Modulation Of DNA Damage Response Research Articles

Tricarboxylic Acid Cycle Relationships with Non-Metabolic Processes: A Short Story with DNA Repair and Its Consequences on Cancer Therapy Resistance.

Metabolic changes involving the tricarboxylic acid (TCA) cycle have been linked to different non-metabolic cell processes. Among them, apart from cancer and immunity, emerges the DNA damage response (DDR) and specifically DNA damage repair. The oncometabolites succinate, fumarate and 2-hydroxyglutarate (2HG) increase reactive oxygen species levels and create pseudohypoxia conditions that induce DNA damage and/or inhibit DNA repair. Additionally, by influencing DDR modulation, they establish direct relationships with DNA repair on at least four different pathways. The AlkB pathway deals with the removal of N-alkylation DNA and RNA damage that is inhibited by fumarate and 2HG. The MGMT pathway acts in the removal of O-alkylation DNA damage, and it is inhibited by the silencing of the MGMT gene promoter by 2HG and succinate. The other two pathways deal with the repair of double-strand breaks (DSBs) but with opposite effects: the FH pathway, which uses fumarate to help with the repair of this damage, and the chromatin remodeling pathway, in which oncometabolites inhibit its repair by impairing the homologous recombination repair (HRR) system. Since oncometabolites inhibit DNA repair, their removal from tumor cells will not always generate a positive response in cancer therapy. In fact, their presence contributes to longer survival and/or sensitization against tumor therapy in some cancer patients.

Pilot study of CBX-12 pharmacodynamics in patients with advanced solid tumors.

TPS3187 Background: Topoisomerase 1 (TOP1) inhibitors effectively kill a diverse range of tumor cells but have limited clinical utility due to severe off-target toxicities. Targeted therapeutic strategies have been developed to circumvent these limitations, although there remains an unmet need for antigen-agnostic tumor targeting. CBX-12 is a peptide conjugate that uses a novel pH-low insertion peptide (pHLIP) linked to TOP1 inhibitor exatecan to selectively target the low-pH tumor microenvironment and deliver the payload intracellularly. Recently published results of the first-in-human study of CBX-12 (NCT04902872) demonstrated single-agent activity in 4 patients, including a complete response in a patient with ovarian cancer. The predominant reported toxicity was myelosuppression with the most common grade 3/4 treatment-related adverse event being neutropenia in 28.6% of patients. Here we report our new pharmacodynamic (PD) biomarker-driven pilot study of CBX-12 in patients with advanced solid tumors. The primary objective of this study is to assess the effects of CBX-12 on biomarkers of DNA damage response (DDR) in biopsy specimen to establish the degree and duration of CBX-12 target engagement. The secondary objectives are to assess the effects of CBX-12 on TOP1 molecular response; determine any association between tumor TOP1 levels, DDR modulation, and plasma exatecan levels; evaluate the effect of CBX-12 on CD8+ T cell infiltration and activation in the tumor microenvironment; assess the objective response rate using RECIST v 1.1; and assess safety and tolerability of CBX-12. The planned PD endpoints aim to confirm and further enrich knowledge of the mechanisms underlying response or resistance to CBX-12 treatment, and guide future complementary treatment combination strategies. The study results may also help identify future patient populations likely to benefit from CBX-12 treatment. Methods: CBX-12 will be administered intravenously once weekly in 28-day cycles at the recommended phase 2 dose. Mandatory biopsies will be collected at baseline, 24-36 hours post first dose, and on cycle 3 day 1 to assess both short- and long-term effects of CBX-12 on the tumor. Mandatory research blood samples will be collected at specified timepoints for pharmacokinetic, circulating tumor cell, and cell-free DNA analyses. Clinical trial information: NCT05691517 .

Modulating DNA damage response in uveal melanoma through embryonic stem cell microenvironment

