TUMOR IMMUNOLOGY

MORE THAN 100 VARIOUS TUMOR TYPES MULTISTEP TUMORIGENESIS DYNAMIC CHANGE OF TUMOR GENOME –Genetic instability –Oncogenes – dominant ‘gain of function’ change –Tumor suppressor genes – recessive ‘loss of function’ change PROGRESSIVE TRANSFORMATION –Pre-malignant –Malignant –Metastatic MULTIPLE LIMITING AND INHIBITORY CHECK POINTS –Growth advantage –Selection REGULATORY CIRCUITS –Inherent cell autonomous regulatory mechanisms –Microenvironmental factors TUMORS INDEPENDENT OF THE IMMUNE SYSTEM

ACTIVATION OF ONCOGENES Mitogens Growth factor receptors Secondary messengers Tarnscriptional activators Cell cycle genes INACTIVATION OF TUMOR SUPPRESSOR/STABILITY GENES Growth inhibitors Transcriptional repressors Cell cycle inhibitors Programmed cell death genes DNA repair enzymes Unlimited proliferation Sustained angiogenesis Tissue migration and metastasis ACQUIRED PROPERTIES Independent growth factor signals Resistance to growth inhibitory factors Avoid apoptosis Hanahan D és Weinberg RA 2000 Cell Tumor stem cell Tissue cell Malignant cell Malignant transformation

Normal epithelial cells 2 APC mutation Inherited Adenomatous polip 1 Ras mutation Adenomatous polip 2 p53 mutation Colon carcinoma Chromosomal translocation Metastatic colon carcinoma The „multi-hit” model of tumorigenesis Knudson A.G Reaction of the immune system TOLERANCE RECOGNITION Tumor antigens Individual TSA Common TAA CEA TOLERANCEIMMUNE RESPONSE DANGER INNATE/AQUIRED IMMUNITY

Oncogenesis MechanismActionExample Growth promotion Overexpression of growth factor receptors (such as epidermal growth factor, or EGF) making cells more sensitive to growth stimuli c-erb-B2 Increased growth factor signal transduction by an oncogene that lacks the GTPase activity that limits GTP induction of cytoplasmic kinases that drive cell growth ras Overexpression of a gene product by stimulation from an oncogene (such as ras)c-sis Lack of normal gene regulation through translocation of a gene where it is controlled by surrounding genes to a place where it is no longer inhibited c-abl Binding of oncogene product to the nucleus with DNA transcriptional activation to promote entry into the cell cycle c-myc Loss of tumor suppressor gene function Lack of regulation of cell adhesion with loss of growth control through cell interactionAPC Loss of down-regulation of growth promoting signal transductionNF-1 Loss of regulation of cell cycle activation through sequestation of transcriptional factorsRb Loss of regulation of cell cycle activation through lack of inhibition of cell proliferation that allows DNA repair p53 Limitation of Apoptosis Overexpression of gene, activated by translocation, prevents apoptosisbcl-2

OncogeneAssociated Neoplasms c-erb-B2 Breast and ovarian carcinomas ras Many carcinomas and leukemias c-sis Gliomas c-abl Chronic myelogenous leukemia, acute lymphocytic leukemia c-myc Lymphomas BRCA-1 Breast and ovarian carcinomas APC Colonic adenocarcinomas NF-1 Neurofibromas and neurofibrosarcomas Rb Retinoblastomas, osteosarcomas, small cell lung carcinomas p53 Many carcinomas bcl-2 Chronic lymphocytic leukemia, lymphomas VARIOUS ONCOGENES ARE ASSOCIATED WITH DEFINED NEOPLASMS

Benign or malignant tumors

The first step toward neoplasia is cellular transformation. Here, there is metaplasia of normal respiratory laryngeal epithelium on the right to squamous epithelium on the left in response to chronic irritation of smoking. This is the next step toward neoplasia. Normal cervical squamous epithelium at the left, but dysplastic squamous epithelium at the right. Dysplasia is a disorderly growth of epithelium, but still confined to the epithelium. Dysplasia is still reversible. normal squamous dysplastic squamous normal squamous LARYNGEAL EPITHELIUM CERVICAL The two forms of cellular transformation that are potentially reversible, but may be steps toward a neoplasm, are: Metaplasia: the exchange of normal epithelium for another type of epithelium. Metaplasia is reversible when the stimulus is taken away. Dysplasia: a disordered growth and maturation of an epithelium, which is still reversible if the factors driving it are eliminated.

