Truncation variants of BCR-ABL mRNA that produces BCR-ABL proteins with a truncated C-terminus and its role in resistance to treatment with kinase inhibitors is described. Vectors for expressing the truncated gene products are described as well as recombinant cells that express the truncated gene products from cDNA constructs. Also provided are methods compositions and kits for detecting the BCR-ABL truncation variants. Also provided are methods for determining the prognosis of a patient diagnosed as having myeloproliferative disease, and methods for predicting the likelihood for resistance to a treatment with tyrosine kinase inhibitor in a patient diagnosed as having myeloproliferative disease. Additionally, methods for screening BCR-ABL tyrosine kinase domain inhibitors which rely on the recombinant cells are also disclosed.