Tumour immunology and immunotherapy of cancer

Question 1

what does a T cell look like

Answer 1

protusions on the surface

Question 2

how can breast cancer cause a previously health women, 53 yrs, to awake dizzy with severe vertigo, unintelligible speech, truncle and appendicular ataxia (abnormal movements) - then progress to being unable to sit, stand, use hands *

Answer 2

immune involvement - detection of anti-CDR2 Ab in serum by seeing brown colour on stain - peroxidase bound to the Ab when add dye = brown colour

spontaneous immune response against tumour-expressed Ag results in auto-immune disease

body made Ab response against tumour - Ab gone to brain = autoimmune neurological disease

purkunje cells express Ag that is expressed by the tumour, so are destroyed by the Ab

Question 3

what is shown by the fact that there is immune involvement in tumours *

Answer 3

that we can make a humoral anti-tumour response

at least certain tumours express Ag that are absent from or not detectable in normal tissue

the immune system can, in principle, detect the Ag and attacl tumur

in some cases may cause auto-immune destruction against normal tissue which limits development of medicine exploiting this

Question 4

circumstantial evidence for immune control of tumours in humans *

Answer 4

immunotherapy works

autopsies of accident victims have shown many adults have microscopic colonies of cancer cells with no symptoms of disease - immune system possibly control the mini-tumours so that they dont cause symptoms

patients treated for melanoma have been used for donor transplants mant years after being cleared from disease - transplant recipients have then developed tumours - donor had developed immunity to melanoma

deliberate immunosuppression increases risk of malignancy

men have twice as great chance at dying from malignant cancer than women, women ammount stringer immune responses - indirect evidence

concept of immunosurveillance - malignant cells are controlled by the action of the immune system

Question 5

what is the role of immunotherapy *

Answer 5

to enhance the immune responses to cancer *

Question 6

describe T cells *

Answer 6

aB TCR

MHC restricted - MHC molecules present peptide Ag

there are class 1 and 2 MHC molecules

Question 7

describe B cells *

Answer 7

BCR - surface Ig

can detect a vast range of molecules - dont have to be presented by MHC

eg Ab can neutralise viruses

Question 8

describe the cancer immunity cycle *

Answer 8

1. release of cancer cell antigens and cancer cell death
2. APC (ie dendritic cells) capture the cancer Ag and migrate to lymph nodes and present them to recirculating T cells
3. T cell activated and Ab response
4. T cell traffic back via blood to tumour cells
5. T cells go into the tumours by the endothelial layer - these are tumour infiltrating lymphocytes
6. once on tumour, of tumour present peptide from Ag that T cell can recognise - T cell will destroy the tumour cell = release of more Ag which are captured by APC

Question 9

describ ethe relationship between the tumour and immune system *

Answer 9

tumour growing all the time

immune system trying to destroy it

immune system provides a selection pressure - any cell that has escaped from T cell recognition proliferates

eg if tumour cell doesnt make MHC - wont be klilled = selective increase of these varients

Question 10

describe the cancer immunity cycle *

Answer 10

the lymphocyte response is up and down regulated

chemicals are important in activating and killing are molecules we can target in immune checkpoint blockade

ie activating T cell - CTLA4/B7.1, PD-L1/PD-1, PD-L1/B7.1

killing of cancer cells - PD-L1/PD-1, PD-L1/B7.1

we can improve the immune response by downregulating these inhibitory factors

Question 11

what are the 2 ways that we can increase an immune response *

Answer 11

increase it - boost it positively

or reduce the down regulation of it

Question 12

describe the initiation of cancer and immune involvement *

Answer 12

usually results from sporadic events over time - irradiation, chemical mutagens, spontaneous errors during DNA replication, tumour induced changes in genome

cancer is genetic

mutations accumulate in DNA affect the cell cycle and growth = tumour growth

when tumours reach a certain size they cause enough damage to release inflammatory signal

this recruits cells of innate immunity eg macrophages, DCs and NKs

DC present Ag from tumour to T cells - lead to adaptive immune responses (T cells and B cells producing Ab)

Question 13

what are the requirements on an adaptive anti-tumour immune response *

Answer 13

local inflammation in tumour - danger signal - Ag alone is not enough

expression and recognition of tumour Ag

Question 14

what are the problems with immune surveillance of cancer *

Answer 14

it takes a while for tumour to cause local inflammation

antigenic differences between normal and tumour cells can be very subtle - eg a small number of point mutations - difficult to pick up

