Cancer Immunology Flashcards
Cancer and the immune system
Problem: immune system is taught to be self-tolerant
- ____ (thymus)
- __ ____ education (MHC-1)
Can the immune system distinguish normal healthy cells from malignant host cells?
- Yes it can
- Process is known as i____
Cancer and the immune system
Problem: immune system is taught to be self-tolerant
- T cells (thymus)
- NK cell education (MHC-1)
Can the immune system distinguish normal healthy cells from malignant host cells?
- Yes it can
- Process is known as immunosurveillance
Evidence for anti-tumour immunity
Clinical observations point ot existence of tumour-protective immunity in humans
- Lymphoid infiltration of cancers e.g. ‘hot’ vs ‘cold’ tumour
- type, location, density
- >‘immunoscore’, >prognosis
- >response to immunotherapy (pre-existing immune response to tumour)
Elaborate on all
Evidence for anti-tumour immunity
Clinical observations point ot existence of tumour-protective immunity in humans
- Lymphoid infiltration of cancers e.g. ‘hot’ vs ‘cold’ tumour
- type, location, density
- >‘immunoscore’, >prognosis
- >response to immunotherapy (pre-existing immune response to tumour)
- Measures density of two lymphocyte populations (CD3 and CD8) in the centre and periphery of tumor
- Score ranging from I0 (low densities of both cell types) to I4 (high densitites of both cell types)
- High immunoscore has better prognosis, longer term disease-free survival
- High immunoscore associated with a significantly improved response to immune checkpoint inhibition (immunotherapy) in terms of increased overall survival
Evidence for anti-tumour immunity
Clinical observations point ot existence of tumour-protective immunity in humans
- Immunodeficiency/immunosuppression
* primary (inherited) immunodeficiencies
* infection
* transplantation
- Immunodeficiency/immunosuppression
Elaborate on all
Evidence for anti-tumour immunity
Clinical observations point ot existence of tumour-protective immunity in humans
- Immunodeficiency/immunosuppression
* primary (inherited) immunodeficiencies- lymphoma - EBV
* infection - Malaria - Burkitt’s lymphoma - EBV
- AIDS - Karposi’s sarcoma - EBV
* transplantation - Kidney transplant (relative risk) - Karposi’s sarcoma - 50-100% relative risk
- lymphoma - EBV
- Immunodeficiency/immunosuppression
- .
- .
- Immunosuppression increases risk of virally induced cancer
- e.g. Malaria causes immunodeficiency - results in Burkitt’s Lymphoma - EBV
- In all forms of immunodeficiency, the relative risk of developing tumours in which oncogenic viruses are known to play a role is greatly increased
- Relative risk for kidney transplantation patients greatly increased because of wide regimen of immunsuppressive treatments
*
Evidence for anti-tumour immunity
Clinical observations point ot existence of tumour-protective immunity in humans
- In vitro immune response to cancer cells
* natural killer cells
- In vitro immune response to cancer cells
Elaborate on all
Evidence for anti-tumour immunity
Clinical observations point ot existence of tumour-protective immunity in humans
- In vitro immune response to cancer cells
* natural killer cells
* Spontaneous lymphocyte-mediated cytotoxicity (SLMC)
* From normal donors aganst recipient tumour
4.
