ICL 8.2: Cancer and Editing

Question 1

what is cancer?

Answer 1

cancer is a group of diseases characterized by uncontrolled growth and spread of abnormal cells

if the spread is not controlled, it can result in death

Question 2

what is metastasis?

Answer 2

migration of cancer cells from the original tumor site through the blood and lymph vessels to produce cancers in other tissues

metastasis is also the term used for a secondary cancer growing at a distant site

Question 3

where are immune cells located?

Answer 3

blood and lymph

Question 4

what are cancer cells?

Answer 4

cancer cells are normal “self” cells that have had a genetic mutation, most likely in something that regulates cell cycle checkpoints

so since they’re self cells, your immune often doesn’t see anything wrong with them

however, we can train our immune system to recognize them through cancer immunotherapy!

Question 5

how can we make the immune system see the cancer cells?

Answer 5

cancer immunotherapy

Question 6

what experiment was done to show that our immune response to tumors is immunologically specific?

Answer 6

1. mice were irradiated with dead tumor cells
2. then the mice were injected with the same liver tumor ells
3. overtime the mice never developed cancer!

however if they went back and gave live tumor cells from a different cell line, the mice got cancer!

this shows that the immune system is antigen specific

Question 7

what is immunoediting?

Answer 7

it’s dynamic process that consists of immunosurveillance and tumor progression

it describes the relation between the tumor cells and the immune system

Question 8

what are the three steps of immunoediting?

Answer 8

1. elimination
2. equilibrium
3. escape

Question 9

how do cancer cells turn into full fledged cancer?

Answer 9

normally, cancer formation is when there’s a group of cells that start dividing abnormally

with cancer editing, there are immune cells out checking for bad cells and they find cells that have been transformed and respond to them by killing them = elimination

in some cases, the cancer cells have mutations and can outsmart the immune system for a bit but ultimately you’re in equilibrium

then, sometimes the cancer cells get even more mutations and either the immune system doesn’t recognize them or the mutations go on for so long that your immune system gets tired = escape

the escape phase is when someone would be in the clinic and actually officially have cancer

all the other stuff is happening every single day in your body normally!

Question 10

how can leukocytes be bad and actually promote cancer?

Answer 10

usually infiltrating leukocytes are a good thing because it means your immune system is trying to stop the abnormal cells

but sometimes there are cancers that thrive on leukocyte infiltration –> the tumors can use the leukocytes as growth factors to grow even more

Question 11

what do PD-1 and PD-L1 do?

Answer 11

PD-L1 are “don’t kill me” signals expressed by host cells

PD-1 on T cells is inhibitory and tells T cell to move on and not kill the cell

Question 12

what does Treg do?

Answer 12

it suppressed CD8 and CD4 responses which stops your immune response

some tumors secrete cytokines to recruit Treg!!!

Question 13

how is anti-PD-1 medications used to treat cancer?

Answer 13

PD-1 on T cells is inhibitory and tells T cell to move on and not kill the cell

if you block PD-1 then the T cell won’t have anything turning it off and it’ll go out and kill tons of things

this is good because it means that the t cell can go kill cancer cells! it increases the immune-based killing of tumor cells

Question 14

what happens if you block CTLA4?

Answer 14

CTLA4 prevents T cells from being activated and destroying self cells

but if you block CTLA4 with anti-CTLA4 medications then the T cell can go out and kill tons of cancer cells

Question 15

what are the 4 types of cancer immunotherapy?

Answer 15

1. cytokine therapy
2. monoclonal antibody therapy
3. cancer vaccine
4. cell therapy

Question 16

what are cytokines?

Answer 16

proteins that activate the immune system

Question 17

how can you use cytokines to treat melanoma and renal cell carcinoma?

Answer 17

you can treat them with IFNα and IL-2

IFNα and IL-2 help with T cell proliferation

they also expand NK cell population which helps kill tumor cells

it’s really effective on tumors that lower MHC expression since this is what NK cells pick up on

the issue is that people have flu-like symptoms for 4 months and there’s only a 15% response rate

Question 18

what are monoclonal antibodies?

Answer 18

they are antibodies that recognize proteins expressed on tumors (tumor antigens)

Question 19

how do monoclonal antibodies work?

Answer 19

various mechanism:

1. opsonization for phagocytes
2. delivering radiation/chemical
3. blocking growth factor signaling (ex. TGF)

Question 20

what is anti-CD3 used for?

Answer 20

it’s a monoclonal antibody used for prevention of transplant rejection

anti-CD3 binds to CD3 which usually opsonizes antigens and marks them for the immune system

Question 21

what is Rituximab used to treat?

Answer 21

non-Hodgkin lymphoma

it’s anti-CD20

Question 22

what is Gemtuzumab ozogamicin used to treat?

Answer 22

aka mylotarg

used to treat AML

it’s a conjugated anti-CD33 antibody

Question 23

how does mylotarg work?

Answer 23

it’s anti-CD33 + calcicheamicin

calicheamicin can intercalate into DNA and disrupt the DNA

when that complex is exposed to cancer cells it binds to tumor cell and kills it

Question 24

what’s the problem with mylotarg?

Answer 24

people were dying of vein occlusion in the liver….

also calicheamicin is kinda toxic so maybe we shouldn’t be putting that into people’s bodies

Question 25

how does Rituximab work?

Answer 25

it a naked monoclonal antibody that is NOT conjugated (mylotarg is conjugated)

it binds to CD20 on normal and abnormal B cells

it blocks growth factor receptors or it can induce cytotoxicity/apoptosis

rituximab can also activate complement and kill B cells via MAC formation

Question 26

what is the problem with Rituximab?

