At lower concentrations (50 μM), ceramides blocked the proliferation of these cell lines: the anti-proliferative effect of C2 and C6 ceramides on the breast carcinoma and NHL cell lines tested was reversed by co-culture with CD40L L cells, except for C2 in BT20 breast carcinoma cell line and Daudi and BL70 NHL cell lines (Table 3). This evidence concerns the gene CD40LG and breast carcinoma.