PBK/TOPK in the differential diagnosis of
cholangiocarcinoma from hepatocellular carcinoma and its
involvement in prognosis of human cholangiocarcinoma
Furong He, Qingguo Yan, Linni Fan, Yixiong Liu, Jihong Cui, Juanhong Wang,
Lu Wang, Yingmei Wang, Zhe Wang, Ying Guo, Gaosheng Huang⁎
State Key Laboratory of Cancer Biology, Department of Pathology, Xijing Hospital, Fourth Military Medical University,
Xi'an 710032, China
Received 24 February 2009; revised 15 May 2009; accepted 21 May 2009
Summary The increased expression of PDZ binding kinase/lymphokine-activated killer T-cell–
originated protein kinase (PBK/TOPK) is associated with some human malignant tumors. In this study,
we analyzed PBK/TOPK expression in hepatic primary tumor and explored its role in cholangiocarci-
noma biology. Seventy-four cholangiocarcinomas, 33 hepatocellular carcinomas, and 10 normal liver
tissues were prepared from paraffin-embedded specimens. PBK/TOPK protein was assessed by
immunohistochemical staining, and the survival time was analyzed with the Kaplan-Meier method. The
protein, mRNA of PBK/TOPK, and cell cycle of cholangiocarcinoma cell line after PBK/TOPK
suppression with small interfere RNA were studied by Western blot, semiquantitative reverse
transcriptase–polymerase chain reaction, and flow cytometry, respectively. PBK/TOPK was usually
expressed in normal bile duct epithelial cells and much more frequently expressed in cholangiocarci-
noma (68/74) but never expressed in hepatocytes and hepatocellular carcinomas (0/33). PBK/TOPK
down-regulation was related to the poor prognosis of patients with cholangiocarcinoma (P = .013).
Epidermal growth factor can enhance PBK/TOPK expression in cholangiocarcinoma QBC 939 cells,
but suppression of PBK/TOPK in the cells did not affect their proliferation. PBK/TOPK protein could
serve as a useful indicator for histopathologic differentiation between cholangiocarcinoma and
hepatocellular carcinomas and the low expression of PBK/TOPK is predicative of poor survival in
© 2010 Elsevier Inc. All rights reserved.
PDZ binding kinase/lymphokine-activated killer T-cell–
originated protein kinase (PBK/TOPK) is a 322 amino acid
mitotic protein kinase and a member of the MEK protein
family. It is reported that PBK/TOPK can phosphorylate p38
and is suggested to be a novel MEK3/6-related mitogen-
normal tissue except the testis, but it is overexpressed in
hematopoietic neoplasms, including Burkitt's lymphoma,
acutelymphoblastic leukemia,multiplemyeloma andpromye-
locytic leukemia, and some cancers such as breast carcinoma
and colorectal cancer [3,4]. Although PBK/TOPK is closely
related to the above mentioned malignancies, its mechanism is
still unclear. It is reported that PBK/TOPK is involved in the
cytokinetic function and in DNA damage and repair [5,6]. In
E-mail address: email@example.com (G. Huang).
0046-8177/$ – see front matter © 2010 Elsevier Inc. All rights reserved.
Human Pathology (2010) 41, 415–424
be a molecular target for malignancy.
Cholangiocarcinoma (CC), a primary liver tumor that
arises from biliary epithelial cells, increases in incidence and
has poor prognosis. Unlike hepatocellular carcinoma (HCC),
no predisposing factors or high-risk populations have been
demonstrated for cholangiocarcinoma . Recent data show
that the incidence and mortality rates of intrahepatic CC
(ICC) increase in several areas around the world [8,9].
Timely diagnosis of cholangiocarcinoma is essential because
surgical resection in early disease remains the only cure.
Lack of a sensitive and specific early diagnostic marker as
well as alternative treatment is the main reason why patients
have limited survival time. The use of diverse approaches,
through which are analyzed the physiological or pathological
complement of proteins in cells, tissues, or biological fluids,
has received substantial interest in biomarker discovery for
In recent studies, PBK/TOPK mRNA has been detected at
low level in liver tissue , but PBK/TOPK protein and its
function have not been revealed in the liver. In our previous
normal and tumor tissues by using tissue chip assay and
immunohistochemical staining. We found that PBK/TOPK
was only expressed in normal bile duct cell and cholangio-
carcinoma, so we used many surgical specimens of cholan-
giocarcinoma and HCC to analyze PBK/TOPK expression
found, for the first time, that PBK/TOPK was only expressed
in cholangiocarcinoma tissues and its down-regulation was
significantly related to prognosis of the patients, which
suggested that PBK/TOPK could be used as an indicator for
preliminary study on the function of PBK/TOPK in
cholangiocarcinoma cell line has been performed.