- In vitro immune response to cancer cells
Evidence for anti-tumour immunity
Clinical observations point ot existence of tumour-protective immunity in humans
- Immune repsonse to cancer cells in animal models (in vivo)
- RAG -/- mice (lack B and T cells) develop more gut epithelial and breast tumours
- mice can be immunised to tumour cells
- Immune repsonse to cancer cells in animal models (in vivo)
Elaborate on all
Evidence for anti-tumour immunity
Clinical observations point ot existence of tumour-protective immunity in humans
- Immune repsonse to cancer cells in animal models (in vivo)
- RAG -/- mice (lack B and T cells) develop more gut epithelial and breast tumours
- mice can be immunised to tumour cells
- (direct evidence for tumour immunity)
- Immune repsonse to cancer cells in animal models (in vivo)
Evidence for anti-tumour immunity
Clinical observations point ot existence of tumour-protective immunity in humans
- Lymphoid infiltration of cancers e.g. ‘hot’ vs ‘cold’ tumour
- type, location, density
- >‘immunoscore’, >prognosis
- >response to immunotherapy (pre-existing immune response to tumour)
- Immunodeficiency/immunosuppression
- primary (inherited) immunodeficiencies
- infection
- transplantation
- In vitro immune response to cancer cells
- natural killer cells
- Immune repsonse to cancer cells in animal models (in vivo)
- RAG -/- mice (lack B and T cells) develop more gut epithelial and breast tumours
- mice can be immunised to tumour cells
ALL THESE EXPERIMENTS SHOW THE IMMUNE SYSTEM CAN R___ AND R___ TO T___ CELLS (A____)
Evidence for anti-tumour immunity
Clinical observations point ot existence of tumour-protective immunity in humans
ALL THESE EXPERIMENTS SHOW THE IMMUNE SYSTEM CAN RECOGNISE AND RESPOND TO TUMOUR CELLS (ANTIGENS)
Tumour antigens
LOTS of different classes of tumour antigens:
- O___ v___ antiens
- M___ g___ products
- A___ glycol___/glycop____
- A____ e____ antigens
- Cell-type s____ d_____ antigens
Q) foreign/mutated/unmutated for each?
Tumour antigens
LOTS of different classes of tumour antigens:
- Oncogenic viral antiens
- foreign
- Mutated gene products
- Mutated
- Altered glycolipid/glycoproteins
- Mutated
- Abberantly expressed antigens
- unmutated
- Cell-type specific differentiation antigens
- unmutated
- Oncogenic virus antigens
- Human papilloma virus (HPV16) e.g. E_ & E_
- C___ and a___ cancer, O__ cancer
- Epstein Barr Virus e.g. ___1
- B___ L___
- Foreign - i_____
- E7 induces i_____ e.g. MHC Class I suppression, represses ___, ___ genes
- EBNA1 G__-A__ repeates inhibit p____/Ag presentation
- Oncogenic virus antigens
- Human papilloma virus (HPV16) e.g. E6 & E7
- Cervical and anal cancer, Oral cancer
- Epstein Barr Virus e.g. EBNA1
- Burkitt’s Lymphoma
- Foreign - immunogenic
- E7 induces immunosuppression e.g. MHC Class I suppression, represses TLR9, IRF genes
- EBNA1 Gly-Ala repeates inhibit proteasome/Ag presentation
- Mutated Gene Products
- Cancer cells can have lots of mutations
- Oncogenes and TSGs frequently mutated in cancer
- good example:____
- Intron retention in mRNA due to dysregulated splicing in cancer cells e.g. melanoma
- These are ‘altered self’ and can be immunogenic
- Tumour-specific neoepitopes may be therapeutic targets in personalised cancer vaccines
- Majority of protective immune responses - highly speciifc for cancer cells vs. host cells
2 key takeaways:
- Mutational load is highly ____, of which melanoma is _____
- Cancers cells are inherently _____, can generate lots of _______ to _______
- Mutated Gene Products
- Cancer cells can have lots of mutations
- Oncogenes and TSGs frequently mutated in cancer
- good example: tumour infilrating cd4+ cells specific for BRAF mutation in melanoma correlate with complete clincal response in these patients
- Intron retention in mRNA due to dysregulated splicing in cancer cells e.g. melanoma
- These are ‘altered self’ and can be immunogenic
- Tumour-specific neoepitopes may be therapeutic targets in personalised cancer vaccines
- Majority of protective immune responses - highly speciifc for cancer cells vs. host cells
- figure shows frequency of mutations per megabase of human genome
2 key takeaways:
- Mutational load is highly dependent on the cancer, of which melanoma is on the high end of the spectrum, 75k mutations per Mb of human genome
- Cancers cells are inherently genetically unstable, can generate a lot of variants to evade immune response
Altered glycolipids/glycoproteins
- Gl____ - glycolypid/glycoprotein m____ covering animal cells
- Tumours really manipulate this surface
