Diversified expression of aryl hydrocarbon receptor dependent genes in human laryngeal squamous cell carcinoma cell lines treated with β-naphthoflavone

The aryl hydrocarbon receptor (AhR) mediates a variety of biological responses to ubiquitous environmental pollutants. In this study the effect of administration of β-naphthoflavone (BNF), potent AhR ligand, on the expression of AhR, AhRR, CYP1A1, CYP1A2, CYP1B1, NQO1, GSTA1, ALDH3A1 and UGT1A genes encoding the enzymes controlled by AhR were examined in thirteen laryngeal tumor cell lines and in HepaRG cell line. The analyzed cell lines were derived from patients with squamous laryngeal cancer, with history of cigarette smoking and without signs of human papillomavirus types 16 and 18 infection in investigated cells. Quantitative real-time RT-PCR analysis revealed huge interindividual differences in expression of genes from AhR regulatory network. Our results strongly suggest predominant effect of DNA methylation on induction of CYP1A1 expression by AhR ligands as well. Our results indicate that differentiated HepaRG cell line appeared to be very good substitute for human liver in studies on xenobiotic metabolism by AhR regulated enzymes.     

Aberrant methylation accounts for cell adhesion-related gene silencing during 3-methylcholanthrene and diethylnitrosamine induced multistep rat lung carcinogenesis associated with overexpression of DNA methyltransferases 1 and 3a

To evaluate the significance of alterations in cell adhesion-related genes methylation during lung multistep carcinogenesis induced by the genotoxic carcinogens 3-methylcholanthrene (MCA) and diethylnitrosamine (DEN), tissue samples microdissected from MCA/DEN-induced rat lung carcinogenesis model were subjected to methylation-specific PCR to evaluate the DNA methylation status of CADM1, TIMP3, E-cadherin and N-cadherin. Immunohistochemistry was used to determine protein expression of CADM1, TIMP3, N-cadherin and the DNA methyltransferases (DNMTs) 1, 3a and 3b. E-cadherin hypermethylation was not detected in any tissue. CADM1, TIMP3 and N-cadherin hypermethylation was correlated with the loss of their protein expression during the progression of pathologic lesions. The prevalence of DNA methylation of at least one gene and the average number of methylated genes increased with the histological progression. DNMT1 and DNMT3a protein expression increased progressively during the stages of lung carcinogenesis, whereas DNMT3b overexpression was only found in several samples. Furthermore, DNMT1 protein expression levels were correlated with CADM1 methylation, and DNMT3a protein expression levels were correlated with CADM1, TIMP3 and N-cadherin methylation. The average number of methylated genes during carcinogenesis was significantly correlated with DNMT1 and DNMT3a protein expression levels. Moreover, mRNA expression of CADM1 significantly increased after treatment with DNMT inhibitor 5-aza-2′-deoxycytidine in CADM1-methylated primary tumor cell lines. Our findings suggest that an accumulation of hypermethylation accounts for cell adhesion-related gene silencing is associated with dynamic changes in the progression of MCA/DEN-induced rat lung carcinogenesis. We suggest that DNMT1 and DNMT3a protein overexpression may be responsible for this aberrant DNA methylation.     

Grape seed proanthocyanidins reactivate silenced tumor suppressor genes in human skin cancer cells by targeting epigenetic regulators

