Cytotoxic T-lymhocte & NK cells PDF

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Summary

Immunotherapy in Cancer  Learning Target o Innate Cellular Response  NK Cells (Normal Role)  Targeting NKs [Immunotherapy: Didn’t Work] o Adaptive Cellular Response  CD 8 +¿¿ CTLs [Normal Role]  Targeting CTL [Immunotherapy: WORKED]  Effector Mechanisms [Tumour Immunity] o NK cells o CTLs Fun...

Description

Immunotherapy in Cancer  Learning Target o Innate Cellular Response  NK Cells (Normal Role)  Targeting NKs [Immunotherapy: Didn’t Work] o Adaptive Cellular Response + ¿ ¿ CTLs [Normal Role]  CD 8  Targeting CTL[Immunotherapy: WORKED]  Effector Mechanisms [Tumour Immunity] o NK cells o CTLs

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Funfact [Cells involved] o Natural Killer Cells  Ant-tumour Response [Overview]

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Why o Tumour cells:  √ ↑ Metabolic Activity [Cellular Stress]  ⊕ Stress receptors [MICA/MICB]  NK recognize receptors ⇒ Kill target cells Killing cells o Apoptosis  FAS  Granzyme B

o Encase Cellular debris ⇒ Plasma Membrane o Mϕ ⇒ Clear Apoptotic debris o CTLs

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Anti-tumour Response [Overview]  Why o Cell replicating: V. High Rate  V. High turn-over rate [Metabolic Stress/ Viral Budding] √ Necrosis [Burst]   Cross-Presentation o Activated DC ↔ Naïve T1 Helper Cells [CD4] o Activated DC ↔ CTLs [CD8]  How

o Cellular leakage [ √ Inflammatory Response]  Cellular leakage ⇒ Phagocytosed by DC  DC activated ⇒ Become Presenting Cells [Altered-self epitopes]  Activated DC ⇒ Migrate [Site of tumour → Lymph Node]  Activated DC ↔ Naïve T-cell [Naïve T1 helper cells] & CTLs  Activated DC ⊕ Naïve T1 helper cells [Displaying  peptide specific to Tumour Cells]  Display Epitope to CTLs  Activated T1 helper cells  Release IL-2 ⊕ CTLs   Activated CTL exit LN  Migrate to Site of Tumour

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Killing Mechanism o Enzymes  Granzyme B o Process [Granzyme B (CTL/NK Cells/ γδ

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Killing of tumour cells o Apoptosis  Granzyme B [X Fas]

T-cells)

ICAD Cleavage o Directly Cleave ICAD  ICAD → CAD o Activate Caspase 8  Procaspase-8 cleavage  Procaspase-8 → Caspase 8  Caspase 8 ⇒⊕ Caspase 3 [Main Effector Molecule]  Caspase 3: Cleave ICAD o Activate Caspase 3 [Directly]

o CAD  Caspase activated DNAse  Normally bound to ICAD [Cytoplasm retention protein]  Enters Nucleus ⇒ Degrade DNA Immunosurveillance o What  Process/ Monitoring of self-cells o Cells responsible  CTLs  NK o Identifying  Stressed Cells:Presence of Stress Receptors  Mutant Cells: Expressing Non-self-proteins [Altered Self] o NK Cells [Innate Immunosurveillance]  Activation

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How o Activation v.s. Inhibition receptors  Normally o Inhibition receptors >>> Activation receptors [Predominant] o X Killing o Require overcoming [Altered-self]  ↑ Activation Signal [Missing-self]  ↓ Inhibition Receptors Normal condition

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Recognizing self-cells ⇒ MHC I!!! NK cells o √ Inhibitory Receptors [KIR & or CF94/NKG2] – ve Signal  Recognize MHC I √ Activation receptor (AR) + ve Signal o  Recognize AR-ligand [Cells]  Cells √ Both Inhibitory & Activation signal Inhibitory Signal >>> Activation Signal [Immunosurveillance] Missing self-hypothesis (Tumours associated with Virus)

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Virus prevent MHC I from expressing (Removing leading sequence)  Receptors Involved Inhibitory Receptor [NK] Activation Receptor [NK] Ligand [Cells] KIR-Long KIR-Short MHC I NKG2A NKG2C HLA-E [Displaying Leader Sequences: HLA-A-C] X Present Epitope to T-cells Receptor

Originally: o Cytotoxic T-lymphocytes ( ∵ MHC Restricted) ∴ X recognize that cells & Kill it  ∴ No longer functional   Overcoming CTL/T-cells Evasion o CD94/NFK2A / KIR ⇒ X Bind to MHC I o Remove inhibitory signal o Minor excitatory signal √ ⊕ Signalled for destruction Altered self-hypothesis (Tumor Cells & Viral infected cells)  Normally o Inhibitory Signal > Activation Signal  Tumour Cells / Other Viral Infected Cells o Stress Cells  All cells √ Intrinsic Biological Clock [Basic Metabolic Rate]  ∵↑ MAPK  ↑ Cells driven to Cell cycle  Overexpress Regulatory Checkpoint Proteins  Using Too much ATP  ∆ Cell metabolic rate [ ∆ Biological Clock]  Stress cells ⇒ Express Stress Receptor o Example  Stressed ⇒↑ ↑↑ Stress receptors (e.g. MIC A & MIC B)  ↑ Expression of developmentally downregulated proteins  Self-proteins modification (Mutations) o Concept  ↑↑ ↑ Activation signal (Altered self-signal)  Activation Signal > Inhibitory Signal [Overcome]  ⊕ Cell-death  Receptors Involved 

