
Clinical Cancer Research Vol. 6, 1445-1451, April 2000
© 2000 American Association for Cancer Research
Molecular Oncology, Markers, Clinical Correlates |
Clinical Significance of Serum Soluble Interleukin 2 Receptor-
in Esophageal Squamous Cell Carcinoma1
Liang-Shun Wang2,
Kuan-Chih Chow,
Wing-Yin Li,
Chia-Chuan Liu,
Yu-Chung Wu and
Min-Hsiung Huang
Division of Chest Surgery, Departments of Surgery [L-S. W., C. C. L., Y-C. W., M-H. H.] and Pathology [W-Y. L.], Veterans General Hospital in Taipei and National Yang-Ming University, Taipei, and Department of Medical Research, China Medical College Hospital, Taichung, 11217 Taiwan, Republic of China [K-C. C.]
 |
ABSTRACT
|
|---|
Although
the serum level of soluble interleukin-2 receptor
(sIL-2R
) has
been shown to correlate with progression and prognosis of several
cancers, data to support its clinical significance to esophageal
squamous cell carcinoma (ESCC) are limited. This study was conducted to
assess the prognostic value and source of sIL-2R
in patients with
ESCC. From January 1986 to June 1997, 125 patients with
histopathologically confirmed ESCC were enrolled for study.
Ninety-three patients underwent en bloc esophagectomy, and 32 patients
with unresectable tumor underwent palliative surgery. Four (4.3%; 4 of
93) patients died of surgical complications. Serum levels of sIL-2R
were measured by ELISA. Expression of IL-2R
, IL-2Rß, and IL-2R
in the pathological section was determined, respectively, by
immunohistochemistry (IHC) and in situ hybridization
(ISH). Compared with the healthy control group (1020 ± 476 pg/ml,
n = 103), ESCC patients tended to have
significantly higher serum sIL-2R
concentrations (1424 ± 798
pg/ml, n = 121). The sIL-2R
level was correlated
with age, Tumor-Node-Metastasis classification, tumor stage, reading
score of the IHC staining, and survival but not with the pathological
grade or lymphovascular invasion. Prognosis was worse for patients with
high sIL-2R
levels (
1500 pg/ml) than for those with low serum
sIL-2R
levels (<1500 pg/ml; P = 0.0209). It can
be used as an independent prognostic factor of ESCC. In the
pathological sections, expression of IL-2R
, IL-2Rß, and IL-2R
was detected in 17 (18.1%), 83 (89.2%), and 83 (89.2%) cases,
respectively, by IHC, and the message of IL-2R
was identified in
tumor cells by ISH in 30.1% (28 of 93) of the cases. Serum
concentrations of sIL-2R
are frequently elevated in ESCC patients
and are correlated with disease progression and survival. These data
indicate that, in addition to activated T cells, cancer cells could be
an important source of sIL-2R
in ESCC patients.
 |
INTRODUCTION
|
|---|
ESCC3
is
common in Mainland China and Taiwan (1, 2, 3)
. Although
surgery provides a chance of cure for early-stage esophageal
malignancies, most of the patients present with advanced disease. The
poor prognosis is further compounded with frequent relapse and early
metastasis (4)
. Therefore, it is important to detect
disease progression and metastasis as early as possible to improve
timely treatment and improve survival.
Several recent studies have shown that TNM stage and the number of
diseased lymph nodes are two important factors associated with the
prognosis of ESCC (5, 6, 7, 8, 9)
. Although these two factors can
only be assessed during surgery, they are not applicable for monitoring
disease advancement and the potential of metastasis. On the other hand,
serum biomarkers are often associated with the biological behavior of
cancer cells. The prognostic measure of a serum biomarker that can
reflect the concerted interaction between the tumor and the host immune
system may provide scientific insight to improve the therapeutic
strategy. However, the serum biomarkers that can be used as
complementary prognostic factors are very few for patients with ESCC.
