| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
Advances in Brief |
Departments of Thoracic/Head and Neck Medical Oncology [J. M. K., J. S. L., F. R. K., L. M., R. C. M., A. B., D. L., R. L., W. K. H.], Thoracic and Cardiovascular Surgery [G. L. W.], Cancer Prevention [S. M. L., X. X.], Pathology [J. Y. R., B. L. K.], and Biostatistics [J. J. L.], and Division of Pathology and Laboratory Medicine [H. A. F.], University of Texas M. D. Anderson Cancer Center, Houston, Texas 77030
 |
ABSTRACT |
|---|
 Top ABSTRACT INTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
|---|
|
INTRODUCTION |
|---|
|
TopABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
|---|
Efforts to identify retinoids that are more effective in lung cancer chemoprevention have been hampered by the lack of an appropriate "intermediate end point" to demonstrate a reduction in lung cancer risk. Lung carcinogenesis is a multistep process that involves the progression of a normal bronchial epithelial cell through a sequence of histopathological entities, culminating in a fully transformed, invasive cancer. Whereas the sequence of events has not been completely defined, the classical progression includes normal, hyperplasia, squamous metaplasia, dysplasia, carcinoma in situ, and invasive cancer. We previously used this model in the design of a randomized, placebo-controlled chemoprevention trial, testing the efficacy of 13cRA3 in the reversal of squamous metaplasia and dysplasia (5) . Current smokers underwent bronchoscopic examination with biopsies, and individuals with detectable squamous metaplasia and/or dysplasia were randomized to 6 months of treatment with 13cRA or placebo and evaluated for response by repeat bronchoscopy with biopsies. We found that 13cRA did not reduce the incidence or severity of squamous metaplasia or dysplasia in active smokers (5) . Whereas there was no effect on bronchial histopathology, we found evidence that 13cRA activated retinoid signaling pathways in the bronchial epithelium (6) . Retinoid signaling is activated by binding of retinoids to retinoid nuclear receptors, which are a family of transcription factors that bind to specific DNA sequences termed RAREs (7) . The RAR-ß gene contains a RARE in its gene promoter region that functions as a positive regulatory element. Presumably, 13cRA increased the expression of the RAR-ß gene in the bronchial epithelium through this mechanism (6) .
The inactivity of 13cRA in the reversal of squamous metaplasia and dysplasia in active smokers raises the possibility that premalignant bronchial foci are resistant to retinoid treatment. A growing body of laboratory studies supports the theory that, during the process of malignant transformation, human bronchial epithelial cells become resistant to the growth inhibitory effects of retinoids (8 , 9) . Contributing to the development of retinoid refractoriness, retinoid nuclear receptors are dysfunctional in a proportion of non-small cell lung carcinomas, exhibiting reduced transcriptional activation in response to retinoid binding (10) . Because this retinoid signaling abnormality could limit the lung cancer chemopreventive effects of conventional retinoids, alternative approaches should be considered. Toward this aim, a variety of synthetic retinoids have been developed that function through novel mechanisms (11) . One of these retinoids is 4-HPR, which has demonstrated chemopreventive activity in animal models of mammary, prostate, lung, and bladder cancer (11) . In clinical trials, 4-HPR demonstrated activity in the reversal of premalignant oral leukoplakia and preventive effects against ovarian cancer and, among premenopausal breast cancer patients, contralateral breast cancer (12) . In tissue culture, 4-HPR induces apoptosis in a variety of lung cancer cell lines through both retinoid receptor-dependent and -independent mechanisms (13, 14, 15) .
In this study, we tested the hypothesis that squamous metaplasia and dysplasia revert to normal bronchial epithelium in 4-HPR-treated participants through stimulation of retinoid nuclear receptor-dependent signaling pathways, as shown by an increase in RAR-ß gene expression. We examined the activity of 4-HPR in the chemoprevention of bronchial dysplasia and squamous metaplasia in current and former smokers. Following screening by bronchoscopic examination with biopsies, individuals with detectable squamous metaplasia and/or dysplasia were randomized to 6 months of treatment with 4-HPR or placebo. Response to treatment was determined by repeat bronchoscopy with biopsies. We found that 4-HPR had no detectable effect on squamous metaplasia or dysplasia under these conditions. Potential explanations for its inactivity are discussed.
