Benzo[a]pyrene-dependent activation of transcription factors NF-κB and AP-1 related to tumor promotion in hepatoma cell cultures

Targeting CD166+ lung cancer stem cells: Molecular study using murine dendritic cell vaccine

PURPOSE

Cancer stem cells (CSC) are the most common causes of lung cancer relapse and mouse resistance to chemotherapy. CD166 was identified as CSC marker for lung cancer. Our study aimed to detect the effect of dendritic cell vaccine loaded with tumor cell lysate (TCL-DCV) on percentage of CD166⁺ CSC in lung of mice exposed to Benzo(a)Pyrene (BP).

METHODS

Female albino mice were divided into 5 groups (22 mice per group): normal control (NC), lung cancer control (LCC) (50 mg/kg BP orally, twice weekly for four weeks), dendritic cell (DC), TCL-DCV and cisplatin. Cisplatin (6 mg/kg, intraperitoneal) was given in two doses (18th and 20th week). 1 × 10⁶ cells of each of DC and TCL-DCV was given subcutaneously as cisplatin. At the end of experiment (22 weeks), lung tissue was used for evaluation of cytotoxic T lymphocyte antigen-4 (Ctla-4), transforming growth factor-β (Tgf-β), forkhead box protein P3 (Foxp3), programmed death ligand 1 (Pd-l1) and interleukin 12 (Il-12) gene expression using quantitative RT-PCR. The percentage of CD83⁺, CD8⁺ and CD166⁺ cells in lung tissue were measured using flow cytometry.

RESULTS

The results revealed that TCL-DCV reversed the tumorigenic effect of BP in the lung as evidenced by histopathological examination. Compared to cisplatin, dendritic cell vaccination (TCL-DCV) significantly decreased percentage of CD166⁺ CSC. This anticancer stemness effect was attributed to the immune-stimulatory effect as indicated by increased percentage of CD83⁺ and CD8⁺ cells, upregulation of Il-12, and downregulation of Tgf-β, Ctla-4, Pd-l1 and Foxp3 gene expression compared to LCC group.

CONCLUSIONS

TCL-DCV ameliorated cancer stemness through modulating tumor immune archetypes which make it a potent therapeutic alternative to chemotherapy resistant cases.

Involvement of p38 MAPK pathway in benzo(a)pyrene-induced human hepatoma cell migration and invasion

The objective of this study was to investigate the potential role of p38 mitogen-activated protein kinases (MAPK) in benzo(a)pyrene (BaP)-induced hepatoma cell migration and invasion. Western blot assay was applied to detect the expression of proteins. qRT-PCR assay was used to measure the expression of mRNA. Wound healing assay and Transwell invasion assay were performed to evaluate cell migratory ability and cell invasive ability, respectively. Our data showed that BaP exposure increased the expression of p-p38 protein in human hepatoma HepG2 cells. Exposure to BaP facilitated HepG2 cell migration and invasion, which could be blocked by p38 MAPK inhibitors. In addition, BaP exposure induced upregulation of MMP9 mRNA expression, which was modulated by p-p38. In conclusion, p38 MAPK pathway was involved in BaP-induced hepatoma cell migration and invasion.

Cytochrome P450 Monooxygenase-Mediated Metabolic Utilization of Benzo[a]Pyrene by Aspergillus Species

We are increasingly exposed to environmental pollutants, including the carcinogen benzo[a]pyrene (BaP), which has prompted extensive research into human metabolism of toxicants. However, little is known about metabolic mechanisms employed by fungi that are able to use some toxic pollutants as the substrates for growth, leaving innocuous by-products. This study systemically demonstrates that a common soil-dwelling fungus is able to use benzo[a]pyrene as food, which results in expression and metabolic changes associated with growth and energy generation. Importantly, this study reveals key components of the metabolic utilization of BaP, notably a cytochrome P450 monooxygenase and the fungal NF-κB-type transcriptional regulators. Our study advances fundamental knowledge of fungal BaP metabolism and provides novel insight into designing and implementing enhanced bioremediation strategies.

