We assessed the clinical impact of MMP-9 expression on long-term survival in patients with operable non-small cell lung cancer (NSCLC). Primary tumors of 143 consecutive patients with NSCLC resected completely and without overt distant metastases (pT1-4, pN0-2, M0, R0) were examined for MMP-9 expression using immunohistochemistry with a polyclonal, affinity-purified rabbit antibody that recognizes both latent and active MMP-9. Immunohistochemical staining of tumor cells was evaluated in comparison to normal bronchiolar epithelium that served as an internal positive control. MMP-9 expression was categorized into negative, <5% tumor cells stained; heterogeneous, >5% and <95% tumor cells stained; and homogeneous, >95% The standard treatment for early stage NSCLC is surgery resulting in a 5-year survival rate of only 50 -60% in Stage I and II. 5,6 A better understanding of the molecular mechanisms of lung cancer progression might help to identify patients at risk for an unfavorable outcome with potential consequences for adjuvant therapy.Penetration of basement membranes and degradation of extracellular matrix are essential steps in the dissemination of tumor cells from primary tumors to distant organs. 7 One group of proteolytic enzymes that has been associated with these abilities is the matrix metalloproteinase family (MMP). Matrix metalloproteinase 9 (MMP-9) (92 kDa Type IV collagenase or gelatinase B) has the potency to degrade gelatin and Type IV collagen, 8 which is a major component of basement membranes. The clinical relevance of MMP 9 in NSCLC remains in discussion. First clinical trials investigating the efficacy of MMP-inhibitors in advanced cancer were rather disappointing. 9 Furthermore, previous studies examining the prognostic impact of immunohistochemical detection of MMP-9 in NSCLC 10,11 are discussed controversially because they did not demonstrate an independent prognostic impact of MMP-9 considering all standard prognostic factors included in the international system for staging lung cancer. 6 To clarify the prognostic impact of MMP 9 in operable NSCLC, we applied a new immunohistochemical evaluation system, focusing on homogeneous expression of MMP-9. The prognostic value was analyzed in relation to established prognostic factors of the TNM-system. Our study shows that the prognostic impact of homogeneous MMP-9 expression remains independent from possible prognostic joint effects of pT-status, pN-status, tumor histology and tumor grading. Because of this independence, MMP-9 may be considered as an interesting target for adjuvant anticancer therapy in operable NSCLC using selective MMP-inhibitors with high specificity for MMP-9. MATERIAL AND METHODS PatientsAfter approval by the ethical committee of the University of Munich and after written informed consent, tissue specimens of 147 consecutive patients with completely resected NSCLC were collected. The tumors were classified according to the international union against cancer (UICC) TNM-classification. 6 The preoperative staging of all patient...

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