72-KD (MMP-2) AND 92-KD (MMP-9) TYPE-IV COLLAGENASE PRODUCTION AND ACTIVITY IN DIFFERENT HISTOLOGIC TYPES OF LUNG-CANCER CELLS

In this study we examined the production of gelatinases A and B (MMP-2 and MMP-9), and their natural inhibitors TIMP-1 and TIMP-2 in cell li nes derived from different histologic types of lung cancer. Gelatinoly tic activity was measured by zymography and radiolabeled gelatin degra dation. Immunocytochemistry and Western blot analysis were performed t o corroborate the presence of immunoreactive MMP-2, MMP-9, TIMP-1 and TIMP-2 proteins. The highest gelatinolytic activity was identified in the cell extracts from a small-cell carcinoma cell line. MMP-9 was obs erved in all samples as a proenzyme, while MMP-2 was present as zymoge n in the squamous-cell and in the small-cell carcinomas, and in its ac tive form in one squamous-cell carcinoma cell line. TIMPs were also pr esent in the neoplastic lung cell lines. TIMP-1 was observed in the me dia of all cells as a 21-kD band, and as TIMP-1 polymers with the exce ption of the small-cell carcinoma samples. TIMP-2 was found as higher- order molecular immunoreactive complexes that may correspond to proMMP -2/TIMP-2 complexes. These results demonstrate that lung neoplastic ce lls produce both MMP-2 and MMP-9 and their inhibitors, with the small- cell carcinoma cell extracts showing the highest enzymatic activity. T his gelatinolytic activity fits well with the clinical metastatic beha vior of this type of lung cancer.