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Inhibitory Receptor [NK] -

Activation Receptor [NK] NKG2D

NKG2A

NKG2C

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Ligand [Cells] MIC-A & MIC-B [Stress Receptor] HLA-E [Displaying Leader Sequences: HLA-A-C] X Present Epitope to T-cells Receptor

Overcoming NK Cells killing  Why o Altered self: Insufficient to mediate NK Response  Inhibition signal remain present  Stress signal: X Overcoming Inhibition Signal o Removal of Activation Receptor [NKG2D]

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Removal of Activation Receptor [Main Evasion Strategies: Oncoviruses]

o Tumour cells ↑ MIC-A & B expression o NKD2D [NK-cells, γδ T-cells] bind MIC-A & B ⇒ Kill Tumour Cells o Some Tumour cells ⇒ Cleaves MIC from cell surface [NO LONGER ASSOCIATED WITH TUMOUR CELLS] o Soluble MIC: Binds Free NKG2D [Decoy MIC-A & MIC-B] o ∴ X Effectively Kill Tumour Cells  Off-Target Effects: Kill Neighbour Cells [X Specific to Tumour Cells] Immunotherapy [Checkpoint Inhibitors]  Concept o Blocking Inhibitory Receptors: Makes Activation easier  How

o KIR-Long Specific Antibodies  Block Main MHC I Inhibition Signal

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Clinical Evidence

o Multiple Myeloma Patient  Anti-KIR Antibody added [Left Diagram]  Line: Normal Degranulation Level  Drop in Relative Degranulation [Degranulation: Releasing of Granzyme B]  ∴ Drop in NK cells killing Tumour cells o Killing NK Cells o Anergic NK Cells  Removing Anti-KIT Antibody Levels [Right Diagram]  Re-boost of Granzyme B  Re-activate NK Cells  Experiment Fucked Up~~~~ o CTLs  Activation  How o Cross-presentation  Cross-Presentation [人妖: Both CD4 & CD8] o APC (DC) ↔ Naïve T1 Helper cells [CD4] [CD8] o APC (DC) ↔ CTLs  Process  APC Display Tumour Specific Epitope o TH1 cells o CTL  Both presentation present o TH1 ⇒ Releases IL-2 o Activates CTLs  CTL enters peripheral  Overcoming CTL killing  Overview o VEGF induced deactivation of APC o ↓ Regulate MHC I [Viral Assoiciated Tumours] [TReh: IL-10 mediated o TGF- β CTLA-4] o PD-L mediated inhibition  VEGF [Tumour Released] o ⊖ APC Activation [Mainly DC] o ⊖ CTL Activation  Subtle Mutations [Non-Viral Associated Tumours]

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o Minor changes to a.a. [Tumour Cells] ⇒ X Change Overall Epitope o T-cells [Gone Through Central Tolerance] ⇒ X recognition of tumour MHC I Deficient tumour cells [Viral Associated Tumours] o Oncogenic Virus ⇒ Knock out MHC I/ X Display MHC Leader sequences o X TH1 recognition of Tumour o Even √ CTL activation o X Recognize Tumour Cells [X know which cells to target] Inhibitory Signals [TGF- β ]

o Tumour Secrete TGF- β o Binds T-helper cells → Regulatory Cells[Natural/ Induced TReg] o Natural TReg  Bind Effector T-cells [T-cells that are activated]  Deactivate activated T-cells [ ⊖ IP3 ⇒ X 2+¿ ] Ca¿ o Induced TReg  Release IL-10

 ⊕ CTLA4  Contraction of Cytokines  Contraction of Immune Response  Prevent activation of new T-cells o IL-10 Driven CTLA-4

IL-10 ↑ CTLA-4 Expression [In CTL] CTLA-4: Higher affinity to B7 [Compared to CD28] Inhibitory Signals [Main Evasion Strategy: Tumours]  

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o Activated T-cell: o Cancer cells:

√ ↑

PD-1 PD-L1 & PD-L2 ligand

∴ PD-1 ↔ PD-L1/PD-L2 ⇒ Blocks T-cells Signalling [CTL] o Even √ T-cell signalling: Tumour √ Block it Immunotherapy  Types o Anti-CTLA4 mAbs [Ipilimumab] o Anti-PD-1 mAbs [Nivolumab]  Anti-CTLA4 o Concept [Prevent Activation w/ B7] o

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o Experiment  Late Metastatic Melanoma [Late-Stage Skin Cancer]  Poor Prognosis [survival Rate: ~20%]  Late-Stage Cancers o Survival Data-Analysis

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√ Drug Treatment: Extend Several Months’ living [5-6 months → ~10 months]

Anti-PD1 o Concept

 Prevent Inactivation of T-cell Signalling  √ Reactivate CTL & Kill Tumour Cells o Tumour Burden

Majority  ↓ Tumour Burden [~20%]  X Really Significant  Minority  Tumours √ Progress [X Do well, Tumour Progress] Combined Therapy [Anti-PD-1 & Anti-CTLA4] o Concept:  Both Therapy at the same time  Prevent CTLA-4 & PD-1 o Tumour Burden 

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3/40 patients: Progressed 2/40 Patients: Slight decrease in Tumour Burden

Remainder: Up to 80% Reduction [Up to 10 weeks] Late-stage Tumour: Almost Gone  Poor prognosis  High Tumour Burden  Metastasis Combine Therapy  Stop Progression  Remove Tumour Clinical Complication  Auto-immune disease [Long Term Complication] Overall Survival [Survival Analysis up to 4 years] 

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Untreated  3-year survival rate:...