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1 University of North Carolina, School of Public Health, Department of Epidemiology, Chapel Hill, North Carolina; Columbia University, 2 Mailman School of Public Health, Department of Epidemiology, 3 College of Physicians and Surgeons, Department of Pathology, and 4 Herbert Irving Cancer Center, New York, New York; 5 Department of Gastroenterology, Tel-Aviv Sourasky Medical Center, Tel-Aviv, Israel; 6 National Cancer Institute, Division of Epidemiology and Genetics, Bethesda, Maryland; 7 Yale University, School of Medicine, Department of Epidemiology and Public Health, New Haven, Connecticut; 8 Fred Hutchinson Cancer Research Center, Program in Epidemiology, and University of Washington, School of Public Health & Community Medicine, Department of Epidemiology, Seattle Washington; 9 Applied Cancer Epidemiology Program, New Jersey Department of Health and Senior Services, Trenton, New Jersey; and 10 New York University, Department of Pathology, New York, New York
| Abstract |
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| Introduction |
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We previously reported (6) a decrease in the odds ratio (OR) for esophageal cancer in relation to the use of aspirin or nonsteroidal anti-inflammatory drugs (NSAIDs), an observation that has been confirmed in a recent meta-analysis (7) . The underlying mechanisms of these potential chemopreventives have not been clearly delineated; however, several are likely including cyclooxygenases 1- (COX1) and 2- (COX2) dependent as well as COX1- and COX2-independent actions. A recent laboratory study (8) reported that, in a mouse model of oral-esophageal cancers that express cyclin D1, administration of sulindac in the drinking water reduced the occurrence of epithelial tumors by 50%.
The molecular epidemiology study reported here was undertaken to explore whether the overexpression of cyclin D1 in tumors of patients with esophageal and gastric cancer was more strongly associated with NSAID use, or other risk factors for these cancers, than among patients with tumors that did not overexpress cyclin D1.
| Materials and Methods |
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Study Population.
Eligible case subjects were men and women between 30 and 79 years of age who were diagnosed with primary invasive cancer of the esophagus or stomach from February 1, 1993 through January 31, 1995 in Connecticut; April 1, 1993 through November 30, 1994 in New Jersey; and from March 1, 1993 through February 28, 1995 in Washington. All case subjects diagnosed with adenocarcinomas of the esophagus or gastric cardia ("target case subjects") were considered eligible for the study. Persons diagnosed with squamous cell carcinoma of the esophagus or adenocarcinomas located elsewhere in the stomach ("comparison case subjects") were sampled by frequency matching to the expected distribution of the target case subjects on geographic area and 5-year age group in Connecticut, New Jersey, and Washington; on sex in New Jersey and Washington; and on race in New Jersey.
Population-based control subjects were frequency matched to the expected distribution of target case subjects by 5-year age group and sex. Control subjects who were 3064 years of age were identified using a modification of Waksbergs random digit dialing method (10) ; those who were 6579 years of age were identified by random sampling of rosters from the Health Care Financing Administration (now called Centers for Medicare and Medicaid Services).
Interviews were obtained for 554 (81%) of the eligible target case subjects, 589 (74%) of the eligible comparison case subjects, and 695 (74%) of the eligible control subjects. The overall response rate among control subjects was 70% when the telephone screener response rate of 91% is taken into account for the 52% of control subjects that were identified by use of random digit dialing. The primary reason for nonparticipation was subject refusal (12% of target case subjects, 17% of comparison case subjects, and 23% of control subjects) followed by physician refusal among case subjects (4% for each group). Interviews were completed with the study subject, rather than to the closest next of kin (usually the spouse), for 70% of the target case subjects, 68% of the comparison case subjects, and 97% of the control subjects.
Risk Factor Information.
During the in-person interview, a structured questionnaire was administered by a trained interviewer, and the average time to complete the questionnaire was 130 min. Information was collected on demographic characteristics, tobacco and alcohol use, other beverage consumption, medical history, use of medications, diet, and occupational history. Definitions of the variables used in these analyses have been described previously in more detail (6
, 7
, 11, 12, 13)
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Retrieval of Archived Tumor Tissue.
