Immuno 4: Tumour immunology and immunotherapy of cancer Flashcards
Outline a piece of evidence that the immune system mounts a response against some tumours
Breast cancer can get paraneoplastic cerebellar degeneration (PCD)
CDR2 (cerebellum degeneration-related antigen 2)
is normally expressed in cerebellum.
But the breast cancer also expresses that, randomly.
Then, an immune response is mounted against the antigen in the breast: anti-CDR2 antibody in the serum.
The antibody then travels to the brain and destroys neurons with CDR2 antigens in the cerebellum
What are the signs of Paraneoplastic cerebellar degeneration (PCD)
- severe vertigo
- unintelligible speech
- truncal and appendicular ataxia
How can PCD be confirmed using immunohistology
Add control serum, and the PCD patient’s serum to sections of the breast tumour
The PCD patient serum has anti-CDR2 antibody. This binds.
Then you put in an anti-antibody which is linked to peroxidase enzyme.
If there is reaction between the CDR2 antigen and the anti-CDR2 antibody from the PCD patient serum, then it will turn brown
What will be seen in a normal brain vs PCD brain
In PCD there is loss of purkinje cells (motor neurons in the cerebellum)
What can PCD in breast cancer teach us
- Some tumours can express antigens not present in the corresponding normal tissue (i.e. CDR2 not in breast normally)
- Immune system can detect abnormally expressed antigens, and launch attack against tumour
- There can be auto-immune destruction of tissue normally containing that antigen
Circumstantial evidence for immune control of tumours in humans
- Autopsies of accident victims have microscopic colonies of cancer cells, with no symptoms of disease
- Patients treated w melanoma who were free of disease were organ donors for transplantation. Transplant recipients developed tumours (donor had developed immunity to the melanoma, but the transplant recipients didn’t have this)
- Deliberate immunosuppression (e.g. in transplantation) increases risk of malignancy
- Men have twice as great chance of dying from malignant cancer as do women (women typically mount stronger immune responses)
What is immunosurveillance
malignant cells are generally controlled by the action of the immune system.
What is the overall goal of immuotherapy
Immunotherapy tries to enhance immune responses to cancer.
Differentiate what is recognised by T and B cells
T cells. MHC restricted. ab TCR
B cells. BCR (antibody). Vast range of molecules. VIRUS NEUTRALISATION
What type of immune system is used in immunotherapy
Harness power of the adaptive immune system
Outline the cancer-immunity cycle
- Tumour grows but some cells die, releasing potential antigens
- Antigen taken up and presented on dendritic cell surface.
- APC drained by the lymph to a lymph node. Priming and activation of T cells
- Trafficking of T cells to tumour (CTLs) via the blood stream
- Infiltration of T cells nto tumours (CTLs, endothelial cells)
- Cancer cells recognised by T cells
- Cancer cells killed and more cancer cell antigens released
What is a TIL
Tumour infiltratin lymphocytes
Activated T lymphocytes which have been activated by dendritic cell in the lymph node and can recognise cancer antigens on MHC
Try to kill tumour cells
Why doesn’t the cancer-immunity cycle kill all tumour cells then
There is immune selection pressure placed on the tumour cells
Any mutations e.g. loss of MHC expression, will allow tumour cells to escape T cell recognition
Mutations can allow resistance to the pressure
Which molecules are targeted in immune checkpoint blockade
Trying to remove the negative signals which prevent immune responses
CTLA and PD-L1
What normalyl vauses initiation of cancer (inherited or acquired?)
