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Molecular Oncology, Markers, Clinical Correlates |
1 Department of Thoracic Surgery, Kyoto University, Faculty of Medicine, Kyoto; 2 Second Department of Surgery, Faculty of Medicine, Kagawa University, Kita-gun; 3 Department of Translational Clinical Oncology, Graduate School of Medicine, Kyoto University, Kyoto; and 4 Department of Thoracic Surgery, Seishin-Iryo Center Hospital, Kobe, Japan
| ABSTRACT |
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Experimental Design: We conducted a retrospective study on MMP-2 and MMP-9 expression as evaluated immunohistochemically in a total of 218 consecutive patients with completely resected pathological stage IIIIA, NSCLC.
Results: Strong MMP-2 expression in tumor cells and stromal fibroblasts were documented in 54 (24.8%) and 132 (60.6%) patients, respectively. Strong MMP-2 expression in stromal fibroblasts was more frequently seen in squamous cell carcinoma (72.7%) than in adenocarcinoma (54.9%; P = 0.016). Tumors showing strong MMP-2 expression in stromal fibroblasts showed a significantly higher intratumoral microvessel density (IMVD) than weak stromal MMP-2 tumors (mean intratumoral microvessel density, 50.9 versus 32.4, P = 0.003). In addition, postoperative prognosis of strong stromal MMP-2 patients was significantly poorer than that of weak stromal MMP-2 patients (5-year survival rate, 77.5 versus 60.2%, P = 0.032), and the prognostic significance was enhanced in squamous cell carcinoma patients but disappeared in adenocarcinoma patients. Multivariate analyses confirmed that strong stromal MMP-2 expression was a significant factor to predict a poor prognosis in squamous cell carcinoma patients, not in adenocarcinoma patients. In contrast, MMP-2 or MMP-9 status in tumor cells was not a significant prognostic factor.
Conclusions: MMP-2 status in stromal fibroblasts, not in tumor cells, was a significant prognostic factor associated with angiogenesis in NSCLC.
| INTRODUCTION |
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80% of primary lung cancer (1)
. Therefore, it is necessary to establish clinical markers, other than the tumor-node-metastasis staging system, that may predict the prognosis and response toward a specific therapy. Although experimental studies have revealed many biological markers that may be correlated with development and progression of malignant tumors, including NSCLC, no biological markers have been established as a clinical marker in the diagnosis or therapy (2)
. Recent experimental studies have revealed that degradation of the extracellular matrix (ECM) by matrix metalloproteinases (MMPs) is a critical process in progression of malignant tumors, including NSCLC, because degradation of the ECM is required in tumor angiogenesis, as well as tumor invasion and metastases (3, 4, 5, 6, 7) . Among many MMPs that have been identified, MMP-2 (Gelatinase-A) and MMP-9 (Gelatinase-B) are thought to be key enzymes as they degrade type IV collagen, the main component of ECM (6 , 7) . After these experimental studies, many clinical studies on MMP-2 and/or MMP-9 expression in malignant tumors, including NSCLC, have been conducted (8, 9, 10, 11, 12, 13) , but the clinical significance remains controversial (6) . In addition, in most clinical studies, MMP expression only in tumor cells was assessed, whereas experimental studies have revealed that stromal tumor cells as well as tumor cells do express MMPs, especially MMP-2, and stromal fibroblast expression MMP-2 plays an important role in tumor progression (6 , 14) . Thus, we conducted a large-scale clinical study on MMP-2 and MMP-9 expression in tumor cells and in stromal fibroblasts as evaluated immunohistochemically to clarify the clinical significance in resected NSCLC.
| PATIENTS AND METHODS |
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All primary tumor specimens were immediately fixed in 10% (v/v) formalin and then embedded in paraffin. Serial 4-µm sections were prepared from each sample and served for H&E staining, immunohistochemical staining, and the terminal deoxynucleotidyltransferase-mediated nick end labeling staining. Results of immunohistochemical staining and terminal deoxynucleotidyltransferase-mediated nick end labeling staining were evaluated by two authors independently (S. Ishikawa and F. Tanaka) without knowledge of any clinical data. In case of a discordant evaluation after reevaluation, the slides were evaluated by another author (K. Takenaka). This study has been approved by the Ethics Committee, Graduate School and Faculty of Medicine, Kyoto University.
Evaluation of MMP-2 and MMP-9 Expression.
