Immunological aspects of Oral Cancer

Immunological aspects of Oral CancerDr. Aurelian Jovita AlexanderMDSDept. Of Oral and Maxillofacial Pathology

SynopsisIntroduction & terminologies

Immunology

Tumor antigens

Immune responses to tumors

Tumor evasion of immune system

Immunotherapy

IMMUNOLOGYThe branch of biomedical science concerned with the response of the organism to antigenic stimuli, the recognition of self and non-self, and all the biological, serological, and physical chemical effects of immune phenomena.

IMMUNITY- refers to the resistance exhibited by the host towards injury caused by microorganisms and their products

IMMUNE- The word Immune is derived from the Latin term immunitas which means freedom from

Cells of the Immune SystemLYMPHOCYTESProduce specific receptors for antigens and thus key mediators for adaptive immunity. B cells- AntibodyT cells- recognise peptide fragments of protein antigens

Cd4 + T cells- Helper cells, B Lymphoctes- AntibodiesRegulatory T LymphocytesCD8+ T cells- Cytotoxic T cellsNK cells

Antigen Presenting CellsThe common portals of entry of microbes- the skin, gatrointestinal tract and resp tract- contain specialsed APCs located in the epithelium that capture antigens and display them to lymphocytes.Dendritic cellMacrophage

Effector cellThe cells that eliminate microbes are called effector cells and consist of lymphocytes and other leukocytes.B cells- Plasma cellsLeukocytes- Macrophages, Granulocytes

MHCMHC (Major histocompatibility complex) Themajorhistocompatibilitycomplex(MHC) is a set ofcell surface molecules encoded by a largegene familyin all vertebrateswhich controls a major part of the immune system.

HLA (Human leucocyte antigen) Thehuman leukocyte antigen (HLA)system is the locus of genes that encode for proteins on the surface of cells that are responsible for regulation of theimmune systemin humans.

Classgene region Classical HLA classgenes-------HLA-A,B,C Non-classical HLA classgenes-----HLA-E,F,GMHC class chain related genes

Class gene region Classical HLA class genes---HLA-DP,DQ,DR Genes associated with antigen processing

Class gene region Complement genes-----C4,C2,Bf Inflammation-associated genes----TNF,HSP70

Cellular expression of MHC MoleculeCLASS I MHC:Nucleated cellsLymphocytesFibroblasts ,muscle cells, liver hepatocytes, neural cells very low CLASS I molecules.Neurons ,sperm cells-lack CLASS I.

CLASS II MHC:Antigen presenting cells Macrophages Mature dentritic cellsB cellsThymic epithelial cells

MHC 1 Response

MHC 11 Response

CancerCanceror malignant tumours, is a group of diseases involving abnormalcell growthwith the potential to invade or spread to other parts of the body.

Tumour/ NeoplasiaNeoplasm is derived from Greek (neo- "new" + plasm- "formation", "creation")Neoplasia means new growth

Tumor is derived from the Latin word for "swelling

Tumor originally applied to the swelling caused by inflammation

Oncology (Greek oncos = tumor) is the study of tumors or neoplasms

Neoplasm is defined by British oncologist Willis as An abnormal mass of tissue, the growth of which exceeds and is uncoordinated with that of the normal tissues and persists in the same excessive manner after the cessation of the stimuli which evoked the change.

Not capable of indefinite growthDoes not invade the surrounding tissueNo metastasisGrows indefinitelyProgressively invade the surrounding tissueExhibit metastasisTumorsBenign TumorsMalignant Tumors

MetastasisSmall clusters of cancerous cells dislodge from a tumor, invade the blood or lymphatic vessels, & are carried to other tissues, where they continue to proliferate

In this way, a primary tumor at one site can give rise to a secondary tumor at another site

Classification of Malignant tumors-(according to the embryonic origin of the tissue from which the tumor is derived)

Carcinomas- (>80%)Sarcomas- (less frequent -around 1%)Leukemias & lymphomas- (around 9%)

Etiology Of CancerGenetic factors: Mutations.Environmental factors: UV, chemicals, viral infections. Alteration in tumor suppressor genes

Tumour AntigensIf the immune system of an individual is able to react against a tumor in that individual, then the tumor must express antigens that are seen as nonself by that individual's immune system.

