Safety and Efficacy Study of Umbilical Cord Blood-Drived Mesenchymal Stem Cells to Promote Engraftment of Unrelated Hematopoietic Stem Cell Transplantation

Inclusion Criteria:

1. Patient age 2\~19 years old with plan to have unrelated hematopoietic stem cell transplantation with acute leukemia
2. Patient never has an experience of hematopoietic stem cell transplantation
3. Patient must have an acute leukemia with a complete remission.
4. Patients must have an ECOG 0\~2.
5. No moderate or sever organ dysfunction : Ejection fraction \> 45%; Creatinine \<2.0 mg/ml; Serum bilirubin \< 2 mg/ml; AST/ALT \< 200 IU/L.
6. Patient must not have an transplantation with different source of hematopoietic stem cell such as bone marrow and cord blood.
7. Patient must not have an infection needed an administration of non-oral antibiotics.
8. No active severe infection derived form virus or fungus.
9. Each patient / patient's guardian must sign written informed consent.

Exclusion Criteria:

1. Patient has previously received hematopoietic stem cell transplantation.
2. Patient plans to have a related hematopoietic stem cell transplantation.
3. Patient has a severe internal disease.
4. Patient has enrolled another clinical trial study within last 4 weeks.