BackgroundUveal melanoma (UVM) is the most common primary intraocular tumor in adults, with a median survival of 4–5 months following metastasis. DNA damage response (DDR) upregulation in UVM, which could be linked to its frequent activation of the PI3K/AKT pathway, contributes to its treatment resistance. We have reported that embryonic stem cell microenvironments (ESCMe) can revert cancer cells to less aggressive states through downregulation of the PI3K signaling, showing promise in modulating the DDR of UVM.MethodsSince nonhomologous end joining (NHEJ) is the main DNA repair mechanism in UVM, this study utilized gene expression analysis and survival prognosis analysis to investigate the role of NHEJ-related genes in UVM based on public databases. Xenograft mouse models were established to assess the therapeutic potential of ESC transplantation and exposure to ESC-conditioned medium (ESC-CM) on key DNA repair pathways in UVM. Quantitative PCR and immunohistochemistry were used to analyze NHEJ pathway-related gene expression in UVM and surrounding normal tissues. Apoptosis in UVM tissues was evaluated using the TUNEL assay.ResultsPRKDC, KU70, XRCC5, LIG4 and PARP1 showed significant correlations with UM progression. High expression of PRKDC and XRCC5 predicted poorer overall survival, while low PARP1 and XRCC6 expression predicted better disease-free survival in UVM patients. ESCMe treatment significantly inhibited the NHEJ pathway transcriptionally and translationally and promoted apoptosis in tumor tissues in mice bearing UVM. Furthermore, ESC transplantation enhanced DDR activities in surrounding normal cells, potentially mitigating the side effects of cancer therapy. Notably, direct cell-to-cell contact with ESCs was more effective than their secreted factors in regulating the NHEJ pathway.ConclusionsOur results suggest that NHEJ-related genes might serve as prognostic markers and therapeutic targets in UVM. These findings support the therapeutic potential of ESC-based therapy in enhancing UVM sensitivity to radiochemotherapy and improving treatment outcomes while minimizing damage to healthy cells.

Abstract LB015: Differential expression of deubiquitinating enzymes and its related DNA damage response genes in neuroblastoma heterogeneity

Abstract SK-N-AS and SK-N-DZ are two cell lines of pediatric solid tumors neuroblastomas well characterized to evaluate heterogeneity between different neuroblastomas and are presumed as models for differences between different neuroblastoma. Using this model system, we recently evaluated if radiation could improve efficacy of radiation therapy and to follow these studies later with animal models to determine decrease of tumor burden. Differences between the N-type and S-type neuroblastoma cell lines SK-N-DZ and SK-N-AS, respectively were observed to be high and their responses to radiation stress were equally heterogeneous. Ubiquitin signaling plays a key role during the DNA damage response in protein recruitment and protein interactions. Deubiquitinating enzymes (DUBs) deconjugate ubiquitin from ubiquitylated substrate proteins to control their activity and stability and are shown to regulate various biological processes. DUBs may play a role in regulating the radiosensitivity of cancer cells by modulating DNA damage response and repair pathways. Determination of specific DUBs that are involved in regulating radiosensitivity in cancer cells will provide opportunity for drug targeting and visa-vis enhance the efficacy of radiation therapy in neuroblastoma cancer treatment. Here, using bioinformatic tools, the differentially regulated DUBs were identified. The relationship between DEGs-DUBs with the genes involved in various DNA repair pathways (NHEJ, HR and Fanconi anemia pathway; KEGG pathway database) are described. We identified 32 DEGs (14 upregulated and 18 downregulated) with these neuroblastoma cell lines. USP22 and USP41 DUBs and its differential expression in these cell lines denotes the importance of such analysis. Especially considering USP22 a potentially biomarker for predicting the outcome of patients with neuroblastoma. These DEG-DUBs were likewise correlated with 91 DNA damage response (DDR) genes belonging to three different pathways (NHEJ, HR and Fanconi anemia pathway). Out of which 44 of the DDR genes showed significant correlation with DEG-DUBs. Further studies are needed to determine the mechanisms underlying the complex relationship of these DUBs and to determine the critical DUBs for drug targeting and to enhance the efficacy of radiation therapy in cancer treatment. Citation Format: Vaibhav Vaibhav, Fahika Nazeerulla, Tatjana Paunesku, Ekta Tripathi, Gayle Woloschak, Prashanthi Karyala, Rao V. Papineni. Differential expression of deubiquitinating enzymes and its related DNA damage response genes in neuroblastoma heterogeneity [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 2 (Late-Breaking, Clinical Trial, and Invited Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(7_Suppl):Abstract nr LB015.

Abstract LB270: VRTX531, a potent and selective inhibitor of USP1 for treatment of BRAC1/2mut and HRD+ cancers

