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Molecular Oncology, Markers, Clinical Correlates |
Departments of Urology and Cancer Biology [K. I., J. W. S., P. S., C. P. N. D.] and Genitourinary Medical Oncology [R. M.], The University of Texas M. D. Anderson Cancer Center, Houston, Texas 77030, and Department of Urology, Kochi Medical School, Kochi, Japan [K. I., T. K., C. Y., T. S.]
| ABSTRACT |
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| INTRODUCTION |
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54,000 patients and results in 12,000
deaths. The standard treatment for operable invasive bladder cancer is
surgery, whereas systemic chemotherapy is the only viable therapeutic
option for patients with distant metastasis (2, 3, 4, 5)
.
Although radical cystectomy will cure a substantial fraction of
patients with minimally invasive TCC, many patients with deeply
muscle-invasive or extravesical disease treated by radical cystectomy
alone die of metastatic TCC (6)
. For this reason, patients
at the Kochi Medical School with muscle-invasive TCC are currently
uniformly treated with neoadjuvant M-VAC chemotherapy followed by
radical cystectomy. Despite this aggressive approach, some patients
still relapse, and nearly all of these will die of metastatic disease
that is resistant to conventional chemotherapy. Therefore, it is
important to identify prognostic markers that predict for disease
recurrence so that we can design and implement more effective
therapeutic strategies. It is well established that tumor growth and metastasis depend upon the induction of a blood supply (7) . This process of angiogenesis is regulated within a complex homeostasis by the balance between proangiogenic and antiangiogenic signals. Some proangiogenic factors including bFGF (8 , 9) , VEGF (10 , 11) , and IL-8 (12) are produced by tumors growing in their relevant microenvironment. Previous studies of bladder cancer have shown that high MVD is predictive of early disease progression for patients with muscle-invasive TCC (13 , 14) but not superficial papillary bladder cancer (15) . Overexpression of bFGF (8 , 9) and VEGF (10 , 11) has been identified in tissue, serum, and urine of patients with bladder cancer and correlates with disease recurrence. IL-8 (16) has also been shown to be proangiogenic and to promote invasion and metastasis of human TCC (17) .
We evaluated MVD and the expression of bFGF, VEGF, and IL-8 in patients with muscle-invasive TCC before and after treatment with neoadjuvant M-VAC and radical cystectomy and then correlated clinical outcome with expression of these factors. We found that MVD and overexpression of VEGF prior to therapy correlated with an increased risk of metastatic disease. After M-VAC, MVD and overexpression of bFGF identified high-risk patients. In this exploratory study, expression of these proangiogenic factors was more significant than stage (either clinical stage before therapy or the pathological stage after M-VAC) for predicting disease recurrence.
| MATERIALS AND METHODS |
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In Situ mRNA Hybridization Analysis.
For ISH analysis, specific antisense oligonucleotide DNA probes for
IL-8 (16)
, bFGF (19)
, and VEGF
(20)
were prepared. These were designed to be
complementary to the mRNA transcripts based on published reports of the
cDNA sequence, as described previously. The specificity of the
oligonucleotide sequence was initially determined by a Gene Bank
European Molecular Biology Library database search with the use of the
Genetics Computer Group sequence analysis program (GCG, Madison, WI)
based on the FastA algorithm; these sequences showed 100% homology
with the target gene and minimal homology with nonspecific mammalian
gene sequences. The specificity of each sequence was also confirmed by
Northern blot analysis (21)
. A
poly(dT)20 oligonucleotide was used to verify the
integrity and lack of degradation of mRNA in each sample. All DNA
probes were synthesized with six biotin molecules (hyperbiotinylated)
at the 3' end via direct coupling, with the use of standard
phosphormidine chemistry (Research Genetics, Huntsville, AL). The
lyophilized probes were reconstituted using a stock solution to 1
µg/µl in 10 mmol/L Tris (pH 7.6) and 1 mmol/L EDTA. Immediately
before use, the stock solution was diluted with probe diluent (Research
Genetics).
In situ mRNA hybridization was performed as described previously with minor modifications (22 , 23) . ISH was performed using the Microprobe Manual Staining System (Fisher Scientific, Pittsburgh, PA; Ref. 24 ). Tissue sections (4 µm) of formalin-fixed, paraffin-embedded specimens were mounted on silane-treated ProbeOn slides (Fisher Scientific; Refs. 22 and 23 ). The slides were placed in the Microprobe slide holder, dewaxed, and rehydrated with Autodewaxer and Autoalcohol (Research Genetics), followed by enzymatic digestion with pepsin. Hybridization of the probe was performed for 45 min at 45°C, and the samples were then washed three times with 2x SSC for 2 min at 45°C. The samples were incubated with alkaline phosphatase-labeled avidin for 30 min at 45°C, rinsed in 50 mM Tris buffer (pH 7.6), rinsed with alkaline phosphatase enhancer for 1 min, and incubated with fresh chromogen substrate for 15 min at 45°C. If necessary, samples were incubated a second time with fresh chromogen to enhance a weak reaction. Complementary mRNA in the sample leads to a red stain in this assay. Control for endogenous alkaline phosphatase included treatment of the sample in the absence of the biotinylated probe and the use of chromogen alone. Four cases of normal urothelium were used as reference material to which all of the tumor samples were referenced.
