ABL1 and chronic myelogenous leukemia, BCR-ABL1 positive: The product of the BCR-ABL gene, the BCR-ABL protein, is a constitutively active protein tyrosine kinase with an important role in the regulation of cell growth [4]; its presence is a strong indicator for CML (since 95% of people with CML have it) but not sufficient on its own for a diagnosis, because 30% of people with ALL will also show Ph+ in their genome.