IL-2, a glycoprotein produced by the activated T cells, can promote the
growth of T cells, B cells and natural killer cells by binding to the
IL-2R. On the activated T cells, IL-2R consists of three components:
chain (Ka = 10-8
M), ß chain (Ka =
10-7 M), and
chain
(Ka undetectable; Ref. 10
, 11
). Only
chain
and ß chains can bind to IL-2; the
chain alone does not bind to
IL-2. Nevertheless, both ß and
chains are required for
transduction of proliferative signals. On the resting T cell, the
heterodimeric IL-2Rß
chain (Ka =
10-8 M) is constitutively
expressed. Once activated by IL-2, T cells start to synthesize
IL-2R
. The newly synthesized IL-2R
chain joins IL-2Rß or
IL-2Rß
to form the membrane-bound heterodimeric IL-2R
ß
(Ka = 10-10
M) or heterotrimeric receptor IL-2R
ß
(Ka = 10-11
M). Expression of IL-2R
is therefore a
landmark of T-cell activation. However, a truncated form of IL-2R
,
sIL-2R
, that has only an extramembranous domain can also be
simultaneously detected in the serum (11, 12, 13, 14)
. The
affinity of sIL-2R
to bind to IL-2 is similar to that of the
membrane-bound
chain (15
, 16)
.
Clinically, serum sIL-2R levels tend to increase in patients with
tuberculosis and autoimmune diseases (17)
. In addition, an
elevated serum concentration of sIL-2R
is also suggested to
correlate with adverse prognosis in patients with nasopharyngeal
carcinoma (18
, 19)
, colorectal cancer (20
, 21)
, breast cancer (22)
, ovarian cancer
(23, 24, 25)
, gastric cancer (26
, 27)
, lung
cancer (28
, 29)
, and leukemia (30
, 31)
. It is
worth noting that in these malignancies the increased sIL-2R
levels
not only are associated with disease activities and treatment response
but also indicate the pathogenetic significance in disease progression.
In this study, we measured the serum sIL-2R
levels in patients with
ESCC to evaluate its relationship with tumor stage, lymph node
metastasis, depth of tumor invasion, pathological findings (grades and
lymphovascular invasion), and survival. We also identified the
prospective source of IL-2R in the pathological sections by IHC and
ISH.
 |
PATIENTS AND METHODS
|
|---|
Human Sera and Tissue Specimens.
From January 1986 to June 1997, 125 consecutive patients with
histopathologically proven ESCC were enrolled for study. The average
age was 64.5 ± 10.7 years, and the ratio of male:female was 40:3.
Tumor stage was classified according to the TNM system
(32)
. Medical Ethical Committee approved the protocol, and
the written informed consent was obtained from every patient before
surgery. Extensive preoperative measures including esophagoscopy with
biopsy, esophagogram, chest radiography, sonograms of abdomen and neck,
computed tomography of the chest, and radionuclide bone scanning were
followed to determine the need of surgery. Patients with resectable
tumor (n = 93) underwent en bloc esophagectomy with
locoregional lymphadenectomy through right thoracotomy, laparotomy with
reconstruction using the stomach through a retrosternal route, and
cervical esophagogastrostomy (33)
. For patients at stage
IIb or beyond, concurrent chemoradiotherapy was applied after surgery
(4)
. Patients with unresectable tumor (n =
32) received chemoradiotherapy after the installation of feeding
jejunostomy or bypass procedure. None of these patients received
neoadjuvant therapy. After treatment, all patients were followed
regularly. Four patients (4.3%) died of cardiopulmonary complication
after surgery and were excluded from the prognosis analysis. Serum
samples were obtained from each patient at the time of diagnosis. Serum
samples from 103 healthy individuals with equivalent distribution of
age and sex were used as normal controls. After centrifugation of the
peripheral blood, serum samples were stored at -20°C until assayed.
ELISA.
The serum level of sIL-2R
was measured with Quantikine human IL-2
sR
(R&D Systems, Inc., Minneapolis, MN). Briefly, diluted serum
(1:4) and peroxidase-conjugated polyclonal antibody specific to
IL-2R
was added to each well having been precoated with monoclonal
antibody specific to IL-2R
. After incubation at room temperature for
3 h, the reaction solution was aspirated, and the microtiter plate
was washed with wash buffer four times. Positive reaction was
identified by developing with chromogen solution containing
3,3',5,5'-tetramethylbenzidine at room temperature for 20 min. The
concentration of sIL-2R
was then determined with concomitant
calibration of standard IL-2R
by reading at A450 nm (MRC; Dynatech
Laboratories, Inc., Chantilly, VA). The individual sample was done in
duplicate. Samples with overscaled readings were further diluted before
measurement.