|
MATERIALS AND METHODS |
|---|
|
TopABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
|---|
All eligible participants underwent a screening bronchoscopy with biopsies at six predetermined sites in the bronchial tree, including the main carina, the bifurcation of the right upper lobe and mainstem bronchus, the bifurcation of the right middle lobe and right lower lobe, the bifurcation of the left upper lobe and the lingula, the medial bronchus of the right lower lobe, and the anterior bronchus of the left lower lobe. The biopsies were routinely processed and stained with H&E, and 10 sections were evaluated per site for the presence of dysplasia and squamous metaplasia by referee pathologists (J. Y. R. and B. L. K.) blinded to the timing of the specimens and the treatment group. MI was calculated as described previously (5) by dividing the number of biopsy sections exhibiting squamous metaplasia by the total number of sections examined, and multiplying the result by 100. Participants found to have evidence of dysplasia or a MI value of >15% were randomly assigned to receive 4-HPR (200 mg p.o. per day) or placebo for 6 months, with a monthly 3-day drug holiday to prevent 4-HPR-related ocular toxicity. Participants were seen at monthly intervals and evaluated for compliance, drug-related toxicity, and serum drug levels. Toxicity was graded, as described previously, using National Cancer Institute Common Toxicity Criteria (5) . At the end of 6 months, bronchoscopic examination was repeated with biopsies at the same sites to evaluate the bronchial tree for evidence of change.
Analysis of Serum Retinol and Drug Levels.
Levels of 4-HPR and its major metabolite 4-MPR were measured in serum
samples obtained at baseline, 2, and 6 months of treatment that had
been frozen at -70°C and protected from exposure to light by
performing high-performance liquid chromatography using
4-ethoxyphenylretinamide as an internal standard (16)
. The
chromatographic separation was performed on a Vydac 201TP column
(0.46 x 25 cm). The isocratic mobile phase was 55% acetonitrile,
10% n-butyl alcohol, 35% water, and 0.01 mol/liter ammonium acetate.
The detector was programmed at 364 nm for the first 12 min, 325 nm for
the next 3 min, and 364 nm for the last 8 min to correspond to the
elution times of 4-HPR, 4-MPR, and 4-ethoxyphenylretinamide. Serum
retinol levels were measured in serum samples taken from patients
at the same time points by high-performance liquid chromatography
analysis performed at Smith Kline Beecham Laboratories, as described
previously (17)
.
In Situ mRNA Hybridization Studies.
Nonradioactive in situ hybridization of RAR-ß mRNA was
performed on formalin-fixed, paraffin-embedded sections as described
previously (18)
. The binding specificity of the antisense
riboprobes was verified using sense probes as controls. Staining was
scored as either detectable or undetectable. RNA quality was verified
by in situ hybridization of retinoid X receptor-
mRNA,
which is expressed constitutively in bronchial epithelium
(6)
.
Microsatellite Analysis.
For microdissection, four 4-µm thick tissue sections were mounted on
glass slides and stained with H&E. The epithelial part of each biopsy
was microdissected under stereomicroscope. The stroma cells were also
microdissected to be used as a normal control for each individual.
After microdissection, the samples were digested and DNA was extracted
as described previously (19)
. DNA from at least 150 nuclei
was used for each PCR amplification. The markers used were D3s1285
(3p14), D9s171 (9p21), and TP53 (17p13) (Research Genetics, Huntsville,
AL). For PCR amplification, one of the primers for each marker was
end-labeled with [
-32P]ATP (4500 Ci/mmol;
ICN Biomedicals, Costa Mesa, CA) and T4 DNA polynucleotide kinase (New
England Biolabs, Beverly, MA). PCR reactions were carried out in a
12.50-µl volume containing 3% DMSO, 200 µM dNTP, 1.5
mM MgCl2, 0.4 µM PCR primers including 0.1
µM [-32P]-labeled primer, and
0.5 unit of Taq DNA polymerase (Life Technologies, Inc., Gaithersburg,
MD). DNA was amplified for 40 cycles at 95°C for 30 s, at
56–60°C for 60 s, and at 70°C for 60 s in a temperature
cycler (Hybaid; Omnigene, Woodbridge, NJ) in 500-µl plastic tubes,
followed by a 5-min extension at 70°C. The PCR products were
separated on a 6% polyacrylamide-urea-formamide gel and then exposed
to film. LOH was defined as >50% reduction of the intensity by visual
inspection in one of the two alleles as compared with those in normal
control panels. When a participant was used as the analysis unit, any
biopsy from an individual with LOH was considered to exhibit LOH even
if other samples did not display a LOH pattern.