2. Patients and methods
2.1. Patients and clinical samples
One hundred seven liver tumors and 10 normal liver
tissues (100 surgical specimens and 17 needle biopsies)
during 2003 to 2007 in Xijing Hospital were included in our
(including 17 needle biopsies), 33 HCCs, and 10 normalliver
tissues obtained from the donor livers. All the tissues were
retrieved from the consecutive patients of the pathology
archives in Xijing Hospital. These specimens came from 82
male patients and 35 female patients with a mean age of 60.5
years (range, 37-77 years). The final diagnoses of CCs and
radiological and laboratory data with consistent histology.
Two pathologists re-examined all the cases to confirm the
diagnoses. Demographic, operation, and survival data were
were approved by the Xijing Hospital Ethics Committee.
2.2. Immunohistochemical staining and evaluation
PBK/TOPK expression was studied by the same immu-
nohistochemical method as that employed in our previous
study . Proliferating cell labeling index (Ki67) was also
determined by immunohistochemistry . Rabbit poly-
clonal PBK/TOPK antibody (1:75 dilution, Cell Signaling
Technology, Danvers, MA, USA) and mouse monoclonal
antibodies against CK7, CK19, and Ki67 (for all these
antibodies, 1:50 dilution; Dako, Glostrup, Denmark) were
used in our experiment, respectively. The EnVision kit
(Dako) was taken as the second antibody. Negative controls
were performed by replacing the primary antibody with
normal mouse or rabbit serum (DAKO, Denmark).
The normal bile duct staining was used to set the score
intensity and Image-Pro Plus 4.5 software was used to analyze
the automatic definition of mean density and area thresholds,
which was used for visual counting of the immunostaining of
PBK/TOPK and Ki67 . PBK/TOPK expressions were
classified as high and low based on whether their scores were
the median value, we regarded them as high expression of
PBK/TOPK. On the other hand, when the scores were below
the median, low expression was determined.
2.3. Cell culture and treatment
Cholangiocarcinoma cell line QBC939  recognized
internationally was a gift from Professor Shuguang Wang in
Department of Hepatobiliary Surgery, Southwest Hospital,
the Third Military Medical University. The HepG2 (human
hepatoma) and MD231 (human breast cancer, as a positive
control of PBK/TOPK ) cell lines were obtained from the
American Type Culture Collection. The cell lines were
cultured in DMEM (Dulbecco's modified eagle medium)
supplemented with 10% fetal bovine serum and 1%
antibiotic/antimycotic solution at 37°C in atmosphere with
5% CO2. QBC939 cells were stimulated with epidermal
growth factor (EGF) (20 ng/mL) (Gibco, Pascagonla, MS,
USA). In order to avoid the confounding variable of serum-
induced signaling, the cells were serum-starved for 24 hours
before EGF treatment.
2.4. Semi-quantitative reverse transcriptase–
polymerase chain reaction
Total RNA was extracted from the cells by using the
TRIzol reagent (Invitrogen, Carlsbad, CA). The cDNA
template was prepared by using oligo(dT) random primers
416 F. He et al.
and reverse-transcripted as described previously . After
the reverse transcription, appropriate dilutions of each
single-stranded cDNA were prepared for subsequent PCR.
The PCR primer sequences for detecting PBK/TOPK were
5′-ATG GAA GGG ATC AGT AAT TTC-3′ and 5′-TCA
GAC ATC TGT TTC CAG AGC TTC-3′. As a quantitative
internal control, the glyceraldehyde-3-phosphate dehydro-
genase (GAPDH) was used to monitor the total RNA. The
primer sequences were 5′-TCG GAG TCA ACG GAT
TTG GTC GTA-3′and 5′-TGG CAT GGA CTG TGG
TCA TGA GTC-3′.
2.5. Western blot analysis
According to our group report , the proteins (50 μg
per lane) extracted from the cells were analyzed by 10%
sodium dodecyl sulfate–polyacrylamide gel electropheresis
gels and subsequently transferred onto a poly(vinylidene
fluoride) (PVFD) membrane (Millipore, Chelmsford, MA).