Abstract Tumors characterized by deficiencies in DNA double-strand break (DSB) repair mechanisms, such as those harboring mutations in BRCA1/2, are commonly addressed through the administration of poly (ADP-ribose) polymerase-1 (PARP1) inhibitors or platinum-based chemotherapy. While these treatments offer clinical advantages, a significant number of patients eventually develop resistance, underscoring the necessity for innovative therapeutic strategies. USP1 belongs to the ubiquitin-specific processing (UBP) family of proteases, playing a pivotal role in modulating DNA damage response (DDR) pathways. VRTX531 is a novel potent, selective and allosteric inhibitor of USP1 with an IC50 of <50 nm in tested across a broad range of tumor lineages including MDAMB-436 and cell lines and UWB1.289. VRTX531, compound induces cell death through a pathway that is distinct from PARP inhibitors and compound demonstrates robust synergy when combined with first- or second-generation PARP inhibitors. Moreover, the compound exhibited profound activity alone and in combination with PARP inhibitor in BRCA1/2 mut and HRD+ tumors. VRTX531 exhibited exemplary pharmacokinetics and safety in preclinical studies and is expected to enter preclinical testing in H1, 2024. VRTX531 is being evaluated as a single agent and in combination with PARP1 inhibitor in patients with BRCA1/2 mut or HRD+ tumors that are naïve to PARP inhibitors and with prior PARP inhibitor history. Citation Format: Uday Kumar Surampudi, Prashant Kashinath Bhavar. VRTX531, a potent and selective inhibitor of USP1 for treatment of BRAC1/2mut and HRD+ cancers [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 2 (Late-Breaking, Clinical Trial, and Invited Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(7_Suppl):Abstract nr LB270.

Aging-Associated ALKBH5-m6A Modification Exacerbates Doxorubicin-Induced Cardiomyocyte Apoptosis Via AT-Rich Interaction Domain 2.

Chemotherapy-induced cardiovascular disease is a growing concern in the elderly population who have survived cancer, yet the underlying mechanism remains poorly understood. We investigated the role of ALKBH5 (AlkB homolog 5), a primary N6-methyladenosine (m6A) demethylase, and its involvement in m6A methylation-mediated regulation of targets in aging-associated doxorubicin-induced cardiotoxicity. To validate the relationship between doxorubicin-induced cardiotoxicity and aging, we established young and old male mouse models. ALKBH5 expression was modulated through adeno-associated virus 9 (in vivo), Lentivirus, and siRNAs (in vitro) to examine its impact on cardiomyocyte m6A modification, doxorubicin-induced cardiac dysfunction, and remodeling. We performed mRNA sequencing, methylated RNA immunoprecipitation sequencing, and molecular assays to unravel the mechanism of ALKBH5-m6A modification in doxorubicin-induced cardiotoxicity. Our data revealed an age-dependent increase in doxorubicin-induced cardiac dysfunction, remodeling, and injury. ALKBH5 expression was elevated in aging mouse hearts, leading to reduced global m6A modification levels. Through mRNA sequencing and methylated RNA immunoprecipitation sequencing analyses, we identified ARID2 (AT-rich interaction domain 2) as the downstream effector of ALKBH5-m6A modulation in cardiomyocytes. Further investigations revealed that ARID2 modulates DNA damage response and enhances doxorubicin-induced cardiomyocyte apoptosis. Our findings provide insights into the role of ALKBH5-m6A modification in modulating doxorubicin-induced cardiac dysfunction, remodeling, and cardiomyocyte apoptosis in male mice. These results highlight the potential of ALKBH5-targeted treatments for elderly patients with cancer in clinical settings.

Abstract C146: VIC-1911, a selective Aurora kinase A inhibitor, synergizes with sacituzumab govitecan in triple-negative breast cancer