Statistical Considerations.
Descriptive statistics and frequency tabulation were used to summarize
the patient characteristics and toxicity profile. The Wilcoxon’s
rank-sum test (20)
was used to compare the mean MI change
before and after treatment between the 4-HPR and placebo groups. The
Wilcoxon signed-rank test was applied to test the change of serum
retinol level after treatment. Frequency tabulation was given for the
baseline and 6-month RAR-ß and LOH status using both biopsy site and
participant as the analysis unit. The McNemar test was performed to
determine the change of RAR-ß expression and LOH before and after
treatment (20)
. The GEE with binary outcome and logistic
link was applied to the data to compare change in the
metaplasia/dysplasia status, RAR-ß expression, and LOH status over
time between the treatment groups (21)
. All of the
Ps were based on two-sided tests.
|
RESULTS |
|---|
|
TopABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
|---|
. Seventy participants were evaluable for response, having completed at
least 3 months of treatment, followed by a second bronchoscopic
examination with biopsies. The most frequent causes of early treatment
withdrawl were non-drug related (i.e., conflicts with work
schedule, moving away). Of the 70 evaluable participants, 62 had
detectable squamous metaplasia but no dysplasia, 1 had dysplasia but no
squamous metaplasia, and 7 had both squamous metaplasia and dysplasia,
at baseline.
|
. No evidence of ocular toxicities (i.e., night blindness)
was observed in participants who took 4-HPR in this trial.
|
or biopsy site (Table 4)
. Table 3
shows that the mean MI was reduced over time by 7.1% and
4.9% in the 4-HPR and placebo groups, respectively. The difference in
MI reduction between the 4-HPR and placebo groups was not statistically
significant (P = 0.79 by two-sided Wilcoxon’s rank-sum
test). When bronchial biopsy was used as the unit of analysis, 43.6%
of the biopsies had metaplasia at baseline whereas only 35.6% of the
biopsies had metaplasia after 6 months of treatment with 4-HPR (Table 4)
. The reduction in metaplasia was only marginally significant
(P = 0.08 by McNemar test). On the other hand, there
was no indication of reduction in metaplasia in the placebo group.
However, the change of metaplasia status was not significantly
different between the 4-HPR and placebo groups (P =
0.57 by GEE method).
|
|
. No
change of dysplasia status from baseline to 6 months was found in
either the 4-HPR or placebo group. The difference between the two
treatment groups was not statistically different (P =
0.83 by GEE method). Smoking status (current versus quitter)
was examined as a covariate and was found not to affect squamous
metaplasia outcome (Fig. 1)
.
|
.
|
. Among informative cases, LOH was detected at chromosomes 3p, 9p, and
17p in 26.7%, 24.7%, and 10.8%, respectively, of the biopsy sites
and 60.4%, 55.6%, and 29.6%, respectively, of the participants. LOH
was present on at least one chromosomal locus in 36.2% of the biopsy
sites and 70.8% of the participants. Changes in the frequency of LOH
attributable to treatment effect were measured (Table 7)
. The frequency of LOH at chromosomes 9p and 17p did not change with
time in the 4-HPR- or placebo-treated groups (data not shown). Whereas
the incidence of LOH at chromosome 3p decreased in the 4-HPR group
(P = 0.06 by McNemar test), this change was not
statistically significant when compared with changes observed in the
placebo group (P = 0.32 by GEE method).
|
|
. The mean nadir retinol level in the 4-HPR group was only 44% of the
mean level in the placebo group. These findings suggest that, in this
study, 4-HPR was biologically active from the standpoint of its effect
on retinoid metabolism, inducing a reduction in serum retinol, but had
no effects on squamous metaplasia or dysplasia.