- Highly robust on cancer cells
- Promotes i___ c____, g___ f___ s____, m_______
- Enhances cancer cell g___ and s___, m___ and m____
- A_____ forms/o___-e___ of cell-surface glycolipids/glycoproteins
- M___ e.g. MUC-1 (breast), CA-125 (ovarian)
- G____ e.g. GM2, GD3 (melanoma)
- Mutated
Altered glycolipids/glycoproteins
- Glycocalyx - glycolypid/glycoprotein matrix covering animal cells
- Tumours really manipulate this surface
- Highly robust on cancer cells
- Promotes integrin clustering, growth factor signalling, mechanotransduction
- Enhances cancer cell growth and survival, motility and metastasis
- Abnormal forms/over-expression of cell-surface glycolipids/glycoproteins
- Mucins e.g. MUC-1 (breast), CA-125 (ovarian)
- Gangliosides e.g. GM2, GD3 (melanoma)
- Mutated
- Abberantly expressed antigens
- Cancers can r_-e____ genes s___ in most adult tissues
- D____ eg. oncofoetal antigens: e.g. a___-f____
- a__-f____ re-expressed in h__c___ c___ (HCC)
- T___-s___ e.g. cancer-testis (CT) antigens: MAGE, NY-ESO-1
- MAGE-1 found in 37% melanomas
- NY-ESO-1 found in 46% melanomas
- O___-e_____ e.g. Her2-Neu e____ g___ f___ r___ gene a____ in breast cancer
- Unmutated tumour antigens
- Abberantly expressed antigens
- Cancers can re-express genes silent in most adult tissues
- Developmental eg. oncofoetal antigens: e.g. alpha-fetoprotein
- a-fetoprotein re-expressed in hepatocellular carcinoma (HCC)
- Tissue-specific e.g. cancer-testis (CT) antigens: MAGE, NY-ESO-1
- MAGE-1 found in 37% melanomas
- NY-ESO-1 found in 46% melanomas
- Over-expressed e.g. Her2-Neu epidermal growth factor receptor gene amplified in breast cancer
- Unmutated tumour antigens
- Cell-type speicifc differentiation antigens
- Tumours normally express antigens for c___ of o____
- Specific for cell l___/d____ stages (unmutated)
- Important targets for immunotherapy and diagnosis
- E.g. CD20 expressed by mature B cells and B cell lymphomas
- CD30 expressed on activated B cells and B cell cancers
- R____ (anti-CD20 antibody) is widely used in B cell leukaemia /lymphoma therapy
- T___ MRT1, gp75 and gp100 - common melanoma antigens (melanocyte lineage)
- Cell-type speicifc differentiation antigens
- Tumours normally express antigens for cells of origin
- Specific for cell lineages/differentiation stages (unmutated)
- Important targets for immunotherapy and diagnosis
- E.g. CD20 expressed by mature B cells and B cell lymphomas
- CD30 expressed on activated B cells and B cell cancers
- Rituximab (anti-CD20 antibody) is widely used in B cell leukaemia /lymphoma therapy
- Tyrosinase, MRT1, gp75 and gp100 - common melanoma antigens (melanocyte lineage)
Immune recognition of Cancer
- How mutated/foreign antigens are presented to the immune system
- Normal cell
- normal self peptides displayed on MHC, no ______ due to ____
- Tumour cell
- M___-g____ n_____ = new TCR contact residue, T cell response
- Tumour cell with oncogenic virus
- Peptide from a p____ encoded by an o___ v____
- T cell response
Immune recognition of Cancer
- How mutated/foreign antigens are presented to the immune system
- Normal cell
- normal self peptides displayed on MHC, no responding T cells due to tolerance
- Tumour cell
- Mutation-generated neoepitope = new TCR contact residue, T cell response
- Tumour cell with oncogenic virus
- Peptide from a protein encoded by an oncogenic virus
- T cell response
Immune recognition of Cancer
- How unmutated antigens are presented to the immune system
- De-r______ expression (e.g. cancer/t____ antigens)
- normally m____ gene gets de-m___
- t__ s___ p___ e___
- tumour antigen peptide with tumour specific CD8+ T cell
- O_____ of o__ p___ due to gene a____ (HER2-Neu in breast carcinoma)
- Large amount of protein = overcome low affinity of binding
- I___ number of cells e___ t___s___ p__ (e.g. t___ in melanomas)
- same as overexpressing
Immune recognition of Cancer
- How unmutated antigens are presented to the immune system
- De-repressed expression (e.g. cancer/testes antigens)
- normally methylated gene gets de-methylated
- tumour specific protein expression
- tumour antigen peptide with tumour specific CD8+ T cell
- Overexpression of oncogenic protein due to gene amplification (HER2-Neu in breast carcinoma)
- Large amount of protein = overcome low affinity of binding
- Increased number of cells expressing tissue specific protein (e.g. tyrosinase in melanomas)
- same as overexpressing
Recap
- The immune system responds to tumour cells but…
Which immune cell subsets elicit anti-tumour immunity and how?
