- Chronic lymphocytic leukemia and small lymphocytic lymphoma (hereby referred as CLL) are tumors of B cells. A subset of patients categorized as high-risk CLL has a poor clinical outcome when treated with conventional chemotherapy. High-risk CLL is defined by relapsed/refractory disease status, or the presence of high-risk mutations, such as deletion 17p, TP53, and NOTCH1. While the cause of CLL is still unclear, studies have indicated critical factors required for the tumor cells. First, CLL cells grow and survive because they receive signals through the B-cell receptor (BCR); and second, CLL cells benefit from interactions with other cells, especially T cells.