity towards FDA approved drugs such as Carboplatin, Cisplatin, Paclitaxel, Doxorubicin, and Bleomycin used for cervical cancer treatment. These drugs, in combination with IR showed enhanced cancer cell death in the background of LIG4 gene mutation. Thus, our study reveals that mutation in LIG4 results in compromised NHEJ, leading to sensitization of cervical cancer cells towards currently used cancer therapeutics.

Effector memory T cells induce innate inflammation by triggering DNA damage and a non-canonical STING pathway in dendritic cells

Cognate interaction between CD4+ effector memory T (TEM) cells and dendritic cells (DCs) induces innate inflammatory cytokine production, resulting in detrimental autoimmune pathology and cytokine storms. While TEM cells use tumor necrosis factor (TNF) superfamily ligands to activate DCs, whether TEM cells prompt other DC-intrinsic changes that influence the innate inflammatory response has never been investigated. We report the surprising discovery that TEM cells trigger double-strand DNA breaks via mitochondrial reactive oxygen species (ROS) production in interacting DCs. Initiation of the DNA damage response in DCs induces activation of a cyclic guanosine monophosphate (GMP)-AMP synthase (cGAS)-independent, non-canonical stimulator of interferon genes (STING)-TNF receptor-associated factor 6 (TRAF6)-nuclear factor κB (NF-κB) signaling axis. Consequently, STING-deficient DCs display reduced NF-κB activation and subsequent defects in transcriptional induction and functional production of interleukin-1β (IL-1β) and IL-6 following their interaction with TEM cells. The discovery of TEM cell-induced innate inflammation through DNA damage and a non-canonical STING-NF-κB pathway presents this pathway as a potential target to alleviate T cell-driven inflammation in autoimmunity and cytokine storms.

Biotin-decorated hollow gold nanoshells for dual-modal imaging-guided NIR-II photothermal and radiosensitizing therapy toward breast cancer

Radiotherapy (RT) is dominantly used in breast cancer therapy but is facing fierce side effects because of the limited difference between tumor and normal tissues in response to ionizing radiation. Herein, we construct a core-shell nanoparticle of UiO-66-NH2@AuNS. Then the solid gold shell was etched into hollow AuNS (HAuNS) and further modified with biotin-PEG-SH (PEG-bio) to obtain HAuNS@PEG-bio. HAuNS@PEG-bio demonstrates effective near infrared II (NIR-II) region photothermal therapy (PTT) performance, and the increase of temperature at the tumor site promotes the blood circulation to alleviate the hypoxia in the tumor microenvironment (TME). Meanwhile, HAuNS exhibits strong X-ray absorption and deposition ability due to the high atomic coefficient of elemental Au (Z = 79) and hollowed-out structure. Through the dual radiosensitization of the high atomic coefficient of Au and the hypoxia alleviation from PTT of HAuNS, the breast cancer cells could undergo immunogenic cell death (ICD) to activate the immune response. At the in vivo level, HAuNS@PEG-bio performs NIR-II photothermal, radiosensitization, and ICD therapies through cellular targeting, guided by infrared heat and CT imaging. This work highlights that the constructed biotin-decorated hollow gold nanoshell has a promising potential as a diagnostic and treatment integration reagents for the breast cancer.

Chemical Insights into Oxidative and Nitrative Modifications of DNA

This review focuses on DNA damage caused by a variety of oxidizing, alkylating, and nitrating species, and it may play an important role in the pathophysiology of inflammation, cancer, and degenerative diseases. Infection and chronic inflammation have been recognized as important factors in carcinogenesis. Under inflammatory conditions, reactive oxygen species (ROS) and reactive nitrogen species (RNS) are generated from inflammatory and epithelial cells, and result in the formation of oxidative and nitrative DNA lesions, such as 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG) and 8-nitroguanine. Cellular DNA is continuously exposed to a very high level of genotoxic stress caused by physical, chemical, and biological agents, with an estimated 10,000 modifications occurring every hour in the genetic material of each of our cells. This review highlights recent developments in the chemical biology and toxicology of 2'-deoxyribose oxidation products in DNA.

Targeting MALAT1 Augments Sensitivity to PARP Inhibition by Impairing Homologous Recombination in Prostate Cancer

PARP inhibitors (PARPi) have emerged as a promising targeted therapeutic intervention for metastatic castrate-resistant prostate cancer (mCRPC). However, the clinical utility of PARPi is limited to a subset of patients who harbor aberrations in the genes associated with the homologous recombination (HR) pathway. Here, we report that targeting metastasis-associated lung adenocarcinoma transcript 1 (MALAT1), an oncogenic long noncoding RNA (lncRNA), contrives a BRCAness-like phenotype, and augments sensitivity to PARPi. Mechanistically, we show that MALAT1 silencing reprograms the homologous recombination (HR) transcriptome and makes prostate cancer cells more vulnerable to PARPi. Particularly, coinhibition of MALAT1 and PARP1 exhibits a decline in clonogenic survival, delays resolution of γH2AX foci, and reduces tumor burden in mice xenograft model. Moreover, we show that miR-421, a tumor suppressor miRNA, negatively regulates the expression of HR genes, while in aggressive prostate cancer cases, miR-421 is sequestered by MALAT1, leading to increased expression of HR genes. Conclusively, our findings suggest that MALAT1 ablation confers sensitivity to PARPi, thus highlighting an alternative therapeutic strategy for patients with castration-resistant prostate cancer (CRPC), irrespective of the alterations in HR genes.

SIGNIFICANCE

PARPi are clinically approved for patients with metastatic CRPC carrying mutations in HR genes, but are ineffective for HR-proficient prostate cancer. Herein, we show that oncogenic lncRNA, MALAT1 is frequently overexpressed in advanced stage prostate cancer and plays a crucial role in maintaining genomic integrity. Importantly, we propose a novel therapeutic strategy that emphasizes MALAT1 inhibition, leading to HR dysfunction in both HR-deficient and -proficient prostate cancer, consequently augmenting their susceptibility to PARPi.

