TUMOR IMMUNOLOGY

• MORE THAN 100 VARIOUS TUMOR TYPES• MULTISTEP TUMORIGENESIS • DYNAMIC CHANGE OF TUMOR GENOME

– Genetic instability– Oncogenes – ‘gain of function’ change– Tumor suppressor genes – recessive ‘loss of function’ change

• PROGRESSIVE TRANSFORMATION– Benign tumor abnormal, but limited growth– Malignant tumor unlimited growth, break basal membranes,

invasion – Metastatic tumor seeds new tumors at distant sites.

• MULTIPLE LIMITING AND INHIBITORY CHECK POINTS– Growth advantage– Selection

• REGULATORY CIRCUITS– Inherent cell autonomous regulatory mechanisms – Microenvironmental factors

Cancer is a result of multiple mutations

INDEPENDENT OF THE IMMUNE SYSTEM

Benign or malignant tumors

ACTIVATION OF ONCOGENESMitogens

Growth factor receptors Secondary messengers

Tarnscriptional activators Cell cycle genes

INACTIVATION OF TUMOR SUPPRESSOR GENES

Growth inhibitors Cell cycle inhibitors

Programmed cell death genes DNA repair enzymes

Unlimited proliferationSustained angiogenesis

Tissue migration and metastasis

ACQUIRED PROPERTIES

Independent growth factor signalsResistance to growth inhibitory factors

Avoid apoptosis

Hanahan D és Weinberg RA 2000 Cell

Tumor stem cell

Tissue cell

Malignant cell

Malignant transformation

Normal epithelial cells2 APC mutation

Inherited

Adenomatous polip

1 Ras mutation

Adenomatous polip

2 p53 mutation

Colon carcinomaChromosomaltranslocation

Metastatic colon carcinoma

The „multi-hit” model of tumorigenesis

Knudson A.G. 2001

Reaction of the immune system

TOLERANCE

RECOGNITIONTumor antigens

Individual TSA

Common TAACEA

TOLERANCEIMMUNE

RESPONSE

DANGER

INNATE/AQUIRED IMMUNITY

Oncogenesis

Mechanism Action Example

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 interaction APC

Loss of down-regulation of growth promoting signal transduction NF-1

Loss of regulation of cell cycle activation through sequestation of transcriptional factors Rb

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 apoptosis bcl-2

Oncogene Associated 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

CHROMOSOMAL TRANSLOCATION IN BURKITT’S LYMPHOMA

Uncontrolled proliferation due to the activation of c-myc oncogene

EBV induced tumor

8 14 8q- 14q+

c-myc

CHVHc-myc

CHVH

THE IMMUNE RESPONSE TO TUMORSHidden, 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 ANTIGENSTumor associated antigens – TA

Present also in normal cellsAberrant/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

About 2/3 of HungaryPopulation half million

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 expressionMany 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• 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 – • Simian virus 40, a polyomavirus that is found in both monkeys and humans. (Large

T-antigen, binds and inactivates p53)• Herpes, EBV- LMP protein strongly trasforming. Homologue of CD40• Papilloma HPV16 HPV18• 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

• TISSUE-SPECIFIC DIFFERENTIATION ANTIGENS – CD10/CALLA Common Acute Lymphoid Leukemia Antigen, Melanoma

macrophage

DS

NK/γδ

CD4/CD8

PROTECTION

ELIMINATIONImmunsurveillence

EQUILIBRIUM ESCAPE

Genetic instabilityImmune selection

Treg cells

TUMORCD8

CD8

macrophage

DS

NK/γδ

CD4/CD8 METASTASIS

ESCAPING TUMOR VARIANTS

Activation of tumor-specific T-cells by DCCross-presentation

M HC II

CD8+

Tc

IL-12

CD4+

T 1H CD40LCD40L

CD40 B

INDUCTION OF A PROTECTIVE ANTI-TUMOR IMMUNE RESPONSE REQUIRES THE COLLABORATION OF DENDRITIC CELLS AND T-

LYMPHOCYTES

IL-2

IFN

Tumor Ag

CROSS PRIMING

TUMOR

APOPTOTIC TUMOR CELL

PS

OxidationICAM-3

HSP

Carbohydrate

TNFIFN

M HC I

APC

CD40

DC

IL - 12

Cytotoxic T-lymphocytesrecognize tumor cells

Activated cytotoxic T-lymphocyteskill tumor cells

CONSEQUENCES OF T-CELL MEDIATED IMMUNITY

Manipulation of the immune response by a tumor.

C 4+

DCD40L

IDCDC2

CD8+

Tc

M

IL-10

CD4+CD25+

CD4+

reg

TOLERANCE INDUCTION BY DENDRITIC CELLS

SIGNAL 1 Tumor antigen YES

SIGNAL 2 Tumor cell NO

Activated APC YES

SIGNAL 3 Natural immunity NO

Inflammation NO

Tumor-associated macrophage (upto 40% of non-malignant cells)

M1 macrophage: MHCII, CD80, 86High 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

Vaccination of melanoma patients may cause their tumor to regress

AZ AKTÍV TUMOR-SPECIFIKUS IMMUNTERÁPIA LEHETŐSÉGEIA tumor antigének beviteli módja

Tumor protein

Tumor protein-derived peptide Anti-idiotipe Ab

Vírus-tumor genome

Plasmid DNAModified tumor cell

Irradiated tumor cell

Heat shock protein

Modified DC

Mocellin S et al. Lancet Oncology 2004

Tumor cell lysateLoaded DC

ANTI-TUMOR IMMUNOTHERAPY

Humanized monoclonal antibodies used in the treatment of patients with cancer.

DIAGNOSIS OF TUMORS BY PET