
Clinical Cancer Research Vol. 7, 290-296, February 2001
© 2001 American Association for Cancer Research
Molecular Oncology, Markers, Clinical Correlates |
Overexpression of p53 in Tumor-distant Epithelia of Head and Neck Cancer Patients Is Associated with an Increased Incidence of Second Primary Carcinoma1
Nils Homann,
Matthias Nees,
Christian Conradt,
Andreas Dietz,
Hagen Weidauer,
Heinz Maier and
Franz X. Bosch2
Molekularbiologisches Labor, Universitäts-HNO-Klinik Heidelberg [N. H., M. N., A. D., H. W., F. X. B.], HNO-Klinik, Bundeswehrkrankenhaus Ulm [H. M.], Zentrum für Medizinische Biometrie und Informatik, Universität Heidelberg [C. C.], D-69120, Heidelberg, Germany
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ABSTRACT
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Second primary carcinoma is a peculiar feature of head and neck cancer
and represents a form of treatment failure distinct from the recurrence
of the primary tumor. Whether altered p53 expression in tumor-distant
epithelia at the time of diagnosis is of clinical value as a biomarker
for second primary carcinoma development has not been rigorously
answered because of the lack of long-term follow-up studies involving a
sufficiently large patient cohort. In this prospective study, we have
investigated p53 expression in tumor-distant epithelia and in the
corresponding primary tumors of 105 head and neck cancer patients by
immunohistochemistry on frozen sections. After a median follow-up of 55
months, the clinical course of disease parameters, i.e.,
local recurrences, lymph node and distant metastasis, incidence of
second primary carcinoma, and survival, was evaluated. Overexpression
of p53 in tumor-distant epithelia was found in 49 patients (46.7%),
and it was independent of the p53 protein status of the primary tumor
and of the tumor site, size, stage, and grading. Mucosal p53
overexpression was not associated with local primary recurrences, lymph
node or distant metastases, or overall survival. Importantly, mucosal
p53 overexpression, but not overexpression in the primary tumors, was
significantly associated with an increased incidence of second primary
carcinomas (P = 0.0001; Fishers exact test). When
the times to second primary tumor occurrence were analyzed by the
Kaplan-Meier method, the difference remained significant
(P = 0.005; log rank test). We conclude that IHC
staining for p53 overexpression in tumor-distant epithelia provides a
simple and rapid tool to identify head and neck cancer patients at
increased risk of developing second primary tumors. Because p53
overexpression in these epithelia in our patient cohort was
specifically associated with second primary cancer but not with
recurrences, at least a fraction of the second primary cancers appears
to have resulted from genetic events in the mucosa ("field
cancerization").
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INTRODUCTION
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SCC3
of the head and neck is the sixth most common malignancy in the world,
and the 5-year survival rate is one of the lowest among all cancers
(1)
. Accumulation of mutations in oncogenes and tumor
suppressor genes is a major molecular mechanism of tumor development
(2)
. Among the tumor suppressor genes, inactivation of the
p53 gene is one of the most frequent events
(3)
. Overexpression of the p53 protein is frequently but
not always associated with gene mutation and is regarded to be a
promising candidate that might predict patient prognosis
(4)
. Taking recent publications together, there is now
good evidence for a prognostic impact of p53 mutations in head and neck
cancer, i.e., they seem to be associated with an increased
risk of locoregional treatment failure (5
, 6)
. p53 DNA
contact mutations appear to harbor a distinctly high malignant
potential and to predict a poorer survival (7)
. Regarding
p53 overexpression, Shin et al. (8)
, in their
cohort of 69 patients with definitive local therapy (46% were stage I
and II tumors), demonstrated a predictive value of p53 overexpression
for shorter survival. However, other studies failed to confirm these
results or revealed contradictory results (9, 10, 11, 12, 13)
.