Grape seed proanthocyanidins (GSPs) have been shown to have anti-skin carcinogenic effects in in vitro and in vivo models. However, the precise epigenetic molecular mechanisms remain unexplored. This study was designed to investigate whether GSPs reactivate silenced tumor suppressor genes following epigenetic modifications in skin cancer cells. For this purpose, A431 and SCC13 human squamous cell carcinoma cell lines were used as in vitro models. The effects of GSPs on DNA methylation, histone modifications and tumor suppressor gene expressions were studied in these cell lines using enzyme activity assays, western blotting, dot-blot analysis and real-time polymerase chain reaction (RT-PCR). We found that treatment of A431 and SCC13 cells with GSPs decreased the levels of: (i) global DNA methylation, (ii) 5-methylcytosine, (iii) DNA methyltransferase (DNMT) activity and (iv) messenger RNA (mRNA) and protein levels of DNMT1, DNMT3a and DNMT3b in these cells. Similar effects were noted when these cancer cells were treated identically with 5-aza-2′-deoxycytidine, an inhibitor of DNA methylation. GSPs decreased histone deacetylase activity, increased levels of acetylated lysines 9 and 14 on histone H3 (H3-Lys 9 and 14) and acetylated lysines 5, 12 and 16 on histone H4, and reduced the levels of methylated H3-Lys 9. Further, GSP treatment resulted in re-expression of the mRNA and proteins of silenced tumor suppressor genes, RASSF1A, p16^INK4a and Cip1/p21. Together, this study provides a new insight into the epigenetic mechanisms of GSPs and may have significant implications for epigenetic therapy in the treatment/prevention of skin cancers in humans.     

DNA methylation and breast cancer

DNA methylation and chromatin structure patterns are tightly linked components of the epigenome, which regulate gene expression programming. Two contradictory changes in DNA methylation patterns are observed in breast cancer; regional hypermethylation of specific genes and global hypomethylation. It is proposed here that independent mechanisms are responsible for these alterations in DNA methylation patterns and that these alterations deregulate two different processes in breast cancer. Regional hypermethylation is brought about by specific regional changes in chromatin structure, whereas global demethylation is caused by a general increase in demethylation activity. Hypermethylation silences growth regulatory genes resulting in uncontrolled growth whereas hypomethylation leads to activation of genes required for metastasis. DNA methylation inhibitors activate silenced tumor suppressor genes resulting in arrest of tumor growth and are now being tested as candidate anticancer drugs. Demethylation inhibitors are proposed here to be potential novel candidate antimetastatic agents, which would bring about methylation and silencing of metastatic genes. Future therapeutic application of either methylation or demethylation inhibitors in cancer therapy would require understanding of the relative role of these processes in the evolution of cancer.     

RNAi沉默PCDGF基因对喉鳞癌Hep-2细胞生物学特性的影响

目的 研究RNAi沉默畸胎瘤细胞源性生长因子（PCDGF）表达对喉鳞癌Hep-2细胞增殖、凋亡及侵袭能力的影响。方法 RT-PCR检测喉鳞癌组织中PCDGF的mRNA表达水平;Hep-2细胞分为空白对照组、阴性对照组和PCDGF-siRNA组,Western blot检测转染效果及Bcl-2、Bax、E-cadherin和MUC1蛋白表达;CCK8实验检测细胞增殖;流式细胞仪检测细胞凋亡;Transwell 小室检测细胞侵袭能力。结果 喉鳞癌组织中的PCDGF mRNA表达水平显著高于声带息肉组织（t=6.88,P=0.005）。PCDGF在喉鳞癌组织中高表达。PCDGF-siRNA组喉鳞癌Hep-2细胞中PCDGF、Bcl-2、MUCI蛋白表达显著低于空白对照组（P<0.05）,Bax、E-cadherin蛋白表达显著高于空白对照组（P<0.05）,细胞增殖率显著低于空白对照组（P<0.05）,细胞侵袭数显著低与空白对照组（P<0.05）,细胞凋亡率显著高于空白对照组（P<0.05）。结论 抑制PCDGF的表达能够抑制喉鳞癌Hep-2细胞的增殖和侵袭能力,诱导细胞发生凋亡。     

DNA methylation of Hugl‐2 is a prognostic biomarker in kidney renal clear cell carcinoma