Immunohistochemistry and Slide Evaluation.
Antibodies used for IHC were specific to IL-2R
(Dako, Kyoto, Japan),
IL-2Rß, and IL-2R
(Santa Cruz Biotechnology, Santa Cruz, CA).
Immunological staining was performed by an immunoperoxidase method
(34)
. Aminoethyl carbazole was used as chromogenic
substrate and crimson precipitate was identified as positive staining.
Samples were counterstained with hematoxylin, and slides were mounted
with glycerol gelatin. Each batch had a positive and a negative control
to ensure quality. Slide was evaluated as described previously
(35)
. Briefly, each slide was evaluated randomly at four
areas that contained tumor cells and was photographed. In each case,
normal epithelial area of the esophageal tissue served as internal
negative control. Slides were read by two independent pathologists
having no knowledge of their clinicopathological status. The signal of
stain was scored on a 0 to 2 plus subjective scale with 0 = no
expression, 1+ = intermediate expression, and
2+ = strong expression. Four areas were examined
on three slides from each patient, resulting in 12 scores. An average
was taken as the final reading. After judging specificity from the
internal negative control, an average score >0.3 was defined as
positive for the expression of IL-2R and otherwise as negative.
ISH.
A nonisotopic method with FITC-labeled IL-2R
antisense
oligonucleotides was used to detect the expression of IL-2R
mRNA
(24)
. The probe sequences are as follows:
5'-GGAAACCTCTCTTGCATCACAGTTCAACATGG-3'
(IL-2R
mRNA, nucleotides 337306);
5'-AGTGGCAGAG-CTTGTGCATTGACATTGGTTGT-3' (KC
2, nucleotides
439408); 5'-AGACACTCTCAGCAGGACCTCTGTCTA-GAGCC-3' (KC
3,
nucleotides 681651); 5'-CACTCAGGAGGAGGACGCTGATCAGCAGG-3'
(IL-2R
mRNA, nucleotides 946918). Hybridization products
were visualized by using alkaline phosphatase-conjugated polyclonal
antibodies to FITC (Amersham International, Buckinghamshire,
United Kingdom) and chromogen nitroblue
tetrazolium/5-bromo-4-chloro-3-indolyl phosphate (Sigma Chemical Co.,
St. Louis, MO). Positive staining was identified microscopically as
brownish blue granules at the site of hybridization.
Statistical Analysis.
The results are expressed as mean ± SD. The relationship between
serum sIL-2R
level and each of the clinicopathological parameters
(age, lymph node involvement, distant metastasis, cell differentiation,
lymphovascular invasion, and tumor stage) was analyzed by
2 analysis. When any analysis cell had fewer
than five cases, the Fishers exact test was used. The statistical
difference between groups A and B in each clinicopathological category
was determined by Students t test (two-tailed) or ANOVA.
Correlation between serum sIL-2R
level and the immunohistochemical
reading score of IL-2R
expression in ESCC patients was analyzed by a
simple curve fit test. Survival curves were plotted with method of
Kaplan-Meier. The statistical difference in survival between different
groups was compared by the log-rank test. Survival correlation with the
prognostic factors was further investigated by multivariate analysis
using Cox proportional hazards model with backward stepwise likelihood
ratio. Statistical analysis was performed using SPSS statistical
software (Chicago, IL). Statistical significance was assumed for
P < 0.05.
 |
RESULTS
|
|---|
Serum sIL-2R
Level and Clinicopathological Features in ESCC
Patients.