p53 overexpression not only occurs in 2370% of all head and neck
tumors (4)
but also has commonly been found in dysplastic
and nondysplastic premalignant epithelial lesions (9
, 14, 15, 16, 17, 18)
. Even less is known about the clinical value of the
observed p53 overexpression in these epithelia. Uhlmann et
al. (15)
performed a retrospective study on laryngeal
cancer patients who previously underwent laryngeal biopsies without the
diagnosis of cancer. Linear basal overexpression of p53 in premalignant
lesions was found to be significantly associated with an increased risk
of progression to cancer (15)
. In a prospective study,
Gallo et al. (16)
have reported that
simultaneous p53 and p16INK4a alterations in
premalignant laryngeal lesions have prognostic relevance in the
progression to a malignant tumor. Thus, in the case of laryngeal
precursor lesions, p53-overexpressing cells seem to have some malignant
potential. In oral premalignant lesions, the predictive power of p53
overexpression appeared even less pronounced than in laryngeal lesions.
Ogden et al. (17)
have noted that p53
overexpression does not necessarily predict further malignant disease.
Taking these studies together, it is clear that p53 overexpression will
not turn out to be a definitive biomarker (indicating 100% risk) for
second primary carcinoma (reviewed in Ref. 18
). Whether
p53 overexpression has reasonable predictive power at all has not been
rigorously answered. For answering this question, long-term follow-up
studies are required. For instance, on the basis of an actuarial rate
of second primary cancer of 10% and on an 3-fold increase of this rate
in a patient group with p53-positive, tumor-distant epithelia, a cohort
size of 50 patients will only provide a study power of 50%. Therefore,
the literature does not contain a study with a sufficiently large
number of patients to answer this question.
We have shown previously that in multiple anatomical sites within one
cancer patient, histologically normal appearing tumor-distant
epithelial cells can be found that express a mutated p53 protein
(19)
. This finding, which was confirmed by Waridel
et al. (20)
, has provided a possible molecular
basis for the development of second (multiple) primary carcinomas.
Here, we present a prospective long-term follow-up study involving 105
patients (including 15 patients from our previous work) with malignant
head and neck tumors. We have focused on the analysis of p53 protein
expression in tumor-distant epithelia at the time of surgery of the
primary tumor and have compared this with clinicopathological
parameters, including the occurrence of second primary carcinoma.
Immunohistochemical staining of tissue sections is a simple, rapid, and
reliable method to assess p53 protein expression and can be performed
according to standard protocols in many clinical laboratories. The size
of our patient cohort was estimated to be sufficiently large to answer
whether p53 overexpression is associated with second primary
carcinomas.
Our results show that it is indeed possible, using this simple assay,
to identify patients with higher and lower risk for second primary SCCs
of the head and neck.
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PATIENTS AND METHODS
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Patients and Tissue Samples.
Clinicopathological parameters from patients with head and neck cancer
were obtained from patient records and the statements of the pathology
department. Only patients from whom fresh-frozen biopsies could be
obtained and who were regularly seen at follow-up examinations were
recruited. The enrollment period started from May 1990 and ended in
December 1998. Inclusion criteria were SCC only (excluding skin cancer)
and patients presenting with primary tumors (excluding patients with
recurrent tumors and patients with secondary tumors who had been
treated with radiation and/or chemotherapy) at the Department of
Oto-Rhino-Laryngology of the University of Heidelberg. Accuracy of
the clinical data was validated by two independently reviewing
investigators, who were unaware of the results of p53 staining. The
data collected included age, gender, primary tumor site (oral cavity,
oropharynx, larynx, hypopharynx, or other), tumor size
(T14), lymph nodal status
(N03), American Joint Committee on Cancer Stage
(stages IIV), histological grading (well, moderately, poorly, and
undifferentiated), and cause of death. In follow-up, recurrences of
primary tumor and occurrences of lymph node metastases, distant
metastases, and second primary tumors were recorded. For the diagnosis
of second primary tumors, a modification of the criteria of Warren and
Gates was used (see Ref. 21
). Only second primary tumors
occurring in the aerodigestive tract were enrolled in this study.
