Correlation between the expression of thrombospondin-1 and neovascularization in mucoepidermoid carcinoma

Background Researchers have recently demonstrated that thrombospondin-1 （TSP-1） has an important function in regulating neovascularization. Whether it inhibits or accelerates neovascularization, however, is still controversial. We found few reports about the correlation between TSP-1 and vascularization in mucoepidermoid carcinoma. In this research, the distribution and expression of TSP-1 in mucoepidermoid carcinoma were investigated. We also analyzed （1） the correlation between the expression of TSP-1 and microvessel density （MVD）, as an indicator of neovascularization activity, and （2） the effect of TSP-1 on neovascularization and tumor growth in the subcutaneous xenotransplanted model of mucoepidermoid carcinoma. Method （1） The sites and intensity of expression of TSP-1 and the MVD were analyzed in 45 cases of mucoepidermoid carcinoma after surgery by the method of streptavidin-peroxidase （SP） immunohistochemistry; and （2） recombinant human thrombospondin-1 （rhTSP-1） was injected twice a week for five consecutive weeks around the tumor in the subcutaneous xenotransplanted tumor model of mucoepidermoid carcinoma in nude mice. Each week, the tumor size was measured, in order to draw the growth curve of the xenotransplanted tumor model of mucoepidermoid carcinoma, and MVD was measured. Results （1） The positive expression of TSP-1 protein was 57.78% （26/45）. Most positive staining for TSP-1 was found in the cytoplasm of the cancer cells, while some staining occurred in the extracellular matrix. The mean MVD in 45 cases of m ucoepidermoid carcinoma was 58.17±19.77 per 100 visual fields. Tumors with a high expression of TSP-1 showed a low MVD value, and the TSP-1 immunocompetence and microvessel density showed a significant negative correlation （rs=-0.947, P 〈0.001）. （2） The xenotransplanted tumors with the injection doses of 1.25, 0.75 and 0.25 ug/ml respectively were 36.97%, 53.36% and 73.61% of the size of the control group （（451±92）, （651±113）, （898±86） and （1220±157） mm^3 respectively, F=-53.167, P 〈0.001）, and their weights were respectively 35.14%, 51.35% and 70.27% of the control group （（1.3±0.5）, （1.9±0.5）, （2.6±0.3）, and （3.7±0.7） g respectively, F=-62.669, P 〈0.001）. Their MVDs were 25.00%, 45.93%, and 72.20% respectively of the control group and concentration dependent （15.43±3.45, 28.35±4.24, 44.57±3.35 and 61.73±5.43 per 100 visual fields respectively, F=54.582, P 〈0.001）. Conclusions The TSP-1 has a higher expression in mucoepidermoid carcinoma and the expression has a significant negative correlation with neovascularization. The TSP-1 inhibits neovascularization and tumor growth, and it might be a new biological therapy for treatment of patients with mucoepidermoid carcinoma.

Derived vascular endothelial cells induced by mucoepidermoid carcinoma cells:3-dimensional collagen matrix model

Mucoepidermoid carcinoma undergoes uniquely vigorous angiogenic and neovascularization processes,possibly due to proliferation of vascular endothelial cells(ECs) induced by mucoepidermoid carcinoma cells(MCCs) in their three-dimensional(3D) microenvironment.To date,no studies have dealt with tumor cells and vascular ECs from the same origin of mucoepidermoid carcinoma using the in vitro 3D microenvironment model.In this context,the current research aims to observe neovascularization with mucoepidermoid carcinoma microvascular ECs(MCMECs) conditioned by the microenvironment in the 3D collagen matrix model.We observed the growth of MCMECs purified by immunomagnetic beads and induced by MCCs,and characteristics of tubule-like structures(TLSs) formed by induced MCMECs or non-induced MCMECs.The assessment parameters involved the growth curve,the length,the outer and inner diameters,and the wall thickness of the TLSs,and the cell cycle.Results showed that MCCs induced formation of the TLSs in the 3D collagen matrix model.A statistically significant difference was noted regarding the count of TLSs between the control group and the induction group on the 4th day of culture(t=5.00,P=0.001).The outer and inner diameters(t1=5.549,P1=0.000;t2=10.663,P2=0.000) and lengths(t=18.035,P=0.000) of the TLSs in the induction group were statistically significant larger than those in the control group.The TLSs were formed at the earlier time in the induction group compared with the control group.It is concluded that MCCs promote growth and migration of MCMECs,and formation of the TLSs.The 3D collagen matrix model with MCMECs induced by MCCs in the current research may be a favorable choice for research on pro-angiogenic factors in progression of mucoepidermoid carcinoma.