Benzo[a]pyrene-induced cell cycle progression occurs via ERK-induced Chk1 pathway activation in human lung cancer cells

LncRNA SPRY4-IT1 regulates 16HBE cell malignant transformation induced by particulate matter through DUSP6-ERK1/2-Chk1 signaling pathway

Particulate matter (PM), one of the most serious air contaminants, could easily pass through the airway and deposit at the deep alveoli. Thus, it might trigger respiratory diseases like inflammation, asthma and lung cancer on human. Long non-coding RNAs (lncRNAs) are considered as important regulator in promotion and progression of diverse cancers. However, the molecular mechanism of lncRNAs mediating PM-induced lung carcinogenesis remains unclear. In this study, we established a 16HBE malignant transformed cell induced by PM (Cells were treated with 20 μg/ml PM, which named PM-T cells) and explored the roles and mechanisms of lncRNAs in the malignant transformation induced by PM. Compared with 16HBE cells, various biological functions were changed in PM-T cells, such as cell proliferation, migration, cell cycle and apoptosis. LncRNA SPRY4-IT1 was significant down-regulated expression and associated with these biological effects. Our results showed that lncRNA SPRY4-IT1 overexpression reversed these functional changes mentioned above. The further studies indicated that lncRNA SPRY4-IT1 involved in PM-induced cell transformation by modulating Chk1 expression via negative regulation of DUSP6-ERK1/2. In conclusion, our studies suggested that lncRNA SPRY4-IT1 played the role as a tumor suppressor gene and might mediate 16HBE cells malignant transformation induced by PM through regulating DUSP6-ERK1/2-Chk1 signaling pathway.

Regulation of Xenobiotic-Metabolizing Enzymes by 5-Demethylnobiletin and Nobiletin to Mitigate Benzo[a]pyrene-Induced DNA Damage In Vitro and In Vivo

Benzo[a]pyrene (B[a]P) is a genotoxic polycyclic aromatic hydrocarbon that is metabolized by cytochrome P450 family 1 enzymes (CYP 1s) and can bind to DNA to form DNA adducts, leading to DNA damage and increased colorectal cancer risk. Previous studies have shown polymethoxyflavones to have a high potential for anticancer effects by regulating CYP 1s, especially nobiletin (NBT) and 5-demethylnobiletin (5-DMNB). However, the effects of NBT and 5-DMNB on B[a]P metabolism remain unclear. Therefore, this study aimed to clarify the effects of NBT and 5-DMNB on B[a]P-induced DNA damage in vitro and in vivo. In NCM460 cells, 5-DMNB and NBT appeared to reduce the metabolic conversion of B[a]P by regulating the aryl hydrocarbon receptor (AhR)/CYP 1s signaling pathway. This process protected NCM460 cells from B[a]P's cytotoxic effects by decreasing DNA damage and suppressing B[a]P diol-epoxide-DNA adduct formation. In BALB/c mice, 5-DMNB and NBT also protected against B[a]P-induced DNA damage. Altogether, these findings indicate that 5-DMNB and NBT attenuate B[a]P-induced DNA damage by modulating biotransformation, highlighting their chemopreventive potential against B[a]P-induced carcinogenesis. Therefore, 5-DMNB and NBT are promising agents for colorectal cancer chemoprevention in the future.

Loss of TIPE3 reduced the proliferation, survival and migration of lung cancer cells through inactivation of Akt/mTOR, NF-κB, STAT-3 signaling cascade

Lung cancer is the foremost cause of cancer related mortality among men and one of the most fatal cancers among women. Notably, the 5-year survival rate of lung cancer is very less; 5% in developing countries. This low survival rate can be attributed to factors like late stage diagnosis, rapid postoperative recurrences in the patients undergoing treatment and development of chemoresistance against different agents used for treating lung cancer. Therefore, in this study we evaluated the potential of a recently identified protein namely TIPE3 which is known as a transfer protein of lipid second messengers as a lung cancer biomarker. TIPE3 was found to be significantly upregulated in lung cancer tissues indicating its role in the positive regulation of lung cancer. Supporting this finding, knockout of TIPE3 was also found to reduce the proliferation, survival and migration of lung cancer cells and arrested the G2 phase of cell cycle through inactivation of Akt/mTOR, NF-κB, STAT-3 signaling. It is well evinced that tobacco is the major risk factor of lung cancer which affects both males and females. Therefore, this study also evaluated the involvement of TIPE3 in tobacco mediated lung carcinogenesis. Notably, this study shows for the first time that TIPE3 positively regulates tobacco induced proliferation, survival and migration of lung cancer through modulation of Akt/mTOR signaling. Thus, TIPE3 plays critical role in the pathogenesis of lung cancer and hence it can be specifically targeted to develop novel therapeutic strategies.

