BCL2 and B-cell chronic lymphocytic leukemia: Over the past three decades, the treatment of CLL has evolved from an immunochemotherapy regimen, such as rituximab combined with fludarabine, and cyclophosphamide chemotherapy regimen (FCR) to targeted therapy, including Bruton tyrosine kinase (BTK) inhibitor, class I phosphatidylinositol 3-kinases (PI3K) inhibitor, and BCL-2 (proteins in B cell 2) inhibitors, which have greatly improved the overall survival of patients with CLL.