Bcr-aBL1 kinase domain mutation analysis in chronic myeloid leukaemia patients with suboptimal response to tyrosine kinase inhibitors

Abstract

Background: The acquired mutations in the BCR-ABL1 kinase domain (KD) may contribute to resistance to tyrosine kinase inhibitors (TKIs) in chronic myeloid leukemia (CML) patients. The aim of our work was to perform the BCRABL1 mutation analysis in a cohort of CML patients receiving TKIs, who did not achieve a major molecular response (MMR) by 18 months or more, or who lost MMR. Methods: Nine CML patients (7 female, 2 male) were included in the study. Total RNA was extracted from peripheral blood leukocytes and used to prepare complementary DNA (cDNA) by reverse transcription. The entire ABL1 kinase domain of the rearranged BCR-ABL1 allele was amplified using a nested PCR. The PCR products were analyzed using an ABI Prism 310 sequencer. Sequences were compared with the wild-type ABL1 sequence. In addition, the T315I mutation detection was carried out by the more sensitive method-allele specific oligonucleotidepolymerase chain reaction (ASO-PCR). It is a highly-resistant mutation to imatinib, nilotinib and dasatinib. Results: The T315I mutation was detected in one out of nine CML patients by direct sequencing and ASO-PCR. The silent mutation p.Glu499Glu was detected in another CML patient by direct sequencing. No mutation was found in the rest of the cohort of CML patients. Conclusions: It seems that the BCR-ABl1 mutations are rare in patients who do not achieve a MMR by 18 months or more or who have lost MMR. The T315I mutation detected in one patient in our cohort of CML patients indicates that the BCR-ABL1 mutation analysis could be recommended in these cases. The silent mutation detected did not lead to amino acid change, however, it is listed in major single nucleotide polymorphisms databases (SNP, rs2227985). The role of the SNP in the resistance to TKIs is not clear.