While cell permeable C2 and C6 ceramides induced apoptosis and blocked thymidine incorporation in the 5 NHL and 2 breast carcinoma cell lines tested, co-culture in the presence of CD40L L cells blocked the apoptotic signal induced by C2 and C6 ceramides in NHL and breast carcinoma cell lines. The gene discussed is CD40LG; the disease is non-Hodgkin lymphoma.