Specific tumor-stroma interactions of EBV-positive Burkitt's lymphoma cells in the chick chorioallantoic membrane

Background: Burkitt's lymphoma (BL) is an aggressive Non-Hodgkin lymphoma. Epstein-Barr Virus (EBV) is able to transform B cells and is a causative infectious agent in BL. The precise role of EBV in lymphoma progression is still unclear. Most investigations have concentrated on cell autonomous functions of EBV in B cells. Functions of the local environment in BL progression have rarely been studied, mainly due to the lack of appropriate in vivo models. Therefore, we inoculated different human BL cell-lines onto the chorioallantoic membrane ( CAM) of embryonic day 10 ( ED10) chick embryos and re-incubated until ED14 and ED17. Results: All cell-lines formed solid tumors. However, we observed strong differences in the behavior of EBV+ and EBV-cell-lines. Tumor borders of EBV+ cells were very fuzzy and numerous cells migrated into the CAM. In EBVtumors, the borders were much better defined. In contrast to EBV-cells, the EBV+ cells induced massive immigration of chick leukocytes at the tumor borders and the development of granulation tissue with large numbers of blood vessels and lymphatics, although the expression of pro-and anti-angiogenic forms of Vascular Endothelial Growth Factors/receptors was the same in all BL cell-lines tested. The EBV+ cell-lines massively disseminated via the lymphatics and completely occluded them. Conclusions: Our data suggest that the EBV+ cells attract pro-angiogenic leukocytes, which then induce secondary tumor-stroma interactions contributing to the progression of BL. We show that the CAM is a highly suitable in vivo model to study the differential behavior of BL cell-lines.