Immunotherapy and cancer II Flashcards
1
Q
What are LAK cells?
A
- lymphokine activates killers
- PBMC taken from patients and cultures with IL-2 in vitro
- heterogenous population produced
- NK, NKT and T cells
- higher than normal anti-tumour activity
- can target NK resistant tumour cells
2
Q
Describe NK cells
A
- recognise lack of MHC I
- majority are CD3-CD56+
- subsets = CD56 bright, CD56 dim, CD16+/CD16-
- primarily found in blood, BM, spleen and liver
- main cell type in LAK population
3
Q
Describe LAK cells
A
- relatively easy to produce in large numbers
- simple activation of a cells subset
- limited specificity
- localise to tumour sites
- may need additional IL-2 to maintain activation
- toxicity - capillary leak syndrome
4
Q
Describe the first trial with LAK cells
A
- Rosenberg trial 1993
- used LAK cells and IL-2
- 181 patients with advanced metastatic cancer
- 10 complete responses in the LAK-1L-2 group compared with 4 in the IL-2 alone group
- overall trend was towards inc survival with LAK
- many toxic effects due to vascular permeability
5
Q
Describe NK-T cells
A
- subpopulation of T cells - found in thymus, liver and BM
- expres biased T cell receptor repertoire
- some inhibitory and activation receptors shared with NK cells
- can kill tumour target cells in vitro - mainly through TCR and CD16
- most important is their ability to produce cytokines to direct the immune response eg. IFN-gamma and IL-4
- also express perforin and surface molecules - FasL
6
Q
Describe NK-T cell recognition
A
- NKT cells are mHC independent
- NKT cell TCR recognises the MHC-1 like molecule = CD1d =
- relatively nonpolymorphic
- restricted dist. on cells of the hematopoietic lineage
- present glycolipid
- synthetic alphaGalCer used to study NKT cells
- unknown whether tumours express glycolipid ligands that stimulate NKT cell activity
7
Q
Describe NKT immunotherapy
A
- alpha-galactosyl ceramide
- used for in vitro expanded NKT based vaccines
- used alpha-gal cer pulsed DCs
- well tolerated
- induce expansions of NKTs in vivo
8
Q
What is the role of NK-T?
A
- MOA unknown - may be linked to interferon gamma
9
Q
What are gamma-delta T cells?
A
- TCR structurally similar to alpha beta
- may not need normal antigen presentation mechanisms
- may not recognise peptides and therefore no need for protein processing
- may detect stress or small organic molecules which signify infection
- can respond to MICA and MICB expressed on stressed cells
- thought to be ‘primitive’ t cells in mucosa
- can directly target a range of tumour cells = TIL
- suggested to target cancer stem cells
- can directly target bacteria
- thought to recognise endogenous pyrophosphonates
10
Q
What is zometa?
A
- amino bis-phosphate used in osteoporosis
- blocks mevalonic acid pathway
- allows build up of IPP (susceptible for killing)
- has been used in prostate and breast cancer
- look at effectors cells
- reduced gamma-delta T cells in peripheral blood of patients receiving treatment
11
Q
Describe gamma-delta T cell therapy
A
- ex vivo activation trialled in RCC in combination with low dose of iL-2 = stable disease
- in vivo activation, use of zometa or other lymphostimulatory regimes - breast and prostate cancer
12
Q
What is a therapeutic vaccination?