|
|
DISCUSSION |
|---|
|
TopABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
|---|
The mechanism by which 4-HPR mediates its chemopreventive effect has been investigated extensively. In tissue culture, 4-HPR treatment of cancer cells activates transcription of RAREs through retinoid nuclear receptor-dependent pathways and increases the expression of RAR-ß (27 , 28) . However, we found no effect of 4-HPR on RAR-ß mRNA levels in the bronchial epithelium. This stands in contrast to the effect of 13cRA on RAR-ß mRNA in the bronchial epithelium observed previously (6) . Potential explanations for this finding include: (a) activation of retinoid nuclear receptor-dependent pathways was not a prominent effect of 4-HPR in these patients; or (b) the 4-HPR levels were not sufficient enough to activate this pathway. Retinoid nuclear receptor-dependent pathways are not necessary for some of the biological effects of 4-HPR. For example, retinoid receptor transcriptional activation is not necessary for the apoptotic effects of 4-HPR on cancer cells (29 , 30) . Although the pathways that mediate the apoptotic effects of 4-HPR have not been defined, it has been shown that induction of apoptosis by 4-HPR occurs coincidently with the production of reactive oxygen species and apoptosis is blocked by pyrrolidine dithiocarbamate, an oxygen radical scavenger (31) .
The inactivity of 4-HPR on pathological changes in the bronchial mucosa raises the possibility that serum 4-HPR levels in participants in this study were not high enough to achieve a biological effect. The apoptotic effects of 4-HPR in tissue culture typically require 4-HPR concentrations of >1 µM (14 , 32) . The mean serum level of 4-HPR observed in this clinical trial was 104.5 ng/ml (0.26 µM). Higher serum levels might be achieved by increasing the dose of 4-HPR. The tolerability of higher dose is not known and awaits the results of ongoing Phase I studies. Previously, the dose-limiting toxicities of 4-HPR were visual and ophthalmological toxicities, which occur in 20% and 8%, respectively, of patients at 5 years (33 , 34) . These toxicities are hypothesized to occur because of a reduction in serum retinol levels (22) . Similar to previous studies, we found that serum retinol levels are reduced in 4-HPR-treated individuals. 4-HPR binds to retinol-binding protein in the liver and thereby competes with retinol, decreasing the affinity of retinol-binding protein for transthyretin, reducing serum retinol levels (35 , 36) . Retinol is necessary to maintain the normal growth and differentiation of the bronchial epithelium (37) ; therefore, loss of serum retinol may counterbalance the chemopreventive effects of 4-HPR. However, we have not observed any clinical signs of vitamin A deficiency in 4-HPR-treated participants.
Several clinical trials examining the effectiveness of conventional retinoids in the chemoprevention of lung cancer have been completed. Similar to the outcome of this trial, 13cRA demonstrated no activity in the reversal of bronchial squamous metaplasia and dysplasia in current smokers (5) . Two large, randomized trials that were recently completed (Alpha-Tocopherol Beta Carotene and Carotene and Retinol Efficacy Trial) demonstrated no efficacy of ß-carotene plus retinol (38) or ß-carotene alone (39) in the chemoprevention of lung cancer in current smokers. Another trial that tests the efficacy of 13cRA in the chemoprevention of second primary tumors in patients with resected lung cancers has reached its targeted accrual and is nearing completion. If this trial has a similar outcome, there will be clear evidence that conventional retinoids are not effective in the chemoprevention of lung cancer in smokers.
Whereas conventional retinoids have demonstrated minimal activity as lung cancer chemopreventive agents, the activity of 4-HPR and other novel retinoids should be further explored. Combinations of 4-HPR with retinol should be investigated to examine whether the chemopreventive effects of 4-HPR can be enhanced by restoring normal retinol levels. Phase I studies with high-dose 4-HPR are ongoing, which will determine whether 4-HPR can be tolerated at doses that reach serum concentrations of >1 µM. Long-term administration may be required to attain a chemopreventive effect; five years of administration at the same dose used in this study revealed chemopreventive activity against breast and ovarian cancer (12 , 40) . Once the pathways that mediate the apoptotic effects of 4-HPR are understood, biomarkers of 4-HPR activity might be developed for clinical trials to study its activity in tissues-at-risk (41) , and strategies might be developed to target specific tumor types that are susceptible to 4-HPR actions.
|
FOOTNOTES |
|---|
1 Supported in part by Grant N01CN25433, the
National Foundation for Cancer Research, the Rippel Foundation, and the
Charles LeMaistre Distinguished Chair. W. K. H. is an American Cancer
Society Clinical Research Professor. J. M. K. is the recipient of a
Sidney Kimmel Scholar Award. 
