MFG-E8 expression for progression of oral squamous cell carcinoma and for self-clearance of apoptotic cells

Abstract

Milk fat globule-epidermal growth factor (EGF)-factor VIII (MFG-E8) is a secreted glycoprotein that promotes clearance of apoptotic cells by bridging phosphatidylserine on apoptotic cells and integrin avb3/5 on phagocytes. High expression of MFG-E8 has been reported in various types of cancer in humans. Apoptotic figures are frequently found in the surgical samples of oral squamous cell carcinoma (SCC) and carcinoma in situ, and we have often observed apoptotic carcinoma cells engulfed by macrophages or even by neighboring carcinoma cells. Thus we hypothesized that MFG-E8 might promote engulfment of apoptotic carcinoma cells by living carcinoma cells and that MFG-E8 expressed by carcinoma cells could contribute to tumor progression. The aim of this study was to elucidate the biological role of MFG-E8 in oral SCC. Fifty-three surgical specimens of oral SCC were used for immunohistochemistry for MFG-E8, and the expression profiles were correlated with clinicopathological properties. Also, we examined the MFG-E8 expression patterns and functions using three human oral SCC cell lines. Most of the cases had MFG-E8-positive SCC cells, and the expression of MFG-E8 was correlated with such clinicopathological features as tumor size, pathological stage, locoregional recurrence, scattering invasion pattern, and SCC cell figures engulfing apoptotic SCC cells. The MFG-E8 staining was enhanced in apoptotic SCC cells, some of which were apparently engulfed by the neighboring SCC cells. ZK-1 cells showed high MFG-E8 expression, and its localization was found in the cytoplasm and the cell surface. Transient MFG-E8 knockdown by siRNA in ZK-1 decreased cell proliferation and invasiveness and increased cell death. Thus we have demonstrated that MFG-E8 promotes tumor progression in oral SCC and that it might be involved in the clearance of apoptotic SCC cells by living SCC cells. Milk fat globule-epidermal growth factor (EGF)-factor VIII (MFG-E8), a secreted glycoprotein also termed lactadherin, was identified initially as a marker of human breast cancer 1 and later as a major component of milk fat globule membranes in the murine lactating mammary gland. 2 MFG-E8 is a multifunctional protein that has key roles in apoptotic cell clearance, 3 cellular adhesion between sperm and oocyte, 4 morphogenetic and homeostatic regulation in diverse tissues, 5-7 and angiogenesis. 8 Human MFG-E8 contains two repeats of an EGF-like domain on the N-terminal side and two repeated domains homologous to blood coagulation factor V/VIII on the C-terminal side. 9-11 On the removal of apoptotic cells, MFG-E8 secreted by phagocytes binds to phosphatidylserine on the apoptotic cell surface via the factor V/VIII-like domains, as well as to integrin avb3/5 on the plasma membrane of phagocytes via its RGD sequence within the EGF-like domain. 3 Impaired MFG-E8-mediated uptake of apoptotic cells results in autoimmune diseases in MFG-E8-deficient mice, 12 indicating that it is related to immune tolerance induction. 13 Apoptotic cells are cleared in MFG-E8-depend...

Immunoregulatory influence of abundant MFG‐E8 expression by esophageal cancer treated with chemotherapy

“…We examined MFG‐E8 expression in human esophageal squamous cell carcinoma using IHC staining and found that some of the cells abundantly express MFG‐E8, as shown in other types of cancer . As the IHC staining of the samples showed that the expression of MFG‐E8 was more abundant in cancer cells than in macrophages or other stromal cells, MFG‐E8 from cancer cells appears to play an important role in the tumor microenvironment.…”

“…We examined MFG-E8 expression in human esophageal squamous cell carcinoma using IHC staining and found that some of the cells abundantly express MFG-E8, as shown in other types of cancer. [15][16][17][18][19][20]28,30,31 As the IHC staining of the samples showed that the expression of MFG-E8 was more abundant in cancer cells than in macrophages or other stromal cells, MFG-E8 from cancer cells appears to play an important role in the tumor microenvironment. Analysis of all patients examined showed that tumors with high MFG-E8 expression had a significantly higher possibility of having advanced lymph node and non-regional lymph node metastasis (M1), as previously suggested in malignant melanoma patients.…”

“…The intensity of MFG‐E8 expression was examined and classified according to the highest intensity of the staining in each sample. The grades of intensity were determined by comparison with that of endothelial cells of muscular blood vessels found in the same specimen in high‐power (100×) microscopic fields (Figure A). Intensity scores 2, 1, or 0 were given to those with stronger, equal, or weaker staining intensity than vascular endothelial cells, respectively (Figure A‐C).…”

Correction of MFG-E8 Resolves Inflammation and Promotes Cutaneous Wound Healing in Diabetes

“…At the wound-site, successful efferocytosis by mϕ achieves cleansing and resolution of inflammation (10-13). Milk fat globule-epidermal growth factor (EGF)-factor VIII (MFG-E8) is a secreted glycoprotein protein that promotes efferocytosis by bridging apoptotic cells on phagocytes with mϕ (14-15). MFG-E8 contains two EGF domains, a proline/threonine-rich domain, and two factor-VIII-homologous domains (15).…”

Efferocytosis: molecular mechanisms and pathophysiological perspectives

“…showed that tissue and serum exosomes from patients with prostate cancer had a higher expression level of MFGE8 than controls and that MFGE8‐induced efferocytosis lead to macrophage polarization towards a tumor‐promoting M2 phenotype. In addition, the immunohistochemical expression of MFGE8 in surgical specimens of human oral squamous cell carcinoma has been associated with some tumor clinicopathological features including size, stage and invasion patterns . An intensified MerTK signaling in the tumor tissues has been associated with cancer progression, metastasis and resistance to treatment …”