Specific chemopreventive agents trigger proteasomal degradation of G1 cyclins: implications for combination therapy.

PURPOSE: There is a need to identify cancer chemoprevention mechanisms. We reported previously that all-trans-retinoic acid (RA) prevented carcinogenic transformation of BEAS-2B immortalized human bronchial epithelial cells by causing G(1) arrest, permitting repair of genomic DNA damage. G(1) arrest was triggered by cyclin D1 proteolysis via ubiquitin-dependent degradation. This study investigated which chemopreventive agents activated this degradation program and whether cyclin E was also degraded. EXPERIMENTAL DESIGN: This study examined whether: (a) cyclin E protein was affected by RA treatment; (b) cyclin degradation occurred in derived BEAS-2B-R1 cells that were partially resistant to RA; and (c) other candidate chemopreventive agents caused cyclin degradation. RESULTS: RA treatment triggered degradation of cyclin E protein, and ALLN, a proteasomal inhibitor, inhibited this degradation. Induction of the retinoic acid receptor beta, growth suppression, and cyclin degradation were each inhibited in BEAS-2B-R1 cells. Transfection experiments in BEAS-2B cells indicated that RA treatment repressed expression of wild-type cyclin D1 and cyclin E, but ALLN inhibited this degradation. Mutation of threonine 286 stabilized transfected cyclin D1, and mutations of threonines 62 and 380 stabilized transfected cyclin E, despite RA treatment. Specific chemopreventive agents triggered cyclin degradation. Nonclassical retinoids (fenretinide and retinoid X receptor agonists) and a synthetic triterpenoid (2-cyano-3,12-dioxooleana-1,9-dien-28-oic acid) each suppressed BEAS-2B growth and activated this degradation program. However, a vitamin D3 analog (RO-24-5531), a cyclooxygenase inhibitor (indomethacin), and a peroxisome proliferator-activated receptor gamma agonist (rosiglitazone) each suppressed BEAS-2B growth, but did not cause cyclin degradation. BEAS-2B-R1 cells remained responsive to nonclassical retinoids and to 2-cyano-3,12-dioxooleana-1,9-dien-28-oic acid. CONCLUSIONS: Specific chemopreventive agents activate cyclin proteolysis. Yet, broad resistance did not occur after acquired resistance to a single agent. This provides a therapeutic rationale for combination chemoprevention with agents activating non-cross-resistant pathways.     

Microarray analyses uncover UBE1L as a candidate target gene for lung cancer chemoprevention

Retinoids, natural and synthetic derivatives of vitamin A, are active in cancer therapy and chemoprevention. We reported previously that all-trans-retinoic acid (RA) treatment prevented carcinogen-induced transformation of immortalized human bronchial epithelial (HBE) cells. To identify cancer chemopreventive mechanisms, immortalized (BEAS-2B), carcinogen-transformed (BEAS-2B(NNK)), and RA-chemoprevented (BEAS-2B(NNK/RA)) HBE cells were used to conduct microarray analyses independently. Species increased in chemoprevented as compared with immortalized HBE cells (group I) and those augmented in chemoprevented as compared with transformed HBE cells (group II) included known RA-target genes as well as previously unrecognized RA-target genes in HBE cells. Unexpectedly, both groups were also enriched for interferon-stimulated genes. One interferon-stimulated gene of particular interest was UBE1L, the ubiquitin-activating enzyme E1-like protein. UBE1L expression was also induced after prolonged RA-treatment of immortalized HBE cells. UBE1L mRNA was shown previously as repressed in certain lung cancer cell lines, directly implicating UBE1L in lung carcinogenesis. Notably, UBE1L immunoblot expression was reduced in a subset of malignant as compared with adjacent normal lung tissues that were examined. Immunohistochemical analyses were performed using a new assay developed to detect this species using rabbit polyclonal anti-UBE1L antibodies independently raised against the amino- or carboxyl-termini of UBE1L. Studies done on paraffin-embedded and fixed tissues revealed abundant UBE1L, but low levels of cyclin D1 expression in the normal human bronchial epithelium, indicating an inverse relationship existed between these species. To study this further, cotransfection into HBE cells of wild-type or mutant UBE1L species was accomplished. In a dose-dependent manner, wild-type but not mutant UBE1L species repressed cyclin D1 expression. This implicated UBE1L in a retinoid chemoprevention mechanism involving cyclin D1 repression described previously. Taken together, these findings directly implicate UBE1L as a candidate-pharmacologic target for lung cancer chemoprevention. These findings also provide a mechanistic basis for the tumor suppressive effects of UBE1L through cyclin D1 repression.     

