An In Vitro Screening to Identify Drug-Resistant Mutations for Target-Directed Chemotherapeutic Agents

The discovery of oncogenes and tumor suppressors as a driver of cancer development has triggered the development of target-specific small molecule anticancer compounds. As exemplified by Imatinib (Gleevec), a specific inhibitor of the Chronic Myeloid Leukemia-associated BCR/ABL kinase, these agents promise impressive activity in clinical trials, with low levels of clinical toxicity. However, such therapy is susceptible to the emergence of drug resistance mainly due to amino acid substitutions in the target protein. Defining the spectrum of such mutations is important for patient monitoring and the design of next-generation inhibitors. Using Imatinib and BCR/ABL as a paradigm for a drug–target pair, we reported a retroviral vector-based screening strategy to identify the spectrum of resistance-conferring mutations, which has helped in designing the next-generation BCR/ABL inhibitors such as Nilotinib, Dasatinib, and Ponatinib. Here we provide a detailed methodology for the screen, which can be generally applied to any drug–target pair.