The primary tumors and adjacent normal tissues in a cohort of 52 patients were analyzed by quantitative real-time reverse transcription polymerase chain reaction (qRT-PCR) for the expression of miR-205 and SMAD4. The functions of miR-205 and its molecular link to SMAD4 were also investigated in cell lines and transplanted tumor models of lung carcinoma in mice. Here, SMAD4 is linked to neoplasm.