Adaptive immunity vs innate immunity
Adaptive immunity to tumours
- CD8+ cytotoxic T lymphocytes (CTL)
- CD4+ T helper cells
Innate immunity to tumours
- NK cells
T cells become activated by being presented antigens by APC (dendritic cells)
Naive T cells require signal 1 in the form of TCR binding to tumour peptide in context of mhc-1, and signal 2 from professional APC
CD4+ cells recognise exogenous peptides presented on mhc-2, only ever presented on apcs, receive signal 2, become actiated, provide CD8+ help via t-cell growth factor IL-2
Key features of CD4+ T cell Help
- CD4+ T cell help is essential for p___ of CTL by c___-p____ antigen
- D___C___s help relay CD4+ T cell help signals to CTL
- Large part of the ‘help’ signal originates from ___L-___ interaction
Key features of CD4+ T cell Help
- CD4+ T cell help is essential for priming of CTL by cross-presented antigen
- CDs help relay CD4+ T cell help signals to CTL
- Large part of the ‘help’ signal originates from CD40L-CD40 interaction
Specialised Dendritic Cells ‘cross-present’ tumour antigens to CD8+ T cells
Cross-presentation
- unique ability of DCs that express the B___ t____ f____ to present e____-derived tumour Ags on MHC-_
- Describe process
- phagocytose tumour cell, derive antigen
- Travel to lymph node, present tumour specific antigen on MHC-I to CD8+ T cell
- Migration of tumour-specific CTL to tumour
- CTL mediated killing of tumour
Personalised peptide vaccines for cancer therapy
- Massive parallel sequencing of Melanoma stage III B/C, IV M1a/b tumours for detection of coding mutations
- Machine learning approaches to predict those melanoma mutated peptides with high affinity binding for a PT’s human leukocyte antigen (HLA) molecules (MHC-I)
- Of 6 vaccinated melanoma PTs, 4 had no recurrence at 25 months after vaccination, while 2 with recurrent disease were subsequently treated with anti-PD-1 and experienced complete tumour regression
Of 6 vaccinated melanoma PTs,
- 4 had no recurrence at 25 months after vaccination,
- 2 with recurrent disease were subsequently treated with anti-PD-1 and
- experienced complete tumour regression
B cells/Antibody
- B cells develop Abs to tumour antigens (Ags)
- Detected in h___ and c___ patients
- Fc region of Ab engage Fc receptors (FcR+) cells
- A____-d____ c___ c____ (ADCC) = NK cells (____ which ligand)
- A__-____ c___ p____ (ADCP) = Macrophage
- C___-mediated tumour cell lysis
- Biomarkers for overal survival and successful immunotherapy
- IgE (allergy) provides protection against cancer
- CD16 g____ effects ADCC and clinical efficacy of Rituximab
- CD16 158VV have higher affinity for IgG than CD16 158FF
B cells/Antibody
- B cells develop Abs to tumour antigens (Ags)
- Detected in healthy and cancer patients
- Fc region of Ab engage Fc receptors (FcR+) cells
- Antibody-dependent cellular cytotoxicity (ADCC) = NK cells (CD16)
- Antibody-dependent cellular phagocytosis (ADCP) = Macrophage
- Complement-mediated tumour cell lysis
- Biomarkers for overal survival and successful immunotherapy
- IgE (allergy) provides protection against cancer
- CD16 genotype effects ADCC and clinical efficacy of Rituximab
- CD16 158VV have higher affinity for IgG than CD16 158FF
Role of antibody in Melanoma
- Abs to melanoma antigens detected in healthy and cancer patients
- Biomarkers for overall survival and successful checkpoint blockade immunotherapy in stage IV melanoma
- Pre-existing immune response
- Does having greater antbody response mean anything?
