Directly to content
  1. Publishing |
  2. Search |
  3. Browse |
  4. Recent items rss |
  5. Open Access |
  6. Jur. Issues |
  7. DeutschClear Cookie - decide language by browser settings

Common mutations in the tumor suppressor p53 & the oncogene Kras as targets for long peptide anti-cancer vaccination

Quandt, Jasmin

[img]
Preview
PDF, English (Titelblatt, Abstract, Table of Content) - Supplemental Material
Download (154kB) | Terms of use

[img]
Preview
PDF, English - main document
Download (12MB) | Terms of use

Citation of documents: Please do not cite the URL that is displayed in your browser location input, instead use the DOI, URN or the persistent URL below, as we can guarantee their long-time accessibility.

Abstract

Tumor-associated antigens (TAAs) are promising targets for immunological therapeutic intervention in cancer therapy. Particularly, mutated proteins are a source for true tumor-specific antigens (TSAs) because they are exclusively expressed in the tumor and are not shared with normal tissue. Moreover, TSAs reduce the risk of autoimmunity and increase the chance to overcome tolerance compared to non-mutated protein sequences. In this study we sought to show for the first time, that a mutation-specific multi-peptide vaccine, which targets simultaneously common mutations in gastrointestinal tumors in a human HLA context, is capable to induce multifunctional and polyvalent CD4+ and CD8+ effector T cell responses with a tumor-protective capacity. Furthermore, we aimed to investigate whether this strategy results in immune-suppressive counter-reactions, like the induction of regulatory T cells (Treg). As target-antigens, we created a panel of peptides with sequences derived from the most frequently mutated variants of the tumor suppressor p53 and the oncogenes Kras and Braf described for colorectal (CRC) and pancreatic carcinomas. More precisely, the peptides represent wild-type (wt) or mutated sequences and have a length of 28-35 amino acids to facilitate a presentation of MHC I and II epitopes. In the presented study we analyzed the potency of the long peptide panel for active vaccination and its tumor-protective capacity in a murine cancer model system. For this purpose we utilized C57BL/6J mice, as well as an HLA-class I/II humanized mouse strain (HLA.A2/HLADR1 transgenic), in a multi-peptide vaccination setting. T cell responses of immunized mice were monitored by flow cytometry measuring cytokine secretion after antigen-specific in vitro re-stimulation. Thereby, we observed simultaneous, polyvalent CD8+ cytotoxic and CD4+ helper T cell responses against the majority of the peptides. Moreover, the peptide-specific T cells possessed a multifunctional cytokine-secretion profile and CD4+ T cells displayed a TH1 like phenotype. Notably, two of the mutation-comprising long peptides (Kras G12V and p53 R248W) induced a significantly higher secretion of cytokines than the corresponding wt sequences in both CD4+ as well as CD8+ T cells, which implied mutation-specificity. For these two peptides we were able to revalidate (Kras G12V) and identify (p53 R248W) HLA.A2 and HLA.DR1 restricted mutation-comprising epitopes. To investigate the tumor-protective capacity of the vaccination approach syngenic fibrosarcoma cell lines were generated in the HLA-class I/II transgenic mouse model by carcinogen-induced tumorigenesis. In tumor challenge experiments we employed cell lines carrying intrinsic Kras/Tp53 mutations and cell lines which were engineered to express the most immunogenic mutations found in our vaccination studies. Vaccination with mutated long peptides resulted in delayed tumor outgrowth compared to vaccination with wt counterparts regarding tumors with intrinsic mutations. However, animals vaccinated with highly immunogenic wt and mutated peptides showed a strong increase of immunosuppressive, peripheral Treg numbers correlating with an accelerated outgrowth of transgene-expressing tumors. In conclusion, we showed that long peptide vaccination targeting multiple mutated oncogenes and tumor suppressor genes is capable of eliciting polyvalent, multifunctional, and mutated antigen-specific effector T cells responses, which have the potential to eradicate tumor cells. Furthermore, we suggest the induction of immune-suppressive, possibly mutation-specific regulatory T cells as a critical issue for the success of this therapeutic approach.

Item Type: Dissertation
Supervisor: Beckhove, Prof. Dr. Philipp
Place of Publication: Heidelberg
Date of thesis defense: 5 November 2014
Date Deposited: 17 Nov 2014 09:52
Date: 2014
Faculties / Institutes: The Faculty of Bio Sciences > Dean's Office of the Faculty of Bio Sciences
Subjects: 500 Natural sciences and mathematics
About | FAQ | Contact | Imprint |
OA-LogoDINI certificate 2013Logo der Open-Archives-Initiative