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Query: UMLS:C0242379 (lung cancer)
 71,905 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The statistics on lung cancer survival remain disappointing and form a powerful argument to develop new methods to control this most deadly form of cancer in both men and women. Chemoprevention is one of these new approaches. While carcinogens from cigarette smoke form an essential link between nicotine addiction and lung cancer, several investigations confirm that dietary and genetically determined factors play an important role in modulating the individual susceptibility and are linked to the chemoprevention approach. In spite of a large abundance of positive preclinical observations, most experiences with potential chemopreventive agents, such as retinoids and antioxidants in individuals at risk for lung cancer have been so far negative. Moreover, beta-carotene was associated with an increased lung cancer incidence in two large randomized studies, as a consequence of a negative interaction with smoking. On the other hand, recent progress in molecular biology has led to the discovery of specific approaches to chemoprevention and there considerable optimism regarding the potential of molecules and antibodies that target specific receptors or mutations. Epidermal growth factor receptor blocking agents, farnesyltransferase and cyclooxygenase inhibitors and 9-cis retinoic acid have been identified as promising candidates for studies in high risk populations. After more than 20 years of worldwide research, the prospects for effective lung cancer treatment are better than ever.
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PMID:Chemoprevention of lung cancer: soon daily practice? 1259 53

Differentially expressed nucleolar TGF-beta1 target (DENTT) is a recently identified gene whose mRNA is differentially affected by TGF-beta1 in TGF-beta1-responsive human lung cancer cells and who is a new member of the TSPY/TSPY-like/SET/NAP-1 (TTSN) protein superfamily. Here, we report that mouse DENTT mRNA contains a 2031-bp open reading frame that encodes a predicted polypeptide of 677-amino acids with a relative molecular mass of 77,671 Da. The mouse and human DENTT sequences show 77% and 78% homology at the nucleotide and amino acid level, respectively. Mouse DENTT is predicted to be a nuclear protein with two nuclear localization signals (NLS), two coiled-coil regions, and a domain that shows significant identity to a region that defines the TTSN superfamily. Green fluorescent protein (GFP)-tagged full-length mouse DENTT transfected into COS-7 cells showed localization predominantly in the nucleolus. Reverse transcription-polymerase chain reaction amplification, Northern hybridization, and Western blot analyses showed expression of mouse DENTT mRNA and protein throughout mouse embryogenesis. Immunohistochemical staining analysis showed that DENTT is expressed in multiple tissues in a defined spatiotemporal pattern during mouse embryogenesis. The heart and primitive brain were the first organs of the embryo that showed immunoreactivity for the DENTT antibody by day 8 of development (E8). In the developing mouse brain, the choroid plexus was intensely stained for DENTT in all stages of development. The spinal cord and dorsal root ganglia were also positive for DENTT staining beginning in the 11-day-old embryo (E11), where homogeneous immunostaining was observed throughout the developing neurons. By day 16 of development (E16), only a small subset of the neuronal population in the spinal cord and dorsal root ganglia was positively stained for DENTT. DENTT immunoreactivity increased steadily with maturation as the differentiation of cartilage and osteoblasts proceeded and reached a maximum in the growth plate during endochondral ossification. DENTT expression was also detected in multiple rodent cell types in vitro, including mouse F9 embryonal carcinoma (EC) cells. Addition of retinoic acid or sodium butyrate to F9 EC cells showed a rapid decrease in expression of DENTT protein occurring by 1 hr that continued to decrease to almost undetectable levels after 24 hr. Cotransfection of full-length mouse DENTT expression plasmid with 3TPLux or COL7A1Luc Luciferase reporter plasmids into F9 EC cells significantly increased the level of 3TPLux reporter transcription while decreasing the level of COL7A1Luc reporter transcription, suggesting that DENTT may play multiple roles in modulating transcriptional responses. These findings suggest new roles for the TTSN superfamily during embryogenesis and differentiation.
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PMID:Differentially expressed nucleolar TGF-beta1 target (DENTT) in mouse development. 1261 35

