Tumor Immunology The ultimate goal of Tumor Immunology Induction of clinically effective anti-tumor immune responses in patients with pre-existing tumors

Types of Cancer Carcinoma: Cancer of endo or ectoderm e.g. Skin or epithelial lining of organs Sarcomas: Cancer of mesoderm e.g. bone, muscles Leukemias and Lymphomas: Cancers of hematopoietic cells

Cell Growth Control of cell growth Growth- promoting Proto-oncogenes Growth-restricting Tumor-suppressor genes

Molecular Basis of Cancer Uncontrolled cell growth Proto-oncogenes Tumor-suppressor genes Mutations Radiation Chemicals Virus

Syngeneic (accepted) Allogeneic (rejected) Inbred: repeated brother- sister matings Outbred: normal population Xenogeneic (rejected)

Ags expressed on tumor cells Major Histocompatability Complex antigens TAVA TSTA TADA TSTA: unique to a tumor plays an important role in tumor rejection. Tumor-specific transplantation Ag Tumor associated developmental Ag Tumor associated viral Ag

Chemically induced cancers Each tumor induced by a carcinogen expresses a unique Ag. Thus difficult to develop vaccine.

Tumor-Associated Developmental Ags Found on cancer cells and on fetal cells. Do not trigger anti-tumor immunity. Used in diagnosis. Alpha-fetoprotein(AFP) Cancers of liver Carcinoembryonic Ag (CEA) colorectal cancer

Other Tumor associated antigens Silent gene-encoded Ags e.g. Thymic leukemic antigen (Tla) expressed in thymocytes of some strains Differentiation Ags: B cells produce surface Ig. B cell tumors have sIg Melanomas and melanocytes express MART-1 Overexpression of Ag on tumors compared to normal cells e.g. In Breast cancer, HER2/neu homologous to Epidermal Growth Factor Receptor (EGFR)

Abnormal posttranslational modifications. Underglycosylated mucin (MUC-1) e.g. breast cancer Ags expressed on male germ cells (lack MHC) and melanoma e.g. MAGE-1

UV-induced tumors >800,000 cases of skin cancer/year. UV radiation--->most serious skin cancer--->melanomas Highly immunogenic.

Evidence for the role of immune system in tumor rejection Spontaneous regression Regression of metastases after removal of primary tumor Regression after chemotherapy Infiltration of tumors by lymphocytes and macrophages Lymphocyte proliferation in draining lymph nodes Higher incidence of cancer after immunosuppression, immunodeficiency (AIDS, neonates), aging, etc.

Immunity against tumors tumor macrophage T helper (Th) cell B cell

tumor CTL tumor Ag Class I MHC NK

FasL Fas CTL Tumor Perforin/ granzyme NK Apoptosis

T lymphocytes CD4 CD8 T helper T cytotoxic Tumor ClassI MHCClassII MHC Ag v Produce factors that activate other cells to kill tumor cells v Directly kill Cl II+ tumor cells Lyse tumor cells T cell receptor (TCR)

Role of CTL TSTA is processed and presented with Class I MHC to CTL CTL produce FasL or perforin/granzyme which kills the tumor cell. If tumor cells are Fas+ve, CTL will use FasL to kill tumor cell apoptosis.

Role of Th cells TSTA shed by cancer cells, is processed and presented by B cells or macrophages to Th cells Th cells will activate B cells or macrophages by producing cytokines. Abs are not very effective against cancer except against retrovirally induced tumors. Activated macrophages can kill the tumor cells.

B Lymphocytes sIg Tumor Complement Natural Killer cell/ Macrophage/ Granulocyte FcRFabFc Tumor Ab dependent cell cytotoxicity(ADCC) Ag

Role of NK cells NK cells can recognize MHC -ve tumor NK cells are large granular lymphocytes (LGL) TCR -, asialoGM + or NK It is not known exactly how NK cells recognize tumor cells. Lyse virally-infected cells and tumor cells Spontaneous cytotoxicity/ADCC Activity increased by interleukin (IL)- 2 = lymphokine-activated killer cells (LAK) They use FasL and perforin to kill tumor cells.

