Four main classes of human tumor antigens recognized by T cells: 1- "Cancer-testis" antigens: non-mutated genes reactivated in neoplastic cells, but

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1 Tumor antigens Andrea Anichini Human Tumors Immunobiology Unit, Dept. of Experimental Oncology and Molecular Medicine Fondazione IRCCS Istituto Nazionale dei Tumori, Milan

2 Timeline of the discovery of the genes encoding tumor-associated antigens Four main classes of human tumor antigens recognized by T cells: 1- "Cancer-testis" antigens: non-mutated genes reactivated in neoplastic cells, but generally silenced in normal cells, with exception of male germ line cells and trophoblasts. 2- Tissue-specific self antigens. 3- Neoantigens resulting from nonsynomymous somatic mutations in neoplastic cells. 4- Normal genes overexpressed in cancer cells

3 A single tumor can express all classes of antigens: Tumor-associated antigens in B-NHL Tumor-associated antigens 1-Tumor-specific idiotype. 2-Shared antigens T cell recognition -Somatically mutated lymphoma Ig regions code for peptides recognized by patients T cells as tumor-specific antigens (Gricks 2001)- -non-mutated, germ-line V region sequences code for peptides recognized as shared antigens by patients T cells (Trojan, 2000). 3-B cell differentiation antigens. CD19 and CD20 encode peptides recognized by patients and healthy donors CD8+CTLs. (Grube 2004). 4-Over-expressed -Apoptosis regulators. Bcl-2 peptide-specific T cells in CLL patients (Andersen 2005) -Proteoglycans. Fibromodulin, overexpressed in CLL compared to normal B cells, encodes for peptides recognized by CTLs (Mayr, 2005)

4 Some antigens expressed by human melanoma Class Antigen peptide sequence HLA Cancer testis MAGE1 EADPTGHSY A1 MAGE3 FLWGPRALV A2 NY-ESO-1 SLLMWITQC A2 Mutated CDK4 ACDPHSGHFV A2 proteins β-catenin SYLDSGIHF A24 Cdc27 FSWAMDLDPKGA DR4 tissue specific antigens Tirosinasi YMDGTMSQV A2 gp100 ITDQVPFSV A2 Melan-A/Mart-1 AAGIGILTV A2 Trp-2 LLGPGRPYR A31

5 processing of a single protein can generate several peptides recognized by CD4+ and CD8+ T cells. HER-2 peptides recognized by T cells. HLA-Class II HLA-Class I (a) (b) (c) (d) (e) A33 A24 A11 A3 A Domain I Domain II Domain III Domain IV TM Tyrosine Kinase Regulatory Region Pertuzumab binding site Herceptin binding site bcr (a),(b),(c),(d),(e): distinct HLA Class II alleles and sometimes promiscuous epitopes

6 One gene, several tumor antigens, and different T and B subsets that recognize them HLA Class II CD4 Treg HLA Class I - CD8 - + HLA Class II CD4 TH B +

7 The same protein expressed in neoplastic cells can be target of B and T cells: immune response to tumors is integrated. B cell response T cell response HLA-peptide Comples TCR T T T

8 Biomarkers of response to anti-ctla-4 Pre-existing antibody response and T/B integrated response to NY-ESO-1 associated with clinical benefit to anti-ctla-4

9 How MHC Class I- peptide complexes are generated

10 MHC Class I vs MHC Class II antigen processing pathwyas

11 How the TCR "sees" the MHC-peptide complex CDR CDR peptide TCR-A TCR-B

12 How the TCR "sees" the MHC-peptide complex CDR3 CDR3 peptide

13 Molecular mechanisms that generate antigens recognized by T cells on tumor cells DNA mrna Protein Peptide Peptide Peptide (epitope o agretope*) (cryptic promoter) Peptide 4 (alternative orf) 5 Peptide (intron retention) 6 Peptide (post-traslational modification) *n.b.epitope: part of the peptide that interacts with the TCR agretope: part of the peptide that interacts with the HLA molecule

14 Protein and peptide surgery New mechanisms generate TAA recognized by T cells... Nature 427:252, Vigneron et al. Science 304:587, 2004 An antigenic peptide produced by peptide splicing in the proteasome R T K A W N R Q L Y P E W bibliografia: Science Science 304:587 Nature 427:252 R T K Q L Y P E W

15 Imagine you are in 1996 and you want to clone a tumor antigen

16 Cloning of tumor antigen genes recognized by patients' antibodies: SEREX approach tumor mrna cdna libraries in expression vectors Bacteria Screening by antibodies from patients' serum serex : serological analysis of recombinant cdna expression libraries

17 Antigen classes recognized by B cells and identified by SEREX 1. Cancer testis (CT) ags Mages NY-ESO-1 HOM-Mel-40/SSX2 CT7 SCP-1 BAGE GAGE NW-BR-3 2. mutated genes p53 LKB/STKII 3. amplified/overexpressed genes eif-4γ Carbonic anhydrase XII HER-2/neu 4.splicing variants 5. differentiation antigens (tissue-specific) Fibulin-1 NY-CO-37/PDZ-45 ING-1 NY-BR-1 Tyrosinase Galectin-4

18 Now you are in 2016 and want to identify new tumor antigens NPR1: Atrial natriuretic peptide receptor 1 KLGDFVA TL A TLHRRLGW T cell Rizvi et al. Mutational landscape determines sensitivity to PD-1 blockade in non small cell lung cancer. Science 348: , 2015