SPORADIC EVENTS OVER TIME:
- Irradiation
- Chemical mutagens
- Spontaneous errors during DNA repication
- Tumor virus-induced chages in genome
INDUCES MUTATIONS
What leads to rapid cell proliferation overall in cancer
Aberrant regulation of apoptosis and cell cycle results in tumour growth
Outline the immune response to tumour
ONCE INFLAMMATORY SIGNALS OCCUR (late):
- recruitment of innate immunity (DC/ macrophage/NK)
- Drainage of these cells to lymph node s
- subsequent recruitment of adaptive, antigen-specific immunity
What is required for activation of adaptive anti-tumour immune response
- Local inflammation in the tumour (“danger signal”–> recognition of antigen alone not enough… need costimulation from danger signals)
- Expression and recognition of tumour antigens
Problems in the immune surveilance of cancer compared to infection for example
- It takes the tumour a while to cause local inflammation
- Antigenic differences between normal and tumour cells can be very subtle (e.g. small number of point mutations) compared to virus which has completely different antigens
When is immunotherapy useful
If requirements for ‘spontaneous’ activation of the adaptive anti-tumour response are NOT met, can we ‘teach’ the adaptive immune system to selectively detect and destroy tumour cells?
T/F cancer immunotherapy usually used isolated
Potential alternative/supplement to conventional therapies (surgery, chemotherapy, radiotherapy)
What is important when considering how to teach the adaptive immune system to selectively detect and destroy tumour cells
Which antigens should be targeted
What is the similarity between the immune response to virally infected cells and tumour cells
Virally infected cells present internal peptides on MHC class 1 molecules for presentation to T cell
This is the same for tumour cells, most of the antigens are internal peptides presented on class 1
In the same way, some viruses present glycoproteins on the host cell membrane which can be recognised by antibodies.
Tumour cells, similarly, have some proteins on the plasma membrane which can be recognised by antibodies
Outline the 2 locations of antigens on tumour cells`
- Most are internal, presented in MHC 1
- Some are on the plasma membrane, recognised by antibodies (humoral)
I.E. SAME FOR VIRUS
Function of MHC and when is it important
‘Display’ contents of cell for surveillance
by T cells:
infection, carcinogenesis
Outline the 2 types of tumour specific antigens. Which is easier to mount immune response against
- Viral proteins (from cancers caused by viruses)
- EBV
- HPV
(these antigens would not normally be present on cell surfaces, but in tumour cells due to this virus, antigens from these viruses will be present. As these are completely different to what is in the host, then ideal to target)
- Mutated cellular proteins
e.g.
TGF-b receptor III (this is just a mutated protein)
BCR-ABL (a fusion gene as you know)
2 types of cancers of viral orgigin
- Opportunistic malignancies (IMMUNOSUPRESSION)
2. In immunocompetent patients
Give examples of cancers of viral origin, in immunosupressed patients
OPPORTUNISTIC MALIGNANCY
- EBV-positive lymphoma: Post-transplant immunosuppression
- HHV8-positive Kaposi sarcoma: HIV
Give examples of cancers of viral origin, in immunocompetent patients
HTLV1-associated leukaemia/lymphoma
HepB virus and HepC virus associated hepatocellular carcinoma
HPV positive genital tumours
What occurs to viral antigens for viruses that cause tumours
Tumour cells express
viral antigens!
HPV is particularly associated with which cancer
Cervical
Which proteins within HPV cause and maintain cervical cancer
Cervical cancer is induced and maintained by the E6 and E7 oncoproteins of HPV
Involved in cell transformation
INTRACELLULAR ANTIGENS but are presented on the surface of tumour cells
T/f E6 and E7 are intracellular antigens
True.
But can be expressed via MHC class 1 (presented as processed peptide not within plasma membrane i.e for T cell recognition not humoral, although E5 tries to prevent this!!!!!)
What are the target antigens for preventative HPV (vaccine)
E6 and E7 oncoproteins too dangerous
Instead use ‘late genes’ called L1 and L2
These are surface proteins incorporated in virus like particles (VLPs)
What is the name of the HPV vaccine
Gardasil
T/F most women, when infected with HPV16, would develop cervical cancer
F…..
