Inhibition Of DNA Replication Research Articles

REV3 promotes cellular tolerance to 5-fluorodeoxyuridine by activating translesion DNA synthesis and intra-S checkpoint.

The drug floxuridine (5-fluorodeoxyuridine, FUdR) is an active metabolite of 5-Fluorouracil (5-FU). It converts to 5-fluorodeoxyuridine monophosphate (FdUMP) and 5-fluorodeoxyuridine triphosphate (FdUTP), which on incorporation into the genome inhibits DNA replication. Additionally, it inhibits thymidylate synthase, causing dTMP shortage while increasing dUMP availability, which induces uracil incorporation into the genome. However, the mechanisms underlying cellular tolerance to FUdR are yet to be fully elucidated. In this study, we explored the mechanisms underlying cellular resistance to FUdR by screening for FUdR hypersensitive mutants from a collection of DT40 mutants deficient in each genomic maintenance system. We identified REV3, which is involved in translesion DNA synthesis (TLS), to be a critical factor in FUdR tolerance. Replication using a FUdR-damaged template was attenuated in REV3-/- cells, indicating that the TLS function of REV3 is required to maintain replication on the FUdR-damaged template. Notably, FUdR-exposed REV3-/- cells exhibited defective cell cycle arrest in the early S phase, suggesting that REV3 is involved in intra-S checkpoint activation. Furthermore, REV3-/- cells showed defects in Chk1 phosphorylation, which is required for checkpoint activation, but the survival of FUdR-exposed REV3-/- cells was further reduced by the inhibition of Chk1 or ATR. These data indicate that REV3 mediates DNA checkpoint activation at least through Chk1 phosphorylation, but this signal acts in parallel with ATR-Chk1 DNA damage checkpoint pathway. Collectively, we reveal a previously unappreciated role of REV3 in FUdR tolerance.

Genome-wide Mapping of Topoisomerase Binding Sites Suggests Topoisomerase 3α (TOP3A) as a Reader of Transcription-Replication Conflicts (TRC).

Both transcription and replication can take place simultaneously on the same DNA template, potentially leading to transcription-replication conflicts (TRCs) and topological problems. Here we asked which topoisomerase(s) is/are the best candidate(s) for sensing TRC. Genome-wide topoisomerase binding sites were mapped in parallel for all the nuclear topoisomerases (TOP1, TOP2A, TOP2B, TOP3A and TOP3B). To increase the signal to noise ratio (SNR), we used ectopic expression of those topoisomerases in H293 cells followed by a modified CUT&Tag method. Although each topoisomerase showed distinct binding patterns, all topoisomerase binding signals positively correlated with gene transcription. TOP3A binding signals were suppressed by DNA replication inhibition. This was also observed but to a lesser extent for TOP2A and TOP2B. Hence, we propose the involvement of TOP3A in sensing both head-on TRCs (HO-TRCs) and co-directional TRCs (CD-TRCs). In which case, the TOP3A signals appear concentrated within the promoters and first 20 kb regions of the 5' -end of genes, suggesting the prevalence of TRCs and the recruitment of TOP3A in the 5'-regions of transcribed and replicated genes.

Antibacterial mechanism and structure-activity relationships of Bombyx mori cecropin A.

Bombyx mori cecropin A (Bmcecropin A) has antibacterial, antiviral, anti-filamentous fungal and tumour cell inhibition activities and is considered a potential succedaneum for antibiotics. We clarified the antibacterial mechanism and structure-activity relationships and then directed the structure-activity optimization of Bmcecropin A. Firstly, we found Bmcecropin A shows a strong binding force and permeability to cell membranes like a detergent; Bmcecropin A could competitively bind to the cell membrane with the cell membrane-specific dye DiI, then damaged the membrane for the access of DiI into the cytoplasm and leading to the leakage of electrolyte and proteins. Secondly, we found Bmcopropin A could also bind to and degrade DNA; furthermore, DNA library polymerase chain reaction (PCR) results indicated that Bmcecropin A inhibited DNA replication by non-specific binding. In addition, we have identified C-terminus amidation and serine-lysine- glycine (SLG) amino acids of Bmcecropin A played critical roles in the membrane damage and DNA degradation. Based on the above results, we designed a mutant of Bmcecropin A (E9 to H, D17 to K, K33 to A), which showed higher antibacterial activity, thermostability and pH stability than ampicillin but no haemolytic activity. Finally, we speculated that Bmcecropin A damaged the cell membrane through a carpet model and drew the schematic diagram of its antibacterial mechanism, based on the antibacterial mechanism and the three-dimensional configuration. These findings yield insights into the mechanism of antimicrobial peptide-pathogen interaction and beneficial for the development of new antibiotics.