Soil-dwelling fungal species possess the versatile metabolic capability to degrade complex organic compounds that are toxic to humans, yet the mechanisms they employ remain largely unknown. Benzo[a]pyrene (BaP) is a pervasive carcinogenic contaminant, posing a significant concern for human health. Here, we report that several Aspergillus species are capable of degrading BaP. Exposing Aspergillus nidulans cells to BaP results in transcriptomic and metabolic changes associated with cellular growth and energy generation, implying that the fungus utilizes BaP as a growth substrate. Importantly, we identify and characterize the conserved bapA gene encoding a cytochrome P450 monooxygenase that is necessary for the metabolic utilization of BaP in Aspergillus. We further demonstrate that the fungal NF-κB-type velvet regulators VeA and VelB are required for proper expression of bapA in response to nutrient limitation and BaP degradation in A. nidulans. Our study illuminates fundamental knowledge of fungal BaP metabolism and provides novel insights into enhancing bioremediation potential.

Benzo(a)pyrene promotes Hep-G2 cell migration and invasion by upregulating phosphorylated extracellular signal-regulated kinase expression

Benzo(a)pyrene (BaP), a carcinogenic component of cigarette smoke, has been reported to activate extracellular signal-regulated kinase (ERK) in cancer cells. Furthermore, activated ERK is associated with liver cancer cell invasion and metastasis. Therefore, the aim of the present study was to investigate the potential role of phosphorylated (p)-ERK in BaP-induced Hep-G2 cell migration and invasion. An MTT assay was used to determine the effects of BaP treatment on Hep-G2 cell proliferation. Wound-healing and Transwell invasion assays were employed to assess the migration and invasion abilities of Hep-G2 cells. Western blot analysis was applied to detect the expression of proteins. The results of the present study demonstrated that BaP treatment was able to increase the level of p-ERK protein expression in Hep-G2 cells. BaP treatment promoted Hep-G2 cell migration and invasion. The ERK inhibitor, U0126, was able to block the migration and invasion abilities of Hep-G2 cells induced by BaP. The results of the present study demonstrated that BaP treatment promoted the migration and invasion of Hep-G2 cells by upregulating p-ERK expression.

Analysis of gene expression changes in A549 cells induced by organic compounds from respirable air particles

A number of toxic effects of respirable ambient air particles (genotoxic effects, inflammation, oxidative damage) have been attributed to organic compounds bound onto the particle surface. In this study, we analyzed global gene expression changes caused by the extractable organic matters (EOMs) from respirable airborne particles <2.5μm (PM2.5), collected at 3 localities from heavily polluted areas of the Czech Republic and a control locality with low pollution levels, in human lung epithelial A549 cells. Although the sampled localities differed in both extent and sources of air pollution, EOMs did not induce substantially different gene expression profiles. The number of transcripts deregulated in A549 cells treated with the lowest EOM concentration (10μg/ml) ranged from 65 to 85 in 4 sampling localities compared to the number of transcripts deregulated after 30μg/ml and 60μg/ml of EOMs, which ranged from 90 to 109, and from 149 to 452, respectively. We found numerous commonly deregulated genes and pathways related to activation of the aryl hydrocarbon receptor (AhR) and metabolism of xenobiotics and endogenous compounds. We further identified deregulation of expression of the genes involved in pro-inflammatory processes, oxidative stress response and in cancer and developmental pathways, such as TGF-β and Wnt signaling pathways. No cell cycle arrest, DNA repair or pro-apoptotic responses were identified at the transcriptional level after the treatment of A549 cells with EOMs. In conclusion, numerous processes and pathways deregulated in response to EOMs suggest a significant role of activated AhR. Interestingly, we did not observe substantial gene expression changes related to DNA damage response, possibly due to the antagonistic effect of non-genotoxic EOM components. Moreover, a comparison of EOM effects with other available data on modulation of global gene expression suggests possible overlap among the effects of PM2.5, EOMs and various types of AhR agonists.