Abstract BACKGROUND: Triple-negative breast cancer (TNBC) accounts for 15-20% of breast cancer cases and 30-40% of U.S. breast cancer deaths. Although current precision treatments improve TNBC patient outcomes, TNBC heterogeneity has led to therapeutic targeting challenges. Also, the resistance of TNBC to conventional treatment remains a significant clinical problem. Therefore, informed evaluation of new targets can improve the treatment of TNBC, representing an unmet need. Dysregulation of the cell cycle is a hallmark of cancer for unlimited proliferation. Abnormal mitosis and cell-cycle checkpoints are crucial in leading to aneuploidy and genetic instability. Aurora kinase A (AURKA), a serine/threonine kinase, regulates mitosis in the early stages (G2/M phase) by regulating centrosome maturation and disjunction, thereby establishing a bipolar mitotic spindle. VIC-1911 (previously known as TAS-119), a novel, orally active, highly selective inhibitor of AURKA with a low toxicity profile, suppresses the growth of various cancer cell lines in vitro and in vivo. As AURKA can modulate DNA damage response, we hypothesized that VIC-1911 combined with sacituzumab govitecan (SG), which has a topoisomerase 1 inhibitor as a payload, has a synergistic antitumor effect on TNBC. MATERIALS AND METHODS: To evaluate the short-term in vitro efficacy of VIC-1911 alone and combination with SG, a sulforhodamine B cell proliferation assay was performed using 10 TNBC cell lines. For long-term treatment conditions, a colony formation assay was conducted. Western blot and immunofluorescent analyses were conducted to confirm treatment-mediated DNA damage and apoptosis. Human TNBC cell line–derived mammary fat pad xenograft models were used to evaluate the antitumor effect of VIC-1911 and SG. RESULTS: In vitro proliferation, data demonstrated that single-agent VIC-1911 had a nanomolar to micromolar range of half-maximal inhibitory concentrations (2.69 nM to 10.6 mM) in the tested TNBC cell lines. The half-maximal inhibitory concentration was correlated with c-Myc expression (R2=0.4876, p=0.0247). Exposure to the combination of VIC-1911 and SG led to significant death of VIC-1911–sensitive TNBC cell lines (p<0.05). Western blot and immunofluorescent analysis revealed that VIC-1911 and SG combination caused TNBC cell death by inducing expression of phosphorylated histone H2AX (DNA damage marker) and cleaved poly (ADP-ribose) polymerase (apoptosis marker). Furthermore, the combination of VIC-1911 and SG had significantly greater antitumor efficacy than did either agent alone in SUM149 TNBC xenograft models (tumor growth inhibition rate (TGI): VIC-1911, 61.4%; SG, 68.3%; combination, 82.9%; p<0.01) and HCC1806 TNBC xenograft models (TGI: VIC-1911, 49.3%; SG, 66.3%; combination, 85.9%; p<0.01). CONCLUSION: The AURKA inhibitor VIC-1911 has a synergistic antitumor effect with SG by inducing DNA damage in TNBC cells. PDX and additional mechanistic studies are planned to further evaluate VIC-1911 and SG as novel combination therapy for TNBC. Citation Format: Jangsoon Lee, YoungJin Gi, Thomas Myers, Linda Paradiso, Debu Tripathy, Naoto T. Ueno. VIC-1911, a selective Aurora kinase A inhibitor, synergizes with sacituzumab govitecan in triple-negative breast cancer [abstract]. In: Proceedings of the AACR-NCI-EORTC Virtual International Conference on Molecular Targets and Cancer Therapeutics; 2023 Oct 11-15; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2023;22(12 Suppl):Abstract nr C146.

Fusobacterium nucleatum facilitates proliferation and autophagy by activating miR-361-3p/NUDT1 axis through oxidative stress in hypopharyngeal squamous cell carcinoma

BackgroundTo investigate how Fusobacterium nucleatum (Fn) promotes oxidative stress and mediates proliferation and autophagy in hypopharyngeal squamous cell carcinoma (HPSCC).MethodsThe prognosis for 82 HPSCC cases was retrospectively analyzed. HPSCC cell line FaDu was co-cultured with Fn. Knockdown of NUDT1 (shNUDT1 group) was done after observing DNA damage response. CCK8 and tumorigenesis assays for proliferation observation, mitochondria ROS (MitoROS) measurement to examine intracellular oxidative stress, and ELISA to analyze concentration of 8-oxo-2’-deoxyguanosine (8-oxo-dG) in cells. Dual-luciferase reporter assays clarified miR-361-3p connection with NUDT1. Autophagy flow was observed using electron microscopy and related proteins.ResultsFn was highly associated with NUDT1. The shNUDT1 group experienced lower proliferation compared with normal FaDu (NC group) in vivo and in vitro. The shNUDT1 group showed 8-oxo-dG and γH2AX to be elevated. Intracellular ROS decreased in shNUDT1Fn group when compared to Fn group. Upregulating miR-361-3p could suppress NUDT1 expression and downstream proliferation and autophagy. Fn modulated miR-361-3p via OH−, which could be proven by H2O2 assay and N-acetylcysteine.ConclusionsHigher Fn in HPSCC patients suggests poorer prognosis. NUDT1 might affect cell proliferation and autophagy and modulate DNA damage response. The oxidative stress induced miR-361-3p/NUDT1 axis is first introduced in microbiome-carcinoma research.

Multimerin 1 aids in the progression of ovarian cancer possibly via modulation of DNA damage response and repair pathways.

Ovarian cancer is one of the leading causes of deaths among women. Despite advances in the treatment regimes, a high rate of diagnosis in the advanced stage makes it almost an incurable malignancy. Thus, more research efforts are required to identify potential molecular markers for early detection of the disease and therapeutic targets to augment the survival rate of ovarian cancer patients. Previously, in this context, we identified dysregulated expression of multimerin 1 (MMRN1) in ovarian cancer. To elucidate the relationship between MMRN1 expression and ovarian cancer progression, siRNA-based MMRN1 knockdown was employed and various cell assays were performed to study its effect on ovarian cancer cells. In addition, network of dysregulated proteins was identified by quantitative proteomics and associated pathways were explored by bioinformatics analysis. MMRN1 silencing showed a significant reduction in cell viability, adhesion, migration, and invasion and a high frequency of cell apoptosis. Label-free quantitative proteomics and in-depth statistical analysis identified 448 dysregulated proteins, majority of which were overexpressed in MMRN1 knockdown cells. The pathways overrepresented in ovarian cancer were DNA replication, mismatch repair, nucleotide excision repair, and cell cycle regulation. Conclusively, the findings of this study suggest that MMRN1 aids in the progression of ovarian cancer via modulation of DNA damage response and repair pathways.