The molecular details of a novel phosphorylation-dependent interaction between MRN and the SOSS complex

The repair of double-strand DNA breaks (DSBs) by homologous recombination is crucial in the maintenance of genome integrity. While the key role of the Mre11-Rad50-Nbs1 (MRN) complex in repair is well known, hSSB1 (SOSSB and OBFC2B), one of the main components of the sensor of single-stranded DNA (SOSS) protein complex, has also been shown to rapidly localize to DSB breaks and promote repair. We have previously demonstrated that hSSB1 binds directly to Nbs1, a component of the MRN complex, in a DNA damage-independent manner. However, recruitment of the MRN complex has also been demonstrated by an interaction between Integrator Complex Subunit 3 (INTS3; also known as SOSSA), another member of the SOSS complex, and Nbs1. In this study, we utilize a combined approach of in silico, biochemical, and functional experiments to uncover the molecular details of INTS3 binding to Nbs1. We demonstrate that the forkhead-associated domain of Nbs1 interacts with INTS3 via phosphorylation-dependent binding to INTS3 at Threonine 592, with contributions from Serine 590. Based on these data, we propose a model of MRN recruitment to a DSB via INTS3.

Potential agnostic role of BRCA alterations in patients with several solid tumors: One for all, all for one?

Germline BRCA1/2 alterations in the Homologous Recombination (HR) pathway are considered as main susceptibility biomarkers to Hereditary Breast and Ovarian Cancers (HBOC). The modern molecular biology technologies allowed to characterize germline and somatic BRCA1/2 alterations in several malignancies, broadening the landscape of BRCA1/2-alterated tumors. In the last years, BRCA genetic testing, beyond the preventive value, also assumed a predictive and prognostic significance for patient management. The approval of molecules with agnostic indication is leading to a new clinical model, defined "mutational". Among these drugs, the Poly (ADP)-Ribose Polymerase inhibitors (PARPi) for BRCA1/2-deficient tumors were widely studied leading to increasing therapeutic implications. In this Review we provided an overview of the main clinical studies describing the association between BRCA-mutated tumors and PARPi response, focusing on the controversial evidence about the potential agnostic indication based on BRCA1/2 alterations in several solid tumors.

The tremendous clinical potential of the microbiota in the treatment of breast cancer: the next frontier

Although significant advances have been made in the diagnosis and treatment of breast cancer (BC) in recent years, BC remains the most common cancer in women and one of the main causes of death among women worldwide. Currently, more than half of BC patients have no known risk factors, emphasizing the significance of identifying more tumor-related factors. Therefore, we urgently need to find new therapeutic strategies to improve prognosis. Increasing evidence demonstrates that the microbiota is present in a wider range of cancers beyond colorectal cancer. BC and breast tissues also have different types of microbiotas that play a key role in carcinogenesis and in modulating the efficacy of anticancer treatment, for instance, chemotherapy, radiotherapy, and immunotherapy. In recent years, studies have confirmed that the microbiota can be an important factor directly and/or indirectly affecting the occurrence, metastasis and treatment of BC by regulating different biological processes, such as estrogen metabolism, DNA damage, and bacterial metabolite production. Here, we review the different microbiota-focused studies associated with BC and explore the mechanisms of action of the microbiota in BC initiation and metastasis and its application in various therapeutic strategies. We found that the microbiota has vital clinical value in the diagnosis and treatment of BC and could be used as a biomarker for prognosis prediction. Therefore, modulation of the gut microbiota and its metabolites might be a potential target for prevention or therapy in BC.

Doxorubicin and other anthracyclines in cancers: Activity, chemoresistance and its overcoming

Anthracyclines have been important and effective treatments against a number of cancers since their discovery. However, their use in therapy has been complicated by severe side effects and toxicity that occur during or after treatment, including cardiotoxicity. The mode of action of anthracyclines is complex, with several mechanisms proposed. It is possible that their high toxicity is due to the large set of processes involved in anthracycline action. The development of resistance is a major barrier to successful treatment when using anthracyclines. This resistance is based on a series of mechanisms that have been studied and addressed in recent years. This work provides an overview of the anthracyclines used in cancer therapy. It discusses their mechanisms of activity, toxicity, and chemoresistance, as well as the approaches used to improve their activity, decrease their toxicity, and overcome resistance.

Pre-rRNA Facilitates TopBP1-Mediated DNA Double-Strand Break Response

In response to genotoxic stress-induced DNA damage, TopBP1 mediates ATR activation for signaling transduction and DNA damage repair. However, the detailed molecular mechanism remains elusive. Here, using unbiased protein affinity purification and RNA sequencing, it is found that TopBP1 is associated with pre-ribosomal RNA (pre-rRNA). Pre-rRNA co-localized with TopBP1 at DNA double-strand breaks (DSBs). Similar to pre-rRNA, ribosomal proteins also colocalize with TopBP1 at DSBs. The recruitment of TopBP1 to DSBs is suppressed when cells are transiently treated with RNA polymerase I inhibitor (Pol I-i) to suppress pre-rRNA biogenesis but not protein translation. Moreover, the BRCT4-5 of TopBP1 recognizes pre-rRNA and forms liquid-liquid phase separation (LLPS) with pre-rRNA, which may be the molecular basis of DSB-induced foci of TopBP1. Finally, Pol I-i treatment impairs TopBP1-associated cell cycle checkpoint activation and homologous recombination repair. Collectively, this study reveals that pre-rRNA plays a key role in the TopBP1-dependent DNA damage response.