Cyclin D1 proteolysis: a retinoid chemoprevention signal in normal, immortalized, and transformed human bronchial epithelial cells

BACKGROUND: Retinoids (derivatives of vitamin A) are reported to reduce the occurrence of some second primary cancers, including aerodigestive tract tumors. In contrast, beta-carotene does not reduce the occurrence of primary aerodigestive tract cancers. Mechanisms explaining these effective retinoid and ineffective carotenoid chemoprevention results are poorly defined. Recently, the all-trans-retinoic acid (RA)-induced proteolysis of cyclin D1 that leads to the arrest of cells in G1 phase of the cell cycle was described in human bronchial epithelial cells and is a promising candidate for such a mechanism. In this study, we have investigated this proteolysis as a common signal used by carotenoids or receptor-selective and receptor-nonselective retinoids. METHODS: We treated cultured normal human bronchial epithelial cells, immortalized human bronchial epithelial cells (BEAS-2B), and transformed human bronchial epithelial cells (BEAS-2BNNK) with receptor-selective or receptor-nonselective retinoids or with carotenoids and studied the effects on cell proliferation by means of tritiated thymidine incorporation and on cyclin D1 expression by means of immunoblot analysis. We also examined whether calpain inhibitor I, an inhibitor of the 26S proteasome degradation pathway, affected the decline (i.e., proteolysis) of cyclin D1. RESULTS: Receptor-nonselective retinoids were superior to the carotenoids studied in mediating the decline in cyclin D1 expression and in suppressing the growth of bronchial epithelial cells. Retinoids that activated retinoic acid receptor beta or retinoid X receptor pathways preferentially led to a decrease in the amount of cyclin D1 protein and a corresponding decline in growth. The retinoid-mediated degradation of cyclin D1 was blocked by cotreatment with calpain inhibitor I. CONCLUSIONS: Retinoid-dependent cyclin D1 proteolysis is a common chemoprevention signal in normal and neoplastic human bronchial epithelial cells. In contrast, carotenoids did not affect cyclin D1 expression. Thus, the degradation of cyclin D1 is a candidate intermediate marker for effective retinoid-mediated cancer chemoprevention in the aerodigestive tract.     

Evidence for the epidermal growth factor receptor as a target for lung cancer prevention.

PURPOSE: There is a need to identify lung cancer prevention mechanisms. All-trans-retinoic acid (RA) was reported previously to inhibit N-nitrosamine-4-(methylnitrosamino)-1-(3 pyridyl)-1-butanone (NNK) carcinogenic transformation of BEAS-2B human bronchial epithelial cells (J. Langenfeld et al., Oncogene, 13: 1983-1990, 1996). This study was undertaken to identify pathways targeted during this chemoprevention. Experimental Design: Because epidermal growth factor receptor (EGFR) overexpression is frequent in non-small cell lung cancers (NSCLC) and bronchial preneoplasia, BEAS-2B cells, carcinogen-transformed BEAS-2B(NNK) cells, and retinoid chemoprevented BEAS-2B(NNK RA) cells were each examined for EGFR expression. Whether RA treatment regulated directly EGFR expression or reporter plasmid activity was studied. RA effects on epidermal growth factor (EGF) induction of EGFR-phosphotyrosine levels, cyclin D1 expression and mitogenesis were examined in BEAS-2B cells. RESULTS: Findings reveal that NNK-mediated transformation of BEAS-2B cells increased EGFR expression. RA treatment repressed EGFR expression and reporter plasmid activity in these cells. This treatment reduced EGF-dependent mitogenesis as well as EGFR-associated phosphotyrosine levels and cyclin D1 expression. These findings extend prior work by highlighting EGFR as a chemoprevention target in the lung. Notably, RA treatment prevented transformation as well as outgrowth of EGFR overexpressing bronchial epithelial cells, despite NNK exposure. After acute NNK exposure, p53-induced species that appear after DNA damage or oxidative stress were evident before an observed increase in EGFR expression. CONCLUSIONS: These findings indicate how effective chemoprevention prevents carcinogenic transformation of bronchial epithelial cells when repair of genomic damage does not select against EGFR overexpressing cells. This implicates EGFR as a chemoprevention target in the carcinogen-exposed bronchial epithelium.     