All tissues were collected during the operation and immediately
snap-frozen in 2-methyl-butane, precooled in liquid nitrogen, and
stored until use at -80 C. One hundred fifty-one snap-frozen,
tumor-distant epithelial tissues were available for study. Precise
information on the anatomical location was available in 113 cases (the
other biopsies were merely classified as tumor-distant). The
tumor-distant epithelia were derived from the site adjacent to the
tumor (e.g., oropharyngeal mucosa in case of a larynx
carcinoma and hypopharyngeal mucosa in case of an oropharynx carcinoma)
or from the contralateral subsite in case of oral cavity and larynx
tumors (see Table 2
). These small biopsies had a minimum distance of 4
cm to the margin of the tumor and were histopathologically tumor free.
Epithelia of 63 patients who underwent operation for other reasons than
malignancy were collected for comparison.
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Table 2 p53 expression in normal and mildly dysplastic
epithelia in patients with and without malignancy in the head and neck
region, and sites of expression
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Immunohistochemistry.
Immunohistochemical staining of the frozen sections with p53-antibody
Bp53-12 (Progen, Heidelberg, Germany) was performed as described
earlier (19)
. Tissues were ranked as p53 positive if
parabasal cell clusters or a continuous cell nest of more than five
cells with a strong nuclear staining were seen. Faint cytoplasmic or
nuclear staining not meeting the former criteria and all other tissues
were ranked as p53 negative. In case of availability of several tissues
from one patient, one positive epithelium was enough to rank the
patient as p53 positive for tumor-distant epithelia.
Statistical Analysis.
The major statistical endpoints of this study were the incidence and
the time to diagnosis of posttherapeutic events during follow-up, in
particular local recurrence from primary carcinoma or second primary
carcinoma, in relation to the p53 expression status in tumor-distant
epithelia or primary tumors, respectively. Events of tumor relapse were
calculated from the date of initial therapy. Calculations were
performed by using Fishers exact test or unpaired Students
t test (GraphPad version 2.02; InStat Software) for
univariate analyses. P < 0.05 was regarded as
significant. All Ps are expressed as mean ± 1 SD. The
Kaplan-Meier method was used to compare the incidence and time course
of tumor relapse events between groups with p53 positivity and p53
negativity. Differences were quantitated and evaluated for significance
using the log-rank test stratified for tumor site.
The study was approved in accordance with the declarations of Helsinki.
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RESULTS
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One hundred five patients met the inclusion criteria. The p53
expression status in the primary tumors and in the tumor-distant
epithelia of these patients and the main clinical characteristics are
summarized in Table 1
. Forty-nine cancer patients (46.7%) revealed p53-positive epithelia,
whereas no p53 positivity could be detected in epithelia obtained from
63 noncancer patients. Examples of p53 positivity in frozen sections of
tumor-distant epithelia are presented in Fig. 1
. The pattern seen in Fig. 1
a, i.e., two
parabasally located small clusters of stained cells, represents the
threshold positivity. Fig. 1
b shows the staining pattern
most often encountered in tumor-distant mucosa, i.e.,
staining of basal and parabasal cells. The positive staining in Fig. 1
c extended from the basal-most layer into the first
suprabasal layers. This pattern was reported to be predictive for
second primary cancer (22)
. For comparison, Fig. 1
d shows the transition from negative to positive in close
proximity of a SCC. p53 expression in the epithelia did not correlate
with the p53 protein status of the primary tumor; neither did it
correlate with tumor size, tumor stage, nodal status, or histological
grading. Regarding smoking habits, there was an insignificant
difference between the two groups. Smoking habits remained balanced
between the groups during follow-up. Because this study focused
primarily on the question of a predictive role of the p53 protein
status in tumor-distant mucosa at the time of presentation with the
primary tumor, we did not attempt to obtain detailed information about
tobacco consumption. The follow-up period ranged from 5 to 106 months,
with a mean time of 55 months. The median occurrence of tumor-dependent
events was 9.9 ± 6.2 months (mean ± 1 SD) for primary
recurrences (n = 20), 42.8 ± 26 months for second
primary tumors (n = 15), 25.5 ± 25.3 months for
lymph node metastases (n = 20), and 15.5 ± 11.7
months for distant metastases (n = 24). Forty-two
patients died during the follow-up period. Death rate, the occurrence
of new lymph node and distant metastases, and recurrences of the
primary tumor were not associated with p53 overexpression in the
epithelia. However, the rate of second primary tumors in the
aerodigestive tract was significantly higher in patients whose
epithelia showed p53 overexpression (14 versus 1 in the
p53-negative group). Table 2
demonstrates that p53-positive cell clusters were seen more frequently
in epithelia of the hypopharynx than in the oropharynx, oral cavity, or
larynx; this difference was, however, not significant. Within
anatomical subgroups of the larynx, p53 overexpression was
significantly more frequent in supraglottic and glottic regions than in
the subglottis. Fig. 2
A shows that Kaplan-Meier analyses and log-rank tests
confirmed the significant association between p53 overexpression
specifically in the epithelia and second primary malignancy. The same
analysis confirmed the lack of such a correlation of p53 overexpression
in the epithelia with local recurrences from the primary tumors (Fig. 2
B). There was also no significant influence of mucosal p53
overexpression with disease-free and overall survival (not shown).
