(P 252) NUCLEAR AND GENOMIC ORGANIZATION OF CHEMOTHERAPY RESISTANT RHABDOMYOSARCOMA CELLS

Objective: The pediatric tumor rhabdomyosarcoma has seen relatively modest improvement in survival rates in the past few decades, particularly in the case of metastatic and recurrent disease. Novel understanding of chemoresistance in these tumors could lead to novel approaches to manage such tumors and thereby improve survival. Organization of the genome and the manner in which chromatin is packed in space has been demonstrated to be related to chemoresistance in certain types of adult tumors, but is less understood in pediatric tumors. Our overall goal is to compare multiple aspects of the nuclear and genomic organization of rhabdomyosarcoma cells across a range of degrees of chemoresistance with the goal of finding novel therapeutic targets.

Methods: Publicly available rhabdomyosarcoma cell lines were serially exposed to increasing concentrations of chemotherapeutic agents in their media to generate progressively more chemoresistant cell lines. Quantitative assessment of chromatin packing for individual nuclei was performed using partial wave spectroscopic imaging of live cells. Nuclear size and morphology were assessed using the program Cellprofiler. Nuclear positioning of genomic loci were assessed using fluorescent in situ hybridization and analyzed with Cellprofiler.

Results: To date, our results demonstrate that exposure to even relatively low concentrations of a single chemotherapeutic agent cause significant changes in chromatin packing, as assessed by changes measured by partial wave spectroscopic imaging.

Conclusion: Changes in chromatin packing in response to chemotherapy drug exposure are largely sustained across a range of chemotherapy drug concentrations, suggesting that even small doses of chemotherapeutic agents can cause wide-scale changes in rhabdomyosarcoma chromatin packing, thereby potentially influencing the activity of numerous other genes.