Cancer and the Immune System

Question 1

Predispositions of cancer

Answer 1

• environmental and lifestyle (80%)
• genetic (20%)
  
  • 2 to 8 sequential alterations
• ~140 genes (Mut-driver genes) - mutations contribute to cancer

Question 2

Driver mutation

Answer 2

• change in gene that gives cancer cell a fundamental growth advantage for its neoplastic transformation
• these genes function through a dozen signalling pathways that regulate
  
  • cell determination
  • cell survival
  • genome maintenance

Question 3

Carcinoma

Answer 3

• cancer drives from ectoderm or endoderm
• colon cancer or breast cancer

Question 4

Types of Cancer

Answer 4

• leukaemia - cancer of blood or bone marrow - abnormal increase of immature WBCs
• lymphoma - tumour in lymphoid tissue, bone marrow, lymph nodes
• Solid Tumours
  
  • adenocarcinoma - colon, breast
• melanoma - cancer of skin

Question 5

Immune response to tumours

Answer 5

• lymphoid cell infiltrates

Question 6

Leukemia

Answer 6

Acute Lymphocytic Leukemia (ALL)

• appearance and proliferation of immature, single, abnormal B cell
• bone marrow, blood, liver, spleen, lymph nodes

Symptoms - anaemia, low WBC, weight loss, fatigue, malaise

• absence of functioning granulocytes - prone to infections
• thrombocytopenia

Question 7

Treatment for decreased granulocytes

Answer 7

• recombinant G-CSF and GM-CSF injections

Question 8

Tumour Antigens

Answer 8

• Tumour Associated Antigens (TAA)
  
  • antigens derived from normal cell but overexpressed in tumours
  • normal self proteins - minimally expressed by healthy tissue but constitutively over expressed in cancer cells
  • VEGF, HER2, hTERT, CEA, CD19
• Tumour Specific Antigens (TSA)
  
  • antigens restricted to tumours - not found in healthy cells
  • result of malignant mutations or expression of viral antigens
  • neoantigens - created by mutations that change AAs
  • oncoviral antigens (HPV, HCV)
• Oncofetal Antigens

Question 9

Products of mutated genes

Answer 9

• chromosomal translocations - leukaemias
• point mutations (k-ras) - colon cancer
• Neoantigens - protein antigens encoded by mutated household genes

Question 10

Oncofetal antigens

Answer 10

• these proteins are over expressed at high levels in some cancers
• expressed during fetal development and not normal adult tissue
• these protein antigens appear in development before immune system develops B and T cell tolerance to self proteins
  
  • if expressed later on cancer cells - recognised as non self - trigger immune response

e.g.

• 𝛼-Fetoprotein - elevated in liver cancer
• CEA (carcinoembryonic antigen) - adhesion protein - increased levels seen in colon cancer

Question 11

Examples of oncogenic viruses

Answer 11

• T-cell leukaemia (adult) - HTLV I
• Burkitt’s lymphoma - EBV
• Cervical cancer - HPV (16 & 18)
• Liver cancer - Hep B & C
• Nasopharyngeal cancer - EBV
• Skin cancer - HPV
• Stomach cancer - H.pylori

Question 12

Immunity towards tumours

Answer 12

• CD8+ CTLs - prinicipal mechanism of recognition of tumour cell antigens
• NK cells - detects decreased MHC I - haemopoetic tumours
  
  • produce IFN-y, IL-2
• Macrophages - presence correlates with tumour regression
  
  • produce TNF-a

Question 13

Recognition of tumour cells

Answer 13

1. ADCC
2. CTL recognition of cancer peptides bound to MHC I on surface of cancer cell
3. NK recognition of loss of MHC I on surface of cancer cell

*3 mechanisms results in apoptotic cell death and removal of apoptotic bodies via macrophages

Question 14

Mechanisms of Tumour Evasion

Answer 14

• lack of T cell recognition of tumour
• inhibition of T cell activation

Question 15

Anergy

Answer 15

• immunologic tolerance characterised by the failure to mount a full immune response against tumour
• failure of cancer cells to present cancer antigens due to downreg of MHC class I
• failure of APC (DCs and macros) to present antigen to Th CD4 and CTL CD8
• failure of CTL CD8 NK cells to engage and kill cancer cell by apoptosis
• immunosuppressive environment of tumour
• tumour editing - downreg of tumour markers

*new approaches needed to be design to wake up immune system

Question 16

Ways of immunosuppression in TME

Answer 16

• tumour microenvironment - crucial in coming up with treatments against solid tumours
• tumours release adenosine under hypoxic conditions - suppress T cell activation - immunosuppressive environment
• tumour cells secrete immunosuppressive cytokines
  
  • IL-10
  • TGFβ

Question 17

Therapeutic interventions for immunosuppressive TME

Answer 17

1. Promote antigen presenting functions of DCs
2. Promote production of protective T cell responses
3. Overcoming immunosuppression in tumour bed

Question 18

Chemotherapy

Answer 18

• combination of
  
  • prednisolone (decreases inflamm)
  • dexamethasone (decreases inflamm)
  • vincristine (prevents tubulin formation)
  • asparginase (breaks down asparagine - starve cancer cell - no growth)

Question 19

Biologicals

Answer 19

• MAbs - to cancer specific antigens
• Cytokines - IL2, IFNs
• Immune checkpoint inhibitors - wake up immune system
  
  • DCs present antigens sufficiently
  • T cells kill tumour cells sufficiently
• CAR-T cell therapy
• Cancer vaccines - with or without DCs
• post chemo
  
  • G-CSF and GM-CSF - increase WBC numbers
  • erythropoietin - increase RBCs

Question 20

MAb suitable for CD19 antigen

Answer 20

• blinatumomab
  
  • single chain ab
  • specific for CD19 and CD3
  • targets CD19 and CD3 - recruits CTLs to kill ALL cells