Evaluation of Ataxia-Telangiectasia Mutated IVS10 Mutation in Breast Cancer Along with Clinicopathological Parameters

Background

Breast cancer is the most common cancer in women worldwide, with an estimated 2.26 million new cases diagnosed in 2020. The important genes associated include BRCA1, BRCA2, CHEK2, PTEN, TP53, and ataxia-telangiectasia mutated (ATM). ATM is responsible for repairing double-strand breaks in DNA making it a significant candidate in breast cancer predisposition. ATM variant, c.1066-6T>G, has been associated with an increased risk of breast cancer in some but not all studies. The Indian studies on the allele IVS10-6T>G are very limited. The present study was undertaken to evaluate the associations between c.1066-6T>G ATM gene variant and breast cancer incidence in Indian women and its correlation with histological grade, stage, and surrogate molecular classification.

Materials and Methods

Routine histopathological processing was done after adequate fixation of the specimen followed by staining with hematoxylin and eosin and immunohistochemistry for ER, PR, Her2neu, and Ki67. Single-nucleotide polymorphism for ATM allele IVS10-6T>G was studied after DNA extraction, polymerase chain reaction amplification, and restriction enzyme digestion.

Results

All cases were found to be negative for ATM allele IVS10-6T>G mutation. Maximum number of patients (19 cases; 52.78%) had pT2 stage tumor followed by 11 patients (30.56%) with pT3. Majority of cases were luminal B (11; 30.56%) followed by triple negative (10; 27.78%).

Conclusion

Although the results obtained by mutational analysis in the present study are not in agreement with the previous study on Indian women it agrees with the numerous previous studies and meta-analyses done on women with breast carcinoma in the Western world.

Foci-Xpress: Automated and Fast Nuclear Foci Counting Tool

In the nucleus, distinct, discrete spots or regions called "foci" have been identified, each harboring a specific molecular function. Accurate and efficient quantification of these foci is essential for understanding cellular dynamics and signaling pathways. In this study, we present an innovative automated image analysis method designed to precisely quantify subcellular foci within the cell nucleus. Manual foci counting methods can be tedious and time-consuming. To address these challenges, we developed an open-source software that automatically counts the number of foci from the indicated image files. We compared the foci counting efficiency, velocity, accuracy, and convenience of Foci-Xpress with those of other conventional methods in foci-induced models. We can adjust the brightness of foci to establish a threshold. The Foci-Xpress method was significantly faster than other conventional methods. Its accuracy was similar to that of conventional methods. The most significant strength of Foci-Xpress is automation, which eliminates the need for analyzing equipment while counting. This enhanced throughput facilitates comprehensive statistical analyses and supports robust conclusions from experiments. Furthermore, automation completely rules out biases caused by researchers, such as manual errors or daily variations. Thus, Foci-Xpress is a convincing, convenient, and easily accessible focus-counting tool for cell biologists.

A pan-cancer analysis reveals the diagnostic and prognostic role of CDCA2 in low-grade glioma

BACKGROUND

Cell division cycle associated 2 (CDCA2), a member of the cell division cycle associated proteins (CDCA) family, is crucial in the regulation of cell mitosis and DNA repair. CDCA2 was extensively examined in our work to determine its role in a wide range of cancers.

METHODS

CDCA2 differential expression was studied in pan-cancer and in diverse molecular and immunological subgroups in this research. Additionally, the diagnostic and prognostic significance of CDCA2 in pan-cancer was also evaluated using receiver operating characteristic (ROC) and Kaplan-Meier (KM) curves. Prognostic value of CDCA2 in distinct clinical subgroups of lower grade glioma (LGG) was also investigated and a nomogram was constructed. Lastly, potential mechanisms of action of CDCA2 were interrogated including biological functions, ceRNA networks, m6A modification and immune infiltration.

RESULTS

CDCA2 is shown to be differentially expressed in a wide variety of cancers. Tumors are diagnosed and forecasted with a high degree of accuracy by CDCA2, and the quantity of expression CDCA2 is linked to the prognosis of many cancers. Additionally, the expression level of CDCA2 in various subgroups of LGG is also closely related to prognosis. The results of enrichment analyses reveal that CDCA2 is predominantly enriched in the cell cycle, mitosis, and DNA replication. Subsequently, hsa-miR-105-5p is predicted to target CDCA2. In addition, 4 lncRNAs were identified that may inhibit the hsa-miR-105-5p/CDCA2 axis in LGG. Meanwhile, CDCA2 expression is shown to be associated to m6A-related genes and levels of immune cell infiltration in LGG.

CONCLUSION

CDCA2 can serve as a novel biomarker for the diagnosis and prognosis in pan-cancer, especially in LGG. For the development of novel targeted therapies in LGG, it may be a potential molecular target. However, to be sure, we'll need to do additional biological experiments to back up our results from bioinformatic predictions.

Unraveling MYC's Role in Orchestrating Tumor Intrinsic and Tumor Microenvironment Interactions Driving Tumorigenesis and Drug Resistance

The transcription factor MYC plays a pivotal role in regulating various cellular processes and has been implicated in tumorigenesis across multiple cancer types. MYC has emerged as a master regulator governing tumor intrinsic and tumor microenvironment interactions, supporting tumor progression and driving drug resistance. This review paper aims to provide an overview and discussion of the intricate mechanisms through which MYC influences tumorigenesis and therapeutic resistance in cancer. We delve into the signaling pathways and molecular networks orchestrated by MYC in the context of tumor intrinsic characteristics, such as proliferation, replication stress and DNA repair. Furthermore, we explore the impact of MYC on the tumor microenvironment, including immune evasion, angiogenesis and cancer-associated fibroblast remodeling. Understanding MYC's multifaceted role in driving drug resistance and tumor progression is crucial for developing targeted therapies and combination treatments that may effectively combat this devastating disease. Through an analysis of the current literature, this review's goal is to shed light on the complexities of MYC-driven oncogenesis and its potential as a promising therapeutic target.