A look beyond the priority: A systematic review of the genotoxic, mutagenic, and carcinogenic endpoints of non-priority PAHs

Knowledge of the toxic potential of polycyclic aromatic hydrocarbons (PAHs) has increased over time. Much of this knowledge is about the 16 United States - Environmental Protection Agency (US - EPA) priority PAHs; however, there are other US - EPA non-priority PAHs in the environment, whose toxic potential is underestimated. We conducted a systematic review of in vitro, in vivo, and in silico studies to assess the genotoxicity, mutagenicity, and carcinogenicity of 13 US - EPA non-priority parental PAHs present in the environment. Electronic databases, such as Science Direct, PubMed, Scopus, Google Scholar, and Web of Science, were used to search for research with selected terms without time restrictions. After analysis, following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) protocol, 249 articles, published between 1946 and 2020, were selected and the quality assessment of these studies was performed. The results showed that 5-methylchrysene (5-MC), 7,12-dimethylbenz[a]anthracene (7,12-DMBA), cyclopenta[cd]pyrene (CPP), and dibenzo[al]pyrene (Db[al]P) were the most studied PAHs. Moreover, 5-MC, 7,12-DMBA, benz[j]aceanthrylene (B[j]A), CPP, anthanthrene (ANT), dibenzo[ae]pyrene (Db[ae]P), and Db[al]P have been reported to cause mutagenic effects and have been being associated with a risk of carcinogenicity. Retene (RET) and benzo[c]fluorene (B[c]F), the least studied compounds, showed evidence of a strong influence on the mutagenicity and carcinogenicity endpoints. Overall, this systematic review provided evidence of the genotoxic, mutagenic, and carcinogenic endpoints of US - EPA non-priority PAHs. However, further studies are needed to improve the future protocols of environmental analysis and risk assessment in severely exposed populations.

Human tumor necrosis factor alpha-induced protein eight-like 1 exhibited potent anti-tumor effect through modulation of proliferation, survival, migration and invasion of lung cancer cells

Lung cancer represents one of the most prevalent neoplasms across the globe. Tobacco smoking, exposure to different occupational and environmental carcinogens, and various dietary factors are strongly implicated in the development of lung cancer. The 5-year survival rate of lung cancer is extremely poor which can be attributed to its propensity for early spread, lack of appropriate biomarkers and proper therapeutic strategies for this aggressive neoplasm. Emerging evidence suggests tumor necrosis factor-α-induced protein eight like 1 (TIPE1 or TNFAIP8L1), which functions as a cell death regulator, to hold high prospect as an important biomarker. Interestingly, this protein was found to be significantly downregulated in human lung cancer tissues compared to normal lung tissues. In addition, this protein exerted marked downregulation in different stages and grades of lung tumor. Further knockout of TIPE1 led to the enhancement in proliferation, survival, migration and invasion of NCIH460 human lung cancer cells through modulation of Akt/mTOR/STAT-3 signaling cascade. In addition, TIPE1 was found to be involved in nicotine, 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone, N-nitrosonornicotine and benzo[a]pyrene-mediated lung cancer through enhanced proliferation, survival and migration of lung cancer cells. Altogether, this newly identified protein plays a critical role in lung cancer pathogenesis and possess enormous prospect to serve as an important tool in the effective management of this aggressive neoplasm.

Modulatory Effects of Silymarin on Benzo[a]pyrene-Induced Hepatotoxicity

Benzo[a]pyrene (B[a]P), a polycyclic aromatic hydrocarbon, is a group 1 carcinogen that introduces mutagenic DNA adducts into the genome. In this study, we investigated the molecular mechanisms underlying the involvement of silymarin in the reduction of DNA adduct formation by B[a]P-7,8-dihydrodiol-9,10-epoxide (BPDE), induced by B[a]P. B[a]P exhibited toxicity in HepG2 cells, whereas co-treatment of the cells with B[a]P and silymarin reduced the formation of BPDE-DNA adducts, thereby increasing cell viability. Determination of the level of major B[a]P metabolites in the treated cells showed that BPDE levels were reduced by silymarin. Nuclear factor erythroid 2-related factor 2 (Nrf2) and pregnane X receptor (PXR) were found to be involved in the activation of detoxifying genes against B[a]P-mediated toxicity. Silymarin did not increase the expression of these major transcription factors, but greatly facilitated their nuclear translocation. In this manner, treatment of HepG2 cells with silymarin modulated detoxification enzymes through NRF2 and PXR to eliminate B[a]P metabolites. Knockdown of Nrf2 abolished the preventive effect of silymarin on BPDE-DNA adduct formation, indicating that activation of the Nrf2 pathway plays a key role in preventing B[a]P-induced genotoxicity. Our results suggest that silymarin has anti-genotoxic effects, as it prevents BPDE-DNA adduct formation by modulating the Nrf2 and PXR signaling pathways.