The antibody-bound proteins were detected by chemilu-
minescence (ECF, Amersham-Pharmacia Biotech, and
Piscataway, NJ). For PBK/TOPK and phospho-PBK/
TOPK (Thr9) (Rabbit polyclonal antibody; Cell Signaling
Technology) antibodies, 1:1000 dilutions were used for
Western blot analysis according to the instructions of
2.6. Gene-silencing effect by siRNA
The siRNA sequences (Product No.M-005390; Dharma-
con RNA Technologies, Lafayette, CO) for PBK/TOPK
gene (accession number NM_018492) were used in our
transfection experiments. Human cholangiocarcinoma cell
line QBC939 cells were split 1 day before transfection, and
siRNA were transfected into the cells at 50% to 60% by
using Lipofectamine 2000 reagent (Invitrogen) according to
the instruction. A nonspecific siRNA control (Product No.d-
001206-13-05 sicontrol Non-Targeting siRNA pool #1;
Dharmacon RNA Technologies) and the untransfected cells
were used as two negative controls. The transfected cells
were harvested 72 hours after transfection for analyzing, the
cell cycle and the protein expression.
2.7. Cell cycle analysis by Flow Cytometry
The cell cycle was analyzed by flow cytometry (ELITE
ESP, Beckman-Coulter, Fullerton, CA, USA). The cells
were trypsinized and centrifuged for 5 min, 1000 rpm. The
pellet was resuspended in cold phosphate-buffered saline
and kept on ice for 5 min before analysis by fluorescence-
activated cell sorting. Np-40 and Propidium Iodide (Sigma)
were added at a final concentration of 0.1% and 50 mg/mL,
respectively. DNA content was measured in the Fl2 channel
of a fluorescence-activated cell sorting station by using cell
2.8. Statistical analysis
Statistical analysis was performed by using SPSS
software (version 10.0, SPSS Inc, Chicago, IL). The
relationship between PBK/TOPK immunoreactivity and
clinicopathological parameters was analyzed by Spearman's
test, and Kaplan-Meier method was used for survival
analysis. The survival time between low and high expres-
sions was compared by using the log-rank test. For
multivariate analysis, the COX regression model was used.
All tests were 2-sided. A P value of .05 was considered to be
3.1. Clinical data and histopathology
Human cholangiocarcinoma specimens were composed
of 51 cases of ICC (34 surgical specimens and 17 needle
biopsies) and 23 cases of hilar CC. All the HCC cases were
surgical specimens and the normal liver tissues were
obtained from the donor livers. Histological grading of
cholangiocarcinoma was assessed based on the World Health
Organization Classification of Tumors . In 57 cases of
the cholangiocarcinoma specimens, 39 cases were well or
intermediately differentiated (Fig. 1A and B), and 18 were
poorly differentiated (Fig. 1C). The diagnosis of HCC was in
accordance with the World Health Organization Criteria
. Among the patients with HCC, cirrhotic liver tissues
around the tumors were found in 21 cases. All the normal
liver tissues showed normal morphology.
3.2. Immunohistochemical staining
Complete staining data with PBK/TOPK antibody were
obtained from 117 patients. The pattern of PBK/TOPK
staining was usually cytoplasmic, and the pattern of a few
specimens was only on the membrane. If none or less than
10% of the tumor cells showed specific PBK/TOPK staining,
the case was classified as negative.
In normal liver, it was found that PBK/TOPK protein was
ubiquitously expressed in normal bile ducts (Fig. 2A),
including all the small and large intrahepatic bile ducts. It
was highly expressed in the reactive bile duct of cirrhosis
liver (Fig. 2B). However, normal hepatocytes were totally
negative for PBK/TOPK (Fig. 2A, B). Statistically, PBK/
TOPK expression between normal bile duct cell and
hepatocyte was significantly different (P b .001).
Most cases of cholangiocarcinoma tissues (68/74) were
positive for PBK/TOPK immunostaining while the adjacent
normal liver cells were negative (Fig. 2D). A significant
correlation between PBK/TOPK expression and histopatho-
logical tumor grading was not found (P = .67) (Fig. 1).