Aberrant RNA polymerase initiation and processivity on the genome of a herpes simplex virus 1 mutant lacking ICP27.

Within the first 15 minutes of infection, herpes simplex virus 1 immediate early proteins repurpose cellular RNA polymerase (Pol II) for viral transcription. An important role of the viral-infected cell protein 27 (ICP27) is to facilitate viral pre-mRNA processing and export viral mRNA to the cytoplasm. Here, we use precision nuclear run-on followed by deep sequencing (PRO-seq) to characterize transcription of a viral ICP27 null mutant. At 1.5 and 3 hours post infection (hpi), we observed increased total levels of Pol II on the mutant viral genome and accumulation of Pol II downstream of poly A sites indicating increased levels of initiation and processivity. By 6 hpi, Pol II accumulation on specific mutant viral genes was higher than that on wild-type virus either at or upstream of poly A signals, depending on the gene. The PRO-seq profile of the ICP27 mutant on late genes at 6 hpi was similar but not identical to that caused by treatment with flavopiridol, a known inhibitor of RNA processivity. This pattern was different from PRO-seq profiles of other α gene mutants and upon inhibition of viral DNA replication with PAA. Together, these results indicate that ICP27 contributes to the repression of aberrant viral transcription at 1.5 and 3 hpi by inhibiting initiation and decreasing RNA processivity. However, ICP27 is needed to enhance processivity on most late genes by 6 hpi in a mechanism distinguishable from its role in viral DNA replication.IMPORTANCEWe developed and validated the use of a processivity index for precision nuclear run-on followed by deep sequencing data. The processivity index calculations confirm infected cell protein 27 (ICP27) induces downstream of transcription termination on certain host genes. The processivity indices and whole gene probe data implicate ICP27 in transient immediate early gene-mediated repression, a process that also requires ICP4, ICP22, and ICP0. The data indicate that ICP27 directly or indirectly regulates RNA polymerase (Pol II) initiation and processivity on specific genes at specific times post infection. These observations support specific and varied roles for ICP27 in regulating Pol II activity on viral genes in addition to its known roles in post transcriptional mRNA processing and export.

Structural basis of human mpox viral DNA replication inhibition by brincidofovir and cidofovir

Mpox virus has wildly spread over 108 non-endemic regions in the world since May 2022. DNA replication of mpox is performed by DNA polymerase machinery F8-A22-E4, which is known as a great drug target. Brincidofovir and cidofovir are reported to have broad-spectrum antiviral activity against poxviruses, including mpox virus in animal models. However, the molecular mechanism is not understood. Here we report cryogenic electron microscopy structures of mpox viral F8-A22-E4 in complex with a DNA duplex, or dCTP and the DNA duplex, or cidofovir diphosphate and the DNA duplex at resolution of 3.22, 2.98 and 2.79 Å, respectively. Our structural work and DNA replication inhibition assays reveal that cidofovir diphosphate is located at the dCTP binding position with a different conformation to compete with dCTP to incorporate into the DNA and inhibit DNA synthesis. Conformation of both F8-A22-E4 and DNA is changed from the pre-dNTP binding state to DNA synthesizing state after dCTP or cidofovir diphosphate is bound, suggesting a coupling mechanism. This work provides the structural basis of DNA synthesis inhibition by brincidofovir and cidofovir, providing a rational strategy for new therapeutical development for mpox virus and other pox viruses.

The concept of folic acid supplementation and its role in prevention of neural tube defect among pregnant women: PRISMA.

