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

Chemoprevention is a strategy used to block the development of cancers in human beings. This emerging field has broad potential for influencing cancer incidence rates in defined high-risk groups and the general population. In this review, we define some of the mechanisms of carcinogenesis, describe some of the genetic markers of carcinogenesis, and list possible biomarkers that may serve as surrogate end points in chemoprevention studies. A major component of this review is a description of the agents that are currently under investigation in animal systems or in human trials. They are grouped according to the agents that block or suppress mutation, such as oltipraz, selenium, vitamin C and the flavones, or according to agents that block promotion and proliferation, such as difluoromethylornithine, tamoxifen, nonsteroidal antiinflammatory drugs, and the vitamin A derivatives. We describe the issues that are considered in the design of chemoprevention trials and in the phase I, II, and III components of these trials. The following national trials are discussed: the Breast Cancer Prevention Trial, which uses tamoxifen; the Prostate Cancer Prevention Trial, which uses finasteride; and a Lung Cancer Prevention Trial, which uses 13-cis-retinoic acid. The review ends with some insights about future studies in chemoprevention.
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PMID:Chemoprevention of cancer. 800 1

Consideration of a range of clinical and basic studies conducted at the National Cancer Institute which explore the nature of the tumor biology of lung identify the limitations of using chemotherapy for the treatment of advanced lung cancer. No single mechanistic explanation for lung cancer's chemoresistance is apparent, although considerable information about the biology of lung cancer and some of its clinical consequences have been elucidated. In contrast to previous works from our group, this presentation will focus principally on studies of the nature of drug resistance with non-small cell cancer. An alternative combined modality strategy for lung cancer control is to focus on epithelial progression of lung cancer using local modalities while it is still confined to the bronchial epithelium. Particular high risk populations may be appropriate to determine if local tools such as photodynamic laser therapy can be effective in this application. To deal with the underlying biochemical perturbations resulting from critical exposure of the bronchial epithelium to carcinogens, rational biochemical intervention with 13 cis retinoic acid are being evaluated in several clinical trials. An evolution towards more effective lung cancer control may involve the combined modalities of laser ablation of accessible dysplastic epithelium and chronic administration of intervention agents, such as retinoids, to neutralize cancer promotion dynamics in the more remote areas of the lung epithelium.
Lung Cancer 1994 Mar
PMID:Integrated clinical and basic studies related to circumventing non-small cell lung cancer drug resistance. 808 30

The addition of lipid hydroperoxides greatly accelerates the rate of oxidative catabolism of all-trans-retinoic acid (RA) in human cell microsomes; hydroperoxy metabolites of the arachidonate cascade are particularly active in the microsomal system. We have measured the plasma content of lipid peroxides in cancer patients during the course of therapy with RA, seeking to assess whether a correlation exists between the rate of oxidative catabolism of exogenously administered RA and whole body lipid peroxide levels. The assay used for plasma lipid peroxides is the capacity to react with thiobarbituric acid under specified conditions; the result is expressed as TBARS (thiobarbituric acid reactive substances). RA administration produced its own accelerated clearance RA within 72 h. Patients were considered to have "normal" or "rapid" baseline catabolism of RA if their Day 1 area under RA concentration over time curve was greater or less than 300 ng.h/ml, respectively. The mean plasma TBARS levels were: 12 normal volunteers = 0.14 microM; 19 "normal" RA catabolizers = 0.25 microM; and 14 "rapid" catabolizers = 0.82 microM. P = 0.008 (rapid catabolizers versus normal volunteers) and 0.05 (rapid catabolizers versus normal catabolizers). Repeat TBARS determinations were made during the course of therapy in 17 patients, all of whom converted to "rapid" RA catabolism on therapy. An increase in plasma TBARS levels > or = 20% of baseline was observed in 5 of 5 prostate cancer patients and 8 of 12 lung cancer patients treated with continuous RA therapy for 2 and 4 weeks, respectively. These observations support the hypothesis that high levels of lipid peroxides and rapid oxidative catabolism of RA are positively correlated.
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PMID:Elevated plasma lipid peroxide content correlates with rapid plasma clearance of all-trans-retinoic acid in patients with advanced cancer. 817 17

