Immunotherapy and cancer II Flashcards
what are some cell based therapies for cancer?
- LAK; lymphokine activated killer
-NK-T CELLS - yd T cells
- DC
- TIL: tumor infiltrating lymphocyte
- CAR: chimeric antigen receptors
LAK cells features
- 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
natural killer cells
- 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
LAK cells and cancer
- 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
what was the Rosenberg Trial of 1993?
- 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
NK-T cells
- 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
NK-T recognition
- MHC independent
- NKT cell TCR recognises the MHC-I like molecule , CD1d
CD1d
-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
NKT immunotherapy
- 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
role of NKT
- 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
the yd T cell features; structural
- 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
yd Tcell; association with cancer
- 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
what is zometa (zoledronic acid)?
- 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
yd T cell therapy
- 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.
what is therapeutic vaccination?
- to induce long lasting reponse against tumor
- stimulate adaptive arm of the immune response
- use professional APC such as DCs
explain priniciple of DC vaccination
- 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
what is antigen loading?
- 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
targetting DC in vivo
- 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
endogenous vaccination
- immunogenic chemotherapy
- radiotherapy
- anti-tumor antibodies
- T cell immune checkpoint blockade
Ex vivo generated cytokine-driven DCs
ex vivo instruction to generate and maintain cytotoxic effector and helper T cells
reprogramming inflammation
- targetting DCs with TLR ligands
- cytokine blockade
targeting antigens to DC subsets in vivo
DC antibody linked to pathogen and/or cancer specific antigens and DC activators
why is manipulaiton of TILs important?
presence of lymphocytes has prognostic significance
why does the presence of lymphocytes have prognostic significance?
- 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
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
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)
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
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
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
what is high affinity TCR
ability of T-cells to detect antigens at low densities
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
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
what are CARs?
chimeric antigen receptors
- similar in nature to TCR transgenics but not MHC restricted
what are CARs composed of?
- antibody recognition domains
- cytoplasmic tail with multiple signalling domains that activate T cells
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
lymphodepletion
a treatment to reduce the population of circulating lymphocytes, prior to infusion of TCR-T cells
how is lymphodepletion achieved?
drugs such as Fludarabine and cyclophosphamide.
- TRI; total body irradiation
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
what is the best phenotype for a T cell in ACT?
- CD4 or CD8
- naive