Macrophages  Normal M  not tumoricidal  Activated M  are tumoricidal  Direct cytotoxicity or ADCC  Reactive oxygen intermediates (O -, H 2 O 2 )  Nitric oxide (NO)  Tumor necrosis factor (TNF)  Lysosomal enzymes  Antigen processing and presentation

Evidence for Immunologic Defenses Against Cancer in Humans Immune cells around tumor mass Hyperplasia of local lymph node Increment of MHC class II and ICAM-1 Immunodeficiency is associated with increased incidence of cancers - B-cell lymphomas AIDS Transplant patients

The 10 leading Causes of Death in the US

Tumor Immunology Characterization of tumor antigens Immune responses to tumors Evasion of tumor from immunosurvillance Immunotherapy

Immunologic Defenses Against Cancer in Experimental Animals Tumors induced by the same virus express the same virally determined antigens Tumors induced by the same chemical are antigenically distinct If a tumor is removed from a mouse, and the mouse later re-injected with the same tumor cells, no tumor will form

What are the Antigens Expressed on Tumors? Tumor Specific Antigens (TSA) –Are only found on tumor cells. –Arise due to point mutations or rearrangement of cellular genes. –Can be derived from viral antigens of transforming viruses. Tumor Associated Antigens (TAA) –Found on both normal and neoplastic tissue, but the expression is greatly altered/increased on cancer cells. –Oncofetal antigens are developmental antigens which become derepressed. (CEA and AFP) –Differentiation antigens are tissue specific. –Altered modification of a protein could be an antigen.

Tumor Immunity -Tumors express antigens that are recognized as foreign by the immune system of the tumor-bearing host -Immune responses frequently fail to prevent the growth of tumors -The immune system can be stimulated to effectively kill tumor cells and eradicate tumor

Tumor Immunity Innate Immunity Macrophage Natural killer cells Adaptive Immunity CTLs Antibody

Macrophages –are activated by IFN  –kill target cells by releasing TNF , radical oxygen species, NO, and proteases Innate immune system I

Natural Killer Cells (NK cells): –can mediate cytotoxicity of cells which have down-regulated their MHC I –part of the innate immune system; involved in immune surveillance –mediate cytotoxicity by using perforin and granzymes, Fas L, and IFN  –NK deficient animals have a higher incidence of neoplastic disease II

Innate Immunity : NK cells

Adaptive Immunity Cell-mediated immunity CD8 + CTLs Humoral immunity Antibody activating complement ADCC (macrophage, NK cell)

Tumor Immunity

The Humoral Immune System What role does it play? Antibodies may bind antigens on the tumor. This may result in: –complement fixation on the tumor cell –antibody dependent cytotoxicity by NK cells, macrophages and CD8 + killer T cells

Antibody Effector Functions Carter P., Nature Rev Cancer.2001;1:

Mechanisms of Immunologic Cytotoxicity Macrophage-mediated cytotoxicity Natural killer cell-mediated cytotoxicity T cell-mediated cytotoxicity Antibody-dependent cell-mediated cytotoxicity Complement-mediated cytotoxicity

How Does the Tumor Evade the Immune System? Low immunogenicity: low expression of adhesion molecules, MHC, co-stimulatory molecules, tumor antigens Antigen: the tumor may not express antigen against which the immune system is reactive. mutation of tumor antigens and antigen masking Immunosuppression: tumor cells may make compounds that suppress immune cells (MHC class 1). TGF-  Speed of tumor growth: may outpace the immune system Antigen released: may saturate the TCRs of T cells or released immunoglobulins

MAC MHC II MHC I APC T helper cell T helper 2 cell IL-2 B Cell Eosinophil IL-4 IL-5 T helper Memor y cell T helper Effector cell IL-1 T cytotoxic cell T cytotoxi c memory cells T cytotoxic effector cells Perforins, apoptotic signals Interferon 1 Cancer Cell T cytotoxic cell Endogenous antigen Perforins, apoptotic signals Generally ineffective tumor surveillance, but some ADCC Tumor antigen or tumor cell SUMMARY

Cancer Immunotherapy Active Immunotherapy Adjuvants Cancer vaccines Cytokines Passive Immunotherapy Monoclonal antibodies In vitro-activated LAK

Adjuvants Inflammatory substances BCG (macrophage activator) Polyclonal activators of T-lymphocytes anti-CD3 antibody (low dose)

Cancer Vaccines Abbas,Lichtman and Pobber, Cellular and Molecular Immunology. W.B. Saunders Fig. 17-5

Cytokines IL-2  increment of LAK and NK activity TNF, IL-1 and IFN-gamma TNF toxic in high level IFN-alpha increment of NK activity and augmentation of MHC class I expression IFN-gamma increment of NK and macrophage activities and augmentation of MHC expression

MHC & Adenovirus- Induced Tumors

Cancer Immunotherapy Active Immunotherapy Adjuvants Cancer vaccines Cytokines Passive Immunotherapy Monoclonal antibodies In vitro-activated LAK

Monoclonal Antibodies

Cancer Immunotherapy Active Immunotherapy Adjuvants Cancer vaccines Cytokines Passive Immunotherapy Monoclonal antibodies In vitro-activated LAK

Treatment of Melanoma with LAK cells +IL-2 BeforeAfter