Using Mouse Models To Define How The P53 R72P Polymorphism Impacts The Adverse Effects Of Doxorubicin And Ionizing Radiation

Author

Emily Dominguez, The University of Texas MD Anderson Cancer Center UTHealth Graduate School of Biomedical SciencesFollow

Date of Graduation

12-2016

Document Type

Dissertation (PhD)

Program Affiliation

Epigenetics and Molecular Carcinogenesis

Degree Name

Doctor of Philosophy (PhD)

Advisor/Committee Chair

David Johnson, PhD

Committee Member

Mark Bedford, PhD

Committee Member

Rick FInch, PhD

Committee Member

Donna Kusewitt, DVM, PhD

Committee Member

Kevin McBride, PhD

Abstract

The single nucleotide polymorphism (SNP) at codon 72 of the tumor suppressor gene p53 codes for either an arginine (R) or proline (P) (p53 R72P). This SNP may impact how cells respond to genotoxic insult. Studies in cell culture and in tissues from mouse models of the SNP indicate that, in response to gentoxic treatment, the two variants may differentially induce apoptosis and expression of p53 target genes. In epidemiological studies, the P variant is associated with decreased cancer survival and increased risk of side-effects from genotoxic cancer treatment. Genotoxic therapy is still the mainstay of cancer treatment, and doxorubicin and/or ionizing radiation (IR) are used in many treatment regimens. In this project I employed our mouse models of the p53 R72P polymorphism to test how this SNP modulates physiological effects of doxorubicin and IR. To test how the p53 R72P polymorphism affects doxorubicin tolerance at a physiological level and in gene expression profiles, I performed blood counts and RNA sequencing of tissues from doxorubicin treated and untreated p53 R72P mice. To test how the p53 R72P polymorphism affects IR tolerance, I performed a survival study, immunohistochemical (IHC) staining, blood counts and used quantitative PCR to analyze p53 target gene expression in IR treated and untreated p53 R72P mice. In both studies I stringently controlled for background strain, age and sex. Due to an unexpected tolerance to doxorubicin in the FVB mouse strain employed, the doxorubicin studies were inconclusive. While IR did elicit a significant response, my findings did not support a role for the p53 R72P polymorphism in modulating the adverse effect IR therapy, and indicate that personalization of these therapies based on this SNP could have limited clinical utility.

Keywords

mouse models, p53, single nucleotide polymorphism, genotoxins