The force awakens : exploring and translating the role of kynurenine in tumor tolerance
Cancer is a critical public health issue in the United States and immunotherapy has emerged as a breakthrough in providing innovative care to patients. Many cancers evade immune detection by altering the ratio of serum L-tryptophan (L-Trp) to L-kynurenine (L-Kyn), an intermediate in tryptophan catabolism that inhibits antitumoral immunity. Earlier, the Georgiou lab demonstrated that administration of P. fluorescens kynureninase (PƒKYNU) results in systematic L-Kyn depletion, thereby relieving immune suppression and inhibiting in vivo tumor progression. However, PƒKYNU has low amino acid identity to the native human kynureninase enzyme, and is likely to be immunogenic, and therefore unsuitable for human therapy. Unfortunately, the human kynureninase (HsKYNU) has poor catalytic activity for the hydrolysis of L-kynurenine. In the first part of this dissertation, I describe my engineering efforts of the Mucilaginibacter paludis kynureninase (MpKYNU), which has higher homology to the human enzyme. In parallel, I performed in vitro studies to gain insight into how L-Kyn affects T cells and specifically how it creates immunosuppression through the induction of non-classical regulatory T cells, thereby contributing to a critical gap of knowledge in the field while advancing our understanding of KYNU’s therapeutic efficacy.