It has been reported that loss of Hugl‐2 contributes to tumour formation and progression in vitro and in vivo. However, whether Hugl‐2 levels decrease during kidney renal clear cell carcinoma (KIRC) and the mechanism involved remain unknown. This study aimed to investigate whether DNA methylation of Hugl‐2 reduces its expression, leading to the progression and poor prognosis of KIRC. Hugl‐2 methylation and mRNA expression and KIRC clinicopathological data were extracted from The Cancer Genome Atlas (TCGA), and relationships among these factors were analyzed using UALCAN, MethHC, Wanderer and LinkedOmics web tools. We found that Hugl‐2 mRNA and protein levels were reduced in KIRC tissues. Moreover, Hugl‐2 mRNA levels were related to tumour grade and overall survival, and Hugl‐2 methylation was increased in KIRC. According to the results of methylation‐specific PCR, KIRC cells had higher Hugl‐2 DNA methylation levels than HKC cells. Moreover, Hugl‐2 DNA methylation correlated negatively with Hugl‐2 mRNA and was also related to the pathology and T stage of KIRC patients. KIRC patients with high Hugl‐2 DNA methylation also had shorter overall survival. Additionally, methylation of cg08827674, a Hugl‐2 probe, was related to pathologic stage, T stage, neoplasm histologic grade, serum calcium level without laterality, M stage, N stage, and ethnicity. Furthermore, treatment with the DNA methylation inhibitor decitabine resulted in upregulation of Hugl‐2 mRNA and protein levels in KIRC cell lines. These results indicate that Hugl‐2 DNA methylation may be both a prognostic marker and a therapeutic target in KIRC.     

Benzopyrene exposure disrupts DNA methylation and growth dynamics in breast cancer cells

Exposures to environmental carcinogens and unhealthy lifestyle choices increase the incidence of breast cancer. One such compound, benzo(a)pyrene (BaP), leads to covalent DNA modifications and the deregulation of gene expression. To date, these mechanisms of BaP-induced carcinogenesis are poorly understood, particularly in the case of breast cancer. We tested the effects of BaP exposure on cellular growth dynamics and DNA methylation in four breast cancer cell lines since disruptions in DNA methylation lead to deregulated gene expression and the loss of genomic integrity. We observed robust time- and concentration-dependent loss of proliferation, S phase and G2M accumulation and apoptosis in p53 positive MCF-7 and T47-D cells. We observed minimal responses in p53 negative HCC-1086 and MDA MB 231 cells. Furthermore, BaP increased p53 levels in both p53 positive cell lines, as well as p21 levels in MCF-7 cells, an effect that was prevented by the p53-specific inhibitor pifithrin-alpha. No changes in global levels of DNA methylation levels induced by BaP were detected by the methyl acceptor assay (MAA) in any cell line, however, methylation profiling by AIMS (amplification of intermethylated sites) analysis showed dynamic, sequence-specific hypo- and hypermethylation events in all cell lines. We also identified BaP-induced hypomethylation events at a number of genomic repeats. Our data confirm the p53-specific disruption of the cell cycle as well as the disruption of DNA methylation as a consequence of BaP treatment, thus reinforcing the link between environmental exposures, DNA methylation and breast cancer.     

表没食子儿茶素没食子酸酯通过下调表皮生长因子受体发挥抑制喉癌细胞的作用机制研究

目的 探究表没食子儿茶素没食子酸酯(epigallocatechin-3-gallate,EGCG)抑制喉癌细胞的作用机制。方法 利用Western blotting检测喉癌细胞株AMC-HN-8、TU686和TU212中表皮生长因子受体(epidermal growth factor receptor,EGFR)的表达,并采用CCK-8法检测西妥昔单抗和EGCG对3种喉癌细胞的抑制作用;构建含有EGFR启动子以及Luc报告基因的慢病毒载体并感染TU686细胞,获得EGFR启动子调控表达荧光素酶的TU686-EGFR-Luc报告基因细胞系,检测EGCG处理后的荧光素酶活性;利用流式细胞术检测EGCG作用后的喉癌细胞的细胞周期和凋亡情况,并用Western blotting检测分析EGFR及下游信号通路分子ERK的表达与活化、细胞周期相关分子P53及P27、凋亡相关分子BCL2及PARP、自噬相关指标LC3A/B的水平情况。结果 喉癌细胞株对西妥昔单抗不敏感,但EGCG能有效抑制喉癌细胞的生长;EGCG能有效抑制EGFR启动子的转录活性;在亚IC₅₀剂量的EGCG作...     