The chemotherapeutic agent retinoic acid (RA) and its derivatives have been used to treat many tumor types. The antitumor effects of retinoids are in part due to their ability to inhibit proliferation of cancer cells. However, smokers receiving dietary vitamin A and beta carotene in chemoprevention studies had a higher incidence of lung cancer. These studies imply that lower doses of retinoids may have tumor-promoting activity. The effects of RA are mediated by a family of ligand-dependent transcription factors, the retinoic acid receptors (RARs) and the retinoid X receptors (RXR). We examined the effects of low- and high-dose RA treatment on proliferation of human squamous cell carcinoma lines in vitro. Low concentrations of RA (20 nM) increased proliferation of SCC lines by epidermal growth factor (EGF) activation of the mitogen-activated protein kinase ERK1. These changes were accompanied by increased expression of S- and G(2) phase cyclins and cyclin-dependent kinases (cdk), increased Rb phosphorylation, and increased E2F-1 DNA binding activity. In contrast, higher doses of RA (40 nM to 1 micro M) inhibited ERK1 expression, caused accumulation of G(1) phase cyclins and cdks, decreased Rb phosphorylation, and increased Rb/E2F-1 association. Overexpression of ERK1 or dominant negative ERK1 was sufficient to reproduce the effects of low- and high-dose RA, respectively. Treatment with receptor selective retinoids revealed that both RARalpha and RARgamma mediated the effects of RA on SCC lines. We concluded that low-dose RA induced proliferation by increased EGF signaling while higher concentrations inhibited cell division by decreasing ERK1 activation.
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PMID:Retinoic acid differentially regulates cancer cell proliferation via dose-dependent modulation of the mitogen-activated protein kinase pathway. 1275

RA175, a new immunoglobulin superfamily member, is preferentially expressed during differentiation of P19 embryonic carcinoma (EC) cells induced by retinoic acid. In the present study, we isolated mouse RA175 cDNA in its entirety and showed that RA175 is the mouse ortholog of TSLC1, a tumor suppressor gene in human lung cancer. RA175/TSLC1 was localized in the adherent region of human lung squamous carcinoma cells and in the differentiated P19 EC cells. RA175/TSLC1 showed homophilic trans-interaction activity in a Ca(2+)-independent manner. RA175/TSLC1 was preferentially expressed in the polarized cells lining the lumen of developing mouse lung epithelium. This suggests that RA175/TSLC1 is a cell adhesion molecule that is acting as a tumor suppressor gene in the metastasis of lung tumors. RA175/TSLC1 may be necessary for cells to remain tightly associated in the epithelium, thereby suppressing metastasis.
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PMID:RA175, which is the mouse ortholog of TSLC1, a tumor suppressor gene in human lung cancer, is a cell adhesion molecule. 1279 82

The peroxisome proliferator-activated receptor gamma (PPAR gamma) is a nuclear receptor family member that can form a heterodimeric complex with retinoid X receptor (RXR) and initiate transcription of target genes. In this study, we have examined the effects of the PPAR gamma ligand ciglitazone and the RXR ligand SR11237 on growth and induction of retinoic acid receptor (RAR) beta expression in breast and lung cancer cells. Our results demonstrated that ciglitazone and SR11237 cooperatively inhibited the growth of ZR-75-1 and T-47D breast cancer and Calu-6 lung cancer cells. Gel shift analysis indicated that PPAR gamma, in the presence of RXR, formed a strong complex with a retinoic acid response element (beta retinoic acid response element) in the RAR beta promoter. In reporter gene assays, RXR ligands and ciglitazone, but not the PPAR gamma ligand 15d-PGJ(2), cooperatively promoted the transcriptional activity of the beta retinoic acid response element. Ciglitazone, but not 15d-PGJ(2), strongly induced RAR beta expression in human breast and lung cancer cell lines when used together with SR11237. The induction of RAR beta expression by the ciglitazone and SR11237 combination was diminished by a PPAR gamma-selective antagonist, bisphenol A diglycidyl ether. All-trans-retinoic acid or the combination of ciglitazone and SR11237 was able to induce RAR beta in all-trans-retinoic acid-resistant MDA-MB-231 breast cancer cells only when the orphan receptor chick ovalbumin upstream promoter transcription factor was expressed, or in the presence of the histone deacetylase inhibitor trichostatin A. These studies indicate the existence of a novel RAR beta-mediated signaling pathway of PPAR gamma action, which may provide a molecular basis for developing novel therapies involving RXR and PPAR gamma ligands in potentiating antitumor responses.
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PMID:Regulation of retinoic acid receptor beta expression by peroxisome proliferator-activated receptor gamma ligands in cancer cells. 1283 38

