What is stem cells used for with cancer?

Stem cells: Stem cells are cells in the body with the capacity to differentiate into many (pluripotent) or all (totipotent) cell types. Often, they are harvested from bone marrow for blood cancers (leukemias), the residual marrow destoyed to remove the blood cancer, and then the marrow is re-populated with the non-cancerous stem cells to replace all the cells that were killed, cancer-free.