T2-T3级喉鳞状细胞癌区域性颈淋巴清扫术的选择

【摘要】 <正>颈部淋巴结转移是影响喉癌治愈率的主要因素之一。对于已侵及声门上、下区的T2-T3级喉鳞状细胞癌患者,因发生颈部淋巴转移的概率较高,一般行常规颈部淋巴清扫术,而过大的手术范围及过长的手术时间,会使术后伤口感染率增高。本研究旨在比较对淋巴结转移阴性患者施行清扫和未施行清扫的愈后结果,报告如下。     

TET-mediated DNA demethylation plays an important role in arsenic-induced HBE cells oxidative stress via regulating promoter methylation of OGG1 and GSTP1

Environmental exposure to arsenic remains a worldwide public health challenge. Oxidative stress and aberrant DNA methylation are both characteristics of arsenic toxicology; however, the relationship between these is not well understood. Ten-eleven translocation (TET1, TET2 and TET3), which is the conversion of 5-methylcytosine (5mC) to 5-hydroxymethylcytosine (5hmC), plays a central role in the DNA demethylation process. Further, it can prevent cytosine-phosphate-guanine (CpG) islands from developing abnormal hypermethylation under oxidative stress. Here, we observed that NaAsO₂ could induce oxidative stress in human bronchial epithelial (HBE) cells. This was accompanied by an inhibition of TET-mediated DNA demethylation. Subsequent results showed that TET1 and TET2 siRNA led to further inhibition of genome 5hmC and a higher level of oxidative stress in NaAsO₂-treated HBE cells. Conversely, l-ascorbic acid enhanced TET proteins and effectively upregulated 5hmC, which antagonized the NaAsO₂-induced oxidative stress. Additionally, the TETs positively regulated the promoter methylation of the antioxidant genes 8-oxoguanine DNA glycosylase (OGG1) and glutathione S-transferase Pi 1 (GSTP1). Taken together, the results indicate that arsenic induced the inhibition of TET-mediated DNA demethylation, which induced promoter hypermethylation, inhibiting the expression of the OGG1 and GSTP1, and increasing oxidative stress in lung cells in vitro. l-ascorbic acid effectively alleviated arsenic-induced oxidative stress by restoring TET function.     

LncRNA KCNQ1OT1通过调控 miR-506-3p表达调节喉鳞状细胞癌细胞的生物学行为

目的 探讨长链非编码RNA(LncRNA)KCNQ1重叠转录物1(KCNQ1OT1)对喉鳞状细胞癌细胞生物学的影响及作用机制.方法 于2019年5月至2020年2月,采用RT-qPCR法检测了45例来自山东大学齐鲁医院桓台分院喉鳞状细胞癌病人的癌组织和癌旁组织及购自上海研生实业有限公司的人胚肺成纤维细胞WI-38和购自中国科学院上海细胞库的喉鳞状细胞癌细胞系(EV-SCC-18、AMC-HN-8和HCC345)中KCNQ1OT1和miR-506-3p表达.以HCC345细胞为研究对象,转染KCNQ1OT1小干扰RNA或共转染KCNQ1OT1小干扰RNA与miR-506-3p抑制剂至HCC345细胞后,MTT法、流式细胞术、Transwell分别检测细胞增殖、凋亡、迁移和侵袭.双荧光素酶报告基因实验验证KCNQ1OT1与miR-506-3p的调控关系.结果 喉鳞状细胞癌组织中KCNQ1OT1表达高于癌旁组织[(0.81±0.09)比(0.27±0.08)],miR-506-3p表达低于癌旁组织[(0.24±0.08)比(0.83±0.09)].喉鳞状细胞癌细胞系(EV-SCC-18、AMC-HN-8和HCC345)中KCNQ1OT1表达均高于WI-38细胞[(2.44±0.22)、(2.69±0.21)、(3.61±0.24)比(1.00±0.13)],miR-506-3p表达均低于WI-38细胞[(0.41±0.13)、(0.30±0.12)、(0.22±0.11)比(1.00±0.12)].与未敲减KCNQ1OT1的HCC345细胞比较,敲减KCNQ1OT1的HCC345细胞活力[(0.41±0.06)比(0.81±0.12)]、迁移数[(86.32±15.21)个比(162.31±20.23)个]和侵袭数[(65.23±12.05)个比(140.26±18.27)个]均降低,细胞凋亡率升高[(34.13±3.60)％比(3.79±2.37)％].KCNQ1OT1在HCC345细胞中负调控miR-506-3p表达.敲减miR-506-3p逆转敲减KCNQ1OT1对HCC345细胞增殖、凋亡、迁移和侵袭的影响.结论 KCNQ1OT1在喉鳞状细胞癌组织和细胞系中表达升高,其通过靶向miR-506-3p促进喉鳞状细胞癌细胞的恶性生物学行为.     