Importantly, we could not find a correlation between the p53 status in
the primary tumors and the incidence of second primary tumors (Fig. 2
C). This latter result was confirmed either when a larger
cohort of 250 patients including the 105 patients of this study was
analyzed or when those patients were analyzed separately, of whom no
tumor-distant mucosal biopsies were available (not shown). The
anatomical site of the second primary tumors did not significantly
correlate with the sites from where the mucosal biopsies analyzed had
been taken (not shown).
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Table 1 Characteristics of the patients of the study
In some cases, collected data were insufficiently recorded, which led
to a lack of information in some groups. For smoking and drinking
habits, only patients who had participated in another case-control
study to evaluate possible risk factors for head and neck cancer were
included.
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Fig. 1. Patterns of p53 expression in frozen
sections of tumor-distant mucosal biopsies (immunohistochemistry with
Bp53-12 monoclonal antibody. a, two parabasally located
small clusters of stained cells in epithelium from the ventricular
fold, defined as threshold positivity; b, basal and
parabasal staining in hypopharyngeal mucosa; c, strongly
positive staining extending into suprabasal layers in hypopharyngeal
mucosa; d, for comparison, staining at the transition
from mucosa to p53-positive SCC.
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Fig. 2. A, incidence and time course of
occurrence of second primary carcinomas in relation to the p53
expression status in tumor-surrounding epithelia. Comparison by the
Kaplan-Meier method. The median time of occurrence of second primary
tumors was 42.8 months; the single case in the p53-negative group
occurred after 54 months. Stratified log-rank test revealed a
significant difference between the groups (P =
0.0059). B, incidence and time course of occurrence of
local recurrences from the primary tumors in relation to the p53 expression status
in tumor-surrounding epithelia. Comparison by the Kaplan-Meier method.
The incidence of primary recurrences was insignificantly higher in the
p53-negative group (P = 0.2765; stratified log-rank
test). C, second primary carcinomas in relation to the
p53 expression status of the primary tumors. Eighty-nine primary tumors
were analyzed by the Kaplan-Meier method. Fifty tumors were p53
positive, but the number of second primary tumors was the same in the
two groups (n = 5 each). Thus, the p53 protein
status in the primary tumor did not correlate with second primary
cancer. p53sh = 0, p53 negative; p53sh
= 1, p53-positive mucosa.
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DISCUSSION
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The prognosis of head and neck cancer patients with definitive
locoregional tumor treatment is influenced by a peculiar characteristic
of this cancer typethe frequent incidence of second primary tumors
(21)
. In the present study, we have used
immunohistochemistry and long-term follow-up on a sufficiently large
number of cases to examine whether the frequently observed
overexpression of p53 in tumor-distant epithelia of head and neck
cancer patients (14, 15, 16, 17, 18)
could be a biomarker with
predictive value for second primary cancer. We show that overexpression
of p53 in tumor-distant epithelia was associated with an increased
incidence of second primary carcinoma (Table 1
; Fig. 2
). At the same
time, as shown in Table 1
and Fig. 2
C, the data provide
strong evidence against a correlation between the p53 protein status in
the primary tumor and the occurrence of second primary tumors. This is
in contrast to the study by Shin et al. (8)
,
who have described a weak association between p53 overexpression in the
tumor and the rate of second primary carcinoma. In another large cohort
of
145 head and neck cancer patients in which no tumor-distant
mucosal biopsies were available, we also did not obtain any evidence
for an association of p53 overexpression in the primary SCCs and the
rate of second primary carcinoma (data not shown).