CHROMOSOMAL TRANSLOCATION IN BURKITT’S LYMPHOMA Uncontrolled proliferation due to the activation of c-myc oncogene EBV induced tumor 8148q-14q+ c-myc CH VH c-myc CH VH

THE IMMUNE RESPONSE TO TUMORS Hidden, changing, proliferating, evolving target Immune surveillence –Few non-self antigens –Poorly immunogenic –Recognized by B and T lymphocytes Tolerance induction –Tumor antigens do exist –Recognized primarily by T lymphocytes –Induce tolerance TUMOR ANTIGENS Tumor associated antigens – TA Present also in normal cells Aberrant/disregulated expression in tumor cells Tumor specific antigens – TSA Unique for individual tumors or tumor types IMMUNE SYSTEM Tumor-specific immune responses can be induced Cytotoxic T lymphocytes can eradicate tumors

MHC-dependent rejection of tumors

Infective facial tumor in the inbread populations of the Tasmanian devil

Tumor antigens and tumor associated antigens

Tumor-specific antigens

Cancer/testis antigens are expressed almost entirely by cancerous cells, showing little or no expression in healthy tissue, with the exception of normal testis, embryonic ovaries and placenta. No MHC expression Many of them X-linked Over 100 in total --- Potential targets for immune therapy

STRUCTURE AND SOURCE OF TUMOR ANTIGENS MUTATED ONCOGENS AND TUMOR SUPPRESSOR GENES –Involved in transformation –Cytosolic novel determinants - no major targets –Cellular proto-oncogenes  oncogene Ras, p53, Abl Point mutation, deletion, chromosomal translocation, viral gene insertion OTHER MUTATED GENES – not required for transformation –Peptides derived from diverse random mutants of host cellular proteins ABERRANTLY OVEREXPRESSED NORMAL CELLULAR PROTEINS –Low/rare expression in normal cell – ignorance by the immune system TUMOR ANTIGENS ENCODED BY GENOMES OF ONCOGENIC VIRUSES –Immunogenic shared viral proteins DNA viruses – Papova, Herpes, Papilloma RNA viruses – Retroviruses HTLV ONCOFETAL ANTIGENS –Silenced during development  de-repressed in tumor cells –Tumor markers – carcinoembryonic antigen CEA, specific for carcinomas –Alpha-fetoprotein AFP, hepatocellular carcinoma ALTERED GLYCOLIPIDS –Ganglioside, blood group related antigens, mucin TISSUE-SPECIFIC DIFFERENTIATION ANTIGENS –CD10/CALLA Common Acute Lymphoid Leukemia Antigen, Melanoma

macrophage DS NK/γδ CD4/CD8 PROTECTION ELIMINATION Immunsurveillence EQUILIBRIUMESCAPE Genetic instability Immune selection Treg cells TUMOR CD8 macrophage DS NK/γδ CD4/CD8 METASTASIS ESCAPING TUMOR VARIANTS

Activation of tumor-specific T-cells by DC Cross-presentation

INDUCTION OF A PROTECTIVE ANTI-TUMOR IMMUNE RESPONSE REQUIRES THE COLLABORATION OF DENDRITIC CELLS AND T- LYMPHOCYTES IL-2 IFN  Tumor Ag CROSS PRIMING APOPTOTIC TUMOR CELL DC IL - 12

Cytotoxic T-lymphocytes recognize tumor cells Activated cytotoxic T-lymphocytes kill tumor cells CONSEQUENCES OF T-CELL MEDIATED IMMUNITY

TOLERANCE INDUCTION BY DENDRITIC CELLS SIGNAL 1Tumor antigenYES SIGNAL 2 Tumor cellNO Activated APCYES SIGNAL 3Natural immunityNO InflammationNO Tumor-associated macrophage (upto 40% of non-malignant cells) M1 macrophage: MHCII, CD80, 86 High iNOS, M2 macrphage: arginase +

TUMOR ANTIGENS –Soluble tumor antigens – inhibit recognition on the cell surface –Antigen modulation – antibody dependent internalization –Masking – antibody binds, no effector function –Low immunogenicity –Peptide antigens – mutations affecting Tc or Th epitopes ANTIGEN PRESENTATION –Direct presentation – non professional APC, no MHC class II, no co-stimulatory molecules –Indirect presentation – by professional APC, soluble CD40 and CD40 ligand inhibit CYTOTOXIC T CELL ACTIVITY –MHC – mutation, altered intracellular transport, β2m, locus, allele –Peptide loading – mutation, tumor derived peptides are not presented, TAP APOPTOSIS –Soluble Fas – inhibits Fas ligand-mediated apoptosis TUMOR DERIVED INHIBITORY FACTORS –TGFβ – G1 block, inhibits tumor growth if sensitive  tumors loose their TGFβ receptor –TGFβ inhibits immune cell activation –PGE2 – immune suppression TUMOR DERIVED POTENTIATING FACTORS –Angiogenesis factors – secreted by tumor tissue cells or by immune cells ESCAPE MECHANISMS OF TUMOR CELLS AND TUMOR TISSUES

Human epithelial tumours can inhibit the response of lymphocytes expressing NKG2D

AZ AKTÍV TUMOR-SPECIFIKUS IMMUNTERÁPIA LEHETŐSÉGEI A tumor antigének beviteli módja Tumor protein Tumor protein- derived peptide Anti-idiotipe Ab Vírus-tumor genome Plasmid DNA Modified tumor cell Irradiated tumor cell Heat shock protein Modified DC Mocellin S et al. Lancet Oncology 2004 Tumor cell lysate Loaded DC ANTI-TUMOR IMMUNOTHERAPY

DIAGNOSIS OF TUMORS BY PET

Vaccination of melanoma patients may cause their tumor to regress