Retinoic acid (RA) and nuclear retinoic acid receptors (RARs) have been implicated in a variety of human malignancies including lung cancer, and RA has been proposed as a chemopreventive agent for bronchogenic carcinoma. Normal human tracheobronchial epithelial cells show dramatic induction of RAR-beta mRNA and significant growth inhibition after RA treatment. In contrast, 17 of 22 small cell lung cancer (SCLC) and 9 of 15 non-SCLC lines treated with 1 microM RA showed no significant growth inhibition. Of interest, 5 SCLC lines with high levels of myc gene family expression related to c-, N-, or L-myc gene amplification exhibited growth inhibition (28-87%), whereas 2 non-SCLC lines actually showed growth stimulation after treatment with 1 microM RA. The lines varied greatly in their constitutive expression of RAR-beta mRNA, and 15 of 20 SCLC and 8 of 15 non-SCLC lines failed to show RAR-beta mRNA induction after RA treatment. Six cell lines showed possible alterations in the coding region of RAR-beta by complementary DNA (cDNA)/polymerase chain reaction (PCR) analysis using primers common to the RAR-beta1,2,3 isoforms, since other regions would undergo cDNA/PCR amplification whereas the DNA binding domain would not. Nonetheless, no abnormal band shift patterns in cDNA amplified by PCR were found by single strand conformation polymorphism analysis covering all 1344 base pairs of the RAR-beta open reading frame. Finally, no abnormalities in RAR-alpha gene structure or expression were identified by Southern and Northern blot analysis, including lines with cytogenetic abnormalities of 17q21. We conclude that abnormalities of the RAR-beta system are common in human lung cancer cell lines.
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PMID:Human lung cancer cell lines exhibit resistance to retinoic acid treatment. 827 49

Retinoic acid receptor beta (RAR beta), which codes for a nuclear receptor for retinoic acid, is localized in a chromosomal region frequently deleted in lung cancer cells. The gene is expressed in normal lung tissue and in the majority of the cell lines derived from lung tumors but not in most of the lines derived from lung tumors with epidermoid characteristics. To study the possible role of RAR beta in growth control of epidermoid lung tumor-derived cells, transfectants expresing RAR beta were generated from nonexpressing epidermoid tumor-derived cell lines. Four clones were derived from line CALU-1, three of which showed a 20-60% increase in doubling time in the presence of retinoic acid. Parental and control-transfected cells were unaffected or slightly stimulated. All four clones expressing RAR beta were less tumorigenic in nude mice than were the untransfected or control-transfected cells, with about a 50% incidence of take vs. 95%. When tumors did develop from RAR beta-positive cells, they showed a reduced rate of growth, an increased latency, and, in six of seven tumors tested, a much reduced level of RAR beta expression. Transfectants derived from a second tumor line, H157, also showed a markedly reduced incidence of take in nude mice. Together with the known effects of retinoic acid on differentiation and carcinogenesis, our results support the hypothesis that RAR beta functions as a tumor suppressor gene in epidermoid lung tumorigenesis.
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PMID:Tumor-suppressive effect of the retinoic acid receptor beta in human epidermoid lung cancer cells. 838 40

The lung and upper aerodigestive tract (oral cavity, larynx, pharynx, upper esophagus) will harbor the greatest proportion (approximately 20%) of estimated new cancer cases in 1992. The estimated mortality rate is even higher (32%), which is reflected in a 5-year survival rate of only 7% and 12% for esophageal and lung cancer, respectively. Tobacco use appears to remain the major cause of aerodigestive cancers despite efforts at primary prevention--cessation of exposure. Another strategy to decrease this public health problem is secondary prevention or chemoprevention. Cancer chemoprevention is defined as intervention with chemical agents before invasion to halt or slow the carcinogenic process; potential agents may include minor dietary constituents and pharmaceuticals. The main objective of the Division of Cancer Prevention and Control (DCPC), National Cancer Institute, is to develop promising chemopreventive drugs for use in humans. The testing of cancer chemopreventives for efficacy in the clinic differs from that of cancer treatment drugs. Chemopreventive drug trials involve healthy target populations, and the endpoints are reduced cancer incidence or mortality, or increased latency, with no to minimal toxicity. The lung and upper aerodigestive tract represent a unique opportunity for intervention in this setting. Even with cessation of tobacco exposure, the risk of cancer in the entire epithelium remains high for years due to the "field cancerization" effect. Some of the first chemopreventive trials made use of this system due to the availability of a study population with a tissue at demonstrably high risk for malignant progression. Much of the evidence for chemopreventive efficacy is in the oral cavity because of the well-defined epithelial neoplastic progression, the existence of well-established preclinical models, and relative ease of tissue monitoring and sampling. In one of the first randomized trials, Hong and co-workers demonstrated that 13-cis-retinoic acid prevents the appearance of second primary tumors in patients previously treated for squamous cell carcinomas of the oral cavity and upper respiratory tract. Even using a high risk population, chemoprevention trials involve large sample sizes, lengthy duration and follow-up, and high cost. To circumvent these problems, the use of intermediate biomarkers as surrogate endpoints is being explored. Intermediate biomarkers are defined as biological alterations in tissue (histological, genetic, biochemical, proliferative, differentiation-related) occurring prior to cancer development. In the oral cavity, studies using modulation of a histological intermediate biomarker, dysplastic leukoplakia, as the endpoint have demonstrated response to a retinoid.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Development of chemopreventive agents for lung and upper aerodigestive tract cancers. 841 95

