11/18 Cancer Immunotherapies + 11/20 Extra Tolerance & Transplantation

Definition of malignant

cells capable of indefinite growth and metastasis - invasion of distant tissue

Definition of metastasis (1 sentence 1 bullet)

the spread of cancer from original place of formation to another part of the body

• occurs when cancerous cells can enter blood vessels and find distant sites & tissue

What causes cancer (3, 2 with subbullets)

• chemical substances

• physical agents

  • ionizing radiation

  • x rays

• some infectious agents

  • HPV, HBV, HCV, EBV

What is a proto-oncogene

genes that promote cell growth and division

What happens when proto-oncogenes are mutated? (1 sentence 1 bullet)

Becomes an oncogene = causes excessive growth via gain of function

• ex: KRAS, HER2

What happens when a tumor suppressor gene is mutated? (1 sentence 1 bullet with 2-3 examples)

Causes excessive replication and division via a loss of function

• ex: p53, BRCA1/BRCA2

What happens when a DNA Repair gene is mutated?

Allows accumulation of mutations via a loss of function

How many mutations need to occur to have cancer progress?

3

Define cancer immunoediting

our immune system is working every day to remove pre-cancerous cells. the process of trying to get rid of a tumor involves selecting for the toughest, most durable, immune-evasive tumor cells out there

What are the three proposed phases of immunoediting?

1. elimination = attacking the cells that can be targeted

2. equilibrium = state of balance between destructive & survival of best cells

3. escape = most aggressive and least immunogenic cells thrive and spread

How can chronic inflammation cause cancer?

Increase in cellular stress like ROS can lead to genotoxic stress that causes reactive oxygen & nitrogen species to release → increased mutation rate in cells

How can growth factors and cytokines increase cancer?

If they’re in the wrong environment they can induce cell proliferation → chronic cell proliferation

How do pro-angiogenic responses cause cancer?

Increased blood vessel growth allows for greater tumor cell invasion by providing nutrients

What is the function of NK cells in tumor eradication?

target cells with altered, deleted, or ab-labeled MHC I

What is NK cells’ mechanism of action in tumor eradication? (3 bullets)

• perforin/granzyme killing

• fas/fasL killing

• upregulation of stress ligands by target cell

What is the function of macrophages in tumor eradication?

Bind to ab-coated tumor cells

What is the mechanism of action of macrophages in tumor eradication?

Secrete TNF-a which is shown to have strong anti-tumor activity

Name the tumor infiltrating lymphocytes (3)

T cells, NK, NKT cells

How can b cells lead to a downfall in tumor eradication? (2)

• ab can bind and block the tumor Ag that the CTL would recognize

• Ab can form complexes that block Fc receptors on NK and macrophages limiting their antitumor abilities

What are tumor-associated antigens (TAAs)/neoantigens?

tumors can express unique or inappropriately expressed Ags that may be detected by the immune system

What are the 4 neoantigen groups that T cells can recognize?

• viral Ag encoded genes exclusively expressed by tumors

• ag encoded by variant forms of normal genes altered by mutations

• ag normally expressed only at certain stages of development

• ag overexpressed in particular tumors

What are two oncofetal tumor antigens?

Alpha-fetoprotein and carcinoembryonic antigen

How can cancer cells evade cytotoxic T cells? Name 2 ways

Downregulation of MHC Class I expression and mutations/downregulations of second signal molecules

Name the costimulatory marker molecules (2/3)

CD80/86 on APCs

CD28 on T cells

What are the two ways cancer cells can evade NK cells?

• downregulate NK activating receptor ligands

• expression of mutated or absent Fas/FasL

What are three general ways cancer calls can evade both cytotoxic T cells and NK cells?

1. upregulation of anti-apoptotic mediators

2. expression of mutated or absent death receptors

3. increased expression of co-inhibitory receptors

Name two categories for cancer immunotherapies (that aren’t therapies)

1. monoclonal antibodies = antibodies that target a specific antigen, varied functions

2. neoantigen vaccines = stimulate immune response against personalized tumor associated antigens

Name the other two categories for cancer immunotherapies (that are therapies)

Adoptive cell therapy = isolate, expand, and stimulate immune cells ex vivo then transfer back to patient

CAR-T cell therapy = engineer immune cells to recognize specific tumor associated antigens

List the 4 steps of creating monoclonal antibodies

1. immunize mice with specific Ag to stimulate ab producing plasma cells

2. fuse plasma cells with human myeloma cells = hybridoma

3. select and expand for mAb-secreting hybridomas

4. isolate mAbs from hybridomas

Name the three activating immune mediated killing types

• complement dependent cytotoxicity

• antibody-dependent cell cytotoxicity

• antibody-dependent phagocytosis (opsonization)

Define/explain rituximab (1 sentence 1 bullet)

an anti-CD20 B cell lymphoma mAb that can do all three immune mediated killing types

• increases long term survival for B cell lymphoma patients

Explain herceptin’s clinical application

binds to the HER2 receptor, preventing signaling that may enable breast cancer cell growth

Explain the problem and solution when blocking inhibitory immune receptors

• ab can target other non-cancerous cells that also express the target Ag, leading to adverse effects

• use a pro-body to mask antigen binding site until it reaches tumor site, where specific proteases can degrade it

What does nivolumab bind to?