Folic acid is the synthetic form of vitamin B9, found in supplements and fortified foods, while folate occurs naturally in foods. Folic acid and its derivatives are extremely important in the synthesis of nucleic acids (DNA and ribose nucleic acid [RNA]) and different proteins. It acts as a coenzyme for the transfer of 1 carbon in the biosynthesis of purine, pyrimidine, and amino acids. Folic acid is critically important in rapidly proliferating tissues, including fetus and trophoblastic tissue to prevent neural tube defect (NTD). The main objective of this review is to identify the role of folic acid to prevent NTD among pregnancy mothers. Electronic databases including Web of Science, Google Scholar, MEDLINE, Scopus, and Cochrane library used to systematically search without limitation of publication date and status. In pregnancy, the first trimester is a significant time for neural tube closure. Decreased blood folic acid levels inhibit DNA replication, repair, RNA synthesis, histone and DNA methylation, methionine production, and homocysteine remethylation reactions that cause NTDs in pregnancy. Therefore, folic acid supplementation is critically important for childbearing mothers before conception and in the first trimester pregnancy. As a result, women are recommended to take 400 microgram FA/day from preconception until the end of the first trimester to prevent NTD-affected pregnancies. This allows the developing neural tissue to acquire critical mass and provides the preferred rostrocaudal orientation so that these divisions contribute to the elongation of the developing neural tube in embryos.

Bombyx moriSuppressor of Hairless is involved in the regulation of the silkworm cell cycle and endoreplication of the silk glands

The Notch signaling pathway is important in cell cycle regulation and cell proliferation. The transcriptional repressor Suppressor of Hairless [Su(H)] is a molecular switch for downstream target genes of the Notch signaling pathway but the regulatory mechanism of the Su(H) gene in the cell cycle is unclear. We determined the function of the Notch signaling pathway and Bombyx mori Su(H) [BmSu(H)] in the regulation of the silkworm cell cycle. Inhibition of Notch signaling promoted the replication of DNA in silkworm gland cells and expression of the BmSu(H) gene was significantly reduced. Overexpression of the BmSu(H) gene inhibited DNA replication and cell proliferation of silkworm cells, whereas knockout of the BmSu(H) gene promoted DNA replication and cell proliferation. Knockout of the BmSu(H) in silkworms improved the efficiency of silk gland cell endoreplication and increased important economic traits. We demonstrated that BmSu(H) protein can directly bind to the promoters of BmCyclinA, BmCyclinE and BmCDK1 genes, inhibiting or promoting their transcription at the cell and individual level. This study identified molecular targets for genetic improvement of the silkworm and also provided insights into the regulatory mechanism of the cell cycle.

Exploring Phytotherapy's Preventive and Therapeutic Impact on Global COVID-19 Management: A Narrative Review

Introduction:: The WHO Emergency Committee advocates preventive strategies for COVID-19 management, emphasising vaccines as highly effective but acknowledging their limitations. Chloroquine and hydroxychloroquine, initially effective against COVID-19, were discontinued due to severe side effects. Further clinical trials are imperative to establish the safety and efficacy of new antiviral agents, some of which may have harmful effects on human development. Objectives:: The shortcomings of various conventional treatments have prompted urgent efforts to discover safe, natural compounds that may be useful in combating COVID-19. This study aims to review research that has investigated the potential of traditional phytotherapies used by different populations for the prevention and symptomatic treatment of COVID-19 infection. Methods:: This paper reviewed scientific studies published through searching on search engines such as PubMed, Scopus, Google Scholar, ScienceDirect and Elsevier from May until October 2023. Results:: The preventive and anti-COVID-19 attributes of Traditional Chinese Medicine, Ayurvedic formulations and African medicinal plants have been substantiated in research. In Nepal, recommendations endorse the utilisation of medicinal plants for herbal teas and homemade sanitizers. Zingiber officinale, Curcuma longa L. and Curcuma xanthorriza Roxb., along with Camellia sinensis are crucial Indonesian medicinal plants with potential for treating COVID-19. Z. officinale was predominantly chosen for relieving coughs and sore throats associated with COVID-19 in Saudi Arabia. Discussion:: The immunomodulatory properties of medicinal plants, which may prove useful in combating COVID-19, have been verified via elevation of the level of peripheral WBCs, IgM, IgG; inhibition of leukotrienes and prostaglandins, maintenance of the integrity of intestinal mucosal barrier and regulation of HMGB1. The antiviral effects of herbs, including the inhibition of viral DNA and RNA replication, down-regulation of oxidative stress, and the impediment of SARS-CoV-2 access to vascular endothelial cells, suggest their potential to facilitate earlier recovery from COVID-19 infection. Conclusion:: Advancing scientific research in phytotherapy promises the possibility of novel approaches for effectively managing future infectious diseases and pandemics.

