Association of the expression of leptin and leptin receptor with bone metastasis in pulmonary adenocarcinoma

Objective To explore the association of expression of leptin and leptin receptor (LR) with bone metastasis of pulmonary adenocarcinoma. Methods One hundred and sixteen pulmonary adenocarcinoma patients who had complete clinicopathological data and definite pathological diagnosis in our hospital from January 2008 to January 2010 were selected. They were divided into the metastasis (n= 58) and non-metastasis (control, n=58) groups. The expressions of leptin and LR were identified by immunohistochemistry. The differences between expressions of leptin and LR in primary pulmonary adenocarcinoma tissues and metastasis, and between the groups with and without bone metastasis were analyzed. We also analyzed the correlation of leptin and LR expressed in primary adenocarcinoma and bone metastatic tissues, and the relationship between their expression levels and bone metastasis free survival (BMFS). Results Among 58 patients of the metastasis group, the cases of high, moderate and low expressions of leptin were 36, 15 and 7, respectively, and the cases of high, moderate and low expressions of LR were 32, 17 and 9, respectively. Among the 58 patients of control group, the cases of high, moderate and low expressions of leptin were 19, 24 and 15, respectively, and those of LR were 17, 16 and 25, respectively. The expressions of leptin and LR in primary pulmonary adenocarcinoma tissues of metastasis group were significantly different from those of the control group (P=0.006, P=0.002, respectively). The expressions of leptin and LR in primary pulmonary adenocarcinoma tissues of the bone metastasis group were also significantly different from those of the non-bone metastasis group (P=0.029, P=0.032, respectively). The high/moderate expression rates of leptin and LR in the bone-metastatic tissues reached 91.4% (32/35) and 88.6% (31/35), respectively. The results showed that the expressions of leptin and LR in primary pulmonary adenocarcinoma tissues were positively related with their expressions in bone metastatic tissue (r = 0.612). The median bone metastasis free survival (BMFS) of the bone metastasis groups with high, moderate and low expressions of leptin were 14, 21 and 47 months, respectively, and the median BMFS of high, moderate and low expressions of LR in the bone metastasis group were 13, 19 and 27 months, respectively. The expressions of leptin and LR in pulmonary adenocarcinoma were significantly associated with BMFS (P<0.001, P=0.006, respectively). Conclusions The expressions of leptin and LR are significantly up-regulated in primary pulmonary adenocarcinoma tissues and bone metastatic tissues, and are negatively correlated with BMFS. These two molecules may be used as effective predictors of bone metastasis in pulmonary adenocarcinoma. Key words: Lung neoplasms; Leptin; Leptin receptor; Neoplasm metastasis; Prognosis