Therapeutic Targeting of DNA Replication Stress in Cancer

The role of DNA damage response in human embryonic stem cells exposed to atmospheric oxygen tension: Implications for embryo development and differentiation

Previous retrospective cohort studies have found that, compared with oxygen tension in the uterus and fallopian tubes (2 %-8 %), exposure of pre-implantation embryos to atmospheric oxygen tension (AtmO2, 20 %) during assisted reproductive technology(ART) can affect embryo quality, pregnancy outcomes and offspring health. However, current research on the effects and mechanisms of AtmO2 on the development of embryos and offspring is mainly limited to animal experiments. Human embryonic stem cells (hESCs) play a special and irreplaceable role in the study of early human embryonic development. In this study, we used hESCs as a model to elucidate the possible effects and mechanisms of AtmO2 exposure on human embryonic development. We found that exposure to AtmO2 can reduce cell viability, produce oxidative stress, increase DNA damage, initiate DNA repair, activate autophagy, and increase cell apoptosis. We also noticed that approximately 50 % of hESCs survived, adapted and proliferated through high expression of self-renewal and pluripotency regulatory factors, and affected embryoid body differentiation. These data indicate that hESCs experience oxidative stress, accumulation of DNA damage, and activate DNA damage response under the selective pressure of AtmO2.Some hESCs undergo cell death, whereas other hESCs adapt and proliferate through increased expression of self-renewal genes. The current findings provide in vitro evidence that exposure to AtmO2 during the early preimplantation stage negatively affects hESCs.

The metabolic response of HepG2 cells to extracellular vesicles derived from Raphanus sativus L. var. caudatus Alef microgreens probed by chemometrics-assisted LC-MS/MS analysis

Extracellular vesicles (EVs) derived from Thai rat-tailed radish (Raphanus sativus L. var. caudatus Alef) microgreens were previously reported as novel bioactive bioparticles against cancer. This study aimed to investigate the metabolic disruption associated with the antiproliferative effect against HepG2 liver cancer cells, a representative of metabolizing cells and tissue. In this study, the neutral red uptake assay was performed to screen for the antiproliferative effect and determine the cytotoxic concentrations of EVs against HepG2 cells. An untargeted approach to cellular metabolomics was conducted using liquid chromatography coupled with the high-resolution mass spectrometry system with multivariate and univariate analyses to determine the metabolic changes of HepG2 liver cancer cells after EV treatment. EVs showed an antiproliferative effect in HepG2 cells with a half-maximal inhibitory concentration (IC50) of 685.5 ± 26.4 and 139.7 ± 4.2 μg/ml at 24 and 48 h, respectively. In the metabolomics study, 163 metabolites were annotated, with 61 significantly altered metabolites. Among these significant metabolites, 18 were related to glycerophospholipid metabolism. Phosphatidylcholine-the important lipid building blocks for cell membranes, lipid mediators for cell proliferation, and immunosuppressive signaling-was mainly decreased by EV treatment. The alteration of cellular phospholipids in cancer was discussed. This finding suggested the possible mechanism of anticancer action of EVs by disrupting phospholipid metabolism and survival signaling in cancer cells. Further studies should be made to confirm EVs' potential as single and combination therapy in vivo to reduce cancer resistance. This may close the gap between in vitro study and clinical setting.

Inhibition of DNA Topoisomerase Ι by Flavonoids and Polyacetylenes Isolated from Bidens pilosa L

Human DNA topoisomerase I (Topo I) is an essential enzyme in regulating DNA supercoiling during transcription and replication, and it is an important therapeutic target for anti-tumor agents. Bidens pilosa L. is a medicinal herb that is used as a folk medicine for cancers in China. A new flavonoid (1) and a new polyacetylene (20), along with eighteen flavonoids (2-19) and nine polyacetylenes (21-29), were isolated and identified from the methanol extract of the whole plant of B. pilosa, and some of the compounds (4, 5, 6 and 7) exhibited potent cytotoxicity against a panel of five human cancer cell lines. The DNA relaxation assay revealed that some flavonoids and polyacetylenes exerted inhibitory activities on human DNA Topo I, among them compounds 1, 2, 5, 6, 7, 8, 15, 19, 20, 22, and 24 were the most active ones, with IC50 values of 393.5, 328.98, 145.57, 239.27, 224.38, 189.84, 89.91, 47.5, 301.32, 178.03, and 218.27 μM, respectively. The structure-activity analysis of flavonoids was performed according to the results from the Topo I inhibition assay. The DNA content analysis revealed that 5, 6, and 7 potently arrested cell cycle at the G1/S and G2/M phases in human colon cancer cell DLD-1 depending on the concentration of the inhibitors. The levels of protein expression related to the G1/S and G2/M cell cycle checkpoints were in accordance with the results from the DNA content analysis. These findings suggest that flavonoids are one of the key active ingredients accounting for the anti-tumor effect of B. pilosa.

