Abstract 657: Impact of therapy induced APOBEC3A mutagenesis on tumor evolution in non small cell lung cancer

Acquired drug resistance to even the most effective anti cancer targeted therapies remains an unsolved clinical problem. Although many drivers of acquired drug resistance have been identified, the underlying molecular mechanisms shaping tumor evolution during treatment are incompletely understood. We have seen that lung cancer targeted therapies commonly used in the clinic induce the expression of cytidine deaminase APOBEC3A (A3A), leading to sustained mutagenesis in drug tolerant cancer cells persisting during therapy. Preventing therapy induced A3A mutagenesis by gene deletion delayed the emergence of drug resistance. Here, we show that therapy induced A3A mutagenesis contributes to tumor evolution in NSCLC. Whole genome sequencing revealed that resistant clones that evolved from persistent drug tolerant cells (late clones) harbored more A3A mutations compared to the parental cell population than pre existing resistant clones (early clones). In a subset of NSCLC patients who received targeted therapies, we observed A3A mutations accompanied clonal evolution during treatment. Comparison of APOBEC mutation fractions in short vs long term responders suggests that short responders with acquired resistance mechanisms that evolved from pre existing resistant clones have less accumulation of APOBEC mutations. Collectively, these findings insist that an increase in mutagenic processes drives tumor evolution during targeted therapy treatment and leads to acquired resistance. Thus, suppressing expression or enzymatic activity of A3A may represent a potential therapeutic strategy to halt the evolution of resistant clones and prevent acquired resistance to lung cancer targeted therapy.

Citation Format: Hideko Isozaki, Ammal Abbasi, Naveed Nikpour, Marcello Stanzione, Ramin Sakhtemani, Susanna L. Monroe, Alice T. Shaw, Jessica J. Lin, Lecia V. Sequist, Zofia Piotrowska, Rémi Buisson, Michael S. Lawrence, Aaron N. Hata. Impact of therapy induced APOBEC3A mutagenesis on tumor evolution in non small cell lung cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 657.

Evaluation of an Automated Instrument for Viability and Concentration Measurements of Cryopreserved Hematopoietic Cells

Two important parameters for determination of deleterious effects of cellular processing on hematopoietic progenitor cells are cell viability and concentration. The Sidney Kimmel Comprehensive Cancer Center at Johns Hopkins Hospital evaluated the Beckman Coulter Vi-Cell automated instrument for the measurement of these two parameters. Using 33 thawed hematopoietic progenitor cell samples, automated Vi-Cell viability results were compared to those obtained using the standard trypan blue manual method. In addition, cell concentrations from these samples were compared with results from the Model Z2 Coulter Counter. Chinese Hamster Ovary cells were used for the evaluation of Vi-Cell linearity at the Beckman Coulter Cellular Analysis Development Center. Significant correlation was obtained when the two methods were compared for both cell concentration and percentage viability (P < .0001). The results of the linearity study indicated that the Vi-Cell is linear from approximately 5 x 10(4) to greater than 1 x 10(7) cells/mL. The Vi-Cell uses sample volumes as low as 0.5 mL; cell diameters may be 2 to 70 microns. The Vi-Cell automated instrument offers many significant advantages for cell analyses in today's busy laboratory environment.