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Immunopathology and applied immunology > 16. T cell therapy and cancer > Flashcards

16. T cell therapy and cancer Flashcards

1
Q

Why do we need novel approaches to cancer treatment?

A
  1. ~375,000 new cancer cases every years in the UK.
  2. Every 2 mins someone in the UK is diagnosed with cancer.
  3. Projections suggest that this could rise to ~500,000 new cases a year by 2038.
  4. It is one of the 3 leading causes of death alongside Infectious disease and cardiovascular disease.
  5. There are ~167,000 cancer deaths in the UK every year.
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2
Q

What does successful cancer treatment require?

A

Removal or destruction of all malignant cells without killing the patient.

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3
Q

What is immunotherapy?

A
  1. Immunotherapy is using the immune system to recognised and eliminate cancer cells.
  2. It could allow precise targeting of cancer cells without killing healthy cells or the patient.
  3. It can be combine with surgery or chemo to reduce the cancer load first.
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4
Q

When was immunotherapy first considered as a cancer therapy?

A
  1. 2013.
  2. There was lots of work on it prior to this but this is the point is was thought to be viable.
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5
Q

Why are T cells the focus of cellular immunotherapy?

A

They are the cells that can recognise and kill cancer cells.

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6
Q

What immunotherapies are already licensed?

A
  1. IL-2 therapy
  2. Checkpoint blockade
  3. CAR-T cell therapy
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7
Q

What indicates that immunotherapy is very promising for the future of cancer treatment?

A
  1. The big funders of cancer research include immunotherapy in their specific funding plans.
  2. This is to fulfil the aim to improve long term survival rates.
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8
Q

What immune cells mediate tumour rejection?

A

T cells

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9
Q

How were T cells proved to mediate tumour rejection?

A
  1. A key experiment transplanted tumours into inbred mouse strains where the host and tumour matched in MHC type.
  2. The majority of transplanted tumours grow and progressively kill the mice.
  3. Some mice were immunised with irradiated tumour and then challenged with viable tumour cells from the same tumour.
  4. These mice rejected that tumour.
  5. When the same experiment was carried out in T cell deficient the same was not seen.
  6. Therefore tumours expressing tumour rejection antigens that become targets for the T cell response mediates tumour rejection.
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10
Q

What happens between cancer cells and immune cells during development of tumours?

A

Lots of interplay and interactions as the immune cells try to control the tumour

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11
Q

What are the 3 phases of tumour growth?

A
  1. Elimination and immune surveillance: There is recognition and destruction of tumour cells and the tumour is under control.
  2. Equilibrium phase: Tumours under changes/mutations that enhance its survival. This is cancer immunoediting and it shapes the properties of the surviving tumour.
  3. Escape phase: The tumour escapes the immune response and grows out of control.
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12
Q

What kinds of challenges need to be overcome to elicit an effective immune response to tumours?

A

Strategies the tumour uses to avoid immune recognition

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13
Q

What strategies do tumours use to avoid immune recognition?

A
  1. Low immunogenicity
  2. Tumour is seen as self.
  3. Antigenic modulation.
  4. Tumour induced immune suppression.
  5. Tumour induced immune privileged site.
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14
Q

Strategies tumours use to avoid immune recognition: low immunogenicity

A
  1. Tumours down regulation MHC 1 (or MHC 2 if relevant) expression on tumour cells to hide from the immune response.
  2. They also don’t express adhesion molecules.
  3. No expression of co stimulatory molecules.
  4. These all contribute to low immunogenicity.
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15
Q

Strategies tumours use to avoid immune recognition: Tumour is seen as self

A
  1. Tumour antigens are self antigens and even if altered they can be seen as self by the immune system.
  2. So when T cells recognise the tumour antigen on APC there can be a lack of co stimulation so the T cell is not effectively activate or anergy is induced.
  3. T cells don’t recognise the tumour very well and don’t mount an effective immune response.
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16
Q

Strategies tumours use to avoid immune recognition: Antigenic modulation

A
  1. Antibodies against tumour cell surface antigens can bind and then be endocytosed.
  2. This internalises the antibody and the antigen.
  3. The antigen is degraded and depleted from the surface.
  4. This leads to antigen-loss variants of cancer cells which can escape immunity.
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17
Q

Strategies tumours use to avoid immune recognition: Tumour induced immunosuppression

A
  1. Soluble factors can be excreted by tumour cells to inhibit T cells directly. This includes TGFß, IL-10 and IDO.
  2. Tumour can induce Tregs
  3. Tumours can express PD-L1 which negatively stimulates immune cells through PD1 binding.
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18
Q

Strategies tumours use to avoid immune recognition: Tumour induce immune privileged site.

A
  1. Tumour cells in TME can secrete factors to create a physical barrier around the tumour.
  2. This prevents immune cell access to the tumour.
  3. eg secretion of collagen
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19
Q

What cells most commonly recognise and kill cancer cells?