Serum sIL-2R
was 1020 ± 476 pg/ml in normal healthy controls
(range, 287.81621 pg/ml; n = 103) and was
significantly higher in patients with ESCC (1424 ± 798 pg/ml;
n = 121; P < 0.005). It was above the
normal range in 70.2% (85 of 121) of ESCC patients before surgery, and
31.4% (38 of 121) of them had >1500 pg/ml, the mean plus 1 SD as
determined from the control. Using 1500 pg/ml as the cutoff value,
these ESCC patients were then divided into group A (n =
38) as those with the higher level (
1500 pg/ml; mean, 2357.6 pg/ml;
range, 1507.64601 pg/ml) and group B (n = 83) as
those with lower level (<1500 pg/ml; mean, 996.2 pg/ml; range,
253.61474 pg/ml).
2 analysis showed that the
preoperative serum sIL-2R
levels correlated well with tumor stage,
the depth of tumor invasion (T status), lymph node involvement (N
status), distant metastasis (M status), and age (Table 1)
. Higher sIL-2R
levels were related
to disease progression (Table 2)
. Serum
levels of sIL-2R
were significantly higher in patients with lymph
node metastasis or advanced-staged tumors than in those without lymph
node involvement or early-stage tumors. However, although the patients
were grouped by their histopathological findings (pathological grade or
lymphovascular invasion), no more differences could be found in their
serum sIL-2R
levels (Tables 1
and 2)
.
Correlation of Serum sIL-2R
Level with the Prognosis of ESCC
Patients.
The overall cumulative survival rates of our patients were 41% at 2
years and 19% at 5 years. In view of the serum sIL-2R
level, group
A patients seemed to have much worse prognosis than group B patients
(P = 0.0209; Fig. 1
). The
cumulative 2-year survival rate for group A patients was 29.8% and for
group B patients was 47.6%. The median survival for group A was 8.8
months, and for group B was 21.3 months. Among patients who had
persistently high sIL-2R
levels or a marked increase of sIL-2R
level within a short interval (16 months) after esophagectomy,
distant metastasis of cancer (8 of 13) was found frequently. On the
other hand, patients with a low preoperative level of sIL-2R
(n = 12) or having sIL-2R
levels decreasing after
esophagectomy (n = 5) could remain disease free for
1223 months (17 of 17). As aforementioned, the depth of tumor
invasion, lymph node metastasis, distant nodal or organ metastasis, and
age correlated well with the sIL-2R
level. The further multivariate
analysis also showed them as the independent factor of patient survival
(lymph node metastasis, P = 0.0014; depth of tumor
invasion, P = 0.003; distant organ metastasis,
P = 0.0118; and sIL-2R
, P = 0.0311).
Expression of IL-2Rs in the Pathological Sections.
IHC and ISH were used to determine IL-2R expression in the pathological
sections. By IHC, expression of IL-2R
(Fig. 2A),
IL-2Rß (Fig. 2B),
and IL-2R
(Fig. 2C)
was noticed,
respectively, in 28 (30.1%), 83 (89.2%), and 83 (89.2%) cases of
pathological sections (n = 93). However, the hybridized
product of IL-2R
mRNA was detected in tumor cells only in 18.3% (17
of 93) of the cases (Fig. 2D).
Interestingly, all IL-2R
mRNA positive cases were identified to have a high level of serum
sIL-2R
(>1500 pg/ml). Cricket Graph software was used to estimate
the relationship between serum sIL-2R
level and the reading score of
immunohistochemical IL-2R
expression (Fig. 3)
and found significant correlation
between both parameters, shown by a simple curve fit
(R2 = 0.732).
 |
DISCUSSION
|
|---|
Several studies have shown that the clinical response of
esophageal carcinoma is correlated with tumor stage and lymph node
metastasis (5
, 9)
. We have also found elevated serum IL-6
not uncommonly in ESCC patients, and its association with tumor stage
and lymph node metastasis in turn renders a poor prognostic measure
(36)
. The present study further supports elevated serum
sIL-2R
in ESCC patients and its correlation with poor prognosis.
In recent years, patient immune competence has emerged as a clinically
important parameter closely associated with the treatment outcome of
the cancer patient (37, 38, 39)
. Early tumor recurrence and
disease progression are believed to have something to do with the rapid
growth of tumor cells and the evident lymphovascular invasion that may
escape the immune surveillance. Although suppression of the
immunoreactivity has been observed (40)
, there is little
description on the interaction between immune defense and disease
status of ESCC patients.
