Involvement of DNA polymerase β overexpression in the malignant transformation induced by benzo[a]pyrene

Diesel exhaust promoted diethylnitrosamine-induced hepatocarcinogenesis in mice

Exposure to diesel exhaust (DE) has been linked to an increased risk of various cancers, including liver cancer. However, the underlying mechanisms driving this association remain insufficiently understood. In this study, we employed a diethylnitrosamine (DEN)-induced mouse liver tumor model and conducted a 19-week combined exposure (750 μg/m3) using a DE exposure system. Our results demonstrated that long-term DE exposure activates cancer-related genes and enhances the formation of DEN-induced liver tumors. Compared to the DEN group, mice in the DEN + diesel exhaust exposure (DEE) group exhibited lower body weight, higher tumor formation rates and more severe DNA damage. The tumor-promoting effect of DE may be associated with the upregulation of SEMA4D and the activation of the PI3K/AKT signaling pathway. Additionally, liver cells in the DEE group exhibited nuclear atypia, a characteristic feature of cancerous transformation. In vitro studies have revealed that exposure to diesel exhaust particles (DEP) promotes the proliferation of HepG2 cells and HUH7 cells by upregulating SEMA4D and activating the PI3K/AKT signaling pathway. This effect was attenuated by inhibiting either SEMA4D or PI3K. This study was the first to identify that DE exposure promotes the development of DEN-induced liver tumors in mice, with the mechanism potentially involving the SEMA4D/PI3K/AKT pathway. These findings provide novel insights into the hepatotoxic effects of DE and highlight the need for further investigation into its carcinogenic potential.

β-Like DNA polymerases and prospects for their use as targets in chemotherapy of tumors

DNA polymerases β are enzymes that perform repair of damaged DNA. In the cells of malignant tumors, there is a change in the production and properties of these enzymes, which is accompanied by altered viability of tumor cells. Analysis of the publications available in Russian and international databases (Pubmed, Elsevier) on the structure and properties of DNA polymerases β and their role in cell growth and proliferation, published over the past 20 years, has shown overexpression of genes encoding β-like DNA polymerases in many types of malignant tumors cells. This explains the maintenance of their viability and proliferative activity. Targeted inhibition of β-like DNA polymerases is accompanied by antiproliferative and antitumor effects. Stable paramagnetic isotopes of magnesium (25Mg2+) or other divalent metals (43Ca2+ and 67Zn2+) with uncompensated nuclear spin isotopes, as well as short single-stranded polydeoxyribonucleotides, can be used as promising antitumor pharmacophores.

Camptosorus sibiricus rupr aqueous extract prevents lung tumorigenesis via dual effects against ROS and DNA damage

ETHNOPHARMACOLOGICAL RELEVANCE

Camptosorus sibiricus Rupr (CSR) is a widely used herbal medicine with antivasculitis, antitrauma, and antitumor effects. However, the effect of CSR aqueous extract on B[a]P-initiated tumorigenesis and the underlying mechanism remain unclear. Moreover, the compounds in CSR aqueous extract need to be identified and structurally characterized.

AIM OF THE STUDY

We aim to investigate the chemopreventive effect of CSR and the underlying molecular mechanism.

MATERIALS AND METHODS

A B[a]P-stimulated normal cell model (BEAS.2B) and lung adenocarcinoma animal model were established on A/J mice. In B[a]P-treated BEAS.2B cells, the protective effects of CSR aqueous extract on B[a]P-induced DNA damage and ROS production were evaluated through flow cytometry, Western blot, real-time quantitative PCR, single-cell gel electrophoresis, and immunofluorescence. Moreover, a model of B[a]P-initiated lung adenocarcinoma was established on A/J mice to determine the chemopreventive effect of CSR in vivo. The underlying mechanism was analyzed via immunohistochemistry and microscopy. Furthermore, the new compounds in CSR aqueous extract were isolated and structurally characterized using IR, HR-ESI-MS, and 1D and 2D NMR spectroscopy.

