The purpose of this study is to determine if WT1 is an adequate measurement of minimal residual disease in leukemic patients.

Patients with acute Leukemia may have a large number of leukemic cells at the time that leukemia is evident clinically. At the time that we determine that a patient is in complete remission (CR) the patient may still have leukemic cells present in smaller quantities. One of the most important factors in the successful treatment of patients with leukemia is the ability to determine if the eradication of leukemia has been achieved. The determination of Minimal Residual Disease may be important in the determination of the therapy that a given patient will receive as determined by the level of residual disease.

WT1 gene function and expression. The WT1 gene is a candidate gene for Wilms tumor, which is thought to arise as a result from inactivation of both alleles of the WT1 gene located at chromosome 11p13. The WT1 gene has been considered a tumor suppressor gene because intragenic deletions or mutations are found in tumors, germline mutations have been found in-patients with leukemia, and mediates growth suppression of Wilms tumor cells expressing a WT1 splicing variant.

Inclusion Criteria:

• Age less than 21 years of age.
• Patients with the following diseases: Acute lymphoblastic Leukemia (ALL) at the time of diagnoses or relapse, Acute non-lymphoblastic leukemia (ANLL) at diagnosis or after relapse and Chronic Myelogenous leukemia in chronic or accelerated phase.
• Patients will be eligible for any of the available treatment protocols or protocols for stem cell transplantation, regardless of the source of stem cells.
• Patients or legal guardians will sign an Institutional Review Board (IRB) approved informed consent.
• Patients will have venous access or peripheral vein for sampling.