Expression of MMP-2 and MMP-9 was assessed immunohistochemically using a standard streptavidin-biotinylated horseradish peroxidase complex method (LSAB+ kit/HRP; Dako, Kyoto, Japan). For antigen retrieval, sections were autoclaved at 121°C for 5 minutes in 0.01 mol/L citrate buffer (pH 6.0), and then sections were incubated in methanol containing 0.03% H2O2 (Nakalai Tesque, Kyoto, Japan) for 30 minutes. After incubation in a nonspecific staining blocking agent (BlockAce; Dainihon Seiyaku, Osaka, Japan), sections were incubated overnight at 4°C with each primary antibody as follows: an antihuman MMP-2 monoclonal antibody (mAb) (500 µg/mL mouse IgG1/
, F-68; Daiichi Fine Chemical Co. Ltd., Tokyo, Japan) diluted at 1/200 and an antihuman MMP-9 monoclonal antibody (500 µg/mL mouse IgG1/
, F-69; Daiichi Fine Chemical Co. Ltd.) diluted at 1/250. As a negative control, each section was treated without the primary antibody.
MMP-2 or MMP-9 expression in tumor cells and MMP-2 expression in stromal fibroblasts were classified according to the following grading system. MMP-9 expression in stromal cells was not assessed because the expression was negative or faint. A percentage score was defined as follows: score 0 if the percentage positive staining cells was
25%, score 1 if the percentage was >25 and
50%, and score 2 if the percentage was >50%; an intensity score was defined as follows: score 0 if no staining was documented, score 1 if the staining intensity was weak, score 2 if the intensity was moderate, and score 3 if the intensity was high. Each section was finally classified based on the sum of the percentage score and the intensity score as follows: weak expression when the sum was
3 and strong expression when the sum was 4 or 5.
Expression of vascular endothelial growth factor (VEGF) was also evaluated immunohistochemically as described previously (16 , 17) . Briefly, an anti-VEGF polyclonal antibody A-20 (200 µg/mL rabbit IgG; Santa Cruz Biotechnology, Santa Cruz, CA) diluted at 1/50 was used as the primary antibody. VEGF expression was also evaluated according to the same scoring system and was finally classified into weak or strong expression based on the score (16 , 17) .
Quantification of Angiogenesis [Intratumoral Microvessel Density (IMVD)].
IMVD, a measurement of tumor angiogenesis, was evaluated immunohistochemically as described in previous studies (16
, 17)
. Briefly, immunohistochemical staining for CD34 (a pan-endothelial marker) and CD 105 (a proliferation-related endothelial marker) to highlight endothelial cells was performed using a sensitive streptavidin-biotinylated horseradish peroxidase complex system (TSA-Indirect kit; NEN Life Science Products, Boston, MA). Primary antibodies used were an anti-CD34 mAb QBEnd10 (50 µg/mL mouse IgG1/
; Dako), diluted at 1/50, and an anti-CD105 mAb SN6 h (366 µg/mL mouse IgG1/
; Dako), diluted at 1/100. The 10 most vascular areas within a section were selected for evaluation of angiogenesis, and vessels labeled with the anti-CD34 mAb or the anti-CD105 mAb were counted under light microscopy with a 200-fold magnification. The average counts were recorded as theCD34-IMVD or CD105-IMVD for each case.
Evaluation of Cell Proliferation, Apoptotic Cell Death, and p53 Status.
Proliferative activity of tumor cells was evaluated by immunohistochemical staining using a mAb against proliferative cell nuclear antigen (clone PC-10, 400 µg/mL mouse IgG2a/
; Dako) as described previously (15)
. A total of 1000 tumor cells was counted for positive staining, and the proliferative activity was represented as the percentage of proliferative cell nuclear antigen-positive tumors cells.
The terminal deoxynucleotidyltransferase-mediated nick end labeling staining to detect apoptotic cells was performed using In Situ Death Detection kit POD (Boehringer Mannheim, Mannheim, Germany) as described previously (15) . In each case, a total of 10,000 tumor cells was evaluated, and apoptotic index was defined as the number of apoptotic cells per 1000 tumor cells.
Evaluation of p53 status was performed by immunohistochemical staining using an antihuman p53 mAb DO-7 (250 µg/mL mouse IgG2b/
; Dako) diluted at 1:50 as described previously (15)
. When the percentages of positive cells exceed 5%, each section was judged to exhibit aberrant p53 expression.
Statistical Methods.
The
2 was used to compare counts. Continuous data were compared using Students t test, if the distribution of samples was normal, or the Mann-Whitney U test, if the sample distribution was asymmetrical. Postoperative survival was analyzed by the Kaplan-Meier method, and the difference was assessed by the log-rank test. A multivariate analysis of prognostic factors was performed using a Coxs regression model. Differences were considered significant when P < 0.05. All statistical manipulations were performed using the SPSS for Windows software system (SPSS, Inc., Chicago, IL).
| RESULTS |
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MMP-2 Status and Other Biomarkers.