Tumor necrosis factor-alpha increases reactive oxygen species by inducing spermine oxidase in human lung epithelial cells: a potential mechanism for inflammation-induced carcinogenesis

Inflammation has been implicated in the development of many human epithelial cancers, including those of the stomach, lung, colon, and prostate. Tumor necrosis factor-alpha (TNF-alpha) is a potent pleiotropic, proinflammatory cytokine produced by many cells in response to injury and inflammation. Here, we show that TNF-alpha exposure results in increased production of reactive oxygen species (ROS), with a concomitant increase in the production of 8-oxo-deoxyguanosine, a marker for oxidative DNA damage, in human lung bronchial epithelial cells. The source of the ROS in TNF-alpha-treated cells was determined by both pharmacologic and small interfering RNA (siRNA) strategies to be spermine oxidase (SMO/PAOh1). SMO/PAOh1 oxidizes spermine into spermidine, 3-aminopropanal, and H(2)O(2). Inhibition of TNF-alpha-induced SMO/PAOh1 activity with MDL 72,527 or with a targeted siRNA prevented ROS production and oxidative DNA damage. Further, similar induction in SMO/PAOh1 is observed with treatment of another inflammatory cytokine, interleukin-6. The data are consistent with a model that directly links inflammation and DNA damage through the production of H(2)O(2) by SMO/PAOh1. Further, these results suggest a common mechanism by which inflammation from multiple sources can lead to the mutagenic changes necessary for the development and progression of epithelial cancers.     

Neoplastic transformation of a human bronchial epithelial cell line by a recombinant retrovirus encoding viral Harvey ras

Activated ras oncogenes have previously been implicated in the pathogenesis of human lung carcinomas. A v-Ha-ras-containing retrovirus, Zip-ras, was generated by inserting the coding region of the v-Ha-ras oncogene into the Zip-NeoSV(X) [Cepko et al., Cell 37:1053-1062, 1984] retroviral vector. Amphotrophic Zip-ras retrovirus was used to infect an SV40 large T antigen-positive immortalized cell line, BEAS-2B, derived from normal bronchial epithelial cells, the predominant progenitor cells of human lung carcinomas. Zip-ras-infected BEAS-2B cells selected for G418 resistance formed anaplastic carcinomas in 12 of 15 athymic nude mice (latency 3 wk), whereas Zip-NeoSV(X)-infected BEAS-2B control cultures inoculated into 12 nude mice formed no tumors after a minimum of 7 mo. Tumor cell lines were established and demonstrated to be of human epithelial origin and to express v-Ha-ras p21 protein. A common feature of the tumor cell lines was an increase in ploidy. The increased efficiency of neoplastic transformation by v-Ha-ras of cell lines as compared with our previous results with normal bronchial epithelial cells [Yoakum et al., Science 227:1174-1179, 1985] is consistent with the hypothesis that the "immortalization" step is rate-limiting in in vitro human epithelial cell carcinogenesis.     

土槿乙酸增强9顺式维甲酸对白血病细胞生长的抑制作用

目的观察过氧化物酶体激活物活化受体γ (PPARγ)的配体土槿乙酸(PLAB)联合维甲类X受体α (RXRα)的配体9-顺式维甲酸(9-cis RA)对白血病细胞生长的影响。方法应用MTT 法检测细胞生长抑制率,流式细胞术和Hoechst33342/PI染色分析HL-60细胞凋亡及细胞周期变化,RT-PCR检测PPARγ和RXRα mRNA表达。结果HL-60细胞系上有PPARγ和RXRα的表达,经配体联合作用后能明显抑制细胞生长,呈剂量依赖关系;细胞出现明显凋亡形态学改变和亚G₁峰;PPARγ和RXRα mRNA表达明显增强。结论PLAB能显著增强9-cis RA对HL-60细胞的生长抑制作用,其机制与凋亡诱导效应有关。     

Spermine oxidation induced by Helicobacter pylori results in apoptosis and DNA damage: implications for gastric carcinogenesis