- Promote completment-mediated lysis, ADCC or ADCP
- healthy donors pre-existing cytotoxic IgM to melanoma Ag
- Abs can have anti- and pro-tumour properties in melanoma
- Explain
- Biomarkers for overall survival and successful checkpoint blockade immunotherapy in stage IV melanoma
- Pre-existing immune response
- PTs that successfully respond to immunotherapy have a greater antibody response to NY-ESO-1 (A) than non-responders, which translates to better survival (C)
- Abs can have anti- and pro-tumour properties in melanoma
- Early on, IgM antibodies are good at activating complement responses, ADCC and ADCP
- Later stages, class switching to IgG and IgA makes the Abs less good at activating complement and take on pro-tumour properties
Innate Immunity = Natural Killer (NK) Cells
- Express an array of ACTIVATING and INHIBITORY receptors
- Activating: FcR (CD16), NKG2D, NKp44, NKp30
- Inhibitory: bind MHC-I e.g. KIR (human), Ly49 (mouse)
- Important for catching tumour cells that d____ ______ to e____ ____
Important for catching tumour cells that downregulate MHC-I to evade CTL
Kills cells that dont have MHC-1 but express other activating ligands
Downregulation of MHC-I & NK cells in melanoma
A significant amount of melanoma patients downregulate all 3 MHC-I subtypes
so??
Patients with low MHC but high NK have better survival rates becase of NK cell mediated killing
NK Cells - Continued
_____ - allows recognition of s____ cells expressing s___-i____ ligands e.g. MIC-A, RAE-1, ULBPs (DNA damage, dsDNA breaks)
NK cells kill by a____ to cancer cells and polarised release of p___ and g_____
NK Cells - Continued
NKG2D - allows recognition of stressed cells expressing stress-inducible ligands e.g. MIC-A, RAE-1, ULBPs (DNA damage, dsDNA breaks)
NK cells kill by attaching to cancer cells and polarised release of perforin and granzymes
Two Receptor Model
For NK cell recognition and activation in natural killing
ITIM = immunoreceptor Tyr-based inhibition motif
ITAM = immunoreceptor Tyr-based activation motif
explain process
Activating NK receptors cooperate/cross-talk for tumour killing
Tumour Immune Evasion
How do tumours evade immunosurveillance?
- Low immunogenicity
- Tumour treated as self-antigen
- Antigenic modulation
- Tumour-induced immune suppression
- Tumour-induced priviledged site
Describe
Tumour Immune Evasion
How do tumours evade immunosurveillance?