The mean VEGF score for strong tumoral MMP-2 tumor (4.15) was significantly higher than that for weak tumoral MMP-2 tumor (3.58, P = 0.030). No significant difference in the mean VEGF score according to the stromal MMP-2 status (Table 2)
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MMP-2 and MMP-9 Status and Postoperative Survival.
Five-year survival rates of the patients with weak MMP-2 expression and strong MMP-2 expression in stromal fibroblasts were 77.5 and 60.2%, showing that weak stromal MMP-2 patients showed a significantly favorable postoperative survival (P = 0.032; Table 3
and Fig. 4
). Subset analyses revealed that the prognostic significance of MMP-2 status in stromal fibroblasts was evident in squamous cell carcinoma patients, especially pathological stage I squamous cell carcinoma patients, but disappeared in adenocarcinoma patients (Table 3)
. Multivariate analyses showed that MMP-2 status in stromal fibroblasts was a marginal prognostic predictor for all NSCLC patients [P = 0.064; relative hazard, 1.666, 95% confidence interval (0.9712.856)]; stromal MMP-2 status was an independent and significant prognostic predictor for squamous cell carcinoma patients (P = 0.022; relative hazard, 9.828, 95% confidence interval (1.41422.911)] but not for adenocarcinoma patients (P = 0.745; relative hazard, 1.119, 95% confidence interval (0.5682.206)].
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| DISCUSSION |
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In contrast to stromal MMP-2 status, MMP-2 or MMP-9 status in tumor cells did not provide a prognostic significance in the present study, although many clinical studies showed that enhanced MMP-2 and/or MMP-9 expression in tumor cells was a significant factor to predict a poor prognosis (8, 9, 10, 11, 12, 13) . In some clinical studies, it has been reported that enhanced expression of MMPs such as MMP-9 may be associated with reduced metastatic proclivity and favorable prognosis (6 , 23 , 24) . These discrepancies may suggest limits of such retrospective studies. Thus, to assess and establish the prognostic significance of MMP-2 and MMP-9 status in tumor cells, as well as MMP-2 status in stromal fibroblasts, prospective clinical studies should be conducted. In addition, recent experimental studies have revealed that proteolytic degradation of ECM barriers by MMPs and other proteolytic enzymes is not essential for tumor cell migration and/or invasion (25) . These results suggest that tumor progression and prognosis may not be predicted by the status of MMPs expression.
Many experimental studies have revealed that MMPs, especially MMP-2 and MMP-9, play important roles in tumor angiogenesis because MMPs degrade the ECM and provide a microenvironment for the development of new vessels (3, 4, 5, 6) , but only a few clinical studies documented correlations between MMPs expression and tumor angiogenesis where enhanced expression of MMP-9, not MMP-2, in tumor cells was correlated with elevated IMVD (26, 27, 28) . We documented a significantly higher CD105-IMVD in tumor with strong MMP-2 expression in stromal fibroblasts, and no significant difference in IMVD according to tumoral MMP-2 or MMP-9 status in the present study. CD 105 (endoglin) is a Mr 180,000 homodimetric membrane glycoprotein expressed on endothelial cells that can bind transforming growth factor ß1 and transforming growth factor ß3, and experimental studies have revealed that CD105 is a marker of proliferating endothelial cells; anti-CD 105 antibodies have greater affinity for activated endothelial cells and preferentially bind to activated endothelial cells in tissues participating in angiogenesis (29) . Thus, in contrast to antibodies against pan-endothelial cells such as anti-CD34 antibodies, anti-CD105 antibodies preferentially react with endothelial cells of all angiogenic tissues, including tumors, but weakly or not at all with those of most normal tissues. In clinical studies, we reported that increased CD105-IMVD, not CD34-IMVD, was significantly correlated with poor postoperative survival, as well as lower incidence of apoptotic cell death in NSCLC (16 , 30) , which was consistent with the results in breast cancer reported by Kumar et al. (31) . The validity of use of CD105 a marker of angiogenesis along with the correlation between MMPs status and angiogenesis should be in future prospective.
In conclusion, enhanced MMP-2 expression in stromal cells, not in tumor cells, was a significant factor to predict a poor postoperative survival in NSCLC, especially squamous cell carcinoma, which might be correlated with active tumor angiogenesis. These results added a new insight into tumor angiogenesis and clinical outcomes in NSCLC and warrant a prospective study to confirm the clinical significance of MMPs status in stromal cells.
| 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.
Requests for reprints: Fumihiro Tanaka, Department of Thoracic Surgery, Faculty of Medicine, Kyoto University, Shogoin-kawahara-cho 54, Sakyo-ku, Kyoto 606-8507, Japan. Phone: 81-75-751-4975; Fax: 81-75-751-4974; E-mail: ftanaka{at}kuhp.kyoto-u.ac.jp
Received 2/12/04; revised 4/19/04; accepted 4/28/04.
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