A

CD8 T cells

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20
Q

How can CD4 T cells aid CD8 T cells to kill cancer cells?

A
  1. They play a role in activating CD8 cytotoxic T cells
  2. Establishing T cell memory.
  3. Killing tumour cells via cytokines like TNFa
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21
Q

What do T cell immunotherapy approaches focus on?

A

The use of CD8 T cells.

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22
Q

What other approaches to T cell immunotherapy are there?

A
  1. Using CD4 T cells in combination with CD8 T cells.
  2. Using gamma delta T cells.
  3. using mucosal associated invariant T cells.
  4. Using NK cells
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23
Q

How do CD8 T cells recognise their targets?

A
  1. Tumour transformed cells have abnormal proteins but they are often buried within the cell.
  2. To overcome this cytosolic proteins are processed and present at the cell surface in MHC class 1 molecules.
  3. CD8 T cells recognise small peptide fragment present in the context of MHC1 through its TCR.
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24
Q

What receptor interactions occur to activate a CD8 T cell?

A
  1. The tumour antigen is presented on MHC1 on the cancer cell or APC.
  2. The T cell uses the TCR and the CD8 co-receptor to recognise this and both interactions are needed.
  3. The TCR binds the peptide and the peptide binding groove on the MHC. This gives specificity and recognition.
  4. The CD8 co receptor binds to MHC1 at a different point which enhances T cell sensitivity.
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25
Q

What happens if you manipulate the CD8 MHC1 interaction?

A

You can fine tune T cell sensitivity.

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26
Q

What do you need to specifically target a tumour with T cells?

A
  1. You need to identify a good tumour antigen.
  2. It needs to be expressed by the tumour.
  3. Ideally you want it to limited expression elsewhere.
  4. This is challenging and rare to find.
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27
Q

What are most tumour antigens?

A
  1. Self antigen.
  2. They are normally just overexpressed or expressed at the wrong time on tumour cells.
  3. This means they are also expressed on normal tissue which could lead to off target effects.
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28
Q

What is an example of off target effects in immunotherapy?

A
  1. T cell therapy can be used to melanoma.
  2. This can cause the side effect of vitiligo.
  3. You need to weigh up the pros and cons of the treatment and side effects.
29
Q

Why do tumour specific antigens often have low affinity for TCR?

A
  1. Tumour specific antigens are or similar to self antigens.
  2. So naturally occurring TCRs with high affinity for these self antigens are deleted in thymic negative selection
  3. This means any TCRs that do see the tumour antigen do so with low affinity.
  4. This makes the T cell harder to activate as it is hard to get it over the activation threshold.
30
Q

Are tumour specific antigens high affinity for TCRs?

A
  1. No
  2. They are low affinity as they are normally self antigens
31
Q

How can low affinity TCRs be overcome to treat cancer?

A

You can take a low affinity TCR that can recognise tumour antigens and engineer them to be higher affinity.

32
Q

What is the goal of immunotherapy?

A

To harness and enhance the ability of the immune system to recognise and destroy cancer cells.

33
Q

What kinds of immunotherapy are there?

A
  1. Cancer vaccination
  2. Checkpoint blockade
  3. Adoptive transfer therapy
  4. Genetic engineering of T cells (TCRs, high affinity CD8 and CAR)
  5. Use of soluble TCRs.
34
Q

What is adoptive T cell therapy and how does it work?

A
  1. A treatment used to help the immune system fight disease like cancer or certain viral infections.
  2. T cells are collected from a patient and grown in the lab.
  3. This increases the number of T cells that are able to kill cancer cells or fight infections.
  4. They are grown with cytokines to stimulate and re activate them.
  5. These T cells are given back to the patient to help the immune system fight disease.
35
Q

What is adoptive TIL therapy and how does it work?

A
  1. Adoptive tumour infiltrating lymphocyte therapy.
  2. Surgical resection of the tumour is done to get the T cells out of the tumour.
  3. These are them expanded using a rapid expansion protocol.
  4. This then generates an infusion product to put back in the patient.
36
Q

What is a rapid expansion protocol?

A
  1. A method used to rapidly expand TILs.
  2. It involves mixing the TILs with IL-2, anti-CD3 antibodies and irradiated feeder cells.
  3. The feeder cells provide signals and cytokines to the TILs.
  4. Anti-CD3 triggers the TILs TCR to activate the T cells.
  5. IL-2 supports T cell proliferation.
37
Q

How effective is adoptive TIL therapy?

A
  1. It has been tried for many years and you can get really good responses from patients like tumours shrinking or disappearing.
  2. It has mainly been tested in melanoma.
  3. A proportion of patients will always have no response to a treatment but we don’t really know why.
  4. Response rates depend on treatment approach.
  5. It can be given with other things like lymphodepletion, IL-2 therapy, or Neoantigen specific TILs.
38
Q

When was the 1st adoptive TIL therapy approved?

