The Correlation Between HMGB1and Tumor-Associated Macrophages On Lymphangiogenesis In Ovarian Cancer

Objective. The tumor microenvironment is quite complicated which consists of cancer cells as well as noncancer cells and noncellular components (pro-tumoral mediators). Multiple lines of evidence have demonstrated that the inflammatory tumor microenvironment predisposes tumorigenesis and orchestrates tumor progression. High-mobility group box1protein (HMGB1) and tumor-associated macrophages (TAMs), as two important components within tumor microenvironment, are able to influence ovarian cancer development and progression via facilitating tumor lymphangiogenesis and lymphatic metastasis. Although HMGB1could display signaling activities on macrophages, the association between HMGB1and TAMs in epithelial ovarian cancer’s (EOC) lymphangiogenesis remains elusive. In this study, we aim to explore whether HMGB1could interact with TAMs so as to amplify lymphangiogenesis in human EOC.Methods.(1) HMGB1, TAMs and lymphatic vessel density (LVD) in108cases of ovarian tissues were measured by immunohistochemistry (IHC) staining of HMGB1, CD68, and D2-40, respectively.(2) The relationships between HMGB1and LVD or TAMs and LVD were assessed by Spearman rank correlation test, and Pearson correlation test, respectively.(3) In vitro study, TAMs were isolated from ascites of EOC patients with MACS. Human lymphatic endothelial cells (LECs) were treated with different conditioned media:rHMGBl(2μg/ml); supernatants from cultures of TAMs; supernatants from TAMs pretreated with rHMGBl(2μg/ml); while rVEGF-C (5ng/ml) served as a positive control and ECM alone served as a negative control. Changes in LECs proliferation, migration, and the capillary-like tube formation were assessed by CCK-8assay, transwell chamber assay, and a Matrigel model, respectively.Results.(1) The expression of HMGB1and the number of infiltrating TAMs were overexpressed in malignant ovarian tumors compared with that in normal ovarian and were closely associated with lymph node metastasis.(2) Using the Spearman rank correlation coefficient analysis, a positive correlation occurred between the expression of HMGB1and LVD (r=0.491,P<0.001). Pearson correlation test was performed to assess the correlation between TAMs count and LVD and data revealed that TAM influx was positively correlated with LVD (R2=0.242, P<0.001).(3) In vitro study, our data demonstrated that rHMGBl or TAMs could facilitate lymphangiogenesis by inducing LECs proliferation, migration, and capillary-like tube formation ability. Meanwhile, HMGB1combining with TAMs may augment the pro-lymphgiogenetic property.Conclusions. HMGB1expression and TAMs influx were closely associated with lymph node metastasis in malignant EOCs. Our data suggest that either HMGB1or TAMs could facilitate lymphangiogenesis, while HMGB1coculture with TAMs may strengthen the pro-lymphangiogenic potential, which may serve as a therapeutic target for ovarian cancer.