Quantification of Color Reaction.
Stained sections were examined in a Zeiss photomicroscope (Carl Zeiss,
Inc., Thomwood, NY) equipped with a three-chip charged-coupled device
color camera (model DXC-960 MD; Sony Corp., Tokyo, Japan). The images
were analyzed using the Optimas image analysis software (version 6.2;
Media Cybernetics, Silver Spring, MD). The slides were prescreened by
one of us to determine the range in staining intensity of the slides to
be analyzed. Images covering the range of staining intensities were
captured electronically, a color bar (montage) was created, and a
threshold value was set in the red, green, and blue modes of the color
camera. All subsequent images were quantified based on this threshold.
The integrated absorbance of the selected fields was determined by the
mean log inverse gray scale values multiplied by the area of the field.
The samples were not counterstained; therefore, the absorbance was
attributable solely to the product of the ISH reaction. For each
section, we determined the absorbance in several 2 x 2-mm zones
located at the periphery of the tumor. Five different fields within
each 2 x 2-mm zone were quantified, and an average value was
determined (24
, 25)
. The intensity of staining was
recorded as a ratio of the observed intensity to the intensity of the
integrated absorbance of poly(dT)20 in the same
sections, and this ratio was then normalized by comparison with the
integrated absorbance of a reference set of normal urothelium stained
simultaneously with the tumor section according to the following
equation: (A/B)/C/D x 100, where
A is the absorbance of the gene expression in the
tumor specimen, B is the absorbance of
poly(dT)20 expression in the tumor specimen,
C is the absorbance of the gene expression in the normal
urothelium, and D is the absorbance of
poly(dT)20 expression in normal urothelium. An
example of ISH and relative gene expression is shown in Fig. 1
.
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Quantification of MVD.
MVD was determined by light microscopy after sections were
immunostained with anti-CD34 antibodies according to the procedure
described by Weidner et al. (27)
. Clusters of
stained endothelial cells distinct from adjacent microvessels, tumor
cells, or other stromal cells were counted as one microvessel. Tissue
images were recorded using a cooled CCD Optotronics Tec 470 camera
(Optotronics Engineering, Goletha, CA) linked to a computer and digital
printer (Sony Corp.). The MVD was expressed as the average count of the
five areas with the highest MVD identified within a single x100 field.
An example of CD34 immunostaining in a representative metastatic tumor
and nonmetastatic tumor is shown in Fig. 2
.
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| RESULTS |
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Pretreatment Biopsy Specimens.
The Kaplan-Meier disease-free survival curve by clinical stage is shown
in Fig. 3
A. Clinical stage (organ confined versus
extravesical, two-sided, P = 0.062) approached
significance as a prognostic factor for disease-free survival, whereas
disease-free survival was independent of grade (data not shown). The
expression of bFGF, VEGF, and IL-8 mRNA as revealed by ISH was
evaluated in relation to anti-CD34 immunostaining results. The
expression of bFGF in the biopsy specimens was correlated with MVD
(P = 0.03), whereas there was no significant
correlation between the expression of VEGF or IL-8 and MVD (Fig. 4)
. Nine of 51 patients (19%) were rendered pT0
after M-VAC and transurethral resection. VEGF expression was
significantly lower in the biopsy specimens of these 9 patients than in
those with persistent tumor (P < 0.05).
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140% of the expression in normal
urothelium) and MVD (
30 per x100 field) in the biopsy specimens were
correlated with recurrence (P = 0.032 and
P = 0.015, respectively). Expression of bFGF and IL-8
were not significant prognostic factors for disease recurrence.
Univariate analysis by Cox proportional hazards model confirmed that
pretherapy VEGF expression and MVD were significant predictors for
disease progression (P = 0.010 and P =
0.023, respectively; Table 1A
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pT3, Nx) after chemotherapy had a
significantly worse survival rate than did patients with organ-confined
or no residual disease (P = 0.0038). The survival of
five patients with lymph node metastasis detected at pelvic lymph node
dissection was not significantly different from the survival of
patients with extravesical disease without metastasis, although the
numbers are too small to make a meaningful comparison. To determine
whether we could further stratify prognosis for patients with residual
disease, the prognostic significance of angiogenesis factor expression
and MVD was evaluated in the cystectomy specimens of patients with
residual cancer using log-rank analysis. The median MVD was 32 (range,
1274) vessels per x100 field. Using median values as the cutoff for
high and low expressions, high expression of bFGF (>200% of
expression by normal urothelium) and high MVD (
32 per x100 field)
were both significant predictors for disease progression
(P = 0.025 and P = 0.0091,
respectively; Fig. 5
pT3, Nx), bFGF, and MVD were all
significantly correlated with disease recurrence, whereas upon
multivariate analysis, bFGF expression in cystectomy specimens was the
strongest predictor (P = 0.008) of recurrence after
neoadjuvant chemotherapy and cystectomy, even more so than posttherapy
pathological stage (Table 1B)
Effect of Systemic Chemotherapy on Angiogenesis Factor
Expression.