Constitutive activation of the ATM/BRCA1 pathway prevents DNA damage-induced apoptosis in 5-azacytidine-resistant cell lines

5-Azacytidine (AZA) exerts its anti-tumor effects by exerting cytotoxicity via its incorporation into RNA and DNA, which causes the reactivation of aberrantly silenced growth-regulatory genes by promoter demethylation, as well as DNA damage. AZA is used for patients with myelodysplastic syndrome and acute myeloid leukemia. However, some patients demonstrate resistance to AZA, the mechanisms of which are not fully elucidated. We therefore sought to better characterize the molecular mechanism of AZA resistance using an in vitro model of AZA resistance. We established AZA-resistant cell lines by exposing the human leukemia cell lines U937 and HL-60 to clinical concentrations of AZA, and characterized these cells. AZA-resistant cells showed a down-regulation of the DNMT3A protein, in correlation with their marked genome-wide DNA hypomethylation. Furthermore, genes involved in pyrimidine metabolism were down-regulated in both AZA-resistant cell lines; AZA sensitivity was restored by inhibition of CTP synthase. Of note is that the DNA damage response pathway is constitutively activated in the AZA-resistant cell lines, but not in the parental cell lines. Inhibition of the DNA damage response pathway canceled the AZA resistance, in association with an increase in apoptotic cells. We found that the molecular mechanism underlying AZA resistance involves pyrimidine metabolism and the DNA damage response through ATM kinase. This study therefore sheds light on the mechanisms underlying AZA resistance, and will enable better understanding of AZA resistance in patients undergoing AZA treatment.     

Nutlin-3-induced redistribution of chromatin-bound IFI16 in human hepatocellular carcinoma cells in vitro is associated with p53 activation

Aim:

Interferon-γ inducible protein 16 (IFI16), a DNA sensor for DNA double-strand break (DSB), is expressed in most human hepatocellular carcinoma cell (HCC) lines. In this study we investigated the re-localization of chromatin-bound IFI16 by Nutlin-3, a DNA damage agent, in HCC cells in vitro, and the potential mechanisms.

Methods:

Human HCC SMMC-7721 (wild-type TP53), Huh-7 (mutant TP53), Hep3B (null TP53) and normal fetal liver L02 cell lines were examined. DSB damage in HCC cells was detected via γH2AX expression and foci formation assay. The expression of IFI16 and IFNB mRNA was measured using RT-PCR, and subcellular localization and expression of the IFI16 protein were detected using chromatin fractionation, Western blot analysis, and fluorescence microscopy.

Results:

Treatment of SMMC-7721 cells with Nutlin-3 (10 μmol/L) or etoposide (40 μmol/L) induced significant DSB damage. In SMMC-7721 cells, Nutlin-3 significantly increased the expression levels of IFI16 and IFNB mRNA, and partially redistributed chromatin-bound IFI16 protein to the cytoplasm. These effects were blocked by pretreatment with pifithrin-α, a p53 inhibitor. Furthermore, Nutlin-3 did not induce ectopic expression of IFI16 protein in Huh-7 and Hep3B cells. Moreover, the association of IFI16 with chromatin and Nutlin-3-induced changes in localization were not detected in L02 cells.

Conclusion:

Nutlin-3 regulates the subcellular localization of IFI16 in HCC cells in vitro in a p53-dependent manner.     

