Other studies have examined the CD40/Fas costimulatory effects on apoptosis in malignant cells and found that this also occurs in a range of tumour cell lines including the human myeloma cell line XG2 [50], B cell lymphoma cells [51], breast carcinoma cell lines [52] and chronic lymphocytic leukemia cells [53]. Here, FAS is linked to B-cell chronic lymphocytic leukemia.