Immunotherapy and cancer II Flashcards
(39 cards)
1
Q
what are some cell based therapies for cancer?
A
- LAK; lymphokine activated killer
-NK-T CELLS - yd T cells
- DC
- TIL: tumor infiltrating lymphocyte
- CAR: chimeric antigen receptors
2
Q
LAK cells features
A
- PBMC taken from patients and cultures with IL2 invitro
- Heterogenous population
- NK, NKT & Tcells (CD25+)
- predominantly NK cells
- higher than normal anti-tumor activity
- can target NK resistant tumor cells
3
Q
natural killer cells
A
- recognise lack of MHC1
- about 5-10% of human peripheral blood lymphocytes
- majority are CD3- CD56+
- primarily found in blood, BM, spleen and liver
- main cell type in LAK population
4
Q
LAK cells and cancer
A
- relatively easy to produce in large numbers
- simple activation of a cell subset
- limited specificity
- localise to tumor sites
- many need additional IL2 to maintain activation
- toxicity, capillary leak syndrome
5
Q
what was the Rosenberg Trial of 1993?
A
- used LAK cells and IL2
- 181 patients with advanced (metastatic) cancer (97 renal and 54 melanoma)
- 10 complete responses in LAK+IL-2 group compared with 4 in the IL2 alone group
- overall result was a trend towards increased survival with LAK
- many toxic effects due to vascular permeability
6
Q
NK-T cells
A
- subpopulation of T cells
- found in thymus, liver and BM, few found in spleen or lymph nodes
- some inhibitory and activation receptors shared with NK cells
- can kill tumor target cells in vitro; mainly through TCR and CD16
- ability to produce cytokines to direct immune response
7
Q
NK-T recognition
A
- MHC independent
- NKT cell TCR recognises the MHC-I like molecule , CD1d
8
Q
CD1d
A
-relatively nonpolymorphic
- restricted distribution on cells of the haematopoietic lineage
- present glycolipids
- synthetic a-GalCer used to study NKT cells
- unknown whether tumors express glycolipid ligands that stimulate NKT cell activity
9
Q
NKT immunotherapy
A
- a-galactosyl ceramide
- used for invitro expanded NKT based vaccines
- used a-galcer pulsed DCs
- well tolerated
- induce expansions of NKTs in vivo
- some stable disease in a variety of cancers
10
Q
role of NKT
A
- MOA; unknown but may be linked to yIFN production
- study in lung cancer = treatment with a-GalCer loaded DCs = increase NKT TILs
- resected tumor 1 week after APC injection
- showed increased y-IFN in response to a-GalCer exvivo
11
Q
the yd T cell features; structural
A
- TCR structurally similar to ab
- may not need normal AP mechanism
- 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
- can recognise small organic molecules secreted by bacteria
11
Q
yd Tcell; association with cancer
A
- primitive T cell in the mucosa
- can directly target a range of tumor cells but also been identified in TIL
- suggested to target cancer stem cells
- can directly target bacteria
- thought to recognise endogenous pyrophophonates
12
Q
what is zometa (zoledronic acid)?
A
- amino bisphosphate used in osteoporosis
- blocks mevalonic acid pathway (HMG-CoA to cholestrol)
- allows build up of isopentenyl pyrophosphate
- zometa has been used in prostate and breast cancer
- look at effector cells
- reduced yd T cells in PB of patient receiving treatment
13
Q
yd T cell therapy
A
- ex vivo activation trialled in RCC in combination with low dose IL2 =stable disease
- also trialled in NSCLC
- in vivo activation use of zometa or lymphostimulatory regimes.
14
Q
what is therapeutic vaccination?
A
- to induce long lasting reponse against tumor
- stimulate adaptive arm of the immune response
- use professional APC such as DCs
15
Q
explain priniciple of DC vaccination
A
- vaccination of patient with mature APC DCs
- isolation of monocytes from peripheral blood
- generation of immature DCs
- loading of DCs with whole cell tumor-lysate
process repeats
16
Q
what is antigen loading?
