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.