Mutational spectrum of DNA damage and mismatch repair genes in prostate cancer

Over the past few years, a number of studies have revealed that a significant number of men with prostate cancer had genetic defects in the DNA damage repair gene response and mismatch repair genes. Certain of these modifications, notably gene alterations known as homologous recombination (HRR) genes; PALB2, CHEK2 BRCA1, BRCA2, ATM, and genes for DNA mismatch repair (MMR); MLH1, MSH2, MSH6, and PMS2 are connected to a higher risk of prostate cancer and more severe types of the disease. The DNA damage repair (DDR) is essential for constructing and diversifying the antigen receptor genes required for T and B cell development. But this DDR imbalance results in stress on DNA replication and transcription, accumulation of mutations, and even cell death, which compromises tissue homeostasis. Due to these impacts of DDR anomalies, tumor immunity may be impacted, which may encourage the growth of tumors, the release of inflammatory cytokines, and aberrant immune reactions. In a similar vein, people who have altered MMR gene may benefit greatly from immunotherapy. Therefore, for these treatments, mutational genetic testing is indicated. Mismatch repair gene (MMR) defects are also more prevalent than previously thought, especially in patients with metastatic disease, high Gleason scores, and diverse histologies. This review summarizes the current information on the mutation spectrum and clinical significance of DDR mechanisms, such as HRR and MMR abnormalities in prostate cancer, and explains how patient management is evolving as a result of this understanding.

Chemical composition, antioxidant, and enzyme inhibitory properties of Rauwolfia vomitoria extract

OBJECTIVES

Rauwolfia vomitoria is one ethno-botanicals in Nigeria used by traditional health practitioners in managing several human diseases. However, necessary information regarding its effect on enzymes implicated in the development and progression of erectile dysfunction is missing in the literature. Thus, this study investigated the antioxidant property and impact of Rauwolfia vomitoria extract on erectile dysfunction-related enzymes in vitro.

METHODS

High performance liquid chromatography was used to identify and quantify Rauwolfia vomitoria's phenolic components. Then, utilizing common antioxidant assays, the extract's antioxidant properties were evaluated and finally the effect of the extract on some enzymes (AChE, arginase and ACE) implicated in erectile dysfunction was investigated in vitro.

RESULTS

The results showed that the extract inhibited AChE (IC50=388.72 μg/mL), arginase (IC50=40.06 μg/mL) and ACE (IC50=108.64 μg/mL) activities. In addition, phenolic rich extract of Rauvolfia vomitoria scavenged radicals and chelated Fe2+ in concentration dependent manner. Furthermore, rutin, chlorogenic acid, gallic acid, and kaempferol were found in large quantities by HPLC analysis.

CONCLUSIONS

Therefore, one of the potential reasons driving Rauwolfia vomitoria's use in folk medicine for the treatment of erectile dysfunction could be its antioxidant and inhibitory activities on several enzymes linked to erectile dysfunction in vitro.

New Views of the DNA Repair Protein Ataxia-Telangiectasia Mutated in Central Neurons: Contribution in Synaptic Dysfunctions of Neurodevelopmental and Neurodegenerative Diseases

Ataxia-Telangiectasia Mutated (ATM) is a serine/threonine protein kinase principally known to orchestrate DNA repair processes upon DNA double-strand breaks (DSBs). Mutations in the Atm gene lead to Ataxia-Telangiectasia (AT), a recessive disorder characterized by ataxic movements consequent to cerebellar atrophy or dysfunction, along with immune alterations, genomic instability, and predisposition to cancer. AT patients show variable phenotypes ranging from neurologic abnormalities and cognitive impairments to more recently described neuropsychiatric features pointing to symptoms hardly ascribable to the canonical functions of ATM in DNA damage response (DDR). Indeed, evidence suggests that cognitive abilities rely on the proper functioning of DSB machinery and specific synaptic changes in central neurons of ATM-deficient mice unveiled unexpected roles of ATM at the synapse. Thus, in the present review, upon a brief recall of DNA damage responses, we focus our attention on the role of ATM in neuronal physiology and pathology and we discuss recent findings showing structural and functional changes in hippocampal and cortical synapses of AT mouse models. Collectively, a deeper knowledge of ATM-dependent mechanisms in neurons is necessary not only for a better comprehension of AT neurological phenotypes, but also for a higher understanding of the pathological mechanisms in neurodevelopmental and degenerative disorders involving ATM dysfunctions.

Polymorphisms in the Nonhomologous End-joining DNA Repair Pathway are Associated with HPV Integration in Cervical Dysplasia

Previous evidence indicates that human papillomavirus (HPV) integration status may be associated with cervical cancer development and progression. However, host genetic variation within genes that may play important roles in the viral integration process is understudied. The aim of this study was to examine the association between HPV16 and HPV18 viral integration status and SNPs in nonhomologous-end-joining (NHEJ) DNA repair pathway genes on cervical dysplasia. Women enrolled in two large trials of optical technologies for cervical cancer detection and positive for HPV16 or HPV18 were selected for HPV integration analysis and genotyping. Associations between SNPs and cytology (normal, low-grade, or high-grade lesions) were evaluated. Among women with cervical dysplasia, polytomous logistic regression models were used to evaluate the effect of each SNP on viral integration status. Of the 710 women evaluated [149 high-grade squamous intraepithelial lesion (HSIL), 251; low-grade squamous intraepithelial lesion (LSIL, 310 normal)], 395 (55.6%) were positive for HPV16 and 192 (27%) were positive for HPV18. Tag-SNPs in 13 DNA repair genes, including RAD50, WRN, and XRCC4, were significantly associated with cervical dysplasia. HPV16 integration status was differential across cervical cytology, but overall, most participants had a mix of both episomal and integrated HPV16. Four tag-SNPs in the XRCC4 gene were found to be significantly associated with HPV16 integration status. Our findings indicate that host genetic variation in NHEJ DNA repair pathway genes, specifically XRCC4, are significantly associated with HPV integration, and that these genes may play an important role in determining cervical cancer development and progression.