Chidamide-induced ROS accumulation and miR-129-3p-dependent cell cycle arrest in non-small lung cancer cells

BACKGROUND

Epigenetic therapy is a promising popular treatment modality for various cancers. Histone modification and miRNA should not be underestimated in lung cancer. This study aimed to investigate whether chidamide, a histone deacetylase inhibitor (HDACi), which inhibits telomerase activity and induces cell cycle arrest, influences ROS and miRNA production in non-small cell lung cancer (NSCLC) cells.

METHODS

H1355 and A549 were treated with chidamide. The analysis of DNA content was measured by FACSCalibur equipped with a 488 nm laser. H1355 cells were transfected with miR-129-3p mimic by Lipofectamine2000. Telomerase activity was performed on the telomeric repeat amplification protocol (TRAP) assay. Detection of thymidylate synthase (TS), p21, p53, pRB, and β-actin, were performed by western blot analysis.

RESULTS

Our data showed that expression of TS, p21, and pRB were altered in the presence of chidamide by PCR and western blot. Using BrdU-incorporation analysis, we found that chidamide induced G1 arrest through the regulation of the TS gene by miR-129-3p. Chidamide was shown to suppress telomerase activity in the TRAP assay and reduced the expression of human telomerase reverse transcriptase (hTERT) by PCR and q-PCR in H1355 and A549 cells. Chidamide increased the generation of reactive oxygen species (ROS) by flow cytometry. N-acetyl cysteine (NAC), a ROS scavenger, attenuated chidamide-induced telomerase activity inhibition.

CONCLUSION

Chidamide repressed telomerase activity through ROS accumulation and cell cycle arrest by miR-129-3p upregulation in both H1355 and A549 cells. This is the first study to demonstrate that chidamide induces miR-129-3p upregulation and ROS accumulation, leading to cell cycle arrest.

Filling the gap between chemical carcinogenesis and the hallmarks of cancer: A temporal perspective

BACKGROUND

Cancer is believed to arise through the perturbation of pathways and the order of pathway perturbation events can enhance understanding and evaluation of carcinogenicity. This order has not been examined so far, and this study aimed to fill this gap by attempting to gather evidence on the potential temporal sequence of events in carcinogenesis.

DESIGN

The methodology followed was to discuss first the temporal sequence of hallmarks of cancer from the point of view of pathological specimens of cancer (essentially branched mutations) and then to consider the hallmarks of cancer that one well-known carcinogen, benzo(a)pyrene, can modify.

RESULTS

Even though the sequential order of driving genetic alterations can vary between and within tumours, the main cancer pathways affected are almost ubiquitous and follow a generally common sequence: resisting cell death, insensitivity to antigrowth signals, sustained proliferation, deregulated energetics, replicative immortality and activation of invasion and metastasis. The first 3 hallmarks can be regarded as almost simultaneous while angiogenesis and avoiding immune destruction are perhaps the only hallmarks with a varying position in the above sequence.

CONCLUSIONS

Our review of hallmarks of cancer and their temporal sequence, based on mutational spectra in biopsies from different cancer sites, allowed us to propose a hypothetical temporal sequence of the hallmarks. This sequence can add molecular support to the evaluation of an agent as a carcinogen as it can be used as a conceptual framework for organising and evaluating the strength of existing evidence.

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.

Benzo(a)pyrene enhances the EMT-associated migration of lung adenocarcinoma A549 cells by upregulating Twist1

Benzo(a)pyrene (BaP), an important toxic component of cigarette smoke, can cause lung cancer and lead to the progression of lung cancer. In the present study, we investigated the effect of BaP on the migration of lung adenocarcinoma A549 cells. BaP (1 µM) promoted the migration of A549 cells in a time-dependent manner and upregulated the expression of the Twist family BHLH transcription factor 1 (Twist1). BaP also induced upregulation of the mesenchymal markers N-cadherin and vimentin and downregulation of the epithelial marker E-cadherin. When the expression of Twist1 was knocked down in A549 cells that were treated with BaP for 4 weeks (A549BaP-4w), the expression of Twist1 decreased, which inhibited the migration capacity of A549BaP-4w cells, the expression of N-cadherin and vimentin was downregulated and the expression of E-cadherin was upregulated. In addition, morphological observations of A549BaP-4w cells revealed that the epithelial characteristics of A549 cells became mesenchymal characteristics. When the expression of Twist1 was knocked down, the A549BaP-4w cells were transformed back to cells with epithelial characteristics. In conclusion, the results from the present study indicate that BaP enhances the epithelial-mesenchymal transition-associated migration of lung adenocarcinoma A549 cells by upregulating Twist1.