Meanwhile, 33 HCC samples were totally negative for PBK/
417PBK/TOPK in the differential diagnosis of cholangiocarcinoma
TOPK immunostaining (Fig. 2C). Statistically, PBK/TOPK-
positive rates between CC group (68/74,91.9%) and HCC
group (0/33) were significantly different (P b .001). In
addition, 11 samples (33.3%) expressed CK7 of 33 HCC
cases and 5 cases (15.1%) were CK19 positive, and the
or CK19-positive rate (33.3% or 15.1% ) was significant (P b
.001 for both). In 74 cases of cholangiocarcinoma, CK7 was
Poorly differentiated CC. No correlation was found between PBK/TOPK expression and tumor grade differentiation.
PBK/TOPK expression in cholangiocarcinoma tissues of 3 grades. (A) Well-differentiated CC. (B) Moderately differentiated CC. (C)
418 F. He et al.
expressed in 72 cases. However, a significant difference
between PBK/TOPK positive rate (68/74) and CK7 (72/74)
positive rate was not found (P = .275).
As most PBK/TOPK-positive cells were all PCNA-
positive in neurons system , it was necessary to know
if there was a correlation between PBK/TOPK expression
and cell proliferation in this study. Interestingly, normal
bile duct epithelial cells were strongly positive for PBK/
TOPK immunostaining, but Ki67 was negative (Fig. 3A).
On the other hand, although Ki67 was highly expressed in
cholangiocarcinoma tissues (80% cells were Ki67 posi-
tive), PBK/TOPK expression was much weaker or even
negative (Fig. 3B). In short, there was no significant
correlation between Ki67 index and PBK/TOPK expres-
sion (P = .169).
3.3. PBK/TOPK expression in cholangiocarcinoma
cells after EGF stimulation
Since PBK/TOPK was much more frequently expressed
in the specimens of cholangiocarcinoma, we turned our
attention to the study on the function of PBK/TOPK in the
cholangiocarcinoma cell line. First of all, we detected PBK/
TOPK protein in the cholangiocarcinoma QBC939 cell line
by Western blot. MD231 cells were taken as the positive
control for detecting PBK/TOPK protein. PBK/TOPK
protein was detected in the QBC939 cell line, but very
low level was found in HepG2 cells (Fig. 4A). As PBK/
TOPK could be induced by EGF  and expression of EGF
receptor increased in human cholangiocarcinoma , we
explored whether EGF could induce PBK/TOPK expres-
sion in the cholangiocarcinoma cell line. After stimulation
of EGF (20 ng/ml) for about 2 hours, PBK/TOPK mRNA
in QBC939 cells began to increase (Fig. 4B) and an
increase of the protein followed (Fig. 4C). But after
stimulation with EGF for about 30 minutes, the level of
phosphorylated PBK/TOPK in QBC939 cells remained
stable (Fig. 4D).
We explored whether PBK/TOPK expression was
essential for cell cycle progress in cholangiocarcinoma
cells. The QBC 939 cell line was transfected with the
siRNA oligonucletides which decreased PBK/TOPK
nonneoplastic H and HCC are negative. A, Normal liver tissue. B, Cirrhotic liver tissue. C, HCC. D, CC. Abbreviations: H, hepatocyte; B, bile
duct; RB, reactive bile duct.
Representative examples of positive and negative immunostaining for PBK/TOPK. The B, RB, and CC are positive, but the
419PBK/TOPK in the differential diagnosis of cholangiocarcinoma
expression compared with the negative control (Fig. 4E).
No significant difference in the cell population in the S
and G1 phases was observed between PBK/TOPK
suppressed cells and the negative control, while a minor
G2 phase delay was found in these cells after PBK/TOPK
suppression (Fig. 4E). These data indicated that suppres-
sion of PBK/TOPK did not affect the proliferation of
3.4. The Prognosis of cholangiocarcinoma patients
and PBK/TOPK expression
Twenty-four patients with cholangiocarcinoma were
followed up for survival analysis by Kaplan-Meier method
and the follow-up period was calculated from the date of
surgery until March 31, 2008. Only deaths from cholan-
giocarcinoma were considered in this study. At the end of
the follow-up period, 19 patients died of the disease and 5
were alive. The median survival time was 8 months for 13
patients with low expression of PBK/TOPK and 14 months
for 11 patients with high expression of PBK/TOPK as
shown in Table 1. It indicated that low expression of PBK/
TOPK was predictive of poor survival of the patients with
cholangiocarcinoma (P = .013). It was also found that the
median survival time for the patients with well differenti-
ated cholangiocarcinoma was 14 months while 8 months
for patients with poorly differentiated cholangiocarcinoma
(P = .011). It was interesting to note that the median
survival time for female patients was 17 months but only
8 months for male patients with cholangiocarcinoma (P =
.007, Table 1). The Kaplan–Meier survival curve for the
patients with cholangiocarcinoma is shown in Fig. 5. To
clarify the independent prognostic value of the PBK/TOPK
expression in the patients with cholangiocarcinoma, a
multivariate analysis of the relevant parameters was
performed. The COX regression analysis revealed that
bile duct is PBK/TOPK strongly positive (left) but Ki67-negative. B, PBK/TOPK is negative, while Ki67 positive.