For the present study, archived tumor blocks with sufficient tumor for the assays were retrieved for 630 (55.1%) of the 1130 cancer cases. Availability of the usable archived tumor tissue varied little by tumor location and/or histology or stage at diagnosis (data not shown). Cases with sufficient tumor tissue available for the laboratory assays did not systematically differ from those without such tissue with regard to known and suspected risk factors for these tumor types (Table 1)
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The study pathologist (H. Hibshoosh) was responsible for the interpretation of the immunohistochemical results using the same methodology as in studies reported previously (3
, 15)
. Nuclear staining of cyclin D1 was evaluated in the esophageal and gastric carcinomas by a semiquantitative scoring system that considers both staining intensity and percentage of positive nuclei. The system assesses nuclear staining intensity as a 4-level ordered categorical variable (0 = none, 1 = mild, 2 = moderate, 3 = strong); the percentage of positive cells is a dichotomous variable where negative = none or rare cells (where rare is defined as
5% are positive) and positive = more than rare (e.g., generally >5% of the cells were positive). Cases were scored as cyclin D1 positive (cyclin D1+) only if: (a) the staining intensity was either moderate (2)
or strong (3)
and (b) the number of nuclei showing a positive staining exceeded rare cells (generally >5%). This cutoff value for rare cells reflects the level of background staining seen in adjacent normal mucosa. Cases not meeting these criteria were scored as cyclin D1 negative (cyclin D1-).
Statistical Methods.
Each of the four case tumor groups (esophageal adenocarcinoma, gastric cardia adenocarcinoma, esophageal squamous cell carcinoma, noncardia gastric adenocarcinomas) was compared with the controls. For each tumor group, unordered polytomous unconditional logistic regression (16)
was performed to simultaneously calculate the OR (and corresponding 95% confidence intervals [CI]) for cyclin D1+ cases (as compared with the controls) and cyclin D1- cases (as compared with the controls) in relation to potential risk factors for esophageal and gastric cancer. All models included as covariates the frequency-matched factors of geographic center (Connecticut/Washington/New Jersey, entered as indicator variables) and age (in quartiles and entered as indicator variables). Final models included variables for center, age, race, sex, cigarette smoking, use of beer, use of wine, use of hard liquor, body mass index, and use of any NSAID. The ratio of the ORs (comparing the OR for cyclin D1+ cancer to the OR for cyclin D1- cancer), and the corresponding CI was used as an indicator of heterogeneity (17)
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| Results |
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The incidence of both cyclin D1+ tumors and cyclin D1- tumors was associated with cigarette smoking in these data (Table 2)
. There were some differences in the magnitude of the OR according to tumor subtype. For esophageal adenocarcinoma, the OR in relation to ever smoking, as compared with never smoking, was more pronounced for tumors that overexpressed cyclin D1 (OR = 2.63; 95% CI = 1.45, 4.77) than for tumors that did not (OR = 1.81; 95% CI = 1.02, 3.22). However, as reflected in the wide CI, the heterogeneity between the two ORs was not substantial (ratio of the ORs for cyclin D1+/cyclin D1- tumors = 1.45; 95% CI = 0.66, 3.18). For esophageal squamous cell carcinoma, there was little or no difference between the OR for cyclin D1+ tumors and cyclin D1- tumors. For gastric cardia adenocarcinoma, however, the magnitude of the OR in relation to ever smoking was less pronounced among those with cyclin D1+ tumors than among those with cyclin D1- tumors. For other gastric adenocarcinomas, this difference was more pronounced, with a slight reduction in the OR for cyclin D1+ tumors (0.90; 95% CI = 0.51, 1.61) and a more than doubling of effect for cyclin D1- tumors (2.37, 95% CI = 1.50, 3.74); this heterogeneity was significant (ratio of the ORs for cyclin D1+ tumors/cyclin D1- tumors = 0.38; 95% CI = 0.19, 0.75).
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| Discussion |
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This epidemiological report is also the first to examine whether the risk for these cancers in humans varies with cyclin D1 expression in relation to NSAID use, cigarette smoking, and other factors. A study in laboratory animals (18) found that subcutaneous administration of N-nitrosomethylbenyzlamine, which is a constituent of tobacco smoke, increased the severity of esophageal squamous dysplasia and cellular proliferation in transgenic mice that overexpress cyclin D1. Our results are not consistent with this laboratory finding. We observed no substantial difference in the ORs associated with cigarette smoking among those with cyclin D1+ tumors versus those with cyclin D1- tumors. Regardless of cyclin D1 status, cigarette smoking was associated with an elevated risk of esophageal adenocarcinoma, gastric cardia adenocarcinoma, and esophageal squamous cell carcinoma. For other gastric adenocarcinomas, only tumors that did not overexpress cyclin D1 had an elevated OR, especially among current smokers. Similarly, little heterogeneity of effect was noted for several other factors in relation to esophageal and gastric cancer, including obesity, alcohol intake, or antacid use.
