Date of Award

Spring 2021

Degree Type



College of Pharmacy

Director of Thesis

Dr. Phillip Buckhaults

First Reader

Dr. Carolyn Banister

Second Reader

Dr. Carolyn Banister


The human TP53 gene codes for a protein, p53, that regulates DNA repair and the cell cycle [9]. Therefore, TP53 plays an immensely important role in the proper growth and division of human cells. Mutations in TP53 are also associated with resistance to many standard cancer treatment drugs [6]. More than 50 percent of human cancers have mutations within TP53; it has become a major focus over the years in cancer research [10]. Organoids are in vitro cultures of primary cells established from human surgical samples [8]. They recapitulate genetics of human cancers better than do cell lines [14]. Some organoids in our lab were established from tumors that have a functional TP53 gene or are TP53 wild type (WT). Other organoids are from tumors that are TP53 mutant and have no functioning TP53 gene or p53 protein. The goal of this experiment was to figure out what chemotherapy drug sensitivity differences are caused by absence of functional TP53 gene, and therefore absence of p53 protein. To do this, our lab has used CRISPR/Cas9 gene editing technology to create TP53 knock out (KO) derivatives of TP53 WT organoids. This is called an isogenic pair of organoids, because they are identical to each other except for the TP53 KO that we engineer into the cells. Differences between the WT and KO cells’ sensitivities to various cancer drugs can be solely attributed to the absence of functional TP53 gene, and not some other genetic difference between the cells. Overall, this experiment proved that colorectal cancer (CRC) organoids without a functional TP53 gene are more resistant to the cancer drugs Nutlin-3A, 5-Fluorouracil (5-FU), 6-Thioguanine, Irinotecan, Decitabine, and Thiotepa.

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© 2021, Clare McTighe