Expression of Delta Like Ligand 4 (DLL4) in endometrial carcinomas and tumor vasculature.

PURPOSE: Delta like ligand 4 (DLL4) is a transmembrane ligand of the Notch Signalling pathway, that regulates blood vessel sprouting and maturation. We investigated the expression of DLL4 in endometrial cancer. METHODS: DLL4 was assessed in the plasma (with ELISA) and tissues (with immunohistochemistry) 33 patients with endometrial cancer, treated with radical hysterectomy for stage I endometroid carcinoma. The angiogenic activity (AA) of endometrial cancer was quantified by assessing the CD31+ microvessel density (MVD) in the invading tumor front. Vascular maturation index (VMI), defined as the percentage of CD31+ microvessels expressing DLL4, was calculated as the ratio of the CD31+ MVD to the DLL4+ MVD. RESULTS: The angiogenic activity was directly related with the histological grade (p=0.01). The VMI ranged from 0.1 to 0.7 (median 0.34). The concentration of DLL4 in the plasma ranged from 55-81pg/ml (mean 62.8) before, and dropped to 55-62 (mean 58.2) after hysterectomy (p<0.05). DLL4 was also expressed by cancer cells in 17/33 cases. No correlation between DLL4-related parameters with histopathological variables was noted. CONCLUSION: This pilot study shows that DLL4 is overexpressed in endometrial cancer cells, vasculature and is also elevated in the plasma of a fraction of patients before surgery. The percentage of DLL4+ vessels in the penetrating sample ranged from 10-70%, indicating a large difference in the quality of angiogenesis produced between the endometrial tumors of the same histological type and differentiation.