PREVENTION RELEVANCE

HPV integration in premalignant lesions and is thought to be an important driver of carcinogenesis. However, it is unclear what factors promote integration. The use of targeted genotyping among women presenting with cervical dysplasia has the potential to be an effective tool in assessing the likelihood of progression to cancer.

PRMT1 and PRMT5: on the road of homologous recombination and non-homologous end joining

DNA double-strand breaks (DSBs) are widely accepted to be the most deleterious form of DNA lesions that pose a severe threat to genome integrity. Two predominant pathways are responsible for repair of DSBs, homologous recombination (HR) and non-homologous end-joining (NHEJ). HR relies on a template to faithfully repair breaks, while NHEJ is a template-independent and error-prone repair mechanism. Multiple layers of regulation have been documented to dictate the balance between HR and NHEJ, such as cell cycle and post-translational modifications (PTMs). Arginine methylation is one of the most common PTMs, which is catalyzed by protein arginine methyltransferases (PRMTs). PRMT1 and PRMT5 are the predominate PRMTs that promote asymmetric dimethylarginine and symmetric dimethylarginine, respectively. They have emerged to be crucial regulators of DNA damage repair. In this review, we summarize current understanding and unaddressed questions of PRMT1 and PRMT5 in regulation of HR and NHEJ, providing insights into their roles in DSB repair pathway choice and the potential of targeting them for cancer therapy.

Radiation makes cells select the form of death dependent on external or internal exposure: apoptosis or pyroptosis

Internal radiation exposure from neutron-induced radioisotopes environmentally activated following atomic bombing or nuclear accidents should be considered for a complete picture of pathologic effects on survivors. Acute and localized high dose radiation exposure from hot particles taken into the body must induce cell death and severe damage to tissues, whether they are proliferating or not. However, very little the cellular and molecular mechanisms underlying this internal radiation pathology has been investigated. Male Wistar rats were internally exposed to ⁵⁶MnO₂ powder by inhalation. Small intestine samples were investigated by histological staining at acute phase (6 h, 3 days and 14 days) and late phase (2, 6 and 8 months) after the exposure. Histological location and chemical properties of the hot particles embedded in small intestinal tissues were analyzed by synchrotron radiation-X-ray fluorescence-X-ray absorption near-edge structure (SR-XRF-XANES). Hot particles located in the intestinal cavity were identified as accumulations of Mn and iron. Pathological changes showed evidence of crypt shortening, massive cell death at the position of stem cell zone, including apoptosis and pyroptosis from 6 h through 8 months in the internal exposed rats.

hGSuite HyperBrowser: A web-based toolkit for hierarchical metadata-informed analysis of genomic tracks

Many high-throughput sequencing datasets can be represented as objects with coordinates along a reference genome. Currently, biological investigations often involve a large number of such datasets, for example representing different cell types or epigenetic factors. Drawing overall conclusions from a large collection of results for individual datasets may be challenging and time-consuming. Meaningful interpretation often requires the results to be aggregated according to metadata that represents biological characteristics of interest. In this light, we here propose the hierarchical Genomic Suite HyperBrowser (hGSuite), an open-source extension to the GSuite HyperBrowser platform, which aims to provide a means for extracting key results from an aggregated collection of high-throughput DNA sequencing data. The hGSuite utilizes a metadata-informed data cube to calculate various statistics across the multiple dimensions of the datasets. With this work, we show that the hGSuite and its associated data cube methodology offers a quick and accessible way for exploratory analysis of large genomic datasets. The web-based toolkit named hGsuite Hyperbrowser is available at https://hyperbrowser.uio.no/hgsuite under a GPLv3 license.

PARP1 negatively regulates transcription of BLM through its interaction with HSP90AB1 in prostate cancer

BACKGROUND

Prostate cancer (PCa) is a prevalent malignant disease affecting a significant number of males globally. Elevated expression of the Bloom's syndrome protein (BLM) helicase has emerged as a promising cancer biomarker, being associated with the onset and progression of PCa. Nevertheless, the precise molecular mechanisms governing BLM regulation in PCa remain elusive.

METHODS

The expression of BLM in human specimens was analyzed using immnohistochemistry (IHC). A 5'-biotin-labeled DNA probe containing the promoter region of BLM was synthesized to pull down BLM promoter-binding proteins. Functional studies were conducted using a range of assays, including CCK-8, EdU incorporation, clone formation, wound scratch, transwell migration, alkaline comet assay, xenograft mouse model, and H&E staining. Mechanistic studies were carried out using various techniques, including streptavidin-agarose-mediated DNA pull-down, mass spectrometry (MS), immunofluorescence (IF), dual luciferase reporter assay system, RT-qPCR, ChIP-qPCR, co-immunoprecipitation (co-IP), and western blot.

RESULTS

The results revealed significant upregulation of BLM in human PCa tissues, and its overexpression was associated with an unfavorable prognosis in PCa patients. Increased BLM expression showed significant correlations with advanced clinical stage (P = 0.022) and Gleason grade (P = 0.006). In vitro experiments demonstrated that BLM knockdown exerted inhibitory effects on cell proliferation, clone formation, invasion, and migration. Furthermore, PARP1 (poly (ADP-ribose) polymerase 1) was identified as a BLM promoter-binding protein. Further investigations revealed that the downregulation of PARP1 led to increased BLM promoter activity and expression, while the overexpression of PARP1 exerted opposite effects. Through mechanistic studies, we elucidated that the interaction between PARP1 and HSP90AB1 (heat shock protein alpha family class B) enhanced the transcriptional regulation of BLM by counteracting the inhibitory influence of PARP1 on BLM. Furthermore, the combination treatment of olaparib with ML216 demonstrated enhanced inhibitory effects on cell proliferation, clone formation, invasion, and migration. It also induced more severe DNA damage in vitro and exhibited superior inhibitory effects on the proliferation of PC3 xenograft tumors in vivo.

