Generation of an in vitro Intratumoral Heterogeneity Model by Lentiviral Fluorescent Labeling of Colon Cancer Cell Line DLD-1 Subclones

Purpose: Studying genomic changes during tumor progression has helped to understand the biology of many different cancers and has been the basis for targeted therapy strategies. However, resistance and differences in response to therapy in patients are still very important issues. One of the major underlying reasons is intratumoral cellular heterogeneity. Clones harbor mutations and/or epigenetic patterns providing a survival advantage under changing micro-environmental conditions are the main culprits of therapy resistance. Therefore, it is crucial to define and to study the properties and the contributions of these deviant subclones in vitro. In order to achieve that, we have generated a fluorescent intratumoral heterogeneity model of the colon cancer cell line DLD-1. Methods: We used 2N subclones (C3 and C34) and 4N subclones (B9 and B12) of DLD-1, isolated by our team previously. Subclones were stably transduced using lentiviral vectors carrying different fluorescent labels and selected by puromycin. Results: Labeled subclones were mixed in equal proportions and a co-culture model of intratumoral heterogeneity was generated. Fluorescent signals were then confirmed by fluorescence microscope. Conclusion: The in vitro model we have generated may be used in many tumor kinetic studies. By co-culturing different clones, profiles that have a selective advantage under different conditions can be detected. After exposure to different chemotherapeutic agents, radiation and/or combinations, real time changes in population kinetics can be tracked. By comparing these results to the genomic profiling of subclones, it will be possible to relate variations that are responsible for any observed therapeutic resistance in vitro.