A
- idea is to induce long lasting response against tumour
- stimulated the adaptive arm of the immune response
- use professional APC such as dendritic cells
13
Q
Describe the principle of DC vaccination
A
- take monocyte from patient
- monocytes can be used to generate immature DCs - using il-4
- also isolate tumour cells from patient and lyse them
- combine lysed tumour cells with immature DCs = DCs take up tumour then give a maturation signal = stops them being endocytic cell turns them into antigen presenting cell
- APC DC which are loaded with tumour material
- injected back into patient as vaccine
14
Q
Describe antigen loading
A
- defined tumour antigens - peptides = at least 4 diff peptide targets needed
- undefined tumour antigens = DC tumour cell hybrids, tumour cell lysates, necrotic/apoptotic tumour cells
15
Q
Describe DC maturation
A
- used to be non-matured
- TNFs
- complex cytokine cocktails including TLR agonists :
poly I: C used clinically, aldara, R848
16
Q
Describe the clinical results with ex-vivo DCs
A
- sipuleucel-T first FDA approved DC treatment for metastatic prostate cancer
- PBMC treated with GM-CFS prostatic acid phosphastase
- phase III trial showed 4 month extension of survival
17
Q
How will ‘virtual virally infected’ tumour cells work?
A
- took a tumour cell and cultured it with dsRNA (ligand for TLR3,7,8 , PKR, RIG-1) -infection monitoring pathways
- causes the death by apoptosis of tumour cells
- tumour cell blebs off parts of its material = apoptotic blebs with danger signals with activate the immune response
- danger signals mature DC which are recruited to site
- DC take up apoptotic blebs and process tumour = helper T cells activated and kill other tumour cells
18
Q
Why are TILs important?
A
- tumour infiltrating lymphocytes
- presence of lymphocytes has prognostic significance
- large numbers of TILs in many tumours
- high number of CD8+ cells also has prognostic significance
- high CD8+/Treg ratio
19
Q
Describe adoptive cell therapy with TILs
A
- assumes that TILs have knowledge of tumour antigens
- method =
- tumour biopsy
- in vitro polyclonal stimulation (IL-2 and anti-CD3 ab)
- lymphodepletion of patient
- stimulated T cells reintroduced into the patient
20
Q
What are the results with adoptive cells therapy with TILs?
A
- cytotoxicity against tumour cells in culture
- homing of transferred T cells to tumour in vivo
- best results are pre-treated with peripheral lymphodepletion regimen of total body irradiation
21
Q
What are the disadvantages of TIL therapy?
A
- no enough tumour to generate sufficient CTLs
- TILs may be refectory to stimulation
- time consuming and labour intensive = requires infrastructure
- culture time may be too long
- culture time may influence quality of T cells
- high failure rate of culture
22
Q
Describe adoptive cell therapy (ACT) using peripheral blood derived T cells
A
- clonal expansion against a known antigen
- advatage of east availabiity of large numbers of T cells
- peripheral blood contains many precursors with TAA reactivity
method = - isolate peripheral blood PBMC
- stimulated in vitro with autologous DC and antigen
- grow out tumour reactive clones/polyclonal pool
- used extensively for treatment of post-transplant
23
Q
Describe high affinity TCR transduction
A
- TCR reactive to TAAs
- alpha and beta chains of TCR are engineered into retroviral vector
- patients CD8+ t cells from peripheral blood are removed and transduced with TCR-virus
- adoptive transfer back into patients
PROBLEMS - initial results 2/15 patients with clinical response
- T cells remain in peripheral blood for up to one year
- epitopes need to be characterised and matched to HLA
- must be present in tumour
- patient specific therapy
24
Q
What are CARs?
A
- chimeric antigen receptors
- similar in nature to TCR transgenics, not MHC restricted
COMPOSED OF: - antibody recognition domains
- cytoplasmic tail with multiple signalling domains that activate T cells
- advantages of specificity and high affinity
- not yet extensively studied
25
Q
Describe peripheral/non-myeloblative lymphodelpletion
A
- there is no relationship between the degree of lymphodepletion and clinical outcome
- achieved with drugs such as fludoarabine and cyclophosphamide
- removes T cells that compete for homeostatic cytokines (IL-7, IL-15)
= inc proliferation and acquisition of effector functions for infused cells - inc expression of serum IL-7 and IL-15
- MAY enhance APC function
- reduces number of circulating regulatory cells
26
Q
What is the best T cell for ACT?
A
- CD4 or CD8
- TCM (central memory, CD62L+)
- TEM
- still unknown