A
  1. Feb 2024
  2. This was Lifileucel
  3. It is used to treat unresectable or metastatic melonoma which has already failed anti-PD1 treatment.
  4. It has a 4 year survival rate of about 20%
39
Q

How can T cells be genetically engineered to enhance their activity?

A
  1. T cells are isolated from the blood and cultured in vito with cytokines like IL-2, IL-7, IL-15 and IL-21.
  2. The T cells are genetically modified using vectors that encode receptors or molecules that enhance response to cancer cells.
  3. These genes are incorporated into the T cell genome and expressed.
40
Q

What receptors do we want to genetically engineer T cells to have?

A
  1. Higher affinity cancer specific TCRs.
  2. CARs (chimeric antigen receptors)
  3. CD8 with higher affinity to MHC1 to help recognition of the cancer antigen
41
Q

What vectors are used in T cell engineering?

A
  1. The most common are retroviruses and lentiviruses.
  2. These are engineered to be replication incompetent by removing vital viral proteins.
    (see FID viral vectors lecture).
  3. These gutless vectors helped remove some safety concerns around using viral vectors.
42
Q

What are the advantages of genetic engineering T cells to express cancer specific TCRs?

A
  1. You can generate large numbers of cancer specific CD8 T cells in a very short space of time to a specific cancer antigen like NY-ESO-1.
  2. You can also insert mutations in the TCR that increases the affinity of the TCR for the cancer antigen.
43
Q

What are the disadvantages of genetic engineering T cells to express cancer specific TCRs?

A
  1. You need to identify a suitable MHC1 restricted tumour rejection antigen.
  2. You need to isolate a tumour specific TCR which can be very challenging.
  3. Increasing the affinity of a TCR may result in loss of specificity or creation of new specificities which could lead to side effects.
  4. Mispairing of the endogenous and engineered TCRs
  5. Restriction by a specific MHC1 can only be used on patients that express that MHC1 type.
44
Q

How can you engineer TCRs to be higher affinity for cancer specific antigens?

A
  1. You can use phage displays to find amino acid substitutions in the CDR3 region of the TCR.
  2. This increases the affinity of the TCR and aids T cell activation.
45
Q

Why do you need to be careful when changing TCR affinities?

A
  1. This could mean the TCR could recognise an antigen it didn’t previously.
  2. This could be a self antigen.
  3. It could cause side effects like toxicity or death.
46
Q

What is TCR mispairing?

A
  1. Each engineered T cell has their own TCR and you are adding another TCR to it.
  2. This means 1 chain of the native TCR could pair with the other chain of the added TCR.
  3. This creates a whole new TCR which could recognise self antigens.
  4. You can design vectors to avoid this.
47
Q

What are CAR T cells?

A
  1. Engineered T cells that take advantage of the ability of T cells to activate and kill cancer cells.
  2. However they are not activated through their TCR but through a chimeric antigen receptor (CAR).
48
Q

What is the chimeric antigen receptor?

A
  1. CAR is an extracellular domain that is a single chain antibody specific for a cancer antigen.
  2. This allows high affinity recognition of a can cell antigen
  3. Have a hinge region to cross the plasma membrane
  4. Intracellularly they have a co stimulatory domain (CD28 or 4-1BB) and have a CD3 zeta signalling chain.
  5. This is non MHC restricted so as long there are cancer cells with that targeted antigen you can use CAR T cells without worrying about the patient MHC/HLA type.
49
Q

What are the different generations of CAR T cells?

A

1st generation: Contains that CAR and intracellular CD3 zeta
2nd generation: Contains CAR, intracellular CD3 zeta, and a co stimulatory domain either CD28 or 4-1BB
3rd generation: Contains CAR, intracellular CD3 zeta, and 2 co stimulatory domains CD28 and 4-1BB.
4th generation: 3rd generation with the addition of ‘armoured’ CARs or cytokine expressing CAR T cells.

50
Q

What are cytokine expressing CAR T cells?

A
  1. These are CAR T cells that have also been engineered to produce and secrete cytokines as well.
  2. This enhances the function of the CAR T cells.
  3. It provides activation signal 3 straight to the T cell.
51
Q

How is CAR T cell therapy done?

A
  1. T cells are harvested from the patient.
  2. A viral vector is used to deliver the CAR encoding genes to the T cell genome.
  3. This makes lots of T cells that express CAR.
  4. Then the T cells are expanded.
  5. This is used to generate an infusion product to give back to the patient.
52
Q

What CAR T cell therapies are approved for clinical treatment?

