L15 - cancer immunology 1

• immunocompetent mice as an experimental approach

  tumour generation - injection of murine tumour cell lines, genetic manipulation to drive efficient tumourigenesis

  immunity - endogenous

  advantages - experimental access - know alot

  disadvantages - faster tumour growth, mice are kept sterile

  potential modification to investigate T-cell function - neo-antigen expression in the tumour cell lines with matching TCR transgenic T cells
• immunodeficient mice as an experimental approach

  tumour generation - injection of human tumour cell lines

  immunity - injection of human immune cells

  advantages - human cells

  disadvantages - limited immunity
• system characterisation of human tumour biopsies as an experimental approach

  tumour generation - endogenous

  immunity - endogenous

  advantages - endogenous human anti-tumour immunity

  disadvantages - limited manipulation - expensive, can't manipulate humans

  
  

  sequences entire genome
• tumour immunity is dynamic
• 3 E model of immune interaction

  Elimination

  Equilibrium

  Escape
• go over the e model and make cards
• tumours need to activate innate immunity

  tumour-induced changes in the tissue need to be - narcotic cell death

  recognised by tissue-resident immune cells, macrophages and dendritic cells

  can also be recognised by danger signals and microbes

  outcome of initial immune response to tissue damage can be repair or chronic inflammation

  environment can lead to infection agent - if tumour stays, initial activation lead to classic tissue response
• cGAS STING pathway as an example of tumours needing to activate innate immunity


  Cytoplasmic dsDNA, e.g. from tumour exosomes, activates cGAS, cyclic GMP-AMP synthase, leading to the generation of cGAMP

  cGAMP activates STING, stimulator of interferon genes, by triggering tetramerization on the Golgi, leading to the generation of type I interferons

  thus activated DCs can translocate to the draining lymph nodes

  Other danger signals are: RNA (TLR3), ATP (inflammasome), extracellular F-actin (DNGR1 on cDC1 cells)
• synthetic STING activation promotes anti-tumour immunity

  Chemical compound library screening generates a STING agonist, MSA-2 2

  MSA-2 dimerization is required for STING binding

  MDA-2 dimerization is pH-dependent and requires the acidic pH of the tumour microenvironment to be efficient

  Oral MSA-2 reduces tumour growth in a mouse model
• sustained DC activation promotes anti-tumour immunity

  1.early stage tumour - Migratory cDC1 cells can effectively prime CD8+ T cells in the draining lympho node

  2. progressive disease - cDC1 function becomes diminished over time - reduced migrated, tumour growth

  3. reduced burden - Restoration of cDC1 function with anti-CD40 and Flt3 can restore CD8+ T cell priming - increased migration, tumour shrinkage
• tumour immunity has to be sustained and generated consistently or it dies out
• macrophages change over time steps 1 and 2

  1.Tissue-resident macrophages (TRM) are activated by danger signals and tumour cell-derived cytokines

  2. Tumours trigger emergency myelopoiesis, leading to monocytes that are recruited to tumours developing into myeloid-derived suppressor cells (MDSC) and tumour-associated macrophages (TAM)
• macrophages change over time steps 3 and 4

  3.Continuous low level macrophage activation in a metabolically competitive environment leads to upregulation of inhibitory receptors, such as PD-1, TIM-3 and the generation of reactive oxygen species (ROS). This drives a switch from the initially immunostimulatory to an immunosuppressive macrophage phenotype

  4. Suppression of T cell function
• tumours harbour bacteria

  bacteria processed by antigen presenting cells and trigger antimaterial T-cell response that does something to antitumour response???
• tumours harbour bacteria

  bacteria processed by antigen presenting cells and trigger antimaterial T-cell response that does something to antitumour response???
• T-cells can recognise various antigens
• the various antigens T-cells can recognise

  TAA - tumour-associated antigen, unmutated genes - may also be expressed in select normal tissues

  CGA - cancer germline antigens, expressed during fetal development, e.g. NY-ESO-1 HERV: endogenous retroviruses (8.5% of gDNA) - not expressed when baby is born

  TDA - tissue differentiation antigens, e.g. MART-1 Overexpressed antigens, e.g. Her2, carcinoembryonic antigen (CEA)

  TSA: tumour-specific antigen, neoantigens
• positives and negatives TAA, CGA, TDA

  + commonly shared
• positives and negatives TSA

  + no prior tolerization

  -ve commonly patient-specific
• tumours generate neoantigens

  melanoma is highly mutagenic
• tumour immune interactions are diverse
• must appreciate how much diversity is in antiimmune tumour response

  end up with sequences from entire transcriptome of the samples - group similar together
• analysis of all samples in The Cancer Genome Atlas - 33 cancers, 11180 samples - RNAseq

  6 different immune types

  different cancers all with different immune response
• method - parallel tissue staining with 40 antibodies, 41 patient triple negative breast cancer samples

  massive diversity from patient to patient
• Tumour CTL are diverse

  method - scRNAseq in combination with TCRseq

  all 400,000 T-cells sequenced and group them - expression characterising and TCR tracing
• tumour T-cells are diverse
• Can group all CD8 T cells into 17 different subtypes, can easily distinguish them from genes produced
• tumour t cells are diverse slides
• exhausted CTL are diverse

  Early/precursor Tex - TCF1+ Variable inhibitory receptor expression Retain some proliferative potential

  Tex with remaining effector function - TOXhi Granzyme, peforin, IFNg Inhibitory receptor high No proliferative potential

  Terminal Tex TOXhi - Inhibitory receptor high No proliferative potential
• Tumour microenvironment (TME)

  Can be immune-rich (hot tumours) or immune-poor (cold tumours)
• Immune-poor tumours

  Trouble as no immune response to activate
• Immune-rich tumours

  • Immune cells can mix with tumour cells or be separated
• Wide variety of immune cells in TME
• Anti-tumour immune effectors and suppressive immune cells commonly co-infiltrate
• Key CTL subtypes

  • Memory
  • Effector memory
  • Exhausted CTL
• Exhausted CTL subtype

  Exhausted cells with residual proliferative potential and terminally exhausted CTL
• The tumour microenvironement (TME) can be immune–rich (hot tumours) or immune-poor (cold tumours)

  In immune-rich tumours immune cells can mix with tumour cells or be separated

  There is a wide variety of immune cells in the TME Anti-tumour immune effectors and suppressive immune cells commonly co-infiltrate

  There are distinct functional subtypes for most immune cell types Key CTL subtypes are memory, effector memory and exhausted CTL

  Even exhausted CTL subtype into exhausted cells with residual proliferative potential and terminally exhausted CTL
• immune therapy aims for:

  • Efficient immune infiltration
  • Efficient mixing of immune cells with tumour cells
  • Favourable balance of effector to regulatory cells
  • Generating CTL with proliferative potential over exhaustion
• key mechanisms of suppression TME

  • immune exclusion
  • metabolic competition
  • suppressive soluble mediators
• suppressive cell types

  • Treg
  • MDSC