Therapeutic resistance is a significant challenge in cancer treatment and is unfortunately a byproduct of said treatment. Although therapies kill the majority of cancer cells, they also leave behind resistant cells that proliferate to reconstitute the cancer and ultimately kill the patient. Current sequencing techniques do not give us the ability to track individual cancer cells that contribute to resistance. Genetic barcoding is a potential solution to this problem. The goal of this project was to use the ClonTracer barcoding system to label HCC827 (lung adenocarcinoma) cells, so that we could follow how a tumor changes in response to therapy and identify which populations of mutant cells contribute to drug resistance. From the work we have done so far, we have been able to successfully barcode the HCC827 cells, such that each cell has a unique barcode. Further experiments are needed to fully optimize the barcoding process. Once optimization is complete, we will then plan on exposing the HCC827 cells to various concentrations of Gefitinib, a targeted cancer therapy, in hyperflasks to scale up our cell populations to more realistically model those found in tumors. This future work will allow us to determine whether ClonTracer is a reliable tool in modeling therapeutic resistance and will hopefully provide us insight on how to better treat cancer in a way that addresses the issue of therapeutic resistance.