KS900: A hypoxia-directed, reductively activated methylating antitumor prodrug that selectively ablates O-alkylguanine-DNA alkyltransferase in neoplastic cells

To most effectively treat cancer it may be necessary to preferentially destroy tumor tissue while sparing normal tissues. One strategy to accomplish this is to selectively cripple the involved tumor resistance mechanisms, thereby allowing the affected anticancer drugs to gain therapeutic efficacy. Such an approach is exemplified by our design and synthesis of the intracellular hypoxic cell activated methylating agent, 1,2-bis(methylsulfonyl)-1-methyl-2-[[1-(4-nitrophenyl)ethoxy]carbonyl]hydrazine (KS900) that targets the O-6 position of guanine in DNA. KS900 is markedly more cytotoxic in clonogenic experiments under conditions of oxygen deficiency than the non-intracellularly activated agents KS90, and 90M, when tested in O⁶-alkylguanine-DNA alkyltransferase (AGT) non-expressing cells (EMT6 mouse mammary carcinoma, CHO/AA8 hamster ovary, and U251 human glioma), and than temozolomide when tested in AGT expressing cells (DU145 human prostate carcinoma). Furthermore, KS900 more efficiently ablates AGT in HL-60 human leukemia and DU145 cells than the spontaneous globally activated methylating agent KS90, with an IC₅₀ value over 9-fold lower than KS90. Finally, KS900 under oxygen-deficient conditions selectively sensitizes DU145 cells to the chloroethylating agent, onrigin, through the ablation of the resistance protein AGT. Thus, under hypoxia, KS900 is more cytotoxic at substantially lower concentrations than methylating agents such as temozolomide that are not preferentially activated in neoplastic cells by intracellular reductase catalysts. The necessity for intracellular activation of KS900 permits substantially greater cytotoxic activity against cells containing the resistance protein O⁶-alkylguanine-DNA alkyltransferase (AGT) than agents such as temozolomide. Furthermore, the hypoxia-directed intracellular activation of KS900 allows it to preferentially ablate AGT pools under the oxygen-deficient conditions that are present in malignant tissue.     

Identification and functional analysis of genes which confer resistance to cisplatin in tumor cells

The efficacy of cisplatin during cancer chemotherapy is often impaired by the emergence of cancer cells which become resistant to chemotherapeutic agents. While various mechanisms have been proposed to explain resistance to cisplatin, the genes involved in this process still remain unclear. By using DNA microarrays, we performed a genome-wide analysis of cisplatin-resistant HeLa cells in order to identify genes involved in resistance. We identified nine genes (NAPA, CITED2, CABIN1, ADM, HIST1H1A, EHD1, MARK2, PTPN21, and MVD), which were consistently upregulated in two cisplatin-resistant HeLa cell lines. The upregulated genes, here referred to as cisplatin resistance genes (CPR), were further analyzed for their ability to modify the response of HEK293 cells to cisplatin. Short-hairpin RNA (shRNA) knockdown of CPR genes, individually or in combination, was shown to sensitize HEK293 cells to cisplatin, but not to vincristine or taxol, suggesting that CPR genes may be involved specifically in cisplatin resistance. Among the treatments performed, shRNA knockdown of NAPA was the most efficient treatment able to sensitize cells to cisplatin. Furthermore, shRNA knockdown of a single CPR gene was sufficient to partially reverse acquired cisplatin resistance in HeLa cells. Sensitization to cisplatin following knockdown of CPR genes was also observed in the tumorigenic cell lines Sk-ov-3, H1155, and CG-1. Based on these results, we propose that the CPR genes identified here may represent potential candidates for novel target therapies aimed at preventing resistance to cisplatin during chemotherapy.     

The effect of dietary polyphenols on the epigenetic regulation of gene expression in MCF7 breast cancer cells

The CpG island methylator phenotype is characterized by DNA hypermethylation in the promoters of several suppressor genes associated with the inactivation of various pathways involved in tumorigenesis. DNA methylation is catalyzed by specific DNA methyltransferases (DNMTs). Dietary phytochemicals particularly catechol-containing polyphenols were shown to inhibit these enzymes and reactivate epigenetically silenced genes.