"While I understood that the TKI's were inhibiting the production of the immature (non normal) WBC, I don't understand how that works to reduce the BCR-ABL activity. I thought that the Sprycel was just stopping the bone marrow from producing the wrong wbcs. But that the translocation of the Philadelphia syndrome was still occuring."
The TKI drugs turn off the ABL found in the BCR-ABL which is in the leukemic cells, which in turn confuses the leukemic cell, and it shuts down and dies. It does not stop the high level leukemic stem cells from producing new leukemic cells (the stem cells are believed to be immune to TKI drugs), but it shuts down and kills those leukemic offspring that are produced by the leukemic stem cells. So the leukemic stem cells keep producing, and the TKI drugs keep killing. It is a matter of population control through execution, not preventing the procreation by the stem cells.
"It seems though, that if one is to get to cytogenic and the MMR response, it would mean that the translocation was no longer occuring."
The translocation occurs once at the beginning of the leukemic process. At that point we had one leukemic stem cell. After that the offspring of that one cell all have the leukemic transloction. This will be the case until the disease is cured (some day).
Sprycel attacks higher level leukemic cells than Gleevec or Tasigna. This is believed to be due to its ability to inhibit the SRC family of kinases. Those higher level leukemic cells are senior progenitor cells, and probably not actually stem cells.