This is, to our knowledge, the first study of a sufficiently
large-scale providing evidence that p53 overexpression in tumor-distant
mucosa of head and neck cancer patients indicates an increased
predisposition or susceptibility of the mucosa of these patients to
progression to a second malignant tumor. We have gathered several
arguments to support this notion: (a) as a consequence of
using frozen sections rather than paraffin sections, we noted that p53
positivity was extremely specific for tumor-distant epithelia of cancer
patients (Table 2)
. In contrast, staining of paraffin sections after
antigen retrieval has a much lower specificity for malignancy or
premalignancy because p53 positivity is also found in benign epithelial
lesions (23)
and in mucosal biopsies from healthy
individuals (24)
. In the latter study, van Oijen et
al. (26)
found that smoking increased the frequency
of p53 overexpression among cancer patients but not among healthy
individuals. In our cohort, the incidence of p53 overexpression was
also higher in the smoking group, but the difference was not
statistically significant (Table 1)
; (b) because these
epithelia were picked at random, either from the adjacent anatomical
site or from the contralateral subsite, they represent an undefined
entity (in contrast to leukoplakias, for example), in line with a
prospective study design. This makes confounders unlikely to occur;
(c) the second primary tumors occurred much later than the
local recurrences from primary tumors (9.9 ± 6.2 months for
primary recurrences and 42.8 ± 26 months for second primary
tumors). This difference in the time interval to presentation with
secondary cancer is regarded to be crucial for the discrimination
between second primary and local recurrence, although in individual
cases discrimination may be difficult. Jones et al.
(21)
in a large retrospective study found an actuarial
second primary rate of 9.1% and a median time to presentation of 36
months. Our data therefore indicate that the second primaries have
originated independently from the local recurrences. This is in line
with previous findings by Chung et al. (25)
and
van Oijen et al. (26)
, who showed discordant
p53 gene mutations in primary and second primary cancers and
with discordant p53 gene mutations in primary tumor and tumor-distant
mucosa (19
, 20)
; (d) it is noteworthy that the
anatomical distribution of p53 positivity correlated well with the
tumor site distribution. In the larynx, only supraglottic and glottic
regions but not subglottic regions showed p53 overexpression. This is
interesting, because subglottic tumors are very seldom seen; and
(e) most importantly, we have demonstrated a predictive
value for second primary carcinoma only for the p53 status of the
epithelia but not for the p53 status of the primary tumors. This last
argument supports the notion that the second primary tumors can result
from events in the epithelia, as postulated by the "field
cancerization" concept (27)
. Our failure to find a
correlation between p53 positivity in tumor-distant epithelia and tumor
size and stage, as well as between second primary malignancy and
primary tumor size and stage, also supports the alternative concept of
field cancerization as a major basis of second primary malignancy in
head and neck cancer.
Our results confirm earlier studies that had already revealed some
predictive impact of p53 overexpression for malignant transformation
(15, 16, 17)
. It should be stressed again, however, that our
results also agree with the conclusion of another recent study on 21
patients with oral cancer, that p53 overexpression does not necessarily
predict further malignant disease (16)
, because the
positive predictive value of the p53 expression status in tumor-distant
epithelia for second primary tumors is moderate. Although the actuarial
rate of second primary cancer in our total patient cohort was 14.3%,
this rate increased to 28.6% in the p53-positive group (14 of 49
patients were affected), whereas in the p53-negative group, the rate of
second primary cancer was only 1.8%. Hence, the difference between the
groups regarding risk of second primary cancer was large (odds ratio,
22.0). Because of the very high specificity of p53 overexpression for
the mucosa in patients with a malignant tumor and the good sensitivity
of mucosal p53 overexpression in relation to second primary cancer, it
is a good biomarker for the development of second primary tumors
(irrespective of whether this results from field cancerization or by
intraepithelial spread).