Even though HPV 16 is a cancerous strain, when most women (99%) are infected with it, their immune system can cope with it and they get HPV-infection clearance and immunological memory
In contrast in a very small proportion of women, they have immune failure to HPV, and get cervical neoplasia (50% have no immunity and 50% have non-functional immunity)
Differentiate when you would use preventative vaccination and when therapeutic vaccination for HPV
Preventative: EVERYONE just in case they are part of the minority group with immune failure against cancerous strains
Therapeutic can be given to people with immune failure if they didn’t have the vaccine (or if they did, and still had immune failure) and went on to develop cervical cancer. Being given therapeutic vaccination in this case can stimulate the body to mount immune response against the cancer
Describe tumour associated atigens
Tumour-associated antigens (TAA) derive from normal cellular proteins which are aberrantly expressed (timing, location or quantity).
ECTOPICALLY EXPRESSED AUTO-ANTIGENS
Why are tumour associated antigens hard for body to target
Because they are normal self proteins, for an immune response to occur tolerance may need to be overcome.
What are cancer-testes antigens
Tumour-associated antigens
These are developmental antigens. They are silent in normal adult tissues except male germ cells/placenta
Can be present in tumour tissue
Give an example of cancer-testes genes
MAGE family (MAGE-3)
Melanoma associated antigens. Identified in melanoma also expressed in other tumours
Cancer-testes gene so they are normal cell proteins, they are just abnormally expressed
Other examples of tumour associated antigen
HER2
Mucin 1 (MUC-1)
Carcinoembryonic antigen (CEA)
- prostate-specific antigen (PSA)
- prostate-specific membrane antigen (PSMA)
- prostatic acid phosphatase (PAP)
Give examples of when the following tumour associated antigens are important:
- HER2
- MUC-1
- CEA
- Prostate
Human epidermal growth factor receptor 2 (HER2): overexpressed in some breast carcinomas
Mucin 1 (MUC-1): membrane-associated glycoprotein, overexpressed in very many cancers
Carcinoembryonic antigen (CEA): normally only expressed in foetus/embryo, but overexpressed in a wide range of carcinomas
PSA, PSMA and PAP are all normal prostate antigens but just over-expressed in prostate cancer
Which cells are stimulated in immunotherapy
T cells that have escaped the mechanism for central tolerance in the thymus
(i.e. normally there is negative selection of autoreactive T cells in the thymus. Some espcape into circulation, which is why peropheral tolerance is needed)
What can be the problem with targeting tumour associated auto-antigens
Auto-immune responses against normal tissues (lineage specific)
Immunological tolerance
- Normal tolerance to auto-antigens
- Tumour-induced tolerance
t/f…. when the immune system is targeted against tumour associated antigens, there is always an autoimmune response
What is meant by the lineage specific nature of some autoantigens
What is the consequence for therapy. Give an example
F…. because tumour associated antigens not always expressed in adult cells (for example in the MAGE family there will not always be expression occurring in the adult cells because they are usually only expressed in development (or in germ cells or placenta)
Differentiation antigen refers to an antigen which is specific to a certain cell lineage.
In this case, tyrosinase is specific to melanocytes.
Some people have poor self tolerance to tyrosinase.
If someone gets a melanoma, they can thus quite easily generate immune response against it (poor self tolerance), leading to reactivity with the tumour cell, in which the tyrosinase is over expressed, but also….