Binds to PD-1

What does ipilimumab bind to?

Binds to CTLA-4

What are the 3 steps to making a neoantigen vaccine?

1. sequence and compare tumor and somatic cell DNA to find mismatches

2. predicted algorithms determine where these mutations are in proteins and if they’re expressed on MHC/HLA

3. this ag can be delivered back into the patient via vaccination to help boost the immune response against the tumor

What is the goal of adoptive cell therapy?

select for the strongest anti-tumor lymphocytes

What is the 4 step process to adoptive cell therapy?

1. excise tumor from patient

2. culture tumor ex vivo with cytokines that promote growth of lymphocytes

3. use assay to select lymphocytes with strongest tumor killing capacity

4. expand and reinfuse strongest lymphocytes into patient

Define chimeric antigen receptor (CAR)

Genetically engineered receptors that involve fusion of tumor targeting antibody with T cell signaling domains

What are the three components of CAR-T cell therapy?

Targeting the antibody, CD3-zeta, and costimulatory domains

What is targeting antibody?

single-chain variable fragment that gives receptor antigen specificity

What is CD3-zeta?

Contains ITAM (immune tyrosine activating motif) for internal signaling

What are the costimulatory domains

CD28, OX40, CD137 = all promote CAR activation

What is the 4 step process for CAR-T cell therapy?

1. t cells collected from patient blood

2. genetically engineered recombinant protein is inserted into the t cell

3. tumor specific t cell is expanded

4. t cells are placed back into the patient

What can car-t cell therapy result in and what’s the solution?

Can result in cytokine storm

• solution: kill switch/suicide gene, CAR-NK Cells

What does histocompatibility determine?

Determines rejection → “histocompatible” grafts share sufficient antigen similarity, decreasing change of rejection

What is the goal of transplantation? (2)

• minimize graft rejection

• prevent suppressing entire immune response

Who is the donor in an autograft?

Self

Who is the donor in an isograft?

Genetically identical individual (eg identical twin)

Who is the donor in allograft?

Genetically different member of same species (eg parent)

Who is the donor in a xenograft?

Different species

What are the 3 indicators of transplant success?

Blood group antigens matching (AB, Rh), MHC/HLA compatibility, and cross-matching

What is the parent-to-child graft and sibling % compatibility

• parent always have 50% compatibility

• siblings have 25% chance of MHC compatibility

What is cross-matching and an example of it? (1 sentence 1 bullet)

Blood test that determines compatibility by analyzing circulating antibodies, especially against HLA

• ex: luminex bead-based screening assays

What do anti-rejection drugs do?

allow organ transplants between completely mismatched people

Why do certain organs have a higher success rate for transplantations? (3 reasons)

Certain organs could be an immune privileged site, being more resilient and easier to remove, or it being combined with another organ transplant

What is first-set rejection in allograft rejections for animals?

Complete by 12-14 days and memory cells are generated against graft

What is second set rejection in allograft rejections for animals?

Occurs much faster due to memory from previous graft

How do t cells mediate allograft rejections in animals? (2)

• CD4+ t cells seem to be more important than CD8+ but both play a significant role

• shown through adoptive transfer and t cell neutralizing experiments

What is the timing and mechanism for hyperacute transplant rejections in humans?

Timing: 24-48 hours

Pre-existing antibodies bind to graft cells and activate complement and ADCC and cause inflammation

What is the timing and mechanism for acute transplant rejections in humans?

Timing: 7-10 days

Mediated by t cells in a sensitization stage and effector stage

Describe the sensitization stage (3 steps) for acute transplant rejections in humans

1. presentation of Ag to T cells

2. T cells recognize donor MHC (direct presentation) or donor peptides in self MHC (indirect presentation)

3. T effector and memory cell generation

Describe the effector stage for acute transplant rejections in humans (3 bullets)

• t and NK cell killing

• antibody production

• inflammatory cytokine and chemical production

What is the timing and mechanism for chronic transplant rejections in humans?

Timing: months to years

Humoral and cell-mediated responses, anti-rejection drugs help but aren’t perfect

What is graft vs host disease?

immune cells from donated organ expand and attack recipient

What is the function of irradiation of lymphoid regions? (2 bullets)

• wipes out host’s immune cells and donor cells engraft and form a “new” immune system

• used in bone marrow transplants, GvHD, and cancer treatment

What is the function of corticosteroids (prednisone, dexamethasone)? (2 bullets)

• quiet immune system

• given right before and after transplantation

What is the function of calcineurin inhibitors (tacrolimus and cyclosporine)

• block calcium-dependent phosphatases that can activate t cells

What are 3 examples of anti-proliferative (anti-miotic) agents?

• mycophenolate mofetil

• azathioprine

• sirolimus

What is the function of anti-thymocyte globulin (ATG) (2 bullets)

• ab that bind and neutralize T cells

• isolated from animals exposed to human serum

What is the function of belatacept?

• soluble CTLA-4 protein that can block co-stimulation and induce T cell anergy

• used in kidney transplantations