In the data reported here, the decrease in adenocarcinomas of the esophagus and gastric cardia associated with aspirin or NSAID use was observed only for subjects whose tumors overexpressed cyclin D1, and no effect was observed among tumors that did not overexpress cyclin D1. The precise mechanism by which NSAIDs reduce cancer risk has not been fully elucidated (8 , 19) . Aspirin has been shown in vivo to inhibit COX1 and COX2, thereby blocking the production of prostaglandins but has little effect on these activities in vitro; also, the biochemical effects of salicylate appear to be independent of effects on COX activity (20) . Thus other mechanisms of action are under consideration. For example, sulindac, sulindac sulfide, and other NSAIDs have been shown to inhibit proliferation and induce apoptosis in colon cancer cells, consequences that have been attributed to their effect on the cell cycle (21) . Among the important cell cycle-regulators are the cyclins and the cyclin-dependent kinases (1) . In laboratory studies, cyclin D1 expression was reduced by aspirin and by indomethacin in four colorectal cell lines (22) , decreased by sulindac sulfide in colon cancer cells (23) and in breast cancer cell lines (24) , and inhibited by sodium salicylate in pancreatic cell lines (25) .
Our observations, if corroborated in other studies, may help to identify patients that may particularly benefit from intervention with NSAIDs. It is noteworthy that the risk of esophageal adenocarcinoma is much greater among patients with Barretts esophagus that show evidence of cyclin D1 overexpression than those without cyclin D1 overexpression (5) . Thus, it is plausible that the chemopreventive effects of NSAIDs may be more favorable when lesions of Barretts esophagus overexpress cyclin D1. Other observations among patients with Barretts esophagus are consistent with this idea; in a cross-sectional study, Vaughan et al. (26) noted that, among Barretts patients, NSAID use was not associated with loss of heterozygosity of 9p allele (which would knock out p16), but was strongly associated with aneuploidy, increased 4N (tetraploidy) fraction, 17p loss of heterozygosity, and high-grade dysplasia. Given the complex interplay between p16, cyclins, and cyclin-dependent kinases, these observations are consistent with the likely implications of our findings that NSAID use may reduce the progression of Barretts esophagus to esophageal adenocarcinoma and may be most effective among Barretts patients with lesions that overexpress cyclin D1+.
Our findings, however, must be cautiously interpreted. Even in the most carefully conducted epidemiological study, bias can arise at several steps, including the inclusion of subjects who choose to participate, the difficulty in recalling historical behaviors or events, as well as the proportion of patients for whom archived block tissue was available and usable. The molecular epidemiology study reported here was built on a parent study that was population-based with a reasonable response rate (9)
, which reduces the likelihood of bias arising because of sample selection. In Table 1
, we were able to demonstrate that the proportion of patients for whom we had archived tissue that was usable for these analyses was not systematically different from the entire sample of case participants. It is possible that cases and controls may have differentially recalled their use of medications, such as aspirin or other NSAIDs. Heterogeneity with cyclin D1 status, however, was not evident for the reported use of over-the-counter antacids, suggesting that the heterogeneity noted for NSAID use was not a spurious result. Furthermore, for recall to influence the results reported here, case response to the comprehensive questionnaire would have had to have been reported differentially based on their cyclin D1 status, which is very unlikely (27)
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In summary, the results of our population-based study confirm the high prevalence of cyclin D1 overexpression in various histological subgroups of esophageal and gastric tumors. In determining whether risk factors for these cancers varied by the presence or absence of cyclin D1 overexpression, we found little variation for alcohol intake, body size, or cigarette smoking, except that the risk of noncardia gastric adenocarcinomas was not elevated for tumors that were cyclin D1+. In contrast, the reduced risk for esophageal and gastric cardia adenocarcinomas associated with the use of aspirin or other NSAIDs was restricted to patients with tumors that overexpressed cyclin D1. Because cyclin D1 is overexpressed in lesions of Barretts esophagus that progress to esophageal adenocarcinoma (4 , 5) , our data, if replicated, suggest that targeting these patients for intervention with NSAIDs may be particularly fruitful.
| Footnotes |
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The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked advertisement in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
Requests for reprints: Marilie D. Gammon, University of North Carolina, School of Public Health, Department of Epidemiology, CB 7435 McGavran-Greenberg Hall, Chapel Hill, NC 27599-7435. Phone: (919) 966-7421; Fax: (919) 966-2089; E-mail: gammon{at}unc.edu
Received 7/ 3/03; revised 9/ 5/03; accepted 9/10/03.
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