Tumor-specific antigens (TSAs)

Tumor-associated antigens (TAAs)

TSAA. Tumors induced with chemical or physical carcinogens (chemically or physically induced tumors express tumor antigens on only one kind of tumor)

B. Some virally induced tumors(virally induced tumors express tumor antigens shared by all different tumors induced by the same virus)

TAA 1. May be proteins usually expressed only on fetal cells but not on normal adult cells. Oncofetal tumor antigens Alpha-fetoprotein (AFP) &Carcinoembryonic antigen (CEA)

2. They may be proteins expressed at low levels by normal cells but at much higher levels by tumor cells. -Tyrosinase, gp 100, Melan-A or MART-1, and gp 75 - GM2, GD2, and GD3

Immune Rejection Responses Against Experimental Tumours in Mice

Proto-Oncogene

Unmutated normal counterpart of the oncogenes.Aproto-oncogeneis a normal gene involved in regulation of normal cell proliferation and can become an oncogene due to mutations or increased expression.Examples of proto-oncogenes includeRAS ,WNT ,MYC ,ERK , andTRK.

Help to regulatecell growthanddifferentiation. Involved insignal transduction and execution ofmitogenicsignals, usually through theirproteinproducts.

Classification of Proto OncogeneGrowth FactorsReceptor Tyrosine KinasesMembrane Associated Non-Receptor Tyrosine KinasesG-Protein Coupled ReceptorsMembrane Associated G-ProteinsSerine/Threonine KinasesNuclear DNA-Binding/Transcription Factors

Growth FactorsThe SIS encodes the PDGF B chain. The int-2 gene encodes an FGF-related growth factor.The KGF (Keratinocyte GF, also called HST) gene also encodes an FGF-related growth factor.

Receptor Tyrosine KinaseThe FMS gene encodes the colony stimulating factor-1 (CSF-1) receptor.The FLG (flag) geneEGFR, also called HER1 for human EGF receptor 1NEU geneTRK genesMET proto-oncogeneKIT gene

Membrane Associated Non-Receptor Tyrosine Kinases

SRC gene- archetypal protein tyrosine kinase.LCK gene- associated with the CD4 and CD8 antigens of T cells.ABL proto-oncogene- in Chronic Myelogenous Leukemia.

G-Protein Coupled Receptors

MAS gene -angiotensin receptor.

Membrane Associated G-Proteins

DBL - involved in the exchange of GTP for GDP in several proteins of the small G-protein classVAV - an exchange factor for RAS

Serine/Threonine Kinases

The RAF gene - responsible for threonine phosphorylation of MAP kinase following receptor activation.The MOS gene (originally identified in the Moloney murine sarcome virus) is normally expressed in germ cells and functions during oocyte maturation.

Nuclear DNA-Binding/Transcription Factors

MYC genes-: MYC, N-MYC, and L-MYC.FOS gene - interacts with a second proto-oncogenic protein, JUN to form a transcriptional regulatory complex.p53 gene

ONCOGENEIt can become an oncogene due to mutations or increasedexpression. The resultant protein may be termed as oncoprotein.Prevent apoptosis.

Traslocations and mutations occur in initial phase.Amplification in Tumour progression.Product of Oncogenes- 6 groups

Transcription FactorsChromatin RemodelersGrowth factorsSignal TransducersGrowth factor receptorsApoptosis Regulators

Transcription FactorsMember of multigene families that share common structural domais.Require interaction with other proteinsEg- Fos transcription protein dimerizes with the Jun transcription factor - AP1 transcription factorIncreases the expression of several genes that control cell division.

Chromatin RemodelersModifications in the degree of compaction of chromatin. Two kinds of enzymes ATP dependent enzymes- move the positions of nucleosomes, the repeating subunits of the histones in chromatin around which DNA winds.Enzymes that modify the N-terminal tails of histonesEg- ALL1 (MLL), EPHA7 gene

Growth FactorsConstitutive activation of a growth factor gene can contribute to malignant transformation.Platelet derived growth factor (PDGF) consists of and chains and is released from platelets during coagulation - induce cell proliferation. FGFTGFHGF

Growth factor receptorsEGFRVEGFFMS like Tyrosine KinaseReceptor for Neutrophic ReceptorsPDGF ReceptorReceptor for Stem cell

Signal TransductionGTP bindingNon receptor Tyrosine KinaseRas signal TransductionWNT signal transduction

Oncogenes in OSCCEGFRTp53PIK3CA- phosphatidylinositol-4,5-bisphosphate 3-kinase, provides instructions for making the p110 protein, which is one piece (subunit) of an enzyme called phosphatidylinositol 3-kinase (PI3K).HRAS - V-Ha-ras Harvey rat sarcoma viral oncogene homolog codes for GTPase HRasalso known asp21.SCCRO / DCUN1D1 (defective in cullin neddylation 1, domain containing 1 (S. cerevisiae))

Cyclin D1Cyclin ARbP16P21P27P34

Ras Myc- V-myc myelocytomatosis viral oncogene homolog (avian)LAZ3/ BCL 6PTK2

Anti-Oncogenes / Tumour Supressor GenesProtects the cell from leading to cancer.