Question 15

how does cancer immunotherpy relate to normal patholgy *

Answer 15

if the requirements for spontaneous actiavtion of the adaptive immune response are not met - can teach the adaptive immune system to selectively detect and destroy tumour cells

Question 16

how can immunotherapy be used *

Answer 16

alternative

or supplement to conventional therapies ie surgery, chemo, radiotherapy

Question 17

how do immune responses to tumours have similarities to virus infected cells *

Answer 17

most of the mutations affect intracellular proteins - T cells see peptide fragments presented by MHC molecules that are representative of the proteins in cells (can be some caes where tumour express Ag on surface that can be detected by Ab)

the function of the MHC molecules is to present conents of cell for surveillance by T cells - infection/carcinogenesis

Question 18

what are tumour specific ag *

Answer 18

proteins that are only found in tumour cells

Question 19

examples of tumour specific antigens *

Answer 19

viral proteins are not found in healthy cells - certain viruses are found in certain tumours eg EBV and HPV

mutated cellular proteins eg TGF-B - the change in aa sequence have potential to be detected by immune system

chromosome translocations can be associated with tumours eg Bcr-abl - fusion generates a new sequence that is not found in normal cells

Question 20

cancers of viral origin *

Answer 20

opportunistic malignancies when people are immunosuppressed

• EBV-positive lymphoma, because of post transplant immunosuppression
• HHV8-positive kaposi sarcoma - when have HIV
• CMV - lymphomas

in immunocompetent individuals

• HTLV-1 associated leukaemin/lymphoma
• HepB virus and HepC virus-associated hepatocellular carcinoma
• HPV positive genetal tumours

Question 21

describe HPV and cervical cancer *

Answer 21

there are 6 types of HIV associated with cervical cancer

the rumour cells express viral Ag

there is internal proliferation of viral cells = downregulation of the cell cycle = aberrent cell growth - important in onchogenesis

cancer is induced and maintained by E6 7 oncoproteins of HPV - these are intracellular - peptides are presented on cell surface and can be recognised by T cells

Question 22

describe the HPV vaccine *

Answer 22

it uses viral surface proteins to make virus like particles

no DNA is involved so no risk of giving people onchogenes

Gardisil 9 is the most common vaccine - contains 9 subunits for different subtypes - has reduced the incidence of cancer - helps protects girls and boys aged 9-26 against cervical, vaginal, vulvar, anal cancer and genital warts

Question 23

describe the relation between consequences of cervical HPV infection and HPV-specific T cell immunity *

Answer 23

most people when infected by HPV16 have a string immunity anyway = clearance of HPV-infection

minority have immune failure when infected = cervical neoplasia - 50% of them have no immunity, other 50% have non-functional immunity - in this minority we can give HPV vaccine as a therapeutic vaccine - effective after early signs of the disease

Question 24

what are tumour associated antigens *

Answer 24

they are normal cellular proteins that are aberrantly expressed ie wrong time, place or quantity

Question 25

describe the problem with immunotherapy against tumour associated antigens \*

Answer 25

they are normal self proteins so immune system is tolerant of them - the body deletes or regulates self-reactive lymphocytes - causes tolerance this tolerance needs to be overcome to elicit an immune response

Question 26

describe tolerance induction by the thymus \*

Answer 26

-ve and +ve selection of T cells - get rid of autoreactive T cells need self-MHC-restricted and self tolerant T cell repertoire the positively selected T cells are exported to the periphery there is some auto-reactivity - T cells recognise themselves but are not activated - these are what we try to activate in immunotherapy - problem is we might generate auto-immunity if tissues express the same Ags

Question 27

examples of tumour associated antigens - ectopically expressed auto-antigens \*

Answer 27

cancer testes antigen (developmental antigen) - silent in normal adult tissue except male germ cells and some in placenta MAGE family - melanoma associated antigens - identified in melanoma but also expressed in other tissues - few are on surface but mainly internal proteins presented by MHC molecules and recognised by T cells

Question 28

other examples of tumour associated antigens \*

Answer 28

human epidermal growth factor receptor 2 (HER2) - overexpressed in some breast carcinomas (this is a target for therapy) Mucin 1 (MUC-1) membrane associated glycoprotein, overexpressed in many cancers carcinoembryonic antigen (CEA) - normally only expressed in foetus/embryo but overexpressed in a wide range of carcinomas prostate - prostate specific ag (PSA), prostate specific membrane ag (PSMA), prostatic acid phosphtase (PAP)