2 To whom requests for reprints should be
addressed, at Department of Thoracic/Head and Neck Medical Oncology,
University of Texas M. D. Anderson Cancer Center, Box 80, 1515
Holcombe Boulevard, Houston, TX 77030.
3 The abbreviations used are: 13cRA,
13-cis-retinoic acid; RARE, RA response element; RAR, RA
receptor; 4-HPR, N-(4-hydroxyphenyl)retinamide; MI,
metaplasia index; 4-MPR, 4-methoxyphenylretinamide; LOH, loss of
heterozygosity; GEE, generalized estimating equation.
Received 3/ 6/00; revised 5/22/00; accepted 5/23/00.
|
REFERENCES |
|---|
|
TopABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
|---|
independent pathway. Oncogene, 18: 5747-5755, 1999.[CrossRef][Medline]
This article has been cited by other articles:
|
|
 |
|
  A. L. Sabichi, S. P. Lerner, E. N. Atkinson, H. B. Grossman, N. P. Caraway, C. P. Dinney, D. F. Penson, S. Matin, A. Kamat, L. L. Pisters, et al. Phase III Prevention Trial of Fenretinide in Patients with Resected Non Muscle-Invasive Bladder Cancer Clin. Cancer Res., January 1, 2008; 14(1): 224 - 229. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 J. Gray, J. T. Mao, E. Szabo, M. Kelley, J. Kurie, and G. Bepler Lung Cancer Chemoprevention: ACCP Evidence-Based Clinical Practice Guidelines (2nd Edition) Chest, September 1, 2007; 132(3_suppl): 56S - 68S. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
S. M. Lippman, J. J. Lee, J. W. Martin, A. K. El-Naggar, X. Xu, D. M. Shin, M. Thomas, L. Mao, H. A. Fritsche Jr., X. Zhou, et al. Fenretinide Activity in Retinoid-Resistant Oral Leukoplakia. Clin. Cancer Res., May 15, 2006; 12(10): 3109 - 3114. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 L. Wang, Q. Wei, L.-E Wang, K. D. Aldape, Y. Cao, M. F. Okcu, K. R. Hess, R. El-Zein, M. R. Gilbert, S. Y. Woo, et al. Survival Prediction in Patients With Glioblastoma Multiforme by Human Telomerase Genetic Variation J. Clin. Oncol., April 1, 2006; 24(10): 1627 - 1632. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
F. R. Hirsch and S. M. Lippman Advances in the Biology of Lung Cancer Chemoprevention J. Clin. Oncol., May 10, 2005; 23(14): 3186 - 3197. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
F. R. Khuri and R. Lotan Retinoids in Lung Cancer: Friend, Foe, or Fellow Traveler? J. Clin. Oncol., September 1, 2004; 22(17): 3435 - 3437. [Full Text] [PDF]
|
|
|
|
|
|
J. S. Kim, H. Lee, H. Kim, Y. M. Shim, J. Han, J. Park, and D.-H. Kim Promoter Methylation of Retinoic Acid Receptor Beta 2 and the Development of Second Primary Lung Cancers in Non-Small-Cell Lung Cancer J. Clin. Oncol., September 1, 2004; 22(17): 3443 - 3450. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
F. R. Khuri and V. Cohen Molecularly Targeted Approaches to the Chemoprevention of Lung Cancer Clin. Cancer Res., June 15, 2004; 10(12): 4249S - 4253S. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 A. S. Tsao, E. S. Kim, and W. K. Hong Chemoprevention of Cancer CA Cancer J Clin, May 1, 2004; 54(3): 150 - 180. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 R. C. Winterhalder, F. R. Hirsch, G. K. Kotantoulas, W. A. Franklin, and P. A. Bunn Jr Chemoprevention of lung cancer--from biology to clinical reality Ann. Onc., February 1, 2004; 15(2): 185 - 196. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 J. M. Kurie, R. Lotan, J. J. Lee, J. S. Lee, R. C. Morice, D. D. Liu, X.-C. Xu, F. R. Khuri, J. Y. Ro, W. N. Hittelman, et al. Treatment of Former Smokers With 9-cis-Retinoic Acid Reverses Loss of Retinoic Acid Receptor-{beta} Expression in the Bronchial Epithelium: Results From a Randomized Placebo-Controlled Trial J Natl Cancer Inst, February 5, 2003; 95(3): 206 - 214. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
