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IMM005 > The immune system fighting cancer > Flashcards

The immune system fighting cancer Flashcards

1
Q

What does an inadequate immune system predispose to?

A

Chronic infection

Cancer

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2
Q

What does an overactive immune system cause?

A

Autoimmune conditions

Type I diabetes
Arthritis
Scleroderma

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3
Q

What is immunotherapy?

A

Employing the immune system to

  • enhance immunity in patients with cancer and chronic infection
  • induce tolerance in autoimmune diseases
  • develop therapies for inherited diseases
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4
Q

What is the potential for immunotherapy in cancer?

A

Help develop a new generation of live medicine

Providing lasting clinical benefit for patients

Potential to replace chemotherapy and radiation therapy

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5
Q

What is cancer?

A

A genetic disease

Developing from normal cells

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6
Q

Describe the potential for cancer development

A

The individual probability for cancer to develop in a cell is small

However, since there are 10^13 cells in the body, the cumulative risk is relatively high

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7
Q

What do genes control?

A

Cell function

Cell shape

Cell growth

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8
Q

What is the consequence of mutated genes?

A

Uncontrolled cell growth

Production of new proteins

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9
Q

Why is cancer rare in individual cells?

A

Evolutionary mechanisms for eliminating of inactivating potentially dangerous cells

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10
Q

Describe the process of oncogenic evolution

A

Elimination:
Once a cancer cell has been formed, immune surveillance attempts to eliminate it

Equilibrium:
Some of the cancer cells develop immune resistance mechanisms, allowing them to escape the elimination phase.

The immune system keeps track of these cells, forming an equilibrium

Escape:
Some of the cells in equilibrium with the immune system escape from the immune syste, leading to progressive disease

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11
Q

When does the escape phase of oncogenic evolution take place?

A

When there is a change in the tumour cells or the microenvironment which causes the immune system to be switched off in some way to allow the tumour to grow

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12
Q

What is essential for the clinical manifestation of cancer to present?

A

Escape phase

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13
Q

Experimental evidence of immunoediting during oncogenic evolution

A

Immunogenic tumours (aka tumours that can be recognised by the immune system) arise in immunodeficient mice

Progressive tumour variants arise in normal mice (immunoedited so immune system can not recognise it)

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14
Q

Which cell is essential for cancer immunoediting?

A

T cell

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15
Q

Describe an important mouse study showing the importance of immunoediting for cancer cells

A

Cancer cells from an immunocompetent mouse was injected into an immunocompromised recipient = cancer developed

Cancer cells from immunocompromised mouse was injected into an immunocompetent recipient = no cancer

Cancer cells from immunocompromised mouse was injected into an immunocompromised recipient = cancer developed

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16
Q

Examples of prophylactic cancer vaccines

A

HBV vaccines

HPV vaccines

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17
Q

Have prophylactic cancer vaccines been effective in reducing the chances of developing cancer?

A

Yes

Vaccinating before viral infection

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18
Q

Which cancer does HBV vaccines protect against?

A

Liver cancer

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19
Q

Which cancer does HPV vaccines protect against?

A

Cervical cancer

20
Q

Example of a therapeutic vaccine used in cancer

A

Dendreon’s Provenge

Prostate cancer cell vaccine produced with patients own cells

21
Q

Have therapeutic vaccines been useful in cancer?

A

Not as effective as other immunotherapies

22
Q

Which cells play an important role in cancer protection?

A

T cells

23
Q

Describe the activation of T cells

A

TCR recognises the target cell through peptides presented on MHCs of APCs

This is called signal 1

On top of this, signal 2 is also needed

In the absence of costimulatory signals, signal 1 is ineffective

24
Q

What are the two types of T cell co-receptors?

A

Co-stimulatory -> cause T cell activation

Co-inhibitory -> prevent T cell activation

25
Q

Examples of stimulatory co-receptors

A

PDL1

CD80/86 binding to CD28

CX40L

CD70

26
Q

Examples of inhibitory co-receptors

A

CD80/86 binding to CTLA4

PDL1 binding to PD1

27
Q

How do cancers shut down the immune system?

A

Inhibit T cell activation following signal 1 by expressing inhibitory co-receptors like PD-1, or inhibitory molecules like CD80/86 binding to CTLA-4

28
Q

What are immune checkpoint inhibitors?

A

Bind and block inhibitory receptors on T cells

Induce immune system activation through blocking inhibitory receptors

Including PD-1 and CTLA-4

29
Q

Examples of checkpoint inhibitor drugs

A

Ipilumumab

anti-PD-1

30
Q

What is the only challenge of checkpoint inhibitors?

A

Autoimmune side-effects

Global T cell activation due to the blocking of PD-1 and CTLA-4

Important regulators of normal immune balance

31
Q

When are checkpoint inhibitors used?

A

In patients resistant to conventional therapies

32
Q

Describe alternatives to conventional therapies currently being developed

A

Checkpoint inhibitors

Tumour infiltrating lymphocytes

Engineered T cells

33
Q

Describe the idea behind using tumour infiltrating lymphocytes for cancer therapy

A

Extraction of T cells present in the tumour microenvironment and their subsequent expansion

Since they have tumour specificity

34
Q

How do we have to prepare the patient before using tumour infiltrating lymphocytes?

A

Reduce the levels of endogenous T cells before you inject the expanded T cells

So the tumour-specific T cells don’t have to compete for space

35
Q

What is the advantage of tumour-specific T cells in cancer therapy?

A

They have multiple specificities against neo-antigens and tumour-associated antigens

36
Q

What are the disadvantages of using tumour-specific T cells in cancer therapy?

A

Difficult to reliably obtain T cells from cancer patients

Unknown fine specificity of T cells

Generally unsuccessful in cancer types other than melanoma

37
Q

Describe the process behind engineering T cells

A

Isolate T cells from peripheral blood

Genetically engineer T cells to direct them towards cancer antigen using TCR or CAR

Reinject the cells back into the patient

38
Q

What is the difference between CAR and TCR?

A

CAR is the addition of the variable portion of antibody onto a chimeric antigen receptor

Genetically engineer the T cell receptor to be specific to a certain antigen

39
Q

What is the benefit of using TCR instead of CAR in engineering T cells?

A

TCR recognise intracellular peptides through the MHC presenting system due to the nature of TCR proteins

CAR T cannot recognise intracellular peptides

40
Q

Success of genetically engineered T cells

A

CAR T cells have been successful for acute lymphoid leukemia

Genetically modified T cells have shown tumour regression in patients with metastatic synovial cell melanoma and sarcoma

41
Q

Which mutations are targeted by T cell therapy?

A

Mutations present in the coding portions of the genome

So it can be loaded on the HLA and presented to the lymphocytes

42
Q

What is the biggest challenge in cancer therapy?

A

Every patient has a unique set of mutations

This personalised therapy is a limitation

43
Q

What is the current goal of cancer therapies?

A

Targeting tumour associated antigens present in all patients

Removes the challenge of personalised therapy

Biggest success = CD19

44
Q

What are the disadvantages of targeting tumour associated antigens present in all patients?

A

Risk of autoimmune disease

Induction of T celinl tolerance by normal tissues

45
Q

Which type of mutations create novel protein sequences?

A

Non-synonymous

Mutation causes a change in the protein expressed

Since DNA is redundant, mutations are not always caused following DNA changes

46
Q

What percentage of the genome is the protein coding exome?

A

1%

IMM005 (17 decks)

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