TBL 4 Immunotherapy for cancer

Question 1

What is immunotherapy?

Answer 1

Uses the patient’s own immune system to attack the cancerous tissue by using biological therapeutic agents which can either be antibodies or cells

Question 2

What are the 4 types of immunotherapy?

Answer 2

• Checkpoint inhibition using monoclonal antibodies
• Cancer vaccines
• Administration of antibodies or recombinant proteins to stimulate the immune system
• Transfer of chimeric antigen receptor (CAR) T cells

Question 3

What are ways in which cancer cells stop the immune system from attacking it?

Answer 3

• tumour cells can lose the expression of MHC class I molecules and therefore cannot present new antigens (e.g. antigens encoded by mutated genes) to T cells,
• the tumour develops a way of inhibiting immune responses,
• rapid growth may be too much for the immune system to control the tumour
• perhaps the antigenic peptides do not prime the cytotoxic T cells in the correct way,
• the co-stimulatory molecules required for full T cell activation are not present

Question 4

What is a neoantigen?

Answer 4

A new protein that forms on cancer cells when certain mutations occur in tumor DNA
Neoantigens may play an important role in helping the body make an immune response against cancer cells

Question 5

Name two cytokines that tumour cells can secrete to suppress immune cell activity:

Answer 5

TGFβ- Transforming Growth Factor
IL-10

Question 6

How are cytotoxic CD8 cells important for destruction of tumour cells?

Answer 6

Tumour-specific CTLs
Tumour infiltrating lymphocytes (TILs) are present and have the ability to kill tumour cells.

Question 7

How are helper CD4 cells important for destruction of tumour cells?

Answer 7

Enhance CD8 T cell responses and macrophage responses by producing key cytokines such as interferon-γ and tumour necrosis factor (TNF)

Question 8

How are NK cells important for destruction of tumour cells?

Answer 8

They recognise cells that do not express MHC class I molecules therefore tumours that have lost expression of MHC Class I should be susceptible to attack by NK cells

Question 9

How are macrophages important for destruction of tumour cells?

Answer 9

Can be present in the tumour-infiltrating leukocyte population and are called tumour-associated macrophages (TAMs)
These innate immune cells are capable of killing tumour cells using similar mechanisms to how they kill infectious organisms.

Question 10

What is signal 1 in T cell activation?

Answer 10

Activation of a T lymphocyte through the T cell antigen receptor (TCR) requires presentation of a peptide antigen by an MHC molecule
Different T cells recognise the two classes of MHC molecules, class I (CD8+) and class II (CD4+). This recognition event is essential for T cell activation

Question 11

What is signal 2 in T cell activation?

Answer 11

Need a second signal, co-stimulatory molecules expressed on their cell surface
CD28 is a co-stimulatory molecule expressed on T cells which engages with CD80 or CD86 molecules which are expressed by the antigen-presenting cell (e.g. dendritic cell, B cell).
Signalling through CD28 enhances T cell activation allowing the production of the T cell growth factor IL-2 and beginning the process of clonal proliferation

Question 12

Describe one process which can limit T cell activation and how does this affect tumours?

Answer 12

A molecule called CTLA-4
This is a similar protein to CD28, it is expressed on the T cell surface (usually only following T cell activation)
CTLA-4 engages with the same molecules on the antigen presenting cell as CD28 does; CD80 and CD86
However, the cellular outcome of engaging CTLA-4 on the T cell is inhibitory. This limits T cell activation
Tumours can evade immune responses by expressing proteins that can engage with inhibitory molecules such as CTLA-4 and limiting T cell responses

Question 13

Describe another process which can limit T cell activation:

Answer 13

PD-1 (programmed cell death protein-1) is a second important molecule involved in the inhibition of T cell responses
PD-1 expressed by T cells recognises two ligands known as PD-L1 and PD-L2 which are typically expressed on antigen-presenting cells
Engagement of PD-1 on the T cell causes inhibition of activation

Question 14

Describe checkpoint inhibition immunotherapy:

Answer 14

Both of these molecules, CTLA-4 and PD-1, are responsible for a checkpoint in T cell activation
Overcoming this blockade is one strategy for re-establishing anti-tumour immunity

Question 15

How are regulatory T cells associated with cancer growth?

Answer 15

CTLA-4 is also highly expressed on regulatory T cells or T-regs
These T cells play an important role in suppression of immune responses to prevent autoimmunity
In cancer, there may be an increase in T-regs in the circulation and in the area of the tumour (TILs) and these T-regs may contribute to the suppression of the anti-tumour immune response.