Morphological and Immunocytochemical Characterization of Paclitaxel-Induced Microcells in Sk-Mel-28 Melanoma Cells

Biomarkers, including proteins, nucleic acids, antibodies, and peptides, are essential for identifying diseases such as cancer and differentiating between healthy and abnormal cells in patients. To date, studies have shown that cancer stem cells have DNA repair mechanisms that deter the effects of medicinal treatment. Experiments with cell cultures and chemotherapy treatments of these cultures have revealed the presence of small cells, with a small amount of cytoplasm that can be intensively stained with azure eosin, called microcells. Microcells develop during sporosis from a damaged tumor macrocell. After anticancer therapy in tumor cells, a defective macrocell may produce one or more microcells. This study aims to characterize microcell morphology in melanoma cell lines. In this investigation, we characterized the population of cancer cell microcells after applying paclitaxel treatment to a Sk-Mel-28 melanoma cell line using immunocytochemical cell marker detection and fluorescent microscopy. Paclitaxel-treated cancer cells show stronger expression of stem-associated ALDH2, SOX2, and Nanog markers than untreated cells. The proliferation of nuclear antigens in cells and the synthesis of RNA in microcells indicate cell self-defense, promoting resistance to applied therapy. These findings improve our understanding of microcell behavior in melanoma, potentially informing future strategies to counteract drug resistance in cancer treatment.

Green-synthesized copper oxide nanoparticles induce apoptosis and up-regulate HOTAIR and HOTTIP in pancreatic cancer cells

Aim: Cu2O nanoparticles were synthesized using an extract from S. latifolium algae (SLCu2O NPs). Their effect on PANC-1 cells and the expression of two drug resistance-related lncRNAs were evaluated in comparison with Arsenic trioxide. Materials & methods: SLCu2O NPs were characterized using XRD, SEM, and TEM microscopies. The effects of SLCu2O NPs on cell cytotoxicity, cell cycle, and apoptosis, and expression of two drug resistance-related lncRNAs were examined using MTT assay, flow cytometry, and real-time PCR, respectively. Results: SLCu2O NPs demonstrated anti-cancer properties against PANC-1 cells comparable to Arsenic trioxide, and the expression of lncRNAs increased upon treatment with them. Conclusion: SLCu2O NPs demonstrate anti-cancer properties against PANC-1 cells; however, using gene silencing strategies along with SLCu2O NPs is suggested.

Replication stress as a driver of cellular senescence and aging

Replication stress refers to slowing or stalling of replication fork progression during DNA synthesis that disrupts faithful copying of the genome. While long considered a nexus for DNA damage, the role of replication stress in aging is under-appreciated. The consequential role of replication stress in promotion of organismal aging phenotypes is evidenced by an extensive list of hereditary accelerated aging disorders marked by molecular defects in factors that promote replication fork progression and operate uniquely in the replication stress response. Additionally, recent studies have revealed cellular pathways and phenotypes elicited by replication stress that align with designated hallmarks of aging. Here we review recent advances demonstrating the role of replication stress as an ultimate driver of cellular senescence and aging. We discuss clinical implications of the intriguing links between cellular senescence and aging including application of senotherapeutic approaches in the context of replication stress.