Question 29

describe problems with antibodies against melanoma \*

Answer 29

there is poor self tolerance the Ab attack melanocytes = auto-immune skin depigmentation (vitiligo)

Question 30

what are the problems of targeting tumour **associated** Ag \*

Answer 30

auto-immune response against normal tissues immunological tolerance either because of * normal tolerance to auto-ag ie dont have the repertoire to stimulate in the first place * tumour induced tolerance - tumours release factors that downregulate the immune response

Question 31

what are the approaches being used and developed for tumour immunotherapy \*

Answer 31

Ab based therapy - Ab of a single specificity therapeutic vaccination immune checkpoint blockade adoptive transfer of immune cells combinations of the above

Question 32

what does monoclonal mean \*

Answer 32

Ab of a single specificity

Question 33

describe different monoclonal Ab based therapy \*

Answer 33

'naked' - means just the Ab itself - eg herceptin which is anti HER2 for breast cancer, anti CD20 (ie B cells) for lymphoma, anti CD52 (B cells) for lymphoma, and anti EGFR for colon cancer conjugated - Ab that have been conjugated something as a way of targeting the drug or radiochemical to the tumour eg Zevalin - anti CD20 linked to radioactive particle as way of delivering radiation, and kadcylca - HER2 linked to cytotoxic drug - way of delivering drug straight to tumour bi-specific Ab - genetically engineered to combine 2 specificities eg anti CD3 and CD19 - approved for use in pts with B cell tumours problem is this is expensive

Question 34

describe therapeutic cancer vaccination \*

Answer 34

provenge - for advanced prostate cancer uses adoptive transfer of cells patients own WBC are treated with a fusion protein between prostatic acid phosphtase (PAP - tumour associated Ag) and the cytokine GM-CSF this stimulates DC maturation and enhances PAP-specific T cell responses then T cells are put back into pt this is FDA approved and liscenced but not NICE approved

Question 35

describe 'personalised' tumour specific cancer variations \*

Answer 35

different people's cancers have differnt mutations - in theory want a differnt vaccine for each patient take normal cell and tumour cell and do whole exome sequencing (WES - exomes are the coding part) - get teh HLA sequencing compare the 2 sequences to find out what mutations are in normal cell compared to tumour cell use computer programming to determine which peptides from mutant proteins bind to pts HLA molecules use this to create candidate neoantigens and add adjuvant to stimulate the immune response this is a personalised vaccine this is expensive

Question 36

describe immune checkpoint blockade \*

Answer 36

induce/remove negative regulatory controls of existing T cell responses - uses monoclonal Ab to block reactions targets CTLA-4 and PD-1 pathways * CTLA-4 is expressed on actiavted and regulatory T cells, binds to CD80/86 (which are costimulatory molecules on APC) * PD-1 is expressed on activated T cells and binds to PD-L1/2 (complex expression patterns that may be upregulated on tumours) * when they bind to their target - they release inhibitory signals it is effective in melanoma and other types of cancer

Question 37

examples of immune checkpoint blockade drugs \*

Answer 37

ipilimab - anti CTLA-4 nivolumab - anti PD-1 they are antagonistic Ab

Question 38

what is the problem with using immune checkpoint blockade \*

Answer 38

remove the -ve influence on t cells - could lead to autoimmune response

Question 39

benefit of immune checkpoint blockade \*

Answer 39

general - not trying to target a specific Ag

Question 40

describe adoptive transfer of cells \*

Answer 40

need source of T cell, from tumour or blood - they are expanded in vitro by stimulation from cytokines ie IL2 T cells are then put back in body this helps by increasing number of tumour specific T cells this gives us the opportunity to alter lymphocytes and change their specificity

Question 41

describe chimaeric antigen receptors \*

Answer 41

introduce CAR into cell receptor is formed by taking antigen binding part of receptor and it is linked together by single polypeptide chain - called single chain varient fragment (scFv) the scFv is fused onto the normal transmembrane part of TCR the costimulatory part of receptor comes fromCD28 )normally involved in costimulation of T cells) zeta part comes from CD3 polypeptide - this has the tyrosine that can be phosphorylated when CAR binds ag that ab recognises - activates T cells because getting signal form costim part and tyrosine phosphorylation - T cells destroy the tumour cells expressing this antigen the principle is that the specificity of the T cells has been changed this is not readily used - expensive

Question 42

why is it harder to generate an immune response against a tumour than an infection \*

Answer 42

tumours are less inflammatory