ZBTB16 inhibits DNA replication and induces cell cycle arrest by targeting WDHD1 transcription in lung adenocarcinoma.

Lung adenocarcinoma is a malignant tumor with high morbidity and mortality. ZBTB16 plays a double role in various tumors; however, the potential mechanism of ZBTB16 in the pathophysiology of lung adenocarcinoma has yet to be elucidated. We herein observed a decreased expression of ZBTB16 mRNA and protein in lung adenocarcinoma and a significantly increased DNA methylation level of ZBTB16 in patients with lung adenocarcinoma. Analysis of public databases and patients' clinical data indicated a close association between ZBTB16 and patient survival. Ectopic expression of ZBTB16 in lung adenocarcinoma cells significantly inhibited cell proliferation, invasion, and migration. It also induced cell cycle arrest in the S phase. Meanwhile, mitotic catastrophe was induced, and DNA damage and apoptosis occurred. In line with these findings, the overexpression of ZBTB16 in xenograft mice resulted in the inhibition of tumor growth. Comprehensive analysis showed that WDHD1 was a potential target for ZBTB16. The overexpression of both isoforms of WDHD1 significantly reversed the ZBTB16-mediated inhibition of lung adenocarcinoma proliferation and cell cycle. These studies suggest that ZBTB16 impedes the progression of lung adenocarcinoma by interfering with WDHD1 transcription, making it a potential novel therapeutic target in the management of lung adenocarcinoma.

Synthesis, Characterization and DNA Binding Study of Silver N-Heterocyclic Carbene Complex [Bis (1,3-Dipentyl-1,3-Dihydro-2-Imidazole-2-Ylidene) Silver (I) hexafluorophosphate (V)] by Surface-Enhanced Raman Spectroscopy (SERS)

The silver organometallic compounds favorably target DNA in cancerous cells and stop their growth by inhibiting DNA replication. Specific properties of these compounds help in their action as drugs and different changes occur in the structure of DNA. In-depth study of the binding mechanism of drugs is of potential use for novel drug synthesis. Surface-enhanced Raman spectroscopy (SERS) coupled with multivariate data analysis was employed to probe the interaction of silver N-heterocyclic carbene complex (drug) with DNA. In this study, silver N-heterocyclic carbene complex was synthesized and various concentrations were exposed to known concentrations of DNA. Silver nanoparticles were used for enhancement of Raman signals, which enabled sensitive detection and characterization of molecular changes occurring during binding process. Principal component analysis (PCA) and partial least squares discriminant analysis (PLS-DA) were applied to extract meaningful information from the spectral data. Changes in intensity and position of significant SERS signals were noted, which gave an indication of the bonding of the drug with DNA. The results reveal the strong intercalative binding of drug with nitrogenous bases of DNA. PCA and PLS-DA provide evidence for successful DNA-drug interaction.

Abstract LB043: VBC101-F11: An innovative EGFR/cMet bispecific antibody drug conjugate (ADC) targeting key oncogenic drivers in solid tumors

