Acute Leukemia and the FLT3 Receptor

By: Betty Sa’ Mentor: Dr. Govind Bhagat

Site: Columbia UniversityVanderbilt Clinic

LeukemiaLeukemia is a cancer of the blood in which is a cancer of the blood in which immature hematopoietic cells proliferate in an immature hematopoietic cells proliferate in an uncontrolled manner. Leukemia originates in uncontrolled manner. Leukemia originates in the bone marrow and quickly spreads the bone marrow and quickly spreads elsewhere. elsewhere.

There are four major types of Leukemia, Acute There are four major types of Leukemia, Acute Myeloid Leukemia Myeloid Leukemia (AML)(AML), Acute Lymphoblastic , Acute Lymphoblastic Leukemia Leukemia (ALL)(ALL), Chronic Myeloid Leukemia, and , Chronic Myeloid Leukemia, and Chronic Lymphocytic Leukemia. But we are Chronic Lymphocytic Leukemia. But we are only focusing on AML and ALL. only focusing on AML and ALL.

Acute:Acute: means that the disease appears quickly means that the disease appears quickly and advances rapidly, so patients with ALL and and advances rapidly, so patients with ALL and AML usually require immediate treatment.AML usually require immediate treatment.

Acute Lymphocytic Leukemia (ALL) Acute Lymphocytic Leukemia (ALL) is a is a rapidly progressing disease marked by the rapidly progressing disease marked by the overabundance of immature lymphoid cells overabundance of immature lymphoid cells called lymphoblasts (fight bacterial and viral called lymphoblasts (fight bacterial and viral infections) in the blood or bone marrow; most infections) in the blood or bone marrow; most commonly found in children. commonly found in children. ((explainexplain))

Acute Myeloid Leukemia (AML)Acute Myeloid Leukemia (AML) is a rapidly is a rapidly progressing cancer in which there is progressing cancer in which there is uncontrollable growth of immature myeloid uncontrollable growth of immature myeloid cells, caused by some type of mutation cells, caused by some type of mutation (myeloblasts, promyelocytes, monoblasts, (myeloblasts, promyelocytes, monoblasts, erythroblasts, megakaryoblasts) in the bone erythroblasts, megakaryoblasts) in the bone marrow that leads to a deficiency of red blood marrow that leads to a deficiency of red blood cells, platelets, and white blood cells. cells, platelets, and white blood cells. ((explainexplain))

*Since there are many different types of *Since there are many different types of myeloid cells there are also may different myeloid cells there are also may different subtypes of AML depending upon exactly subtypes of AML depending upon exactly which type of cell has become leukemic the which type of cell has become leukemic the stage of maturation the cells are at and stage of maturation the cells are at and whether the cells are differentiated, these whether the cells are differentiated, these sub-types include:sub-types include: Acute Myeloid Leukemia Acute Myeloid Leukemia without maturation, Acute Myeloid Leukemia without maturation, Acute Myeloid Leukemia with maturation, Acute Promyelocytic with maturation, Acute Promyelocytic Leukemia (APL), Acute Myelomonocytic Leukemia (APL), Acute Myelomonocytic Leukemia, Acute Monocytic/ Monoblastic Leukemia, Acute Monocytic/ Monoblastic Leukemia, Acute Erythroleukemia, and Acute Leukemia, Acute Erythroleukemia, and Acute Megakaryoblastic Leukemia).Megakaryoblastic Leukemia).

AML

ALL

FLT3 or FMS-like tyrosine kinase 3, is a gene that FLT3 or FMS-like tyrosine kinase 3, is a gene that encodes a membrane-bound receptor tyrosine kinase encodes a membrane-bound receptor tyrosine kinase (RTK), which plays a crucial role in normal (RTK), which plays a crucial role in normal haematopoiesis. haematopoiesis. Normally, FLT3 expression is restricted to CD34+ Normally, FLT3 expression is restricted to CD34+ hematopoietic stem cells, brain, placenta, and gonads. hematopoietic stem cells, brain, placenta, and gonads. FLT3 is normally activated by the FLT3-Ligand which FLT3 is normally activated by the FLT3-Ligand which promotes the normal in vitro growth of early stem cells. promotes the normal in vitro growth of early stem cells. In Acute Leukemia, mutations of the FLT3 gene have In Acute Leukemia, mutations of the FLT3 gene have been found to be one of the most common acquired been found to be one of the most common acquired genetic lesions. FLT3 mutations can be detected in genetic lesions. FLT3 mutations can be detected in about 7-15% of ALL patients and 30% of AML patients. about 7-15% of ALL patients and 30% of AML patients.

There are two frequent types of somatic FLT3 There are two frequent types of somatic FLT3 genetic mutations: genetic mutations: – Internal Tandem Duplications (ITDs) in the Internal Tandem Duplications (ITDs) in the

Juxtamembrane (JM) Domain (Juxtamembrane (JM) Domain (explainexplain) ) – Point Mutations in the activation loop of the Point Mutations in the activation loop of the

Tyrosine Kinase Domain (TKD). (Tyrosine Kinase Domain (TKD). (explainexplain))

• The presence of FLT3/ITD mutations is associated The presence of FLT3/ITD mutations is associated with a poor clinical outcome in both pediatric and with a poor clinical outcome in both pediatric and adult patients with ALL and AML. But TKD adult patients with ALL and AML. But TKD mutations, unlike ITD mutations, have not been mutations, unlike ITD mutations, have not been shown to have any prognostic significance in ALL shown to have any prognostic significance in ALL or AML patients.or AML patients.