2 main TSG Rb gene and P53The proteins encoded by these genes inhibit cell cycle progression by blocking transcription of gene products necessary for transition from G1 to S phase.P53- induces cell differentiation, promotes apoptosis.

Other TS genes..pVHL - Von HippelLindau tumor suppressorAPC- Adenomatous polyposis coliCD 95ST5 gene- Suppression of tumorigenicity 5YPEL3

Steps in Tumour DevelopmentTumour InitiationTumourProgressionTumour Promotion

Tumour InitiationThe change in the cell's genetic material may occur spontaneously or be brought on by an agent that causes cancer (a carcinogen).

Carcinogens include many chemicals, tobacco, viruses, radiation, and sunlight.

A genetic flaw in a cell may make it more susceptible. Even chronic physical irritation may make a cell more susceptible to carcinogens.

Clonal selectionCellular Expansion

Cell populations with all of the prerequisites for metastatic capacity are the subpopulations that metastasize

Tumour PromotionUnlike carcinogens, promoters do not cause cancer by themselves. Instead, promoters allow a cell that has undergone initiation to become cancerous. The earlier abnormal cells in these two stages are referred to as preneoplastic or premalignant.

Tumour ProgressionSuccessive changes in the neoplasm give rise to increasingly malignant sub-populations.Accelerated by repeated exposures to carcinogenic stimuli.Further gene mutations accumulating within the expanding pre-neoplastic cell clone.

Evasion of Apoptosis

Inhibitors of Apoptosis Proteins

AngiogenesisSolid tumours cant enlarge beyond 1-2mm.Secretion of various GF- bFGF, VEGFNormal Cells- Anti VEGF- PKG - Limits beta cateninBV- Irregular, leaky, dilatedMosaic vessels

Oral cancerIL-8, VEGFTumour MicroenvironmentSecretion of chemotactic cytokines:-CSF-1, GM-CSF, VEGF, Monocyte Chemotactic Protein(MCP)-1, TGFPeripheral Blood MonocyteMacrophagesRelease bfgf, VEGF, TNF, IL-8

Tumour Metastasis

Invasion of local normal tissuesEntry and transit of neoplastic cells in the blood and lymphatic systemsThe subsequent establishment of secondary tumor growth at distant sites

Host defense against TumoursProducts of Mutated genes- Genetic alterations in TSG, P53- represent antigens

Overexpressed or Aberrantly Expressed Cellular Proteins Tumour antigens may be normal cellular proteins abormally expressed in tumour cells

Tumour Antigens produced by oncogenic viruses

Latent DNA virus- HPV, EBVCTLs recognize antigens of these viruses

Oncofetal AntigensProteins in Cancer cells and developing fetus.The two most thoroughly characterized oncofetal antigens are Carcinoembryonic antigen (CEA) -fetoprotein (AFP).

Altered cell surface Glycolipids and GlycoproteinsGangliosides, Blood group antigens, MucinsAmong the glycolipids expressed at high levels in melanomas are the gangliosides GM2, GD2, and GD3Mucins- CA-125 and CA-19-9, expressed on ovarian carcinomas, and MUC-1 on breast carcinomas.

Cell TypeSpecific Differentiation AntigensTumors express molecules that are normally present on the cells of origin.Normal self-antigens, and therefore they do not induce immune response in tumor-bearing hosts.Used for Immunotherapy and identification of the origin.

For example, lymphomas may be diagnosed as B cellderived tumors by the detection of surface markers characteristic of this lineage, such as CD20. Antibodies against CD20 are also used for tumor immunotherapy

Antitumor effector mechanismsCytotoxic T LymphocytesNK CellsMacrophagesAntibody

Tumour evasion of the Immune System

Lack of Co- Stimulation

Myeloid-derived suppressor cellsMDSC accumulate in the tumor microenvironment and suppress T-cell responses.MDSC are bone marrow-derived immature myeloid cells that are increased in frequency in the peripheral circulation, lymphoid organs and tumors of virtually all tumor-bearing hostsThey are recruited by tumor-derived soluble factors, such as TGF-b, IL-10, VEGF, IL-6, PGE2, which directly bind to their cognate receptors on MDSC.

