Tumor immunology Flashcards
What is cancer immunoserveillance
The immune system recognises and destroys nascent transformed cells
What is cancer immunoediting?
As tumours are genetically unstable, the immune system can kill and also induce changes in the tumour resulting in tumour escape and recurrence
What are tumour specific antigens
Antigens found only on tumours as a result of point mutations or gene rearrangement. Derive from viral antigens
What are tumour associated antigens
Found on both normal and tumour cells, but are overexpressed by cancerous cells. Tend to be developmental antigens that become derepressed. The differentiation of antigens is tissue specific and could result from an altered modification of a protein
What evidence is there for tumour immunology
Infiltration of tumours by lymphocytes and macrophages in melanomas and breast cancers.
Higher chance of cancer after immunosuppression i.e AIDS, ageing…
What are 5 examples of immune system escape by tumours
Low immunogenicity - No MHC ligand/ surface antigen (Breast cancer)
Tumour treated as self - Tumour antigens taken up and presented by APCs but dont stimulate T cells.
Antigen modulation - Antibody against a tumour cell - The cell surface antigen is endocytosed and degraded, immune selection for the antigen is lost
Tumour induced immune suppression - Factors secreted by tumour cells inhibit T cells directly
Tumour induced privileged site - Factors secreted by tumour cells create a physical barrier to the immune system i.e the BBB
What is active immunotherapy
typically vaccination (cervical cancer) Purpose is to augment host immune system to tumours with cytokines and costimulators
What are types of cancer vaccine
Purified tumour antigens injected as a peptide vaccine - problem is that the peptides are unlikely to be tumour specific
What is passive immunotherapy
Adoptive T cell therapy/ anti-tumour antibodies
What are three types of cell based therapies
Can be used to activate a patients immune system to attack cancer
Used to target therapeutic genes to attack the tumour (loaded with a gene/virus)
Dont directly act on cancer cells, instead work to activate the hosts immune system
What are dendritic cells and where are they found
Found throughout the body - detect foreign material and present the antigen on their surface to lymphoid originated cells (T cells NK cells)
Describe a dendritic cell vaccine
Take blood from the patient. Isolate monocytes and differentiate them into DC. Pulse the DC with the toxic payload (tumour antigen) and return them to the body. Circulate to lymphoid organ and present to CD4/CD8 T cells.
How is the trojan horse treatment performed
Take blood from the patient and isolate the monocytes
These will differentiate into macrophages and are associated with a toxic payload (in this case a virus) and are put back into circulation. It’s known that they translocate deep into tumours and release the toxic payload.
Why are areas of hypoxia targeted
Tumour hypoxia associated with poorer prognosis:
Hypoxic conditions stimulate new vessel growth, suppress cytotoxic T cells and are resistant to radio/chemotherapies (this will lead to relapse of the tumour)
Would the macrophage therapy be a frontline treatment?
No, used following chemo/radiation therapy - After these macrophages are found in the hypoxic tumour site that remains so can kill off any surviving cells
