Fig. 2

Correlation between clinical features and serum concentration of Smad4 in NSCLC patients. a Serum concentration of Smad4 was lower in NSCLC patients than in patients with benign lung disease and healthy people (P < 0.05). b Serum concentration of Smad4 was lower in female patients than in male patients (P = 0.001). c Serum concentration of Smad4 was lower in LAC patients than in LSCC patients (P < 0.001). d Serum concentration of Smad4 was lower in poorly differentiated NSCLC than in moderately and well differentiated NSCLC (P < 0.001). e NSCLC patients with lymph node metastasis (N2–N3) showed a lower concentration of Smad4 than patients with lymph node metastasis (N0–N1) (P < 0.001). f NSCLC patients at stages IIIA–IV showed a lower concentration of Smad4 than patients at stages IA–IIB (P < 0.001). NSCLC, non-small cell lung cancer; LAC, lung adenocarcinoma. LSCC, lung squamous cell carcinoma. N, node stage (TNM classification)