Oxidative stress is linked to carcinogenesis due to its ability to damage DNA. The human gastric pathogen Helicobacter pylori exerts much of its pathogenicity by inducing apoptosis and DNA damage in host gastric epithelial cells. Polyamines are abundant in epithelial cells, and when oxidized by the inducible spermine oxidase SMO(PAOh1) H(2)O(2) is generated. Here, we report that H. pylori up-regulates mRNA expression, promoter activity, and enzyme activity of SMO(PAOh1) in human gastric epithelial cells, resulting in DNA damage and apoptosis. H. pylori-induced H(2)O(2) generation and apoptosis in these cells was equally attenuated by an inhibitor of SMO(PAOh1), by catalase, and by transient transfection with small interfering RNA targeting SMO(PAOh1). Conversely, SMO(PAOh1) overexpression induced apoptosis to the same levels as caused by H. pylori. Importantly, in H. pylori-infected tissues, there was increased expression of SMO(PAOh1) in both human and mouse gastritis. Laser capture microdissection of human gastric epithelial cells demonstrated expression of SMO(PAOh1) that was significantly attenuated by H. pylori eradication. These results identify a pathway for oxidative stress-induced epithelial cell apoptosis and DNA damage due to SMO(PAOh1) activation by H. pylori that may contribute to the pathogenesis of the infection and development of gastric cancer.     

A proof-of-principle clinical trial of bexarotene in patients with non-small cell lung cancer.

PURPOSE: Bexarotene is a rexinoid (selective retinoid X receptor agonist) that affects proliferation, differentiation, and apoptosis in preclinical studies. The relationship between bexarotene levels and biomarker changes in tumor tissues has not been previously studied. EXPERIMENTAL DESIGN: BEAS-2B human bronchial epithelial (HBE) cells, retinoid-resistant BEAS-2B-R1 cells, A427, H226, and H358 lung cancer cells were treated with bexarotene. Proliferation and biomarker expression were assessed. In a proof-of-principle clinical trial, bexarotene tumor tissue levels and intratumoral pharmacodynamic effects were assessed in patients with stages I to II non-small cell lung cancer. Bexarotene (300 mg/m(2)/day) was administered p.o. for 7 to 9 days before resection. RESULTS: Bexarotene-induced dosage-dependent repression of growth, cyclin D1, cyclin D3, total epidermal growth factor receptor (EGFR), and phospho-EGFR expression in BEAS-2B, BEAS-2B-R1, A427, and H358, but not H226 cells. Twelve patients were enrolled, and 10 were evaluable. Bexarotene treatment was well tolerated. There was nonlinear correlation between plasma and tumor bexarotene concentrations (r(2) = 0.77). Biomarker changes in tumors were observed: repression of cyclin D1, total EGFR and proliferation in one case; repression of cyclin D3, total and phospho-EGFR in another. The cases with multiple biomarker changes had high tumor bexarotene (107-159 ng/g). A single biomarker change was detected in one case with low tumor bexarotene. CONCLUSION: Bexarotene represses proliferation and biomarker expression in responsive, but not resistant HBE and lung cancer cells. Similar biomarker changes occur in lung tumors when therapeutic intratumoral bexarotene levels are achieved. This proof-of-principle trial approach is useful to uncover pharmacodynamic mechanisms in vivo and relate these to intratumoral pharmacokinetic effects.     

36. Study on p16INK4a and p15INK4b genes of human bronchial epithelial cells malignantly transformed by cyclophosphamide and thiotepa

Transformed human bronchial epithelial cells BEAS-2B induced by CP and TEPA were used to study abnormity of the tumor suppressor genes p15INK4b and p16INK4a, through which we can provide clues for explanations of the molecular mechanism in carcinogenesis of human bronchial epithelial cells induced by CP and TEPA. Analysis of the genomic DNA from the transformed BEAS-CP, and BEAS-T cells using PCR amplification, singe strand conformation polymorphism(SSCP) and DNA sequencing     

甲醛对人支气管上皮细胞系染色体不稳定性的研究

背景与目的： 为探讨染色体不稳定性与细胞恶性转化之间的关系,揭示化学致癌的机制,本研究以甲醛为诱导剂,研究化学致癌物甲醛作用于人支气管上皮细胞系后,对人支气管上皮细胞染色体稳定性的影响。 材料与方法： 用甲醛作为诱导剂,以液体染毒方式处理细胞,检测染毒后细胞的LC50,以低剂量（20% LC50）对细胞进行诱导并筛选诱导克隆。然后采用细胞遗传学方法（G带染色法）考察染毒后甲醛诱导的人支气管上皮细胞系（BEAS-2B）染色体畸变的情况。 结果： 甲醛作用后,诱导细胞的核型由2倍体转化为近2倍体、非整倍体和多倍体等核型同时存在。诱导细胞染色体稳定性降低,呈现大量染色体畸变,包括染色体丢失、内复制、易位、断裂、双/三着丝粒,同时伴有大量非稳定性畸变。 结论： 甲醛可影响BEAS-2B细胞染色体的稳定性,使其发生畸变并最终使细胞向恶性化方向发展。     