Corresponding pretherapy and postchemotherapy specimens were available
from 31 patients. Table 2
shows that the median expression of both VEGF and bFGF was higher in
the postchemotherapy cystectomy specimens than in the pretherapy
biopsy, whereas IL-8 expression and MVD were similar in both.
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| DISCUSSION |
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Angiogenesis is regulated by the balance between stimulatory and inhibitory factors released by the tumor and its microenvironment (34 , 35) . Overexpression of proangiogenic factors by tumor cells is one mechanism by which tumors promote neovascularity. Overexpression of angiogenic factors bFGF (8 , 9) and VEGF (10 , 11 , 35 , 36) has been identified in the tissue, serum, and urine of patients with invasive bladder cancer and has also been associated with disease progression. Overexpression of VEGF is also associated with the altered expression of p53 (36) , which is a significant predictor of progression in patients with both superficial and muscle-invasive bladder cancer (37, 38, 39, 40, 41) . Our results showed that VEGF is a stronger predictor than MVD and clinical stage in predicting for recurrence in a group of patients with muscle-invasive TCC treated with neoadjuvant M-VAC prior to radical cystectomy. In a similar manner, bFGF overexpression within the residual tumors after neoadjuvant chemotherapy was predictive of disease progression and maintained independent prognostic significance when compared with advanced pathological stage (pT3, Nx). For this analysis, patients with pelvic lymph node metastasis (n = 5) were grouped with patients with extravesical disease, because their survival times were similar and there were too few patients with lymph node metastasis to analyze them independently. Given these limitations of this retrospective analysis, the expression of bFGF within the residual tumors from patients with muscle-invasive TCC after neoadjuvant M-VAC appears to be an independent prognostic factor for disease progression.
When we compared 31 matched sets of biopsy and cystectomy specimens, we found that bFGF and VEGF expression was higher in the residual tumor after M-VAC compared with the pretherapy biopsy, although only bFGF expression correlated with disease recurrence. Overexpression of bFGF by human bladder cancer cell lines is associated with resistance to cisplatin, possibly by protecting the tumor cells from cisplatininduced apoptosis (42 , 43) . Our observation of enhanced bFGF expression within residual tumors after cisplatin-based chemotherapy suggests that bladder cancer cells that overexpress bFGF selectively survive systemic chemotherapy, possibly secondary to resistance to cisplatin-induced apoptosis.
VEGF was also overexpressed within post M-VAC residual tumors compared with the pretherapy tumor biopsies. VEGF is a survival factor that protects both tumor and endothelial cells from exposure to environmental stresses such as hypoxia or acidosis (44 , 45) . Recent reports indicate that VEGF also protects tumor cells against chemotherapy-induced apoptosis (46) . Therefore, the relative overexpression of VEGF observed within the residual tumors after M-VAC may reflect the clonal selection resulting from the death of tumor cells expressing low levels of VEGF and the survival of tumor cells expressing relatively high levels of VEGF, which rendered them relatively resistant to chemotherapy-induced apoptosis.
IL-8 is a putative proangiogenic factor (16) , and in preclinical studies, we found that IL-8 expression regulates angiogenesis, tumorigenicity, and metastasis of human TCC (17) . However, in the current study, we did not detect any significance of IL-8 expression in the prognosis of these patients with TCC.
Herein, we report the results of an exploratory study evaluating the prognostic significance of proangiogenic markers for patients with muscle-invasive TCC treated with neoadjuvant M-VAC and radical cystectomy. The results are based upon a relatively small patient population, and yet we observed that increased expression of angiogenic factors and a high MVD were indicative of a poor prognosis for patients treated with chemotherapy and cystectomy. Clearly, these results from an exploratory study need to be confirmed in larger cohorts before these markers can be applied more generally for the clinical management of bladder cancer.
| FOOTNOTES |
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1 This work was supported by National Cancer
Institute Cancer Center Core Grant CA 16672 and by Grants CA 67914 and
CA 71861 from the NIH. ![]()
2 Both authors contributed equally to this
report. ![]()
3 To whom requests for reprints should be
addressed, at Department of Cancer Biology, Box 173, The University of
Texas M. D. Anderson Cancer Center, 1515 Holcombe Boulevard, Houston,
TX 77030. Phone: (713) 792-3250; Fax: (713) 792-8747; E-mail: cdinney{at}mdanderson.org ![]()
4 The abbreviations used are: TCC, transitional
cell carcinoma; bFGF, basic fibroblast growth factor; VEGF, vascular
endothelial cell growth factor; IL, interleukin; ISH, in
situ hybridization; IHC, immunohistochemistry; MVD, microvessel
density; M-VAC, methotrexate, vinblastine, doxorubicin, and
cisplatin. ![]()
Received 5/ 1/00; revised 8/31/00; accepted 8/31/00.
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