Analysis of the T cell repertoire in cancer patients: unveiling the antitumor immune response in humans

Author(s)

Mariana Pereira Pinho

• Document type: Doctoral Thesis
• Press: São Paulo.
• Institution: Universidade de São Paulo (USP). Instituto de Ciências Biomédicas (ICB/SDI)
• Defense date: 2019-07-19

Examining board members

Jose Alexandre Marzagao Barbuto; Niels Olsen Saraiva Câmara; Kenneth John Gollob; Elaine Guadelupe Rodrigues

• Advisor: Jose Alexandre Marzagao Barbuto

Abstract

Tumorigenesis is accompanied by the accumulation of mutations and aberrant expression of various proteins by the transformed cells, which can be recognized by the adaptive immune response in cancer patients. The study of the patients ability to recognize its tumor, specifically of its antitumor T cell repertoire, is of vital importance for a better understanding of the interplay between the immune system and tumors. Therefore, this project aimed to develop an in-depth study of the tumor-reactive T cell repertoire in cancer patients, determining its frequency and response pattern, at different points of disease progression and therapy. To estimate the frequency of tumor-reactive T lymphocytes, comprehensive detection techniques that employ the T cell proliferative capacity against its cognate antigen to determine its specificity were developed. By using such techniques, we could find T cells reactive for mutated antigens (neoantigens) in a patient with hepatocellular carcinoma, and reactive for an overexpressed antigen (Her2) in patients with breast cancer. We also found T lymphocytes reactive for these antigens in healthy individuals, not only in the naïve cell compartment, but also among memory T cells, which adds evidence to the theory of immune surveillance. It is noteworthy that Her2-reactive T lymphocytes could produce cytokines and specifically eliminate cells that overexpressed Her2. The total frequency of tumor-reactive T-lymphocytes in the blood of individuals with breast cancer and with glioblastoma multiforme (GBM) was estimated using tumor cell lysates as antigen source, and it was found to be higher in the blood of breast cancer patients. The frequency of tumor-reactive T cells in patients\' blood did not correlate with that found among T cells infiltrating the tumor, indicating that these may differ significantly. Even so, in two patients, temporal variation in the blood frequency of GBM-reactive CD4 and CD8 T cells correlated with their clinical response to the experimental vaccination with dendritic-tumor cell hybrids. This immune intervention also changed the cytokine production pattern of GBM-reactive CD4 T lymphocytes in the patient tested. As with vaccination, the surgical removal of the tumor also affected significantly the repertoire of GBM-reactive T lymphocytes in the patients, decreasing their frequency and altering their phenotype. Finally, among the breast cancer-reactive T cells, we detected CD8 T lymphocytes with possible suppressive capacity and CD4 T lymphocytes that had protumoral characteristics and whose clones belonged to multiple distinct subpopulations with different helper phenotypes. Altogether, the results of the frequency and function of the tumor-reactive T lymphocytes shown here unveil some tumor immune response characteristics largely unknown, which improve our understanding of the antitumor immune response in humans. (AU)

• FAPESP's process: 14/25988-1 - Analysis of the T cell repertoire in cancer patients: unveiling the antitumor immune response in humans
• Grantee: Mariana Pereira Pinho
• Support Opportunities: Scholarships in Brazil - Doctorate