• Both types of FLT3 mutation cause ligand-Both types of FLT3 mutation cause ligand-independent activation of the receptor and independent activation of the receptor and activation of downstream signaling pathways.activation of downstream signaling pathways.((explainexplain) )

In 2006 an estimated 3,930 adultsIn 2006 an estimated 3,930 adults (2,150 men and 1,780 (2,150 men and 1,780 women) women) in the US will be diagnosed with ALL and an in the US will be diagnosed with ALL and an estimated 1,490estimated 1,490 (900 men, 590 women) (900 men, 590 women) deaths will occurdeaths will occur. . ALL is more common in adults older than 50. 20% to 30% ALL is more common in adults older than 50. 20% to 30% of adults with ALL experience long-term disease of adults with ALL experience long-term disease remission or are cured of the disease. remission or are cured of the disease.

ALL is more common in children than in adults; 74% of all ALL is more common in children than in adults; 74% of all new cases are diagnosed in children ages 0 to 19.new cases are diagnosed in children ages 0 to 19.

In 2006, an estimated 11,930 peopleIn 2006, an estimated 11,930 people (6,350 men and (6,350 men and 5,580 women) 5,580 women) in the US will be diagnosed with AML and in the US will be diagnosed with AML and an estimated 9,040 deaths will occur (5,090 men and an estimated 9,040 deaths will occur (5,090 men and 3,950 women).3,950 women). AML is most common in older adults AML is most common in older adults around 60-65 years old.around 60-65 years old.

The percentage of patients who survived at least five The percentage of patients who survived at least five years after being diagnosed, for adults under the age 65 years after being diagnosed, for adults under the age 65 with AML is 33%.with AML is 33%.

To get a better understanding of the molecular To get a better understanding of the molecular abnormalities underlying Acute Leukemia's.abnormalities underlying Acute Leukemia's.

I will study the different types of FLT 3 tyrosine I will study the different types of FLT 3 tyrosine kinase mutations in subsets of acute leukemias kinase mutations in subsets of acute leukemias to determine their relative frequency and to determine their relative frequency and impact on the biologic course of disease.impact on the biologic course of disease.

I will also correlate the presence of FLT3 I will also correlate the presence of FLT3 mutations with other cytogenetic abnormalities mutations with other cytogenetic abnormalities in different types of acute leukemias to better in different types of acute leukemias to better understand the multi-step pathways of understand the multi-step pathways of leukemogenesis. leukemogenesis.

Case selection: Acute leukemias diagnosed at Case selection: Acute leukemias diagnosed at Columbia University Medical Center over the past 5 Columbia University Medical Center over the past 5 years for which cytogenetic information is available years for which cytogenetic information is available (at least 100 cases)(at least 100 cases)DNA extraction from peripheral blood or bone DNA extraction from peripheral blood or bone marrow aspirate samplesmarrow aspirate samples

PCR using primers specific for Exons 11and 12 of PCR using primers specific for Exons 11and 12 of thethe FLT3 geneFLT3 geneCapillary gel electrophoresisCapillary gel electrophoresisAnalysis of electropherograms for FLT3-ITD Analysis of electropherograms for FLT3-ITD mutations (Direct electrophoresis) and FLT3/TKD mutations (Direct electrophoresis) and FLT3/TKD mutations (restriction enzyme digestion followed by mutations (restriction enzyme digestion followed by electrophoresis).electrophoresis).

Rui Zheng & Donald Small. Rui Zheng & Donald Small. Mutant FLT3 Signaling contributes to a block in Myloid Differentiation.Mutant FLT3 Signaling contributes to a block in Myloid Differentiation. Leukemia & LymphomaLeukemia & Lymphoma, December 2005; 46(12); 1679-1687: 2005 Taylor & Francis publishing, December 2005; 46(12); 1679-1687: 2005 Taylor & Francis publishing

Ana Markovic, Karen L. Mackenzie, Richard Block. Ana Markovic, Karen L. Mackenzie, Richard Block. Molecules in focus;Molecules in focus; FLT3: A new focus in the FLT3: A new focus in the understanding of Acute Leukemiaunderstanding of Acute Leukemia . . TheThe International Journal of Biochemistry & Cell BiologyInternational Journal of Biochemistry & Cell Biology 37(2005) 37(2005) 1168-11721168-1172

Derek L. Stirewalt & Jerald P. Radich.Derek L. Stirewalt & Jerald P. Radich.The Role of FLT3 in Hematopoietic MalignaniesThe Role of FLT3 in Hematopoietic Malignanies . 650, September . 650, September 2003, Volume 3. 2003, Volume 3. http://www.nature.com/nrc/index.htmlhttp://www.nature.com/nrc/index.html

Marta libura, Vahin Asnafi, Angela Tu, Eric Delabasse, Isabelle Tigaud, Florence Cymbalista, Annelise Marta libura, Vahin Asnafi, Angela Tu, Eric Delabasse, Isabelle Tigaud, Florence Cymbalista, Annelise Bannaceur-Griscelli, Patrick Villarese, Gabriel Solbu, Anne Hagemeijer, Kheira Beldjord, Oliver Hermine, Bannaceur-Griscelli, Patrick Villarese, Gabriel Solbu, Anne Hagemeijer, Kheira Beldjord, Oliver Hermine, & Elizabeth Macintyre. & Elizabeth Macintyre. FLT3 & MLL intragenic Abnormalities in AML reflect a common Category of FLT3 & MLL intragenic Abnormalities in AML reflect a common Category of Genotoxic StressGenotoxic Stress. . BloodBlood, 15 September 2003. Volume 102, #6 , 15 September 2003. Volume 102, #6

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Dr.Dr. Govind BhagatGovind BhagatDr. Mahesh MansukhaniDr. Mahesh Mansukhani

Columbia UniversityColumbia University Dr. SatDr. Sat

MSKCCMSKCCHarlem Children Society Harlem Children Society