J.-C. Soria, X. Xu, D. D. Liu, J. J. Lee, J. Kurie, R. C. Morice, F. Khuri, L. Mao, W. K. Hong, and R. Lotan Retinoic Acid Receptor {beta} and Telomerase Catalytic Subunit Expression in Bronchial Epithelium of Heavy Smokers J Natl Cancer Inst, January 15, 2003; 95(2): 165 - 168. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 C. Zou, A.-T. Vlastos, L. Yang, J. Wang, M. Brewer, and M. Follen Effect of 4-Hydroxyphenylretinamide on Human Cervical Epithelial and Cancer Cell Lines Reproductive Sciences, January 1, 2003; 10(1): 41 - 48. [Abstract] [PDF]
|
|
|
|
 |
|
 J L Mulshine and R A Smith Lung cancer * 2: Screening and early diagnosis of lung cancer Thorax, December 1, 2002; 57(12): 1071 - 1078. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 S. M. Lippman and W. K. Hong Cancer Prevention Science and Practice Cancer Res., September 15, 2002; 62(18): 5119 - 5125. [Full Text] [PDF]
|
|
|
|
|
|
S. Lam, C. MacAulay, J. C. le Riche, Y. Dyachkova, A. Coldman, M. Guillaud, E. Hawk, M.-O. Christen, and A. F. Gazdar A Randomized Phase IIb Trial of Anethole Dithiolethione in Smokers with Bronchial Dysplasia J Natl Cancer Inst, July 3, 2002; 94(13): 1001 - 1009. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
J.-C. Soria, C. Moon, and L. Mao RESPONSE: Re: Effects of N-(4-Hydroxy-phenyl)retinamide on hTERT Expression in the Bronchial Epithelium of Cigarette Smokers J Natl Cancer Inst, June 19, 2002; 94(12): 950 - 951. [Full Text] [PDF]
|
|
|
|
|
|
F. Formelli Correspondence re: M. Follen et al., A Randomized Clinical Trial of 4-Hydroxyphenylretinamide for High-Grade Squamous Intraepithelial Lesions of the Cervix. Clin. Cancer Res., 7: 3356-3365, 2001 Clin. Cancer Res., May 1, 2002; 8(5): 1310 - 1312. [Full Text] [PDF]
|
|
|
|
|
|
M. Follen and H. A. Fritsche Reply Clin. Cancer Res., May 1, 2002; 8(5): 1313 - 1313. [Full Text] [PDF]
|
|
|
|
|
|
S. A. Belinsky, W. A. Palmisano, F. D. Gilliland, L. A. Crooks, K. K. Divine, S. A. Winters, M. J. Grimes, H. J. Harms, C. S. Tellez, T. M. Smith, et al. Aberrant Promoter Methylation in Bronchial Epithelium and Sputum from Current and Former Smokers Cancer Res., April 1, 2002; 62(8): 2370 - 2377. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 S. Bruno, C. Tenca, D. Saverino, E. Ciccone, and C. E. Grossi Apoptosis of squamous cells at different stages of carcinogenesis following 4-HPR treatment Carcinogenesis, March 1, 2002; 23(3): 447 - 456. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
R. C. Young and C. M. Wilson Cancer Prevention: Past, Present, and Future Clin. Cancer Res., January 1, 2002; 8(1): 11 - 16. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
M. Follen, E. N. Atkinson, D. Schottenfeld, A. Malpica, L. West, S. Lippman, C. Zou, W. N. Hittelman, R. Lotan, and W. K. Hong A Randomized Clinical Trial of 4-Hydroxyphenylretinamide for High-Grade Squamous Intraepithelial Lesions of the Cervix Clin. Cancer Res., November 1, 2001; 7(11): 3356 - 3365. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
, smoking at 6 months; 
and 
, nonsmoking at 6
months.