Autoimmune reactivity against normal melancyte cells too–> hypopigmentation around the tumour
This can be with therapy or even just in an individual’s natural immune response to the cancer
Why can there be depigmentation around the melanoma tumour
Local auto-immune depigmentation in melanoma patients
The body mounts immune response against the tyrosinase which is a differentiation antigen expressed in both normal melanocytes and in melanomas. So the body is trying to wipe out the tumour but also have autoreactivity to normal melanocytes, killing them and producing white patch
What are the 5 types of therapy
- Antibody-based therapy
- Therapeutic vaccination
- Immune checkpoint blockade
- Adoptive transfer of immune cells
- Combinations of 1) to 4) above
3 types of monoclonal antibody-based therapy
- Naked
- Congugated
- Bispecific
Give example of naked monoclonal antibody therapy
e.g. Trastuzumab (Herceptin®), anti HER2
Examples of conjugated monoclonal antibody therapy
Can conjugate antibody to:
- radioactive particle e.g. Ibritumomab tioxetan (Zevalin®), anti CD20 linked to yttrium-90
- drug e.g. Trastuzumab emtansine (Kadcyla®), anti HER2 linked to cytotoxic drug
i. e. so you don’t make the immune system do the work like with when you just have antibodies binding (anti-her2) you make immune system do work. Now you add drug or radioactive to kill the cells
Outline bispecific antibodues
Genetically engineered to combine 2 specificities, e.g. anti CD3 and anti CD19 (Blinatumomab, approved for use in patients with some B cell tumours)
Bring the B cell tumour near to a T cell so the T cell can kill it
Outline therapeutic cancer vaccination exampe
Provenge® (sipuleucel-T) for advanced prostate cancer
Patient’s own WBC are treated with a fusion protein between prostatic acid phosphatase (PAP) and the cytokine GM-CSF (which is thought to upregulate antigen presentation)
Stimulates DC maturation and enhances PAP-specific T cell responses
So you have to remove patient’s white cells (Magnetic beads: e.g. purification of cell types…. look back to diagnostics)
Problem with monoclonal anti-based therapy
Very expensive
What is kadcyla
Trastuzumab emtansine (Kadcyla®), anti HER2 linked to cytotoxic drug
How do ‘personalised’ tumour-specific cancer vaccines work
- Do whole exome sequencing (i.e. sequence all the genes which encode proteins) in tumour cell vs normal cell
- Look for where there are differences (mutations).
- Confirm these differences by looking for the same mutations in the RNA and DNA of the tumour cell
- Look at the HLA of the person from the normal cell
- Look at which of the mutated gene products can bind that persons HLA and thus appear on MHC
- These are the ‘candidate neoarntigens’ and then you add adjuvant
What is the relationship between immune checkpoint blockade and cell cycle blockade
NOTHING lol they unrelated
What is immune checkpoint blockade treatment
Rather than directly stimulate responses, this approach seeks to reduce/remove negative regulatory controls of existing T cell responses
Targets CTLA-4 and PD-1 pathways
Where is CTLA-4 expressed
How do you block it
So this is just a molecule which downregulates immune response
CTLA-4 is expressed on activated and regulatory T cells, binds to CD80/86 (costimulatory molecules on APC, inhibiting them)
Ipilimumab (anti CTLA-4),
Where is PD-1 expressed
So this is just a molecule which downregulates immune response
PD-1 is expressed on activated T cells, binds to PD-L1/L2 (complex expression patterns, may be upregulated on tumours…i.e. tumour downregulated immune response)
Nivolumab (anti PD-1)
What type of antibodies are Ipilimumab (anti CTLA-4), Nivolumab (anti PD-1),
Antagonistic antibodies
What is adoptive transfer of cells
Extract white blood cells from the blood or from the tumour in the form of tumour infiltrating lymphocytes
Can then expand the cells in vitro, using tumour specific antigen (such that only the white blood cells specific to that tumour expand) or just cytokines so that all the white cells expand
Can genetically engineer the T cells i.e. introduce new antigen receptors which identify tumour antigens
Then culture
And re-infuse the white blood cells into the patient
Give an example of genetic engineering in adoptive transfer of cells
So this is when you try to introduce new receptors on T cells to recognise tumour antigens
CARs (chimaeric antigen receptors)
Normally T cells have TCR.
The binding part of the receptor is derived from an antibody.
You can make single chain fragment variable (scFv) which is from the variable part of the antibody. It has a flexible linker sequence
ScFV is then stuck onto a transmembrane pat of a what is essentially a TCR without the binding part
There is a CD3- zeta unit (which is tyrosine phosphorylated when binding occurs for usual CD3) and costimulatory molecule
So binding will initiate TCR activation and cytotoxicity in the tumour cell expressing the antigen
make sure you know the difference between zeta chain and CD3 and TCR
When has CAR been used
The scFv is basically a receptorr for CD19
So the new chimaeric antigen receptor for the T cell is binds CD19 and becomes activated to kill CD19+ cells
This has been used in B cell tumours