A
  1. There are 6 FDA approved CAR T cell therapies for B cell malignancies and multiple myeloma.
  2. Kymriah is an anti-CD19 CAR T cell therapy that was approved in 2017 for the treatment of paediatric and young adult acute lymphoblastic leukaemia.
53
Q

What are the severe adverse events associated with CAR T cell therapy?

A
  1. Cytokine release syndrome
  2. On target off tumour toxicity: This is the T cell responding to healthy tissue that expresses the same antigen as the tumour eg anti-CD19 CAR T cells causing depletion of normal B cells.
  3. Immune effector cell associated neurotoxicity syndrome.
  4. Post CAR T cell therapy infections which are often the cause of mortality rather then cancer relapse.
54
Q

What is cytokine release syndrome?

A
  1. It is a severe reaction mediated by cytokines.
  2. Mostly IL-1 and IL-6.
  3. Symptoms include fever, hypertension and systemic symptoms.
  4. Can be treated with anti-IL6 receptor antibody tocilizumab
55
Q

What are the challenges of CAR T cell therapy?

A
  1. It is a highly personalised treatment so it is very expensive.
  2. It is not very effective against solid tumours which make up 90% of cancers.
  3. Currently these T cells can’t be switched off once they have served their purpose and this could become a requirement in the future.
56
Q

What could T cell be engineered to do?

A
  1. Enhance their activity.
  2. Enhance specificity.
  3. Increase T cell survival
  4. Increase proliferation
  5. Improve Trafficking
  6. Overcome the TME
  7. Improve safety
57
Q

What could be engineered on T cells to increase specificity?

A
  1. The TCR
  2. CAR
58
Q

What could be engineered on T cells to enhance activity?

A
  1. Increase TCR or CAR affinity.
  2. Addition of signalling domains.
  3. Decrease TCR mispairing
59
Q

What could be engineered on T cells to increase T cell survival?

A
  1. Downregulation of FAS or BID.
  2. Upregulation of BCL-X and BCL-2
  3. Stem cells
60
Q

What could be engineered on T cells to increase proliferation?

A
  1. CD137 and CD134 CARs
  2. Addition of cytokines or their receptors.
61
Q

What could be engineered on T cells to increase trafficking?

A
  1. CXCR2
  2. CCR4
  3. CCR2B
  4. VEGFR2 CAR
62
Q

What could be engineered on T cells to increase safety?

A
  1. Thymidine kinase
  2. inducible caspase 9
  3. CD20
63
Q

What could be engineered on T cells to overcome the TME?

A
  1. upregulation of AKT
  2. PD1-CD28 chimaera
  3. IL-12
64
Q

What are ImmTacs?

A
  1. A soluble therapy which combines a high affinity, affinity maturated TCR for a cancer cell antigen MHC complex
  2. These TCRs will coat any cancer cell that expresses this antigen
  3. This is fused with a stimulatory anti-CD3 epsilon antibody fragment.
  4. This redirects and activates the patient’s bystander T cells to kill the cancer cells.
  5. The TCR needs to be high affinity.
  6. The anti-CD3 antibody is to activate the CD3 region of the TCR on the bystander T cells to activate and redirect the T cell to kill the cancer cells.
65
Q

What are the advantages of ImmTacs?

A
  1. They are a soluble therapy that doesn’t require altering cells.
  2. It can be manufactured a delivered like a drug.
66
Q

What are some of the side effects associated with ImmTacs?

A
  1. Cytokine mediated events involving T cell activation.
  2. Skin related events including rash, pyrexia and pruritis.
67
Q

What ImmTacs is approved for use?

A
  1. Tebentafusp-tebn is an ImmTac which is specific for a HLA-A0201 restricted epitope from GP-100.
  2. It has improved overall survival in uveal melanoma.
  3. It was approved to treat unresectable or metastatic uveal melanoma.
68
Q

What are checkpoint inhibitors?

A
  1. T cells within the immunosuppressive TME express a range of co inhibitory receptors such as PD-1, CTLA4, TIM3, Lag3 and TIGIT.
  2. Engagement of these co inhibitory receptors deliver a negative signal to the T cells to which prevent them from activating.
  3. Monoclonal antibodies that block PD-1 and CLTA4 have been developed and are being used to treat humans with metastatic melanoma.
  4. This reverses the immunosuppressive signalling of the TME and helps reactivate the T cells.
  5. They have amazing clinical responses in patients but ~60% do not respond and there are side effects.
  6. Other cancers are being explored for checkpoint inhibition as well as using checkpoint inhibitors in combination with T cell therapies.
  7. Cheaper then cellular therapies
69
Q

Why is there only 1 approved CAR T cell therapy?

A
  1. We cannot find any other cancer specific antigen that can be targeted without significant side effects .
  2. CD19 in B cell cancers can be targeted as Antibodies and B cells can be supplemented during treatment and can recover after treatment.

Immunopathology and applied immunology (17 decks)

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