Question 16

Describe checkpoint inhibition using monoclonal antibodies:

Answer 16

The two molecules targeted are CTLA-4 and PD-1/PD-L1
To do this monoclonal antibodies are used that stop these cell surface proteins from engaging with their ligands
This effectively stops the T cell inhibition and allows anti-tumour immune responses to proceed
Anti-CTLA-4 antibodies are also thought to deplete T-regs and therefore prevent this type of immune suppression

Question 17

What types of cancers are treated using checkpoint inhibition?

Answer 17

Melanoma, lung carcinoma, renal carcinoma, bladder carcinoma, colon carcinoma and non-Hodgkins lymphoma

Question 18

Name three monoclonal antibody checkpoint inhibitors and their targets:

Answer 18

Ipilimumab- CTLA-4
Nivolumab- PD-1
Atezolimumab- PD-L1
Combination of these has been more effective

Question 19

What are some adverse affects of checkpoint inhibitors?

Answer 19

Autoimmune and inflammatory reaction
Severe Cutaneous Adverse Reactions (SCARS)

Question 20

What is the aim of cancer vaccinations in someone who has a tumour?

Answer 20

To boost the cytotoxic CD8+ T cell response that recognise the tumour cells

Question 21

What do cancer vaccinations contain?

Answer 21

Killed tumour cells from the patient, recombinant tumour antigens, or dendritic cell vaccines

Question 22

How are dendritic cells involved in cancer vaccination?

Answer 22

Dendritic cells are taken from patients and incubated with tumour antigens in a laboratory (ex vivo)
The dendritic cells are then injected back into the patient allowing the dendritic cells to present the tumour antigen to T cells

Question 23

Give an example of a dendritic cell cancer vaccination:

Answer 23

Treat prostate cancer
The dendritic cells are loaded with a prostate specific antigen called prostatic acid phosphatase and treated with GM-CSF (an adjuvant which promotes the maturation of the dendritic cells)
Not lisenced in UK but in the US it is

Question 24

Name and describe a preventative cancer vaccination:

Answer 24

Viral antigens that are known to be oncogenic
HPV is one such virus associated with carcinomas of the cervix, oropharynx and other sites

Question 25

Who is eligible for the HPV vaccination?

Answer 25

Girls and boys aged 12 and 13
Then second dose 6-24 months after
Can have one before 25 if missed a routine one

Question 26

How does Rituximab work?

Answer 26

Anti-CD20 antibodies
Can be used to deplete all cells expressing CD20 (a cell surface marker of B cells)

Question 27

Describe IL-2 as an immune modulator:

Answer 27

Is used clinically to treat melanoma and renal cell carcinoma
It is given at a high dose and can stimulate production of inflammatory cytokines such as TNF-α and IFN-γ which can cause serious side effects.

Question 28

Describe IFN-α as an immune modulator:

Answer 28

For the treatment of several cancers including melanoma, lymphomas, and leukaemias
This cytokine will increase the action of NK cells and help upregulate MHC class I expression on tumour cells thus promoting the cytotoxic action of CD8+ T cells

Question 29

What does CAR stand for in immunotherapy?

Answer 29

Chimeric Antigen Receptors

Question 30

What does chimera’s mean?

Answer 30

Something that contains pieces derived from two or more sources

Question 31

What type of immunotherapy are CAR T cells and why?

Answer 31

Adoptive therapy
Immune cells are derived from the patient’s blood and expanded in vitro before being reinfused into the patient

Question 32

What are CAR T cells?

Answer 32

Genetically engineered receptors which have specific antigen-binding sites allowing the treatment to be directed to a specific tumour-bearing antigen
Chimera’s of an immunoglobulin variable gene and the cytoplasmic tails containing the relevant signalling domains of the TCR and co-stimulatory molecules
These include the ITAM of a TCR and the intracellular signalling domain of CD28

Question 33

How does CAR T cell immunotherapy work?

Answer 33

Peripheral blood is taken from the patient and T cells are isolated
The T cells are then put into culture and stimulated to expand using antibodies to the CD3 complex and antibodies to the CD28 co-stimulatory molecule
These expanded T cells are then transfected with viral vectors encoding the genetically engineered CAR
The T cells are then injected back into the patient where they undergo further proliferation in response to tumour antigen recognition events by the newly expressed CAR

Question 34

Which cancers can CAR T cell therapy treat and why?

Answer 34

B cell malignancies such as lymphoma have been successfully treated using this therapy
CAR T cells recognising the CD19 B cell surface marker can eradicate all B cells from the patient (both tumour B cells and normal B cells

Question 35

What are some adverse effects of CAR T cell immunotherapy?

Answer 35

Due to the high number of activated T cells in the patient, this type of therapy can cause an intense systemic inflammatory response or cytokine release syndrome
There is also a number of reported neurological complications such as cerebral oedema which has led to fatalities.