Because they may be used as a quantifiable estimate of the extent of recent DNA injury, micronuclei, extrachromosomal fragments of DNA, are among the most studied potential intermediate markers of cancer chemoprevention. Serial measurements of micronuclei frequency may be easily performed on scrapings from the oral cavity or on bronchial brushings. Assessment of micronuclei frequency and its response to chemopreventive agents has been incorporated into studies of upper aerodigestive tract and lung cancer chemoprevention. These studies have helped define the characteristics of micronuclei and have suggested a role for this test in future chemoprevention studies. Micronuclei frequency has been shown to be increased in the oral and bronchial mucosa of individuals with known carcinogen exposure and is higher at the site of the greatest carcinogen exposure, such as the site where tobacco quids are held, than in grossly normal-appearing mucosa. Treatment with chemopreventive agents leads to a reduction in micronuclei frequency. In oral leukoplakia studies, this effect followed treatment with beta-carotene, retinol, alpha-tocopherol, and 13-cis-retinoic acid. The multistep process of epithelial carcinogenesis results from DNA damage and specific genetic events. That micronuclei reflect ongoing DNA injury suggests the hypothesis that long term suppression of cellular genotoxicity, as reflected by a reduction in micronuclei frequency, ultimately leads to a reduction in cancer incidence.
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PMID:Micronuclei: a potential intermediate marker for chemoprevention of aerodigestive tract cancer. 841 1

Chemoprevention entails using specific agents to suppress carcinogenesis and thereby prevent the development of primary or second primary cancers. Because the concept of chemoprevention in patients with or at risk of lung cancer is new, ongoing clinical trials are based on data from epidemiologic and preclinical research, as well as on results of chemoprevention studies in head and neck cancer. The latter studies have provided a model for such studies in lung cancer, considering the two diseases have a similar etiology and biology of field carcinogenesis. Beta-carotene, natural vitamin A, and the retinoids may be effective chemopreventive agents. However, chronic administration of such agents may be required to prevent the development of cancer. Results of chemoprevention trials in head and neck cancer have demonstrated effective inhibition of the development of second primary tumors with the synthetic retinoid 13-cis-retinoic acid; investigators are hopeful this will be repeated in patients with lung cancer. Results of ongoing phase III trials and continued advances in the epidemiologic and biologic study of lung carcinogenesis should contribute to future research in this area.
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PMID:Chemoprevention strategies in lung carcinogenesis. 841 69

Retinoids, the natural and synthetic vitamin A derivatives, are known to inhibit the proliferation of lung cancer and breast cancer cells and the growth of carcinogen-induced bronchogenic squamous cell carcinoma and mammary tumors, and have been used as chemoprevention agents against both types of cancer. However, clinical trials of retinoids in patients with advanced lung cancer and breast cancer have not been successful. In studying how retinoid sensitivity is lost in cancer cells, we have found that lack of the retinoic acid receptor beta (RAR beta) gene expression and its abnormal regulation by retinoic acid (RA) are common features in human lung cancer and breast cancer cells. The absence and abnormal RA regulation of RAR beta correlates with the loss of anti-proliferation effect of RA in hormone-independent breast cancer cells, and is due to different abnormalities found in cancer cells. Furthermore, expression of RAR beta gene in hormone-independent breast cancer cells restores their RA sensitivity. These data demonstrate that RAR beta can mediate the growth inhibitory effect of RA and suggest that the lack of RAR beta may contribute to retinoid resistance in certain cancer cells.
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PMID:Retinoid receptors in human lung cancer and breast cancer. 865 91

The metabolic activity of cytochrome P-450 enzymes has been associated with an increased risk of developing lung cancer. We found previously that all-trans retinoic acid is catabolized by these oxidative enzymes, and that an inhibitor of this system discriminated between two populations of lung cancer patients. We examined the association between this metabolic phenotype and the risk of lung cancer in 85 subjects. The area under the plasma concentration x time curve (AUC) was calculated after a single oral dose of all-trans retinoic acid (45 mg/m2). The mean AUC for patients who had either squamous or large cell carcinomas was significantly lower than that of patients with adenocarcinomas (P = 0.0001) or control subjects (P = 0.01). Individuals with an AUC < 250 ng x h/ml had a greater likelihood of having squamous or large cell carcinoma (odds ratio = 5.93). This study suggests that the "rapid" catabolism of all-trans retinoic acid is linked to an increased risk of squamous or large cell cancers of the lung.
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PMID:Metabolic phenotypes of retinoic acid and the risk of lung cancer. 866 95


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