Galectin-4, a Novel Predictor for Lymph Node Metastasis in Lung Adenocarcinoma

<div><p>Metastasis is still a major issue in cancer, and the discovery of biomarkers predicting metastatic capacity is essential for the development of better therapeutic strategies for treating lung adenocarcinoma. By using a proteomic approach, we aimed to identify novel predictors for lymph node metastasis in lung adenocarcinoma. Two-dimensional sodium dodecyl sulfate polyacrylamide gel electrophoresis showed 6 spots differentially expressed between lymph node metastasis-positive and lymph node metastasis-negative groups in a discovery set. Subsequent mass spectrometry showed that 2 of these spots were derived from galectin-4, and western blot analysis confirmed the overexpression of galectin-4 in metastatic samples. The predictive value of galectin-4 was confirmed by immunohistochemical analysis for a validation set consisting of 707 surgically resected specimens of lung adenocarcinomas (stages I to IV). We observed that 148 lung adenocarcinomas (20.9%) expressed galectin-4, which was significantly associated with variables of disease progression such as tumor size (<i>p</i><0.0001), pleural invasion (<i>p</i> = 0.0071), venous invasion (<i>p</i> = 0.0178), nodal status (<i>p</i> = 0.0007), and TNM stage (<i>p</i><0.0001). By the multivariate analysis, Galectin-4 expression was revealed as one of the independent predictor for lymph node metastasis, together with solid predominant and micropapillary histologic pattern. Furthermore, galectin-4 expression was revealed to be an independent predictor for lymph node metastasis and an adverse survival factor in patients with lung adenocarcinoma of acinar predominant type. Galectin-4 plays an important role in metastatic process of lung adenocarcinoma. Immunohistochemical testing for galectin-4 expression may be useful together with the detection of specific histology to predict the metastatic potential of lung adenocarcinoma.</p></div

Validation of the differential expression of galectin-4.

<p>A. A representative result of western blotting for galectin-4 expression and PPIB, together with β-actin as internal control. Three of 5 lung adenocarcinomas with LN metastasis expressed galectin-4 at higher levels than those without LN metastasis. One lung adenocarcinoma with LN metastasis (P3) showed a slightly increased expression level of galectin-4. PPIB expression was observed almost equally in all samples examined. B. Histogram showing the relative expression levels of galectin-4. C. Immunohistochemical expression patterns of galectin-4 in normal lung tissue and lung adenocarcinoma tissues. Lung adenocarcinomas without lymph node metastasis (N1 and N3) showed that both carcinomas and normal lung tissue did not express galectin-4, whereas lung adenocarcinomas with lymph node metastasis (P1 and P5) showed that galectin-4 was strongly expressed in carcinoma cells (magnification ×20). The high-power view of lung adenocarcinomas with lymph node metastasis showed nuclear, cytoplasmic, and membranous expression of galectin-4 (magnification ×100).</p

Kaplan-Meier plots for lung adenocarcinoma belonging to acinar predominant type.

<p>Galectin-4-negative group has survival advantage compared to galectin-4-positive group (p = 0.0464) (A). The difference in the recurrence-free survival was not significant between both groups (B).</p

The relationship between clinicopathological variables and Galectin-4 expression and univariate analysis of prognostic factors.

<p>OS, Overall survival; RFS, recurrence-free survival; AIS, Adenocarcinoma in situ; MIA, Minimally invasive adenocarcinoma.</p

The relationship between nodal status and Galectin-4 expression in each subtype.

<p>The relationship between nodal status and Galectin-4 expression in each subtype.</p

Univariate and multivariate analysis of predictive factors for nodal metastasis.

<p>OR, odds ratio; CI, confidence interval.</p