Abstract EGFR and cMet are two classic growth factor receptors frequently co-expressed in solid tumors at significantly high levels, while only limited to moderate expression in normal tissues. Beyond their co-expression patten, the aberrant or over expression in their pathway are implicated in oncogenesis. Notably, MET pathway activation either through increased cMet expression or its ligand, is often associated with resistance to EGFR tyrosine kinase inhibitors (TKI). Therefore, the interplay between EGFR and cMet, coupled with their differential expression in tumors versus normal tissue substantiates the rationale for a bispecific approach that targets both receptors to enhance tumor specificity. VBC101-F11 is a bispecific anti-EGFR/cMet ADC engineered to deliver clinically validated cytotoxic agents to tumor cells with a drug-to antibody ratio (DAR) of 4. This innovative design distinguishes VBC101-F11 from other EGFR/cMet-targeting agents on the market or in clinical trials (ABBV399 or AZD9592), optimizing both efficacy and safety. 1. VBC101-F11 features a low-affinity EGFR arm coupled with a high-affinity cMet arm. Incorporating the low-affinity EGFR arm enhances binding avidity and internalization, resulting in a superior cytotoxicity with a 5-fold improvement in IC50 compared to ABBV-399 (targeting cMet only). This nuanced EGFR arm design ensures a reduction in EGFR-related off-target toxicity in normal tissues. 2. The biparatopic design in cMet arm further underscores our strategic rationale by demonstrating a synergistic effect in terms of binding, internalization, and functional blocking with a 10-fold improvement in EC50 compared to the monospecific parental antibodies that target a single epitope. This ensures VBC101-F11’s maximized efficacy in tumor cells. 3. VBC101-F11’s innovative nanobody-based format sets our molecule apart. Living imaging data in mouse model reveals that VBC101-F11 (90kD) achieves superior tumor penetration and accumulation from 1 hour to over 90 hours surpassing the mAb ABBV399 and bispecific antibody AZD9592, both at 150kD. 4. VBC101-F11 has demonstrated outstanding molecular developability in stress tests, particularly in human and non-human primate (NHP) plasma, where both the antibody component and the entire ADC molecule exhibit remarkable stability, positioning VBC101-F11 as a viable candidate for future Chemistry, Manufacturing, and Controls (CMC) development. 5. In in vivo CDX models using various lung cancer cell lines, VBC101-F11 equipped with MMAE warhead displayed a marked superiority in tumor growth inhibition (TGI of 60% vs. 17%) at a single dose of 3mg/kg compared to MMAE conjugating ADC ABBV-399. Further payload exploration, such as DNA replication inhibitor, has also yielded promising results, with VBC101-F11-new payload showing comparable efficacy to the same class ADC AZD9592 in models with low EGFR and high cMet expression (100% TGI) and in those with moderate EGFR/cMet expression (~ 60% TGI). In summary, VBC101-F11, with unique design and distinguished attributes, has demonstrated its remarkable potential in the landscape of anti-EGFR/cMet therapies. The encouraging efficacy observed in preclinical models supports the molecule’s advancement into clinical development, positioning it as a best-in-class bispecific ADC for treating tumors in patients. Citation Format: Wei (Vivian) Wang, Jing Li, Lin Ma, Man Xu, Qun Yin. VBC101-F11: An innovative EGFR/cMet bispecific antibody drug conjugate (ADC) targeting key oncogenic drivers in solid tumors [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 LB043.

A platform for predicting mechanism of action based on bacterial transcriptional responses identifies an unusual DNA gyrase inhibitor

In the search for much-needed new antibacterial chemical matter, a myriad of compounds have been reported in academic and pharmaceutical screening endeavors. Only a small fraction of these, however, are characterized with respect to mechanism of action (MOA). Here, we describe a pipeline that categorizes transcriptional responses to antibiotics and provides hypotheses for MOA. 3D-printed imaging hardware PFIboxes) profiles responses of Escherichia coli promoter-GFP fusions to more than 100 antibiotics. Notably, metergoline, a semi-synthetic ergot alkaloid, mimics a DNA replication inhibitor. Invitro supercoiling assays confirm this prediction, and a potent analog thereof (MLEB-1934) inhibits growth at 0.25μg/mL and is highly active against quinolone-resistant strains of methicillin-resistant Staphylococcus aureus. Spontaneous suppressor mutants map to a seldom explored allosteric binding pocket, suggesting a mechanism distinct from DNA gyrase inhibitors used in the clinic. In all, the work highlights the potential of this platform to rapidly assess MOA of new antibacterial compounds.

TisB protein is the single molecular determinant underlying multiple downstream effects of ofloxacin in Escherichia coli.

