Correlation between loss of Smad4 and clinical parameters of non-small cell lung cancer: an observational cohort study

Abstract

Background: SMAD4 has been found to be inactivated to varying degrees in many types of cancer; the purpose of this study was to investigate the correlation between SMAD4 expression in non-small cell lung cancer (NSCLC) and clinical pathological parameters.

Methods: The serum concentration of SMAD4 was measured by enzyme-linked immunosorbent assay and its histological expression was quantified by immunohistochemistry.

Results: The serum concentration of Smad4 in patients with NSCLC was lower than that in benign lung disease patients and healthy individuals (P < 0.001) and its concentration was related to the histological classification, pathological differentiation, lymphatic metastasis and clinical stage of NSCLC. The sensitivity and specificity of serum Smad4 were 91.56% and 61.56% for screening NSCLC from healthy individuals and 84.55% and 60.36% for screening NSCLC from patients with benign lung disease. Logistic regression analysis showed that the degree of cell differentiation (P < 0.001), lymph node metastasis (P < 0.001) and clinical stage of NSCLC (P = 0.007) affected the expression of Smad4, and had a strong correlation with the expression of Smad4. The expression of Smad4 in NSCLC tissues was lower than that in normal lung tissues (P = 0.009) and its expression was related to the degree of tissue differentiation, lymph node metastasis and clinical stage (P < 0.05).

Conclusions: The downregulation or deletion of Smad4 is related to the malignant biological behavior of NSCLC and serum Smad4 could be considered as a potential molecular indicator for diagnosis and evaluation of NSCLC.

Keywords: Diagnosis; Evaluation; NSCLC; Non-small cell lung cancer; Smad4.

Fig. 1

Flow chart for grouping of research objects. NSCLC, non-small cell lung cancer

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)

Fig. 3

ROC curve analysis of serum Smad4 to distinguish NSCLC patients from healthy people. a, b Critical value (104 ng/L) of serum Smad4 for discerning NSCLC patients from healthy people had a sensitivity of 91.56% and specificity of 61.56%. c ROC of serum Smad4 for distinguishing NSCLC patients from healthy people (AUC = 0.720). NSCLC, non-small cell lung cancer; ROC, receiver operating characteristic curve; AUC, area under the curve

Fig. 4

ROC curve analysis of serum Smad4 to distinguish NSCLC patients from benign lung disease patients. a, b Critical value (122 ng/L) of serum Smad4 for discerning NSCLC patients from benign lung disease patients had a sensitivity of 84.55% and specificity of 60.36%. c ROC of serum Smad4 for distinguishing lung cancer patients from benign lung disease patients (AUC = 0.744). NSCLC, non-small cell lung cancer; ROC, receiver operating characteristic curve; AUC, area under the curve

Fig. 5

IHC analysis of Smad4 in NSCLC tissues and normal lung tissues adjacent to cancer (IHC × 200). a Negative expression of Smad4 in poorly differentiated LAC; b Positive expression of Smad4 in well differentiated LAC; (C) Negative expression of Smad4 in poorly differentiated LSCC; d Positive expression of Smad4 in well differentiated LSCC; e Negative expression of Smad4 in normal lung tissue adjacent to cancer; f Positive expression of Smad4 in normal lung tissue adjacent to cancer. NSCLC, non-small cell lung cancer; LAC, lung adenocarcinoma. LSCC, lung squamous cell carcinoma

Fig. 6

Correlation between clinical features and Smad4 expression in NSCLC tissues. a Expression of Smad4 was lower in NSCLC tissues than in normal lung tissues adjacent to cancer (P = 0.009). b Expression of Smad4 was lower in poorly differentiated NSCLC than in moderately and well differentiated NSCLC (P = 0.006). c NSCLC patients with lymph node metastasis (N2–N3) had a lower Smad4 expression than patients with lymph node metastasis (N0–N1) (P = 0.010). f NSCLC patients at stage IIIA showed a lower Smad4 expression 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)