Lei Y, et al. - In this study, expression of microRNA-222 (miR-222) and matrix metalloproteinase inhibitor 3 (TIMP3) in non-small cell lung cancer (NSCLC) and their significance was discussed. They analyzed 230 patients with NSCLC in the observation group during the operation and used 98 normal adjacent tissues as the control group. Immunohistochemistry revealed significantly higher expression of miR-222 in lung cancer tissue, but lower TIMP3 than that in normal lung tissue. Findings suggest a negative correlation of TIMP3 expression in lung cancer with lung cancer staging and prognosis, which infers it could play a defensive role in lung cancer development; miR-222 showed the opposite effect. The expression of both proteins is observed to be correlated negatively, both proteins may act together in lung cancer progresses.