The modulatory effects of two bioflavonoids, quercetin and thymoquinone on the expression levels of DNA damage and repair genes in human breast, lung and prostate cancer cell lines.

The recent decade has witnessed the increasing potential of various flavonoids such as quercetin and thymoquinone in inhibiting cancer cells proliferation and growth and their therapeutic effects in various cancers. Therefore, in the current study, we aim to evaluate the expression levels of key factors of DNA damage response in human breast, lung and prostate cancer cell lines in response to treatment with quercetin and thymoquinone. MTT assay was applied to assess the effects of quercetin and thymoquinone on the viability of MCF-7, A549, and PC3 cancer cells. Quantitative reverse transcription-polymerase chain reaction (qRT-PCR) was used to evaluate the expression levels of p53, RAD51, Ku70, XRCC1, and H2AX in treated cells. In addition, the expression rate of 8-hydroxy-deoxyguanosine (8-OH-dG) was assessed by ELISA kit. The quercetin and thymoquinone induce cytotoxicity in breast, lung, and prostate cancer cells effectively; MCF-7 cells were the most sensitive cells to quercetin with an IC50 value of 50μM and PC3 cells were more sensitive to thymoquinone with an IC50 value of 20μM. The expression levels of DNA damage markers, H2AX, and 8-OH-dG were significantly increased in all cancer cells treated with quercetin and thymoquinone (p<0.05). Moreover, both flavonoids significantly decreased the expression levels of DNA repair mediators, RAD51, Ku70, XRCC1, in cell lines. P53 was also increased in MCF-7 and A549 cells. We concluded that quercetin and thymoquinone may exert their effects through modulation of DNA damage response, increasing DNA damage, and suppressing DNA repair genes.

An Evidence Based Reporting System for Molecular Tumorboards Identifies Novel Therapeutics for T-Cell Lymphomas

Introduction Peripheral T-cell lymphomas (PTCLs) exhibit significant diagnostic and therapeutic challenges. Following current treatment guidelines, the majority of patients either do not achieve a remission or experience an early relapse with fatal outcome. Hence, development of innovative therapeutic strategies targeting the underlying biology of PTCLs is highly demanded. To identify novel therapeutic options for PTCL, we here compiled a comprehensive database of genetic alterations in T-cell lymphomas and utilized bioinformatic methodology for evidence-based reporting of treatment options in the context of molecular tumorboards. Methods Utilizing newly developed bioinformatic methodology for molecular tumorboards1,2, genetic data from >1800 patients with T-cell lymphomas (TCL) compiled from public available sources were analyzed and queried for potential therapeutics addressing genetic alterations in TCL. Based on the results of this approach, a broad in vitro drug screening was performed to assess the activity of potential therapeutics in genetically and transcriptionally characterized cell lines of TCL and address potential biomarkers of response and resistance. Furthermore, functional apoptosis profiling, combination drug screening and mechanistic work up was performed to identify and mechanistically explore novel drug combinations. Results Integration of genetic alterations and drug sensitivity screens revealed novel therapeutic strategies for PTCL. Notably, multiple components of DNA damage response pathways were suggested as therapeutic targets, most prominently the cell cycle regulator WEE1. Indeed, the clinical-grade WEE1 kinase inhibitor, adavosertib, potently induced premature mitotic entry, accumulation of DNA damage and induction of apoptosis in PTCL cell lines, predominantly in cell line models harboring genetic alterations in the ATR signaling pathway. To further enhance the therapeutic effects of WEE1 inhibition, we explored potential combination strategies through mechanistic studies and functional apoptosis profiling. Here, we identified synergistic effects in DNA damage response pathways, cell cycle regulation and modulation of anti-apoptotic proteins through combined WEE1 and JAK/STAT inhibition. Indeed, the combination of adavosertib and ruxolitinib showed marked synergistic cytotoxicity in vitro in genetically characterized subsets of T-cell lymphoma. Conclusions Our results identified WEE1 as a promising therapeutic target for genetically defined PTCL subgroups. Furthermore, mechanistic studies identified concepts for rational combination strategies of WEE1 and JAK/STAT inhibition through modulation of DNA-damage response and priming for apoptosis.