- Low immunogenicity
- no peptide:mhc ligand
- no adhesion molecules
- no co-stimulatory molecules
- Tumour treated as self-antigen
- tumour Ags taken up and presented by APC in absence of co-stimulation, tolerise T cells
- Antigenic modulation
- T cells may eliminate tumours expressing immunogenic antigens, but not those who have lost such antigens
- Tumour-induced immune suppression
- tumour cell may secrete factors (TGF-b, IL-10) that inhibit T cells directly
- Expression of PD-L1 by tumour
- Tumour-induced priviledged site
- Tumour secrete extracellular matrix or collagen that creates a physical barrier and prevents immune cells penetrating
Immunoediting
- Tumour cells are inherently g___ u___
- V___ arise that can e___ an effective immune repsonse (immune selection = e___)
Three E’s of tumorigenesis
- E____
- E____
- E____
Immunoediting
- Tumour cells are inherently genetically unstable
- Varaints arise that can escape an effective immune repsonse (immune selection = editing)
Three E’s of tumorigenesis
- Elimination
- Equilibrium
- Escape
I.e. constantly mutate such that eventually, one varaint can escape killing mechanism and can spread unchallenged
Cancer-immune Equilibrium
Evidence
- comes from occult or latent cancer transferred from organ donors to recipients
- any patient who has had cancer (melanoma) should not have their organs donated because can transfer cancer
- In mice, CD8+ t___-r___ m___ (TRM) cells promote m___-i__ e___ in skin epithelium - mice remain free of m____ melanoma but melanoma tumour cells still p___ (cells c____ = e_____)
Cancer-immune Equilibrium
Evidence
- comes from occult or latent cancer transferred from organ donors to recipients
- any patient who has had cancer (melanoma) should not have their organs donated because can transfer cancer
- In mice, CD8+ tissue-resident memory (TRM) cells promote melanoma-immune equilibrium in skin epithelium - mice remain free of macroscopic melanoma but melanoma tumour cells still present (cells contained = equilibrium)
Melanoma Immune-evasion
- Only a subset of melanoma patients responds to checkpoint immunotherapy (anti-PD-1 etc.)
- suggest therapeutic benefit achieved in patients with pre-existing T-cell responses e.g. baseline CD8+ T-cell infiltration
- WNT/β-catenin o____ pathway u_____ in immunotherapy-resistant melanomas
- activates the t____ r____ ____ to suppress transcription of ____ chemokine and
recruitment of _____+ DCs - results in i___ e___ (‘cold’ tumour)
- Targeting WNT/β-catenin pathway may benefit immunotherapy-resistant melanoma patients
Melanoma Immune-evasion
- Only a subset of melanoma patients responds to checkpoint immunotherapy (anti-PD-1 etc.)
- suggest therapeutic benefit achieved in patients with pre-existing T-cell responses e.g. baseline CD8+ T-cell infiltration
- WNT/β-catenin oncogenic pathway upregulated in immunotherapy-resistant melanomas
- activates the transcriptional repressor ATF3 to suppress transcription of CCL4 chemokine and
recruitment of Batf3+ DCs - results in immune exclusion (‘cold’ tumour)
- Targeting WNT/β-catenin pathway may benefit immunotherapy-resistant melanoma patients
Melanoma Immune-evasion
- Tumours can induce a____ of t___-i____ l____ (TILs) as one method of immune evasion
- Melanomas increase expression of ___ l____ (FASL) on tumour-associated ‘myeloid suppressor cells’
- FASL engages the death receptor FAS on T cells
- > programmed cell death (apoptosis)
- Depleting suppressive FASL+ myeloid cells (anti-Ly6G) and blocking Fas (Fas-Fc) can improve anti-PD1 immunotherapy
Melanoma Immune-evasion
- Tumours can induce apoptosis of tumor-infiltrating lymphocytes (TILs) as one method of immune evasion
- Melanomas increase expression of FAS ligand (FASL) on tumour-associated ‘myeloid suppressor cells’
- FASL engages the death receptor FAS on T cells
- > programmed cell death (apoptosis)
- Depleting suppressive FASL+ myeloid cells (anti-Ly6G) and blocking Fas (Fas-Fc) can improve anti-PD1 immunotherapy
Melanoma Immune-Evasion
- growth of BrafV600E tumour cells require prostaglandin E2 for growth
- cyclooxygenases (COX) responsible for prostaglandin formation
- suppress anti-tumour T cell immunity (type I IFN signalling) and fuels ‘tumour promoting inflammation’ (IL-1, IL-6)
- COX ablation in BrafV600E melanoma cells renders them susceptible to immune control
- COX-dependent inflammatory signature conserved in human melanoma biopsies
- COX inhibition (aspirin) synergises with anti-PD-1 blockade in pre-clinical model
Summarise this
Summary:
BrafV600E melanomas need PGE2 to grow
Using aspirin (COX inhibitor) can be used in adjunct with immunotherapy (anti-PD-1 blockade)