Answer 26

it binds to CD30 on both normal and abnormal B cells

so it’s also going to opsonize your healthy B cells and kill them…

this is great if you have a B cell lymphoma but you should still give immunoglobulin to make up for the fact there’s no B cells around to produce antibodies

Question 27

what are the pros and cons of naked monoclonal antibody therapy?

Answer 27

they effectively kill all cells expressing the antigen which is great for getting kid of cancer cells and non-immune cancers

however, it also kills normal cells and can lead to some loss of normal tissue and local inflammation

Question 28

how do you engineer monoclonal antibodies to be specific for what you want?

Answer 28

1. if you alter the Fab region it will change the antigen specificity and make the antibody stay bound for longer
2. or you can alter the Fc region which will effect complement activation

Question 29

what is bi-specific antibody therapy?

Answer 29

when one antibody has two specificities

one end of the antibody binds to the cancer antigen (anti-HER2/neu) and the other end binds to the effector cell (CD8 T cell, NK cell, macrophage/monocyte)

or sometimes the second end will be engineered to bind to another cancer antigen

once both things are bound to the antibody, cancer cell killing occurs

Question 30

what’s the point to making a bi-specific antibody?

Answer 30

you want to hook up the cancer cell with effector cell to induce ADCC

then you can use another bi-specific antibody to hook another tumor cell to the tumor cell that’s bound to the effector cell to make a chain

cross-linking the two cancer antigens induces apoptosis!

basically you’re trying to bring an NK cell in close proximity to tumor cells to improve killing

Question 31

if you wanted to kill a T cell lymphoma, what would you target?

Answer 31

CD4 or CD8

if you targeted CD3 you’d kill all T cells including the healthy ones

so if you target CD4 for example, then you would only be partially immunosuppressed but still be killing off some of the cancer

Question 32

what is anti-idiotype therapy?

Answer 32

you’re using the immune system to fight the immune system!

you generate antibodies against antibodies!

use the antigen-binding domain of cancerous B cells as an antigen and produce monoclonal antibodies that will activate ADCC against cancerous B cells

if you could get something to bind to the antigen-binding site of the antibody and recognize it as foreign, you could get rid of B cell lymphomas

once the anti-idiotype monoclonal antibody binds to the cancerous B cell antibodies, it will illicit a response from effector cells and phagocytes that will kill the B cell

antigen binding domain of antibodies = idiotype

Question 33

what does ADCC stand for?

Answer 33

antibody-dependent cellular cytotoxicity

Question 34

why doesn’t anti-idiotype therapy work for MM?

Answer 34

in MM the B cells are secreting antibodies, they don’t have antibodies on their surface

however, in B cell lymphoma, there are antibodies on the surface of the B cells that can be targeted by anti-idiotype therapy!

Question 35

what are prophylactic vaccines?

Answer 35

they prevent development of cancer

you must know causative agent of cancer in order to vaccinate!

currently only 2 approved by FDA

Question 36

what are therapeutic vaccines?

Answer 36

they treat existing cancer

must know cancer specific antigen!

0 currently approved by FDA

Question 37

what cancer does HepB cause?

Answer 37

liver cancer

Question 38

what cancer does HPV cause?

Answer 38

cervical cancer

Question 39

which vaccine is against HPV?

Answer 39

Gardasil

Question 40

how do you design a therapeutic vaccine?

Answer 40

1. common target vaccine: this would be a vaccine where everybody with this certain cancer would have this same antigen
2. patient specific vaccine: this would be a vaccine that’s made from taking the specific patient’s tumor cells and developing a vaccine for it

Question 41

how do you make a patient specific therapeutic vaccine?

Answer 41

1. remove patients own tumor cells
Isolate proteins (antigens)

2. couple to a carrier to help make the protein more antigenic
3. inject back into patient

Question 42

what is Provenge?

Answer 42

cancer therapy

1. take APC outside the body and inject either tumor RNA into them or tumor antigen
2. let the APC mature and produce tumor antigens
3. inject the APC back into the patient
4. the APC will then present this antigen to T cells and activate T cells to illicit an immune response

this is how you train your APC to attack cancer cells!

Question 43

how can we engineer CD8 T cells to fight cancer?

Answer 43

we know alot of cancer antigens so we can clone TCR that react with these cancer antigens!

there is a subset of patients that just spontaneously cure themselves of cancer and when we looked at their T cells and cloned their TCR we found that they were antigen specific towards an antigen that was on their tumor!

so if we can figure out a way to clone a TCR and put it onto someone’s T cell we would be engineering CD8 T cells to recognize specific antigens based on their TCR!

so you’re cloning the TCR that reacts with the specific cancer antigen that that patient has – then you take CD8 T cells from that patient and engineer them to express the TCR that would respond to the antigen associated with their tumor – then you inject their CD8 T cells back into them

so freaking cool

Question 44

what is CAR T-cell therapy?

Answer 44

CAR = chimeric antigen receptor

CAR T-cell therapy is genetically modified t cells

you take the patient’s T cells out of their body and engineer them to recognize CD19 lymphoma

this actually works really well for treating ALL!

Question 45

what are the common cancer antigens that we know of?

Answer 45

1. PSA = prostate cancer
2. MART-1 = melanoma
3. tyrosinase = melanoma
4. CEA = lung, colorectal, breast, pancreatic
5. mucin (up-regulated in many cancers)

Question 46

what is mucin?

Answer 46

makes membranes more sticky

it’s upregulated in many cancers

Question 47

how is mucin involved in cancer?

Answer 47

normal mucin has a protein core that is blocked and you can’t get to it due to sugars attached to it

but in cancer, the sugars are smaller and the protein backbone gets exposed

so they’re trying to develop a treatment against carbohydrates but this is really hard because literally everything we have done involves proteins