CONCLUSIONS

The results of this study underscore the significance of BLM overexpression as a prognostic biomarker for PCa, while also demonstrating the negative regulatory impact of PARP1 on BLM transcription. The concurrent targeting of BLM and PARP1 emerges as a promising therapeutic approach for PCa treatment, holding potential clinical significance.

Roles of Oxidative Stress and Nrf2 Signaling in Pathogenic and Non-Pathogenic Cells: A Possible General Mechanism of Resistance to Therapy

The coordinating role of nuclear factor erythroid-2-related factor 2 (Nrf2) in cellular function is undeniable. Evidence indicates that this transcription factor exerts massive regulatory functions in multiple signaling pathways concerning redox homeostasis and xenobiotics, macromolecules, and iron metabolism. Being the master regulator of antioxidant system, Nrf2 controls cellular fate, influencing cell proliferation, differentiation, apoptosis, resistance to therapy, and senescence processes, as well as infection disease success. Because Nrf2 is the key coordinator of cell defence mechanisms, dysregulation of its signaling has been associated with carcinogenic phenomena and infectious and age-related diseases. Deregulation of this cytoprotective system may also interfere with immune response. Oxidative burst, one of the main microbicidal mechanisms, could be impaired during the initial phagocytosis of pathogens, which could lead to the successful establishment of infection and promote susceptibility to infectious diseases. There is still a knowledge gap to fill regarding the molecular mechanisms by which Nrf2 orchestrates such complex networks involving multiple pathways. This review describes the role of Nrf2 in non-pathogenic and pathogenic cells.

Molecular mechanisms of tumor resistance to radiotherapy

BACKGROUND

Cancer is the most prevalent cause of death globally, and radiotherapy is considered the standard of care for most solid tumors, including lung, breast, esophageal, and colorectal cancers and glioblastoma. Resistance to radiation can lead to local treatment failure and even cancer recurrence.

MAIN BODY

In this review, we have extensively discussed several crucial aspects that cause resistance of cancer to radiation therapy, including radiation-induced DNA damage repair, cell cycle arrest, apoptosis escape, abundance of cancer stem cells, modification of cancer cells and their microenvironment, presence of exosomal and non-coding RNA, metabolic reprogramming, and ferroptosis. We aim to focus on the molecular mechanisms of cancer radiotherapy resistance in relation to these aspects and to discuss possible targets to improve treatment outcomes.

CONCLUSIONS

Studying the molecular mechanisms responsible for radiotherapy resistance and its interactions with the tumor environment will help improve cancer responses to radiotherapy. Our review provides a foundation to identify and overcome the obstacles to effective radiotherapy.

Transmembrane nuclease NUMEN/ENDOD1 regulates DNA repair pathway choice at the nuclear periphery

Proper repair of DNA damage lesions is essential to maintaining genome integrity and preventing the development of human diseases, including cancer. Increasing evidence suggests the importance of the nuclear envelope in the spatial regulation of DNA repair, although the mechanisms of such regulatory processes remain poorly defined. Through a genome-wide synthetic viability screen for PARP-inhibitor resistance using an inducible CRISPR-Cas9 platform and BRCA1-deficient breast cancer cells, we identified a transmembrane nuclease (renamed NUMEN) that could facilitate compartmentalized and non-homologous end joining-dependent repair of double-stranded DNA breaks at the nuclear periphery. Collectively, our data demonstrate that NUMEN generates short 5' overhangs through its endonuclease and 3'→5' exonuclease activities, promotes the repair of DNA lesions-including heterochromatic lamina-associated domain breaks as well as deprotected telomeres-and functions as a downstream effector of DNA-dependent protein kinase catalytic subunit. These findings underline the role of NUMEN as a key player in DNA repair pathway choice and genome-stability maintenance, and have implications for ongoing research into the development and treatment of genome instability disorders.

Strategies for precise gene edits in mammalian cells

CRISPR-Cas technologies have the potential to revolutionize genetic medicine. However, work is still needed to make this technology clinically efficient for gene correction. A barrier to making precise genetic edits in the human genome is controlling how CRISPR-Cas-induced DNA breaks are repaired by the cell. Since error-prone non-homologous end-joining is often the preferred cellular repair pathway, CRISPR-Cas-induced breaks often result in gene disruption. Homology-directed repair (HDR) makes precise genetic changes and is the clinically desired pathway, but this repair pathway requires a homology donor template and cycling cells. Newer editing strategies, such as base and prime editing, can affect precise repair for relatively small edits without requiring HDR and circumvent cell cycle dependence. However, these technologies have limitations in the extent of genetic editing and require the delivery of bulky cargo. Here, we discuss the pros and cons of precise gene correction using CRISPR-Cas-induced HDR, as well as base and prime editing for repairing small mutations. Finally, we consider emerging new technologies, such as recombination and transposases, which can circumvent both cell cycle and cellular DNA repair dependence for editing the genome.

Unsupervised machine learning framework for discriminating major variants of concern during COVID-19

Due to the high mutation rate of the virus, the COVID-19 pandemic evolved rapidly. Certain variants of the virus, such as Delta and Omicron emerged with altered viral properties leading to severe transmission and death rates. These variants burdened the medical systems worldwide with a major impact to travel, productivity, and the world economy. Unsupervised machine learning methods have the ability to compress, characterize, and visualize unlabelled data. This paper presents a framework that utilizes unsupervised machine learning methods to discriminate and visualize the associations between major COVID-19 variants based on their genome sequences. These methods comprise a combination of selected dimensionality reduction and clustering techniques. The framework processes the RNA sequences by performing a k-mer analysis on the data and further visualises and compares the results using selected dimensionality reduction methods that include principal component analysis (PCA), t-distributed stochastic neighbour embedding (t-SNE), and uniform manifold approximation projection (UMAP). Our framework also employs agglomerative hierarchical clustering to visualize the mutational differences among major variants of concern and country-wise mutational differences for selected variants (Delta and Omicron) using dendrograms. We also provide country-wise mutational differences for selected variants via dendrograms. We find that the proposed framework can effectively distinguish between the major variants and has the potential to identify emerging variants in the future.