Abstract 1513: FASN inhibition-induced BRCAness as a therapeutic option for castration-resistant prostate cancer (CRPC)

Abstract Androgen deprivation therapy (ADT) is the primary treatment for prostate cancer. However, resistance to ADT invariably develops, leading to castration-resistant prostate cancer (CRPC). Prostate cancer progression is marked by overexpression of fatty acid synthase (FASN) and increased de novo synthesis of fatty acids. Importantly, the majority of normal tissues have low expression of FASN and rely mostly on exogenous lipids, making FASN an interesting therapeutic target for prostate cancer. Previously our group evaluated the effects of inhibiting FASN in prostate cancer, with especially promising results in CRPC models. We observed that FASN inhibition decreases DNA damage repair capability by transcriptionally modulating homologous recombination (BRCAness) and non-homologous end joining repair pathways, which leads to increased DNA damage and apoptosis. Key enzymes involved in DNA repair pathways are reduced at the protein level, and the addition of exogenous palmitate, the product of FASN, is able to rescue their expression to normal levels. Interestingly, genes involved in the synthesis of ceramide are upregulated after FASN blockade, with consequent increased cellular levels of ceramides, dihydroceramides and sphingomyelin. Additionally, we observed increased acyl chain unsaturation levels in these lipid species, in line with the uptake of polyunsaturated fatty acids (PUFA) observed when de novo lipogenesis is blocked. The inhibition of ceramide synthesis, both through genetic knock-down with siRNA or pharmacologically with an inhibitor of serine palmitoyltransferase, is capable of partially rescuing the DNA damage induced by FASN inhibition, suggesting a role of ceramides in DNA damage response modulation. Next, we investigated the synergistic effect of combining FASN inhibitor with PARP inhibitor and observed a higher inhibition of cell growth in prostate cancer cell lines in comparison to either drug alone. Human CRPC organoids when treated with PARP and FASN inhibitor in combination showed reduced diameter, as well as reduced cell proliferation, when compared with each agent alone. Overall, our data demonstrate that targeting de novo lipogenesis can increase the therapeutic efficacy of PARP inhibitors and benefit prostate cancer patients that do not harbor BRCA mutations, by pharmacologically downregulating DNA damage repair pathways, particularly HR. Citation Format: Caroline Fidalgo Ribeiro, Silvia D. Rodrigues, Debora C. Bastos, Hubert Pakula, Giorgia Zadra, Marco Foiani, Massimo Loda. FASN inhibition-induced BRCAness as a therapeutic option for castration-resistant prostate cancer (CRPC) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 1513.

Zinc Prevents DNA Damage in Normal Cells but Shows Genotoxic and Cytotoxic Effects in Acute Myeloid Leukemia Cells.

Genomic instability is prevented by the DNA damage response (DDR). Micronutrients, like zinc (Zn), are cofactors of DDR proteins, and micronutrient deficiencies have been related to increased cancer risk. Acute myeloid leukemia (AML) patients commonly present Zn deficiency. Moreover, reports point to DDR defects in AML. We studied the effects of Zn in DDR modulation in AML. Cell lines of AML (HEL) and normal human lymphocytes (IMC) were cultured in standard culture, Zn depletion, and supplementation (40 μM ZnSO4) conditions and exposed to hydrogen peroxide (H2O2) or ultraviolet (UV) radiation. Chromosomal damage, cell death, and nuclear division indexes (NDI) were assessed through cytokinesis-block micronucleus assay. The phosphorylated histone H2AX (yH2AX) expression was monitored at 0 h, 1 h, and 24 h after exposure. Expression of DDR genes was evaluated by quantitative real time polymerase chain reaction (qPCR). Zn supplementation increased the genotoxicity of H2O2 and UV radiation in AML cells, induced cytotoxic and antiproliferative effects, and led to persistent yH2AX activation. In contrast, in normal lymphocytes, supplementation decreased damage rates, while Zn depletion favored damage accumulation and impaired repair kinetics. Gene expression was not affected by Zn depletion or supplementation. Zn presented a dual role in the modulation of genome damage, preventing damage accumulation in normal cells and increasing genotoxicity and cytotoxicity in AML cells.

Modulation of DNA Damage Response by SAM and HD Domain Containing Deoxynucleoside Triphosphate Triphosphohydrolase (SAMHD1) Determines Prognosis and Treatment Efficacy in Different Solid Tumor Types.