Enhancement of the invasive ability of a transformed human bronchial epithelial cell line by 12-O-tetradecanoyl-phorbol-13-acetate and diacylglycerol

The effect of the tumor promoter 12-O-tetradecanoyl-phorbol-13-acetate (TPA) was studied using an immortalized human bronchial epithelial cell line, BEAS-2B, both in vivo and in vitro. The in vivo model consisted of tracheas reconstituted with an epithelium of BEAS-2B cells xenotransplanted into athymic nude mice. Intraluminal TPA treatment caused increased BEAS-2B cell proliferation and downgrowth into the tracheal stroma. In an in vitro invasion assay, TPA enhanced the invasive capacity of BEAS-2B cells 20- to 25-fold. A similar result was observed with diacylglycerol (DAG), an endogenous activator of protein kinase C, and the effects of TPA and DAG were abolished by simultaneous treatment with H-7, a protein kinase C inhibitor. TPA induced type IV collagenolysis, and this effect also was prevented by H-7. These data are consistent with the hypothesis that TPA causes these cells to become invasive by inducing collagenase activity and that this effect is mediated via protein kinase C.     

Articles activation of promutagens in a human bronchial epithelial cell line stably expressing human cytochrome P450 1A2

Normal human bronchial epithelial (NHBE) cells are the putative progenitor cells of all types of lung cancer. NHBE cells immortalized by SV40 T-antigen retain many characteristics of the primary cells and are a useful model for investigating the role of oncogenes, tumor suppressor genes, and certain chemical carcinogens in the molecular pathogenesis of lung cancer. In this study, SV40 T-antigen-positive cells (BEAS-2B) were characterized for their metabolic functions and were shown to continue to express epoxide hydrolase, glutathione S-transferrase π, glutathione peroxidase, and catalase. To increase their metabolic activity towards human procarcinogens, human cytochrome P450 1A2 (CYP1A2) was stably expressed by introducing CYP1A2 cDNA into BEAS-2B cells either by infection with a high-titer recombinant retrovirus (pXT-1A2) or by transfection with a CYP1A2 expression vector (pCMV1A2), which produced the cell lines B-1A2 and B-CMV1A2, and B-CMV1A2, respectively. Cell lines established with either expression system expressed enzymatically active CYP1A2 protein and were 50- to 400-fold more sensitive to the cytotoxic effect of the carcinogen aflatoxin B₁) (AFB₁) than the corresponding control cell lines. The cytotoxic effects of AFB₁ were paralleled by increased metabolism of AFB₁ and enhanced formation of the AFB₁-N⁷ guanine adduct in B-CMV1A2 cells. Cytotoxicity and adduct formation correlated with a significantly higher protein expression of CYP1A2 by the cytomegalovirus promoter-driven plasmid. Since this human epithelial cell line is the precursor cell type of lung cancer, has normal phase II enzymes, and exhibits highly reproducible expression of phase l enzymes, this in vitro model should aid in the evaluation of putative human carcinogens and anticarcinogens. ©1994 Wiley-Liss, Inc.     

Uncovering residues that regulate cyclin D1 proteasomal degradation

Cyclin D1 regulates G1 cell-cycle progression and is aberrantly expressed in carcinogenesis. Proteasomal degradation of cyclin D1 was highlighted as a cancer chemopreventive mechanism. To understand this mechanism better, residues responsible for degradation and ubiquitination of cyclin D1 were investigated. Eighteen lysines in cyclin D1 had single, double or multiple mutations engineered before transfection into BEAS-2B human bronchial epithelial (HBE) cells to evaluate stabilities after all-trans-retinoic acid (RA) or cycloheximide treatments. Specific mutations stabilized cyclin D1, including substitutions of lysines surrounding the cyclin box domain that inhibited RA-mediated degradation and extended the cyclin D1 half-life. Mutation of all cyclin D1 lysines blocked polyubiquitination. N-terminus (but not C-terminus) modification stabilized cyclin D1. Ubiquitination-resistant mutants preferentially localized cyclin D1 to the nucleus, directly implicating subcellular localization in regulating cyclin D1 degradation. Taken together, these findings uncover specific residues conferring ubiquitination of cyclin D1. These provide a mechanistic basis for proteasomal degradation of cyclin D1.     