Establishing a genomic radiation-age association for space exploration supplements lung disease differentiation

Purpose

One possible way to quantify each individual's response or damage from ionizing radiation is to estimate their accelerated biological age following exposure. Since there is currently no definitive way to know if biological age estimations are accurate, we aim to establish a rad-age association using genomics as its foundation.

Methods

Two datasets were combined and used to empirically find the age cutoff between young and old patients. With age as both a categorical and continuous variable, two other datasets that included radiation exposure are used to test the interaction between radiation and age. The gene lists are oriented in preranked lists for both pathway and diseases analysis. Finally, these genes are used to evaluate another dataset on the clinical relevance in differentiating lung disease given ethnicity and sex using both pairwise t-tests and linear models.

Results

Using 12 well-known genes associated with aging, a threshold of 29-years-old was found to be the difference between young and old patients. The two interaction tests yielded 234 unique genes such that pathway analysis flagged IL-1 signaling and PRPP biosynthesis as significant with high cell proliferation diseases and carcinomas being a common trend. LAPTM4B was the only gene with significant interaction among lung disease, ethnicity, and sex, with fold change greater than two.

Conclusion

The results corroborate an initial association between radiation and age, given inflammation and metabolic pathways and multiple genes emphasizing mitochondrial function, oxidation, and histone modification. Being able to tie rad-age genes to lung disease supplements future work for risk assessment following radiation exposure.

A graph neural network-based interpretable framework reveals a novel DNA fragility-associated chromatin structural unit

BACKGROUND

DNA double-strand breaks (DSBs) are among the most deleterious DNA lesions, and they can cause cancer if improperly repaired. Recent chromosome conformation capture techniques, such as Hi-C, have enabled the identification of relationships between the 3D chromatin structure and DSBs, but little is known about how to explain these relationships, especially from global contact maps, or their contributions to DSB formation.

RESULTS

Here, we propose a framework that integrates graph neural network (GNN) to unravel the relationship between 3D chromatin structure and DSBs using an advanced interpretable technique GNNExplainer. We identify a new chromatin structural unit named the DNA fragility-associated chromatin interaction network (FaCIN). FaCIN is a bottleneck-like structure, and it helps to reveal a universal form of how the fragility of a piece of DNA might be affected by the whole genome through chromatin interactions. Moreover, we demonstrate that neck interactions in FaCIN can serve as chromatin structural determinants of DSB formation.

CONCLUSIONS

Our study provides a more systematic and refined view enabling a better understanding of the mechanisms of DSB formation under the context of the 3D genome.

USP7 reduction leads to developmental failure of mouse early embryos

As a member of Ubiquitin-specific protease subfamily, ubiquitin specific protease 7 (USP7) has been reported to participate in a variety of cellular processes, including cell cycle, apoptosis, DNA damage response, and epigenetic modification. However, its function in preimplantation embryos is still obscure. To investigate the functions of USP7 during preimplantation embryo development, we used siRNA to degrade endogenous USP7 messenger RNA. We found that USP7 knockdown significantly decreased the development rate of mouse early embryos. Moreover, depletion of USP7 induced the accumulation of the DNA lesions and apoptotic blastomeres in early embryos. In addition, USP7 knockdown caused an abnormal H3K27me3 modification in 2-cell embryos. Overall, our results indicate that USP7 maintains genome stability perhaps via regulating H3K27me3 and DNA damage, consequently controlling the embryo quality.

Elucidation of Increased Cervical Cancer Risk Due to Polymorphisms in XRCC1 (R399Q and R194W), ERCC5 (D1104H), and NQO1 (P187S)

Genetic variations like single nucleotide polymorphisms (SNPs) are associated with cervical carcinogenesis. In this study, SNPs have been identified that contribute toward changes in the function and stability of the proteins and show association with cervical cancer. Initially, literature mining identified 114 protein-coding polymorphisms with population-based evidence in cervical cancer. Subsequently, the functional assessment was performed using sequence-dependent tools, and thereafter, protein stability was analyzed using sequence and structural data. Twenty-three non-synonymous SNPs (nsSNPs) found to be damaging and destabilizing were then analyzed to check their risk association at the population level. The meta-analysis indicated that polymorphisms in DNA damage repair genes XRCC1 (rs25487 and rs1799782), ERCC5 (rs17655), and oxidative stress-related gene NQO1 (rs1800566) are significantly associated with increased cervical cancer risk. The XRCC1 rs25487 and rs1799782 polymorphisms showed the highest risk of cervical cancer in the homozygous model having odds ratio (OR) = 1.85, 95% confidence interval (CI) = 1.17-2.92, p = 0.01, and recessive model with OR = 1.81, 95% CI = 1.01-3.24, and p = 0.04 respectively. Similarly, rs17655 polymorphism of ERCC5 and rs1800566 polymorphism of NQO1 showed the highest pooled OR in the homozygous (OR = 1.70, 95% CI = 1.32-2.19, p = 0.00004) and heterozygous model (OR = 1.3, 95% CI = 1.06-1.58, p = 0.01) respectively. Thus, in this study, a comprehensive collection of nsSNPs was collated and assessed, leading to the identification of polymorphisms in DNA damage repair and oxidative stress-related genes, that destabilize the protein and shows increased risk associated with cervical cancer.