Simple SummaryAmple evidence exists connecting dNTP pool dysregulation to cancer and genomic instability. SAMHD1, the unique dNTP triphosphohydrolase described in humans, has been proposed to play a key role in hematological cancers, although its value in advanced solid tumors has not yet been explored. Moreover, it has been proposed that SAMHD1 might fulfill the requirements of a driver gene in tumor development or might promote a so-called mutator phenotype. Here, we show that low SAMHD1 expression tumors show better prognosis in breast, ovarian, and lung advanced cancer. Moreover, low SAMHD1 expression is a positive predictive factor in lung and ovarian cancer treated with platin derivates and/or antimetabolites. In vitro evaluation of its underlying mechanism revealed that SAMHD1 KO cells presented enhanced susceptibility to DNA damage and subsequent induction of apoptosis of tumor cells. Our results provide strong evidence of the clinical importance of SAMHD1, becoming an interesting target for the development of personalized cancer treatments.SAMHD1 is a deoxynucleotide triphosphate (dNTP) triphosphohydrolase with important roles in the control of cell proliferation and apoptosis, either through the regulation of intracellular dNTPs levels or the modulation of the DNA damage response. However, SAMHD1′s role in cancer evolution is still unknown. We performed the first in-depth study of SAMHD1′s role in advanced solid tumors, by analyzing samples of 128 patients treated with chemotherapy agents based on platinum derivatives and/or antimetabolites, developing novel in vitro knock-out models to explore the mechanisms driving SAMHD1 function in cancer. Low (or no) expression of SAMHD1 was associated with a positive prognosis in breast, ovarian, and non-small cell lung cancer (NSCLC) cancer patients. A predictive value was associated with low-SAMHD1 expression in NSCLC and ovarian patients treated with antimetabolites in combination with platinum derivatives. In vitro, SAMHD1 knock-out cells showed increased γ-H2AX and apoptosis, suggesting that SAMHD1 depletion induces DNA damage leading to cell death. In vitro treatment with platinum-derived drugs significantly enhanced γ-H2AX and apoptotic markers expression in knock-out cells, indicating a synergic effect of SAMHD1 depletion and platinum-based treatment. SAMHD1 expression represents a new strong prognostic and predictive biomarker in solid tumors and, thus, modulation of the SAMHD1 function may constitute a promising target for the improvement of cancer therapy.

HO-1 and Heme: G-Quadruplex Interaction Choreograph DNA Damage Responses and Cancer Growth.

Many anti-cancer therapeutics lead to the release of danger associated pattern molecules (DAMPs) as the result of killing large numbers of both normal and transformed cells as well as lysis of red blood cells (RBC) (hemolysis). Labile heme originating from hemolysis acts as a DAMP while its breakdown products exert varying immunomodulatory effects. Labile heme is scavenged by hemopexin (Hx) and processed by heme oxygenase-1 (HO-1, Hmox1), resulting in its removal and the generation of biliverdin/bilirubin, carbon monoxide (CO) and iron. We recently demonstrated that labile heme accumulates in cancer cell nuclei in the tumor parenchyma of Hx knockout mice and contributes to the malignant phenotype of prostate cancer (PCa) cells and increased metastases. Additionally, this work identified Hx as a tumor suppressor gene. Direct interaction of heme with DNA G-quadruplexes (G4) leads to altered gene expression in cancer cells that regulate transcription, recombination and replication. Here, we provide new data supporting the nuclear role of HO-1 and heme in modulating DNA damage response, G4 stability and cancer growth. Finally, we discuss an alternative role of labile heme as a nuclear danger signal (NDS) that regulates gene expression and nuclear HO-1 regulated DNA damage responses stimulated by its interaction with G4.

SCR7, an inhibitor of NHEJ can sensitize tumor cells to ionization radiation

Nonhomologous end joining (NHEJ), one of the major DNA double-strand break repair pathways, plays a significant role in cancer cell proliferation and resistance to radio and chemotherapeutic agents. Previously, we had described a small molecule inhibitor, SCR7, which inhibited NHEJ in a DNA Ligase IV dependent manner. Here, we report that SCR7 potentiates the effect of γ-radiation (IR) that induces DNA breaks as intermediates to eradicate cancer cells. Dose fractionation studies revealed that coadministration of SCR7 and IR (0.5 Gy) in mice Dalton's lymphoma (DLA) model led to a significant reduction in mice tumor cell proliferation, which was equivalent to that observed for 2 Gy dose when both solid and liquid tumor models were used. Besides, co-treatment with SCR7 and 1 Gy of IR further improved the efficacy. Notably, there was no significant change in blood parameters, kidney and liver functions upon combinatorial treatment of SCR7 and IR. Further, the co-treatment of SCR7 and IR resulted in a significant increase in unrepaired DSBs within cancer cells compared to either of the agent alone. Anatomy, histology, and other studies in tumor models confirmed the cumulative effects of both agents in activating apoptotic pathways to induce cytotoxicity by modulating DNA damage response and repair pathways. Thus, we report that SCR7 has the potential to reduce the side effects of radiotherapy by lowering its effective dose ex vivo and in mice tumor models, with implications in cancer therapy.