Bactericidal antibiotics can cause metabolic perturbations that contribute to antibiotic-induced lethality. The molecular mechanism underlying these downstream effects remains unknown. Here, we show that ofloxacin, a fluoroquinolone that poisons DNA gyrase, induces a cascade of metabolic changes that are dependent on an active SOS response. We identified the SOS-regulated TisB protein as the unique molecular determinant responsible for cytoplasmic condensation, proton motive force dissipation, loss of pH homeostasis, and H2O2 accumulation in Escherichia coli cells treated with high doses of ofloxacin. However, TisB is not required for high doses of ofloxacin to interfere with the function of DNA gyrase or the resulting rapid inhibition of DNA replication and lethal DNA damage. Overall, the study sheds light on the molecular mechanisms by which ofloxacin affects bacterial cells and highlights the role of the TisB protein in mediating these effects.

Cynaroside Induces G1 Cell Cycle Arrest by Downregulating Cell Division Cycle 25A in Colorectal Cancer.

Natural chemicals derived from herbal plants have recently been recognized as potentially useful treatment alternatives owing to their ability to target a wide range of important biological molecules. Cynaroside is one of these natural compounds with promising anticancer activity for numerous tumor types. Nevertheless, the anticancer effects and molecular mechanisms of action of cynaroside on colorectal cancer (CRC) remain unclear. In this study, cynaroside was found to markedly inhibit CRC cell proliferation and colony formation in vitro. Cynaroside also inhibited cell proliferation in vivo and decreased the expression of KI67, a cell nuclear antigen. RNA sequencing revealed 144 differentially expressed genes (DEGs) in HCT116 cells and 493 DEGs in RKO cells that were enriched in the cell cycle signaling pathway. Cell division cycle 25A (CDC25A), a DEG widely enriched in the cell cycle signaling pathway, is considered a key target of cynaroside in CRC cells. Cynaroside also inhibited DNA replication and arrested cells in the G1/S phase in vitro. The expression levels of CDC25A and related G1-phase proteins were significantly elevated after CDC25A overexpression in CRC cells, which partially reversed the inhibitory effect of cynaroside on CRC cell proliferation and G1/S-phase arrest. In summary, cynaroside may be used to treat CRC as it inhibits CDC25A expression.

Ultrafast spectroscopy study of DNA photophysics after proflavine intercalation.

Proflavine (PF), an acridine DNA intercalating agent, has been widespread applied as an anti-microbial and topical antiseptic agent due to its ability to suppress DNA replication. On the other hand, various studies show that PF intercalation to DNA can increase photogenotoxicity and has potential chances to induce carcinomas of skin appendages. However, the effects of PF intercalation on the photophysical and photochemical properties of DNA have not been sufficiently explored. In this study, the excited state dynamics of the PF intercalated d(GC)9 • d(GC)9 and d(AT)9 • d(AT)9 DNA duplex are investigated in an aqueous buffer solution. Under 267nm excitation, we observed ultrafast charge transfer (CT) between PF and d(GC)9 • d(GC)9 duplex, generating a CT state with an order of magnitude longer lifetime compared to that of the intrinsic excited state reported for the d(GC)9 • d(GC)9 duplex. In contrast, no excited state interaction was detected between PF and d(AT)9 • d(AT)9. Nevertheless, a localized triplet state with a lifetime over 5 µs was identified in the PF-d(AT)9 • d(AT)9 duplex.

Abstract 4641: Preclinical evaluation of the novel curcumin Analogue AKT-100 demonstrates therapeutic effectiveness in p53-mutated cancer cells