What is the relationship between p53 overexpression and p53
gene mutation in tumor-distant mucosa, and would the identification of
p53 gene mutation in tumor-distant epithelia provide a
better predictor for second primary tumor development? Previously, we
found p53 gene mutations only in a fraction of the
tumor-surrounding epithelia with p53 overexpression (19)
.
We have preliminary data from DNA sequencing of p53-positive mucosal
biopsies from 11 patients, 4 of whom had second primary cancer in the
upper aerodigestive tract. Among the latter group, 18 microdissected
areas were sequenced. In 5 lesions, including those presented in Fig. 1
, b and c, mutations were found, attributable to
three of the four patients with second primary cancer
(mutation:overexpression ratio, 0.28). The mutational status differed
from the primary tumors. In the group of 7 patients without second
primary tumor in the upper aerodigestive tract, sequencing 11
p53-positive microdissected areas revealed one mutation
(mutation:overexpression ratio, 0.01). It seems notable that this
patient experienced a prostate carcinoma as second primary malignancy
(data not shown). On the basis of this limited experience, the
assumption seems justified that the correlation between p53 mutation
and overexpression is generally low in tumor-distant mucosal lesions,
and the benefit of mutational analysis would be uncertain. Large-scale
mutational analysis of tumor-distant mucosal biopsies as it was
performed in the basic studies (19
, 20)
, which is very
expensive and time consuming, is not feasible for most clinical
laboratories and for a large number of cases, whereas
immunohistochemical staining using established protocols is easy to set
up and gives fast and reliable information. Furthermore, mutational
analysis is confronted with the problem that negative results are not
conclusive. This is because these lesions are mostly very small (note
the PCR-SSCP analyses in Ref.
19
),4
and it is not clear whether microdissection of undefined mucosal areas
will actually catch cells with p53 mutations. Possibly, the new DNA
chip technology can be adapted to identify mutations despite a high
background of wild-type sequence (28)
.
It is also possible that other markers might improve the positive
predictive value of p53 overexpression for the individual epithelial
lesions. Because cytogenetic alterations are another hallmark of
premalignant and malignant transformation and have been found to be
correlated with p53 overexpression and mutation (Ref. 29
and references therein), allelic imbalances assessed by microsatellite
marker analysis (30)
and numerical chromosomal aberrations
assessed by fluorescence in situ hybridization (25
, 30, 31, 32, 33)
appear particularly promising.
In conclusion, p53 overexpression in tumor-distant epithelia should
serve as a biomarker to identify those patients who are at high risk to
develop second primary carcinomas. Because patients with locally cured
malignant tumors are more likely to die from a second primary carcinoma
rather than from the recurrence of the primary tumor itself, this
potential biomarker may allow new intervention strategies for those
patients.
 |
ACKNOWLEDGMENTS
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We are greatly indebted to Antje Schuhmann and Wolfgang
Klein-Kühne for excellent technical support. We specifically
thank Dr. Christa Flechtenmacher, Institute of Pathology, University of
Heidelberg, for histopathological assessment and helpful discussions.
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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.
1 This study was supported by the Wilhelm
Sander-Stiftung, the Verein zur Förderung der Krebsforschung in
Deutschland e.V., the Tumorzentrum Heidelberg/Mannheim, and the
Forschungsförderungsprogramm der Medizinischen Fakultät
Heidelberg. 
2 To whom requests for reprints should be
addressed, at HNO-Klinik, Molecular Biology Laboratory, University of
Heidelberg, Im Neuenheimerfild 400, D-69120, Heidelberg, Germany.
Phone: 49-6221-56-7278; Fax: 06221/564604; E-mail: Franz_Bosch{at}med.uni-heidelberg.de 
3 The abbreviation used is: SCC, squamous cell
carcinoma. 
4 Unpublished observations. 
Received 6/12/00;
revised 11/20/00;
accepted 11/20/00.
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