Tumor immunology (Daemen)

21 important questions on Tumor immunology (Daemen)

What is the difference between benign and malignant tumors?

In benign tumors the tumor cells do not penetrate surrounding tissue (goedaardig)

In malignant tumors the tumor cells do penetrate surrounding tissue (kwaadaardig)

Name five different types of cancers and their origin.

Carcinoma: cancer derived from epithelial cells. Most common cancers: breast, prostate, lung, pancreas, colon

Sarcoma: derived from connective tissue. Bone, cartilage, fat nerve 

Lymphoma and leukemia: from hematopoietic cells

Blastoma: from immature precursor cells or embryonic tissues, more common in children

Germ cell tumor: from pluripotent cells in testicle or ovary.

How does cancer develop?

Through mutations, either hereditary (for example BRSA I & II breastcancer) or acquired mutations through physical and chemical factors.

Through micro-organisms such as bacteria, viruses and parasites.
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What percentage of cancers worldwide does infection plays a role?

20%

Which cells play a role in the adaptive immune response against tumors?

CD8+ cytotoxic T cells
CD4+ T helper cells (produce cytokines to stimulate CTL)

Also: antibodies

What is the mechanism behind NK cells to be activated or not against a tumor cell? (innate immunity)

NK cells kill tumor cells that have low MHC class I expression.

ligand binds activating receptor (NK) V
MHC I binds inhibitory receptor (NK) V,
result: NK does not kill

ligand binds activating receptor (NK) V
no MHC I to bind inhibitory receptor (NK) X
result: NK kills

How do macrophages respond to tumor cells? (innate immunity)

By release of cytokines like TNF-alpha (tumor necrosis factor), ROS, NO or phagocytosis

What kind of different types (4) of tumor antigens do tumor cells express?

- Mutated cell protein
- Oncogene or mutated tumor suppressor gene
- Overexpressed or deflective expressed self protein
- Oncogenic viruses

How do T cells get activated and trafficked as a result of cancer antigens?

1) Release of cancer cell antigens (cancer cell death)

2) Cancer antigens presentation by dendritic cells/APC)

3) Priming and activation of T cells in lymph node

4) Trafficking of T cells to tumor (CTLs) through blood vessels

5) Infiltration of T cells into tumors

6) Recognition of cancer cells by T cells

7) Killing of cancer cells

For anti-tumor immunity, CTL requires cross-priming to become tumor-specific. What is this and what receptor and cytokines does this need?

Although CTL effectors can act alone when killing target cells, their differentiation from naive CD8-positive T cells is often dependent on 'help' from CD4-positive helper T (TH) cells.

The CD4+ T cell binds to the CD40 receptor on the APC which stimulates the CD4+ cell to express IL-2 which causes differentiation of tumor-specific CTLs.

What is perforin/granzyme-mediated cell killing by CTLs?

1) The CTL binds to the target cell.

2) Granzymes (perforin and serglycin) enter the target cell cytosol and activate caspases.

3) Apoptosis of target cells.

What is Fas/FasL-mediated cell killing by CTLs?

FasL on CTL interacts with Fas on target cell, which results in apoptosis of the target cell.

Often the immune system fails and tumors can progress. Multiple co-stimulatory and inhibitory interactions regulate T cell responses.

Name 2 important inhibitory interactions and their compounds that take place in the lymph nodes.

PDL1 of PDL2 (APC) - PD1 (TC)
CD80 or CD86 (APC) - CTLA4 (TC)

What is CTLA4 and what does it have to do with cancer development?

CTLA4 is a protein receptor that functions as an immune checkpoint and downregulates immune responses. It acts as an "off" switch when bound to CD80 or CD86 on the surface of antigen-presenting cells.

CTLA4 is expressed in regulatory T cells but only upregulated in conventional T cells after activation – a phenomenon which is particularly notable in cancers.

Tumor cells can evade immunization. For example by cancer cells growing faster than they're being killed. Name 4 other mechanisms.

1) decreased MHC expression prevents CTL recognition

2) NK cells have a limited capacity for clonal expansion

3) Immune suppressive factors and immunesuppressive cells decrease immune responses
- Treg cells
- myeloid-derived suppressor cells, MDSC    

4) Inhibitory checkpoints like PD-1

Name the 3 types of passive immunotherapy

- adoptive T cell transfer
- anti-tumor antibodies
- suppression of the suppression

What are the effector mechanisms of tumor antibodies?

- Activating apoptosse pathways in tumor cells

1) Interference with grow signal functions (for example Her2-Neu) 

2) Complement activation (CDC)

3) Fcy-R-dependent lysis (ADCC, phagocytosis)

4) mAb-induced adaptive anti-tumor immune response

What does suppression of the suppression mean in passive immunization against tumor cells?

Immune checkpoint blockades.

- Ipilimumab blocks negative signaling from CTLA4

- PD-L1/PD-1 blockades, blocks the inhibition of CTLs

What is active immunotherapy?

Prophylactic tumor vaccines.
Induction of neutralizing antibodies against the structural proteins of the virus, for example the HPV- or HBV vaccine.

What is the B7 family?

The B7 family consists of structurally related, cell-surface protein ligands, which bind to receptors on lymphocytes that regulate immune responses. Activation of T and B lymphocytes is initiated by engagement of cell-surface, antigen-specific T-cell receptors or B-cell receptors, but additional signals delivered simultaneously by B7 ligands determine the ultimate immune response.

What kind of therapeutic cancer vaccines are there?

- Killed tumor vaccine
- Purified tumor antigens
- APC-based vaccines
- Cytokine- and costimulator- enhanced vaccines
- DNA vaccines
- Viral vectors

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