Abstract Among the myriad of molecular alterations associated with cancer, loss of the normal tumor suppressive functions of p53, the “guardian of the genome,” is the most consistent. Thus, the possibility of targeting oncogenic, mutant p53 proteins has long been a therapeutic goal. However, that aspiration has not been fully realized, leaving patients vulnerable to aggressive disease that is resistant to chemotherapy and to targeted agents such as PARP inhibitors and immunotherapy owing to the loss of wild type p53 functionality and the gain of new oncogenic functions when mutant p53 is expressed. An effective therapeutic strategy is urgently needed for p53 mutant cancers, and our team is developing novel analogues of curcumin with the potential to convert mutant p53 to a wild type conformation and restore its tumor suppressive functions. In this study, we investigated the effects of AKT-100, which was developed from the parent molecule and curcumin analogue HO-3867. Effects were compared to another drug believed to reactivate p53 functionality, APR-246, using CyQUANT IC50 cell proliferation assays and bulk and single cell RNA sequencing. Structural analyses are underway investigating the specific sites of interaction of AKT-100 with various mutant forms of p53. Our findings indicate that, first, AKT-100 exhibits impressive cell killing in multiple ovarian and serous endometrial cancer cells at concentrations ranging from 100-300 nM and is synergistic with the PARP inhibitor olaparib. Second, RNA sequencing demonstrates the reactivation of wild type p53 genes associated with normal cell cycle regulation (induction of CDKN1A encoding p21 and GADD45A), apoptosis (induction of PMAIP1 encoding Noxa and DR5 encoding Death Receptor 5), and the inhibition of DNA replication and multiple alternative mechanisms of DNA repair employed by malignant cells. Third, RNA sequencing indicates that AKT-100 acts through both p53-dependent and independent pathways to inhibit cancer cell proliferation. Gene expression is impacted in ways that portend a therapeutic effect as well as highlight potential resistance pathways (e.g. significant induction of PLK5 encoding polo like kinase 5) that can be further targeted to create synthetic lethal drug combinations with AKT-100 chosen specifically to target the various mutant forms of p53. Taken together, these results identify novel curcumin analogues in early development with the potential to improve therapy for p53 mutant cancers. Through this strategy it is also possible to identify and block resistance pathways that are activated by different forms of mutant p53 in response to AKT-100 and to create synthetic lethal precision drug combinations. Citation Format: Kimberly K. Leslie, Jamie L. Padilla, Geneva L. Williams, Hua-Ying Fan, Cristian G. Bologa, Eric R. Prossnitz, Jun-Yong Choe, Lane E. Smith, Alexander Goss, Robert J. Lake, Avinash D. Sahu. Preclinical evaluation of the novel curcumin Analogue AKT-100 demonstrates therapeutic effectiveness in p53-mutated cancer cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 4641.

Abstract 504: Anticancer effects of kaempferol through cell cycle arrest and the inhibition of proliferation in genetically distinct triple-negative breast cancer cells

Abstract Triple-negative breast cancer (TNBC) is one of the most known aggressive subtypes of breast cancer, affecting 1 in 3 newly diagnosed cancers in women. TNBC affects African-American women disproportionally in comparison to Caucasian women. Due to the lack of estrogen receptors (ER), progesterone receptors (PR), and human epidermal growth factor receptors (HER-2), it poses direct challenges to the efficacy of standard hormonal therapies. The current TNBC treatments present higher toxicity and multiple side effects. An alternative would be using natural compounds that have emerged as potential anticancer agents. Kaempferol is a major flavonoid aglycone found in many fruits, vegetables, and herbs, including grapes, tomatoes, broccoli, tea, and ginkgo biloba leaves. In this study, we investigated the differential effect of kaempferol on cell toxicity, cell growth, and underlying mechanisms in inducing cell cycle arrest in genetically different TNBC cells from Caucasian (MDA-MB-231) and African American (MDA-MB- 468) women. Kaempferol significantly inhibited cell growth in both the cell lines with a more profound effect against MDA-MB-231 (IC50: 43.86 µM) compared to MDA-MB-468 cells (IC50: 53.47 µM). Also, kaempferol treatment induced cell cycle arrest at S-phase in both cancer cell subtypes. The MDA-MB-231 cells showed a kaempferol effect at lower concentrations (6.25µM and 12.5µM), while MDA-MB-468 cells showed the same effect at higher concentrations (25µM and 50µM). Kaempferol also modulated CDK gene expression associated with cell cycle progression in breast cancer cells. The inhibition at S-phase is important in cancer treatment because it targets the highly proliferative nature of cancer cells characterized by uncontrolled cell division. This study indicates that, by inducing cell cycle arrest at the S-phase, kaempferol may interfere with cancer cell growth and proliferation by inhibiting DNA replication, offering potential therapeutic benefits. This approach could reduce side effects and increase treatment efficacy, providing hope for more effective interventions in the fight against TNBC. Citation Format: Sukhmandeep Kaur, Patricia Mendonca, Karam F. A. Soliman. Anticancer effects of kaempferol through cell cycle arrest and the inhibition of proliferation in genetically distinct triple-negative breast cancer cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 504.