PBK/TOPK and Ki67 immunostainings in a representative case of cholangiocarcinoma with heterogeneous morphology. A, Normal
420 F. He et al.
PBK/TOPK expression (P = .049) and the gender (P =
.025) were independent prognostic factors for overall
survival (Table 1).
Cholangiocarcinoma is the second most frequent primary
malignant epithelial liver tumor . In addition, intrahepatic
cholangiocarcinoma is increasing worldwide [9,21]. The
diagnosis, poor prognosis, evaluation and management of
these tumors are still challenges [22,23] and molecular
mechanisms underlying the development, growth and metas-
tasis in biliary tract cancer are still unclear. The worldwide
increase in incidence, mortality and poor prognosis of
cholangiocarcinoma impel us to make a more complete
recognition of the molecular pathology of bile duct cancer.
In our study, we found for the first time that PBK/TOPK
was expressed not only in bile ducts, especially in reactive
proliferative bile ducts of all cases, but also in most
cholangiocarcinoma cases (68/74). In contrast to cholangio-
carcinoma and bile duct cell, neither HCC nor nonneoplastic
hepatocyte expressed PBK/TOPK proteins. The absence of
PBK/TOPK protein in nonneoplastic liver tissue was
consistent with the previous report that the mRNA of PBK/
TOPK was detected at a low level in normal adult liver tissue
determined by Northern blot analysis, but the mRNA of
PBK/TOPK could not tell whether PBK/TOPK expression
was from hepatocyte or bile duct cells. Furthermore, as PBK/
TOPK was detected at a very low level in HepG2 cell line,
the human hepatoma cells, by Western blot analysis; it was
lines were analyzed by Western blot using antibodies against PBK and actin (loading control). A, PBK/TOPK expression in QBC939, MD231,
and HepG2 cell lines. B, PBK/TOPK mRNA in cholangiocarcinoma cells starved for 24 h before stimulation with 20 ng/ml EGF for the
indicated times. C, PBK/TOPK protein increased in cholangiocarcinoma cell in the same condition as in B. D, After stimulation with EGF, the
level of phosphorylated PBK/TOPK in QBC939 cells remained stable. E, The cell lines transfected with siRNA of PBK/TOPK or negative
control siRNA. The cell lines were cultured in complete media and harvested at the time of 72 hours after the transfection. No significant
difference was observed in the cell cycle profiles between PBK/TOPK-suppressed QBC 939 cells and controls; however, a minor G2 phase
delay was found.
Analysis of PBK/TOPK protein in QBC939, MD231, HepG2, and siRNA transfected QBC939 cell lines. Total lysates of the cell
421 PBK/TOPK in the differential diagnosis of cholangiocarcinoma
quite possible that PBK/TOPK protein in HCC tissues was
too low to be detected by immunohistochemical analysis.
As PBK/TOPK was mainly expressed in bile duct cells
and cholangiocarcinoma, it suggests that PBK/TOPK
protein could be a useful indicator for making the
differential diagnosis of cholangiocarcinoma from HCC.