Question 21

Immune Checkpoint Inhibitors

Answer 21

• immune checkpoints - control immune response
  
  • downregulate immune response once infection under control
• immune checkpoint receptors located on APC and T cell surface
  
  • dampen response by sending off signals to both cell typeS

Immunotherapy - immune checkpoint inhibitors

• block the checkpoint proteins from binding with partner proteins
• prevents the off signal being transmitted
• T cells and APCs work functionally to kill cancer cells

Question 22

CAR-T Cell Therapy

Answer 22

• combines abs and T cells
• CARs - molecules genetically engineered into polyclonal T cell pop giving T cells the ability to recognise tumour-associated surface antigens
• CAR in surface of T cell comprised of a single-chain variable fragment (scFv) - derived from mAb
  
  • connected to intracellular signalling domains - ensures T cell can be activated
• combines specificity of ab with cytotoxic ability of T cell
• involves the use of autologous T cells collected from cancer patient

Question 23

Allogenic CAR-T cells

Answer 23

• Graft-versus-host disease (GVHD) - main barrier
  
  • CRISPR technologies may need to be involved to remove TCR and MHC genes in donor T cells

Question 24

CAR T cell challenges

Answer 24

• success in haematological malignancies but limited success with solid tumours
• challenges involved in targeting solid tumours
  
  • precise tumour antigen target required
  • overcoming immunosuppressive tumour microenvironment
• Cytokine release syndrome (CRS)
  
  • immune effector cell -associated neurotoxicity syndrome (ICANS)
• Need to develop off shelf CAR-T cells from allogenic donors
• Cost (€320,000)

Question 25

Potential therapies to reduce CRS and ICANS associated with CAR-T cell therapy

Answer 25

* infusion of mAbs - that will bind and neutralise cytokine effects

Question 26

Dendritic Cell Cancer Therapy

Answer 26

* Sipuleucel-T - vaccine of enriched APCs/DC - pulsed with prostate acid phosphate (PAP) - reintroduced IV to induce immune response against prostate cancer

Question 27

Cancer Vaccination

Answer 27

* prophylactic vaccines * HBV vaccine - against hepatocellular carcinoma (liver cancer) * HPV vaccine against cervical and head & neck cancer * vaccination of patients with their own cancer **neoantigens**

Question 28

Neoantigens

Answer 28

* **point mutations** in genes that give rise to AA changes in proteins (non-synonymous point mutations) - generate neoantigens * effective anti-tumour immunity associated with T cell presence against neoantigens * MHC bound peptides that arise from tumour-specific mutations * neonantigens are **immunogenic** - not present in normal tissue

Question 29

Cancer Genome Sequencing

Answer 29

* based on identification of neoantigens * tumour material analysed for nonsynonymous somatic mutations * sequencing of genomic DNA * Whole exon sequencing * RNA seq - identify mutations in expressed genes * in-silico analysis - see if predicted mutated peptides are likely to bind to MHC I and MHC II * synthesise these neoantigen peptides and inject them into cancer patient

Question 30

Types of Transplant

Answer 30

* **autograft** - one part of body to another (same person) * **isograft** - between genetically identical individuals (monozygotic twins) * **allograft** - between different members of same species (different person) * **xenograft** - between members of different species (pig and human)

Question 31

Types of rejection reactions

Answer 31

* **hyperacute** - mins/hours - preformed anti donor , abs and complement * blood groups * **accelerated** - days - reactivation of sensitised T cells * 2nd graft * **acute** - days/wks - primary activation of T cells * 1st graft * **chronic** - months/yrs - cause is unclear (abs, immune complexes) * genetic disparity between donor and recipient

Question 32

Primary difference between one persons individuals cells and another persons

Answer 32

* AA sequence for MHC I and II * each individual has their own unique MHC/HLA genes giving rise to different MHC/HCLA class I and II proteins - haplotype * MHC proteins are co-dominantly expressed * 2 x each 6 * HLA, A, B, C, DR, DP, DQ * one MHC haplotype inherited from each parent

Question 33

Why is efficient matching of donor and recipients MHC crucial?

Answer 33

* antigens from donor or graft - picked up by recipient DCs * presented as foreign antigen to CTLs and THs in lymph nodes * graft MHC I and II - importnat for foreign recognition

Question 34

Therapies to prevent organ rejection

Answer 34

* most immunosuppressive therapies target production or inhibition of IL-2 * Cyclosporin - replaced by … * **Tacromilus** * **Basiliximab** - mAb (IL-2r blocker) * **Mycophenolate** - inhibits B & T cell proliferation - reversibly inhibits inosine monophosphate dehydrogenase - inhibits purine biosynthesis pathway * steroids no longer used

Question 35

How can the immune system be immunosuppressed to inhibit organ rejection?

Answer 35

* **IL-2 gene** * IL-2 production - T cell activation and immune activation * IL-2 stimulates many parts of immune response * produced by CD4+ Th Inhibited by cyclosporin and tacroplimus

Question 36

NFAT

Answer 36

* essential for IL-2 transcription

Question 37

Cyclosporin mechanism

Answer 37

* used to prevent organ/graft rejection * blocks activity of a specific phosphatase - **calcineurin** * calcineurin - unable to remove phosphate group from NFAT * NFAT remains active in cytoplasm * No IL-2 production * No Th cell activation - immunosuppression

Question 38

Where does NFAT bind?

Answer 38

* promoter region of IL-2 gene

Question 39

Inhibitor of Calcinuerin

Answer 39

* FK506 * Takrolimus - from bacterium strep tsukubaensis