Using the ScltTA/TRE-BCR::ABL1 CML mouse model, we now show for the first time that BCR::ABL1 drives the cytokine independent expansion of BM derived mast cells (BMMCs) and sensitizes them for degranulation, IL-6 and TNF release. The gene discussed is BCR; the disease is chronic myelogenous leukemia, BCR-ABL1 positive.