Objective  To investigate the expression and clinical significance of matrix metalloproteinase-12 (MMP-12) in non-small cell lung cancer (NSCLC).  Methods  Reverse transcription-polymerase chain reaction (RT-PCR) was used to detect MMP-12 mRNA expressions in 38 NSCLC the tumor tissues

including 12 samples of stage Ⅰ and 26 of stage Ⅱ and Ⅲ

and the matched normal lung tissues. Western blotting was used to measure the protein expression of MMP-12 in some tissue samples. Clinicopathological data were collected

and the relationship of MMP-12 mRNA and MMP-12 protein expression were analyzed with the clinicopathologi

cal characteristics of NSCLC.  Results  There was no expression of MMP-12 in 38 matched normal lung tissue

and MMP-12 mRNA was expressed in the NSCLC at stage Ⅰ (0.551±0.140)

and at stage Ⅱ and Ⅲ tumor tissues (1.082±0.424) with significant difference (

P

=0.001)

MMP-12 protein was not found in normal lung tissues

but expressed mild in the cancer tissue at stage Ⅰ

and highly in the tissues at stage Ⅱ and Ⅲ.  Conclusion  MMP-12 is highly expressed in NSCLC at stage of Ⅱ and Ⅲ

and significantly correlated with lymphatic node metastasis. The abnormal expression of MMP-12 in gene transcription may play an important role in the tumorogenesis and development of NSCLC.