These pro-inflammatory mediators induce tissue accumulations of MDSC and increase their suppressor activity thus favoring tumor growth.

Apoptosis of Activated T Cells

Referred to as activation-induced cell death (AICD) or spontaneous apoptosis.

CD8+ effector T cells relative to CD4+ T cells

Overexpression of Fas (CD95) and crosslinking of this receptor by FasL expressed on human tumor cells

The tumor-mediated down-regulation of the common cytokine receptor c chain (cc) expression in T cells is responsible for their defective signaling and, ultimately, T-cell apoptosis.

Tumour derived MicrovesciclesSera of patients of cancer contain double membrane-bound vesicles called EXOSOMES or microvesicles (MV), ranging in size from 50 to 100 nm.

Express surface and cytoplasmic components of tumor cells from which they originate.

Thus, tumor- derived MV contain TAA and have a molecular profile similar to that of tumor cells but distinct from that of DC or T cell profiles, for example.

Tumor-derived MV arrest proliferation of activated T cells.Down-regulate expression of TCR-associated zeta chain and Jak3 in T cells. They express FasL and/orTRAIL, induce apoptosis of activated T cells.

Exosomes are a potent method of dendritic cell communication with other antigen presenting cells.Mini antigen presenting cell.

Antigen Masking

The cell surface antigens of tumors may be hidden, or masked, from the immune system by glycocalyx molecules, such as sialic acidcontaining mucopolysaccharides.

Antigen ModulationCertain tumor-specific antigens have been observed to disappear from the surface of tumor cells in the presence of serum antibody and then to reappear after the antibody is no longer present.

Tumor Cells Frequently Express Low Levels of Class I MHC Molecules

Cancer Immunotherapy

Cancer ImmunotherapyCancer Vaccine Design

Manipulation of Co-Stimulatory Signals Can Enhance Immunity

Enhancement of APC Activity Can Modulate Tumor Immunity

Cytokine Therapy Can Augment Immune Responses to Tumors

IFN-, , and ; IL-1, IL-2, IL-4, IL-5, and IL-12;GM-CSF; and TNF.

INTERFERONSPurified recombination of IFN-, IFN-, and IFN-.

-Increase class I MHC expression on tumor cells. -Increase class II MHC expression on macrophages.-Inhibit cell division of both normal and malignantlytransformed cells in vitro.-Directly or indirectly increases the activity of TC cells, macrophages, and NK cells

TUMOR NECROSIS FACTORSTNF- and TNF- Killing some tumor cells and reducing the rate of proliferation of tumour cells. Tumor undergoes visible hemorrhagic necrosis and regression. Inhibits tumor-induced vascularization (angiogenesis)of a tumor.

IN VITROACTIVATED LAK AND TIL CELLS

S.Rosenberg discovered that, in the presence of high concentrations of cloned IL-2 , without the addition of tumor antigens, large numbers of activated lymphoid cellswere generated -kill fresh tumor cells but not normalcells. He called these cells lymphokine-activated killer(LAK) cells. LAK cells plus recombinant IL-2 into tumor bearing animals mediated effective tumor-cell destruction

Tumors contain lymphocytes that have infiltrated the tumour and presumably are taking part in an antitumor response.Small biopsy samples of tumors- lymphocytes in vitro with IL-2. These activated tumor-infiltrating lymphocytes are called TILs.Some TILs cells have specific cytolytic activity against their autologous tumor.

Monoclonal Antibodies Are Effectivein Treating Some TumorsFor example, anti-idiotype monoclonal antibodies have been used with some success in treating human B-cell lymphomas and T-cell leukemias.

Microvesicle Removal by Extracorporeal Filtration: The HemopurifierHollow-fiber cartridge (Hemopurifier)Utilizes an affinity substrate a proprietary lectin-based resin, which possesses high affinity for heavily glycosylated viral surface proteins.It can selectively deplete circulating virus with resultant accumulation of virus in the cartridge.

MV- 2,0005,000 ug/ml protein/ml of blood versus 00.5 ug in healthy volunteers.Hemopurifier used for removal of cancer-secreted immunosuppressive microvesicles.

Anti- Angiogeneic drugsAgents that prevent or decrease the secretion of angiogenic factors by tumour itself- IFNInc secretion of Antiangiogeneic factors- Retinoids