Modulation of DNA damage response by targeting ATM kinase using newly synthesized di-phenoxy acetamide (DPA) analogs to induce anti-neoplasia.

Imbalance and instability in the structure of the DNA have become major characteristics of cancer. In response to DNA damage, DNA damage response (DDR) protein, ataxia telangiectasia mutated (ATM), plays a pivotal role in the modulation of regulatory regions responsible for inhibition of apoptosis, thereby neoplastic progression. A new series of DPA (7a-t) were synthesized, characterized. Anti-proliferative studies to identify the lead compound were carried out by LDH and MTT assay. Apoptosis/DNA damage was measured through FACS, Annexin-v staining, TUNEL and Comet assay. Elucidation of molecular mechanism through immunoblot and further validation of the drug effect through in vivo approaches. Initial in vitro anti-proliferative screening of Compounds DPA (7a-t) against multiple cancer cell lines identified Compound DPA (7n) as a potent cytotoxic molecule with IC50 value of 4.3μM. Down the line, in vitro and in vivo evaluation of Compound DPA (7n) inferred that it has apoptotic inducing potentiality. Further, evaluation of molecular mechanism inferred that Compound DPA (7n) effectively modulates ATM phosphorylation only, eventually altering downstream signalling pathways. Compound DPA (7n) emerged as a potent proapoptotic and anti-neoplastic agent by inhibiting ATM kinase activity both in vitro and in vivo. The conferring results ascertain that the drug could be developed as a new ATM kinase inhibitor with anti-cancer capacity.

Deficiency of Histone Methyltransferase SET Domain-Containing 2 in Liver Leads to Abnormal Lipid Metabolism and HCC.

Trimethylation of Lys36 on histone 3 (H3K36me3) catalyzed by histone methyltransferase SET domain-containing 2 (SETD2) is one of the most conserved epigenetic marks from yeast to mammals. SETD2 is frequently mutated in multiple cancers and acts as a tumor suppressor. Here, using a liver-specific Setd2 depletion model, we found that Setd2 deficiency is sufficient to trigger spontaneous HCC. Meanwhile, Setd2 depletion significantly increased tumor and tumor size of a diethylnitrosamine-induced HCC model. The mechanistic study showed that Setd2 suppresses HCC not only through modulating DNA damage response, but also by regulating lipid metabolism in the liver. Setd2 deficiency down-regulated H3K36me3 enrichment and expression of cholesterol efflux genes and caused lipid accumulation. High-fat diet enhanced lipid accumulation and promoted the development of HCC in Setd2-deficient mice. Chromatin immunoprecipitation sequencing analysis further revealed that Setd2 depletion induced c-Jun/activator protein 1 (AP-1) activation in the liver, which was trigged by accumulated lipid. c-Jun acts as an oncogene in HCC and functions through inhibiting p53 in Setd2-deficient cells. We revealed the roles of Setd2 in HCC and the underlying mechanisms in regulating cholesterol homeostasis and c-Jun/AP-1 signaling.

Effect of ATR Inhibition in RT Response of HPV-Negative and HPV-Positive Head and Neck Cancers.

Radiotherapy (RT) has a central role in head and neck squamous cell carcinoma (HNSCC) treatment. Targeted therapies modulating DNA damage response (DDR) and more specific cell cycle checkpoints can improve the radiotherapeutic response. Here, we assessed the influence of ataxia-telangiectasia mutated and Rad3-related (ATR) inhibition with the ATR inhibitor AZD6738 on RT response in both human papillomavirus (HPV)-negative and HPV-positive HNSCC. We found that ATR inhibition enhanced RT response in HPV-negative and HPV-positive cell lines independent of HPV status. The radiosensitizing effect of AZD6738 was correlated with checkpoint kinase 1 (CHK1)-mediated abrogation of G2/M-arrest. This resulted in the inhibition of RT-induced DNA repair and in an increase in the percentage of micronucleated cells. We validated the enhanced RT response in HPV-negative and HPV-positive xenograft models. These data demonstrate the potential use of ATR inhibition in combination with RT as a treatment option for both HPV-negative and HPV-positive HNSCC patients.

Modulation of DNA Damage Response by Samhd1 Determines Prognosis and Treatment Efficacy in Different Solid Tumor Types

Modulation of DNA Damage Response by Samhd1 Determines Prognosis and Treatment Efficacy in Different Solid Tumor Types