A study by Jablonska et al. (41)
has
demonstrated a significantly higher serum sIL-2R
level in ESCC
patients than in control groups. Because sIL-2R
can potentially bind
to IL-2, high sIL-2R
levels in cancer patients may therefore
contribute as a poor prognostic factor to decrease IL-2-mediated
immunoactivities of lymphocytes. It has been suggested that the
sIL-2R
level be useful for prognosis estimation and for monitoring
disease progression. According to our findings, the serum sIL-2R
level not only increased substantially in ESCC patients but also
correlated well with TNM factors and tumor stage. High serum levels of
sIL-2R
at diagnosis may imply higher a relapse rate and shorter
survival. However, our results did not demonstrate any correlation of
serum sIL-2R
level with histopathological grade or lymphovascular
invasion.
As noted previously, binding of IL-2 can promote proliferation of
immune cells and biosynthesis of IL-2R. Immune cells can then secrete
sIL-2R
to elevate the serum sIL-2R
level, consequently considered
as a signal for lymphocyte activation. Nonetheless, host immune
response can also be negatively modulated by sIL-2R (16)
.
In fact, an adequate balance of lymphocyte activation is critical in
maintaining homeostasis between responses to foreign antigens and
tolerance to self-antigens (42
, 43)
. Elegant in
vitro studies of lymphocyte inactivation further support such
concept by showing that the profound defect of cellular immunity in
patients with advanced cancer may be attributable to the serum factor
from cancer patients (44
, 45)
. In addition to activated
lymphocytes, increased IL-2R
gene expression can be found in many
different types of human cancer cells (18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31
, 46, 47, 48)
.
IL-2R expression on cancer cells seems to play a role in tumor growth
(46
, 47)
. Although the autocrine tumor proliferation is
not observed consistently (48)
, it provides a focus for
future studies to elucidate the mechanism by which expression of
sIL-2R
may be regulated pathophysiologically. The impact of
sIL-2R
on tumor progression, nevertheless, remains to be clarified
if this is the basis for tumor evasion of host immune surveillance.
Tumor progression is a concerted process including evasion of host
immune surveillance, tumor cell proliferation, killing of the immune
cell, and the invasion of neighboring tissues as well as distant organs
(36)
. The present study demonstrates that the serum level
of sIL-2R
in ESCC patients is proportional to the tumor burden as
well as the disease progression. Expression of IL-2 receptors was
detected by IHC in the pathological sections of tumor specimens, and
among these specimens, the hybridized products of IL-2R
mRNA were
further identified by ISH. All patients with a high level of serum
sIL-2R
(>1500 pg/ml) were associated with the positive expression
of IL-2R
mRNA. In addition to activated T cells, cancer cells can be
an important source of elevated sIL-2R
in ESCC patients. This
elevated sIL-2R
level can in turn act as a prognostic serum
biomarker to assess the aggressiveness of ESCC.
 |
ACKNOWLEDGMENTS
|
|---|
We thank Jin-Ping Lin and Li-Ling Yang for excellent technical
assistance and Hua-Ping Kao for help in preparing the manuscript.
 |
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 Supported, in part, by Grant
NSC88-2314-B-075-082 from the National Science Council and by Grant
LF99 MD01 from the Lite-On Cultural Foundation. 
2 To whom requests for reprints should be
addressed, at Division of Thoracic Surgery, Department of Surgery,
Veterans General Hospital in Taipei, #201 Section 2, Shih-Pai Road,
Taipei 11217, Taiwan, Republic of China. Phone: 886-2-2875-7060; Fax:
886-2-873-1488; E-mail: lswang{at}vghtpe.gov.tw 
3 The abbreviations used are: ESCC, esophageal
squamous cell carcinoma; TNM, Tumor-Node-Metastasis; IL, interleukin;
IL-2R, IL-2 receptor; sIL-2R
, soluble IL-2R
; IHC,
immunohistochemistry; ISH, in situ hybridization. 
Received 5/12/99;
revised 1/ 3/00;
accepted 1/ 6/00.
 |
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