Oral Presentation 24th Annual Lorne Proteomics Symposium 2019

In depth definition of the immunopeptidome in haematological malignancies and its potential for immunotherapy (#8)

Kirti Pandey 1 , Nicole A Mifsud 1 , Sri R Ramarathinam 1 , Anthony W Purcell 1
  1. Infection and Immunity Program and Department of Biochemistry and Molecular Biology, Monash Biomedicine Discovery Institute, Monash University, Clayton, Victoria, Australia

Introduction – Haematological malignancy (HM) is an umbrella term used to refer to neoplasms originating from haematopoietic and lymphoid tissues. These clinically manifest as leukaemia, including Acute Myeloid Leukaemia (AML), which is characterised by an increase in blasts cells in the bone marrow. Despite recent successes in cancer immunotherapy involving checkpoint inhibitors and CAR T cell therapy in cancers including Hodgkin lymphoma and Melanoma, the success of these therapies is limited in HM. This makes it imperative to identify new targets for HM, which can be used in T-cell based vaccine therapies. The aim of this study was to define the HLA ligandome associated with AML and thereby identifying leukaemia-specific peptide antigens that include peptides derived from tumour-specific antigens and those bearing novel post translational modifications (PTM) involving phosphorylation and methylation. Methods- 1 X 109 cells of human AML cell line, THP-1 (HLA-A*02:01, -B*15:11, -C*03:03) were lysed and native HLA-peptide class I complexes purified by immunoaffinity chromatography and analysed using liquid chromatography and tandem mass spectrometry (LC-MS/MS). The experiment was performed using biological triplicates. Results – A total of 19,624 HLA-A*02:01 bound peptides along with 17,993 combined HLA-B*15:11 and HLA-C*03:03 bound peptides were identified from the triplicate dataset. Of note, many of the peptides were derived from pathways known to be dysregulated in AML, including Ras and Notch pathways. A number of tumour-specific or associated antigen derived peptides, including peptides from known oncogenes such as Retinoblastoma, A-raf and B-raf were found (n=6). Moreover, PTM peptides including phosphopeptides from upregulated or dysregulated signalling cascades (n=292) and methylated peptides (n=52) were also identified. Conclusion - This study identified naturally presented AML-specific and associated peptides, which will aid in development of improved diagnostic and patient stratification tools and novel peptide based immunotherapeutic approaches.