Analysis of p16 and p21(Cip1) expression in tumorigenic human bronchial epithelial cells induced by asbestos.

Although asbestos is carcinogenic to humans, the mechanism(s) by which it induces cancer is unknown. Using tumor cell lines generated previously by asbestos treatment of immortalized human bronchial epithelial (BEP2D) cells, we examined alterations in p16 and p21(Cip1) genes together with their protein levels. Results were compared with untreated BEP2D cells, normal human bronchial epithelial cells (NHBE), as well as non-tumorigenic fusion cell lines generated by fusing tumor cells with BEP2D cells. No deletion in the p16 gene was found in any of the tumor cell lines examined. Although p16 protein was expressed at a similar level in tumor and BEP2D cells, there was a fourfold decrease in its expression among NHBE cells. In contrast, both the protein and mRNA expression levels of p21(Cip1) were decreased by about threefold in tumor cell lines when compared with either BEP2D or NHBE cells, which had a similar expression level. Expression of p21(Cip1) mRNA was restored to the control level in all the fusion cell lines examined. The results suggested that down regulation of p21(Cip1) expression is linked to the tumorigenic conversion of BEP2D cells by asbestos.     

Invasive and metastatic potential of a v-Ha-ras-transformed human bronchial epithelial cell line

The in vivo growth behavior and invasive potential of normal and "immortalized" human bronchial epithelial cells were studied by xenotransplantation procedures, an in vitro assay of invasiveness, and determinations of type IV collagenase activity and mRNA expression. BEAS-2B cells, immortalized after hybrid virus infection (adenovirus 12-simian virus 40), reconstituted a columnar epithelium when xenotransplanted into de-epithelialized rat tracheas transplanted sc into athymic BALB/c mice. A few adenomatous growths could be seen 16 weeks after transplantation. BZR cells, obtained by transfer of the v-Ha-ras oncogene into BEAS-2B cells, were tumorigenic in this xenotransplantation model. BZR-T33 cells, obtained from a tumor produced after injection of BZR cells, were also tumorigenic; however, they exhibited a shorter latent period. When these same cell lines were injected sc and iv into athymic BALB/c mice, BEAS-2B cells were not tumorigenic, and the BZR-T33 cells were more tumorigenic than the BZR cells. The incidence of spontaneous metastases after sc inoculation was zero for BEAS-2B cells, 33% for BZR cells, and 100% for BZR-T33 cells. Similar increasing values that correlated well with the data on in vivo growth were noted in the in vitro invasion assay, the collagenolytic ability, and the mRNA expression of type IV collagenase. Normal human bronchial epithelial cells showed the lowest values in all the assays. These progressive changes occurring in cells derived from the same parental line indicate that the presence of the v-Ha-ras oncogene in immortalized bronchial cells is associated with a full-fledged malignant phenotype, which is further enhanced by in vivo passaging.     

Hypoxia and nickel inhibit histone demethylase JMJD1A and repress Spry2 expression in human bronchial epithelial BEAS-2B cells

Epigenetic silencing of tumor suppressor genes commonly occurs in human cancers via increasing DNA methylation and repressive histone modifications at gene promoters. However, little is known about how pathogenic environmental factors contribute to cancer development by affecting epigenetic regulatory mechanisms. Previously, we reported that both hypoxia and nickel (an environmental carcinogen) increased global histone H3 lysine 9 methylation in cells through inhibiting a novel class of iron- and α-ketoglutarate-dependent histone demethylases. Here, we investigated whether inhibition of histone demethylase JMJD1A by hypoxia and nickel could lead to repression/silencing of JMJD1A-targeted gene(s). By using Affymetrix GeneChip and ChIP-on-chip technologies, we identified Spry2 gene, a key regulator of receptor tyrosine kinase/extracellular signal-regulated kinase (ERK) signaling, as one of the JMJD1A-targeted genes in human bronchial epithelial BEAS-2B cells. Both hypoxia and nickel exposure increased the level of H3K9me2 at the Spry2 promoter by inhibiting JMJD1A, which probably led to a decreased expression of Spry2 in BEAS-2B cells. Repression of Spry2 potentiated the nickel-induced ERK phosphorylation, and forced expression of Spry2 in BEAS-2B cells decreased the nickel-induced ERK phosphorylation and significantly suppressed nickel-induced anchorage-independent growth. Taken together, our results suggest that histone demethylases could be targets of environmental carcinogens and their inhibition may lead to altered gene expression and eventually carcinogenesis.