RBBP4 regulates the expression of the Mre11-Rad50-NBS1 (MRN) complex and promotes DNA double-strand break repair to mediate glioblastoma chemoradiotherapy resistance

For treatment of glioblastoma (GBM), temozolomide (TMZ) and radiotherapy (RT) exert antitumor effects by inducing DNA double-strand breaks (DSBs), mainly via futile DNA mismatch repair (MMR) and inducing apoptosis. Here, we provide evidence that RBBP4 modulates glioblastoma resistance to chemotherapy and radiotherapy by recruiting transcription factors and epigenetic regulators that bind to their promoters to regulate the expression of the Mre11-Rad50-NBS1(MRN) complex and the level of DNA-DSB repair, which are closely associated with recovery from TMZ- and radiotherapy-induced DNA damage in U87MG and LN229 glioblastoma cells, which have negative MGMT expression. Disruption of RBBP4 induced GBM cell DNA damage and apoptosis in response to TMZ and radiotherapy and enhanced radiotherapy and chemotherapy sensitivity by the independent pathway of MGMT. These results displayed a possible chemo-radioresistant mechanism in MGMT negative GBM. In addition, the RBBP4-MRN complex regulation axis may provide an interesting target for developing therapy-sensitizing strategies for GBM.

The Promise of Nanoparticles-Based Radiotherapy in Cancer Treatment

Radiation has been utilized for a long time for the treatment of cancer patients. However, radiotherapy (RT) has many constraints, among which non-selectivity is the primary one. The implementation of nanoparticles (NPs) with RT not only localizes radiation in targeted tissue but also provides significant tumoricidal effect(s) compared to radiation alone. NPs can be functionalized with both biomolecules and therapeutic agents, and their combination significantly reduces the side effects of RT. NP-based RT destroys cancer cells through multiple mechanisms, including ROS generation, which in turn damages DNA and other cellular organelles, inhibiting of the DNA double-strand damage-repair system, obstructing of the cell cycle, regulating of the tumor microenvironment, and killing of cancer stem cells. Furthermore, such combined treatments overcome radioresistance and drug resistance to chemotherapy. Additionally, NP-based RT in combined treatments have shown synergistic therapeutic benefit(s) and enhanced the therapeutic window. Furthermore, a combination of phototherapy, i.e., photodynamic therapy and photothermal therapy with NP-based RT, not only reduces phototoxicity but also offers excellent therapeutic benefits. Moreover, using NPs with RT has shown promise in cancer treatment and shown excellent therapeutic outcomes in clinical trials. Therefore, extensive research in this field will pave the way toward improved RT in cancer treatment.

Aging Hallmarks and the Role of Oxidative Stress

Aging is a complex biological process accompanied by a progressive decline in the physical function of the organism and an increased risk of age-related chronic diseases such as cardiovascular diseases, cancer, and neurodegenerative diseases. Studies have established that there exist nine hallmarks of the aging process, including (i) telomere shortening, (ii) genomic instability, (iii) epigenetic modifications, (iv) mitochondrial dysfunction, (v) loss of proteostasis, (vi) dysregulated nutrient sensing, (vii) stem cell exhaustion, (viii) cellular senescence, and (ix) altered cellular communication. All these alterations have been linked to sustained systemic inflammation, and these mechanisms contribute to the aging process in timing not clearly determined yet. Nevertheless, mitochondrial dysfunction is one of the most important mechanisms contributing to the aging process. Mitochondria is the primary endogenous source of reactive oxygen species (ROS). During the aging process, there is a decline in ATP production and elevated ROS production together with a decline in the antioxidant defense. Elevated ROS levels can cause oxidative stress and severe damage to the cell, organelle membranes, DNA, lipids, and proteins. This damage contributes to the aging phenotype. In this review, we summarize recent advances in the mechanisms of aging with an emphasis on mitochondrial dysfunction and ROS production.

Ku-DNA binding inhibitors modulate the DNA damage response in response to DNA double-strand breaks

The DNA-dependent protein kinase (DNA-PK) plays a critical role in the DNA damage response (DDR) and non-homologous end joining (NHEJ) double-strand break (DSB) repair pathways. Consequently, DNA-PK is a validated therapeutic target for cancer treatment in certain DNA repair-deficient cancers and in combination with ionizing radiation (IR). We have previously reported the discovery and development of a novel class of DNA-PK inhibitors with a unique mechanism of action, blocking the Ku 70/80 heterodimer interaction with DNA. These Ku-DNA binding inhibitors (Ku-DBi's) display nanomolar activity in vitro, inhibit cellular DNA-PK, NHEJ-catalyzed DSB repair and sensitize non-small cell lung cancer (NSCLC) cells to DSB-inducing agents. In this study, we demonstrate that chemical inhibition of the Ku-DNA interaction potentiates the cellular effects of bleomycin and IR via p53 phosphorylation through the activation of the ATM pathway. This response is concomitant with a reduction of DNA-PK catalytic subunit (DNA-PKcs) autophosphorylation at S2056 and a time-dependent increase in H2AX phosphorylation at S139. These results are consistent with Ku-DBi's abrogating DNA-PKcs autophosphorylation to impact DSB repair and DDR signaling through a novel mechanism of action, and thus represent a promising anticancer therapeutic strategy in combination with DNA DSB-inducing agents.

CRISPR-Cas9 base editors and their current role in human therapeutics

BACKGROUND

Consistent progress has been made to create more efficient and useful CRISPR-Cas9-based molecular toolsfor genomic modification.

METHODS

This review focuses on recent articles that have employed base editors (BEs) for both clinical and research purposes.

RESULTS

CRISPR-Cas9 BEs are a useful system because of their highefficiency and broad applicability to gene correction and disruption. In addition, base editing has beensuggested as a safer approach than other CRISPR-Cas9-based systems, as it limits double-strand breaksduring multiplex gene knockout and does not require a toxic DNA donor molecule for genetic correction.

CONCLUSION

As such, numerous industry and academic groups are currently developing base editing strategies withclinical applications in cancer immunotherapy and gene therapy, which this review will discuss, with a focuson current and future applications of in vivo BE delivery.