Non-oncogene dependencies: Novel opportunities for cancer therapy

Targeting oncogene addictions have changed the history of subsets of malignancies and continues to represent an excellent therapeutic opportunity. Nonetheless, alternative strategies are required to treat malignancies driven by undruggable oncogenes or loss of tumor suppressor genes and to overcome drug resistance also occurring in cancers addicted to actionable drivers. The discovery of non-oncogene addiction (NOA) uncovered novel therapeutically exploitable "Achilles' heels". NOA refers to genes/pathways not oncogenic per sé but essential for the tumor cell growth/survival while dispensable for normal cells. The clinical success of several classes of conventional and molecular targeted agents can be ascribed to their impact on both tumor cell-associated intrinsic as well as microenvironment-related extrinsic NOA. The integration of genetic, computational and pharmacological high-throughput approaches led to the identification of an expanded repertoire of synthetic lethality interactions implicating NOA targets. Only a few of them have been translated into the clinics as most NOA vulnerabilities are not easily druggable or appealing targets. Nonetheless, their identification has provided in-depth knowledge of tumor pathobiology and suggested novel therapeutic opportunities. Here, we summarize conceptual framework of intrinsic and extrinsic NOA providing exploitable vulnerabilities. Conventional and emerging methodological approaches used to disclose NOA dependencies are reported together with their limits. We illustrate NOA paradigmatic and peculiar examples and outline the functional/mechanistic aspects, potential druggability and translational interest. Finally, we comment on difficulties in exploiting the NOA-generated knowledge to develop novel therapeutic approaches to be translated into the clinics and to fully harness the potential of clinically available drugs.

Cutaneous Oncology: Strategies for Melanoma Prevention, Diagnosis, and Therapy

Skin cancer comprises one-third of all diagnosed cancer cases and remains a major health concern. Genetic and environmental parameters serve as the two main risk factors associated with the development of skin cancer, with ultraviolet radiation being the most common environmental risk factor. Studies have also found fair complexion, arsenic toxicity, indoor tanning, and family history among the prevailing causes of skin cancer. Prevention and early diagnosis play a crucial role in reducing the frequency and ensuring effective management of skin cancer. Recent studies have focused on exploring minimally invasive or non-invasive diagnostic technologies along with artificial intelligence to facilitate rapid and accurate diagnosis. The treatment of skin cancer ranges from traditional surgical excision to various advanced methods such as phototherapy, radiotherapy, immunotherapy, targeted therapy, and combination therapy. Recent studies have focused on immunotherapy, with the introduction of new checkpoint inhibitors and personalized immunotherapy enhancing treatment efficacy. Advancements in multi-omics, nanotechnology, and artificial intelligence have further deepened the understanding of the mechanisms underlying tumoral growth and their interaction with therapeutic effects, which has paved the way for precision oncology. This review aims to highlight the recent advancements in the understanding and management of skin cancer, and provide an overview of existing and emerging diagnostic, prognostic, and therapeutic modalities, while highlighting areas that require further research to bridge the existing knowledge gaps.

Canonical binding of Chaetomium thermophilum DNA polymerase δ/ζ subunit PolD3 and flap endonuclease Fen1 to PCNA

The sliding clamp PCNA is a key player in eukaryotic genome replication and stability, acting as a platform onto which components of the DNA replication and repair machinery are assembled. Interactions with PCNA are frequently mediated via a short protein sequence motif known as the PCNA-interacting protein (PIP) motif. Here we describe the binding mode of a PIP motif peptide derived from C-terminus of the PolD3 protein from the thermophilic ascomycete fungus C. thermophilum, a subunit of both DNA polymerase δ (Pol δ) and the translesion DNA synthesis polymerase Pol ζ, characterised by isothermal titration calorimetry (ITC) and protein X-ray crystallography. In sharp contrast to the previously determined structure of a Chaetomium thermophilum PolD4 peptide bound to PCNA, binding of the PolD3 peptide is strictly canonical, with the peptide adopting the anticipated 310 helix structure, conserved Gln441 inserting into the so-called Q-pocket on PCNA, and Ile444 and Phe448 forming a two-fork plug that inserts into the hydrophobic surface pocket on PCNA. The binding affinity for the canonical PolD3 PIP-PCNA interaction determined by ITC is broadly similar to that previously determined for the non-canonical PolD4 PIP-PCNA interaction. In addition, we report the structure of a PIP peptide derived from the C. thermophilum Fen1 nuclease bound to PCNA. Like PolD3, Fen1 PIP peptide binding to PCNA is achieved by strictly canonical means. Taken together, these results add to an increasing body of information on how different proteins bind to PCNA, both within and across species.