Epidemiological studies suggested that vitamin A may be protective against lung cancer, however, recent chemoprevention trials with beta-carotene, a precursor of vitamin A, demonstrated enhancement of lung carcinogenesis among smokers. Whether vitamin A is beneficial or harmful in chemoprevention of lung cancer in smokers has not been resolved. This study was designed to determine the effect of retinol alone in current and former smokers using bronchial dysplasia, nuclear morphometry and retinoic acid receptor-beta (RAR-beta) mRNA expression as surrogate end-point biomarkers (SEBs). Eighty-one current or former smokers with a smoking history of >/=30 pack-years were randomized to receive either placebo or retinol (50,000 IU per day) for six months. Fluorescence bronchoscopy was performed prior to treatment to localize areas suggestive of dysplasia. At least 4 bronchial biopsies were taken per subject including at least two biopsies from apparently normal areas. The same areas were precisely re-biopsied after 6 months. Any new areas suggestive of dysplasia were also biopsied. Changes in the SEBs were assessed before and after treatment. At baseline, the frequency of biopsies negative for RAR-beta expression was: normal (23%), hyperplasia (28%), metaplasia (41%), mild dysplasia (41%), and moderate/severe dysplasia (44%). There was no significant difference in the regression rate between the retinol and placebo groups using histopathology and nuclear morphometry as SEBs. The likelihood of regression was found to be lower in those who continued to smoke during the study (OR=1.86 for those smoking >10 cigarettes per day, p=0.084 to OR=0.95, p=0.26 for those smoking 20+ per day compared to ex-smokers). Retinol was not effective in the up-regulation of RAR-beta in lesions with bronchial dysplasia. We postulate that the lack of effect of retinol on RAR-beta expression among individuals who continued to smoke while taking retinol may be due to suppressive effect of tobacco smoke constituents on RAR-beta expression and/or altered cellular metabolism of retinol to retinoic acid and its isomers.
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PMID:Surrogate end-point biomarker analysis in a retinol chemoprevention trial in current and former smokers with bronchial dysplasia. 1461 33

The retinoic acid receptor beta (RAR-beta) gene encodes one of the primary receptors for retinoic acid, an important signaling molecule in lung growth, differentiation and carcinogenesis. RAR-beta has been shown to be down-regulated by methylation in human lung cancer. We have used previously lung tumors induced in mice to evaluate the timing and effect of specific carcinogen exposures on targeting genes altered in human lung cancer. These studies were extended to characterize the role of methylation of the RAR-beta gene in murine lung cancers. After treatment with the demethylating agent 5-aza-2'-deoxycytidine (DAC), RAR-beta was re-expressed in silenced cell lines or expressed at a higher rate than without DAC, supporting methylation as the inactivating mechanism. Bisulfite sequencing detected dense methylation in the area of the CpG island that contained the 5' untranslated region and the first translated exon in non-expressing cell lines, compared with minimal and heterogeneous methylation in normal mouse lung. Methylation-specific PCR revealed that this gene is targeted differentially by carcinogen exposures with the detection of methylated alleles in virtually all primary tumors associated with cigarette smoke or 4-methylnitrosamino-1-(3-pyridyl)-butanone (NNK) in contrast to half of tumors induced by methylene chloride or vinyl carbamate. RAR-beta methylation was also detected in 54% of preneoplastic hyperplasias induced by treatment with NNK. Bisulfite sequencing of both premalignant and malignant lesions detected dense methylation in the same area observed in cell lines, substantiating that this gene is functionally inactivated at the earliest histologic stage of adenocarcinoma development. These studies demonstrate that aberrant methylation of RAR-beta is an early and common alteration in murine lung tumors induced by several environmentally relevant exposures.
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PMID:Carcinogen exposure differentially modulates RAR-beta promoter hypermethylation, an early and frequent event in mouse lung carcinogenesis. 1465 41