A
- defined tumor antigens; at least 4 different peptide targets needed
- undefined tumor antigens; DC-tumor cell hybrids, tumor cell lysates, nectrotic/apoptotic tumor cells, tumor RNA
17
Q
targetting DC in vivo
A
- use chimeric proteins to deliver antigens to DC specific molecules
- Ag linked to CD205. MHC1 and MHC2 presentation
- need to understand consequences of ligating these surface molecules
18
Q
endogenous vaccination
A
- immunogenic chemotherapy
- radiotherapy
- anti-tumor antibodies
- T cell immune checkpoint blockade
19
Q
Ex vivo generated cytokine-driven DCs
A
ex vivo instruction to generate and maintain cytotoxic effector and helper T cells
20
Q
reprogramming inflammation
A
- targetting DCs with TLR ligands
- cytokine blockade
21
Q
targeting antigens to DC subsets in vivo
A
DC antibody linked to pathogen and/or cancer specific antigens and DC activators
22
Q
why is manipulaiton of TILs important?
A
presence of lymphocytes has prognostic significance
23
Q
why does the presence of lymphocytes have prognostic significance?
A
- large numbers of TILs in many tumors
- high number of CD8+ cells has prognostic significance
- high CD8+/Treg ratio
- pre exisiting antigen specificity of TILs has been correlated with outcome in immunotherapy of melanoma
24
methods of adaptive cellular therapy with TILs
assumes that TILS already have knowledge of transferred T-cells:
- tumor biopsy
- in vitro polyclonal stimulation (IL2 and anti CD3 antibody)
- lymphodepletion of patient (enhances persistence of transferred T cells)
- stimulated T cells reintroduced into the patient
25
results of adaptive cellular therapy with TILs
- cytotoxcitiy against tumor cells in culture
- homing of transferred T cells to tumor in vivo
- >50% objective response rate
- best results when patients are pre-treated with peripheral lymphodepletion regimen of total body irradiation (improved survival benefit)
25
disadvantages of adaptive cellular therapy (ACT) with TILs
- need enough tumor to generate sufficient CTLs
- TILs may be refractory to stimulation
- time consuming and labor intensive; requires infrastructure
- culture time may be too long
- culture time MAY influence quality of T cells
- high failure rate of culture
26
ACT using peripheral blood derived T cells
results in clonal expansion against a known antigen
- advantage of easy availibility of large numbers of T cells
- peripheral blood contains many precursors with TAA reactivity
27
method of ACT using peripheral blood derived T cells
- isolte peripheral blood
- stimulate in vitro with autologous DC + antigen
- grow out tumor reactive clones/ polyclonal pool
- used extensively for treatment of post-transplant lymphoprolifrative diseases
- used in haematological malignancies; some success
- cloning and culture take time
28
what is high affinity TCR
ability of T-cells to detect antigens at low densities
29
high affinity TCR reduction
- TCRs reactive to TAAs characterised and cloned
- a and b chains to 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
30
problems with high affinity TCR reduction
- initial results 2/15 patients with clinical response
- T cells remain in peripheral blood for up to 1 yr
- epitopes need to be characterised and matched to HLA
- must be present in tumor
- becomes patient specific therapy
31
what are CARs?
chimeric antigen receptors
- similar in nature to TCR transgenics but not MHC restricted
31
what are CARs composed of?
- antibody recognition domains
- cytoplasmic tail with multiple signalling domains that activate T cells
32
disastrous case study using CARs
- patient with colon carcinoma
- CAR against Erb-B2
- patient developed acute autoimmune response
- possible due to low levels of antigen on lung epithelium
33
lymphodepletion
a treatment to reduce the population of circulating lymphocytes, prior to infusion of TCR-T cells
34
how is lymphodepletion achieved?
drugs such as Fludarabine and cyclophosphamide.
- TRI; total body irradiation
35
what does lymphodepletion do?
removes T cells that compete for homeostatic cytokines and =
- increased prolif. & acquisition of effector functions for infused cells
- increased expression of serum IL7 and IL15
- may enhance APC function
- reduces number of circulatory regulatory cells
36
what is the best phenotype for a T cell in ACT?
- CD4 or CD8
- naive