RESULTS

CSR effectively suppressed ROS production by re-activating Nrf2-mediated reductases HO-1 and NQO-1. Simultaneously, CSR attenuated the DNA damage of BEAS.2B cells in the presence of B[a]P. Moreover, CSR at 1.5 and 3 g/kg significantly suppressed tumorigenesis with tumor inhibition ratios of 36.65% and 65.80%, respectively. The tumor volume, tumor size, and multiplicity of B[a]P-induced lung adenocarcinoma were effectively decreased by CSR in vivo. After extracting and identifying the compounds in CSR aqueous extract, three new triterpene saponins were isolated and characterized structurally.

CONCLUSIONS

CSR aqueous extract prevents lung tumorigenesis by exerting dual effects against ROS and DNA damage, suggesting that CSR is a novel and effective agent for B[a]P-induced carcinogenesis. Moreover, by isolating and structurally characterizing three new triterpene saponins, our study further standardized the quality of CSR aqueous extract, which could widen CSR clinical applications.

A High Throughput Micro-Chamber Array Device for Single Cell Clonal Cultivation and Tumor Heterogeneity Analysis

Recently, single cell cloning techniques have been gradually developed benefited from their important roles in monoclonal antibody screening, tumor heterogeneity research fields, etc. In this study, we developed a high throughput device containing 1400 lateral chambers to efficiently isolate single cells and carry out long-term single cell clonal cultivation as well as tumor heterogeneity studies. Most of the isolated single cells could proliferate normally nearly as long as three weeks and hundreds of clones could be formed once with one device, which made it possible to study tumor heterogeneity at single cell level. The device was further used to examine tumor heterogeneity such as morphology, growth rate, anti-cancer drug tolerance as well as adenosine triphosphate-binding cassette (ABC) transporter ABCG2 protein expression level. Except for the single cell isolation and tumor heterogeneity studies, the device is expected to be used as an excellent platform for drug screening, tumor biomarker discovering and tumor metastasis assay.

Genotoxic damage of benzo[a]pyrene in cultured sea bream (Sparus aurata L.) hepatocytes: harmful effects of chronic exposure

The large majority of studies on the genotoxic hazard of PAHs polluted water widely applied the ENA assay as versatile tool in large number of wild and farmed aquatic species. Nuclear abnormalities are commonly considered to be a direct consequence of genotoxic lesions in DNA macromolecule, and such evaluation might be helpful in identifying the genotoxic damage induced by the most harmful PAHs such as B[a]P. Regarding at the fish species subjected to aquaculture, most of the toxicological data come from wild fish and mainly focus on freshwater fish, but very little is known for other marine major aquacultured species. The gilthead sea bream (Sparus aurata L.) is the most economically important sparid species cultured along the Mediterranean costs, and it has been proved a very sensitive species to acute B[a]P exposure. However, further investigation is needed on several other types of genotoxic assessments, especially for chronic effects. This work was totally based on an in vitro model for chronic toxicity, using long-term S. aurata hepatocytes in primary culture, continuously exposed to low levels of BaP, over a prolonged period of time, to provide evidences for latent toxicity response. We aimed to investigate the kind of nuclear damage in gilthead sea bream hepatocytes continuously exposed to B[a]P sublethal doses. Cells were exposed to several B[a]P concentrations (10 μg/mL, 1 μg/mL, 1 ng/mL, 1 pg/mL) for two exposure times (24 and 72 h), and then tested both for apoptosis induction and for nuclear abnormalities by immunofluorescence analysis. The presence of severe nuclear damage, revealed cells progressing towards abnormal genotypes, due to a series of aberrant mitosis followed by unequal distribution of chromosomal content. The nuclear atypia (NA) more frequently observed were: a) micronuclei (MN); b) nuclear buds or blebs (NBUDs); c) notched nuclei; d) lobed nuclei; e) nuclei with nucleoplasmic bridge (NPBs); f) nuclei squashed, with a residual nuclear membrane; g) open nuclei, with membrane tape unrolled; and h) apoptotic bodies. Our results showed at medium-low doses a sustained genotoxic response, whose potency increased with the exposure time, becoming apparent as apoptosis induction, both by cell surface and nuclear changes. At the lowest doses, the longer was B[a]P exposure, greater was the involvement on masses of replicating cells, establishing the connection between the escape from apoptosis and the selection of tumoral cell evolution. In view of these results, there is no evidence of a threshold dose below which B[a]P was found not to be genotoxic in sea bream cultured hepatocytes.