Immunity to Cancer / Cancer Checkpoints Flashcards
1
Q
What are the characteristics of a benign vs malignant tumours
A
- Benign: Localised, non-invasive, resemble tissue of origin, encapsulated, intact surface, exophytic growth, incapable of indefinite growth
- Malignant: Invade, rapid growth, aneuploidy, ulcerated, endophytic growth, vascular permeation, metastasis to invade other tissues
2
Q
What is malignant transformation
A
- DNA alterations that caused cells to acquire properties of cancer
- Small benign tumours, adenomas grow / disorganise acquiring malignant phenotype
- Inactivation or loss of 3 tumour suppressor genes
- Activation of one cellular proliferation oncogene
- Induced by physical / chemical substances, ionising radiation and infectious agents
3
Q
What is a proto-oncogene
A
- Encode proteins that normally control cell proliferation
- Activate normal cell proliferation
4
Q
What is an oncogene
A
- Mutated proto-oncogene
- Jammed accelerator, gain of function
- Uncontrolled proliferation
- Alterations through actions of transforming viruses, exposure to carcinogens or genetic predispositions
5
Q
What are tumour suppressor genes
A
- Genes that normally prevent cell proliferation that are mutated
- Defective breaks, loss of function (recessive)
- Uncontrolled proliferation
- TP53: Encodes nuclear phosphoprotein involved in growth arrest, apoptosis and DNA repair
- Rb Gene: Hereditary, one copy is mutated and second is somatically inactivated
6
Q
What are apoptotic genes
A
- Genes associated with cancer control, proliferation
- Pro-apoptotic (tumour suppressor)
- Anti apoptotic (oncogenes)
- Dysregulation leads to failure of former / overactivity of latter, both encourage neoplastic transformation
7
Q
What is a neoplasm / neoplastic cells
A
- Abnormal mass of tissue, growth excess / is uncoordinated with that of normal tissues
- New growths of cells in the body that express unique / inappropriately expressed Ag
- Altered self gene, over expressed genes, TAAs / TSAs
8
Q
What are TAAs vs TSAs
A
- TAAs: Normal cellular proteins expressed at particular times of development, unregulated in tumour cells
- TSAs: Unique to cancer, mutations in tumour cells that generate altered proteins and thus new Ag
9
Q
What is tumour immunity
A
- Tumour cells can evade immune activation and recognition
- Up-regulation of anti-apoptotic mediators
- Expression of mutated / absent death receptors
- Poor co-stimulatory or down regulation of secondary signal molecules
- Lack of T cell activation
10
Q
What is immuno-editing
A
- Dynamic process that consists of immuno-surveillance and tumour progression
- Consists of elimination (immuno-surveillance), equilibrium (persistence) and escape (cancer progression)
11
Q
What cells are involved in the anti-tumour response
A
- NK cells (target neoplastic cells)
- Adaptive immune cells (CD4 / CD8 / NK T cells)
- Cytokines (IFN-y, IL-12, TNF-a)
12
Q
What is involved in subverting the anti-tumour response
A
- Chronic inflammation (increases stress signals, increased mutation, GF)
- Anti-tumour antibodies (bind NK / macrophages, impair activities)
- Active immunosuppression (soluble factors suppress Tregs / MDSCs)
Reduced MHC expression (poor CTL targets, TAP, IFN-y mutations, insensitivity, decreased activation)
13
Q
What is cancer immunotherapy
A
- Treatment for cancer that involves cytokines that elicit / amplify or suppress immune response
- Attempt to slow the growth of cancer cells
14
Q
What substances are useful in immunotherapy
A
- Used singly or in combinations
- Cytokines (stimulate production of anti-tumour cells)
- Autologous DCs (expanded and reintroduced, prime tumour specific T cells)
- Tumour specific T cells (obtained from tumours, expanded and reintroduced)
- Vaccines (enhance anti-tumour response, tumour Ag stimulating CTL response)
- Monoclonal Ab (attached to therapeutic drug to deliver treatment directly to cancer)
15
Q
What are the three factors that characterise the adaptive immune response to an antigen / tumour
A
- Antigenicity: Ags promote anti-tumour immunity T cells, recognise TAAs, present to MHC
- Adjuvanticity: Presence of non-self antigens is accompanied by danger signals, promote DC / T cell activation
- Feedback: Homeostasis curbs immune response to remove effector cells and limit damage to healthy tissues
16
Q
What are the mechanisms of immune evasion that can be used by tumour cell to subvert immune response
A
- Loss of tumour recognition (decreased MHC / genetic loss of b2-microglobulin, prevent presentation of TAAs)
- Corrupted PRR signalling (inhibition of PRR, suppresses activation of T cells / macrophages / DCs)
- Feedback mechanisms (designed to protect, can be overridden, chronic inflammation, immunosuppressive effects)
17
Q
What is immune suppression
A
- Immune unresponsiveness to tumour
- Inhibitory cytokines, down regulation of MHC / Treg
- Generation of antigen-loss variants
- Loss of CTL function through clonal exhaustion
- Inhibition of T cell activity
18
Q
What are checkpoint inhibitors / checkpoint inhibitor therapy
A
- Antibodies that interfere with the function of proteins on the surface of T cells (abrogate CTL responsiveness)
- By blocking these pathways, checkpoint inhibitors reactivate host T cell response
- Anti-CTLA-4 or PD-1L can block the suppressive effect of tumours and allow reactivation of tumour specific CD8 CTLs
19
Q
What are exhausted T cells
A
- Tumour microenvironment
- Reduced proliferative and functional capacity
- Reduced cytokine / cytolytic activity
- Increased TCIR leading to PD1/PDL1 blockade (normally prevents tumour cells from attacking normal cells)
20
Q
What are CAR T cells
A
- Chimaeric antigen receptor cells
- Fusion proteins, derived from extracellular Ab and intracellular signalling molecule
- Target surface structures
- MHC independent recognition of tumour targets
- Serial killers of tumour cells
21
Q
What are TCR T cells
A
- Cells transduced with a rearranged TCR that can combine CD3
- Specific tumour pMHC complex
- Requires MHC expression, lifelong persistence
- Serial killers of tumour cells