Phytotherapeutic approach: a new hope for polycyclic aromatic hydrocarbons induced cellular disorders, autophagic and apoptotic cell death

Polycyclic aromatic hydrocarbons (PAHs) comprise the major class of cancer-causing chemicals and are ranked ninth among the chemical compounds threatening to humans. Moreover, interest in PAHs has been mainly due to their genotoxic, teratogenic, mutagenic and carcinogenic property. Polymorphism in cytochrome P450 (CYP450) and aryl hydrocarbon receptor (AhR) has the capacity to convert procarcinogens into carcinogens, which is an imperative factor contributing to individual susceptibility to cancer development. The carcinogenicity potential of PAHs is related to their ability to bind to DNA, thereby enhances DNA cross-linking, causing a series of disruptive effects which can result in tumor initiation. They induce cellular toxicity by regulating the generation of reactive oxygen species (ROS), which arbitrate apoptosis. Additionally, cellular toxicity-mediated apoptotic and autophagic cell death and immune suppression by industrial pollutants PAH, provide fertile ground for the proliferation of mutated cells, which results in cancer growth and progression. PAHs play a foremost role in angiogenesis necessary for tumor metastasization by promoting the upregulation of metalloproteinase-9 (MMP-9), vascular endothelial growth factor (VEGF) and hypoxia inducible factor (HIF) in human cancer cells. This review sheds light on the molecular mechanisms of PAHs induced cancer development as well as autophagic and apoptotic cell death. Besides that authors have unraveled how phytotherapeutics is an alternate potential therapeutics acting as a savior from the toxic effects of PAHs for safer and cost effective perspectives.

Hydroxyl metabolite of PCB 180 induces DNA damage signaling and enhances the DNA damaging effect of benzo[a]pyrene

Non-dioxin-like (NDL) polychlorinated biphenyls (PCBs) and their hydroxyl metabolites (OH-PCBs) are ubiquitous environmental contaminants in human tissues and blood. The toxicological impact of these metabolites is poorly understood. In this study rats were exposed to ultrapure PCB180 (10-1000mg/kgbw) for 28days and induction of genotoxic stress in liver was investigated. DNA damage signaling proteins (pChk1Ser317 and γH2AXSer319) were increased dose dependently in female rats. This increase was paralleled by increasing levels of the metabolite 3'-OH-PCB180. pChk1 was the most sensitive marker. In in vitro studies HepG2 cells were exposed to 1μM of PCB180 and 3'-OH-PCB180 or the positive control benzo[a]pyrene (BaP, 5μM). 3'-OH-PCB180, but not PCB180, induced CYP1A1 mRNA and γH2AX. CYP1A1 mRNA induction was seen at 1h, and γH2AX at 3h. The anti-oxidant N-Acetyl-l-Cysteine (NAC) completely prevented, and 17β-estradiol amplified the γH2AX induction by 3'-OH-PCB180. As 3'-OH-PCB180 induced CYP1A1, a major BaP-metabolizing and activating enzyme, interactions between 3'-OH-PCB180 and BaP was also studied. The metabolite amplified the DNA damage signaling response to BaP. In conclusion, metabolism of PCB180 to its hydroxyl metabolite and the subsequent induction of CYP1A1 seem important for DNA damage induced by PCB180 in vivo. Amplification of the response with estradiol may explain why DNA damage was only seen in female rats.

Polycyclic aromatic hydrocarbons and cytochrome P450 in HIV pathogenesis

High prevalence of cigarette smoking in HIV patients is associated with increased HIV pathogenesis and disease progression. While the effect of smoking on the occurrence of lung cancer has been studied extensively, the association between smoking and HIV pathogenesis is poorly studied. We have recently shown the possible role of cytochrome P450 (CYP) in smoking/nicotine-mediated viral replication. In this review, we focus on the potential role of CYP pathway in polycyclic aromatic hydrocarbons (PAH), important constituents of cigarette smoke, mediated HIV pathogenesis. More specifically, we will discuss the role of CYP1A1 and CYP1B1, which are the major PAH-activating CYP enzymes. Our results have shown that treatment with cigarette smoke condensate (CSC) increases viral replication in HIV-infected macrophages. CSC contains PAH, which are known to be activated by CYP1A1 and CYP1B1 into procarcinogens/toxic metabolites. The expression of these CYPs is regulated by aryl hydrocarbon receptors (AHR), the cellular target of PAH, and an important player in various diseases including cancer. We propose that PAH/AHR-mediated CYP pathway is a novel target to develop new interventions for HIV positive smokers.