26P - Identifying novel cancer antigens using immunoproteomics

Date 20 November 2015
Event ESMO Symposium on Immuno-Oncology 2015
Session Welcome reception and general Poster viewing
Topics Cancer Immunology and Immunotherapy
Presenter Muneerah Smith
Citation Annals of Oncology (2015) 26 (suppl_8): 5-14. 10.1093/annonc/mdv514
Authors M. Smith, J. Blackburn
  • Integrative Biomedical Sciences, University of Cape Town Groote Schuur Hospital, 7925 - Cape Town/ZA

Abstract

Aim

The Blackburn lab has developed a highly sensitive and selective native cancer-antigen (CT100+) microarray, housing 123 tumour-specific antigens (TSA), for cancer diagnosis using patient blood. Although technically advanced, the microarray has biological limitations as we observed a random antibody response in 10-20% of patients. Our aim is therefore to use immunoproteomics to identify TSAs which can reproducibly be used for cancer diagnosis and prognosis.

Methods

We have an archive of 67 cancer and normal tissues, with corresponding autologous sera, from patients with colorectal cancer (CRC) (Groote Schuur Hospital, South Africa) for identifying novel TSAs. For each patient, we have a range of clinical information including their MSI status, inflammation status, cancer stage, family CRC history, etc. We have, thus far, developed an immuno-pulldown assay, in which Protein A and Protein G magnetic microbeads are used to selectively capture antibodies from the patient sera. The Ig-bound microbeads were incubated with native cancer and control tissue lysates to capture antigens. After performing an on-bead tryptic digestion, the peptides were eluted and proteins were identified by mass spectrometry, using a QExactive mass analyser.

Results

In total, 1276 proteins were identified of which 360 were unique to cancer. Eight of the 360 cancer-unique proteins were matched to the Tantigen database, a data source and analysis platform for cancer vaccine target discovery focusing on human tumour antigens that contain HLA ligands and T cell epitopes. Furthermore, we found the most abundant cancer-specific protein to be elongation factor 2, a protein previously reported in CRC patients to result in an antibody response, supporting evidence that the IP assay developed captured cancer antigens.

Conclusions

In conclusion, we have optimised an immuno-pulldown assay to capture and identify cancer antigens from CRC tissues using autologous sera. Our next step is to assay the remaining samples to identify additional TSAs associated with disease diagnosis and prognosis. The newly identified TSAs will then be fabricated on the CT100+ microarray, and validated with patient sera to confirm the presence of cancer-specific antibody response.

Clinical trial identification

Disclosure

All authors have declared no conflicts of interest.