BmNPV Bm60 is a key target gene used by a resistant strain of Bombyx mori to inhibit BmNPV proliferation

Bombyx mori nucleopolyhedrovirus (BmNPV) is a pathogen that causes significant losses to the silkworm industry. Numerous antiviral genes and proteins have been identified by studying silkworm resistance to BmNPV. However, the molecular mechanism of silkworm resistance to BmNPV is unclear. We analyzed the differences between the susceptible strain 871 and a near-isogenic resistant strain 871C. The survival of strain 871C was significantly greater than that of 871 after oral and subcutaneous exposure to BmNPV. Strain 871C exhibited a nearly 10,000-fold higher LD50 for BmNPV compared to 871. BmNPV proliferation was significantly inhibited in all tested tissues of strain 871C using HE strain and fluorescence analysis. Strain 871C exhibited cellular resistance to BmNPV rather than peritrophic membrane or serum resistance. Strain 871C suppressed the expression of the viral early gene Bm60. This led to the inhibition of BmNPV DNA replication and late structural gene transcription based on the cascade regulation of baculovirus gene expression. Bm60 could also interact with the viral DNA binding protein and alkaline nuclease, as well as host proteins Methylcrotonoyl-CoA carboxylase subunit alpha, mucin-2-like protein, and 30 K-8. Overexpression of 30 K-8 significantly inhibited BmNPV proliferation. These results increase understanding of the molecular mechanism behind silkworm resistance to BmNPV and suggest targets for the breeding of resistant silkworm strains and the controlling pest of Lepidoptera.

Oxidative replication stress induced by long-term exposure to hydroxyurea in root meristem cells of Vicia faba.

Low concentrations of hydroxyurea, an inhibitor of DNA replication, induced oxidative and replicative stress in root apical meristem (RAM) cells of Vicia faba. Plant cells are constantly exposed to low-level endogenous stress factors that can affect DNA replication and lead to DNA damage. Long-term treatments of Vicia faba root apical meristems (RAMs) with HU leads to the appearance of atypical cells with intranuclear asynchrony. This rare form of abnormality was manifested by a gradual condensation of chromatin, from interphase to mitosis (so-called IM cells). Moreover, HU-treated root cells revealed abnormal chromosome structure, persisting DNA replication, and elevated levels of intracellular hydrogen peroxide (H2O2) and superoxide anion (O2∙-). Immunocytochemical studies have shown an increased number of fluorescent foci of H3 histones acetylated at lysine 56 (H3K56Ac; canonically connected with the DNA replication process). We show that continuous 3-day exposure to low concentrations (0.75mM) of hydroxyurea (HU; an inhibitor of DNA replication) induces cellular response to reactive oxygen species and to DNA replication stress conditions.

Lily Polysaccharide Nano‐Selenium Promotes A549 Cells Apoptosis through Cell Cycle Inhibition

AbstractThis study uses Lilium davidii var. unicolor (Lanzhou lily) polysaccharides extracted from bulbs to prepare nano‐selenium (nano‐Se) polysaccharide (LPS). Here, the study explores the molecular structure characterization, inhibition effects, and mechanisms of action of prepared LPS on A549 lung cancer cells. The LPS structure is characterized using Fourier‐transform infrared spectroscopy (FTIR), UV spectroscopy (UV–vis), transmission electron microscopy (TEM), dynamic light scattering (DLS), X‐ray photoelectron spectroscopy (XPS), etc. Results show that selenized polysaccharides bonded through electrostatic adsorption, with an average LPS particle size of 243.75 nm and zeta potential of −38.3 mV, which can be stably preserved at 4 °C for more than 3 months. The in vitro antitumor activity experiment shows that the prepared LPS inhibited A549 cell proliferation while affecting cell migration. Cell cycle analysis shows that apoptosis is promoted by blocking the G1 phase, while during the late apoptosis stage cells accounted for 60%. RNA‐Seq data analysis shows that the main mechanisms of action on A549 cells are to inhibit DNA replication initiation genes, block the cell cycle, and regulate the expression of apoptosis‐related genes and proteins in promoting cell apoptosis.