Research conducted over the last two decades has yielded a detailed understanding of the molecular lesions that contribute to the malignant transformation of hematopoietic stem cells and committed progenitors into the various forms of acute and chronic leukemia. Although our understanding of the molecular pathology of leukemia remains incomplete, the information gained to date has had a profound impact on the way these malignancies are both diagnosed and monitored during therapy. More recently, targeted therapies have been developed against some of the identified genetic lesions. These therapies have led to significant improvements in patient outcomes while simultaneously decreasing therapy-related toxicity.
Philadelphia chromosome (Ph)/BCR/ABL-positive acute lymphoblastic leukemia is the most common genetic abnormality associated with adult acute lymphocytic leukemia and has been shown to confer the worst prognosis to both children and adults. BCR–ABL tyrosine kinase inhibitor (TKI) become the main treatment of targeted therapy of acute lymphocytic leukemia
Chronic lymphocytic leukemia (CLL) is a type of cancer that starts from cells that become certain white blood cells (called lymphocytes) in the bone marrow. The cancer (leukemia) cells start in the bone marrow but then go into the blood. Targeted therapy attacks one or more specific targets on or in cancer cells. The most common targets are BTK, PI3K and BCL-2.
The Philadelphia chromosome (Ph), t(9;22), is the cytogenetic hallmark of chronic myeloid leukemia, this balanced translocation results in the creation of a chimeric BCR-ABL gene that expressesa n 8.5-kb hybrid mRNA transcript and a 210-kD fusion protein. The BCR-ABL gene acted like the gas pedal in a car stuck in the "on" position, fueling the excess growth of white blood cells in chronic myeloid leukemia. With the target identified, a drug discovery program was started, aimed at developing a drug to shut down the activity of BCR-ABL.
Traditional therapy for acute myeloid leukemia (AML) relies on conventional DNA-targeted chemotherapy, such as cytarabine plus either daunorubicin or idarubicin. They work by targeting acute myeloid leukemia blasts more than normal cells to produce remission, and are highly cytotoxic. It is increasingly clear that many of these classical therapies cause genetic damage to surviving leukemia cells, which contributes to relapse via the selection of resistant clones. With the discovery of novel tumor-associated mutations and their protein antigens, and the expanding insights into the mechanisms of epigenetic gene regulation and the functions of oncogenic kinases, development of nongenotoxic, “more targeted” therapy with monoclonal antibodies or other inhibitors is being rapidly explored.
Downing J R. Targeted therapy in leukemia[J]. Modern Pathology, 2008, 21: S2-S7.
Leoni V et al. Tyrosine kinase inhibitors in BCR-ABL positive acute lymphoblastic leukemia[J]. Haematologica, 2015, 100(3): 295.
Woyach JA, et al. Bruton’s tyrosine kinase (BTK) function is important to the development and expansion of chronic lymphocytic leukemia (CLL). Blood. 2014;123(8):1207-1213.
Bedi A et al. Inhibition of apoptosis by BCR-ABL in chronic myeloid leukemia[J]. Blood, 1994, 83(8): 2038-2044.
Sawyers C L. Finding the next Gleevec: FLT3 targeted kinase inhibitor therapy for acute myeloid leukemia[J]. Cancer cell, 2002, 1(5): 413-415.