Bone morphogenetic proteins (BMPs) are members of the TGF-β superfamily and are aberrantly expressed in many types of carcinoma cells, including prostate, lung, breast, gastric, and ovarian [13–16]. BMP-2 is known to stimulate proliferation, differentiation, and migration during embryonic development [6, 17–21]. BMP-2 abrogated the fibrogenic function of TGF-β in pancreatic stellate cells via the Smad1 signaling pathway . Moreover, high concentrations of BMP-2 strongly enhanced gastric cancer cell motility and invasiveness . BMP-2 upregulation caused epithelial dysfunction and hyperpermeability , and enhanced the neovascularization of developing lung tumors. BMP-2 is aberrantly expressed in approximately 98% of lung carcinomas . BMP-2 is highly overexpressed in human NCSLC compared with normal lung tissue and benign lung tumors, and high BMP-2 levels enhanced tumor cell migration and invasion, thereby promoting tumor growth [10, 11, 26, 27]. Thus, these data indicate that BMP-2 has important biological activity in lung carcinomas and a potential marker of lung carcinomas. Up to now, several lung carcinomas potential markers had reported, such as Tiam1, MAT3, DNA methylome [28–30].
In this study, we observed that the mRNA expression of BMP-2 in tumor tissue was significantly higher than in matched adjacent normal tissues (P < 0.01). Furthermore, we found that BMP-2 expression was related to lymph node metastasis, tumor stage, and survival time. These results suggest that BMP-2 may play a role in tumor metastasis.
High levels of BMP-2 promote tumorigenesis. However, downregulation of BMP-2 reduced tumor growth. For example, inhibition of BMP-2 activity using either recombinant Noggin or a BMP-2 antibody caused a reduction in lung tumor growth . Blocking BMP signaling with the inhibitor DMH1 reduced lung cell proliferation, promoted cell death, and decreased cell migration and invasion in NSCLC cells . BMP-2 knockdown by adenovirus inhibited growth and invasion of human lung adenocarcinoma cells by blocking PI3K/AKT signaling . In this study, we suppressed BMP-2 activity by siRNA. These data show that suppressing BMP-2 expression significantly inhibited lung tumor cell proliferation and migration (Figures 3 and 4). This outcome is in accordance with previous studies and further confirms the biological function of BMP-2 in lung cancer.
Previous studies of BMP-2 have focused on the expression of BMP-2 in tumor tissues and its function in tumor cell proliferation, invasion, and migration. However, for the first time, we investigated and assessed the relationship between BMP-2 expression and clinicopathological characteristics. Our analyses found significant correlations between BMP-2 expression and lymph node metastasis, TNM stage, tumor stage, and survival time (Figure 1). Transwell migration assays also showed that the number of siBMP-2-transfected cells that migrated decreased. This result suggests that BMP-2 expression is closely related to lung tumor metastasis.