Genomic Mechanisms Influencing Outcome in Chronic Myeloid Leukemia

SIMPLE SUMMARY: Chronic myeloid leukemia (CML) is a blood cancer currently well managed with drugs that inhibit the protein responsible for the disease. However, some patients are resistant to these drugs and can progress to fatal phases of CML. This review focuses explicitly on genomic mechanisms that contribute to drug resistance in CML. The ability to predict how patients will respond to treatment at the early stages of the disease is important for selecting optimal therapy and administering more potent drugs before the disease progresses. Currently, only mutations that affect drug binding are included in routine monitoring in drug-resistant patients. This review illustrates other genomic mutations and sequence rearrangements that may impact treatment response and contribute to drug resistance and disease progression. We highlight the potential future role of expanded genomic testing for managing patients with CML. ABSTRACT: Chronic myeloid leukemia (CML) represents the disease prototype of genetically based diagnosis and management. Tyrosine kinase inhibitors (TKIs), that target the causal BCR::ABL1 fusion protein, exemplify the success of molecularly based therapy. Most patients now have long-term survival; however, TKI resistance is a persistent clinical problem. TKIs are effective in the BCR::ABL1-driven chronic phase of CML but are relatively ineffective for clinically defined advanced phases. Genomic investigation of drug resistance using next-generation sequencing for CML has lagged behind other hematological malignancies. However, emerging data show that genomic abnormalities are likely associated with suboptimal response and drug resistance. This has already been supported by the presence of BCR::ABL1 kinase domain mutations in drug resistance, which led to the development of more potent TKIs. Next-generation sequencing studies are revealing additional mutations associated with resistance. In this review, we discuss the initiating chromosomal translocation that may not always be a straightforward reciprocal event between chromosomes 9 and 22 but can sometimes be accompanied by sequence deletion, inversion, and rearrangement. These events may biologically reflect a more genomically unstable disease prone to acquire mutations. We also discuss the future role of cancer-related gene mutation analysis for risk stratification in CML.