Beta-carotene and other carotenoids have been thought to have anti-cancer activity, either because of antioxidant activity or because of their ability to be converted to vitamin A. Nevertheless, two large scale intervention studies in humans using high doses of beta-carotene found that beta-carotene supplementation resulted in more lung cancer rather than less lung cancer among smoking and asbestos exposed populations. Studies conducted in the ferret have elucidated molecular mechanisms behind this observation, in that high-dose beta-carotene and smoke exposure in these animals leads to squamous metaplasia, a pre-cancerous lesion in the lung. High dose beta-carotene in the smoke exposed animals was found to give rise to a number of transient oxidative metabolites, which include P450 enzymes that result in the destruction of retinoic acid, and diminished retinoid signaling, and enhanced cell proliferation. In addition, eccentric cleavage beta-carotene metabolites facilitate the binding of smoke derived carcinogens to DNA. In other ferret studies low dose beta-carotene smoke exposure provided mild protection against squamous metaplasia. Thus, it appears that the explanation of the apparent paradoxical effects of beta-carotene on lung cancer is related to dose. The metabolism and breakdown of natural products should be thoroughly investigated in animal models before embarking on large scale intervention trials, particularly when using unusually high doses that greatly exceed normal dietary levels.
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PMID:The enigma of beta-carotene in carcinogenesis: what can be learned from animal studies. 1470 31

Retinoic acid (RA) and sodium butyrate (NaB) have been implicated in the regulation of growth and differentiation in various cancer cells. To produce an agent with the properties of both RA and NaB, a butyryl aminophenyl ester of RA (4-BPRE) was synthesized. The agent was compared with an aminophenyl ester devoid of the butyryl group (4-APRE) for antitumor potential in vitro. Like RA, 4-hydroxyphenyl retinamide (4-HPR) and 4-APRE, 4-BPRE was an active ligand for all three subtypes of RAR, but not for RXR, as determined by transcription assays in COS-1 cells. In addition, regardless of the butyryl group, 4-BPRE actively suppressed c-Jun transcriptional activity, which may result in reduced expression of matrix metalloproteinases (MMP-1 and MMP-2), and effectively inhibited HCT116 cell invasion into Matrigel. In these respects, 4-BPRE is similar to 4-APRE, and even to RA and 4-HPR. However, our results showed that in HCT116 colon and A549 lung cancer cells, 4-BPRE was much more cytotoxic than RA and 4-APRE, and was also more cytotoxic than 4-HPR, which is the most cytotoxic retinoid derivative under clinical investigation. Subsequent assays using DAPI staining, DNA fragmentation, and FACS analysis suggested that the cytotoxic effect of 4-BPRE is mediated by apoptosis in HCT116 cells. Moreover, 4-BPRE inhibited histone deacetylase (HDAC) activity to some degree, although inhibition was less than that induced by the known HDAC inhibitors TSA and NaB. These results suggest that 4-BPRE could be a promising antitumor retinoid with both NaB activity and RA function.
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PMID:In vitro antitumor potential of 4-BPRE, a butyryl aminophenyl ester of retinoic acid: role of the butyryl group. 1476 28

Large, randomized trials have been conducted in the primary prevention of lung cancer using micronutrients or derivative agents for which epidemiological data suggested a potential role in lung cancer prevention. The disappointing primary prevention trials of beta-carotene, alpha-tocopherol, and retinyl palmitate have led to the development of a more compact, biomarker-driven series of translational trials of lung cancer prevention that target reversal of premalignancy as the primary end point. Serial trials of 13-cis-retinoic acid (isotretinoin) and other retinoids have failed to show a difference in reversal of premalignancy in active smokers or in second primary tumor prevention. However, a trial of 9-cis-retinoic acid, a pan retinoid/rexinoid agonist, showed up-regulation of retinoic acid receptor beta (RAR-beta), a potentially important intermediate marker of response in lung cancer premalignancy. Other planned or ongoing trials currently target important molecular markers of lung carcinogenesis and progression including cyclooxygenase-2, the ras-signaling pathway through farnesyl transferase inhibitors, and the tyrosine kinase/epidermal growth factor receptor pathway (gefitinib, erlotinib). Early results of bioadjuvant trials in head and neck cancer suggest that combination chemoprevention will ultimately be an important option.
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PMID:Molecularly targeted approaches to the chemoprevention of lung cancer. 1521 68


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