Childhood cancer survivors have an increased risk of developing a second (non-relapse) malignancy, which is a major cause of long-term mortality in these children. It is therefore important to develop treatment strategies that aim to prevent carcinogenesis in patients. To achieve this, we need to first understand the mechanisms underlying the development of second malignancies. My research focuses on the etiology of therapy-related malignancies in pediatric cancer survivors. Using multiple experimental approaches, I investigate the mutational effects of predisposition alleles and different mutagenic/therapeutic agents.