Sometimes, it is difficult to differentiate CC from HCC with
the exhibition of pseudoglandular or poorly differentiated
morphology  because a minority of HCC is variable in
appearance and confused with ICC. Although it is believed
that CK7/CK19 immunostaining in liver as biliary differen-
tiation markers could distinguish HCC from ICC, a series of
studies demonstrate that CK7 and /or CK19 are/is expressed
in 28% to 50% of HCC [25-27]. In accordance with the
results of the above mentioned studies, of 33 cases of HCC
in our study, 11 (33.3%) expressed the biliary differentiation
markers but none of them expressed PBK/TOPK protein. It
suggested that PBK/TOPK was more specific than CK7 or
CK19 in differentiating CC from HCC. As it was reported
that Hep Par 1 was expressed confined primarily to benign
and malignant hepatocytes and was sensitive and specific for
HCC , we proposed that the combination of PBK/TOPK
and Hep Par 1 could help the differentiation between CC
We have learned from the previous studies that PBK/
TOPK is overexpressed in highly proliferating tumors ,
such as breast carcinoma, colorectal carcinoma and malig-
nant haematopoietic disorder [3,4,29], so it is believed that
PBK/TOPK plays an important role in carcinogenesis,whose
key role is related to cell proliferation [4,5]. In addition,
PBK/TOPK is localized in neural progenitor cells undergo-
ing active proliferation in normal tissue . So, it seems
that PBK/TOPK plays a role in cell proliferation. However,
our study demonstrates that PBK/TOPK immunostaining is
not related to Ki67 labeling in both bile duct epithelial cells
and cholangiocarcinoma cells. It is not related to the
differentiation of cholangiocarcinoma, either. Furthermore,
the suppression of PBK/TOPK by siRNA does not affect the
proliferation of the QBC939 cell line, which is consistent
with the results in the MCF 10 cell line . Therefore, we
may draw a conclusion from our study that PBK/TOPK
should not be a key protein to cell proliferation in
cholangiocarcinoma and bile duct cells and it may have
more functions in bile duct epithelial cells and cholangio-
carcinoma besides proliferation.
Similar to previous results , we found that PBK/TOPK
mRNA and protein increased in cholangiocarcinoma cells
after EGF stimulation. It indicated that EGF could stimulate
the transcription and/or translation of PBK/TOPK. As PBK/
TOPK expression can be regulated by transcription factors
E2F and CREB/ATF , we speculate that the growth
factor may increase total PBK/TOPK protein expression
through activating the transcription factors. But stimulation
of EGF did not increase the level of phosphor-PBK/TOPK
cholangiocarcinoma with low and high levels of PBK/TOPK
expression (n = 24. P = .013). B, Kaplan-Meier survival analysis for
the female patients of cholangiocarcinoma compared with the male
patients (n = 24. P = .007).
A, Kaplan-Meier survival analysis for the patients of
Prognostic variable for survival in 24 patients with
VariableN Median survival
15 11.00 (2.23-19.77)
9 13 (8.59-17.41)
8 14 (11.97-16.03) .0113
14 (12.64-15.36) .0129
422 F. He et al.
protein in QBC939 cells. Moreover, previous studies have
demonstrated that rat hepatocytes could transdifferentiate
into biliary epithelium when they were stimulated with EGF
 and it indicated that EGF was an important component
for facilitation of bile ductal morphogenesis . In addition,
as EGF receptor expression was found in bile duct , we
speculate that the EGF/PBK/TOPK pathway may be
responsible for retaining the phenotype of normal biliary
epithelium, in which PBK/TOPK was frequently expressed.
Total level of PBK/TOPK could be induced by EGF in
cholangiocarcinoma cells, but the level of active PBK/TOPK
did not increase. Therefore, we infer that the activation of
PBK/TOPK induction by EGF was probably defective in
One important issue in oncology study is whether any
potential biomarkers are useful in predicting patient
prognosis. In our present study, we have found for the first
time that PBK/TOPK expression is significantly related to
prognosis of the patients with cholangiocarcinoma by
Kaplan-Meier analysis. PBK/TOPK down-regulation is
significantly associated with poor prognosis in patients
with cholangiocarcinoma. In addition, women undergoing
surgical resection for cholangiocarcinoma show much better
prognosis than male patients. The same is true of the cases in
lung cancer studies reported recently . Based on the
results of our study and others' research, female hormones
may have some antitumor function.
In sum, as PBK/TOPK immunostaining can help to make
differential diagnosis of cholangiocarcinoma from HCC and
its down-regulation is significantly associated with poor
prognosis in patients with cholangiocarcinoma, we conclude
that it could serve as a useful indicator for predicting survival
of patients with cholangiocarcinoma. However, the exact
biologic function of PBK/TOPK in both normal bile duct
epithelial cells and in cholangiocarcinoma cells needs to be
further investigated in the future.
We are very grateful to Professor Yumei Zhou and
Donglei Jiang (Department of Foreign Languages, Fourth
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